US2291363A - Refrigerant evaporator - Google Patents

Description

July 28, 1942.'V

L. W. ATCHYISON REFRIGERANT EVAPORATOR v Filed Aug. l, 1941 Inventor" Leonard W Atchison,

by?el His Attorney.

Patented July 28, '1942 REFRIGERANT EVAPoRA'roR Leonard W. AtchisonQSchenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 1, 1941, Serial No. 404,963

9 Claims.

My invention relates to refrigerant evaporators and particularly to such evaporators having continuous vaporizing conduits supplied by expansion devices of the fixed restricted opening type.

Evaporators of a continuous or series coil type tend to accumulate liquid in the lower portions of the coil during the inactive periods of-the cycle of operation of the refrigerating machine. The cooled liquid may forin slugs which pass to the compressor when the machine is restarted and it is necessary to provide some arrangement for trapping the slugs and preventing their reaching the compressor where they might cause damage. When a capillary tube or other expansion device of the fixed restricted opening type is employed, a considerable quantity of liquid refrigerant may beA collected in the condenser or liquid receiver at the time the compressor is stopped and this liquid refrigerant will continue to flow to the evaporator and a large proportion of this liquid may flow to the trap atthe end of the evaporator and be collected therein. When the machine is restarted a substantial period of time is necessary before the iiow of liquid refrigerant from the condenser is adequate to wet the entire interior surface of the evaporator coil, and a considerable portion of the coil, therefore, may have no liquid refrigerant in it which is available for immediate refrigeration when the compressor is started. Accordingly it is an object of my invention toprovide a refrigerant evaporator of the continuous coil type including an improved arrangement for assuring the presence of liquid refrigerant in a substantial portion of the evaporator as soon as the operation of the compressor is resumed after an inactiveperiod during the refrigeration cycle.

Another object of my invention is to provide a refrigerant evaporator including a liquid vaporizing portion and a liquid and gas. separating header and an improved arrangement for preventing the ow of liquid refrigerant from the header into the` suction line during the inactive period when the compressor is stopped during the refrigeration cycle.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. 1 is a side elevation partly in section of a household refrigerator provided with a refrigerating machineincluding lan evaporator embodying my invention; Fig. 2 is an enlarged perspective rear view of the evaporator shown in Fig. l; Fig. 3 is an enlarged sectional side elevation of the header in theside wall of the evaporator shown in Figs. land 2; and Fig. 4 is an enlarged side elevation of the outlet header of the evaporatorshown in Figs. 1 and 2.

The evaporator shown in the drawing cornprises generally a sheet metal structure providing the side and bottom walls of a freezing compartment and having arranged therein two continup ous refrigerant vaporizing conduits connected in series by an intermediate header, the first conduit being supplied with refrigerant from a capillary tube expansion device and refrigerant being withdrawn from the other conduit and entering a second header. A refrigerated shelf is provided which is cooled'by a flooded conduit communicating at both ends with the second header and vaporized refrigerant is withdrawn from the evaporator by a suction line which opens in cornmunication with the upper portion of the second header. The intermediate header serves as a liquid trap between the two conduits, the second conduit being provided with a gooseneck or bowed portion extending downwardly within the header and having its open end communicating with the upper portion of the headerf'A restricted aperture in the bottom of the bowed portion near the bottpm of the header is employed to meter liquid refrigerant from the header into the second conduit and another restricted opening is provided at the end of the bowed portion near the outlet of the header at about the same level as the open end of the bowed portion so that during the inactive period of the refrigeration cycle the pressures in the two conduits will be substantially equalized and liquid refrigerant will be trapped in the intermediate header. The suction line is provided with a similar bowed portion in the second header. This bowed portion is also'provided with two restricted apertures in.

similar positions tol those in the bowed portion of the conduit in the intermediate header. However the restricted opening for metering liquid refrigerant into the suction line is arranged at or near the normal level of liquid refrigerant in vthe second header rather than at the bottom' of the header. During the foff period'of the refrigeration cycle liquid refrigerantwhich continues to flow from the-condenser and through the capillary tube will pass through the rst conduit into the intermediatefhea'der where it win be trapped, since the pressure in the header and inthe second conduit is substantially equalized so that only a small ow of gaseous refrigerant continues through the upper restricted aperture. When the refrigerating machine is again started the liquid refrigerant in the intermediate header flows into the second conduit and, thus, is immediately available to produce refrigeration in a substantial portion of the evaporator.

Referring now to the drawing, in Fig. 1 I have shown a household refrigerator comprising an insulated cabinet I having a door II and a food compartment I2. The food compartment is cooled by an evaporator or vaporizing `unit I3 connected in the refrigerant circuit of a refrigerating machine comprising a hermetically sealed motor-compressor unit I4 and an air cooled condenser I5 mounted on the back of the cabinet III. The compressor unit I4 is mounted in a machinery compartment below the food compartment I 2 and insulated therefrom by a 'bottom wall of the compartment I2` (not shown). D ur` ing the Loperation off the refrigerating machine liquid refrigerant withinthe evaporator I3 absorbs heat from the compartment I2 and is vaporized and the vapor is withdrawn from the evaporator through a suction line I6 by operation of the compressor in the unit I4. The compressor compresses the withdrawn vaporized refrigerant and discharges it through a connection II to thecondenser I5. The hot compressed refrigerant is cooled and liquefied in the condenser by the natural circulation of air over the outside *surface thereof; The liquid refrigerant is deliv-v ered 4to the evaporator through a capillary tube I8, the major portion of which is secured to the suction line in heat exchange relation therewith. The capillary tube `maintains a predetermined pressure diiferencebetween the condenser and evaporator and determines the rate of flow of the refrigerant. When the operation of the Vcom` pressor in the unit I4 is stopped, any liquid refrigerant remaining inthe condenser will continue to flowto the evaporator through the capillary tube until pressure equilibrium is reached.

'Ihe constructionand arrangement of the evap- Y:orator I3 is clearly shown in Fig. 2. The evaporator comprises a rectangular metal sheet I9 lbent, into U-shaped form and provided with flanges 2|)` and 2I for securing the evaporator to the top plate or inner liner of the refrigerator cabinet. On the sheet I9 are provided a section of conduit 22 and a section of conduit 23 connected in series by a header 24 to forma continuous refrigerant vaporizing passage. The conduits and the header ane formed in any 'suitable manner and are arranged in-good heat exchange relationship with lthe sheet I9 and preferably are secured to or formed on the sheet while it isv flat and are then bent with the sheet to form the U-shaped evaporator as shown'. The conduit 22 is arranged adjacent the edgesof the sheet I9 and the conduit 23 extends back and forth across the sheet Awithin the area enclosedby the conduit 22. Liquid refrigerant from the capillary tube I9 enters the conduit 22 and flows around the edges of the sheet and thence into the upper portion of the header 24.

thence back and forth from one wall of the evapo'rator to the other across the lbottom Wall and thence into the top of aheader 25 which extends across the back of the evaporator at the top thereof and is secured to the side walls by flanges 26 and 21. A shelf 28 is secured to the From the header 24 the' refrigerant flows into the conduit 23 and lll side walls by flanges 29 and 30 and extends across the freezing compartment formed by the sheet I9 about midway between the top and bottom thereof. The shelf is cooled by sinuous conduit 3I having its ends 32 and 33 opening into the bottom of the header 25 below the level of liquid refrigerant thereinso that the conduit 3I is maintained floodedv with liquid refrigerant. Refrigerant vaporized in the evaporator is Withdrawn from the header 25 through the suction line I6. 'I'he U-shaped portions`of thel conduits 22` and 23 `tend to trap liquid refrigerant in their lower portion during the off period of the refrigerant cycle. `However with the continued admission of the refrigerant to the evaporator during the "off period liquid refrigerant tends to flow out of the conduits .so that when the operation of the compressor isresumed subrefrigeration of the walls of the evaporator may therefore result. In order to provide refrigeration throughout'the conduit 23 when operation.

of the compressor lis resumed, I construct the header 24 so that it acts as a yliquid trap.during the offfperiodiof the-cycle and so that it supplies liquid refrigerantto the conduit 23 as soon Y as the compressor is started. As shown in Fig. 3,

the conduit V'23 is provided with a bowed extension or gooseneck 34.forming a portion of theA conduit within the header 24. The extension 34 has its open end 35 in direct communication with the upper portion of the header 24 and the lowermost portion of the extension Vliesat the bottom vof the header 24. Conduit 23 constitutes a suction line with respect to 'thefrst portionof vthe evaporator comprising the conduit 22 .and the header 24 and ,during the` normal-withdrawal ofr refrigerant from the header 24 gaseous refrigv erant flows from the headerthrough the opening 35` and vliquid refrigerant flows through a restricted aperture 36 near the bottom of the bowed portion which meters the flow of liquidrefrigf erant. A small amount of gaseous refrigerant also entersthe con-duit 23 through a restricted opening 3`Iin the upper portion of the extension 34 at about the same level as the open end thereof. A continuous supply ofr liquid and vaporized refrigerant is therefore admitted rto the conduit 23 during the active portion of the refrigerating cycle. When the withdrawal ofvaporized refrigerant is stopped by the stopping of the compresser the pressures inthe header 24 -f and in theconduit 23 are substantially equalized by the flow of vaporized refrigerant through the restricted opening 31," Liquid refrigerant, which continues to enter the h eaderg24 from the conduit 22 because of the. continued supply of liquid refrigerant ythrough the capillary tubeY I8, col-l Y lects in the header` 24, extension 34 filling with liquid refrigerant to the level ofthe liquid refrigerant in the header. As `soon as the operation of the compressor is` resumed the pressure the header 24 continues to flow through aperturek y y 36 and supply liquid `refrigerant tothe conduit 23.

frigerant for the conduit 23 for a considerable period of time before `sufficient liquidv refrigerant is supplied through the capillary tube Il This provides a supply of liquid re,`

to reach the conduit 23. Active refrigeration is therefore obtained in the conduit 23 much sooner than would be possible if it were necessary to wait untilan adequate supply .was available from the capillary tube. The liquid and gaseous refrigerant separate in the header 25 and the vaporized refrigerant is withdrawn from the header through the suction line I6. In order to provide a quiet zone of liquid refrigerant within the header 25 and `prevents slugs of liquid from entering the suction line, two baffles 38 and 39 are provided between the ends 32 and 33, respectively, of the conduit 3| and the suction line I6. Baffles 38 and 39 do not extend entirely across the header 25 but provide communication between the ends and the central portion of the header both above and below the normal level of liquid refrigerant. The suction line 4I6 is provided with a bowed extension or gooseneck 40 within the central portion of the ,header 25, the open end of the extension communicating with the top central portion of the header. A restricted orifice 42 is provided in the extension 4l in order that small amounts of liquid may be metered from the header into the suction line. This is necessary in order that oil or other lubricant which is unavoidably entrained in the refrigerant discharged from the compressor may bei returned to the compressor. If the lubricant 4and 'liquid refrigerant separate by gravity only oil from the surface of the liquid in the header need be removed through the orice 42; however, if the lubricant is intimately mixed or dissolved in the liquid refrigerant, it is necessary to withdraw small amounts of the mixture of liquid refrigerant and lubricant and to separate the lubricant from the liquid refrigerant before the mixture reaches the compressor. This separation is accomplished in the heat exchanger since the liquid mixture will absorb heatfrom the hot liquid in the capillary tube, which is in heat exchange with the suction line, and the liquid refrigerant will thereby be vaporized leaving the oil which is carried with the vaporized refrigerant to the compressor. The extension 40 is also provided with a restricted aperture 43 which operates to equalize pressures in the same manner as the aperture 31 in the extension 34 in the header 24, thereby preventing the flow of quantities of liquid into the suction line during the inactive period cf the refrigeration cycle.

During the operation of the refrigerating machine described above the conduit sections 22 and 23 act -as a continuous refrigerant conduit during the active portion of the refrigerating cycle, Liquid and gaseous refrigerant, fiowing continuously through the section 22 and into the section 23 and thence to the header 25; and the conduit 3l in the shelf 28, is maintained flooded with liquid refrigerant since the header 25 is normally about half filled with liquid refrigerant. During the ofi period of the cycle liquid refrigerant collects in the header 24, and, even if all the liquid refrigerant should flow from the conduit 22 into the header and no more liquid be supplied to the conduit 22, nevertheless, there will be available a substantial quantity of liquid refrigerant for supplying refrigeration in conduit 23 as soon'as the compressor is again started. The arrangement of the extension 40 of the suction line I6 prevents the flow of liquid refrigerant to the suction line I6 even though an abnormal quantity of liquid refrigerant should enter the header 25 during the off period ofl the cycle. Furthermore the aperture 42 in the exand I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

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

1. An evaporator for a refrigerating machine comprising a liquid vaporizing section and a header in communication therewith, a connection for admitting liquid refrigerant to said vaporizing section, and a suctionconduit entering said header and opening into the upper portion thereof and having a portion extending .K

downwardly in said header, said conduit having two restricted apertures therein the first at substantially the same level as the open` end of said conduit and the second adjacent the lowermost part of said downwardly extending portion, said restricted apertures being so located that liquid refrigerant is metered into said suction conduit through said 'second aperture during the normal withdrawal of vaporized refrigerant and so that the pressures of vaporizedrefrigerant within said header and within said suction conduit are substantially equalized through said first aperture regardless of the accumulation of liquid refrigerant in said header during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator.

2. An evaporator for a refrigerating machine comprising a liquid vaporizing section and a header in communication therewith, a connection for admitting liquid refrigerant to said vaporizing' section and a suction conduit entering said header and opening into the upper portion thereof and having a bowed portion extending downwardly in said header, the lowermost part of said bowed portion being arranged adjacent the bottom of said header, said conduit having two restricted apertures therein the first at substantially the same level as the open end cf said conduit and the second in said lowermost part of said bowed portion, said restricted apertures beingv so located that liquid refrigerant is metered into said suction conduit through said second aperture during the normal withdrawal of vaporized refrigerant and so that the pressures of vaporized refrigerant within said header and within said suction conduit are substantially equalized through said first aperture regardless of the accumulation of liquid refrigerant in said header during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator.

3. An evaporator for a refrigerating machine comprising a liquid vaporizing conduit and a header in communication therewith,l an expansion device of the fixed opening type for admitting liquid refrigerant to said conduit, said conduit being arranged in series between said expansion device and said header, and a suction conduit entering said header and opening into the upper portion thereof and having a bowed portion extending downwardly in said header, the lowermost part of said bowed portion being arranged adjacent the bottomof said header, said suction 4 i f l, 2,291,363

conduit having two restricted apertures therein the first at substantially the same level as the open end of said conduit and the second in said lowermost part of said bowed portion, said restrictedapertures being so located that liquid refrigerant is metered into said suction conduit throughisaid second aperture during the normal withdrawal of vaporized refrigerant and so that the pressures of vaporized refrigerant within said header and within said suction conduit are substantially equalized through said rst aperture regardless of the accumulation ci liquid refrigerf-y to those in said suction connection for preventing the iiow of liquid from said second header except during the normal withdrawal of'vaporized refrigerant through said suction conduit and for metering the iiow of liquid fromr said second l header to said suction conduit during the normal 'Y withdrawal of vaporized refrigerant;

most part of said downwardly extending portion,

said restricted apertures being so located that liquid refrigerant is metered into said suction connection through said second aperture during the normal withdrawal of vaporized refrigerant and so that the pressures of vaporized refrigerant withinsaidheader and within said suction connection are substantially equalized through said first-aperture regardless of the accumulation of liquidV refrigerant in said header during the inactive period when vaporized refrigerant *is not being withdrawn from the evaporator, a

Suction conduit for removing vaporized refrigerant from said evaporator and a second vaporizing conduit connected in series between said suction connection and said suction conduit for vaporizing liquid refrigerant withdrawn from said header. Y

5. An evaporator for a refrigerating machine comprising a liquid vaporizing section and a header in communication therewith, a connection for admitting liquid refrigerant to said vaporizing section, a suction connection entering said header and opening into the upper portion thereofk and havingl a portion extending downwardly in said header, said connection having two re-v stricted apertures therein the first at substantially the same level as the open end of said connection and the second adjacent the lowermost part of said downwardly extending portion said restricted apertures being solocated that liquid refrigerant is ymetered into said suction con`- 6. An evaporator for a refrigerating machine comprising a liquid vaporizing conduit divided in two sections and having `a. header connecting the sections, a connection for admitting liquid refrigerant to the first ofsaid sections, the second of said sections entering said header and opening into the upper portion thereof and having aportion extending downwardly in said header, said* portion of said second section having two re-r stricted apertures therein'the vfirst at substantially the same level as theopen end of said section within said' header andthe second adjacent the lowermost part of said downwardly extending portion, and a suction connection for removing vaporized refrigerant from the said second section of said conduit, said restricted apertures being so located that liquid refrigerant is metered into said second section through said second aperture during the normal withdrawal of vaporized refrigerant from the evaporator andso that the pressures of vaporized refrigerant within said header and within said second section of said 'conduit are substantialy equalized through said rst aperture regardless of the accumulation of d liqud refrigerant in saidheader during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator, said header constituting a liquid trap and providing a supply of liquid refrigerant for said second section of said conduit immediatelywhen normal withdrawal of vaporized refrigerant is resumed.

'7. An evaporator for a refrigerating machine comprising a sheet metal wall structure vand means providing two extended refrigerant conbeing so located that liquid refrigerant is metered Y into said other conduit through said secondH nection through said second aperture during the normal withdrawal of vaporized refrigerant and so that the pressures of vaporized refrigerant within said header and within said suction connection are substantially equalized through said first aperture regardless of the accumulation of liquid refrigerant in said header during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator, a second vaporizing conduit connected to receive refrigerant from said suctionV connection and having a second header at its outlet end for separating liquid and vaporized refrigerant, a suction conduit for removing vaporized refrigerant from said second header and having a bowed portion extending downwardly within said second header and provided with restricted apertures similar duits arranged on the surface of said structure,

`a connection-for admitting liquid refrigerant to` one of said conduits, a connection for removing vaporized refrigerant from the other of said conduits and a header connectingsaid conduits in series, said other of said conduits having a pori tion entering said header and opening `into the upper portion thereof, said portion of said other conduit being bowed downwardly within said header and having two restricted apertures therein the first at substantially ythe same level as.

the open end of ,said portion of said other conduit and the second adjacent the lowermost part of said bowed portion, said'restricted apertures aperture during the normal withdrawal of vaporized refrigerant from said evaporator and so that the pressures of vaporized refrigerant within said header and within said other conduit are substantially equalized through said rst aperture regardless of the accumulation of liquid refrigerantv in said headerr during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator.

8..An evaporator for a refrigerating machine comprising a rectangular sheet metalstructure having two sections of a refrigerant vaporizing conduit arranged thereon, one` of said sections of conduit extending around the border ofv said sheet metal structure and the other of said sections extending back and forth across the facel of said sheet metal structure in the area within said one section of conduit, a header connecting said sections of conduit in series, a connection for admitting liquid refrigerant to one of said sections, a connection for withdrawing vaporized refrigerant from the other of said sections, said other of said sections having an end opening into the upper portion of said header, and having a bowed portion extending'downwardly within said header, said bowed portion having -two restricted apertures thereon the first at substantially the same level as the open end of said section and the second adjacent the lowermost part of said bowed portion, said restricted apertures being so located that liquid refrigerant is metered into said other section of conduit through said second aperture .duringthe normal Withdrawal of vaporized refrigerant and so that the pressures of vaporized refrigerant within said header and lwithin said other section of conduit are substantially equalized through said first aperture regardless of the accumulation of liquid refrigerant in said'header during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator.

9. An evaporator for a refrigerating machine comprising a rectangular sheet metal structure having two sections of a refrigerant vaporizing conduit arranged thereon, one of said sections of conduit extending around the border of said vsheet metal structure and the other of said sections extending back and forth across the face o1 said sheet metal structure in the area Within said one section of conduit, an elongated header arranged near one end of said sheet and substantially parallel to said one end connecting said sections of conduit in series, a connection for admitting liquid refrigerant to one of said sections, a connection for withdrawing vaporized refrigerant from the other of said sections, said other of said sections having an end opening into the upper portion of said header and having a bowed portion extending downwardly with said header, said bowed portion having two restricted v apertures thereon the first at substantially the same level as the open end of said section and the second adjacent the lowermost part of Asaid bowedportion, said restricted apertures being so located that liquid refrigerant is metered intov said other section of conduit through said second aperture during the normal withdrawal of vaporized refrigerant and so that the pressures of vaporized refrigerant'within said header and within said other section of conduit are substantially equalized through said iirst aperture regardless of the accumulation of liquid refrigerant in said header during the inactive period when vaporized refrigerant is not being withdrawn from the evaporator, said sheet metal structure being bent in U-shaped form to provide two side walls and a bottom wall, said header being arranged near the top of one of said side walls.

LEONARD W. ATCHISON.

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