Refrigeration System Including A Flow Metering Device

Abstract

A refrigerant flow metering device for use in a refrigeration system comprising a housing having an inlet and an outlet and defining a bore disposed within its confines, the ends of which communicate with the inlet and outlet, said bore being of a variable cross section to form a variable passage. A valve element positioned within the bore is capable of movement therein in response to changes in pressure in the refrigeration system. A spring associated with the valve element provides a force to move the element toward the inlet of said housing.

Description

BACKGROUND OF THE INVENTION

This invention relates to a refrigeration system and more particularly, to a refrigeration system including a refrigerant flow metering device for regulating the flow of refrigerant from the condenser to the evaporator.

The need for a device to meter the flow of refrigerant in refrigeration systems is well known to those skilled in the art. Most refrigeration systems employ either a thermostatic expansion valve or a capillary tube as the required metering device. However, each of the above-mentioned apparatus possesses disadvantages which limit their utility.

Thermostatic expansion valves, while being highly efficient in their operation and readily responsive to changes in load upon the system to vary the flow of refrigerant to the evaporator, are also relatively expensive. Therefore, they are generally not employed in small applications such as room air conditioners.

Capillary tubes are generally employed in lieu of the thermostatic expansion valves for such small applications, wherein ambient air is almost universally utilized as the condensing medium. Although capillary tubes are relatively inexpensive to manufacture and are simple to install, when used in applications wherein ambient air is employed as the condensing medium, certain problems generally occur.

For example, at relatively high ambient temperatures, the pressure differential between the condenser and evaporator is of a relatively large magnitude, thus producing a substantial flow of refrigerant through the capillary tube disposed between the condenser and evaporator. At times, the refrigerant flow might become excessive and a portion of the refrigerant flowing to the evaporator will not be evaporated therein and will remain in its liquid state as it passes to the compressor. The introduction of liquid refrigerant into the compressor may produce serious problems, such as breakage of valves, in addition to a decrease in the efficiency of operation of the compressor.

An additional problem is found at relatively low ambient temperatures wherein the pressure differential between the condenser and the evaporator is of a relatively small magnitude, whereby the flow of refrigerant through the capillary tube is decreased. If the flow of refrigerant at low ambient temperatures is insufficient, the compressor will reduce the pressure in the evaporator coil below its designed operating point, and the evaporator coil will begin to freeze, thereby reducing the transfer of heat between the medium to be cooled, such as room air, and the refrigerant flowing through the evaporator, thus reducing the efficiency of the system operation.

The object of this invention is a refrigerant flow metering device that will obviate the problems hereinbefore discussed.

SUMMARY OF THE INVENTION

This invention relates to a refrigeration system and, in particular, to a novel refrigerant flow metering device which is relatively inexpensive to manufacture and possesses none of the disadvantages of the capillary tube hereinbefore noted. The novel device operates to prevent excessive flow of refrigerant at relatively high ambient temperatures and additionally operates to prevent freezing of the evaporator coil at relatively low ambient temperatures. In addition, the novel device herein disclosed operates to permit rapid equalization of the pressure differential between the condenser and evaporator when operation of the system is discontinued. Rapid equalization permits utilization of a low-starting torque motor to drive the compressor, thus eliminating the need for expensive high-starting torque motors, or in the alternative, eliminating the need for such devices as time delays to prevent restarting of the compressor motor before a sufficient period of time has elapsed, to enable the pressure in the refrigeration system to equalize of its own accord.

The device includes a housing having an inlet and an outlet and defining a bore disposed within its confines, the ends of which communicate with the inlet and outlet. The bore is of a variable cross section and thereby forms a variable restriction or passage. The narrower portion of the variable cross section passage is formed relatively close to the outlet of the housing, and the wider portion of the variable cross section passage is formed relatively close to the inlet of the housing. A valve element is positioned within the bore and is capable of movement therein in response to changes in pressure in the refrigeration system. A spring associated with the valve element provides a force to move the valve element toward the inlet of the housing. The valve element moves toward the outlet of the housing upon an increase in the pressure differential of the system and moves toward the inlet of the housing upon a decrease in the pressure differential of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a refrigeration system including the novel refrigerant flow metering device; and

FIG. 2 is a cross-sectional view of the novel device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and in particular to FIG. 1, there is shown a refrigeration system including the novel refrigerant flow metering device herein disclosed. In referring to the drawings, like numerals shall refer to like parts.

The refrigeration system of FIG. 1 includes a compressor 10 connected to condenser 11 by conduit 12. Condenser 11 is connected to evaporator 22 by conduits 13 and 13'. Refrigerant metering device 14 is disposed between conduits 13 and 13' and operates to regulate the flow of refrigerant from the condenser to the evaporator. Conduit 15 connects the evaporator to the suction side of the compressor.

Relatively high pressure refrigerant gas is discharged from the compressor via conduit 12 and flows to condenser 11 where it passes in heat transfer relation with a relatively cool medium such as ambient air, passed thereover by means not shown, the refrigerant gas rejecting heat to the cool medium and being condensed thereby. The liquid refrigerant thus formed passes via conduit 13, through device 14 and conduit 13', to evaporator 22. The refrigerant absorbs heat in the evaporator from the medium to be cooled such as room air which is passed over the evaporator (by means not shown) in heat transfer relation with the refrigerant which is vaporized thereby. The gaseous refrigerant thus formed is returned to the compressor via conduit 15. The refrigeration system thus described is typical of the type found in window mounted room air conditioners, but it should be understood that such systems may be employed in other applications. The compressor outlet and the inlet to the refrigerant flow metering device define a high pressure side of the refrigeration system, and the refrigerant flow metering device outlet and compressor inlet define a low pressure side of the system.

The refrigerant flow metering device disposed between the condenser and the evaporator operates to regulate the flow of refrigerant in response to the cooling load imposed on the system. Generally, such device is sized so that a predetermined amount of refrigerant will flow therethrough when the ambient temperature is within a range generally referred to in the art as the design operating range.

For smaller applications, the refrigerant flow metering device generally employed is a capillary tube. Although such device generally functions as desired when the ambient temperature is within its design range, such device does not function as desired when the ambient temperature either exceeds or falls below the desired range as heretofore noted. Although thermostatic expansion valves may be employed to substantially increase the operating range, such devices are relatively expensive. As will become more apparent hereinafter, the novel refrigerant flow metering device obviates the problems heretofore discussed without substantially increasing the manufacturing costs as would occur by utilization of a thermostatic expansion valve.

Referring now to FIG. 2 there is shown a cross-sectional view of the novel refrigerant flow metering device employed in the refrigeration system of FIG. 1. The device includes a main body member or housing 16 having a threaded portion 17. Enclosing the upper end of body member 16 is a cap member 18, connected to the body member by means such as induction brazing indicated by reference numeral 23. The refrigerant metering device has an inlet thereto 24 and an outlet therefrom 25. The inlet and outlet are connected together by a bore 19 disposed within the confines of body member 16. The bore has a variable cross section as clearly shown in FIG. 2, thus forming a variable passage.

Mounted within bore 19 is valve element 20, which is capable of reciprocal movement in said bore relative to body member 16. Associated with valve element 20 is spring 21 which provides a biasing force moving the valve element toward the wider end of the variable cross section bore, the wider end being relatively close to the inlet of device 14. The narrower portion of bore 19 is relatively close to the outlet of the device.

Threadably connected to portion 17 of body member 16 is calibrating member 28. Calibrating member 28 includes seat portion 29, upon which spring 21 is mounted. Calibrating member 28 is rotated relative to body member 16 to provide a predetermined compressive force on spring 21. This compressive force provides the desired operating range for device 14. If desired, after calibration, calibrating member 28 can be permanently affixed relative to body member 16 by means such as induction brazing, represented by reference numeral 27.

When assembled, device 14 is installed between conduits 13 and 13' as shown in FIG. 1 and may be permanently affixed therein by means such as induction brazing shown by reference numerals 30 and 31.

As noted hereinbefore, problems occur when capillary tubes are employed in refrigeration systems utilizing ambient air as the condensing medium. The novel refrigerant metering device will properly control the flow of refrigerant even though the ambient temperature has substantially increased or decreased from the design operating point.

For example, assume the ambient temperature has increased above the design point, thus increasing the magnitude of the pressure differential between the condenser and the evaporator. The refrigerant flow from the condenser to the evaporator will correspondingly tend to increase. The increased pressure, caused by the increase in ambient temperature, acting on the valve element 20 in bore 19 will force the element toward the narrower portion of the bore, thus reducing the flow area about the valve element, and acting to moderate the increased flow of refrigerant passing to the evaporator due to the increase in pressure differential. Although the flow area about valve element 20 has been reduced due to the movement thereof toward the narrower portion of the bore, the total flow of refrigerant passing to the evaporator will increase as desired upon the increase in ambient temperature. The reduced flow area operates to moderate the increase of refrigerant flow thereby preventing the problems encountered with capillary tubes operating at high ambient temperatures.

Assume now that the ambient temperature is relatively low as compared to the design operating point. Thus, the pressure differential between the condenser and the evaporator is of a relatively small magnitude. At the relatively small magnitude pressure differential, the flow of refrigerant from the condenser to the evaporator is correspondingly decreased. As noted hereinbefore, such a decrease in refrigerant flow where a capillary tube is installed may cause freezing of the evaporator coil. However, as shall be apparent, such a condition will not occur when the novel refrigerant flow metering device is utilized.

The reduced ambient temperature operates to decrease the pressure acting on valve element 20 of device 14. Spring 21 moves the valve element toward the wider portion of bore 19, thus increasing the flow area for the refrigerant through the device. Thus, the reduction in the magnitude of the pressure differential between the condenser and evaporator resulting from the decrease in ambient temperature is compensated by the increase in flow area through the device to maintain the flow of refrigerant to the evaporator at a sufficient level to prevent the evaporator coil from freezing due to refrigerant starvation. The increased flow area about valve element 20 operates to moderate the reduction in refrigerant flow caused by the decrease in ambient temperature.

The novel metering device further provides an additional advantage upon shutdown of the refrigeration system. Upon shutdown, the pressure differential between the condenser and the evaporator decreases. With the standard capillary tube, refrigerant flow from the condenser to the evaporator is reduced, thereby prolonging the period of time in which equalization of the pressure differential between the high pressure side and low pressure side of the system will be obtained. If it is desired to restart the compressor motor while the pressure differential is still relatively high, high-starting torque motors are required, thus increasing the cost of the refrigeration system. Alternatively, if it is desired to prevent the restarting of the compressor motor until the pressure differential has substantially equalized, such devices as time delay apparatus must be included in the compressor motor circuitry, also increasing overall cost.

By employing the novel device 14, as the pressure differential decreases upon compressor shutdown, spring 21 moves valve element 20 to increase the flow area for the refrigerant through device 14. Thus, device 14 promotes more rapid equalization, thus obviating the need for either high-starting torque motors or devices to provide time delay in restarting of the compressor motor.

It should be understood that devices such as accumulators, disposed between the evaporator outlet and compressor suction, may be required to prevent liquid refrigerant from flowing to the compressor upon start-up of the system. Accumulators are generally employed in refrigeration systems utilizing capillary tubes, and their utilization may be similarly required for applications employing the device of this invention.

While I have described a preferred embodiment of my invention, it is to be understood that the invention is not so limited thereto since it may be otherwise embodied within the scope of the following claims.

Claims

I claim:

1. A refrigeration system including a compressor, a condenser, an evaporator, and a flow metering device disposed between said condenser and said evaporator, connected together to form said system, said compressor and said flow metering device defining therebetween a high pressure side and a low pressure side of said system, said flow metering device comprising:

A. a valve housing having an inlet and an outlet and defining a bore disposed within its confines, said bore providing a flow path for refrigerant passing from said condenser to said evaporator through said flow metering device; and

B. means operable to decrease the cross section of said bore as the pressure differential between said condenser and said evaporator increases, and being further operable to increase the cross section of said bore as the pressure differential between said condenser and said evaporator decreases.

2. A refrigeration system in accordance with claim 1 wherein said last-mentioned means includes a valve element and a biasing member associated therewith, said biasing member providing a force acting on said valve element in opposition to a force provided by the refrigerant flowing through said metering device.