HK1133068B - De-gassing lubrication reclamation system - Google Patents

Description

Degassed lubricant recovery system

Technical Field

The present invention relates to vapor compression systems, and more particularly to vapor compression systems for use in "chiller" systems having a flooded evaporator and a generator vessel or still for separating lubricant from liquid refrigerant.

Background

Chillers used to cool extensive interior spaces such as airport terminals, shopping centers and office buildings include vapor compression systems which typically include a refrigeration loop and a lubrication loop. The refrigeration loop includes a condenser, an expansion device, an evaporator or chiller, and a compressor. The lubrication circuit also includes a compressor and is designed to provide lubricant to the compressor. As the refrigeration loop and the lubrication loop intersect in the compressor, the liquid refrigerant from the refrigeration loop and the lubricant from the lubrication loop are allowed to mix, thus creating a mixture of liquid refrigerant and lubricant. The mixture of lubricant and refrigerant collects in the evaporator where it can reduce the heat transfer capacity of the system without recovering the mixture. Since the viscosity of the refrigerant is much lower than that of the lubricant, the viscosity of the resulting lubricant and refrigerant mixture is much lower than necessary to adequately lubricate the compressor. Therefore, the lubricant and refrigerant mixture is not suitable for use as a lubricant upon recovery.

Therefore, known chillers incorporate a generator vessel or retort to address this problem. The still is actually a concentrator that operates to remove oily refrigerant from the evaporator and separate lubricant from liquid refrigerant. Conventional distillers accomplish this by boiling off the refrigerant with heat and leaving an oil-rich mixture of sufficiently high viscosity to be suitable for use as a lubricant. However, under certain pressure temperature conditions experienced by freezers, it can be difficult to obtain adequate lubricant viscosity using conventional heating methods. Moreover, even if sufficient lubricant viscosity is obtained by heating alone, achieving such viscosity often requires substantial heating, resulting in an undesirable reduction in chiller energy efficiency.

It would therefore be desirable to have a lubricant reclamation system that can be used to remove refrigerant from a lubricant and refrigerant mixture without the significant heat cost required by conventional systems.

Disclosure of Invention

The present invention relates to vapor compression systems for use in freezers. Such vapor compression systems include a lubricant recovery system or still that incorporates an ejector to reduce the pressure in the still. The ejector includes an inlet portion, an outlet portion, and a vent portion. The inlet portion, the outlet portion, and the vent portion are in fluid communication with one another. The still contains primarily a mixture of liquid refrigerant and lubricant. The vent portion of the eductor is located within a vent line connected to the still. The inlet portion of the ejector receives high pressure liquid or gas. As the high pressure fluid flows through the ejector, a low pressure is created in the vent portion, causing refrigerant vapor to flow from the still into the ejector through the vent portion.

The fluid flow into the inlet portion is at an input pressure and the fluid flowing into the vent portion is at a vent pressure. The flow from the inlet portion and the flow from the vent portion are combined within the ejector and discharged through the outlet portion at an output pressure that is between the input pressure and the vent pressure. The resulting reduction in pressure in the vent section is fluidly communicated to the vaporizer via the vent line. This causes a portion of the liquid refrigerant to evaporate from the still and flow into the vent line, through the vent portion, into the ejector and out through the outlet portion, and leaves the remaining lubricant-refrigerant mixture in the still at a higher viscosity.

In one embodiment, the ejector is also operated whenever the chiller is operating. In another embodiment, the ejector is operated intermittently, i.e. it is driven only when the suction pressure is in a range where it is difficult to obtain a sufficiently high lubricant viscosity in a conventional manner under certain pressure temperature conditions.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Drawings

FIG. 1 is a schematic diagram of a known vapor compression system including a refrigeration loop and a lubrication loop;

FIG. 1A is a schematic diagram of a known distiller incorporating a heating tube;

FIG. 2 is a schematic view of a vapor compression system including a refrigeration loop, a lubrication loop, and an embodiment of the present invention;

FIG. 3 is a schematic view of a vapor compression system including a refrigeration loop, a lubrication loop, and another embodiment of the present invention; and

fig. 4 is a detailed view of a distiller including an exemplary embodiment of the present invention.

Detailed Description

Fig. 1 is a schematic diagram of a known vapor compression system 10 including a refrigeration loop and a lubrication loop. The refrigeration loop includes an evaporator 12, a compressor 14, a condenser 16, and an expansion device 18. The lubrication circuit includes a compressor 14, an oil pump 20, and a still 22.

In the refrigeration loop, the evaporator 12 delivers gaseous refrigerant to the compressor 14, where the gaseous refrigerant is compressed. The compressed gaseous refrigerant is passed to the condenser 16 where it is cooled to a liquid phase in the condenser 16 and passed back to the evaporator 12 through the expansion valve 18. In the chiller system, heat exchange is performed between the evaporator 12 and the chiller 13, and the chiller 13 is shown in a broken line.

In the lubrication loop, an oil pump 20 supplies lubricant to the compressor 14 for lubrication. Since the compressor 14 is both part of the refrigeration loop and part of the lubrication loop, some of the refrigerant from the refrigeration loop mixes with lubricant from the lubrication loop in the compressor 14 to form a lubricant and refrigerant mixture. The presence of refrigerant in the lubricant is undesirable because the viscosity of the lubricant and refrigerant mixture is lower than the viscosity of the lubricant alone. Thus, the lubricant and refrigerant mixture is transferred to the still 22, and heat is introduced into the still 22 to boil off refrigerant from the lubricant and refrigerant mixture, thereby producing a liquid of increased viscosity. This can be done by incorporating an electric heater 24 in the vaporizer 22 and/or by heating with a hot refrigerant stream that is passed through isolated piping (not shown) that passes through the vaporizer 22. Further, an optional lubricant reservoir 26, shown in phantom, may be included in the lubrication loop.

However, under the pressure temperature conditions experienced by the vapor compression system 10, it is difficult to obtain sufficient lubricant viscosity with conventional heating methods. Furthermore, even if sufficient lubricant viscosity can be achieved by heating alone, achieving such viscosity requires a large amount of heat to be added to the vapor compression system 10, which results in an undesirable reduction in energy efficiency in the system.

Fig. 1A is a schematic diagram of a known vaporizer 22, such vaporizer 22 incorporating a heating tube 23 to supply heat to the vaporizer 22. The heated fluid flows through the heating tube 23 to introduce heat to the lubricant and refrigerant mixture in the still 22, the heating tube 23 extending through the still 22. The heated fluid may be either heated liquid received from condenser 16 (fig. 1) or heated gas received from compressor output line 47 (fig. 2). The heated fluid flows through a heating tube 23 located in the still 22 and returns to the evaporator 12 (fig. 1).

Fig. 2 is a schematic diagram of a vapor compression system 30 including a refrigeration loop, a lubrication loop, and an ejector according to an embodiment of the present invention. In the refrigeration loop, the evaporator 32 delivers refrigerant gas to the compressor 34, where the refrigerant gas is compressed. The compressed gaseous refrigerant is passed to a condenser 36 where it is cooled to a liquid phase in the condenser 36 and passed back to the evaporator 32 through an expansion valve 38. In the chiller system, heat is exchanged between the evaporator 32 and the chiller 33, and the chiller 33 is shown in a broken line.

In the lubrication loop, an oil pump 40 supplies lubricant to the compressor 34 for lubrication. As shown in the known vapor compression system 10 (fig. 1), since the compressor 34 is both part of the refrigeration loop and part of the lubrication loop, some of the refrigerant from the refrigeration loop mixes with lubricant from the lubrication loop in the compressor 34 to form a lubricant and refrigerant mixture. Thus, a still 42 is included to provide lubricant of increased viscosity by removing refrigerant from the lubricant and refrigerant mixture. In still 42, this hot refrigerant stream may be received from compressor output conduit 47 through heating tube 23 by incorporating an electric heater 43 in still 42 and/or by heating with the hot refrigerant stream, as shown in FIG. 1A, heating tube 23 isolated in still 42, or through other isolated conduits (not shown) that pass through still 42.

However, to increase the viscosity of the lubricant in still 42 without adding a significant amount of heat, ejector 44 is positioned in fluid communication with the refrigeration and lubrication loops. The ejector 44 may include, but is not limited to, an ejector pump or a supersonic nozzle. In this example, the ejector 44 operates during the same time period as the vapor compression system 30 operates. Alternatively, the ejector 44 may be operated intermittently, i.e., only when the pressure and temperature in the still 42 are within a range where it is difficult to obtain sufficient lubricant viscosity with conventional heating if the ejector 44 is not driven.

The injector 44 includes three ports: two input ports and one output port. A high pressure fluid, such as a liquid or gas, is introduced through the first input port 46 and passes through the ejector 44, creating a low pressure region downstream of the first input port 46. A second input port 50 is located near the low pressure region and is in fluid communication with the still 42 via the vent line 48.

In one exemplary system, the first input port 46 receives high pressure refrigerant gas from a high pressure gas drive line 52. The low pressure generated at the second input port 50 is fluidly communicated to the interior of the distiller 42 through the vent line 48. This reduction in pressure causes some of the liquid refrigerant from the lubricant-refrigerant mixture in the still 42 to evaporate and form a refrigerant gas. A second input port 50 receives refrigerant gas from the vent line 48 connected to the still 42. The fluid flows from the first and second input ports 46, 50 combine in the ejector 44 and flow at an output pressure into the ejector through an output port 54 to be discharged into a conduit 56. The output pressure is less than the input pressure of the fluid received into the first input port 46 and greater than the input pressure of the fluid received into the second input port 50.

As a result of the evaporation event, the liquid remaining in the still 42 is not diluted too much by the refrigerant, thus providing a more oil-rich (i.e., higher viscosity) liquid for use as a lubricant delivered to the pump 40. Thus, the use of the eductor 44 increases the viscosity of the lubricant without adding excessive heat. Furthermore, by incorporating an appropriately sized injector 44, no added heat is required at all to achieve adequate lubricant viscosity under certain operating conditions.

Optionally, a lubricant reservoir 58 (shown in phantom) may be included in the lubrication loop. If lubricant reservoir 58 is included, lubricant from still 42 may be further refined or filtered just prior to entering lubricant reservoir 58. The lubricant is then supplied from the lubricant reservoir 58 to the oil pump 40. A reservoir vent line 59 may also be included to connect the reservoir 58 to the vent line 48 to maintain the proper viscosity.

Fig. 3 is a schematic diagram of a vapor compression system 60 including a refrigeration loop, a lubrication loop, and an embodiment of the present invention. The vapor compression system 60 of fig. 3 is similar in layout and function to the vapor compression system 30 shown in fig. 2. Accordingly, similar devices are designated by reference numerals increased by a value of 30. However, in the lubrication loop shown in FIG. 3, the injectors 74 are driven by high pressure liquid, rather than the high pressure gas described in FIG. 2.

In fig. 3, a first input port 76 of the ejector 74 receives high pressure fluid from the condenser 66 through a high pressure fluid drive conduit 82. The low pressure generated at the second input port 80 is fluidly communicated to the interior of the still 72 through the vent line 78. This reduction in pressure causes some of the liquid refrigerant from the lubricant-refrigerant mixture in the still 72 to evaporate and form a refrigerant gas. A second input port 80 receives refrigerant gas from the vent line 78 connected to the still 72. The fluid flows from the first and second input ports 76, 80 combine in the ejector 74 and are discharged at an output pressure through an output port 84 into an ejector discharge line 86. The output pressure is less than the input pressure of the fluid received into the first input port 76 and greater than the input pressure of the fluid received into the second input port 80. As a result of the evaporation event, the liquid remaining in the still 72 is not diluted too much by the refrigerant, thus providing a more oil-rich (i.e., higher viscosity) liquid for use as a lubricant delivered to the pump 70.

Moreover, using high pressure liquid refrigerant to drive the ejector 74 may have several advantages over using high pressure refrigerant gas. For example, as shown in FIG. 3, when liquid refrigerant flow is required for another aspect of system operation, such as cooling the motor 85. The addition of the cooling function may be combined with the function of driving the ejector 74. Fluid discharged through the output port 84 of the ejector 74 flows through an ejector discharge line 86 into a motor 85 that drives the compressor 64 to provide cooling to the motor 85. As another advantage, the system 60 can accommodate higher flow rates of gas through the vent conduit 78 when a higher density liquid is used to drive the ejector 74. This allows a higher velocity refrigerant to evaporate from the lubricant-refrigerant mixture in the still 72.

FIG. 4 is a schematic diagram including a distiller in accordance with an exemplary embodiment of the present invention. Still 90 contains lubricant and refrigerant sludge and refrigerant gas. In this figure, the lubricant and refrigerant mixture enters the still 90 through an inlet conduit 92. As is known, the inlet conduit 92 is positioned relative to the evaporator (not shown) such that the connection of the inlet conduit 92 to the evaporator (not shown) is gravitationally below the lowest operating liquid level in the evaporator and above the maximum non-operating liquid level in the evaporator. Alternatively, if a shut-off valve (not shown) is used to prevent refrigerant from flowing into the inlet conduit 92 during periods of non-operation, the connection of the inlet conduit 92 to the evaporator (not shown) may be at a location that is both below the lowest operating liquid level and the maximum non-operating liquid level in the direction of gravity. An orifice or controlled regulating valve 93 may be located between the evaporator (not shown) and the still 90 in the inlet conduit 92. A controlled regulating valve 93 may be used to regulate the flow of lubricant and refrigerant within inlet line 92 and to vaporizer 90.

The inlet duct 92 is preferably flat-bottomed and may also include features such as barriers, ribs, dividers or deflectors to evenly distribute the flow and/or isolate the flow from leveling.

A first electric heater 94 may also optionally be mounted along the bottom edge of the inlet conduit 92, the first electric heater 94 introducing heat into the lubricant and refrigerant mixture causing some of the liquid refrigerant to evaporate. Second electric heater 96 may also be mounted at the bottom edge of distiller 90 or inserted into distiller 90 below the liquid level. The second electric heater may be used to introduce additional heat, causing more liquid refrigerant from the lubricant and refrigerant mixture to flash into a gas. If an electric heater 94 or 96 is used, the electric heater 94 or 96 may be intermittently adjusted or operated as desired.

Ejector 98 is connected to a vent line 100, and vent line 100 discharges refrigerant gas from vaporizer 90. The ejector 98 receives a high pressure fluid (e.g., high pressure refrigerant gas or high pressure liquid refrigerant) through an inlet conduit 102 and discharges a low pressure fluid (e.g., low pressure refrigerant gas or a low pressure mixture of refrigerant gas and liquid refrigerant) through an outlet conduit 104. As the fluid passes through the ejector 98, a pressure drop is created in the vent line 100. This pressure drop creates a pressure drop in still 90. This pressure drop causes some of the liquid refrigerant from the lubricant and refrigerant mixture in the still 90 to evaporate, thereby creating a fluid flow through the vent line 100 and into the ejector 98.

As a result of the evaporation event, the liquid remaining in still 90 provides a more oil-rich (i.e., higher viscosity) liquid to use as a lubricant without adding excessive heat. Furthermore, by incorporating an appropriately sized eductor 90, the addition of heat is not required at all to achieve sufficient lubricant viscosity under certain operating conditions, as sufficient lubricant viscosity can be achieved through pressure drop alone. Thus, under these operating conditions, the electric heaters 94 and 96 may not be required.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (19)

1. A lubricant reclamation system comprising:

a distiller; and

an ejector comprising an inlet portion, an outlet portion, and a vent portion, wherein the vent portion is located within a vent conduit in fluid communication with the distiller, the inlet portion, outlet portion, and vent portion are in fluid communication with one another, the inlet portion receives high pressure fluid, and the outlet portion discharges low pressure fluid.

2. The lubricant reclamation system of claim 1, wherein the fluid received through the inlet portion is a gas.

3. The lubricant reclamation system of claim 1, wherein the fluid received through the inlet portion is a liquid.

4. The lubricant reclamation system of claim 1, wherein the injector is a jet pump.

5. The lubricant reclamation system of claim 1, wherein the injector is a supersonic nozzle.

6. The lubricant reclamation system as recited in claim 1, further comprising at least one heating device.

7. The lubricant reclamation system of claim 6, wherein the at least one heating device is an electric heater.

8. The lubricant reclamation system as recited in claim 7, wherein the at least one electric heater is located proximate to the still.

9. The lubricant reclamation system of claim 6, wherein the at least one heating device comprises at least one tube through which hot fluid flows.

10. The lubricant reclamation system as recited in claim 9, wherein the at least one tube is located proximate to the still.

11. A vapor compression system comprising:

a condenser;

an expansion device;

an evaporator;

a compressor; and

a lubricant reclamation system comprising a still and an eductor, the eductor further comprising: an inlet portion; an outlet portion; and a vent portion, wherein the vent portion is located within a vent conduit in fluid communication with the still, the inlet portion, outlet portion, and vent portion are in fluid communication with each other, the inlet portion receives high pressure fluid from the condenser, and the outlet portion discharges low pressure fluid to the evaporator.

12. The vapor compression system as recited in claim 11, wherein the fluid received through the inlet portion is a gas.

13. The vapor compression system as recited in claim 11, wherein the fluid received through the inlet portion is a liquid.

14. The vapor compression system as recited in claim 11, further comprising at least one heating device.

15. The vapor compression system as recited in claim 14, wherein the at least one heating device is an electric heater.

16. The vapor compression system as recited in claim 14, wherein the at least one heating device includes at least one tube through which a hot fluid flows.

17. A method of removing refrigerant from a lubricant and refrigerant mixture by using the vapor compression system of claim 11.

18. The method of removing refrigerant from a lubricant-refrigerant mixture as set forth in claim 17, wherein the fluid received through said inlet portion is a liquid.

19. The method of removing refrigerant from a lubricant-refrigerant mixture as set forth in claim 17, wherein the fluid received through said inlet portion is a gas.