HK1188279B

HK1188279B - System and method for efficient air dehumidification and liquid recovery with evaporative cooling

Info

Publication number: HK1188279B
Application number: HK14101422.0A
Authority: HK
Inventors: D．E．克拉里奇; C．H．卡尔普; J．S．哈伯尔
Original assignee: 得克萨斯州A&M大学系统
Priority date: 2010-11-12
Filing date: 2011-11-11
Publication date: 2017-08-04

Description

System and method for air dehumidification and liquid recovery with evaporative cooling

Background

Heating Ventilation and Air Conditioning (HVAC) systems often have a dehumidification system integrated into the cooling apparatus for dehumidifying air conditioned by such a system. When cooling is required in warm and hot environments, the air that is cooled and dehumidified will typically have over about 0.009 (H per pound of dry air)₂O pounds) humidity ratio. In these environments, HVAC systems traditionally use refrigeration compressors to sensible cooling (sendiblelogging) and remove latent energy (i.e., humidity) from the air. The air is typically cooled to about 55F, which will be H₂O condenses out of the air until the air is about 100% saturated (i.e., reaches about 100% relative humidity). The 55F temperature reduced the humidity ratio to about 0.009 pounds of H per pound of dry air₂O, which is the water vapor saturation point at 55 ° F, resulting in almost 100% relative humidity. When the air is warmed to about 75 ° F, the humidity ratio remains nearly the same, while the relative humidity decreases to about 50%. This conventional dehumidification method requires cooling the air to about 55 ° F, and can typically achieve a coefficient of performance (COP) of about 3 to 5.

Disclosure of Invention

Certain embodiments commensurate in scope with the present invention are summarized below. These examples are not intended to limit the scope of the claimed invention, but rather are intended to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

In a first embodiment, there is provided a dehumidification system for removing water vapor from an air stream, the dehumidification system comprising: a first channel and a second channel separated by a membrane. The membrane is configured to helpH from water vapour₂O passes through the permeable volume of the membrane to the second channel and substantially blocks passage of all other components of the air stream through the membrane, effecting a removal of water vapor from the air stream flowing through the first channel. The system also includes an evaporative cooling unit configured to cool the air stream. The system also includes a pressure increasing device configured to generate a lower partial pressure of water vapor in the second passage than in the first passage to cause H₂O moves through the membrane to the second channel. The pressure increasing means is further configured for increasing the water vapor pressure at the outlet of the pressure increasing means to a partial water vapor pressure in a range suitable for subsequent condensation to liquid water.

In a second embodiment, a system includes a system for removing H from an air stream₂And a dehumidification unit of O steam. The dehumidifying unit includes: an air passage configured to receive an inlet airflow and a discharge outlet airflow. The dehumidification unit further comprises a permeable H adjacent to the air channel₂And (3) O material. The light transmission H₂The O material is configured to selectively allow H from the inlet airflow₂H of O vapor₂O passes through the through H₂O material to said H₂O suction side of the material and substantially blocks passage of other components of the inlet air stream through the H-permeable membrane₂O material to said H₂O suction side of material. The system also includes an evaporative cooling unit configured to cool the air stream. The system further includes a pressure increasing device configured for increasing the pressure in the H-penetration₂Producing H in the inlet air flow on the suction side of the O material₂H with lower partial pressure of O vapor₂Partial pressure of O vapor, driving H from the inlet air stream₂H of O vapor₂O passes through the through H₂O material, and increasing the pressure at the outlet of the pressure increasing device to be suitable for H₂Condensing O vapor into liquid H₂H of O₂Partial pressure of O vapor.

In a third embodiment, a method comprises: receiving includes H₂The air flow including O steam flows into an air passage of the dehumidification unit, wherein the air flow has H₂O steam first partial pressure. The method also includes cooling the air stream via an evaporative cooling unit. The method further includes utilizing a pass-through H across the dehumidification unit₂Pressure difference of O material will be H₂O passes through the hydrogen permeable membrane₂H of O material sucked to the dehumidification unit₂O in the vapor channel. Said H₂O vapor channel has H below air flow₂H of first partial pressure of O steam₂O steam second partial pressure. Further, the method includes converting the signal from the H₂H of O vapor channel₂Receiving O vapor into a pressure increasing device, and feeding H from the pressure increasing device₂Increasing the pressure of O vapor above the H₂H of second partial pressure of O steam₂O vapor third partial pressure.

Drawings

These and other features, aspects, and advantages of the disclosed embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic diagram of an HVAC system having a dehumidification unit and one or more evaporative cooling units in accordance with an embodiment of the present disclosure;

FIG. 2A is a perspective view of the dehumidification unit of FIG. 1 having a plurality of parallel air channels and water vapor channels in accordance with an embodiment of the present invention;

FIG. 2B is a perspective view of the dehumidification unit of FIG. 1 with a single air channel located within a single water vapor channel in accordance with an embodiment of the present invention;

FIG. 3 is a plan view of an air channel and an adjacent water vapor channel of the dehumidification unit of FIGS. 1, 2A, and 2B, in accordance with an embodiment of the present invention;

FIG. 4 is a perspective view of a separation module utilizing membrane formation that may be used as a water vapor channel of the dehumidification unit of FIGS. 1-3 in accordance with an embodiment of the present invention;

FIG. 5 is a temperature-humidity diagram of the temperature and humidity ratio of humid air flowing through the dehumidification unit of FIGS. 1-3, according to an embodiment of the present invention;

FIG. 6 is a schematic view of the HVAC system and dehumidification unit of FIG. 1 and one or more evaporative cooling units having a vacuum pump for removing non-condensing components from water vapor in a water vapor extraction chamber of the dehumidification unit, in accordance with an embodiment of the present invention;

FIG. 7 is a schematic view of the HVAC system and dehumidification unit and one or more evaporative cooling units of FIG. 6 having a control system for controlling various operating conditions of the HVAC system and the dehumidification unit in accordance with an embodiment of the present disclosure;

FIG. 8 is a schematic diagram of an HVAC system having an evaporative cooling unit disposed upstream of a dehumidification unit in accordance with an embodiment of the present disclosure;

FIG. 9A is a psychrometric chart of the temperature and humidity ratio of air flowing through the direct evaporative cooling unit and the dehumidification unit of FIG. 8, in accordance with an embodiment of the present invention;

FIG. 9B is a psychrometric chart of the temperature and humidity ratio of the air flowing through the indirect evaporative cooling unit and the dehumidification unit of FIG. 8, in accordance with an embodiment of the present invention;

FIG. 10 is a schematic view of an HVAC system having an evaporative cooling unit disposed downstream of a dehumidification unit in accordance with an embodiment of the present disclosure;

FIG. 11A is a psychrometric chart of the temperature and humidity ratio of air flowing through the dehumidification unit and the direct evaporative cooling unit of FIG. 10, in accordance with an embodiment of the present invention;

FIG. 11B is a psychrometric chart of the temperature and humidity ratio of air flowing through the dehumidification unit and the indirect evaporative cooling unit of FIG. 10, in accordance with an embodiment of the present invention;

FIG. 12A is a psychrometric chart of the temperature and humidity ratio of air flowing through a plurality of dehumidification units and a plurality of direct evaporative cooling units, in accordance with an embodiment of the present invention; and

fig. 12B is a psychrometric chart of the temperature and humidity ratio of air flowing through a plurality of dehumidification units and a plurality of indirect evaporative cooling units, in accordance with an embodiment of the present invention.

Detailed Description

Specific embodiments of the present invention will be described herein. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present invention, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

The subject matter disclosed herein relates to dehumidification systems, and more particularly, to systems and methods capable of dehumidifying air without initial condensation by establishing a humidity gradient in a dehumidification unit. In one embodiment, water vapor permeable material (i.e., water vapor permeable membrane) is used along at least one boundary separating the air channel from the secondary channel or chamber to assist in removing water vapor from air passing through the air channel. The secondary channel or chamber separated from the air channel by the water vapor permeable material may receive water vapor extracted from the air channel via the water vapor permeable material.

In certain embodiments, the dehumidification unit may be used in conjunction with one or more evaporative cooling units. For example, in certain embodiments, the evaporative cooling unit may be disposed upstream of the dehumidification unit, and air expelled from the evaporative cooling unit is directed into the inlet of the dehumidification unit. Conversely, in other embodiments, the dehumidification unit may be disposed upstream of the evaporative cooling unit, with air expelled from the dehumidification unit being directed into an inlet of the evaporative cooling unit. Indeed, in other embodiments, multiple dehumidification units may be used with multiple evaporative cooling units disposed between the dehumidification units. The use of multiple dehumidification units and multiple evaporative cooling units enables a "zig-zag" progression from initial conditions of temperature and humidity ratio of the inlet air to desired final conditions of temperature and humidity ratio of the outlet air to be achieved on a psychrometric chart. In other words, each dehumidification unit dehumidifies the air successively at a substantially constant temperature, while each evaporative cooling unit successively cools (and humidifies) the air in the case of direct evaporative cooling, until the desired final conditions of temperature and humidity ratio are achieved.

In operation, the water vapor permeable material allows for H₂O（H₂O may be referred to as H for water molecules, gaseous water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, or combinations thereof₂O) from the air channel to the secondary channel or chamber through the water vapor permeable material while substantially blocking the flow of other components of the air flowing through the air channel from passing through the water vapor permeable material. In this way, the water vapor permeable material reduces the humidity of the air flowing through the air channels by only primarily removing water vapor from the air. Correspondingly, the secondary channel or chamber is mainly filled with water vapour. It should be noted that H can be assisted by a pressure differential₂O passes through the water vapor permeable material. In practice, it may be in the secondary channel or chamberTo generate a lower partial pressure of water vapor (i.e., this partial pressure is less than the partial pressure of water vapor in the air passageway) to further assist H₂O passes through the water vapor permeable material. Thus, the side of the water vapor permeable material opposite the air channel may be referred to as the suction side of the water vapor permeable material.

Once H is₂O has passed through the water vapor permeable material, a vacuum pump is used to increase the partial pressure of water vapor on the suction side of the water vapor permeable material to the minimum saturation pressure required to enable the water vapor to be condensed by the condenser. That is, depending on the desired conditions for condensation, the vacuum pump compresses the water vapor to a pressure in a range suitable for condensing the water vapor into liquid water (e.g., a range of about 0.25 pounds per square inch absolute (psia) to 1.1 pounds per square inch absolute, the higher values of which apply to embodiments using multiple dehumidification units in series). The condenser then condenses the water vapor to a liquid state, and the resulting liquid water is then pressurized to about atmospheric pressure so that the liquid water can be removed at ambient atmospheric conditions. By condensing the water vapor to a liquid state prior to expelling the water vapor, certain efficiencies are provided. For example, the energy required to pressurize liquid water to atmospheric pressure is significantly less than the energy required to pressurize water vapor to atmospheric pressure. It should also be noted that the dehumidification units described herein generally use significantly less energy than conventional systems.

Although the embodiments described herein are primarily presented as being capable of removing water vapor from air, other embodiments may also accomplish the removal of other H from air₂And (4) an O component. For example, in some embodiments, it may be possible to use Per-H₂O material replaces the water vapor permeable material. Thus, let through H₂The O material may allow for multiple H₂One, all, or any combination of O components (i.e., water molecules, gaseous water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, etc.) pass from the air channel through the H-permeable membrane₂O-material flows to the secondary channel or chamber while substantially blocking the passage of other components of the air flowing through the air channel through the vent H₂And (3) O material. In other words, it is possible to provide a high-quality imageThe disclosed embodiments are not limited to removing water vapor from air, but may also remove H from air₂O (i.e., in H)₂In any state of O). However, for the sake of simplicity, the embodiments described herein focus primarily on the removal of water vapor from air.

FIG. 1 is a schematic diagram of an HVAC system 8 having a dehumidification unit 10 and one or more evaporative cooling units 12 according to an embodiment of the present disclosure. In certain embodiments, as shown, the dehumidification unit 10 may receive relatively high humidity inlet air 14A from a first evaporative cooling unit 12 located on an inlet side of the dehumidification unit 10. Further, in certain embodiments, the dehumidification unit 10 may expel outlet air 14B of relatively low humidity into the second evaporative cooling unit 12 disposed on the outlet side of the dehumidification unit 10. Aspects of the evaporative cooling unit 12 and its positioning in the HVAC system 8 will be described in greater detail herein. Specifically, while FIG. 1 shows the evaporative cooling units 12 located on the inlet and outlet sides of the dehumidification unit 10, in other embodiments, the HVAC system 8 may include only the evaporative cooling units 12 upstream of the dehumidification unit 10, or only the evaporative cooling units 12 downstream of the dehumidification unit 10. Furthermore, in more complex arrangements, multiple dehumidification units 10 may be used with multiple evaporative cooling units 12.

The dehumidification unit 10 may include one or more air channels 16 through which the air 14 (i.e., the inlet air 14A and the outlet air 14B) flows. In addition, the dehumidification unit 10 may include one or more water vapor channels 18 adjacent to the one or more air channels 16. As shown in fig. 1, the air 14 does not flow through the water vapor passage 18. However, the embodiments described herein enable passage of water vapor from the air 14 in the air channel 16 to the water vapor channel 18, thus dehumidifying the air 14 and accumulating water vapor in the water vapor channel 18. Specifically, water vapor from the air 14 in the air channels 16 may be allowed to flow through the interface 20 (i.e., barrier or membrane) between the adjacent air channels 16 and water vapor channels 18, while other components of the air 14 (e.g., nitrogen, oxygen, carbon dioxide, etc.)) Is blocked from flowing across the interface 20. In general, the water vapor passage 18 is sealed to create a low pressure, drawing water vapor from the air 14 in the air passage 16 as H₂O passes through the interface 20 (i.e., passes through the interface 20 as water molecules, gaseous water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, etc.).

In this way, a humidity gradient is established between the air channels 16 and the adjacent water vapor channels 18. A humidity gradient is created by the pressure gradient between the air channels 16 and the adjacent water vapor channels 18. Specifically, the partial pressure of water vapor in the water vapor channels 18 is maintained at a level lower than the partial pressure of water vapor in the air channels 16 so that water vapor in the air 14 flowing through the air channels 16 tends to flow to the suction side of the interface 20 (i.e., the water vapor channels 18 have a lower partial pressure of water vapor).

According to the present embodiment, H can be substantially blocked off₂Air components other than O pass through the interface 20. In other words, in some embodiments, H may be blocked off₂About 95% or more, about 96% or more, about 97% or more, about 98% or more, or about 99% or more of the components of the air 14 other than O (e.g., nitrogen, oxygen, carbon dioxide, etc.) pass through the interface 20. When and blocks H₂Ideal interface 20 for 100% air 14 composition other than O, when compared, blocks H₂An interface 20 of 99.5% composition other than O will experience an efficiency reduction of about 2% to 4%. Thus, except for H₂The components other than O are periodically purged to minimize these negative effects on efficiency.

Fig. 2A is a perspective view of the dehumidification unit 10 of fig. 1 having a plurality of parallel air channels 16 and water vapor channels 18, in accordance with an embodiment of the present invention. In the embodiment shown in fig. 2A, the air channels 16 and the water vapor channels 18 are generally straight channels that provide a large amount of interface 20 surface area between adjacent air channels 16 and water vapor channels 18. In addition, the generally straight channels 16, 18 enable the water vapor 26A to be removed along the path of the air channel 16 before the air 14 exits the air channel 16. In other words, the relatively humid inlet air 14A (e.g., air having a dew point of 55 ° f or higher suitable for air conditioning) passes straight through the air passage 16 and exits as relatively dry outlet air 14B because moisture has been removed as the air 14 traverses along the atmospheric pressure side of the interface 20 (i.e., the side of the interface 20 in the air passage 16). In embodiments where a single unit dehumidifies to a 60 ° f saturation pressure or less, the partial pressure of water vapor on the suction side of interface 20 (i.e., the side of interface 20 in water vapor passage 18) will be substantially maintained below the partial pressure of water vapor on the atmospheric pressure side of interface 20.

As shown in fig. 2A, each water vapor channel 18 is connected to a water vapor channel outlet 22, and water vapor in the water vapor channel 18 is removed through the water vapor channel outlet 22. As shown in fig. 2A, in certain embodiments, the water vapor channel outlets 22 may be connected via a water vapor outlet manifold 24, wherein water vapor 26A from all of the water vapor channels 18 is combined in a single water vapor vacuum volume 28 (e.g., tube or chamber). Other configurations of the air channels 16 and the water vapor channels 18 may also be implemented. As another example, fig. 2B is a perspective view of the dehumidification unit 10 of fig. 1 having a single air channel 16 positioned within a single water vapor channel 18, in accordance with an embodiment of the present invention. As shown, the air passage 16 may be a cylindrical air passage that is positioned within a larger concentric cylindrical water vapor passage 18. The embodiments shown in fig. 2A and 2B are merely exemplary and are not intended to be limiting.

Fig. 3 is a plan view of the air channel 16 and the adjacent water vapor channel 18 of the dehumidification unit 10 of fig. 1, 2A, and 2B, in accordance with an embodiment of the present invention. In fig. 3, the depiction of water vapor 26 is exaggerated for illustrative purposes. Specifically, water vapor 26 from the air 14 is shown as H₂O flows through the interface 20 between the air channel 16 and the adjacent water vapor channel 18 (i.e., as water molecules, gaseous water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, etc. pass through the interface 20). Conversely, other components 30 of the air 14 (e.g.Nitrogen, oxygen, carbon dioxide, etc.) are shown to be blocked from flowing through the interface 20 between the air channel 16 and the adjacent water vapor channel 18.

In certain embodiments, the interface 20 may comprise a membrane that is permeable to water vapor and allows for H₂O flows through the permeable volume of the membrane while blocking the flow of the other components 30. Again, it should be noted that when H is₂When O passes through the interface 20, H₂O will actually pass through the interface 20 as one, all, or any combination of states of water (e.g., as water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, etc.). For example, in one embodiment, the interface 20 may adsorb/desorb water molecules. In another example, the interface 20 may adsorb/desorb water molecules and allow water vapor to pass through. In other embodiments, the interface 20 may assist in the passage of water in other combinations of states. The interface 20 extends along the flow path of the air 14. Thus, as the relatively humid inlet air 14A flows through the air channels 16, the water vapor 26 is continuously removed from one side of the interface 20. Thus, as the air 14 progresses along the flow path of the air channel 16 and continuously contacts the interface 20 adjacent the air channel 16 from the inlet air 14A location to the outlet air 14B location, dehumidification of the air 14 flowing through the air channel 16 is achieved by incrementally separating the water vapor 26 from the other components 30 of the air 14.

In certain embodiments, the water vapor channels 18 are evacuated prior to use of the dehumidification unit 10 to create a lower partial pressure of the water vapor 26 in the water vapor channels 18 (i.e., the partial pressure is less than the partial pressure of the water vapor in the air channels 16). For example, during normal operation, the partial pressure of the water vapor 26 in the water vapor channels 18 may be in the range of about 0.10psia to 0.25psia, which corresponds to dehumidification to a 60 ° f saturation pressure or lower. In this example, initial conditions in the range of 0.01psia may be used to remove noncondensables, while the partial pressure of water vapor in the air channels 16 may be in the range of about 0.2psia to 1.0 psia. However, at some times, the pressure differential between the partial pressure of water vapor in the water vapor channels 18 and the partial pressure of water vapor in the air channels 16 may be as low as (or lower than) 0.01 psia. The lower partial pressure of water vapor in the water vapor channels 18 further assists the flow of water vapor 26 from the air channels 16 to the water vapor channels 18 because the air 14 flowing through the air channels 16 is at local atmospheric pressure (i.e., about 14.7psia at sea level). Since the partial pressure of water vapor in the air 14 in the air passage 16 is greater than the partial pressure of water vapor 26 in the water vapor passage 18, a pressure gradient is created from the air passage 16 to the water vapor passage 18. As described above, the interface 20 between adjacent air channels 16 and water vapor channels 18 provides a barrier and allows substantially only water vapor 26 to flow from the air 14 in the air channels 16 into the water vapor channels 18. Thus, the air 14 flowing through the air passages 16 will generally reduce humidity from the inlet air 14A to the outlet air 14B.

The use of water vapor permeable membranes as the interface 20 between the air channels 16 and the water vapor channels 18 has a number of advantages. Specifically, in certain embodiments, no additional energy is required to create the humidity gradient from the air channels 16 to the water vapor channels 18. Additionally, in certain embodiments, no regeneration operation is involved, and no environmental emissions (e.g., solids, liquids, or gases) are generated. Indeed, according to one embodiment, the water vapor 26 may be separated from the other components 30 of the air 14 via a water permeable membrane (i.e., the interface 20) at an energy efficiency much greater than compressor techniques used to condense water directly from an air stream.

Because the water vapor permeable membrane is highly permeable to water vapor and because the air 14 flowing through the air channels 16 does not have to be significantly pressurized to assist with H₂O passes through the interface 20 so the cost of operating the dehumidification unit 10 can be minimized. Water vapor permeable membranes are also highly selective for the permeation of water vapor from the air 14. In other words, the water vapor permeable membrane is very effective in preventing components 30 of the air 14 other than water vapor from entering the water vapor channels 18. This is advantageous because H₂O passes due to a pressure gradient (i.e., due to a lower partial pressure of water vapor in the water vapor channels 18)Past the interface 20 and any air 14 that permeates or leaks into the water vapor channels 18 will increase the power consumption of the vacuum pump used to evacuate the water vapor channels 18. In addition, the water vapor permeable membrane is strong enough to resist air contamination, biodegradation, and mechanical corrosion of the air channels 16 and water vapor channels 18. According to one embodiment, the water vapor permeable membrane may also resist bacterial attachment and growth in hot, humid air environments.

One example of a material for the water vapor permeable membrane (i.e., interface 20) is zeolite supported on a porous metal sheet. Specifically, in certain embodiments, ultra-thin (e.g., less than about 2 μm) dense zeolite thin film sheets may be deposited on porous metal sheets that are about 50 μm thick. The resulting membrane sheets may be packaged into membrane separation modules to be used in the dehumidification unit 10. Fig. 4 is a perspective view of a separation module 32 formed using membranes, which may be used as the water vapor channel 18 of the dehumidification unit 10 of fig. 1-3 in accordance with an embodiment of the present invention. The two membranes 34, 36 may be folded and attached together in a generally rectangular shape with a width w_msmA water vapor passage of about 5 mm. The separation module 32 may be positioned within the dehumidification unit 10 to expose the coated membrane surface to the air 14. The thin metal support sheet reduces the weight and cost of the metal starting material and also allows for diffusion of H through the water vapor permeable film deposited on the membranes 34, 36₂The resistance of O is minimized. The metallic nature of the metal sheets 34, 36 provides mechanical strength and flexibility for packaging so that the separation module 32 can withstand pressure gradients greater than about 60psi (i.e., about 4 times atmospheric pressure).

Separation of water vapor from the other components 30 of the air 14 may result in a water vapor permeation flux of about 1.0kg/m²H (e.g., at about 0.5 kg/m)²H to 2.0kg/m²In the range of/h) and may produce a water vapor to air selectivity in the range of about 5 to 200 +. As such, the efficiency of the dehumidification unit 12 is relatively high compared to other conventional dehumidification techniques that have relatively low production costs. As an example, a 1 ton air cooling load dehumidifies under ambient conditionsAbout 7m is required²To 10m²The membrane area of the interface 20 of (1). To handle this air cooling load, in certain embodiments, 17 to 20 fins having a height h of about 450mm may be used_msmA length l of about 450mm_msmAnd a width w of about 5mm_msmThe separation module 32. These separation modules 32 may be assembled side-by-side in the dehumidification unit 10, leaving a gap of about 2mm between the separation modules 32. These voids define air channels 16 through which the air 14 flows. The measurements described in this example are merely exemplary and are not intended to be limiting.

Fig. 5 is a psychrometric chart 38 of the temperature and humidity ratio of the humid air 14 flowing through the dehumidification unit 12 of fig. 1-3, in accordance with an embodiment of the present invention. Specifically, the x-axis 40 of the psychrometric chart 38 corresponds to the temperature of the air 14 flowing through the air channel 16 of FIG. 1, the y-axis 42 of the psychrometric chart 38 corresponds to the humidity ratio of the air 14 flowing through the air channel 16, and the curve 44 represents the water vapor saturation curve of the air 14 flowing through the air channel 16. As shown by line 46, because water vapor is removed from the air 14 flowing through the air channel 16, the outlet air 14B humidity ratio (i.e., point 48) from the dehumidification unit 12 of fig. 1-3 is lower than the inlet air 14A humidity ratio (i.e., point 50) into the dehumidification unit 12 of fig. 1-3, and the temperatures of the outlet air 14B and the inlet air 14A are substantially the same.

Referring now to FIG. 1, as described above, a lower partial pressure of the water vapor 26 (i.e., this partial pressure is less than the partial pressure of the water vapor in the air passage 16) is generated in the water vapor passage 18 of the dehumidification unit 10 to further assist H₂O passes from the air channel 16 to the water vapor channel 18 through the interface 20. In certain embodiments, the water vapor channel 18 may be initially evacuated with a vacuum pump 52. Specifically, the vacuum pump 52 may evacuate the water vapor channels 18 and the water vapor vacuum volume 28, as well as the water vapor outlets 22 and the water vapor manifold 24 of fig. 2A. However, in other embodiments, a pump separate from the vacuum pump 52 may be used to evacuate the water vapor channels 18, the water vapor vacuum volume 28, the water vapor outlets 22, and the water vapor manifold 24. From the void in the dehumidification unit 10, as shown in FIG. 1The water vapor 26 removed by the gas 14 will be distinguished between water vapor 26A in the water vapor vacuum volume 28 (i.e., the suction side of the vacuum pump 52) and water vapor 26B expelled from the discharge side (i.e., the outlet) of the vacuum pump 52 (i.e., the water vapor 26B delivered to the condensing unit). In general, the water vapor 26B expelled from the vacuum pump 52 will have a slightly higher pressure and higher temperature than the water vapor 26A in the water vapor vacuum volume 28. The vacuum pump 52 may be a compressor or any other suitable pressure increasing device capable of maintaining a pressure on the suction side of the vacuum pump 52 below the partial pressure of the water vapor in the humid air 14.

For example, the lower partial pressure of the water vapor 26A maintained in the water vapor vacuum volume 28 may be in the range of about 0.15psia to 0.25psia, which corresponds to a saturation temperature of about 45 f to 60 f, with the water vapor 26A typically being in the range of about 65 f to 75 f. However, in other embodiments, the partial pressure of water vapor of the water vapor 26A in the water vapor vacuum volume 28 may be maintained within a range of about 0.01psia to 0.25psia, and the temperature of the water vapor 26A is maintained within a range of about 55 ° f up to the highest ambient air temperature. Particular embodiments may be designed to reduce the partial pressure in the water vapor vacuum volume 28 to the range of 0.01psia to increase the capacity for removing water vapor from the air 14, thereby enabling the evaporative cooler to handle the entire air conditioning load when atmospheric conditions permit this mode of operation.

In certain embodiments, the vacuum pump 52 is a low pressure pump configured to reduce the pressure of the water vapor 26A in the water vapor vacuum volume 28 below the partial pressure of the water vapor on the atmospheric side of the interface 20 (i.e., the partial pressure of the air 14 in the air channel 16). On the discharge side of the vacuum pump 52, the partial pressure 26B of the water vapor has increased just enough to assist in the condensation of the water vapor (i.e., in the condensing unit 54). In practice, the vacuum pump 52 is configured to increase the pressure so as to bring the pressure of the water vapor 26B in the condensing unit 54 close to the minimum saturation pressure in the condensing unit 54.

As an example, when in operation, the air 14 may be vaporized at 0.32psiaEnters the system at a partial vapor pressure corresponding to 0.014 pounds of H per pound of dry air₂Humidity ratio of O. The system may be set to remove 0.005 pounds of H from each pound of dry air in the air 14₂And O. The pressure differential across the interface 20 can be used to generate H₂Flow of O across the interface 20. For example, the partial pressure of water vapor in the water vapor vacuum volume 28 may be set to about 0.1 psia. The pressure of the water vapor 26B is increased by the vacuum pump 52 in a substantially adiabatic process, and as the pressure of the water vapor 26B increases, the temperature also increases (as opposed to a relatively negligible temperature difference across the interface 20). As such, if, for example, the pressure of the water vapor 26B is increased by 0.3psia (i.e., to about 0.4 psia) in the vacuum pump 52, the condensing unit 54 is able to condense the water vapor 26B at a temperature of about 72 to 73 ° f, and the temperature of the water vapor 26B will increase to a temperature substantially above the condenser temperature. The system may continuously monitor the pressure and temperature conditions of both the upstream water vapor 26A and the downstream water vapor 26B to ensure that the water vapor 26B expelled from the vacuum pump 52 has a partial pressure of water vapor that is just high enough to aid in condensation in the condensing unit 54. It should be noted that the pressure and temperature values present in this scenario are merely exemplary and are not intended to be limiting.

Note that as the pressure differential from the water vapor 26A entering the vacuum pump 52 to the water vapor 26B exiting the vacuum pump 52 increases, the efficiency of the dehumidification unit 10 decreases. For example, in a preferred embodiment, the vacuum pump 52 will be set to adjust the pressure of the water vapor 26B in the condensing unit 54 to be slightly higher than the saturation pressure at the lowest ambient temperature of the cooling medium (i.e., air or water) used by the condensing unit 54 to condense the water vapor 26B. In another embodiment, the temperature of the water vapor 26B may be used to control the pressure in the condensing unit 54. The temperature of the water vapor 26B expelled from the vacuum pump 52 may be substantially higher than the humid air 14A (e.g., the temperature may reach 200 ° f or higher depending on various factors). Because the vacuum pump 52 only increases the pressure of the water vapor 26B to a point that facilitates condensation of the water vapor 26B (i.e., approximately the saturation pressure), less power is required by the vacuum pump 52, thereby obtaining high efficiency from the dehumidification unit 10.

Once the water vapor 26B has been slightly pressurized (i.e., compressed) by the vacuum pump 52, the water vapor 26B is directed into a condensing unit 54, where the water vapor 26B condenses to a liquid state. In certain embodiments, the condensing unit 54 may include a condensing coil 56, a tube/pipe condenser, a flat panel condenser, or any other suitable system for causing a temperature below the condensation point of the water vapor 26B. The condensing unit 54 may be air-cooled or water-cooled. For example, in certain embodiments, the condensing unit 54 may be cooled by ambient air or water from a cooling tower. In this way, the cost of operating the condensing unit 54 may be low, as both ambient air and cooling tower water are supplied relatively indefinitely.

Once the water vapor 26B has been condensed into a liquid state, in certain embodiments, the liquid water from the condensing unit 54 may be directed into a reservoir 58 for temporarily storing saturated steam and liquid water. However, in other embodiments, the reservoir 58 may not be used. In either case, the liquid water from the condensing unit 54 may be directed into a liquid pump 60 (i.e., water delivery device) where the pressure of the liquid water from the condensing unit 54 is increased to about atmospheric pressure (i.e., about 14.7 psia) in the liquid pump 60 so that the liquid water may be discharged at ambient conditions. In this way, the liquid pump 60 may be sized just large enough to increase the pressure of the liquid water from the condensing unit 54 to about atmospheric pressure. Thus, the cost of operating the liquid pump 60 may be relatively low. In addition, the liquid water from the liquid pump 60 may increase in temperature slightly due to the increase in pressure of the liquid water. As such, in certain embodiments, the heated liquid water may be transported for use as domestic hot water, further increasing the efficiency of the system by recapturing the heat transferred into the liquid water.

Although described above, the interface 20 between the air channel 16 and the water vapor channel 18 generally allows only H₂O passes from the air passages 16 to the water vapor passages 18, but in some embodiments, a very small amount of other components 30 of the air 14 (e.g., such asLess than 1% oxygen (O)₂) Nitrogen (N)₂) Or other non-condensing component) may allow for transfer from the air channel 16 to the water vapor channel 18 through the interface 20. Over time, the amount of other components 30 may build up in the water vapor channels 18 (as well as in the water vapor vacuum volume 28, water vapor outlet 22, and water vapor manifold 24 of fig. 2A). In general, these other components 30 do not condense at the range of condenser temperatures used in the condensing unit 54. As such, the composition 30 can adversely affect the performance of the vacuum pump 52 and all other equipment downstream of the vacuum pump 52 (specifically, the condensing unit 54).

Thus, in certain embodiments, a second vacuum pump may be used to periodically purge the other components 30 from the water vapor vacuum volume 28. FIG. 6 is a schematic view of the HVAC system 8 and the dehumidification unit 10 and the one or more evaporative cooling units 12 of FIG. 1 having a vacuum pump 62 for removing non-condensable components 30 from the water vapor 26A in the water vapor vacuum volume 28 of the dehumidification unit 10, in accordance with an embodiment of the present invention. In some embodiments, the vacuum pump 62 may be used in conjunction with a vacuum pump for evacuating the water vapor vacuum volume 28 (and the water vapor channels 18, water vapor outlets 22, and water vapor manifold 24) to create the lower partial pressure of water vapor described above to assist in H₂The pump for O transfer from the air channel 16 to the water vapor channel 18 through the interface 20 is the same. However, in other embodiments, the vacuum pump 62 may be different from the pump used to evacuate the water vapor vacuum volume 28 to produce a lower partial pressure of water vapor.

The dehumidification unit 10 described herein may also be controlled between various operating states and adjusted based on the operating conditions of the dehumidification unit 10. For example, FIG. 7 is a schematic illustration of the HVAC system 8 and the dehumidification unit 10 and the one or more evaporative cooling units 12 of FIG. 6 having a control system 64 for controlling various operating conditions of the HVAC system 8 and the dehumidification unit 10 and the one or more evaporative cooling units 12, in accordance with an embodiment of the present invention. Control system 64 may include one or more processors 66, such as one or more "general purpose" microprocessors, one or more special purpose microprocessors and/or ASICS (application specific integrated circuits), or some combination of such processing components. The processor 66 may use input/output (I/O) devices 68, for example, for receiving signals and sending control signals to the components of the dehumidification unit 10 (i.e., the vacuum pumps 52, 62; the condensation unit 54; the reservoir 58; the liquid pump 60; other equipment, such as fans that blow the inlet air 14A through the dehumidification unit 10, sensors configured to generate signals related to characteristics of the inlet air 14A and the outlet air 14B, etc.) and the one or more evaporative cooling units 12. The processor 66 may take these signals as inputs and calculate how to control the functionality of the components of the dehumidification unit 10 and the one or more evaporative cooling units 12 to maximize the efficiency of cooling the air 14 while also removing water vapor 26 from the air 14 flowing through the dehumidification unit 10. The control system 64 may also include a non-transitory computer-readable medium (i.e., memory 70) that may store, for example, instructions or data to be processed by the one or more processors 66 of the control system 64.

For example, the control system 64 may be configured to control the rate at which the non-condensable components 30 of the water vapor 26A are removed from the water vapor vacuum volume 28 of the dehumidification unit 10 by turning the vacuum pump 62 on or off or by adjusting the rate at which the vacuum pump 62 removes the non-condensable components 30 of the water vapor 26A. More specifically, in certain embodiments, the control system 64 may receive signals from sensors in the water vapor vacuum volume 28 that detect when the water vapor 26A contained in the water vapor vacuum volume 28 has an excess of the non-condensable components 30. This process of removing non-condensable components will be operated in a cyclic manner. In "normal" operation to remove the water vapor 26 from the air 14, the vacuum pump 62 will not operate. As the non-condensable components 30 accumulate in the water vapor vacuum volume 28, the internal pressure in the water vapor vacuum volume 28 will eventually reach the set point. At this point, the vacuum pump 62 will be turned on and all components (i.e., non-condensing components 30 and H) will be removed₂O both, including water vapor) until the internal pressure in the water vapor vacuum volume 28 reaches another set point (e.g., below the starting vacuum pressure)Until now. The vacuum pump 62 is then turned off and the dehumidification unit 10 returns to the normal mode of operation. The set point may be preset or dynamically determined. One preferred method is to have the vacuum pump 62 operate in the purge mode only intermittently.

Another example of the type of control that may be implemented by the control system 64 is to regulate the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 (as well as the water vapor channels 18, the water vapor outlets 22, and the water vapor manifold 24) to modify the water vapor removal capacity and efficiency ratio of the dehumidification unit 10. For example, the control system 64 may receive signals from pressure sensors in the water vapor vacuum volume 28, the water vapor channels 18, the water vapor outlets 22, and/or the water vapor manifold 24, and, in addition, signals generated by sensors related to characteristics (e.g., temperature, pressure, flow rate, relative humidity, etc.) of the inlet air 14A and the outlet air 14B. The control system 64 may use this information to determine how to adjust the lower partial pressure of the water vapor 26A (e.g., relative to the partial pressure of the water vapor in the air 14 flowing through the air passage 16) to increase or decrease the rate at which the water vapor 26 is removed from the air passage 16 to the water vapor passage 18 through the interface 20.

For example, if it is desired to remove more water vapor, the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 may be reduced, and conversely, if it is desired to remove less water vapor, the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 may be increased. Further, in certain embodiments, the amount of dehumidification (i.e., water vapor removal) may be cycled to increase the efficiency of the dehumidification unit 10. More specifically, under certain operating conditions, the dehumidification unit 10 may function more efficiently at higher water vapor removal rates. Thus, in certain embodiments, the dehumidification unit 10 may be cycled to remove a maximum amount of water vapor from the air 14 for a period of time, then remove relatively no water vapor from the air 14 for a period of time, then remove a maximum amount of water vapor from the air 14 for a period of time, and so on. In other words, the dehumidification unit 10 may operate at full water vapor removal capacity for a number of cycles that alternate with other cycles that do not remove water vapor. In addition, the control system 64 may be configured to control the start-up and shut-down sequence of the dehumidification unit 10.

The dehumidification unit 10 and the evaporative cooling unit 12 may be designed and operated in a wide variety of modes under varying operating conditions. In general, the dehumidification unit 10 will be at a lower partial pressure of water vapor than the partial pressure of water vapor of the air 14 flowing through the air channels 16 with the water vapor vacuum volume 28 (and the water vapor channels 18, the water vapor outlets 22, and the water vapor manifold 24). In certain embodiments, the dehumidification unit 10 and the evaporative cooling unit 12 may be optimized for Dedicated Outdoor Air System (DOAS) use, wherein the temperature of the air 14 may be in the range of about 55-100 ° f, and the relative humidity of the air 14 is in the range of about 55-100%. In other embodiments, the dehumidification unit 10 and the evaporative cooling unit 12 may be optimized for residential use of recirculated air having a temperature in the range of about 70-85 ° f and a relative humidity in the range of about 55-65%. Similarly, in certain embodiments, the dehumidification unit 10 and the evaporative cooling unit 12 may be optimized for dehumidification of outside air in a commercial building recirculation air system, with the inlet air 14A dehumidified thereby having a temperature in the range of about 55-110 ° f and a relative humidity in the range of about 55-100%. The outlet air 14B has a humidity less than that of the inlet air 14A and has approximately the same temperature as the inlet air 14A unless cooling is performed on the outlet air 14B.

Because of the relatively low pressures required to dehumidify the air 14A, the dehumidification unit 10 described herein requires less operating power than conventional dehumidification systems. This is due, at least in part, to the fact that the interface 20 (i.e., the water vapor permeable membrane) is capable of effectively removing the water vapor 26 from the air 14 without requiring excessive pressure to force the water vapor 26 through the interface 20. For example, in one embodiment, the minimum power required to operate the dehumidification unit 10 includes only: fan power required to move the air 14 through the dehumidification unit 10; the compression power of vacuum pump 52 to compress water vapor 26 to approximately the saturation pressure (e.g., to about 1.0psia, or to a saturation pressure corresponding to a given condensation temperature of, for example, about 100 ° f); the pumping and/or fan power of the condensing unit 54 (e.g., depending on whether cooling tower water or ambient air is used as the cooling medium); the pumping power of the liquid pump 60 that discharges liquid water from the condensing unit 54 at ambient conditions; and the power of the vacuum pump 62 to purge the non-condensable components 30 from leaking into the water vapor vacuum volume 28 of the dehumidification unit 10. As such, the only relatively significant power component required to operate the dehumidification unit 10 is the compression power of the vacuum pump 52 to compress the water vapor 26 to approximately the saturation pressure (e.g., to only about 1.0psia, or to a saturation pressure corresponding to a given condensation temperature, such as about 100 ° f). As described above, this power is relatively low, and therefore, it is relatively inexpensive to operate the dehumidification unit 10, as opposed to conventional refrigeration compression dehumidification systems. Moreover, calculations of the embodiment show that the dehumidification unit 10 has a coefficient of performance (COP) at least twice as high (or even up to five times as high, depending on operating conditions) as these conventional dehumidification systems. In addition, the dehumidification unit 10 is capable of dehumidifying air without reducing the air temperature to a desired air temperature as is often done with conventional dehumidification systems.

In certain embodiments, as noted above, the dehumidification unit 10 described with reference to fig. 1-7 may be used in conjunction with one or more evaporative cooling units 12. For example, FIG. 8 is a schematic diagram of an HVAC system 72 having an evaporative cooling unit 74 disposed upstream of the dehumidification unit 10, in accordance with an embodiment of the present invention. The HVAC system 72 of fig. 8 has substantially the same functionality as the HVAC system 8 of fig. 1, 6 and 7. However, as shown in FIG. 8, the HVAC system 72 includes exclusively an evaporative cooling unit 74 disposed upstream of the dehumidification unit 10. Thus, the HVAC system 72 first receives the relatively humid inlet air 14A into the evaporative cooling unit 74 rather than the dehumidification unit 10. The evaporative cooling unit 74 reduces the temperature of the relatively humid inlet air 14A and expels the cooler (but still relatively humid) air 14B, which air 14B is directed into the dehumidification unit 10 via the duct 76. As described above, the cooler (but still relatively humid) air 14B is then dehumidified in the dehumidification unit 10 and expelled into the conditioned space as relatively dry air 14C.

The evaporative cooling unit 74 of FIG. 8 may be a direct evaporative cooling unit or an indirect evaporative cooling unit. In other words, when the evaporative cooling unit 74 uses direct evaporative cooling techniques, relatively cool and moist media 78 (e.g., relatively cool water) is added directly to the relatively humid inlet air 14A. However, when the evaporative cooling unit 74 uses indirect evaporative cooling techniques, the relatively humid air 14A may flow across one side of the plates of the heat exchanger, for example, while the relatively cool and humid medium 78 flows across the other side of the plates of the heat exchanger. In other words, in general, some of the relatively cool moisture from the relatively cool and moist media 78 is indirectly added to the relatively moist air 14A. Whether direct evaporative cooling techniques or indirect evaporative cooling techniques are used in the evaporative cooling unit 74, the rate of humidity removal and temperature reduction of the air 14 flowing through the HVAC system 72 of FIG. 8 is affected. In general, however, the evaporative cooling unit 74 of FIG. 8 initially cools the air 14 to as low a temperature as possible for a particular application, and the dehumidification unit 10 reduces the humidity ratio at an approximately constant temperature.

As shown, many of the components of the HVAC system 72 of fig. 8 may be considered the same as the components of the HVAC system 8 of fig. 1, 6, and 7. For example, as described above, the HVAC system 72 of fig. 8 includes the condensing unit 54, the partial pressure of the water vapor 26B received by the condensing unit 54 being just high enough to facilitate condensation as described above. In certain embodiments, the HVAC system 72 of fig. 8 may also include a reservoir 58 for temporarily storing saturated steam and liquid water. However, as described above, in other embodiments, the reservoir may not be used. In either case, the liquid water from the condensing unit 54 may be directed into a liquid pump 60, where the pressure of the liquid water from the condensing unit 54 is increased to about atmospheric pressure (i.e., about 14.7 psia) within the liquid pump 60, thereby allowing the liquid water to drain at ambient conditions.

Additionally, the control system 64 of FIG. 7 may also be used in the HVAC system 72 of FIG. 8 to control the operation of the HVAC system 72 in a manner similar to that described above with reference to FIG. 7. For example, as described above, the control system 64 may be configured to control the rate at which the non-condensable components 30 of the water vapor 26A are removed from the water vapor vacuum volume 28 by turning the vacuum pump 52 (or the separate vacuum pump 62) on or off or by adjusting the rate at which the vacuum pump 52 (or the separate vacuum pump 62) removes the non-condensable components 30 of the water vapor 26A. More specifically, in certain embodiments, the control system 64 may receive signals from sensors in the water vapor vacuum volume 28 that detect when the water vapor 26A contained in the water vapor vacuum volume 28 has too many non-condensable components 30.

Additionally, the control system 64 may adjust the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28, thereby modifying the water vapor removal capacity and efficiency ratio of the dehumidification unit 10. For example, the control system 64 may receive signals from the water vapor vacuum volume 28, pressure sensors in the water vapor passage 18, and in addition signals generated by sensors related to characteristics (e.g., temperature, pressure, flow rate, relative humidity, etc.) of the air 14 in the evaporative cooling unit 74, the dehumidification unit 10, or both.

The control system 64 may use this information to determine how to adjust the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 to increase or decrease the rate at which the water vapor 26 is removed from the air passage 16 as H2O through the interface 20 of the dehumidification unit 10 (i.e., as water molecules, gaseous water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, etc., through the interface 20) to the water vapor passage 18. For example, if it is desired to remove more water vapor, the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 may be reduced, and conversely, if it is desired to remove less water vapor, the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 may be increased. Further, as described above, the amount of dehumidification (i.e., removal of water vapor) may be cycled to increase the efficiency of the dehumidification unit 10. More specifically, under certain operating conditions, the dehumidification unit 10 may function more efficiently at higher water vapor removal rates. Thus, in certain embodiments, the dehumidification unit 10 may be cycled to remove a maximum amount of water vapor from the air 14 for a period of time, then remove relatively no water vapor from the air 14 for a period of time, then remove a maximum amount of water vapor from the air 14 for a period of time, and so on. In other words, the dehumidification unit 10 may operate at full water vapor removal capacity for a number of cycles that alternate with other cycles that do not remove water vapor.

Further, the control system 64 may also be configured to control the operation of the evaporative cooling unit 74. For example, the control system 64 may selectively regulate how evaporative cooling occurs (directly or indirectly) in the evaporative cooling unit 74. As an example, a valve may be actuated to control the flow rate of the relatively cool and moist media 78 through the evaporative cooling unit 74, thereby directly affecting the amount of (direct or indirect) evaporative cooling in the evaporative cooling unit 74. In addition, the operation of the evaporative cooling unit 74 and the dehumidification unit 10 may be controlled simultaneously. In addition, the control system 64 may be configured to control the start-up and shut-down sequence of the evaporative cooling unit 74 and the dehumidification unit 10.

Fig. 9A and 9B are temperature and humidity maps 80, 82 of the temperature and humidity ratio of the air 14 flowing through the evaporative cooling unit 74 and the dehumidification unit 10 of fig. 8, in accordance with an embodiment of the present invention. More specifically, FIG. 9A is a psychrometric chart 80 of the temperature and humidity ratio of the air 14 flowing through the direct evaporative cooling unit 74 and the dehumidification unit 10 of FIG. 8, and FIG. 9B is a psychrometric chart 82 of the temperature and humidity ratio of the air 14 flowing through the indirect evaporative cooling unit 74 and the dehumidification unit 10 of FIG. 8, according to an embodiment of the present invention. Specifically, in each of the graphs 80, 82, the x-axis 84 corresponds to the temperature of the air 14 flowing through the evaporative cooling unit 74 and the dehumidification unit 10 of FIG. 8, the y-axis 86 corresponds to the humidity ratio of the air 14 flowing through the evaporative cooling unit 74 and the dehumidification unit 10 of FIG. 8, and the curve 88 represents a water vapor saturation curve for a given relative humidity ratio of the air 14 flowing through the evaporative cooling unit 74 and the dehumidification unit 10 of FIG. 8.

As shown by line 90 of fig. 9A, because the relatively cool and moist media 78 is introduced directly into the air 14 flowing through the direct evaporative cooling unit 74, the humidity ratio of the air 14B exiting the direct evaporative cooling unit 74 (i.e., point 92) is substantially higher than the humidity ratio of the inlet air 14A entering the direct evaporative cooling unit 74 (i.e., point 94). However, the temperature of the air 14B exiting the direct evaporative cooling unit 74 (i.e., point 92) is substantially lower than the temperature of the inlet air 14A entering the evaporative cooling unit 74 (i.e., point 94). As shown by line 96 of FIG. 9A, because the water vapor 26 is removed from the air 14B flowing through the dehumidification unit 10, the humidity ratio of the outlet air 14C from the dehumidification unit 10 (i.e., point 98) is lower than the humidity ratio of the air 14B entering the dehumidification unit 10 (i.e., point 92), but the temperatures of the outlet air 14C and the air 14B are substantially the same. In effect, the direct evaporative cooling unit 74 humidifies and cools the air 14, while the dehumidification unit 10 subsequently dehumidifies the air 14 at a substantially constant temperature.

As shown by line 100 in fig. 9B, since the relatively cool and moist media 78 indirectly cools the air 14 flowing through the indirect evaporative cooling unit 74, the humidity ratio of the air 14B exiting the indirect evaporative cooling unit 74 (i.e., point 102) is substantially the same as the humidity ratio of the inlet air 14A entering the indirect evaporative cooling unit 74 (i.e., point 104). However, the temperature of the air 14B exiting the indirect evaporative cooling unit 74 (i.e., point 102) is substantially lower than the temperature of the inlet air 14A entering the indirect evaporative cooling unit 74 (i.e., point 104). As shown by line 106 of FIG. 9B, as the water vapor 26 is removed from the air 14B flowing through the dehumidification unit 10, the humidity ratio of the outlet air 14C from the dehumidification unit 10 (i.e., point 108) is lower than the humidity ratio of the air 14B entering the dehumidification unit 10 (i.e., point 102), but the temperatures of the outlet air 14C and the air 14B are substantially the same. In effect, the indirect evaporative cooling unit 74 cools the air 14 (without substantially humidifying the air 14), while the dehumidification unit 10 subsequently dehumidifies the air 14 at a substantially constant temperature.

As described above, the control system 64 of FIG. 8 may be configured to control the operation of the evaporative cooling unit 74 and the dehumidification unit 10. For example, when using direct and indirect evaporative cooling techniques, respectively, in the evaporative cooling unit 74 of fig. 8, the control system 64 may be configured to adjust the locations at which the points 92, 94, 98 and 102, 104, 108 of the air 14 fall into the psychrometric charts 80, 82 of fig. 9A and 9B.

FIG. 10 is a schematic view of an HVAC system 110 having an evaporative cooling unit 74 disposed downstream of the dehumidification unit 10, in accordance with an embodiment of the present invention, 110. The HVAC system 110 of fig. 10 has substantially the same functionality as the HVAC system 8 of fig. 1, 6, and 7 and the HVAC system 72 of fig. 8. However, as shown in FIG. 10, the HVAC system 110 first receives relatively humid inlet air 14A into the dehumidification unit 10. As described above, the relatively humid inlet air 14A is first dehumidified in the dehumidification unit 10 and expelled into the duct 76 as relatively dry air 14B. The evaporative cooling unit 74, in turn, lowers the temperature of the dry air 14B and expels the cooler dry air 14C into the conditioned space.

As described above with reference to FIG. 8, the evaporative cooling unit 74 of FIG. 10 may be a direct evaporative cooling unit or an indirect evaporative cooling unit. In other words, when the evaporative cooling unit 74 uses direct evaporative cooling techniques, a relatively cool and moist media 78 (e.g., relatively cool water) is added directly to the relatively dry air 14B in the conduit 76. However, when the evaporative cooling unit 74 uses indirect evaporative cooling techniques, the relatively dry air 14B may flow across one side of the plates of the heat exchanger, for example, while the relatively cool and humid medium 78 flows across the other side of the plates of the heat exchanger. In other words, in general, some relatively cool moisture from the relatively cool and moist media 78 is indirectly added to the relatively dry air 14B in the duct 76. Whether direct evaporative cooling techniques or indirect evaporative cooling techniques are used in the evaporative cooling unit 74, the rate of humidity removal and temperature reduction of the air 14 flowing through the HVAC system 110 of FIG. 10 is affected. In general, however, the dehumidification unit 10 initially reduces the humidity ratio at an approximately constant temperature, and the evaporative cooling unit 74 cools the air 14 to as low a temperature as possible for the particular application.

As shown, many of the components of the HVAC system 110 of fig. 10 may be considered the same as the components of the HVAC system 8 of fig. 1, 6, and 7 and the HVAC system 72 of fig. 8. For example, as described above, the HVAC system 110 of fig. 10 includes a condensing unit 54, the partial pressure of the water vapor 26B received by the condensing unit 54 being just high enough to facilitate condensation as described above. In certain embodiments, the HVAC system 110 of fig. 10 may further include a reservoir 58, the reservoir 58 for temporarily storing saturated steam and liquid water. However, as described above, in other embodiments, the reservoir may not be used. In either case, the liquid water from the condensing unit 54 may be directed into a liquid pump 60, where the pressure of the liquid water from the condensing unit 54 is increased to about atmospheric pressure (i.e., about 14.7 psia) within the liquid pump 60, thereby allowing the liquid water to be discharged at ambient conditions.

Additionally, the control system 64 of fig. 7 and 8 may also be used in the HVAC system 110 of fig. 10 to control the operation of the HVAC system 110 in a manner similar to that described above with reference to fig. 7 and 8. For example, as described above, the control system 64 may be configured to control the rate at which the non-condensable components 30 of the water vapor 26A are removed from the water vapor vacuum volume 28 by turning the vacuum pump 52 (or the separate vacuum pump 62) on or off or by adjusting the rate at which the vacuum pump 52 (or the separate vacuum pump 62) removes the non-condensable components 30 of the water vapor 26A. More specifically, in certain embodiments, the control system 64 may receive signals from sensors in the water vapor vacuum volume 28 that detect when the water vapor 26A contained in the water vapor vacuum volume 28 has an excess of the non-condensable components 30.

Additionally, the control system 64 may adjust the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 to modify the water vapor removal capacity and efficiency ratio of the dehumidification unit 10. For example, the control system 64 may receive signals from the water vapor vacuum volume 28, pressure sensors in the water vapor passage 18, and in addition signals generated by sensors related to characteristics (e.g., temperature, pressure, flow rate, relative humidity, etc.) of the air 14 in the dehumidification unit 10, the evaporative cooling unit 74.

The control system 64 may use this information to determine how to adjust the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 to increase or decrease the flow of water vapor 26 from the air passage 16 as H₂The rate at which O is removed to the water vapor channels 18 through the interfaces 20 of the dehumidification unit 10 (i.e., as water molecules, gaseous water vapor, liquid water, adsorbed/desorbed water molecules, absorbed/desorbed water molecules, etc., through the interfaces 20). For example, if it is desired to remove more water vapor, the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 may be reduced, and conversely, if it is desired to remove less water vapor, the lower partial pressure of the water vapor 26A in the water vapor vacuum volume 28 may be increased. Further, as described above, the amount of dehumidification (i.e., removal of water vapor) may be cycled to increase the efficiency of the dehumidification unit 10. More specifically, under certain operating conditions, the dehumidification unit 10 may function more efficiently at higher water vapor removal rates. Thus, in certain embodiments, the dehumidification unit 10 may be cycled to remove a maximum amount of water vapor from the air 14 for a period of time, then remove relatively no water vapor from the air 14 for a period of time, then remove a maximum amount of water vapor from the air 14 for a period of time, and so on. In other words, the dehumidification unit 10 may operate at full water vapor removal capacity for a number of cycles that alternate with other cycles that do not remove water vapor.

FIGS. 11A and 11B are temperature and humidity maps 112, 114 of the temperature and humidity ratio of the air 14 flowing through the dehumidification unit 10 and the evaporative cooling unit 74 of FIG. 10, in accordance with embodiments of the present invention. More specifically, FIG. 11A is a psychrometric chart 112 of the temperature and humidity ratio of the air 14 flowing through the dehumidification unit 10 and the direct evaporative cooling unit 74 of FIG. 10, and FIG. 11B is a psychrometric chart 114 of the temperature and humidity ratio of the air 14 flowing through the dehumidification unit 10 and the indirect evaporative cooling unit 74 of FIG. 10, according to an embodiment of the present invention. Specifically, as described above with reference to FIGS. 9A and 9B, the x-axis 84 corresponds to the temperature of the air 14 flowing through the dehumidification unit 10 and the evaporative cooling unit 74 of FIG. 10, the y-axis 86 corresponds to the humidity ratio of the air 14 flowing through the dehumidification unit 10 and the evaporative cooling unit 74 of FIG. 10, and the curve 88 represents a water vapor saturation curve for a given relative humidity ratio of the air 14 flowing through the dehumidification unit 10 and the evaporative cooling unit 74 of FIG. 10.

As shown by line 116 in FIG. 11A, as the water vapor 26 is removed from the relatively humid inlet air 14A flowing through the dehumidification unit 10, the humidity ratio of the relatively dry air 14B from the dehumidification unit 10 (i.e., point 118) is lower than the humidity ratio of the relatively humid inlet air 14A entering the dehumidification unit 10 (i.e., point 120), and the temperatures of the relatively dry air 14B and the relatively humid inlet air 14A are substantially the same. As shown by line 122 of fig. 11A, since the relatively cool and moist media 78 is introduced directly into the relatively dry air 14B flowing through the direct evaporative cooling unit 74, the humidity ratio of the outlet air 14C from the direct evaporative cooling unit 74 (i.e., point 124) is substantially higher than the humidity ratio of the relatively dry air 14B entering the direct evaporative cooling unit 74 (i.e., point 118). However, the temperature of the outlet air 14C from the direct evaporative cooling unit 74 (i.e., point 124) is substantially lower than the temperature of the relatively dry air 14B entering the direct evaporative cooling unit 74 (i.e., point 118). In practice, the dehumidification unit 10 dehumidifies the air 14 at a substantially constant temperature, while the direct evaporative cooling unit 74 subsequently humidifies and cools the air 14.

As shown by line 126 in FIG. 11B, because the water vapor 26 is removed from the relatively humid inlet air 14A flowing through the dehumidification unit 10, the humidity ratio of the relatively dry air 14B from the dehumidification unit 10 (i.e., point 128) is lower than the humidity ratio of the relatively humid inlet air 14A entering the dehumidification unit 10 (i.e., point 130), but the temperatures of the relatively dry air 14B and the relatively humid inlet air 14A are substantially the same. As shown by line 132 of FIG. 11B, since the relatively cool and moist media 78 indirectly cools the relatively dry air 14B flowing through the indirect evaporative cooling unit 74, the humidity ratio of the outlet air 14C from the indirect evaporative cooling unit 74 (i.e., point 134) is substantially the same as the humidity ratio of the relatively dry air 14B entering the indirect evaporative cooling unit 74 (i.e., point 128). However, the temperature of the outlet air 14C from the indirect evaporative cooling unit 74 (i.e., point 134) is substantially lower than the temperature of the relatively dry air 14B entering the indirect evaporative cooling unit 74 (i.e., point 128). In practice, the dehumidification unit 10 dehumidifies the air 14 at a substantially constant temperature, while the indirect evaporative cooling unit 74 cools the air 14 (substantially without humidifying the air 14).

As described above, the control system 64 of FIG. 10 may be configured to control the operation of the dehumidification unit 10 and the evaporative cooling unit 74. For example, when using direct and indirect evaporative cooling techniques, respectively, in the evaporative cooling unit 74 of fig. 10, the control system 64 may be configured to adjust the locations at which the points 118, 120, 124 and 128, 130, 134 of the air 14 fall into the psychrometric charts 112, 114 of fig. 11A and 11B.

The embodiments of the HVAC systems 72, 110 of fig. 8 and 10 are not the only way in which the dehumidification unit 10 may be used in combination with the evaporative cooling unit 74. More specifically, fig. 8 and 10 illustrate the use of a single dehumidification unit 10 and a single evaporative cooling unit 74 in series with one another, and in other embodiments, any number of dehumidification units 10 and evaporative cooling units 74 may be used in series with one another. For example, FIG. 1 shows a dehumidification unit 10 having evaporative cooling units disposed on both sides (i.e., upstream and downstream sides) of the dehumidification unit 10. As another example, in one embodiment, the first dehumidification unit 10 may be followed by a first evaporative cooling unit 74, the first evaporative cooling unit 74 being followed by a second dehumidification unit 10, the second dehumidification unit 10 being followed by a second evaporative cooling unit 74, and so on. However, any number of dehumidification units 10 and evaporative cooling units 74 may in fact be used in series with one another, with the air 14 exiting each unit 10, 74 being directed into the next downstream unit 10, 74 in the series sequence (except for the last unit 10, 74 in the series from which the air 14 is expelled into the conditioned space). In other words, the air 14 exiting each dehumidification unit 10 in the series is directed into the downstream evaporative cooling unit 74 (or to the air-conditioned space if the downstream evaporative cooling unit is the last unit in the series), and the air 14 exiting each evaporative cooling unit 74 in the series is directed into the downstream dehumidification unit 10 (or to the air-conditioned space if the downstream dehumidification unit is the last unit in the series). In this way, the temperature of the air 14 may be successively lowered in each evaporative cooling unit 74 between the dehumidification units 10 in the series, and the humidity ratio of the air 14 may be successively lowered in each dehumidification unit 10 between the evaporative cooling units 74 in the series. This process may continue in any number of dehumidification units 10 and evaporative cooling units 74 until the desired final temperature and humidity ratio conditions of the air 14 are achieved.

Fig. 12A and 12B are temperature and humidity maps 136, 138 of the temperature and humidity ratio of the air 14 flowing through the plurality of dehumidification units 10 and the plurality of evaporative cooling units 74, in accordance with an embodiment of the present invention. More specifically, fig. 12A is a temperature-humidity map 136 of the temperature and humidity ratio of the air 14 flowing through the plurality of dehumidification units 10 and the plurality of direct evaporative cooling units 74, and fig. 12B is a temperature-humidity map 138 of the temperature and humidity ratio of the air 14 flowing through the plurality of dehumidification units 10 and the plurality of indirect evaporative cooling units 74, according to an embodiment of the present invention. Specifically, in each of the graphs 136, 138, the x-axis 84 corresponds to the temperature of the air 14 flowing through the plurality of dehumidification units 10 and the plurality of evaporative cooling units 74, the y-axis 86 corresponds to the humidity ratio of the air 14 flowing through the plurality of dehumidification units 10 and the plurality of evaporative cooling units 74, and the curve 88 represents a water vapor saturation curve for a given relative humidity ratio of the air 14 flowing through the plurality of dehumidification units 10 and the plurality of evaporative cooling units 74.

As shown by line 140 in FIG. 12A, because the water vapor 26 is removed from the relatively humid air 14 flowing through each of the plurality of dehumidification units 10, the humidity ratio of the air 14 is substantially reduced, but the temperature of the air 14 remains substantially the same in each of the plurality of dehumidification units 10. As shown by line 142 in fig. 12A, since the relatively cool and moist media 78 is directly introduced into the relatively dry air 14 flowing through each of the plurality of direct evaporative cooling units 74, the humidity ratio of the air 14 increases, but the temperature of the air 14 substantially decreases in each of the plurality of direct evaporative cooling units 74. In other words, each of the plurality of dehumidification units 10 successively dehumidifies the air 14 at a substantially constant temperature, while each of the plurality of direct evaporative cooling units 74 successively humidifies and cools the air 14 until desired final temperature and humidity ratio conditions are achieved. More specifically, as shown in FIG. 12A, the lines 140, 142 generally form a "step function" progression from an initial temperature and humidity ratio condition of the inlet air 14 (i.e., point 144) to a final temperature and humidity ratio condition of the outlet air 14 (i.e., point 146).

As shown by line 148 in FIG. 12B, the humidity ratio of the air 14 is substantially reduced due to the removal of the water vapor 26 from the relatively humid air 14 flowing through each of the plurality of dehumidification units 10, but the temperature of the air 14 remains substantially the same in each of the plurality of dehumidification units 10. As shown by line 150 in fig. 12B, the humidity ratio of the air 14 remains substantially the same, but the temperature of the air 14 is substantially reduced in each of the plurality of indirect evaporative cooling units 74, as the relatively cool and moist media 78 indirectly interacts with the relatively dry air 14 flowing through each of the plurality of indirect evaporative cooling units 74. In other words, each of the plurality of dehumidification units 10 successively dehumidifies the air 14 at a substantially constant temperature, while each of the plurality of indirect evaporative cooling units 74 successively cools the air 14 at a substantially constant humidity ratio until desired final temperature and humidity ratio conditions are achieved. More specifically, as shown in FIG. 12B, the lines 148, 150 generally form a "saw tooth" progression from the initial temperature and humidity ratio condition of the inlet air 14 (i.e., point 152) to the final temperature and humidity ratio condition of the outlet air 14 (i.e., point 154).

Because of the use of evaporative cooling units 74 between dehumidification units 10, each dehumidification unit 10 will receive air 14 that is cooler and at a lower partial pressure of water vapor than the upstream dehumidification unit 10. In this way, each of the plurality of dehumidification units 10 will operate under substantially different operating conditions. Thus, the control system 64 may be used to adjust operating parameters of the dehumidification unit 10 (e.g., the partial pressure of water vapor in the water vapor vacuum volume 28) to account for variations between the dehumidification units 10. Similarly, because of the use of the dehumidification unit 10 between evaporative cooling units 74, each evaporative cooling unit 74 will also receive cooler air 14 at a lower partial pressure of water vapor than the upstream evaporative cooling unit 74. In this way, each of the evaporative cooling units 74 will also operate under substantially different operating conditions. Accordingly, the control system 64 may also be used to adjust operating parameters of the evaporative cooling units 74 (e.g., the flow rate of the relatively cool and moist media 78) to account for variations between the evaporative cooling units 74. In addition, the control system 64 may also coordinate the operation of multiple dehumidification units 10 and multiple evaporative cooling units 74 simultaneously to account for variables.

The evaporative cooling unit 74 of fig. 8 and 10 may not reduce the temperature of the air 14, but may clean the air 14 by, for example, passing the air 14 through a wet fiber mat. Additionally, the dehumidification unit 10 and the evaporative cooling unit 14 may be operated at variable or fixed speeds to achieve optimal operation between different initial temperature and humidity conditions (i.e., operating points 144 and 152 in fig. 12A and 12B, respectively) and final temperature and humidity conditions (i.e., operating points 146 and 154 in fig. 12A and 12B, respectively). Furthermore, the evaporative cooling unit 74 is a relatively low energy unit, thereby minimizing overall operating costs.

While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and tables and have been described in detail herein. It should be understood, however, that the embodiments are not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims. Additionally, while various embodiments are discussed herein, the present invention is intended to cover all combinations of these embodiments.

Claims

1. A dehumidification system for removing water vapor from an air stream, the dehumidification system comprising:

a first channel and a second channel separated by a membrane, wherein the membrane is configured to pass H assisted from water vapor₂O passes through the permeable volume of the membrane to the second channel and substantially blocks passage of all other components of the air stream through the membrane to effect removal of water vapor from the air stream flowing through the first channel;

a first evaporative cooling unit configured to cool an air stream downstream of the membrane;

a second evaporative cooling unit configured to cool an air flow upstream of the membrane;

a pressure increasing device configured to generate a lower partial pressure of water vapor in the second passage than in the first passage so as to cause H₂O moves past the membrane to the second channel, wherein the pressure increasing device is further configured to increase the water vapor pressure at the outlet of the pressure increasing device to a water vapor partial pressure in a range suitable for subsequent condensation to liquid water, wherein the air flow is delivered to the membrane at substantially atmospheric pressure; and

a controller configured to control operation of the dehumidification system.

2. The dehumidification system of claim 1, wherein the second evaporative cooling unit is upstream of the first channel and directs air flow into the first channel.

3. The dehumidification system of claim 2, wherein the first evaporative cooling unit is downstream of the first channel and receives an air stream from the first channel.

4. The dehumidification system of claim 1, comprising a condensation device configured to receive the water vapor from the pressure increasing device and condense the water vapor into liquid water.

5. The dehumidification system of claim 4, comprising a water transport device configured to transport liquid water from the condensation device.

6. The dehumidification system of claim 1, wherein the membrane comprises a zeolite.

7. A system, comprising:

for removing H from an air stream₂A dehumidification unit of O vapor, the dehumidification unit comprising:

an air passage configured to receive an inlet airflow and a discharge outlet airflow; and

a through H adjacent to the air channel₂O material, wherein the H permeability₂The O material is configured to selectively allow H from the inlet airflow₂H of O vapor₂O passes through the through H₂O material to said H₂O suction side of the material and substantially blocks passage of other components of the inlet air stream through the H-permeable membrane₂O material to said H₂A suction side of O material, wherein the inlet air flow is delivered to the H penetration at substantially atmospheric pressure₂An O material;

an evaporative cooling unit configured to cool an air flow; and

a pressure increasing device configured for the permeation H₂Producing H in the inlet air flow on the suction side of the O material₂H with lower partial pressure of O vapor₂Partial pressure of O vapor, driving H from the inlet air stream₂H of O vapor₂O passes through the through H₂O material, and increasing the pressure at the outlet of the pressure increasing device to be suitable for H₂Condensing O vapor into liquid H₂H of O₂Partial pressure of O vapor.

8. The system of claim 7, wherein the evaporative cooling unit is upstream of the dehumidification unit and directs an inlet airflow into the air channel.

9. The system of claim 7, wherein the evaporative cooling unit is downstream of the dehumidification unit and receives an outlet air stream from the air channel.

10. The system of claim 7, comprising a condensing device configured to receive H from an outlet of the pressure increasing device₂O is vaporized, and H is₂Condensing O vapor into liquid H₂O。

11. The system of claim 10, comprising a liquid pump configured to transport liquid H from the condensing device₂O。

12. The system of claim 7, wherein the through H is₂The O material comprises a material permeable to H₂And (3) an O film.

13. The system of claim 7, wherein the through H is₂The O material includes a zeolite.

14. The system of claim 7, wherein the dehumidification unit is a variable speed dehumidification unit and the evaporative cooling unit is a variable speed evaporative cooling unit.

15. A method, comprising:

receiving includes H₂The air flow including O steam flows into an air passage of the dehumidification unit, wherein the air flow has H₂A first partial pressure of O vapor, and wherein an air stream is delivered to the dehumidification unit at substantially air pressure;

cooling the air stream via an evaporative cooling unit;

by means of a transparent H crossing the dehumidifying unit₂Pressure difference of O material will be H₂O passes through the hydrogen permeable membrane₂H of O material sucked to the dehumidification unit₂O vapor channel, wherein the H permeation₂The O material comprises a zeolite, and the H₂O steam channel having lower than air flowH of (A) to (B)₂H of first partial pressure of O steam₂O steam second partial pressure; and

will be from the H₂H of O vapor channel₂Receiving O vapor into a pressure increasing device, and feeding H from the pressure increasing device₂Increasing the pressure of O vapor above the H₂H of second partial pressure of O steam₂O vapor third partial pressure.

16. The method of claim 15, comprising: cooling an air stream via the evaporative cooling unit prior to directing the air stream into the dehumidification unit.

17. The method of claim 15, comprising: cooling an air stream via the evaporative cooling unit after receiving the air stream from the dehumidification unit.

18. The method of claim 15, comprising: cooling the airflow via a first evaporative cooling unit prior to directing the airflow into the dehumidification unit, and cooling the airflow via a second evaporative cooling unit after receiving the airflow from the dehumidification unit.

19. The method of claim 15, comprising: h from the pressure increasing device₂O vapor is received into a condensing unit and the H is₂Condensing O vapor into liquid H₂O。

20. The method of claim 19, wherein the air stream has a H₂O steam first partial pressure in the range of about 0.2psia to 1.0psia, the H₂A second partial pressure of O vapor is in the range of about 0.1psia to 1.0psia, and the H vapor is₂The third vapor partial pressure is in the range of about 0.25psia to 1.1 psia.