HK1132543B - Improved air conditioning system - Google Patents

Description

Improved air conditioning system

RELATED APPLICATIONS

This international patent application claims priority from australian provisional patent application 2006906435, the specification of which is incorporated herein by reference.

Technical Field

The present invention relates to an improved air conditioning system, including methods and apparatus for controlling the improved air conditioning system.

Background

Conventional air conditioning design theory was challenged in the 90 s of the twentieth century by a series of innovative ideas proposed by the deceased doctor alanshaw. These concepts of peaking with air conditioning control systems are described in united states patent 6,269,650 to Shaw. This patent and the system it describes are now owned by the applicant and will be referred to as the "Shaw system" throughout this specification.

The Shaw system is one of the following: the air conditioning function operates in parallel to separate the process of handling latent heat load (typically, moisture is removed from the outdoor air) and sensible heat load (typically, dried inside air). The Shaw system differs from conventional air conditioning processes in that, rather than taking untreated outdoor air and then cooling it throughout the air conditioning system, the incoming outdoor air is pre-treated (dehumidified and cooled) by a separate first outdoor air heat exchanger before being merged with the generally dry (treated or untreated) interior air that has been cooled. The two air streams merge and are then delivered to the conditioned space.

The Shaw system is a dual heat exchanger system that provides the additional benefit of allowing the same flow of cooling medium (typically water) to pass through two heat exchangers in series to maximize efficiency. This dual heat exchanger process also avoids the following conventional need: high energy is input at both levels to first subcool the air and then reheat the air in order to maintain the desired humidity level in the conditioned space. In combination with a control system that allows integrated control of humidity, temperature and cooling operations, it has been demonstrated that the air handling process of the Shaw system can optimize energy performance at all times of the operating cycle, thereby providing significantly reduced energy consumption and precise control of humidity and temperature fluctuations in the conditioned space.

However, Shaw systems are designed for use in moderate typical cooling situations where the building requirements dictate only the use of a standard amount of ventilation (such as about 10% to 20% outdoor air) and only need to produce an environment that meets moderate standard comfort levels. Indeed, with outdoor air ventilation levels up to about 25%, the Shaw system has been found to operate successfully to provide the above-described benefits for typically average conditioned space temperature and humidity targets.

On the other hand, for special applications where ventilation requirements require the use of higher levels of outdoor air (such as in hospitals and special laboratories where outdoor air levels of 40-50% are typically required), it has been found that the Shaw system has a tendency to overcool the conditioned space. Moreover, Shaw systems can still suffer from energy inefficiencies, for example, if needed to produce abnormal levels of dehumidification such as are required to provide extremely low dew point temperatures. It is therefore an object of the present invention to provide an improvement to the Shaw system that allows for ease of adoption of the Shaw system in situations such as these and where multiple thermal zones in a conditioned space need to be provided and controlled with a single dry bulb and integrated absolute humidity control.

Before turning to the summary of the invention, it must be understood that the above description of the prior art is merely provided as a background to illustrate the context of the present invention. It is not an admission that any of the material referred to was published or known, or was part of the common general knowledge in australia or elsewhere.

Disclosure of Invention

In general terms, the present invention provides an air conditioning system that is an improvement over the Shaw system described above in that it utilizes at least two additional heat exchangers and a variable speed pump to recover energy for dehumidification that is not required to meet the dry bulb conditions of the conditioned space. The improved air conditioning system of the present invention provides controlled separation from the saturation curve on moisture determination.

The present invention provides an air conditioning system capable of treating a conditioned space by treating outdoor air from outside the conditioned space and return air from inside the conditioned space and mixing the outdoor air with the return air to form supply air for the conditioned space, the air conditioning system comprising:

an outdoor air latent heat cooling process section configured to provide an air stream in juxtaposition with a return air sensible cooling process section; and

means for mixing outdoor air with return air to form conditioned space supply air,

wherein the outdoor air latent heat cooling process section comprises at least a dehumidification heat exchanger, a combined pre-cooling and heat recovery heat exchanger, and a heat transfer pump, and the return air sensible cooling process section comprises at least a sensible cooling heat exchanger.

Reference above and throughout this specification to "side-by-side air flow" is understood to mean that the two treatment stages are configured such that latent heat cooling is performed on the outdoor air before it is mixed with treated return air (treatment in the sense of return air that has been subjected to sensible heat cooling), but sensible heat cooling is required on the return air before it is mixed with the treated outdoor air as such. Indeed, in one form of the invention, it is envisaged that treated outdoor air may be mixed with untreated return air, after which sensible cooling may be carried out on the mixed air stream (treated outdoor air and untreated return air) to thereafter produce conditioned space supply air. References to "juxtaposition" are of course not to be construed as geometric limitations on the physical location or arrangement of any devices used in the system of the present invention.

In a preferred form, the configuration of the outdoor air latent heat cooling process section and the return air sensible heat cooling process section is such that the two processes are carried out on their respective air streams prior to mixing, the mixing means thus being capable of mixing the processed outdoor air with the processed return air to form conditioned space supply air.

Ideally, the heat exchange medium for the sensible cooling heat exchanger is passed in series with the dehumidification heat exchanger. This series configuration reduces the temperature differential, which increases the flow rate through the dehumidification heat exchanger, thereby increasing the heat exchange efficiency and effectiveness thereof to operate at higher equipment dew points to enable the chiller to operate at higher saturated suction temperatures. Then, preferably, the second section of the series circuit, i.e. the sensible heat cooling heat exchanger, utilizes the remaining cooling power. In addition, the reduced temperature differential increases the flow rate through the sensible cooling heat exchanger, thereby increasing the efficiency of the heat exchanger operating at higher temperatures and its effectiveness.

The air conditioning system of the present invention also preferably includes a demand driven primary heat exchange medium set point and a demand driven secondary heat exchange flow rate. In this regard, it can be appreciated that the energy required to produce the cooling medium at the lower saturated suction temperature is higher than the energy required to produce the cooling medium at the higher saturated suction temperature. The increase in saturated suction temperature required for a heat exchanger operating at higher efficiency allows the saturated suction temperature of the cooling medium to be increased, thereby reducing the energy required to produce the cooling effect.

As described above, the outdoor air latent heat cooling process section includes a combined pre-cooling and heat recovery heat exchanger. Reference to "combining" the pre-cooling and heat recovery heat exchangers refers to matching the amount of heat transferred from the pre-cooling heat exchanger to the heat recovery heat exchanger. In practice, the two heat exchangers are interdependent by a heat exchange fluid. Furthermore, the heat exchange fluid cooled by the heat recovery heat exchanger is transferred to a pre-cooling heat exchanger, which then pre-cools the air stream with the cooled heat exchange fluid. Ideally, the warm heat exchange fluid then flows back to the heat recovery heat exchanger to be cooled again. In this respect, the flow processes are complementary and adjusted as required.

In a first embodiment of the present invention, the improved air conditioning system desirably extends the Shaw system described above to use up to 100% outdoor air beyond normal air-conditioned space requirements (up to 25% outdoor air), possibly eliminating the use of a return air heat exchanger altogether.

This first embodiment preferably utilizes an outdoor air latent heat cooling process section comprising a single heat exchanger for dehumidification cooling and two heat exchangers for heat recovery to provide separation from the saturation curve without re-heating and thus provide energy improvement. In particular, the outdoor air latent heat cooling treatment section preferably includes a heat recovery pre-cooling heat exchanger, a chilled water dehumidification heat exchanger, and an additional heat recovery heat exchanger. In this embodiment, the first stage of cooling is provided by a heat recovery pre-cooling heat exchanger (sub-cooled energy transfer).

In this embodiment, the energy required for dehumidification also cools the outdoor air stream, preferably in a sensible manner. Ideally, this energy is transferred by using a closed loop heat recovery circuit to pre-cool the dehumidified air stream so that the energy used to dehumidify the outdoor air stream can be recovered by the heat recovery heat exchanger. Preferably, this heat exchanger is connected to the chilled water system by a heat recovery water circuit filled with connections, and said energy is transferred by a pump to a heat recovery pre-cooling heat exchanger. In this regard, the amount of energy transferred will generally be determined by the conditioning space sensible heat load requirements, and the energy transfer rate will generally dictate the separation temperature decoupled from the saturation curve, thereby providing a variable sensible heat ratio that would otherwise be obtained by the reheating of the additional heat source.

This first embodiment preferably also utilizes return air sensible heat to cool or heat the process section, which process section includes any one or more of a chilled water heat exchanger, a condensed water heat recovery heat exchanger, and/or a heated water heat exchanger. Ideally, then, condensate water can be drawn from the cooling tower to provide heating (if needed) to maintain conditioned space dry bulb conditions.

In this embodiment, the chilled water heat exchanger may provide sensible cooling to the conditioned space that could not otherwise be provided by the outdoor air dehumidification stream being delivered at or near the saturation curve. The chilled water heat exchanger is preferably connected in series to a chilled water dehumidification heat exchanger of the outdoor air latent heat cooling process section.

The water heating heat exchanger may then provide additional heating capacity if the condensate water system is unable to provide sufficient heating of the conditioned space.

Of course, after the above-described separation process of outdoor air and return air, the two air streams are preferably mixed to provide a single supply air stream to be delivered into the space to be conditioned.

In this preferred construction aspect of the ductwork of the first embodiment, it is preferred that the ductwork is configured as described above in combination with a series flow for the dehumidification heat exchanger to the sensible heat exchanger. Preferably, the two ductwork circuits incorporate a three-way bypass configuration to divert flow from either or both heat exchangers. Ideally, the circuit incorporates a flow meter to measure chilled water flow rate, and also includes temperature sensors to measure incoming chilled water temperature, interstage chilled water temperature, and outgoing chilled water temperature.

Preferably, the heat recovery pipework circuit also incorporates a heat transfer pump to transfer energy from the heat recovery pre-cooling heat exchanger to the further heat recovery heat exchanger, and a flow meter to measure the water flow rate. Ideally, such a circuit includes temperature sensors to measure the entering and leaving temperatures.

Furthermore, the condensed water piping system circuit preferably also incorporates a two-way control valve to regulate heating capacity, and also incorporates a flow sensor and temperature sensors that measure the entering and exiting temperatures. Furthermore, the heating water piping circuit preferably also incorporates a two-way or three-way control valve as well as a flow meter for measuring the flow of heating water and temperature sensors for measuring the incoming and outgoing water temperatures.

In a second embodiment of the invention, the principles of the first embodiment are extended to correspond to the requirements of a variable air volume system. Ideally, this second embodiment achieves the lowest supply air temperature that achieves dehumidification of the conditioned space, thereby reducing the amount of supply air required to compensate for the heat load demand of the conditioned space at the highest chilled water temperature at which the load demand of the conditioned space can be achieved. Thus, the second embodiment reduces the amount of supply air needed to adequately achieve single dry bulb control and overall acceptable controlled absolute humidity.

The outdoor air latent heat cooling process section in the second embodiment again preferably comprises a single heat exchanger for dehumidification cooling and two heat exchangers for heat recovery, so as to provide separation from the saturation curve without re-heating and thus provide energy improvement. These heat exchangers are preferably constructed in the same manner as described above with respect to the first embodiment. However, in this second embodiment, it is preferable to further include a damper that adjusts the amount of conditioned space air that can be returned to mix with the outdoor air stream, and a damper that allows excess conditioned space air to escape to the atmosphere. When the outdoor air temperature is suitable for sensible cooling, the two dampers operate inductively to increase the outdoor air flow, thereby providing additional outdoor air to meet the space sensible cooling load.

In this second embodiment, the outdoor air itself is of course a suitable medium to meet the cooling needs of the conditioned space when the ambient air conditions are below the desired conditioned space dry bulb temperature and dew point. In response to providing cooling, the bypass adjustment is opened to provide additional air through the outdoor air heat exchanger. The supply air fan speed is then increased to provide additional airflow and thus additional cooling.

For the return air sensible cooling process section of the second embodiment, the return air flow preferably incorporates a return air fan responsive to the demand of the warmest thermal zone. The return air stream preferably incorporates one or more of a condensate water heat recovery heat exchanger, a chilled water heat exchanger, a heated water heat exchanger, a return air fan, and/or an overflowed air damper. In this embodiment, condensed water will preferably be drawn from the cooling tower to provide heating to maintain conditioned space dry bulb conditions.

The chilled water heat exchanger of the return air sensible cooling treatment stage preferably provides sensible cooling to the conditioned space that could not otherwise be provided by dehumidified outdoor air delivered at or near the saturation curve. The chilled water heat exchanger is preferably connected in series to a chilled water dehumidification heat exchanger of the outdoor air latent heat cooling process section.

In a preferred form of this second embodiment, a return air fan coupled to the variable speed drive will adjust the amount of return air for recirculation to achieve sufficient sensible cooling or to provide overflowed (or exhaust) air. Further, during the outdoor air cooling mode, the spill air damper will open whenever there is excessive conditioned space pressurization.

Of course, after the above-described separation process of outdoor air and return air, it is preferable to mix the two air streams to provide a single supply air stream to be delivered to the space to be conditioned, as is the case with the first embodiment described above.

In terms of the preferred configuration of the ductwork circuit for this second embodiment, the ductwork will again preferably be configured to incorporate a series flow for the dehumidification heat exchanger to the sensible heat exchanger. Both ductwork circuits desirably incorporate a three-way bypass configuration to divert flow from either or both heat exchangers, and a flow meter to measure chilled water flow rate. Ideally, the circuit includes temperature sensors to measure the incoming chilled water temperature, the inter-stage chilled water temperature, and the outgoing chilled water temperature.

The heat recovery pipework circuit is again preferably combined with a transfer heat pump to transfer energy from the heat recovery pre-cooling heat exchanger to the second heat recovery heat exchanger, and is also preferably combined with a flow meter to measure the water flow rate. The circuit also preferably includes temperature sensors to measure the entering and exiting temperatures. Furthermore, the condensed water pipework circuit again preferably incorporates a two-way control valve to regulate the heating capacity, and a flow sensor and temperature sensors for measuring the entering and leaving temperatures. Furthermore, the heating water ductwork circuit is again preferably also combined with a two-way or three-way control valve, and with a temperature sensor for measuring the heating water flow meter and for measuring the incoming and outgoing water temperatures.

Turning to a general description of a third embodiment of the present invention, the third embodiment is a low dew point control process that extends the Shaw system beyond normal air-conditioned space requirements. The air conditioning system of the third embodiment again comprises an outdoor air latent heat cooling process section and a return air sensible heat cooling process section, but works with four dehumidification cooling steps including two heat recovery steps and one sensible cooling step, thereby providing energy improvement.

The outdoor air latent heat cooling process stage of this third embodiment preferably includes a brine heat recovery pre-cooling heat exchanger, a first stage chilled water dehumidification heat exchanger, a second stage brine dehumidification heat exchanger, and an additional brine heat recovery heat exchanger. Thus, the first stage of cooling in the third embodiment is preferably provided by a brine heat recovery pre-cooling heat exchanger, and the energy required for dehumidification pre-cools the outdoor air stream in a sensible manner. This energy is in turn transferred by using a closed loop heat recovery circuit to pre-cool the outdoor air stream.

In this embodiment, the first stage of dehumidification is preferably provided by chilled water. This chilled water is produced with a high coefficient of performance. The second stage of dehumidification is then preferably provided by a low temperature brine heat exchanger, with brine produced at a lower coefficient of performance compared to chilled water. Furthermore, the energy for dehumidifying the outdoor air stream is recovered by a heat recovery heat exchanger connected by a heat recovery water (brine) loop and a pump to a brine heat recovery pre-cooling heat exchanger.

Unlike the first and second embodiments, the return air stream combines both sensible cooling and sensible heating. The return air sensible cooling treatment stage of the third embodiment preferably comprises one or more of a condensate water heat recovery heat exchanger, a chilled water heat exchanger and a heated water heat exchanger. In this regard, condensate water is again drawn from the cooling tower to provide heating to maintain conditioned space dry bulb conditions. Additionally, where the heat exchanger is connected in series to the first stage chilled water dehumidification heat exchanger, the chilled water heat exchanger provides sensible cooling to the conditioned space.

Of course, after the above-described separation process of outdoor air and return air, it is preferable to mix the two air streams to provide a single supply air stream to be delivered to the space to be conditioned.

In terms of the preferred configuration of the ductwork circuit for this third embodiment, the ductwork circuit will again preferably be configured to incorporate a series flow for the dehumidification heat exchanger to the sensible heat exchanger in the same manner as described above.

In terms of the piping of the brine loop, the brine piping will preferably incorporate a two-way or three-way valve to control the dehumidification process. Ideally, the piping system incorporates a flow meter to measure the brine flow rate. Preferably the duct system also incorporates temperature sensors to measure the entry and exit temperatures.

Preferably the heat recovery pipework circuit also incorporates a transfer heat pump to transfer energy from the brine energy heat recovery pre-cooling heat exchanger to the heat recovery pre-cooling heat exchanger and a flow meter to measure the brine flow rate. This circuit preferably includes temperature sensors to measure the entering and leaving temperatures. This heat recovery pipe system is preferably connected to a brine pipe system to provide a heat exchange medium usable at low temperatures.

Furthermore, the condensed water piping circuit preferably incorporates a two-way control valve to regulate heating capacity, and a flow sensor and temperature sensors for measuring the entering and exiting temperatures. Furthermore, the heating water conduit system again preferably further comprises a two-way or three-way control valve, a flow meter for measuring the flow of heating water and temperature sensors for measuring the incoming and outgoing water temperatures.

The invention also provides a method of controlling the improved air conditioning system. The control method preferably includes the use of various inputs (among other things depending on the nature of the embodiments of the invention), including:

adjusting space dry bulb and relative humidity input;

outdoor air dry bulb and relative humidity input; and

an outdoor air flow input and a heat exchange medium flow input.

Preferably, the control method further comprises using various strategies (again, depending on the nature of the embodiments of the invention, among various things), including:

an outdoor air dehumidification strategy;

a return air sensible cooling strategy;

a heat recovery cooling strategy;

an outdoor air free cooling strategy;

a heat exchange medium delivery temperature reset strategy; and

an intersegment heat exchange medium selection strategy.

In terms of these strategies, they can be summarized in a very general sense as outlined in the following paragraphs.

The outdoor air dehumidification strategy preferably incorporates on-demand control of the outdoor air dehumidification heat exchanger and the heat exchange medium (chilled water) control valve.

The return air sensible cooling strategy preferably incorporates on-demand control of the return air sensible cooling heat exchanger and chilled water control valve along with a return air fan.

The heat recovery cooling strategy preferably incorporates on-demand control of the outdoor air pre-cooling heat exchanger, the heat recovery heat exchanger, and the guest-return circuit recirculation pump.

The outdoor air free cooling strategy preferably incorporates on-demand control of the conditioned space supply air fan, the return air fan and the outdoor air bypass damper.

The heat exchange medium delivery temperature reset strategy preferably incorporates on-demand control of the heat exchange medium (chilled water) delivery temperature reset.

The interstage heat exchange medium selection strategy preferably incorporates demand control over a heat exchange medium (such as chilled water) delivery temperature setpoint and a subcooled heat exchange medium (such as brine) delivery temperature setpoint.

In a preferred control methodology aspect to the first and second embodiments of the present invention, dual heat exchanger dehumidification, such as that utilized by the present invention, preferably uses one heat exchanger (such as a chilled water heat exchanger) in the outdoor air stream to provide latent heat cooling to achieve upper limit humidity control, and a second heat exchanger (such as a second chilled water heat exchanger) in the return air stream to provide additional sensible heat cooling to meet conditioned space dry bulb conditions. Therefore, sensible dehumidification heat transfer employs two heat exchangers collocated with an outdoor air dehumidification heat exchanger to regulate the amount of sensible cooling provided as part of the dehumidification process. Sensible cooling required to suppress the outdoor air stream to achieve dehumidification is preferably recovered by a circulation pump and an additional heat exchanger in a closed loop and passed to a pre-cooling heat exchanger in the outdoor air stream.

In the case where such a conditioned space requires a large amount of outdoor air (according to the first embodiment of the present invention), then, the control system manages the conditioned space state using controlled items, as follows:

the outdoor air dehumidification heat exchanger provides the required latent heat cooling;

the return air heat exchanger provides additional sensible cooling in addition to that provided by the dehumidification process; and

when the dehumidification process provides more sensible cooling than is required to condition the space, the heat recovery system transfers the sensible cooling remaining after dehumidification (saturation separation) to the cooling required to start the dehumidification process.

In a second embodiment, the variable volume box additionally serves to accommodate the requirements of two or more thermal zones in the conditioned space. Where the first requirement of all embodiments of the invention is to provide sufficient air circulation in the conditioned space to assist comfort conditions, the second requirement (and hence that satisfied by the second embodiment) is to provide supply air control to meet the change in regional heat load.

In this regard, when the ambient air has the ability to provide cooling to the conditioned space, the introduction of additional outdoor air will be conditioned to meet the conditioned space load, which may be accomplished by preferably using a bypass damper (as described above). In one form, a simple fan operating in response to a conditioned space load may act as a bypass damper to introduce additional outdoor air and maintain conditioned space conditions. In fact, the return air fan is then operable to obtain a difference between the supply air and the return air which is equal to the minimum required outdoor air quantity. Note that in this case, ideally, the return air would spill (vent) to the outside via the spill air damper.

In the case where such an air handling cooling apparatus is coupled to a plurality of sub-area cooling conditioning devices for delivering air to a variable air volume box (VAV) to manage a conditioned space (according to a second embodiment of the invention), then the control system uses the controlled items to manage the conditioned space conditions as follows:

changing the amount of outdoor air to meet a conditioned space dry bulb condition when the outdoor air dry bulb temperature and absolute humidity level are less than a desired conditioned space condition;

the outdoor air dehumidification heat exchanger provides sensible cooling to meet overall conditioned space requirements;

when the outdoor air dehumidification process provides insufficient sensible cooling to meet the conditioned space sensible cooling requirements, a return air fan is used with the return air heat exchanger to provide additional sensible cooling; and

when the dehumidification process provides more sensible cooling than is required to condition the space, the heat recovery system transfers the remaining sensible cooling after dehumidification (saturation separation) to the cooling required to start the dehumidification process.

In a preferred control method aspect of the third embodiment of the present invention, it is preferred to use a chilled water (as the primary heat exchange medium) heat exchanger and a brine (as the secondary heat exchange medium, or sub-cooled heat exchange medium) heat exchanger in the outdoor air stream to provide latent heat cooling to achieve upper limit humidity control. As with the first and second embodiments, the chilled water heat exchanger may therefore also be arranged in the return air stream to provide additional sensible cooling to meet the conditioned space dry bulb conditions.

In the case where such a conditioned space requires low absolute humidity (according to a third embodiment of the present invention), the control system will manage the conditioned space conditions using the controlled items as follows:

the first stage outdoor air dehumidification heat exchanger provides an initial dehumidification process to meet the conditioned space latent heat cooling requirements (this stage will preferably use the cold energy produced by refrigeration equipment with a high coefficient of performance (energy conversion efficiency));

the second stage outdoor air dehumidification heat exchanger provides a final dehumidification process to meet the conditioned space latent heat cooling requirements (this stage preferably uses refrigeration generated by refrigeration equipment having a coefficient of performance (energy conversion efficiency) less than that of the first stage dehumidification process refrigeration equipment);

the return air heat exchanger provides additional sensible cooling in addition to that provided by the dehumidification process;

when the sensible cooling provided by the dehumidification process is more than that required to condition the space, the heat recovery system transfers the sensible cooling remaining after dehumidification (saturation separation) to the cooling required to start the dehumidification process; and

supplemental heating may be provided by a higher energy source when the thermal potential of the recovered heat is insufficient (heat may be transferred from the heat of the refrigeration plant's exhaust (condensed water) or from a conventional fuel-fired system).

For all embodiments of the invention, the control system preferably uses proportional integral (P + L) control theory to provide a variable output to the controlled element to achieve near set point conditions in the conditioned space. All of the components of the apparatus preferably incorporate a variable drive to respond to a varying input signal.

Drawings

Having briefly described the general concepts associated with the present invention, three preferred embodiments of an improved air conditioning system according to the present invention will now be described. It should be understood, however, that the following description does not limit the generality of the above description.

In the drawings:

FIG. 1a is a flow chart of a first embodiment of an air conditioning system according to the present invention;

figure 1b is a psychrometric chart of the first embodiment shown in figure 1 a;

FIG. 2a is a flow chart of a second embodiment of an air conditioning system according to the present invention;

figure 2b is a psychrometric chart of the second embodiment shown in figure 2 a;

FIG. 3a is a flow chart of a third embodiment of an air conditioning system according to the present invention; and is

Figure 3b is a psychrometric chart of the third embodiment shown in figure 3 a.

Detailed Description

As noted above, in a first embodiment of the present invention, the improved air conditioning system of the present invention extends the Shaw system described above ideally to use up to 100% outdoor air over normal air-conditioned space requirements (up to 25% outdoor air), potentially eliminating the use of a return air heat exchanger altogether.

This first embodiment is illustrated by the flow diagram of figure 1a and the psychrometric chart of figure 1 b. For ease of understanding, the following description will first provide a general overview of the flow diagram of FIG. 1a, followed by a more detailed description of the different elements of the flow diagram (in the tables). Next, a brief description of the psychrometric chart of fig. 1b will be provided.

In summary, illustrated in the flow diagram of fig. 1a is an air conditioning system in which return air a from a conditioned space is subjected to a psychrometric process separately from outdoor air B (for ventilation) to obtain independent control of latent and sensible cooling. After the return air a and the outdoor air B are separately processed, the two air streams are then mixed to provide a single conditioned space supply air stream W to be delivered to the space to be conditioned.

The cooling process for the return air stream a is mainly sensible cooling, which takes place in the return air sensible cooling process section, which in this embodiment is represented by a heat exchanger H placed in the return air stream a.

The cooling process for the outdoor air stream B is mainly latent heat cooling, which is performed in an outdoor air latent heat cooling process section, which is represented in this embodiment by heat exchangers D, E and F placed in the outdoor air stream B. The first heat exchanger D pre-cools the outdoor air stream B using the recovered energy, reduces the dry bulb temperature of the air stream, and begins the dehumidification process. The second heat exchanger E dehumidifies the outdoor air stream B to an absolute humidity level that will achieve the desired relative humidity level in the conditioned space. The third heat exchanger F recovers sensible heat not needed to meet the sensible cooling load of the conditioned space. The result of this third stage of heat exchange is that the outdoor air stream B separates from the saturation curve. In this respect, the separation amount is regulated by a heat transfer pump I connecting the first heat exchanger D and the third heat exchanger F.

A main heat exchange medium (chilled water in this embodiment) is used to maximize the heat exchange efficiency. The cold chilled water inlet stream is used to provide the drive potential for the outdoor air second heat exchanger E (which in this embodiment is referred to as the dehumidification heat exchanger) and then the warm heat exchange medium passes to the heat exchanger H in the return air a path, which is referred to as the sensible heat cooling heat exchanger.

Prior to entering the air conditioning system, the temperature of the chilled water is adjusted as required by the current conditions in the conditioned space. For example, when maximum flow conditions are set for the heat exchanger and conditions in the conditioned space require additional dehumidification or sensible cooling, the initial temperature of the chilled water is adjusted down to obtain additional heat exchange, resulting in the conditioned space dry bulb and relative humidity requirements being met.

Finally, with reference to fig. 1a, and before providing a detailed description of each of the elements shown in fig. 1a, it will be understood that sensible heating for a conditioned space (if needed) is obtained by adding an additional heat exchanger in the return air stream a or the outdoor air stream B. In fig. 1a, such a further heat exchanger G is shown in the outdoor air stream B downstream of the outdoor air latent heat cooling treatment stage. In this embodiment, it can be seen that no latent heat heating is provided, as no such additional heat exchanger is provided in the return air stream a.

The following table provides a more detailed illustration of the various elements shown in the flow chart of FIG. 1 a:

A	return air (sensible cooling) flow typically, air recirculated from the conditioned space will be used to act as a medium to provide sensible cooling to the conditioned space.
		B	Outdoor air (dehumidified) flow typically, the air provided for ventilation of the space will serve as the medium used to provide latent cooling to the conditioned space.
C	The air that is delivered by the supply air stream to the conditioned space will be cooled to compensate for the heat load in the conditioned space. Depending on the ambient environment and the variability of the heat inflow and outflow of the conditioned space, the heat load of the space will require varying rates and amounts of sensible and latent cooling.
		D	The outdoor air stream pre-cools heat exchanger outdoor air stream B across heat exchanger D. The heat recovery cooling medium (L to K) passes through the heat exchanger D. The flow direction is counter-current: the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The outdoor air stream B releases heat to the heat recovery cooling medium. The outdoor air stream B will obtain sensible cooling and, depending on the temperature of the cooling medium stream, latent cooling may also be obtained.
E	Outdoor air stream desiccant heat exchanger outdoor air stream B passes over heat exchanger E. The cooling medium (M to N) passes through the heat exchanger E. The flow direction is counter-current: the warmer air flow being cooled by the warmer cooling medium
			The cooler air stream, however, is cooled by the cooler media stream. The outdoor air flow B releases heat to the cooling medium. The outdoor air stream B will primarily obtain latent heat cooling, although some sensible cooling will also be obtained.
F	Outdoor air flow heat recoveryThe heat recovery exchanger outdoor air flow B passes over the heat exchanger F. The heat recovery heating medium (K to L) passes through a heat exchanger F. The flow direction is counter-current: the warmer air stream is heated by the warmer heating medium stream and the cooler air stream is heated by the cooler medium stream. The outdoor air flow B absorbs heat from the heat recovery heating medium. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.
		G	The outdoor air stream sensible heats the heat exchanger outdoor air stream B across heat exchanger G. The heating medium (V to U) passes through a heat exchanger F. The flow direction is counter-current: the warmer air stream is heated by the warmer heating medium stream and the cooler air stream is heated by the cooler medium stream. The outdoor air flow B absorbs heat from the heating medium. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.

H	The return air stream sensible cooling heat exchanger the return air stream a passes over the heat exchanger H. The cooling medium (N to Q) passes through the heat exchanger H. The flow direction is counter-current: the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The return air flow a gives up heat to the cooling medium. The return air stream a will obtain sensible cooling and, depending on the temperature of the cooling medium stream, latent cooling may also be obtained.
		I	Heat transfer Pump Heat Pump I produces a flow through a Heat recovery Medium conduit Circuit (K and L) and two Heat exchangers (D and F). The sequence of flow through the heat recovery conduit loop is as follows: the flow generated by the heat transfer pump I passes through the conduit K, through the heat exchanger F, through the conduit L, and then through the heat exchanger D, back to the heat transfer pump I.
J	Feed and expansion pipe J connects the heat recovery piping circuit (K and L) to the cooling medium circuit M. The connection fills the heat recovery pipe with heat exchange medium from the cooling medium circuit M
			And (4) a loop. This connection allows for temperature-induced expansion and contraction in the heat recovery circuits (K and L).
K	Warm heat recovery tube the warm heat recovery tube transfers warm heat recovery medium from heat exchanger D to heat exchanger F.
		L	Cool heat recovery tubes transfer cool heat recovery medium from heat exchanger F to heat exchanger D.
M	Cold cooling medium pipe the cold cooling medium pipe transfers cold cooling medium from a cold generator (a freezer as shown by reference numeral 6, although some pipes are not shown) to the outdoor air stream dehumidifying heat exchanger E.
		N	Intersegment cooling medium pipe the intersegment cooling medium pipe transfers the cool cooling medium from the dehumidifying heat exchanger E to the sensible heat cooling heat exchanger H or to the return pipe S leading to the cold generator (freezer) 6.
O	Sensible cooling heat exchanger control valve O regulates the flow of cool heat exchange medium N through sensible cooling heat exchanger H. The increase in the flow of the cool heat exchange cooling medium increases the amount of heat exchange obtained by the sensible heat cooling heat exchanger H. The return air flow a will get sensible cooling due to the cool cooling medium flow and latent cooling will also be obtained depending on the temperature and flow rate of the cooling medium flow.

P	Dehumidification heat exchanger control valve the dehumidification cooling heat exchanger control valve P regulates the flow of cold heat exchange medium M through the dehumidification heat exchanger E. The increase in the flow of the cold heat-exchange cooling medium increases the amount of heat exchange obtained by the dehumidifying heat exchanger E. The outdoor air flow B will get latent heat cooling due to the cold cooling medium flow. Sensible cooling will also be obtained at a rate determined by the dehumidification process. In the case where there is no dehumidification demand but there is a sensible cooling demand, the dehumidification cooling heat exchanger control valve P will also be required to regulate the flow of the cold heat exchange medium M. Cold heat
			The increase in the flow of the exchange cooling medium increases the amount of heat exchange obtained by the dehumidifying heat exchanger E. Due to the cold cooling medium flow, the outdoor air stream B will get sensible cooling. Latent cooling may also be obtained depending on the temperature of the cooling medium flow.
Q	Warm cooling medium pipe warm cooling mediumThe pipe Q transfers warm cooling medium from the heat exchanger H back to the cold generator (freezer) 6.
		R	The cooling medium flow meter R measures the flow rate in the return cooling medium pipe S.
S	Reflux cooling medium pipe the reflux cooling medium pipe S transfers the mixed reflux cooling medium back to the cold generator (freezer) 6. The cooling media that have been used in the dehumidification heat exchanger E and the sensible heat cooling heat exchanger H flow together and then return to the cold generator (freezer) 6.
		T	Dehumidification air flow sensible heating heat exchanger control valve the outdoor air flow sensible heating heat exchanger control valve T regulates the flow of the hot heat exchange medium V through the sensible heating heat exchanger G. The increase in the flow of the hot heat-exchange heating medium increases the amount of heat exchange obtained by the sensible heat heating heat exchanger G. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.
U	Heat heating medium pipe the heat heating medium pipe transfers the hot heating medium from the heat exchanger G to the outdoor air stream dehumidifying heat exchanger E via a heat generator (not shown).
		V	Warm heating medium pipe warm reflux heating medium pipe V transfers warm heating medium from outdoor air stream dehumidification heat exchanger E back to the heat generator.
W	Conditioned space supply air the conditioned space supply air W is an outdoor air stream B (dehumidified air stream) and a return air stream a(sensible cooling air stream). Conditioned space supply air flow Wfrom train

Referring to the graph of fig. 1b, the enthalpy-wetting process is as follows: the first heat exchanger D precools the outdoor air B; the second heat exchanger E dehumidifies the outdoor air B using chilled water; and the third heat exchanger F transfers energy to the first heat exchanger D for pre-cooling. This enables the outdoor air stream B to be sufficiently dehumidified with the sensible cooling ratio reduced. As can be seen, a separation from the saturation curve is obtained. The separation is obtained by regulating the heat transfer from the first heat exchanger D to the third heat exchanger F.

By summarizing the first embodiment of fig. 1a and 1b, and as described above, a separate air path is used to obtain the enthalpy wetting scheme. As used by the Shaw system, where the outdoor air stream is dehumidified prior to mixing, the first embodiment of the present invention uses this same Shaw methodology but extends to four heat transfer processes. Note this, and as will be appreciated from the above description, the use of heat recovery allows for variability in the dehumidification process to provide separation from the saturation curve, which can be adjusted to meet the conditions of the conditioned space with minimal or no need for reheating.

Turning now to a second embodiment of the invention, and again as described above, the principles of the first embodiment extend to respond to the requirements of a variable air volume system. This second embodiment desirably achieves the lowest supply air temperature at which conditioned space dehumidification is achieved, thus reducing the amount of supply air required to compensate for conditioned space heat load demands at the chilled water temperature at which conditioned space load demands can be highest. Thus, the second embodiment reduces the amount of supplied air sufficient to achieve single dry bulb control and overall acceptable controlled absolute humidity.

This second embodiment is illustrated by the flow diagram of figure 2a and the psychrometric chart of figure 2 b. For ease of understanding, the following description will first provide an overview of the flow chart of fig. 2a, and then a more detailed description of the different elements of the flow chart (in the table). A brief description of the psychrometric chart of figure 2b will then be provided.

Shown in the flow chart of fig. 2a is an air conditioning system that provides a conditioned space supply air flow W to a plurality of variable volume area boxes (EEa, EEb, etc.). The sensible heat transfer is regulated by individual zone control. This latent cooling is regulated by the general conditions of the conditioned space.

As in the case of the first embodiment of fig. 1a and 1B, the outdoor air B (for ventilation) is treated separately from the return air a for enthalpy and humidity to obtain independent control of latent and sensible cooling. After this separate treatment, the two treated air streams are mixed to provide a single conditioned space supply air stream W to be delivered to the space to be conditioned.

The cooling process for the return air stream a is mainly sensible cooling, which is performed in a return air sensible cooling process section represented by a heat exchanger H placed in the return air stream a. The required sensible cooling is achieved by adjusting the return air volume. As the sensible heat load increases, the amount of return air also increases.

Further, the cooling process for the outdoor air stream B is mainly latent heat cooling performed in the outdoor air latent heat cooling process section represented by the heat exchangers D, E, and F placed in the outdoor air stream B. The first heat exchanger D pre-cools the outdoor air B using the recovered energy, reduces the dry bulb temperature and starts the dehumidification process. The second heat exchanger E dehumidifies the outdoor air B to an absolute humidity level that achieves a desired relative humidity level in the conditioned space. The third heat exchanger F recovers sensible heat not needed to meet the sensible cooling load of the conditioned space. The result of the third stage of heat exchange is that the outdoor air stream B separates from the saturation curve. The amount of separation is regulated by a heat transfer pump I connecting the first heat exchanger D and the third heat exchanger F.

The main heat exchange medium (again in this case chilled water) is used again to maximize heat exchanger efficiency. Thus, the cold incoming flow is used to provide the drive potential for the second heat exchanger E (outdoor air dehumidification heat exchanger) and then the warmer water is passed to the heat exchanger H of the return air stream a, i.e. the return air sensible cooling heat exchanger.

When the outdoor conditions are themselves adapted to provide sensible cooling and dehumidification, the return air "bypass" damper CC can be tuned to close to introduce additional outdoor air to meet the sensible cooling requirements of any zone present. When additional cooling is required, conditioned space supply air W is increased. The excess pressurization provided by this additional outdoor air is relieved from the conditioned space by opening the ambient air decompression damper BB and adjusting the speed of the return air fan AA.

The temperature of the heat exchange medium (chilled water) entering the system is again regulated as required by the conditions of the conditioned space. When maximum flow conditions have been set for the heat exchanger and additional dehumidification or sensible cooling is required to condition the space, the delivery temperature of the chilled water is adjusted down to obtain additional heat exchange, which results in meeting the conditioned space dry bulb and overall relative humidity requirements.

Finally, and as in the first embodiment of fig. 1a and 1B, sensible heating for the conditioned space in this second embodiment may be obtained by adding an additional heat exchanger (shown as heat exchanger G in outdoor air stream B in fig. 2 a) in the return air stream a or outdoor air stream B. This embodiment does not provide latent heat heating.

The following table provides a more detailed illustration of the various elements shown in the flow chart of fig. 2 a:

A	return air (sensible cooling) flow typically, air recirculated from the conditioned space will be used to act as a medium to provide sensible cooling to the conditioned space.
		B	Outdoor air (dehumidified) flow typically, the air provided for ventilation of the space will serve as the medium used to provide latent cooling to the conditioned space.
C	The air that is delivered by the supply air stream to the conditioned space will be cooled to compensate for the heat load in the conditioned space. Depending on the ambient environment and the variability of the heat inflow and outflow of the conditioned space, the heat load of the space will require varying rates and amounts of sensible and latent cooling.
		D	Outdoor air flow precooling heat exchanger outdoor airStream B passes over heat exchanger D. The heat recovery cooling medium (L to K) passes through the heat exchanger D. The flow direction is counter-current: the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The outdoor air stream B releases heat to the heat recovery cooling medium. The outdoor air stream B will obtain sensible cooling and, depending on the temperature of the cooling medium stream, latent cooling may also be obtained.
E	Outdoor air stream desiccant heat exchanger outdoor air stream B passes over heat exchanger E. The cooling medium (M to N) passes through the heat exchanger E. The flow direction is counter-current: the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The outdoor air flow B releases heat to the cooling medium. The outdoor air stream B will primarily obtain latent heat cooling, although some sensible cooling will also be obtained.
		F	The outdoor air stream heat recovery heat exchanger outdoor air stream B passes over the heat exchanger F. The heat recovery heating medium (K to L) passes through a heat exchanger F. The flow direction is counter-current: the warmer air stream is heated by the warmer heating medium stream and the cooler air stream is heated by the cooler medium stream. The outdoor air flow B absorbs heat from the heat recovery heating medium. The outdoor air stream B will gain sensible heat heating and will not gain
	Latent heat exchange is obtained.
		G	The outdoor air stream heats heat exchanger the outdoor air stream B across the heat exchanger G. The heating medium (V to U) passes through a heat exchanger F. The flow direction is counter-current: the warmer air stream is heated by the warmer heating medium stream and the cooler air stream is heated by the cooler medium stream. The outdoor air flow B absorbs heat from the heating medium. Outdoor air flow B willSensible heating is achieved and latent heat exchange will not be achieved.

H	The return air stream sensible cooling heat exchanger the return air stream a passes over the heat exchanger H. The cooling medium (N to Q) passes through the heat exchanger H. The flow direction is counter-current: the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The return air flow a gives up heat to the cooling medium. The return air stream a will obtain sensible cooling and, depending on the temperature of the cooling medium stream, latent cooling may also be obtained.
		I	The heat transfer pump I generates a flow through the heat recovery medium conduit loop (K and L) and the two heat exchangers D and F. The sequence of flow through the heat recovery conduit loop is as follows: the flow generated by the heat transfer pump I passes through the conduit K, through the heat exchanger F, through the conduit L, and then through the heat exchanger D, back to the heat transfer pump I.
J	Feed and expansion pipe J connects the heat recovery pipe circuit (K and L) to the cooling medium circuit M. This connection fills the heat recovery tube loop with heat exchange medium from M. This connection allows for temperature-induced expansion and contraction in the heat recovery circuits (K and L).
		K	Warm Heat recovery tube the warm heat recovery tube transfers warm heat recovery medium from Heat exchanger D to Heat exchangerAnd (F) a device.
L	Cool heat recovery tubes transfer cool heat recovery medium from heat exchanger F to heat exchanger D.
		M	Cold cooling medium pipe the cold cooling medium pipe transfers cold cooling medium from the cold generator (freezer) to the outdoor air stream dehumidifying heat exchanger E.
N	Intersegment cooling medium pipe an intersegment cooling medium pipe transfers the cool cooling medium from the dehumidifying heat exchanger E to the sensible heat cooling heat exchanger H or to a return pipe S leading to a cold generator (freezer) DD.
		O	Sensible cooling heat exchanger control valve O regulates the flow of cool heat exchange medium N through sensible cooling heat exchanger H. The increase in the flow of the cool heat exchange cooling medium increases the amount of heat exchange obtained by the sensible heat cooling heat exchanger H. The return air flow a will get sensible cooling due to the cool cooling medium flow and latent cooling will also be obtained depending on the temperature and flow rate of the cooling medium flow.

P	Dehumidification heat exchanger control valve dehumidification cooling heat exchanger control valve P regulates the cold through dehumidification heat exchanger EThe flow rate of the heat exchange medium M. The increase in the flow of the cold heat-exchange cooling medium increases the amount of heat exchange obtained by the dehumidifying heat exchanger E. The outdoor air flow B will get latent heat cooling due to the cold cooling medium flow. Sensible cooling will also be obtained at a rate determined by the dehumidification process. In the case where there is no dehumidification demand but there is a sensible cooling demand, the dehumidification cooling heat exchanger control valve P will also be required to regulate the flow of the cold heat exchange medium M. The increase in the flow of the cold heat-exchange cooling medium increases the amount of heat exchange obtained by the dehumidifying heat exchanger E. Due to the cold cooling medium flow, the outdoor air stream B will get sensible cooling. Latent cooling may also be obtained depending on the temperature of the cooling medium flow.
		Q	Warm cooling medium pipe the warm cooling medium pipe Q transfers the warm cooling medium from the heat exchanger H back to the cold generator (freezer) DD.
R	Cooling medium flowmeter
			The cooling medium flow meter R measures the flow rate in the return cooling medium pipe S.
S	Reflux cooling medium pipe the reflux cooling medium pipe S transfers the mixed reflux cooling medium back to the cold generator (freezer) DD. The cooling media that have been used in the dehumidification heat exchanger E and the sensible heat cooling heat exchanger H flow together and then return to the cold generator (freezer) DD.
		T	Outdoor air flow sensible heating heat exchanger control valve the outdoor air flow sensible heating heat exchanger control valve T regulates the flow of the hot heat exchange medium V through the sensible heating heat exchanger G. The increase in the flow of the hot heat-exchange heating medium increases the amount of heat exchange obtained by the sensible heat heating heat exchanger G. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.
U	Heat heating medium pipe the heat heating medium pipe transfers the hot heating medium from the heat exchanger G to the outdoor air stream dehumidifying heat exchanger E via a heat generator (not shown)
		V	Warm heating medium pipe warm reflux heating medium pipe V transfers warm heating medium from outdoor air stream dehumidification heat exchanger E back to the heat generator.
W	Conditioned space supply air the conditioned space supply air W is a mixture of an outdoor air stream B (dehumidified air stream) and a return air stream a (sensible cooling air stream). The conditioned space supply air stream W delivers sensible and latent cooling and sensible heating potentials from the series and parallel heat exchangers D, E, F, G and H to compensate for the conditioned space and ventilation air stream heat loads to provide target dry bulb and relative humidity conditions.

X	Treated outdoor air stream the treated outdoor air stream X delivers sensible and latent cooling and sensible heating potentials from the series of heat exchangers D, E, F and G.
		Y	Treated return air stream
	The treated return air stream Y is cooled by sensible and latent heat transfer from the heat exchanger G.
		Z	Supply air fan the supply air fan Z delivers air from the heat exchanger process to the variable volume tanks 'EEa', 'EEb', etc. The supply air fan Z is driven by a motor equipped with a variable speed transmission. The speed of the supply air fan Z varies in response to the dry bulb temperature control air flow management sequence.
AA	Return air fan the return air fan AA delivers air from the conditioned space through a sensible heat exchange process to mix with the treated outdoor air stream X or release to the ambient environment. The return air fan AA is driven by a motor equipped with a variable speed transmission. The speed of the return air fan AA is varied in response to the dry bulb temperature control air flow management sequence.
		BB	Ambient reduced pressure air damper BB will allow the return air to be released to the ambient. The ambient decompression air damper BB position will be set in response to the dry bulb temperature control air flow management sequence.
CC	Return air damper the return air damper CC will allow the treated return air flow Y to mix with the treated outdoor air flow X. The return air damper CC position will be set in response to the dry bulb temperature control airflow management sequence.
		DD	Cold cooling medium generator (freezer) the cold cooling medium generator (freezer) DD is a mechanical device that removes the thermal energy absorbed by the heat exchangers E and H.
EEaEEb……	Zoned variable volume tanks the delivery of conditioned space supply air W is regulated by the zoned variable volume tanks EEa, EEb, etc. to compensate for the zoned space heat load. The conditioned space supply air stream W delivers sensible and latent cooling and sensible heating potentials from the series and parallel heat exchangers D, E, F, G and H to compensate for the combined zonal conditioning space and ventilation air stream heat load

For the second embodiment and its psychrometric chart shown in fig. 2b, the psychrometric process is as follows: the first heat exchanger D pre-cools the outdoor air; the second heat exchanger E dehumidifies the outdoor air using chilled water; and the third heat exchanger F transfers energy to the first heat exchanger D for pre-cooling. The cooling process for the return air stream a is mainly sensible cooling, which is performed in a return air sensible cooling process section represented by a heat exchanger H placed in the return air stream a.

By summarizing the second embodiment of fig. 2a and 2b, the enthalpy wetting scheme is again obtained using a separate air path. While the Shaw system uses outdoor air flow to dehumidify prior to mixing, this second embodiment of the present invention uses the Shaw methodology, which again extends to four heat transfer processes. The use of heat recovery allows for variability in the separation from the saturation curve that can be adjusted to meet the condition of the conditioned space with minimal or no need for reheating. When additional sensible cooling is required, the supply air flow is increased and ideally regulated by the load.

Turning now to the third embodiment of the present invention, and again as described above, the third embodiment is a low dew point control process that extends the Shaw system beyond normal air-conditioned space requirements. The air conditioning system of the third embodiment again comprises an outdoor air latent heat cooling process section and a return air sensible heat cooling process section, but these sections are completed with four dehumidification cooling steps including two heat recovery steps and one sensible cooling step to provide energy improvement.

This third embodiment is illustrated by the flow diagram of figure 3a and the psychrometric chart of figure 3 b. For ease of understanding, the following description will first provide an overview of the flow chart of fig. 3a, and then a more detailed description of the different elements of the flow chart (in the table). A brief description of the psychrometric chart of figure 3b will then be provided.

Shown in fig. 3a is an air conditioning system which again relies on the use of outdoor air B for ventilation to perform an enthalpy process separately from return air a for independent control of latent and sensible cooling, this third embodiment being able to successfully use the high proportion of outdoor air B required by some dedicated buildings such as manufacturing laboratories.

Furthermore, the cooling process for the outdoor air stream B is mainly latent heat cooling, which is performed in the outdoor air latent heat cooling process section. In the outdoor air latent heat cooling process section, the outdoor air B is processed four times by the heat exchangers (D, E, Z and F), which constitute an additional heat exchange step in the outdoor air latent heat cooling process section compared to the first and second embodiments.

The first heat exchanger D pre-cools the outdoor air B using the recovered energy, reduces the dry bulb temperature and starts the dehumidification process. The second heat exchanger E dehumidifies the outdoor air B to an intermediate absolute humidity level. The third heat exchanger Z utilizes a relatively cold heat exchange medium (a sub-cooled medium such as brine) to provide additional dehumidification to achieve an absolute humidity level that achieves a desired relative humidity level in the conditioned space. Thus, this third heat exchanger Z provides an air conditioning system of an embodiment of the present invention with the ability to handle lower conditioned space absolute humidity requirements.

The fourth heat exchanger F recovers sensible heat not needed to meet the sensible cooling load of the conditioned space. The result of this fourth stage of heat exchange is also that the air flow separates from the saturation curve. The separation amount is regulated by a heat transfer pump I connecting the first exchanger D to the fourth exchanger F.

The cooling process for the return air stream a is also primarily sensible cooling, which is carried out in the return air sensible cooling treatment section. In the return air sensible cooling treatment stage, and in the event that additional sensible cooling is required, an additional heat exchanger H is placed in the return air stream.

A main heat exchange medium (which is also chilled water in this third embodiment) is used to maximize heat exchanger efficiency. The cold inlet stream is used to provide the driving potential for the second heat exchanger E in the outdoor air latent heat cooling process section and subsequently, the warm media is passed to the further heat exchanger H of the return air sensible heat cooling process section.

The delivery temperature of the chilled water is also adjusted as needed to adjust the conditions of the space to achieve optimum performance between the main chiller generator (for chilled water) and the subcooled chiller generator (for brine). When maximum flow conditions have been set for the heat exchanger and additional dehumidification or sensible cooling is required to condition the conditioned space, the delivery temperature of the chilled water is adjusted down to obtain additional heat exchange, which results in meeting the conditioned space dry bulb and relative humidity requirements. In the event additional dehumidification is required, the delivery temperature of the brine is set to achieve a conditioned space absolute humidity set point.

Sensible heating of the conditioned space is obtained by adding a heat exchanger G in the return air stream a or the outdoor air stream B, shown in this embodiment (unlike the first and second embodiments) in the path of the return air stream a. Heating may also be provided by a condensate water heat exchanger. Latent heat heating is also not provided in this third embodiment.

After the separation process of the outdoor air B and the return air a, the two air streams may be mixed to provide a single air stream W to be delivered to the space to be conditioned.

The following table provides a more detailed illustration of the various elements shown in the flow chart of FIG. 3 a:

A	return air (sensible cooling) flow typically, air recirculated from the conditioned space will be used to act as a medium to provide sensible cooling to the conditioned space.
		B	Outdoor air (dehumidified) flow typically, the air provided for ventilation of the space will serve as the medium used to provide latent cooling to the conditioned space.
C	The air that is delivered by the supply air stream to the conditioned space will be cooled to compensate for the heat load in the conditioned space. Depending on the ambient environment and the variability of the heat inflow and outflow of the conditioned space, the heat load of the space will require varying rates and amounts of sensible and latent cooling.
		D	The outdoor air stream pre-cools heat exchanger outdoor air stream B across heat exchanger D. The heat recovery cooling medium (L to K) passes through the heat exchanger D. The flow direction is counter-current; the warmer air flow being formed by the warmer cooling medium
	Flow cooling, cooler air flowThe cool medium flow cools. The outdoor air stream B releases heat to the heat recovery cooling medium. The outdoor air stream B will obtain sensible cooling and, depending on the temperature of the cooling medium stream, latent cooling may also be obtained.

E	Outdoor air stream desiccant heat exchanger outdoor air stream B passes over heat exchanger E. The cooling medium (M to N) passes through the heat exchanger E. The flow direction is counter-current; the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The outdoor air flow B releases heat to the cooling medium. The outdoor air stream B will primarily obtain latent heat cooling, although some sensible cooling will also be obtained.
		F	The outdoor air stream heat recovery heat exchanger outdoor air stream B passes over the heat exchanger F. The heat recovery heating medium (K to L) passes through a heat exchanger F. The flow direction is counter-current; the warmer air stream is heated by the warmer heating medium stream and the cooler air stream is heated by the cooler medium stream. The outdoor air flow B absorbs heat from the heat recovery heating medium. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.
G	The outdoor air stream heats heat exchanger the outdoor air stream B across the heat exchanger G. The heating medium (V to U) passes through a heat exchanger F. The flow direction is counter-current; the warmer air stream is heated by the warmer heating medium stream and the cooler air stream is heated by the cooler medium stream. Outdoor air flow B absorbs heat from the heating medium. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.
		H	The return air stream sensible cooling heat exchanger the return air stream a passes over the heat exchanger H. The cooling medium (N to Q) passes through the heat exchanger H. The flow direction is counter-current; the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The return air flow a gives up heat to the cooling medium. The return air stream a will obtain sensible cooling and, depending on the temperature of the cooling medium stream, latent cooling may also be obtained.
I	The heat transfer pump I generates heat through the heat recovery medium pipe loop (K and L) and two heat exchangers
			D and F. The sequence of flow through the heat recovery conduit loop is as follows: the flow generated by the heat transfer pump I passes through the conduit K, through the heat exchanger F, through the conduit L, and then through the heat exchanger D, back to the heat transfer pump I.
J	Feed and expansion pipe J connects the heat recovery pipe circuit (K and L) to the cooling medium circuit M. This connection fills the heat recovery pipe circuit with heat exchange medium from the cooling medium circuit M. This connection also allows for temperature-induced expansion and contraction in the heat recovery circuits (K and L).
		K	Warm heat recovery tube the warm heat recovery tube transfers warm heat recovery medium from heat exchanger D to heat exchanger F.
L	Cooling and heatingThe take-up cold heat recovery pipe transfers the cold heat recovery medium from heat exchanger F to heat exchanger D.

M	Cold cooling medium pipe the cold cooling medium pipe transfers cold cooling medium from the cold generator (freezer) to the outdoor air stream dehumidifying heat exchanger E.
		N	Intersegment cooling medium pipe the intersegment cooling medium pipe transfers the cool cooling medium from the dehumidifying heat exchanger E to the sensible heat cooling heat exchanger H or to the return pipe to the cold generator (freezer) 6.
O	Sensible cooling heat exchanger control valve O regulates the flow of cool heat exchange medium N through sensible cooling heat exchanger H. The increase in the flow of the cool heat exchange cooling medium increases the amount of heat exchange obtained by the sensible heat cooling heat exchanger H. The return air flow a will get sensible cooling due to the cool cooling medium flow and latent cooling will also be obtained depending on the temperature and flow rate of the cooling medium flow.
		P	Dehumidification heat exchanger control valve the dehumidification cooling heat exchanger control valve P regulates the cold heat exchange through the dehumidification heat exchanger E
	Exchange mediumM, of the flow rate. The increase in the flow of the cold heat-exchange cooling medium increases the amount of heat exchange obtained by the dehumidifying heat exchanger E. The outdoor air flow B will get latent heat cooling due to the cold cooling medium flow. Sensible cooling will also be obtained at a rate determined by the dehumidification process. In the case where there is no dehumidification demand but there is a sensible cooling demand, the dehumidification cooling heat exchanger control valve P will also be required to regulate the flow of the cold heat exchange medium M. The increase in the flow of the cold heat exchange cooling medium increases the amount of heat exchange achieved by the dehumidifying heat exchanger. Due to the cold cooling medium flow, the outdoor air stream B will get sensible cooling. Latent cooling may also be obtained depending on the temperature of the cooling medium flow.
		Q	Warm cooling medium pipe the warm cooling medium pipe Q transfers the warm cooling medium from the heat exchanger H back to the cold generator (freezer) 6.
R	The cooling medium flow meter R measures the flow rate in the return cooling medium pipe S.
		S	Reflux cooling medium pipe the reflux cooling medium pipe S transfers the mixed reflux cooling medium back to the cold generator (freezer) 6. The cooling media that have been used in the dehumidification heat exchanger E and the sensible heat cooling heat exchanger H flow together and then return to the cold generator (freezer) 6.
T	Outdoor air flow sensible heat exchanger control valve the outdoor air flow sensible heat exchanger control valve T regulates the flow of the hot heat exchange medium V through the sensible heat exchanger G. The increase in the flow of the hot heat-exchange heating medium increases the amount of heat exchange obtained by the sensible heat heating heat exchanger G. The outdoor air stream B will get sensible heat heating and will not get latent heat exchange.

U	Heat heating medium pipe the heat heating medium pipe transfers the hot heating medium from the heat exchanger G to the outdoor air stream dehumidifying heat exchanger E via a heat generator (not shown)
		V	Warm heating medium pipe warm reflux heating medium pipe V dehumidifies and exchanges warm heating medium from outdoor air flow
	The inverter E transmits back to the heat generator.
		W	Conditioned space supply air the conditioned space supply air W is a mixture of the outdoor air stream B and the return air stream a. The conditioned space supply air stream W delivers sensible and latent cooling and sensible heating potentials from the series and parallel heat exchangers D, E, F, G and H to compensate for the conditioned space and ventilation air stream heat loads to provide target dry bulb and relative humidity conditions.
X	Treated outdoor air stream the treated outdoor air stream X delivers sensible and latent cooling and sensible heating potentials from the series of heat exchangers D, E, F and G.
		Y	Treated return air stream the treated return air stream Y delivers sensible and latent cooling from heat exchanger G.
Z	The outdoor air flows through the dehumidification heat exchanger outdoor air stream B across the heat exchanger Z. The subcooled medium (BB to CC) is passed through heat exchanger ZZ. The flow direction is counter-current; the warmer air stream is cooled by the warmer cooling medium stream and the cooler air stream is cooled by the cooler medium stream. The outdoor air flow B releases heat to the cooling medium. The outdoor air stream B will primarily obtain latent heat cooling, although some sensible cooling will also be obtained.
		AA	Super strong dehumidification heat exchanger control valve super strong dehumidification cooling heat exchanger control valve AA regulates the flow of cold heat exchange medium BB through dehumidification heat exchanger E. The increase in the flow of the supercooled heat-exchange cooling medium increases the amount of heat exchange achieved by the super strong heat-removal heat exchanger Z. The outdoor air stream B will obtain latent heat cooling due to the sub-cooled cooling medium flow. Sensible cooling will also be obtained at a rate determined by the dehumidification process.
BB	Cold subcooling medium pipe the cold subcooling medium pipe BB transfers the subcooled cooling medium from the subcooling generator (brine chiller) to the outdoor air stream super dehumidification heat exchanger Z.

Referring to the third embodiment and its psychrometric chart shown in fig. 3b, the psychrometric process is as follows: the outdoor air dehumidification pre-cooling heat exchanger D pre-cools the outdoor air B; the outdoor air dehumidifying heat exchanger E dehumidifies the outdoor air B using chilled water (M to N); the outdoor air super strong dehumidification heat exchanger Z (which is a salt water heat exchanger) further dehumidifies the outdoor air B to obtain the required relative humidity of the conditioned space; and the outdoor-air heat-recovery heat exchanger F transfers energy to the first heat exchanger D to pre-cool the outdoor air B, thereby starting the dehumidification process. The cooling process for the return air stream a is primarily sensible cooling, which is carried out in the return air sensible cooling treatment section. In the return air sensible cooling process section, and in the event that the air conditioning system requires additional sensible cooling, an additional heat exchanger G is placed in the return air stream a.

By summarizing the third embodiment of fig. 3a and 3b, a humidity regime is again obtained using a separate air path. While the Shaw system uses the outdoor air stream to dehumidify prior to mixing, the third embodiment uses the Shaw methodology that extends to four heat transfer processes (similar to the three heat transfer processes of the first and second embodiments, but with the addition of additional heat transfer processes). The advantage is to provide a high demand enthalpy wet process with a lower efficiency energy source and to re-use this higher efficiency energy source for creating pre-cooling of the final dehumidification process. The subcooling, which is typically reheated with a primary heating source (as is the case with conventional design theory), is replaced by heat recovery and reject heat (condensate) used in the refrigeration cycle cooling process, thus eliminating the primary heating requirement and reducing energy consumption.

In conclusion, it must be understood that there may be other variations and modifications to the configurations described herein which also fall within the scope of the present invention.

Claims (19)

1. An air conditioning system capable of treating a conditioned space by treating outdoor air from outside the conditioned space and return air from inside the conditioned space and mixing the outdoor air with the return air to form supply air for the conditioned space, the air conditioning system comprising:

an outdoor air latent heat cooling process section configured to provide an air stream in juxtaposition with a return air sensible cooling process section; and

means for mixing outdoor air with return air, the means for mixing outdoor air with return air to form conditioned space supply air,

wherein the outdoor air latent heat cooling treatment section comprises at least a dehumidification heat exchanger, a combined pre-cooling and heat recovery heat exchanger, and a heat transfer pump, and the return air sensible heat cooling treatment section comprises at least a sensible heat cooling heat exchanger.

2. An air conditioning system according to claim 1, wherein the configuration of the outdoor air latent cooling process section and the return air sensible cooling process section is such that both processes are carried out on their respective air streams prior to mixing, the means for mixing outdoor air with return air thereby being capable of mixing treated outdoor air with treated return air to form the conditioned space supply air.

3. The air conditioning system of claim 1 wherein the heat exchange medium for the sensible cooling heat exchanger is passed in series with a dehumidification heat exchanger.

4. The air conditioning system of claim 1, wherein the outdoor air latent heat cooling process section includes at least a dehumidification heat exchanger, a combined pre-cooling and heat recovery heat exchanger, and a heat transfer pump to deliver a dehumidified air stream separated from a saturation curve variable dry bulb.

5. The air conditioning system of claim 1, comprising at least one variable return air bypass damper, a variable supply air velocity controller, and a variable return air velocity controller to meet a plurality of variable sensible load requirements to maintain an overall conditioned space relative humidity requirement.

6. The air conditioning system of claim 1, wherein the outdoor air latent heat cooling process section comprises: three dehumidification heat exchangers capable of meeting low absolute humidity requirements by utilizing two main cold generators; a heat recovery pre-cooling heat exchanger to transfer energy from the low absolute dehumidification process to pre-cooling; and an additional heat recovery heat exchanger to reheat heat from any one of the cold generators of the discharged condensed water system, if necessary.

7. The air conditioning system of claim 6, wherein the stream temperature of each cold generator is adjusted to minimize energy consumption.

8. The air conditioning system of claim 1, wherein the system comprises: a first chilled water heat exchanger in the outdoor air stream to provide latent heat cooling for upper limit humidity control; and a second chilled water heat exchanger in the return air stream to provide additional sensible cooling to meet conditioned space dry bulb conditions.

9. The air conditioning system of claim 8 wherein the system further comprises a sensible dehumidification heat transfer section comprising two heat exchangers collocated to the dehumidification heat exchanger of the outdoor air latent heat cooling process section to regulate the amount of sensible cooling provided as part of a dehumidification process.

10. The air conditioning system of claim 8 wherein sensible cooling required to suppress the outdoor air to achieve dehumidification is recovered by an additional heat exchanger and a circulation pump in a closed loop and transferred to a pre-cooling heat exchanger of the combined pre-cooling and heat recovery heat exchanger.

11. The air conditioning system of any of claims 8 to 10, wherein a control system manages the conditioned space conditions as follows:

the dehumidification heat exchanger of the outdoor air latent heat cooling treatment section provides the required latent heat cooling;

the sensible cooling heat exchanger of the return air sensible cooling treatment section provides additional sensible cooling in addition to the sensible cooling provided by the dehumidification process; and is

When the dehumidification process provides more sensible cooling than is required to condition the space, a heat recovery system transfers the remaining sensible cooling after dehumidification to the cooling required to start the dehumidification process.

12. The air conditioning system of claim 1, wherein a variable volume box is used to meet the requirements of two or more heat sensitive zones in the conditioned space.

13. The air conditioning system of claim 12, wherein additional outdoor air is conditioned to meet conditioned space loads by using a bypass damper when the outdoor air has the capacity to provide cooling to the conditioned space.

14. The air conditioning system of claim 13, wherein a return air fan operating in response to a conditioned space load operates in conjunction with a bypass damper to introduce additional return air and maintain conditioned space conditions.

15. The air conditioning system of claim 14, wherein a return air fan operates to obtain a difference between the supply air and the return air that is equal to a minimum required minimum outdoor air amount.

16. The air conditioning system of claim 15, comprising a plurality of sub-areas for delivering air to a plurality of Variable Air Volume (VAV) boxes to manage the conditioned space, a control system managing the conditioned space conditions as follows:

changing the amount of outdoor air to meet a conditioned space dry bulb condition when the outdoor air dry bulb temperature and absolute humidity level are less than a desired conditioned space condition;

the dehumidification heat exchanger of the outdoor air latent heat cooling process section provides latent heat cooling to meet the overall conditioned space requirements;

using the return air fan with the sensible cooling heat exchanger of the return air sensible cooling process section providing additional sensible cooling when the sensible cooling provided by the outdoor air latent cooling process section is insufficient to meet a conditioned space sensible cooling demand; and is

When the dehumidification process provides more sensible cooling than is required for the conditioned space, the heat recovery system transfers the sensible cooling remaining after dehumidification to the cooling required to start the dehumidification process.

17. An air conditioning system according to claim 1, comprising chilled water as a primary heat exchange medium, brine as a secondary heat exchange medium, and a chilled water heat exchanger and a brine heat exchanger located in the outdoor air stream to provide latent heat cooling to achieve upper limit humidity control.

18. An air conditioning system according to claim 17, including a further chilled water heat exchanger in the return air stream to provide additional sensible cooling to meet conditioned space dry bulb conditions.

19. The air conditioning system of claim 18, wherein in the event that the conditioned space requires low absolute humidity, a control system manages the conditioned space conditions as follows:

the first stage outdoor air dehumidification heat exchanger provides an initial dehumidification process using cold energy generated by refrigeration equipment having a high coefficient of performance to meet the conditioned space latent heat cooling requirements;

the second-stage outdoor air dehumidification heat exchanger provides a final dehumidification process by using cold energy generated by refrigeration equipment with a performance coefficient smaller than that of the first-stage dehumidification process refrigeration equipment so as to meet the latent heat cooling requirement of the conditioned space;

the return air heat exchanger provides additional sensible cooling in addition to that provided by the first stage dehumidification process and the second stage dehumidification process;

when the sensible cooling provided by the dehumidification process is more than that required by the conditioned space, the heat recovery system transfers the residual sensible cooling after dehumidification to the cooling required to start the dehumidification process; and is

Supplemental heating can be provided by a higher energy source when the thermal potential of the recovered heat is insufficient, heat being transferred from the heat of the exhaust of the refrigeration equipment or from a conventional fuel-fired system.