US3531947A

US3531947A - Refrigeration system including refrigerant noise suppression

Info

Publication number: US3531947A
Application number: US771464A
Authority: US
Inventors: Francis M Drury; Jerry A Priest
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1968-10-29
Filing date: 1968-10-29
Publication date: 1970-10-06
Anticipated expiration: 1987-10-06
Also published as: BR6913732D0

Description

Oct. 6, 1970 DRURY ETAL 3,531,947

REFRIGERATION SYSTEM INCLUDING REFRIGERANT NOISE SUPPRESSION Filed 001;. 29, 1968 INVENTORS FRANCIS M. DRURY &JERRY A. Pan: T

THEIR ATTORNEY United States Patent 3,531,947 REFRIGERATION SYSTEM INCLUDING REFRIGERANT NOISE SUPPRESSION Francis M. Drury and Jerry A. Priest, Louisville, Ky.,

assignors to General Electric Company, a corporation of New York Filed Oct. 29, 1968, Ser. No. 771,464 Int. Cl. F251) 41/06 US. Cl. 62511 3 Claims ABSTRACT OF THE DISCLOSURE A refrigeration system comprising in closed series-flow relationship a condenser, a tubular flow restrictor and an evaporator includes means connecting the outlet end of the restrictor to the evaporator inlet for reducing the noise generated by refrigerant flowing from the restrictor.

BACKGROUND OF THE INVENTION A well known refrigeration system includes in closed, series-flow relationship an evaporator, a compressor for Withdrawing refrigerant from the evaporator, a condenser for condensing the refrigerant compressed by the compressor and tubular flow restrictor means for controlling the flow of refrigerant to the evaporator. The tubular flow restrictor means, commonly referred to as a capillary tube, maintains the desired pressure differential between the condenser and the evaporator by restricting the flow of refrigerant therethrough and to this end its internal diameter is substantially less than the internal diameter of the conduit forming the inlet end of the evaporator.

The refrigerant exiting from the flow restrictor may be in the form of liquid or gas or a mixture of the two. Also as it exits fom the flow restrictor a portion thereof usually vaporizes at the lower pressure condition in the evaporator. The boiling turbulence resulting from this vaporization as well as the exit velocity of the refrigerant, which is close to sonic speed, constitute a major source of noise in the operation of such a refrigeration system. This noise can be particularly bothersome in the operation of refrigeration systems such as those contained in room air conditioners. The usual means for isolating this source of noise from the enclosure being conditioned has been to locate the outlet end of the flow restrictor on the outdoor side of the usual partition separating the room air conditioner into indoor and outdoor compartments. This requires an additional unrestricted connecting tube for connecting the outlet end of the flow restrictor to the inlet end of the evaporator which is positioned within the indoor compartment and results in some cooling loss in the system.

SUMMARY OF THE INVENTION The present invention is directed to the provision of means connecting the tubular flow restrictor with the inlet end of the evaporator designed to control the flashing of liquid refrigerant to gas in a manner such that the usual noises associated with this portion of a refrigeration system are substantially suppressed or eliminated.

To this end, there is provided in a refrigeration system comprising a condenser, a tubular flow restrictor and evaporator in closed series flow connection, improved means for connecting the outlet end of the flow restrictor to the inlet end of the evaporator made up of at least three sucessive tubular sections or segments of progressively increasing diameters and decreasing lengths. In accordance with a preferred and commercially practicable form of the invention, this connecting means comprises a series of telescoping interconnected tubular sections each of which is a standard diameter refrigeration tubing with ice the internal diameter of each succeeding tube being substantially equal of the external diameter of the preceding tubular section. The lengths of each section progressively decrease to provide a gradual flaring of the connector in the direction of its outlet to the evaporator.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawing:

FIG. 1 is a schematic diagram of a closed refrigeration system incorporating the present invention,

FIG. 2 is an enlarged sectional view of the connecting means forming part of the refrigerating system of FIG. 1; and

FIG. 3 is a sectional view of an alternative form of connecting means for practicing the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1 of the accompanying drawing, there is illustrated diagrammatically a refrigeration system including a compressor 1, a condenser 2, a tubular flow restrictor, such as a capillary tube 3-, the improved connecting means 4 of the present invention and an evaporator 5 connected in closed series-flow relationship. In the operation of such a system, the compressor 1 withdraws refrigerant vapor from the evaporator 5 and discharges compressed refrigerant to the condenser 2. The high pressure refrigerant condensed in the condenser 2 passes through the capillary tube 3 to the evaporator 5. The capillary tube 3 provides a substantial restriction to the flow of liquid refrigerant to the evaporator and thereby maintains the desired range of pressure differential between the condenser and the evaporator in a well known manner.

To maintain such pressure differential, the internal diameter of the capillary tube 3 is substantially smaller than the remaining fluid passages in the refrigeration system including the inlet end 6 to the evaporator 5. In previously known refrigeration systems of this type such as those specifically used in room air conditioners, the outlet end of the capillary tube 3 was connected directly to the inlet end 6 of the evaporator, or to a suitable non-restrictive tubular connection having substantially the same diameter as the evaporator tubing or conduit, employing suitable means for plugging the space between the outer surface of the capillary and the inner surface of the evaporator inlet. With such a direct connection, the refrigerant in the form of either a liquid or a gas or mixture thereof issued from the outlet end of the relatively small capillary at a relatively high velocity close to sonic speed. Also as this refrigerant exited from the capillary tube to the larger diameter evaporator conduit operating at compressor suction pressures, some of the liquid refrigerant flashed into gas at this lower pressure resulting in a turbulent and noise producing flow at the inlet to the evaporator. This noise may be described as a roaring sound, accompanied in some cases believed to result from the use of a condenser which alternately feeds gas and liquid slugs to the capillary, by a relatively loud popping sound similar to that of popping corn.

Both the roaring noise and the popping noise are substantially eliminated in accordance with the present invention by employing a connector between the capillary outlet and the evaporator inlet which in its preferred form comprises a plurality of telescoping tubular segments or sections, the first of which has an inner diameter approximately equal to the outer diameter of the capillary and each succeeding section bearing a similar relationship to the preceding one. Generally commercially available refrigerant tubing of various sizes can be employed in manufacturing the connector.

For optimum results, the effective lengths of the individual segments or sections of the connector are such that the connector provides a gradual transition from the inner diameter of the capillary to the inner diameter of the evaporator inlet. To this end, at least three tubular sections or in other words three steps in the expanding connector are required for the desired suppression of the above mentioned noises.

Also, for best results, the wall thicknesses of all the segments or sections are substantially equal and this criterion is satisfied by the fact that most commercially available refrigerant tubing within the range of sizes employed for making the connector have about the same wall thicknesses.

Broadly described, the lengths of the individual segments or sections are selected to provide an increase in the cross sectional area of the connector from capillary to the evaporator inlet at a logarithmic rate with the lengths of the successive segments being determined by the formula X log N +1 where X is a multiplier between 8 and 12, preferably 10, and N is the number of the section in the connector. In other words, the lengths of the segments of the connector are successively determined by the progressive formulas X log 2; X log 3; X log 4; etc.

In accordance with the above equations, the value of X determines the average rate of increase in cross sectional area within the connector. Tests have indicated that if X is a number substantially less than 8, there is no substantial elimination or repression of the roaring and popping noises whereas if X has the value greater than 12 the rate of increase in the effective cross sectional area of the connector is so gradual that the first section or sections of the connector effectively increase the capillary length and hence result in an undesirable increase in the pressure differential between the high and low pressure sides of the system.

A typical example of a preferred connector for the practice of the present invention is illustrated in FIG. 2 of the drawing. This connector was designed to provide an optimum noise suppression with substantially no increase in back pressure in a system comprising a capillary tube having an exterior diameter of about 0.125 inch and an evaporator inlet having an exterior diameter of 0.375 inch and an interior diameter of 0.319 inch. Each of the segments employed in manufacturing this connector had a will thickness of about 0.028 inch or in other words a difference of about 0.056 inch between the inner and outer diameters thereof. More specifically the first section 8 had a A outer diameter, the second section 9 a A1" outer diameter and the third section 10 an outer diameter of The exterior diameter of the third section was such that it approximately matched the interior diameter of the evaporator inlet 6.

Employing the above formula with X equal to the preferred multiplier 10, the effective lengths of the individual segments (with the insertion depth of each segment into a succeeding segment being extra), were as indicated on the drawing. The first segment 8 was 3" in length, the second segment 9 was 1.75 in length and the third segment 1.2" in length.

This connector has been extensively employed in a room air conditioner system and has substantially suppressed or eliminated all of the capillary-evaporator joint noise. It is easily manufactured merely by soldering or brazing the overlapping portions of the respective segments. The ledges or steps formed by the outlet end of each of the segment do not appear to provide any significant noise problem presumably because the refrigerant flows through the connector in such a manner that its boundary layers tend to smooth out these irregularities.

In manufacturing some connectors, it may be advantageous to manufacture some adjacent segments from a single piece of tubing as for example by swagging a portion thereof to a smaller diameter. Such a connector is shown in FIG. 3 in which the first two segments 11 and 12, corresponding to segments 8 and 9 of FIG. 2, are made by reducing the cross sectional area of a piece of tubing having the internal diameter of the section 12 to a smaller diameter section 11.

It has also been found that the subject connector is particularly useful for solving field complaints concerning abnormal refrigerant noises in air conditioning systems.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a refrigeration system including a condenser, an evaporator having a tubular inlet and a tubular flow restrictor for controlling the fiow of refrigerant from said condenser to said evaporator and having a flow restriction sufficient to maintain the desired range of pressure differ ential between said condenser and said evaporator;

means for connecting the outlet end of said flow restrictor to said evaporator inlet;

said connecting means comprising at least three successive tubular sections of progressively increasing diameters and decreasing lengths from said flow restrictor to said evaporator inlet for reducing the noise generated by the refrigerant flowing from said flow restrictor;

the effective lengths of said sections being determined by the formula X log N +1 wherein X is a number between 8 and 12 and N is the number of the section in said connector.

2. The system of claim 1 in which the wall thickness of said sections are each substantially equal to the Wall thickness of said flow restrictor.

3. The system of claim 1 in which X is equal to approximately 10.

References Cited UNITED STATES PATENTS 2,434,118 1/1948 Newman 62--5l1 MEYER PERLIN, Primary Examiner