Patent Application
20180163998
The present invention relates to industrial refrigeration systems.
Prior art industrial refrigeration systems, e.g., for refrigerated warehouses, especially ammonia based refrigeration systems, are highly compartmentalized. The evaporator coils are often ceiling mounted in the refrigerated space or collected in a penthouse on the roof of the refrigerated space, the condenser coils and fans are usually mounted in a separate space on the roof of the building containing the refrigerated space, and the compressor, receiver tank(s), oil separator tank(s), and other mechanical systems are usually collected in a separate mechanical room away from public spaces. Ammonia-based industrial refrigeration systems containing large quantities of ammonia are highly regulated due to the toxicity of ammonia to humans, the impact of releases caused by human error or mechanical integrity, and the threat of terrorism. Systems containing more than 10,000 lbs of ammonia require EPA's Risk Management Plan (RMP) and OSHA's Process Safety Management Plan and will likely result in inspections from federal agencies. California has additional restrictions/requirements for systems containing more than 500 lbs of ammonia. Any refrigeration system leak resulting in the discharge of 100 lbs or more of ammonia must be reported to the EPA.
The present invention is a packaged, pumped liquid, recirculating refrigeration system with charges of 10 lbs or less of refrigerant per ton of refrigeration capacity. The present invention is a low charge packaged refrigeration system in which the compressor and related components are situated in a pre-packaged modular machine room, and in which the condenser is close coupled to the pre-packaged modular machine room. According to an embodiment of the invention, the prior art large receiver vessels, which are used to separate refrigerant vapor and refrigerant liquid coming off the evaporators and to store backup refrigerant liquid, may be replaced with liquid-vapor separation structure/device which is housed in the pre-packaged modular machine room. According to one embodiment, the liquid-vapor separation structure/device may be a single or dual phase cyclonic separator. According to another embodiment of the invention, the standard economizer vessel (which collects liquid coming off the condenser) can also optionally be replaced with a single or dual phase cyclonic separator, also housed in the pre-packaged modular machine room. The evaporator coil tubes are preferably formed with internal enhancements that improve the flow of the refrigerant liquid through the tubes, enhance heat exchange and reduce refrigerant charge. According to one embodiment, the condenser may be constructed of coil tubes preferably formed with internal enhancements that improve the flow of the refrigerant vapor through the tubes, enhance heat exchange and reduce refrigerant. According to a more preferred embodiment, the evaporator tube enhancements and the condenser tube enhancements are different from one-another. The specification of co-pending provisional application Ser. No. 62/188,264 entitled “Internally Enhanced Tubes for Coil Products” is incorporated herein 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 into liquid refrigerant.
According to various embodiments, the system may be a liquid overfeed system, or a direct expansion system, but a very low charge or “critically charged” system is most preferred with an overfeed rate (the ratio of liquid refrigerant mass flow rate entering the evaporator versus the mass flow rate of vapor required to produce the cooling effect) of 1.05:1.0 to 1.8:1.0, and a preferred overfeed rate of 1.2:1. In order to maintain such a low overfeed rate, capacitance sensors, such as those described in U.S. patent application Ser. Nos. 14/221,694 and 14/705,781 the entirety of each of which is incorporated herein by reference, 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 sensors are preferably located at the inlet to the liquid-vapor separation device and/or at the outlet of the evaporator, and/or someplace in the refrigerant line between the outlet of the evaporator and the liquid-vapor separation device and/or at the inlet to the compressor and/or someplace in the refrigerant line between the vapor outlet of the liquid-vapor separation device and the compressor.
Additionally, the condenser system and the machine room are preferably close-coupled to the evaporators. In the case of a penthouse evaporator arrangement, in which evaporators are situated in a “penthouse” room above the refrigerated space, the machine room is preferably connected to a pre-fabricated penthouse evaporator module. In the case of ceiling mounted evaporators in the refrigerated space, the integrated condenser system and modular machine room are mounted on a floor or rooftop directly above the evaporator units (a so-called “split system”).
According to a further embodiment, the compressor and related components may be situated inside the plenum of an evaporative condenser and the coil of the evaporative condenser is close coupled to the compressor and other components of the chiller package. Specifically, according to this embodiment, underutilized space in the plenum of a standard or modified prior art evaporative condenser is used to house the remaining components of the chiller package, with the evaporator located in the refrigerated space or in an evaporator module preferably adjacent to the integrated evaporative condenser/chiller package. According to this embodiment, the system may use an induced draft co-flow condenser coil with crossflow fill. The air enters on one long side of the package through the fill media and at the top of the coil. The balance of the chiller package is housed within the condenser plenum with the sump located below. An additional benefit of this integrated arrangement is that it may allow reach-in, rather than walk-in, access to chiller service items.
According to an alternate embodiment of the invention, there may be presented induced draft evaporative condenser arrangement which may replace the fill media with a larger condensing coil extending across the plan area. In this embodiment, the air and water would be in a counterflow arrangement through the evaporative condensing coil. The induced draft arrangement allows ambient air to enter below the coil on all sides, including through the chiller area, as long as that area is not enclosed, though the chiller components must be isolated from the falling spray water.
According to still further embodiments, forced draft units with either axial or centrifugal fans are presented. According to these evaporative condensing with forced draft axial or centrifugal fan embodiments, the fans would blow air into the unit from one long side of the condenser. A wall between the chiller package and the plenum is required to turn the air, directing it upward through the coil.
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 pound 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.
According to the embodiment shown in
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.
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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 62432883 | Dec 2016 | US |
