US2158403A - Refrigeration system - Google Patents

Description

May' 16, 1939.

J. R. CHAMBERLAIN REFRIGERATION SYSTEM Filed Nov. 2'7, 1957 (Ittornegs Patented May 16, 1939 .UNITED STATES REFRIGERATION SYSTEM Joseph R. Chamberlain,

York, Pa.; assignor to- York Ice Machinery Corporation, York, Pa., a corporation of Delaware Application November 27, 1937, Serial No.'178,866

Claims.

This invention relates to refrigeration systems and particularly to systems of the compressorcondenser-expander type.

In refrigerating systems of this type and par- 6 ticularly as applied to commercial installations, it is; common practice for reasons of efficiency and convenience to locate the compressor unit in the basement of a building to be refrigerated, and the condensing unit on the roof or at some other 4 elevated point where unobstructed air simulation can be obtained. The condensers frequently take the form of a cooling tower-condenser in which water is continuously showered over the condenser coil, preferably countercurrent to the circulation of air over such coil. Installations of this kind are subject to protracted standby periods over week ends or holidays when the apparatus remains idle. The condenser unit and the compressor unit are subject to the widely different temperatures of a relatively cool basement and the relatively ,warm outside air. When'the system .is idle, especially in warm weather, the vapor pressure of refrigerant in the condenser will be substantially greater than the vapor pressure of refrigerant in the discharge line leading from the compressor to the condenser, since there is free communication between them. Evaporation willtend to occur in the condenser or condensation will tend to occur in the discharge line adjacent the compressor. If the condition persists long enough, the liquid in the receiver will evaporate and the vapor will flow backwards through the condenser unit and ultimately condense in the discharge line. and find its way to the compressor.

The object of the present invention is to so modify existing apparatus that condensed refrigerant'can never reach the compressor, and to accomplish this by providing a liquid sump in the line between the condenser and the compressor, and of suflicient' capacity to receive and hold all .refrigerantwhich can ever condense in this lineunder any conditions. It is further proposed to so locate therefrigerant sump that when the sys- {5 tem is'restarted after a shut-down, it will resume its normal operation quickly and safely, and will continue to operate as it would if the safety sump werenot present. I .Other. objects will be apparent from the specification. I ln th'e drawing the single figure is-a diagrammatic view 9f one form of apparatus embodying the present invention, and showing the construction-of the compressor and its associated refrig- 55 erant'sump v r Referring to the drawing, reference character 5 designates the outline of a building having a compressor unit C located in the basement, a condenser unit D located on the roof, and an evaporator unit E inside of the building, the 5 ground line being indicated at G. The compressor unit comprises the usual. base 6 having, mounted thereon a compressor 1 and a driving motor 8. The base also houses a tank or refrigerant sump 22. The-condenser unit comprises an 1 enclosing casing 9 containing a condenser coil ll associated with a liquid receiver l2, and a water circulating pump l3 for showering cooling water from pipe l4 over the coil. This unit pref:

erablyincludes an air circulating fan having an outlet l5 whereby evaporation of the cooling wa 'ter is increased, and the cooling effect of the condenser is thus enhanced. The receiver l2 is connectedby pipe I 6 to the evaporator E through an expansion valve H, which may be controlled by a heat sensitive bulb l8 associated with the line I9 connecting the outflowend of the evaporator E to the low pressure side of the compressor.

In the usual construction of systems of this type, the high pressure side of compressor 1 would be connected directly to the topside of the condenser coil H so as to convey hot compressed gas directly from the compressor to the condensrer. In the present instance, however, the pipe 2| leading from the high pressure side of the compressor passes to the refrigerant sump 22 having at its bottom an offtake pipe 23 connected to the intake of condenser coil II. The sump 22 has a capacity sufljcient to hold the volume of refrigerant which may, under any conditions, condense between the compressor and condenser. Use of' a compressor unit in this way simplifies the apparatus and makes it possibleto use a single type of compressor unit interchangeably either in a system of the present type, where tank 22 serves as a refrigerant sump, or in a refrigeratingsystem .where this tank serves as a refrigerant condenser and receiver. The normal operation of the system is the same as that of usual practice. Briefly stated, evaporated refrigerant coming from the evaporator E to the intake of compressor I, is compressed and passes through pipe 2|, sump 22 and line 23 to condenser- II, where it comes into heat exchanging relation through the walls of the condenser coil with the relatively cool water flowing 'over this coil and with the air which is circulating over thiscoil. As the gas passes downwardly through the coil toward the receiver I2, .it' gradually loses heat until it liquefies and collects in the receiver l2, whence it flows through pipe l6 and expansion valve I! to evaporator E in liquid form. The expansion valve I1 is shown as of the automatic or thermally controlled type, in which a thermostatic bulb IB regulates the expansion valve in conjunction with the pressure and temperature on the discharge side of the valve. The thermostatic bulb being placed on the suction line IS, the valve operates to insure that the refrigerant is slightly superheated in the suction line, a con-- dition which guards against the flow of liquid refrigerant from the evaporator to the compressor. However, the invention is not limited to any particular type of expansion valve, and other conventional mechanisms, such as, particularly, low side float valves, might be used exactly as they are used in current practice. v

The operation just described is standard practice in refrigeration systems of the type to which this invention relates. The operation of such systems, so long as there are no standby periods. is thoroughly satisfactory with known types of structure and without the interposition of the refrigerant sump 22. When, however, the apparatus is shut down for comparatively long periods, the widely different temperature conditions existing at the condenser coil II and in the basement where the compressor 1 is located, cause a great difference in vapor pressure between the compressor and the condenser. When the apparatus shuts downfsome liquid refrigerant willalways be present in the receiver l2 where it becomes subject to gradually increasing temperature and vaporizes as the temperature of the condenser coil H rises, since there is no circulation of cooling water within the casing 9. While the temperature of the condenser coil H rising, the temperature Within the cool basement remains substantially the same, so that the vapor pressure differential at the two ends of pipe'23 eventually increases to the point where refrigerant condenses in the line and collects in the sump 22.

During operation of the system the compressor, as well as the sump and discharge line, become relatively hot. The compressor is composed of a comparatively heavy mass of metal whereas the sump and discharge line are made of lighter and thinner metal having less heat storing capacity than the compressor. Consequently, when the system is shut down and cools off, the sump and discharge line cool to ambient temperature much more quickly than the compressor. When, therefore, condensate starts to flow back through'the discharge line from the condenser, before the entire system has had time to cool down, it will go to the coldest point in the system, namely to the sump, and will remain there in liquid form without any tendency to pass to the warmer compressor. In this way it is assured that the condensed refrigerant will collect in the sump and not in the compressor.

This condensation may continue until the entire volume of refrigerant present between expansion valve H on the condenser side, line l6, receiver 12, condenser coil II and line 23, i. e., in the high side of the system, has condensed and collected in the sump 22. For absolutesafety it is preferred to make this sump of a volume sufficient to hold the entire charge of liquid refrigerant in the system, but the essential requirement is that it be large enough tohold all liquid which could condense under the most extreme condition to which the system could ever be subject. In most systems, and with a sufficiently protracted standby period under the conditions noted, this liquid volume might approximate the entire charge. Consequently, with the arrangement illustrated, there can never be any danger of the compressor head being blown off by reason of its starting up with liquid refrigerant present 'in the cylinder. The operation of the sump 22 is effective regardless of the length of standby periods, and it is immaterial whether the entire volume or only a part of the refrigerant condenses therein.

When the system is started up, after a standby period in which liquid has collected in the sump 22, the compressorstarts immediately to compress the gas coming from line l9, and to force it under pressure into the sump 22, where it displaces the condensed refrigerant liquid inthe sump, and sends it through the line 23 to the condenser II. All of the liquid in sump 22 is displaced before any gaseous refrigerant can flow from the compressor to the condenser. Refrigeration is obtainable almost immediately after the compressor starts, because the condensed refrigerant is sent to the evaporator quickly.

In the example given, the refrigerant sump 22 has been illustrated as located in the compressor base for reasons of convenience, although it will be understood that it may be placed in otherlocations and still bring about the result which is here obtained. The essential point is that the sump be of a capacity, and be so located in the line between the off-take of the compressor and the inlet of the condenser, that no condensed refrigerant can ever reach the compressor under any conditions to which the system may be subjected.

- The system shown herein is merely by way of illustration as it is obvious that the inventive concept may be applied to other known types of system where, as a result of temperature differences between the compressor and condenser units, this-problem of refrigerant condensation during standby periods may appear.

I claim:

1. In a refrigeration system, a compressor for gaseous refrigerant: an evaporator; a condenser connected between the compressor and said evaporator for condensing the gaseous refrigerant and supplying it to said evaporator in the form of a liquid, said condenser being subject to a temperature differing substantially from that of the compressor; and a refrigerant sump subject to substantially the same ambient temperature as the compressor, interposed in the high pressure side of the system between said compressor and condenser for receiving. refrigerant condensed from the system during standby periods and preventing it from reaching the compressor.

2. The combination with a refrigerating circuit including a compressor, a condenser, and an evaporator, of a liquid trap connected between the compressor and the condenser, said trap being subject to an ambient temperature substantially different from that of said condenser but approximating that of said compressor and so arranged that refrigerant tending to flow in vapor form from the condenser and to condense adjacent the compressor during standby periods, will be collected in said trap and displaced therefrom to the condenser, by pressure developed as an incident to the resumption of operation of the compressor.

3. In a refrigeration system, a compressor for gaseous refrigerant; an evaporator; a condenser connected between the compressor and evaporator for condensing the gaseous refrigerant and supplying it to the evaporator in liquid form, said condenser being located at a different level from that of the compressor and being subject to a temperature differing materially from that of the compressor; and a liquid trap connected between the compressor and the condenser, said.

trap being so arranged that refrigerant tending to flow in vapor form from the condenser so as to condense adjacent the compressor during standby periods, will be collected in said trap and be displaced therefrom to the condenser by pressure developed as an incident to the resumption of operation of the compressor at the conclusion of a standby period.

4. In a refrigeration system, a compressor unit comprising a hollow base having a tank disposed therein; a compressor mounted on said base; a motor mounted on said base and operatively connected to drive said compressor; a condenser unit located at a point remote from said compressor and subject to a substantially different ambient temperature than that of the compressor; an

evaporator connected between the condenser and the suction side of the compressor; and means for connecting said tank in circuit between said condenser and the high pressure side of said compressor to cause refrigerant tending to flow in vapor form from the condenser and to condense adjacent the compressor during standby periods, to be collected in said tank and displaced therefrom to the condenser by pressure developed as an incident to the resumption of operation of the compressor after a standby period sufiicient to cause condensation of refrigerant in said tank.

5. The combination with a refrigerating circuit including a compressor, a condenser and an evaporator, of a liquid trap connected between the compressor and condenser and subject to ambient temperature conditions approximating those of said compressor, but difiering substantially from those of said condenser, said trap having less heat storing capacity than the com pressor,-and being so arranged that refrigerant tending to flow in vapor form from the condenser and to condense adjacent the compressor during standby periods will collect in said trap.

JOSEPH R. CHAMBERLAIN.

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