Device for metering refrigerant flow to an evaporator and systems incorporating same

Abstract

Metering devices suitable for incorporation into vapor-compression refrigeration systems are disclosed, having adjustable features that allow them to regulate the pressure drop across them. These devices include a screw with flights positioned to define a path for the liquid refrigerant to flow through, causing frictional pressure losses. Refrigerant systems incorporating these metering devices are also disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/476,676 filed Jun. 6, 2003.

FIELD OF THE INVENTION

The present invention relates to valves and metering devices in refrigeration loops and refrigerant based test systems, useful for example in the automotive, HVAC, home appliance and industrial refrigeration fields. More particularly the present invention relates to such devices suitable for the control of pressure drop within a refrigeration loop, and systems incorporating such devices.

BACKGROUND OF THE INVENTION

Conventional vapor and compression refrigeration loops incorporate a condensor and an evaporator, in fluid connection with a compressor and a metering device. The metering device is positioned between the condenser and the evaporator to lower the pressure of the liquid before it is evaporated. Traditionally, this is accomplished using either a capillary tube or a thermostatic expansion valve.

In operation, a capillary tube uses a channel having a specific length and diameter to create frictional losses, resulting in pressure drop of the liquid as it traverses through the channel. This equipment has the disadvantage that it is not adjustable to suit a variety of desired pressure drops, inasmuch as both the length and the diameter of capillary tube used in the refrigeration system is constant or fixed. Given this limitation, the amount of superheated fluid that leaves the evaporator is also not adjustable, so that liquid could reach the compressor should the operating conditions change.

A thermostatic expansion valve overcomes this problem, but such valves are typically bulky and expensive to manufacture.

It is an object of the present invention to provide a metering valve suitable for use in refrigeration systems, which allows for adjustments in desired pressure drop across the device. A further object of the present invention is to provide such a metering valve which can incorporate a variety of fluid flow configurations therealong. A feature of the present invention is that it can be retrofitted into existing refrigeration systems including those used in HVAC and automotive applications. It is an advantage of the present invention to provide a metering valve with a minimal number of parts which promotes long service life. These and other objects, features and advantages of the present invention will become better understood upon having reference to the description of the invention herein.

SUMMARY OF THE INVENTION

There is disclosed and claimed herein a device suitable for metering the flow of fluid therealong, comprising:

• • (a) a casing defining an inlet port, a side port and an end port; and
  • (b) a screw positioned within said inlet port and sufficient to block the flow of fluid therethrough, said screw comprising a member and flights positioned along all or a portion of the length of said member,
  • such that fluid entering said side port or said end port flows along a pathway defined by said member and said flights of said screw sufficient to achieve a desired frictional pressure loss and thereafter exits said end port or said side port, respectively.

The invention will become better understood upon having reference to the drawings herein.

IN THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional vapor-compression refrigeration cycle;

FIG. 2 is a cross sectional side view of one embodiment of the device according to the invention with the valve sealing to the threads therein; and

FIG. 3 is a cross sectional side view of another embodiment of the device according to the invention with the valve sealing to the shaft therein.

DETAILED DESCRIPTION OF THE INVENTION

Having reference to FIG. 1 herein, there is shown generally at 10 a schematic of a typical refrigeration cycle. Those having skill in this field will readily appreciate the thermodynamics associated with this diagram. In general, an evaporator 12 and a condenser 14 are in fluid connection with each other. The compressor 16 is positioned to receive fluid from the evaporator 12 and feeds into the condenser 14. A metering device 18 is positioned to receive fluid from the condenser 14 and feeds into the evaporator 12. Passages 20 (as piping, tubing and the like) connect each of the elements above in the aforementioned sequence.

Having reference to FIG. 2 herein, there is shown generally at 22 one embodiment of the metering device 18 of the invention herein. This metering device 18 includes a casing 24 (typically tubular) with an inlet port 26 and a screw 28 positioned around the member 40. The liquid refrigerant enters through either the side port 30 or the end port 32 and is forced around the flights 34 of the screw 28 (and outside the member 40) until it exits at the end port 32 or the side port 30 respectively. These flights 34 can be any shape or size, and are configured to develop a desired path length for the liquid refrigerant to flow therealong. The pressure drop is achieved by the liquid refrigerant traveling the path defined by the screw 28 and the member 40, which causes frictional pressure losses. The screw 28 is fitted through a sealed hole 36 in the inlet port 26 so that it can be retracted or inserted to adjust the length of the path that the fluid must travel before it reaches the exit (either side port 30 or end port 32).

Having reference to FIG. 3 herein, there is shown generally at 38 another embodiment of the metering device 18 of the invention herein. The design depicted in FIG. 3 is identical to that in FIG. 2 except instead of forming the sealed hole 36 with the flights 34 of the screw 28, an unthreaded member 40 is positioned at the end of the screw 28 closest to the sealed hole 36 and the seal is thereby made with this unthreaded member 40. Both configurations allow the pressure drop to be adjusted to the proper amount to give desired superheating.

Various attributes of the invention as described above can be manufactured according to conventional techniques, all as is readily understood by those of relevant skill in the art. For example, the sealed hole 36 may be sealed by fitting in place an elastomeric compound suitable for withstanding the motion through the sealed hole 36 and resistant to degradation by the elements and the refrigerants. The member 40 and the flights 34 are likewise constructed from materials that function in place for extended periods of time and without failure, and such that they are mechanically sound and resistant to chemical attack. Metals such as aluminum are attractive for this purpose. Finally the casing 24 can be made of a variety of materials including a wide array of metals and plastics, such that they meet design specifications for overall size and shape and function to retain the fluids therewithin. Copper and brass can be selected as useful materials in the design of a durable assembly according to the invention.

It is readily understood and appreciated that those having skill in the art to which this invention pertains can make any number of variations and modifications to the invention as set forth and described herein. Such enhancements are contemplated as within the spirit and scope of the invention.

Claims

1. A device suitable for metering the flow of fluid therealong, comprising:

(c) a casing defining an inlet port, a side port and an end port; and

(d) a screw positioned within said inlet port and sufficient to block the flow of fluid therethrough, said screw comprising a member and flights positioned along all or a portion of the length of said member,

such that fluid entering said side port or said end port flows along a pathway defined by said member and said flights of said screw sufficient to achieve a desired frictional pressure loss and thereafter exits said end port or said side port, respectively.

2. The metering device of claim 1 wherein said flights of said screw extend along said member and contact said inlet port.

3. The metering device of claim 1 wherein said flights of said screw extend along said member but do not contact said inlet port.

4. A vapor-compression refrigeration cycle system incorporating the metering device of claim 1, wherein said metering device receives fluid from a condenser and directs fluid to an evaporator.