US3587245A - Air conditioner with receiver in accumulator - Google Patents

Abstract

IN THE PREFERRED FORM, THE REFRIGERANT CIRCUIT IS PROVIDED WITH A RECEIVER PRECEDING THE CAPILLARY TUBE RESTRICTOR WHICH IS LOCATED WITHIN THE ACCUMULATOR AT THE OUTLET OF THE EVAPORATOR FOR PRECOOLING THE LIQUID REFRIGERANT TO SUSTANTIALLY PREVENT ELECTROSTATIC PRECIPITATION IN THE CAPILLARY TUBE RESTRICTOR.

Description

United States Patent [56] References Cited UNITED STATES PATENTS 6/1946 Carter..........................

[72] Inventor James W. Jacobs -Dayton,0hio 211 AppLNo. 808,097

2,740,263 4/1956 Kritzer Primary Examiner-Martin P. Schwadron Assistant Examiner-P. D. Ferguson AttorneysWil1iam S. Pettigrew, Frederick M. Ritchie and [22] Filed Mar. 18,1969

[45] Patented June 28, 1971 [73] Assignee General Motors Corporation Detroit, Mich.

Edward P. Barthel 54 AIR CONDITIONER minimum in ACCUMULATOR ABSTRACT: In the preferred form, the refrigerant circuit is lClaim, 2 Drawing Figs.

' provided with a receiver preceding the capillary tube restrictor which is located within the accu mulator at the outlet of the evaporator for precooling the liquid refrigerant to substantially prevent electrostatic precipitation in the capillary tube restrictor.

[51] [50] FieldofSearch...................

PATENTED JUN28 um ATTORNFY AIR CONDITIONER WITII RECEIVER IN ACCUMULA'IOR It has been recognized that the commonly used refrigerants in air conditioning systems gradually form rough deposits within the capillary tube restrictors so that the refrigerant flow is gradually reduced during the life of the refrigerating system to gradually reduce its capability of producing cold. It has been recognized that this is a result of the streaming potential produced by the rapid flow of refrigerant vapor through the capillary tube restrictor which produces a streaming potential of the order of 10,000 to 100,000 volts which tends to make the capillary tube restrictor an electrostatic precipitator.

It is an object of this invention to precool the liquid refrigerant prior to its entrance into the capillary tube restrictor substantially to evaporator temperature so as to reduce the evaporation of the refrigerant and the formation of gas within the restrictor sufficiently to reduce the velocity of flow and substantially reduce the streaming potential and electrostatic precipitation within the restrictor.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

IN THE DRAWINGS FIG. I is a view partly diagrammatic of an air conditioning refrigerating system embodying one form of my invention; and

FIG. 2 is a fragmentary side view of the accumulator and receiver and the adjacent portions of the restrictor and evaporator shown in FIG. 1.

Referring now to the drawings, enclosed in an air conditioner cabinet 19 indicated in dot-dash outline, there is shown a sealed motor compressor unit 20 containing an electric motor and a compressor. The sealed unit 20 withdraws evaporated refrigerant through the suction conduit 22 and discharges the compressed refrigerant through the discharge conduit 24 which connects with the top of the vertically finned tubular condenser 26. This condenser is located in one end of the cabinet and is cooled by air circulated by the propeller fan 28 connected to the fan motor 30. The compressed refrigerant is thereby liquefied and flows to the bottom of the condenser from which it is conducted by the supply pipe 32 to a receiver 34 from which the liquid refrigerant flows through the capillary tube restrictor 36 to the bottom of the vertically finned tubular evaporator 38. The air to be cooled is circulated through the evaporator 38 by a propeller type fan 40 which may draw air from the sides and bottom and top and discharge the air through the evaporator 38. The circulating air causes the evaporation of the refrigerant which flows upwardly through the evaporator to the accumulator 42 in the outlet portion of the evaporator. The top of the accumulator connects to the suction conduit 22.

It has been discovered that when air conditioning systems employing capillary tube restrictors and certain refrigerants operate under high temperature conditions for long periods of time that their cooling capacity is gradually reduced due to the accumulation of rough deposits adjacent the outlet portion of the capillary restrictor tubes. This appears to be the result of the streaming potential of l0,000 to l00,000 volts which may be generated by the high velocity of vapor flow in the capillary tube restrictor under such high temperatures and to electrochemical properties of refrigerants. Refrigerants having a conductivity between ohm"cm. and 2.0 l0"ohm cm. are prone to capillary deposit production. The precipitation is more severe for refrigerants having a conductivity between l0" and l0"ohm"cm.. Specific examples of refrigerants commonly used in air conditioning systems having the most severe problems of electrostatic precipitation are those known as R22 and R502. R22 is monochlorodifluoromethane (CHCIF and R502 is an azeotropic mixture of R22 and chloropentafluoroethane (CHClF lCclF CF According to my invention, I precool the liquid flowing to the entrance of the restrictor 36 substantially to evaporator temperature by obtaining high heat transfer between the cold refrigerant in the accumulator 42 and the warm liquid refrigerant in the receiver 34. This is done by locating the receiver 34 in the form of a relatively large tank substantially entirely within the accumulator 42 so that the receiver 34 and its contents are cooled by being surrounded by the cold refrigerant in the accumulator 42 which serves to keep the liquid refrigerant in the evaporator and facilitates the return of completely evaporated refrigerant through the suction conduit 22. The receiver 34 is located adjacent the bottom of the accumulator 42 so that it will be contacted and cooled substantially to evaporator temperature by any liquid refrigerant collecting in the bottom of the accumulator 42 and evaporating at the surfaces of the receiver 34.

This accumulator arrangement will aid in preventing any liquid refrigerant from entering the suction conduit 22 and returning to the sealed unit 20. The heat transfer may be further augmented by the use of any of the various forms of roughened or extended surfaces upon the receiver 34. The receiver 34 is shielded from the air circulated by the fan 40 by being enclosed in the accumulator 42 so that its content of liquid refrigerant is cooled to and maintained at a relatively low temperature during both the operating and idle periods of the apparatus substantially at the temperature of the evaporator 38. A relatively large amount of cooled liquid refrigerant normally accumulates in the receiver 34 under low pressure conditions in the condenser for normal release to provide increased cooling under high condenser temperature and pressure conditions.

As a result of this precooling of the refrigerant in the receiver 34 the amount of evaporation and the amount of vapor formed in the refrigerant is greatly reduced. Since the volume of the liquid refrigerant is very small (about one-sixtieth compared to the volume of evaporated refrigerant, the velocity of the refrigerant flow within the capillary tube restrictor is greatly reduced thereby greatly reducing the streaming potential and the electrostatic precipitation and the accumulation of deposits within the capillary tube restrictor.

In addition to placing the receiving 34 within the accumulator 42, as shown in FIG. I, the capillary restrictor 36 may be also bonded to the outside of the accumulator 42 and also to one or more passes or loops of the tubing of the evaporator 38 to provide additional heat transfer and cooling for the refrigerant in the capillary tube restrictor to maintain the refrigerant in a liquid state in the capillary tube restrictor to the greatest extent possible. Thus, by this large precooling of the liquid refrigerant in the receiver and also by the cooling of the capillary tube restrictor, evaporation is substantially diminished in the restrictor so that the velocity of flow and streaming potential are greatly diminished, thereby substantially reducing deposits in the capillary tube.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

Iclaim:

1. An air conditioner including a motor compressor unit, a condenser, a capillary tube restrictor constituting a major restriction to flow and a fin and tube evaporator connected in an operative refrigerant circuit containing a refrigerant capable of generating high streaming potential forming substantial objectionable deposits in the capillary tube restrictor wherein the improvement comprises providing the outlet portion of the evaporator with a large accumulator and a receiver extending within and being substantially surrounded by the accumulator in intimate heat transfer contact therewith, said receiver being connected between the outlet of said condensing means and the inlet of said restrictor for precooling the liquid refrigerant prior to its entrance into the restrictor tube, said evaporator comprising a refrigerant tube extending in heat transfer with a plurality of fins, said restrictor tube having a portion extending along and in direct heat transfer contact with a portion of said refrigerant tube which is provided with the fins to provide additional cooling of the refrigerant as it flows through the restrictor.

+29 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 587 245 Dated June 28, 1971 Inventor s) Iames H Ia b It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 64, "10 should read l0 "7 same line, "ohm should read ohm same line, "cmshould read cm same line, 2;.0 x 10 should read same line, "ohm should read ohm line 67, "10 should read 1o" same line, "10 should read 10 --7 same line, "ohm should read ohm same line, "cm. should read cm same column 1, line 65 "cm. should read cm Signed and sealed this 22nd day of February 1972.

(SEAL) Attest:

EDWARD M.FLE'ICHER,JR. ROBERT T HALK Attesting Officer Commissioner of Patents

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