LOW CHARGE PACKAGED AMMONIA REFRIGERATION SYSTEM WITH EVAPORATIVE CONDENSER

Abstract

A packaged, pumped liquid, evaporative-condensing recirculating ammonia refrigeration system with charges of 10 lbs or less of refrigerant per ton of refrigeration capacity. The compressor and related components are situated inside the plenum of a standard evaporative condenser unit, and the evaporator is close coupled to the evaporative condenser. Prior art large receiver vessels may be replaced with a single or dual phase cyclonic separator also housed in the plenum of the evaporative condenser.

Claims

1. A refrigeration system comprising: a refrigerant evaporator coil, vapor/liquid separation structure connected to an outlet of said evaporator coil via refrigerant line configured to separate low pressure refrigerant vapor from low pressure refrigerant liquid; a refrigerant compressor connected to an outlet of said liquid-vapor separation device via refrigerant line and configured to compress refrigerant vapor from said vapor liquid separation structure; an evaporative refrigerant condenser connected to an outlet of said refrigerant compressor via refrigerant line and configured to condense refrigerant vapor produced in said compressor to refrigerant liquid, a high pressure-side expansion device connected to an outlet of said evaporative refrigerant condenser via refrigerant line and configured to reduce pressure of refrigerant liquid received from said evaporative refrigerant condenser; a collection vessel connected to an outlet of said high pressure-side expansion device via refrigerant line for receiving refrigerant liquid from said high pressure-side expansion device; a low pressure-side expansion device connected to an outlet of said collection vessel via refrigerant line and configured to reduce pressure of refrigerant liquid received from said collection vessel; refrigerant line connecting an outlet of said low pressure-side expansion device to an inlet of said vapor/liquid separation structure and configured to deliver refrigerant liquid to said separation structure; said vapor/liquid separation structure having a liquid outlet that is connected via refrigerant line to an inlet of said evaporator; wherein said vapor/liquid separation structure, said compressor, said high pressure side expansion device, said collection vessel, and said low pressure side expansion device are situated inside a plenum of said evaporative refrigerant condenser; and wherein said refrigerant is ammonia.

2. A refrigeration system according to claim 1, which requires less than six pounds of refrigerant per ton of refrigeration capacity.

3. A refrigeration system according to claim 1, wherein said evaporative condenser comprises a water distribution system located above a condenser coil, and said plenum is located beneath and adjacent to said condenser coil.

4. A refrigeration system according to claim 1, wherein said vapor/liquid separation structure comprises a cyclonic separator.

5. A refrigeration system according to claim 1, wherein said vapor/liquid separation structure comprises a recirculator vessel.

6. A refrigeration system according to claim 1, wherein said collection vessel comprises a cyclonic separator.

7. A refrigeration system according to claim 1, wherein said collection vessel comprises an economizer.

8. A refrigeration system according to claim 1, wherein said evaporator coil has internal enhancements to improve the flow of liquid/vapor therein and improve heat exchange and refrigerant charge.

9. A refrigeration system according to claim 1, wherein said condenser comprises coils having internal enhancements.

10. A refrigeration system according to claim 1, wherein said condenser comprises a microchannel heat exchanger.

11. A refrigeration system according to claim 1, further comprising a liquid to vapor mass ratio sensor situated inside refrigerant line connecting said evaporator coil and said vapor/liquid separation structure.

12. A refrigeration system according to claim 1, further comprising a liquid to vapor mass ratio sensor situated inside refrigerant line connecting said vapor/liquid separation structure and said compressor.

13. A refrigeration system according to claim 1, further comprising an oil separator vessel configured to separate compressor oil from refrigerant vapor received from said compressor.

14. A refrigeration system according to claim 1, which requires less than four pounds of refrigerant per ton of refrigeration capacity.

15. A refrigeration system according to claim 1, which requires less than two pounds of refrigerant per ton of refrigeration capacity.

16. A method for reducing the amount of refrigerant per ton of refrigeration capacity in a refrigeration system having an evaporator, liquid/vapor separator, a compressor, an evaporative condenser, and a collection vessel, said method comprising packaging said compressor, said liquid vapor separator and said collection vessel in a plenum of an evaporative condenser, connecting said evaporator to said evaporative condenser via refrigerant line, and filling said refrigerant system with ammonia refrigerant.

17. A method according to claim 16, wherein said evaporator is mounted in a pre-fabricated modular evaporator room.

18. A method according to claim 17, wherein said pre-fabricated modular evaporator room is installed adjacent to said evaporative condenser.

19. A method according to claim 16, wherein said evaporator is mounted in a refrigerated space directly beneath said evaporative condenser

Description

DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic of a refrigeration system according to an embodiment of the invention.

[0011] FIG. 2 is a blow-up of the upper left hand portion of FIG. 1.

[0012] FIG. 3 is a blow-up of the lower left hand portion of FIG. 1.

[0013] FIG. 4 is a blow-up of the lower right hand portion of FIG. 1.

[0014] FIG. 5 is a blow up of the upper right hand portion of FIG. 1.

[0015] FIG. 6 is a three dimensional perspective view of a combined evaporator module and a prepackaged modular machine room according to an embodiment of the invention.

[0016] FIG. 7 is a three dimensional perspective view of a combined evaporator module and a prepackaged modular machine room according to another embodiment of the invention.

[0017] FIG. 8 is a three dimensional perspective view of the inside of a pre-packaged modular machine room and condenser unit according to an embodiment of the invention.

[0018] FIG. 9 is a three dimensional perspective view of the inside of a pre-packaged modular machine room and condenser unit according to another embodiment of the invention.

[0019] FIG. 10 is a three dimensional perspective view of combined evaporator module and a prepackaged modular machine room according to another embodiment of the invention.

[0020] FIG. 11 shows three-dimensional perspective views of three different embodiments of combined evaporator module and a prepackaged modular machine room, in which the embodiment on the left includes a roof mounted air-cooled condenser system.

[0021] FIG. 12 shows a three-dimensional cut-away view of the inside of a pre-packaged modular machine room according to another embodiment of the invention.

[0022] FIG. 13 shows a three-dimensional cut-away view of the inside of a combined penthouse evaporator module and a prepackaged modular machine room.

[0023] FIG. 14 is a prior art evaporative condenser.

[0024] FIG. 15 shows a packaged ammonia evaporative-condensing chiller according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1 is a process and instrumentation diagram for a low charge packaged refrigeration system according to an embodiment of the invention. Blow-ups of the four quadrants of FIG. 1 are presented in FIGS. 2 through 5, respectively. The system includes evaporators 2a and 2b, including evaporator coils 4a and 4b, respectively, condenser 8, compressor 10, expansion devices 11a and 11b (which may be provided in the form of valves, metering orifices or other expansion devices), pump 16, liquid-vapor separation device 12, and economizer 14. According to one embodiment, liquid-vapor separation device 12 may be a recirculator vessel. According to other embodiments, liquid-vapor separation device 12 and economizer 14 may one or both provided in the form of single or dual phase cyclonic separators. The foregoing elements may be connected using standard refrigerant tubing in the manner shown in FIGS. 1-5. As used herein, the term connected to or connected via means connected directly or indirectly, unless otherwise stated. Optional defrost system 18 includes glycol tank 20, glycol pump 22, glycol condenser coils 24 and glycol coils 6a and 6b, also connected to one-another and the other element of the system using refrigerant tubing according to the arrangement shown in FIG. 1. According to other optional alternative embodiments, hot gas or electric defrost systems may be provided. An evaporator feed pump/recirculator 16 may also be provided to provide the additional energy necessary to force the liquid refrigerant through the evaporator heat exchanger.

[0026] According to the embodiment shown in FIGS. 1-5, low pressure liquid refrigerant (LPL) is supplied to the evaporator by pump 16 via expansion devices 11. The refrigerant accepts heat from the refrigerated space, leaves the evaporator as low pressure vapor (LPV) and liquid and is delivered to the liquid-vapor separation device 12 (which may optionally be a cyclonic separator) which separates the liquid from the vapor. Liquid refrigerant (LPL) is returned to the pump 16, and the vapor (LPV) is delivered to the compressor 10 which condenses the vapor and sends high pressure vapor (HPV) to the condenser 8 which compresses it to high pressure liquid (HPL). The high pressure liquid (HPL) is delivered to the economizer 14 which improves system efficiency by reducing the high pressure liquid (HPL) to intermediate pressure liquid IPL then delivers it to the liquid-vapor separation device 12, which supplies the pump 16 with low pressure liquid refrigerant (LPL), completing the refrigerant cycle. The glycol flow path (in the case of optional glycol defrost system) and compressor oil flow path is also shown in FIGS. 1-5, but need not be discussed in more detail here, other than to note that the present low charge packaged refrigeration system may optionally include full defrost and compressor oil recirculation sub-systems within the packaged system. FIGS. 1-5 also include numerous control, isolation, and safety valves, as well as temperature and pressure sensors (a.k.a. indicators or gages) for monitoring and control of the system. In addition, optional sensors 26a and 26b may be located downstream of said evaporators 2a and 2b, upstream of the inlet to the liquid-vapor separation device 12, to measure vapor/liquid ratio of refrigerant leaving the evaporators. According to alternative embodiments, optional sensor 26c may be located in the refrigerant line between the outlet of the liquid-vapor separation device 12 and the inlet to the compressor 10. Sensors 26a, 26b and 26c may be capacitance sensors of the type disclosed in U.S. Ser. Nos. 14/221,694 and 14/705,781, the disclosures of which are incorporated herein by reference, in their entirety. FIG. 6 shows an example of a combined penthouse evaporator module and a prepackaged modular machine room according to an embodiment of the invention. According to this embodiment, the evaporator is housed in the evaporator module, and the remaining components of the system shown in FIGS. 1-5 are housed in the machine room module. Various embodiments of condenser systems that may be employed according to the invention include evaporative condensers, with optional internally enhanced tubes, air cooled fin and tube heat exchangers with optional internal enhancements, air cooled microchannel heat exchangers, and water cooled heat exchangers. In the case of air cooled condenser systems, the condenser coils and fans may be mounted on top of the machine room module for a complete self-contained rooftop system. Other types of condenser systems may be located inside the machine room. According to this embodiment, the entire system is completely self-contained in two roof-top modules making it very easy for over-the-road transport to the install site, using e.g., flat bed permit load non-escort vehicles. The penthouse and machine room modules can be separated for shipping and/or for final placement, but according to a most preferred embodiment, the penthouse and machine room modules are mounted adjacent to one-another to maximize the reduction in refrigerant charge. According to a most preferred embodiment, the penthouse module and the machine room module are integrated into a single module, although the evaporator space is separated and insulated from the machine room space to comply with industry codes. FIGS. 7, 10 and 11 show other examples of adjacent penthouse evaporator modules and machine room modules.

[0027] FIGS. 8, 9 and 12 are three dimensional cutaway perspective views of the inside of a pre-packaged modular machine room and condenser unit according to an embodiment of the invention, in which all the elements of the low charge packaged refrigeration system are contained in an integrated unit, except the evaporator. As discussed herein, the evaporator may be housed in a penthouse module, or it may be suspended in the refrigerated space, preferably directly below the location of the machine room module. According to these embodiments, the evaporator is configured to directly cool air which is in or supplied to a refrigerated space.

[0028] According to alternative embodiments (e.g., in which end users to not wish refrigerated air to come into contact with ammonia-containing parts/tubing), the evaporator may be configured as a heat exchanger to cool a secondary non-volatile fluid, such as water or a water/glycol mixture, which secondary non-volatile fluid is used to cool the air in a refrigerated space. In such cases, the evaporator may be mounted inside the machine room.

[0029] FIG. 13 is a cutaway three-dimensional perspective view of the inside of a combined penthouse evaporator module and a prepackaged modular machine room.

[0030] The combination of features as described herein provides a very low charge refrigeration system compared to the prior art. Specifically, the present invention is configured to require less than six pounds of ammonia per ton of refrigeration capacity. According to a preferred embodiment, the present invention can require less than four pounds of ammonia per ton of refrigeration. And according to most preferred embodiments, the present invention can operate efficiently with less than two pounds per ton of refrigeration capacity. By comparison, prior art stick-built systems require 15-25 pounds of ammonia per ton of refrigeration, and prior art low charge systems require approximately 10 pounds per ton of refrigeration. Thus, for a 50 ton refrigeration system, prior art stick built systems require 750-1,250 pounds of ammonia, prior art low charge systems require approximately 500 pounds of ammonia, and the present invention requires less than 300 pounds of ammonia, and preferably less than 200 pounds of ammonia, and more preferably less than 100 pounds of ammonia, the report threshold for the EPA (assuming all of the ammonia in the system were to leak out. Indeed according to a 50 ton refrigeration system of the present invention, the entire amount of ammonia in the system could be discharged into the surrounding area without significant damage or harm to humans or the environment.

[0031] While the present invention has been described primarily in the context of refrigeration systems in which ammonia is the refrigerant, it is contemplated that this invention will have equal application for refrigeration systems using other natural refrigerants, including carbon dioxide.

[0032] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the concept of a packaged (one- or two-module integrated and compact system) low refrigerant charge (i.e., less than 10 lbs of refrigerant per ton of refrigeration capacity) refrigeration system are intended to be within the scope of the invention. Any variations from the specific embodiments described herein but which otherwise constitute a packaged, pumped liquid, recirculating refrigeration system with charges of 10 lbs or less of refrigerant per ton of refrigeration capacity should not be regarded as a departure from the spirit and scope of the invention set forth in the following claims.

[0033] FIG. 14 shows a prior art evaporative condenser unit marketed by Applicant, designated the ATC-E Evaporative Condenser. Housed within the four-sided metal housing 202 of the unit is a water distribution system 204 located above a coil 206 which in turn is located above a plenum 208. The plenum optionally contains fill. At the bottom of the plenum is a water basin 210 where water is collected and pumped to the water distribution system 204. On the top of the unit is an induced-draft fan 212 which pulls air from the outside through openings in the side of the unit adjacent the plenum, up through the coil and out the top of the unit. Process fluid is circulated through the coil and is cooled by evaporative effect of the water and air passing over the coil.

[0034] FIG. 15 shows an example of an integrated evaporative condensing ammonia chiller package according to an embodiment of the invention, in which the elements of the chiller are packaged in the plenum 118 of an evaporative condenser unit. Examples of evaporative condenser units that may be used or modified for the present invention include, but are not limited to Applicant Evapco, Inc.'s ATC-E models of evaporative condenser. High pressure vapor enters the condensing coil 108 at inlet 110 and exits the coil at outlet 112. Water distribution system 114 sprays water over coil 108, which then falls through fill 116 situated in plenum 118 to collect in sump 120 at the bottom of the unit where it is pumped back through water distribution system. Induced draft fan 122 is located adjacent the water distribution system at the top of the unit and draws air into the system through air inlets located above the water distribution system, and through the side of the unit adjacent fill 116. Air entering the coil 108 exits the coil through the side via drift eliminators 124 and exits through the fan 122 at the top of the unit. Air entering the plenum 108 through the lower side of the unit likewise exits the unit at the top through the fan 122. According to this embodiment, the chiller components of the system shown in FIGS. 1-5 are housed in the plenum of the evaporative condenser component. The evaporator may be located in the refrigerated space or in an evaporator module adjacent the integrated evaporative condensing chiller package.