Non-compression cascade refrigeration system for closed refrigerated spaces

#This invention relates to commercial refrigeration systems for enclosed refrigerated spaces which have walk-in freezers or other large chilled spaces and primary mechanical refrigeration equipment in remotely located machine areas for supplying coolant fluid to the evaporators in the chilled spaces, with an intermediate heat exchange system between the primary mechanical refrigeration equipment area and the chilled spaces to reduce the amount of coolant that is communicated to the evaporator in the chilled space.

#Modern supermarkets require a large amount of refrigeration for freezing and chilling the goods purchased by its customers. Typically, the freezers and coolers are located in random positions about the customer areas of the supermarket, in optimum locations for marketing purposes. In some instances, large closed refrigerated spaces and fixtures, including walk-in freezers or walk-in coolers are provided for butchers and other personnel of the supermarket, and occasionally for customers where large stocks of chilled items are maintained. While these larger closed refrigerated spaces are highly desirable, it is also desirable to use as little refrigerant coolant fluid as possible to chill these spaces. This is because the refrigerants must pass through an evaporator in the chilled space and there is a hazard that the refrigerant will leak into the atmosphere of the closed chilled space and be inhaled by customers, workers, and others. Refrigerants may replace oxygen in a closed space and result in oxygen deprivation, and possibly death by asphyxiation.

#As a result of this hazard, federal and state regulations limit the amount of refrigerant that can be used to cool freezer rooms and other large closed refrigerated spaces which can be occupied by a person, either by an employee of the supermarket or by a customer. In most instances, the typical walk-in refrigerated space, etc. requires more refrigerant than is permitted by the federal and local regulations in order to adequately cool the space, particularly when people frequently move into and out of the chilled space. The result of this situation is that walk-in refrigerated spaces and other large closed refrigerated spaces that have frequent entry of people and therefore a large refrigeration load are not commonly available in typical supermarkets.

#FIG. 1 is a perspective illustration of the Cascade Refrigeration System as it is connected to a conventional primary refrigeration system.

#FIG. 2 is a front elevational view of the Cascade Refrigeration System.

#FIG. 3 is a side elevational view of the Cascade Refrigeration System.

#Referring now in more detail to the drawings, in which like numerals indicate like parts throughout the several views, FIG. 1 illustrates the refrigeration system 10 which includes a conventional primary refrigeration system 12 that is located in a remote area of a supermarket, such as on the roof or on the roof and in a machine room, as generally indicated by the dash lines 14. Coolant is received through a return conduit 16 at the compressor 18 and delivered to the condenser 20, in which the coolant changes into a liquid state. The coolant moves from the condenser 20 through the delivery line 22 back into the supermarket and is received through expansion valve 23 in a primary evaporator 24, whereby the coolant absorbs heat.

#The evaporator 24 is part of a prior art condenser-evaporator plate heat exchanger 26 such as a brazed plate heat exchanger produced by Swep, Inc. or by Alfa Laval Thermal, Inc.

#The non-compression cascade refrigeration system 30 has its components, except for its evaporator, supported in a framework 32 as indicated by the dash lines in FIG. 1, and includes a condenser 34 that is part of the condenser-evaporator plate heat exchanger 26, and evaporator 28 that is located within the walk-in refrigerated space 40 as indicated by the dash lines in FIG. 1, and a liquid-vapor separator 42. A first delivery conduit 44 delivers coolant in a liquid form from the condenser 34 of the condenser-evaporator plate heat exchanger 26 to the separator 42. A second delivery conduit 46 transmits liquid coolant from the separator 42 in a downward direction to the cascade evaporator 28 in the refrigerated space 40. The coolant changes from a liquid state to a liquid and gaseous state in the evaporator 28, with electric fans 48 moving air across the evaporator, so that the evaporator chills the air. So configured, the first and second coolant delivery conduits form a coolant delivery system for delivering coolant in a liquid state from the cascade condenser to the evaporator.