CN106796073B

CN106796073B - Low charge packaged refrigeration system

Info

Publication number: CN106796073B
Application number: CN201580036543.1A
Authority: CN
Inventors: 库尔特·利本多费; 格雷戈里·S·德罗西耶; 特雷弗·赫格
Original assignee: Evapco Inc
Current assignee: Evapco Inc
Priority date: 2014-07-02
Filing date: 2015-07-02
Publication date: 2020-03-17
Anticipated expiration: 2035-07-02
Also published as: EP3164651A2; EP3164651A4; EP3869126A1; CN110260545A; EP4180746A1; CN106796073A; CN111503951A

Abstract

A packaged, pumped liquid cycle refrigeration system having a refrigerant charge of 10lbs or less per ton of refrigeration capacity. The compressor and related components are located in a pre-packaged modular machine room, and wherein the condenser is mounted on the machine room and the evaporator is closely coupled to the pre-packaged modular machine room. The large receiver vessels of the prior art may be replaced with single-phase or two-phase cyclonic separators, which are also housed in the pre-packaged modular machine room.

Description

Low charge packaged refrigeration system

Technical Field

The present invention relates to industrial refrigeration systems.

Background

Industrial refrigeration systems of the prior art, such as refrigeration systems for refrigerated warehouses, in particular amino refrigeration systems, are highly compartmentalized. The evaporator coil is often mounted on the ceiling of the refrigerated space or collected in a rooftop room on the roof of the refrigerated space, the condenser coil and fan are often mounted in a separate space on the roof of the building containing the refrigerated space, and the compressor, receiving tank, oil separation tank and other mechanical systems are often collected in a separate machine room remote from the common space. Industrial refrigeration systems containing large amounts of ammonia are highly regulated due to their toxicity to humans, their impact on release caused by human error or mechanical integrity, and the threat of terrorism. Systems containing more than 10,000lbs of ammonia require Risk Management Plan (RMP) for EPA and process Safety Management Plan (OSHA) for OSHA, and may result in federal agency review. The state of california has additional limitations/requirements for systems containing more than 500lbs of ammonia. Any refrigeration system leak that results in 100 pounds or more of ammonia emissions must be reported to the EPA.

Disclosure of Invention

The present invention is a packaged, pumped liquid cycle refrigeration system having a refrigerant charge of 10lbs or less per ton of refrigeration capacity. The present invention is a low charge packaged refrigeration system wherein the compressor and related components are located in a pre-packaged modular machine room and wherein the condenser is closely coupled to the pre-packaged modular machine room. According to embodiments of the present invention, a prior art large receiver vessel for separating refrigerant vapor and refrigerant liquid exiting from an evaporator and storing a backup refrigerant liquid may be replaced with a liquid-vapor separation structure/device housed in a pre-packaged modular machine room. According to one embodiment, the liquid-vapor separation structure/device may be a single-phase or a two-phase cyclone separator. According to another embodiment of the invention, the standard economizer vessel (which collects liquid from the condenser) can also optionally be replaced by a single-phase or two-phase cyclonic separator also housed in the pre-packaged modular machine room. The evaporator coil is preferably formed with internal enhancements to improve the flow of refrigerant liquid through the conduit, enhance heat exchange and reduce refrigerant charge. According to one embodiment, the condenser may be constructed of a coil preferably formed with internal enhancements that improve the flow of refrigerant vapor through the tubing, enhance heat exchange and reduce refrigerant. According to a more preferred embodiment, the evaporator tube enhancements and the condenser tube enhancements are different from each other. Co-pending provisional application 62/188,264 entitled "internal reinforced Tubes for Coil Products" is incorporated herein by reference in its entirety. According to an alternative embodiment, the condenser system may employ microchannel heat exchanger technology. The condenser system may be of any type known in the art for condensing refrigerant vapor to liquid refrigerant.

According to various embodiments, the system may be a liquid overfeed system or a direct expansion system, but most preferably is a very low charge or "critical charge" system with an overfeed rate (the ratio of the mass flow rate of liquid refrigerant entering the evaporator compared to the mass flow rate of vapor required to produce a cooling effect) of 1.05: 1.0 to 1.8: 1.0, with an overfeed rate of 1.2: 1 being preferred. To maintain such low overfeed rates, capacitive sensors such as those described in U.S. patent applications 14/221,694 and 14/705,781 (both of which are incorporated herein by reference in their entirety) may be provided at various points in the system to determine the relative amounts of liquid and vapor so that the system may be adjusted accordingly. Such a sensor is preferably located at the inlet of the liquid-vapor separation device and/or at the outlet of the evaporator and/or somewhere in the refrigerant line between the outlet of the evaporator and the liquid-vapor separation device and/or at the inlet of the compressor and/or somewhere in the refrigerant line between the vapor outlet of the liquid-vapor separation device and the compressor.

In addition, the condenser system and the machine room are preferably closely coupled to the evaporator. In the case of a rooftop evaporator arrangement in a "rooftop" room, in which the evaporator is located above the refrigerated space, the machine room is preferably connected to a prefabricated rooftop evaporator module. In the case of ceiling-mounted evaporators in refrigerated spaces, the integrated condenser system and modular machine room are mounted on the floor or roof directly above the evaporator units (so-called "separation systems").

The combination of features described herein provides a very low charge refrigeration system as compared to the prior art. Specifically, the present invention is configured to require less than 6 pounds of ammonia per ton of refrigeration capacity. According to a preferred embodiment, the present invention may require less than 4 pounds of ammonia per ton of refrigeration. According to the most preferred embodiment, the present invention can operate effectively at less than 2 pounds per ton of refrigeration capacity. In contrast, the prior art "stick build" systems require 15-25 pounds of ammonia per ton of refrigeration, and the prior art low charge systems require about 10 pounds per ton of refrigeration. Thus, for a 50 ton refrigeration system, the prior art rod build system requires 750-1,250 pounds of ammonia, the prior art low charge system requires approximately 500 pounds of ammonia, while 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 EPA reporting threshold (assuming all ammonia in the system leaks out). Indeed, according to the 50 ton refrigeration system of the present invention, the entire amount of ammonia in the system can be discharged to the surrounding area without significant damage or harm to humans or the environment.

Drawings

FIG. 1 is a schematic diagram of a refrigeration system according to an embodiment of the present invention.

Fig. 2 is an enlarged view of the upper left portion of fig. 1.

Fig. 3 is an enlarged view of the lower left portion of fig. 1.

Fig. 4 is an enlarged view of the lower right portion of fig. 1.

Fig. 5 is an enlarged view of the upper right portion of fig. 1.

Fig. 6 is a three-dimensional perspective view of a combined evaporator module and pre-packaged modular machine room according to an embodiment of the invention.

Fig. 7 is a three-dimensional perspective view of a combined evaporator module and pre-packaged modular machine room according to another embodiment of the invention.

Figure 8 is a three-dimensional perspective view of the interior of a pre-packaged modular machine room and condenser unit according to an embodiment of the invention.

Figure 9 is a three-dimensional perspective view of the interior of a pre-packaged modular machine room and condenser unit according to another embodiment of the present invention.

Fig. 10 is a three-dimensional perspective view of a combined evaporator module and pre-packaged modular machine room according to another embodiment of the invention.

Figure 11 shows a three-dimensional perspective view of three different embodiments of a combined evaporator module and pre-packaged modular machine room, wherein the left-hand embodiment comprises a top-mounted air-cooled condenser system.

Figure 12 shows a three-dimensional cross-sectional view of the interior of a pre-packaged modular machine room according to another embodiment of the present invention.

Fig. 13 shows a three-dimensional cross-sectional view of the interior of a combined rooftop evaporator module and pre-packaged modular machine room.

Detailed Description

Fig. 1 is a process and instrument diagram of a low charge packaged refrigeration system according to an embodiment of the invention. Enlarged views of the four quarters of fig. 1 are shown in fig. 2-5, respectively. The system includes

evaporators

2a and 2b, each including an

evaporator coil

4a, 4b, a condenser 8, a compressor 10,

expansion devices

11a and 11b (which may be provided in the form of valves, metering orifices or other expansion devices), a pump 16, a liquid-vapor separation device 12 and an economizer 14. According to one embodiment, the liquid-vapor separation device 12 may be a recycle vessel. According to other embodiments, one or both of the liquid-vapor separation device 12 and the economizer 14 can be provided in the form of a single-phase or a two-phase cyclonic separator. The foregoing elements may be connected in the manner shown in fig. 1-5 using standard refrigerant tubing. As used herein, unless otherwise specified, the term "connected to" or "connected via …" means directly or indirectly connected. The optional defrost system 18 includes a glycol tank 20, a glycol pump 22, a glycol condenser coil 24, and glycol coils 6a, 6b, which are also connected to each other and other elements in the system using refrigerant tubing according to the arrangement shown in fig. 1. According to other alternative embodiments, a hot gas or electric defrost system may be provided. An evaporator feed pump/recirculator 16 may also be provided to provide the additional energy required to force the liquid refrigerant through the evaporator heat exchanger.

According to the embodiment shown in fig. 1-5, low pressure liquid refrigerant ("LPL") is supplied to the evaporator by pump 16 through expansion device 11. The refrigerant receives heat from the refrigerated space, exits the evaporator as low pressure vapor ("LPV") and liquid, and is sent to a liquid-vapor separation device 12 (which may optionally be a cyclonic separator), which liquid-vapor separation device 12 separates the liquid from the vapor. The liquid refrigerant ("LPL") is returned to the pump 16 and the vapor ("LPV") is delivered to the compressor 10, the compressor 10 accumulates the vapor and sends high pressure vapor ("HPV") to the condenser 8, and the condenser 8 compresses the high pressure vapor to a high pressure liquid ("HPL"). High pressure liquid ("HPL") is delivered to the economizer 14, which increases system efficiency in the following manner: the high pressure liquid ("HPL") is reduced to an intermediate pressure liquid "IPL" which is then sent to the liquid-vapor separation device 12, and the liquid-vapor separation device 12 supplies low pressure liquid refrigerant ("LPL") to the pump 16, thereby completing the refrigerant cycle. The glycol flow path (in the case of the optional glycol defrost system) and the compressor oil flow path are also shown in fig. 1-5, but need not be discussed in greater detail herein, except to note that the present low charge packaged refrigeration system may optionally include a full defrost and compressor oil recirculation subsystem within the packaged system. Fig. 1-5 also include a number of control, isolation and safety valves and temperature and pressure sensors (also referred to as indicators or gauges) for monitoring and control of the system. Furthermore, an

optional sensor

26a, 26b may be located downstream of the

evaporator

2a, 2b, upstream of the inlet of the liquid-vapor separation device 12, to measure the vapor/liquid ratio of the refrigerant leaving the evaporator. According to an alternative embodiment, an optional sensor 26c may be located in the refrigerant line between the outlet of the liquid-vapor separation device 12 and the inlet of the compressor 10. The

sensors

26a, 26b and 26c may be capacitive sensors of the type disclosed in U.S. serial numbers 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 rooftop evaporator module and pre-packaged modular machine room according to an embodiment of the invention. According to this embodiment, the evaporator is housed in an evaporator module and the remaining components of the system shown in figures 1-5 are housed in a machine room module. Various embodiments of condenser systems that may be employed in accordance with the present invention include evaporative condensers with optional internal reinforcing tubes, air-cooled fin and tube heat exchangers with optional internal reinforcing, air-cooled microchannel heat exchangers, and water-cooled heat exchangers. In the case of an air cooled condenser system, the condenser coils and fans may be mounted on top of the machine room module for use with a fully independent roof 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 both roof modules, so that the entire system allows loading of non-escort vehicles (flat bed), for example, which are very easy to transport on the highway to the installation site. The roof room and machine room modules may be separated for transport and/or final placement, but according to the most preferred embodiment the roof room and machine room modules are mounted adjacent to each other to maximize the reduction of refrigerant charge. According to a most preferred embodiment, the roof room module and the machine room module are integrated into a single module, but the evaporator space is separated from the machine room space and insulated to comply with industry standards. Figures 7, 10 and 11 show further examples of adjacent roof house evaporator modules and machine room modules.

Fig. 8, 9 and 12 are three-dimensional cutaway perspective views of the interior of a pre-packaged modular machine room and condenser unit in which all the elements of the low charge packaged refrigeration system are contained in an integrated unit, except for the evaporator, according to an embodiment of the present invention. As discussed herein, the evaporator may be housed in a rooftop 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 in or supplied to the refrigerated space.

According to an alternative embodiment (e.g., where the end user does not wish to have cooling air in contact with the ammonia containing portion/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 is used to cool the air in the refrigerated space. In this case, the evaporator may be installed inside the machine room.

Fig. 13 is a cut-away three-dimensional perspective view of the interior of a combined rooftop evaporator module and pre-packaged modular machine room.

The combination of features described herein provides a very low charge refrigeration system as compared to the prior art. Specifically, the present invention is configured to require less than 6 pounds of ammonia per ton of refrigeration capacity. According to a preferred embodiment, the present invention may require less than 4 pounds of ammonia per ton of refrigeration. According to a most preferred embodiment, the present invention can operate effectively with less than 2 pounds per ton of refrigeration. In contrast, prior art "stick build" systems require 15-25 pounds of ammonia per ton of refrigeration, and prior art low charge systems require about 10 pounds per ton of refrigeration. Thus, for a 50 ton refrigeration system, the prior art rod build system requires 750-1,250 pounds of ammonia, the prior art low charge system requires approximately 500 pounds of ammonia, while 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 EPA reporting threshold (assuming all ammonia in the system leaks out). Indeed, according to the 50 ton refrigeration system of the present invention, the entire amount of ammonia in the system can be discharged to the surrounding area without significant damage or harm to humans or the environment.

Although the present invention is described primarily in the context of a refrigeration system in which ammonia is the refrigerant, it is contemplated that the present invention will be equally applicable to refrigeration systems using other natural refrigerants, including carbon dioxide.

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 compact system) low refrigerant charge (i.e., less than 10 pounds of refrigerant per ton of refrigeration capacity) refrigeration system are intended to be within the scope of the invention. Any changes to the specific embodiments described herein that would otherwise constitute a packaged, pumped liquid cycle refrigeration system and in which there is 10lbs or less of refrigerant per ton of refrigeration capacity should not be considered as departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

1. A refrigeration system comprising:

the coils of the refrigerant evaporator are provided with,

a vapor/liquid separation structure connected to an outlet of the evaporator coil via a refrigerant line and configured to separate low pressure refrigerant vapor from low pressure refrigerant liquid;

a refrigerant compressor connected to an outlet of the liquid-vapor separation device via a refrigerant line and configured to compress refrigerant vapor from the vapor-liquid separation structure;

a refrigerant condenser connected to an outlet of the refrigerant compressor via a refrigerant line and configured to condense refrigerant vapor generated in the compressor into refrigerant liquid,

a high pressure side expansion device connected to an outlet of the refrigerant condenser via a refrigerant line and configured to reduce a pressure of a refrigerant liquid received from the refrigerant condenser;

a collection vessel connected to an outlet of the high pressure side expansion device via a refrigerant line to receive refrigerant liquid from the high pressure side expansion device;

a low pressure side expansion device connected to an outlet of the collection vessel via a refrigerant line and configured to reduce a pressure of a refrigerant liquid received from the collection vessel;

a refrigerant line connecting an outlet of the low side expansion device to an inlet of the vapor/liquid separation structure, the refrigerant line configured to deliver refrigerant liquid to the separation structure;

the vapor/liquid separation structure having a liquid outlet connected to an inlet of the evaporator via a refrigerant line;

wherein the vapor/liquid separation structure, the compressor, the high pressure side expansion device, the collection vessel, and the low pressure side expansion device are located within a pre-packaged modular machine room;

wherein the refrigeration system requires less than six pounds of refrigerant per ton of refrigeration capacity.

2. The refrigeration system of claim 1, wherein the refrigerant is ammonia.

3. The refrigeration system of claim 1, wherein the vapor/liquid separation structure comprises a cyclonic separator.

4. The refrigeration system of claim 1, wherein the vapor/liquid separation structure comprises a recirculator vessel.

5. The refrigeration system of claim 1, wherein the collection vessel comprises a cyclonic separator.

6. The refrigeration system of claim 1, wherein the collection vessel comprises an economizer.

7. The refrigeration system of claim 1, wherein the evaporator coil has internal enhancements to improve the flow of liquid/vapor in the evaporator coil and to improve heat exchange and refrigerant charge.

8. The refrigeration system of claim 1, wherein the condenser comprises a coil with internal enhancements.

9. The refrigeration system of claim 1, wherein the condenser comprises a microchannel heat exchanger.

10. The refrigeration system of claim 1, further comprising a liquid-to-vapor mass ratio sensor located in a refrigerant line connecting the evaporator coil and the vapor/liquid separation structure.

11. The refrigeration system of claim 1, further comprising a liquid-to-vapor mass ratio sensor located within a refrigerant line connecting the vapor/liquid separation structure and the compressor.

12. The refrigeration system of claim 1, further comprising an oil separator vessel configured to separate compressor oil from refrigerant vapor received from the compressor.

13. The refrigeration system of claim 1, wherein the condenser is an air-cooled condenser comprising a coil and a condenser fan located on top of the pre-packaged modular machine room.

14. The refrigeration system of claim 1, wherein the condenser is located inside the pre-packaged modular machine room.

15. The refrigeration system of claim 1, requiring less than four pounds of refrigerant per ton of refrigeration capacity of the refrigeration system.

16. The refrigeration system of claim 1, requiring less than two pounds of refrigerant per ton of refrigeration capacity of the refrigeration system.