US2934918A - Evaporator structure - Google Patents

Description

y 1960 D. A. SOLLEY, JR 2,934,918

EVAPORATOR STRUCTURE Filed Sept. 26, 1958 cacmcnc:

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INVENTOR.

HIS ATTORNEY DOUGLAS A. SOLLEY IR.

2,934,918 le Patented May 3, 1960,

EVAPORATOR STRUCTURE Douglas A. Solley, Jn, Fern Creek, Ky., assignor to General Electric Company, a corporation of New York Application September 26, 1958, Serial No. 763,529

2 Claims. (Cl. 62-523) The present invention relates to an evaporator structure for refrigerating systems and is more particularly concerned with an improved tube-in-sheet evaporator structure for household refrigerator and similar refrigerating systems.

In most household refrigerator systems, an accumulator is provided at the outlet end of the evaporator for the purpose of separating the liquid refrigerant from the vaporized refrigerant and for storing or accumulating the separated liquid while pivoting the refrigerant vapors to return through a suction line to the condensing unit. When the tube-in-sheet evaporators, that is, evaporators comprising a pair of metal sheets bonded together in faceto-face relation and providing between them refrigerant passages, are employed, it is common practice to provide adjacent the outlet end of refrigerant passage and as part of the tube-in-sheet structure an enlarged section which functions as an accumulator. The presently known processes for forming these tube-in-sheet evaporators comprises dilating or expanding the fluid or refrigerant passages including the portions of the passages forming the cumulator and means for preventing this liquid carry over of refrigerant from the accumulator into the suction line during operation of the evaporator.

A more specific object of the present invention is to provide a tube-in-sheet evaporator structure including an evaporator section and an accumulator section of the wafiie grid type and means forming part of the tube-insheet evaporator structure for bypassing a portion of the vaporized refrigerant around the accumulator and into the suction line in order to decrease refrigerant turbulence within an accumulator.

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

fication. I

In accordance with the present invention, there is provided' a tube-in-sheet evaporator structure including an evaporator section, a vertically arranged waffle-grid ac cumulator section. For preventing excessive turbulence in the accumulator and to obtain improved liquid-vaporization in the accumulator, means in the form of a substantially horizontal connecting passage between the evaporator and the accumulator and a vapor bleed line connecting this horizontal passage to the suction line leading from the accumulator are provided so that a substantial portion of the vapor flowing from the evaporator toward the accumulator is separated from the liquid refrigerant and bypassed through the vapor bleed line directly to the suction line.

accumulator section while the material is confined between spaced platens or dies in order to limit the expansion and thereby prevent rupture of the metal forming the tubular passages. This confined expansion process results in a flat walled accumulator section and in order to prevent these flat walls from bulging when the evaporator is subjected to the normal refrigerant pressures, the flat side walls forming the accumulator are normally secured together. at a plurality of spaced points. Due to the bonding at spaced points, the accumulator section is in effect composed of a plurality of intersecting horizontal and vertical tubular passages, and has the appearance of a wafile grid, which term will be used hereinafter and in the appended claims to refer to this type of accumulator provided in a tube-in-sheet evaporator structure and comprising a plurality of intersecting passages of sub stantially tubular form.

While these waffle grid accumulators possess a number of advantages due to their space-saving flat wall structure and the ease with which they can be formed as an integral part of the tube-in-sheet evaporator, it has been found that in a number of applications of tube-in-sheet evaporators including a wafile grid accumulator the accumulator is not as eflicient as an accumulator in the form of a single relatively large chamber for separating the vaporized refrigerant from the liquid refrigerent. Due to the relative small or restricted cross-sectional areas of the passageways forming the waffle grid accumulator, re-

frigerant gas entering the bottom of the accumulator and passing upwardly through the liquid contained therein causes considerable turbulence with the result that slugs of liquid are separated from the main body of liquid refrigerant and are carried upwardly through the re- For a better understanding of the invention reference may be had to the following description thereof when taken in connection with the accompanying drawing in which:

Fig. 1 is an elevational view of the tube-in-sheet evaporator structure of the present invention; and

Fig. 2 is an enlarged view, in section, of a portion of the evaporator structure of Fig. 1.

"Referring to Fig. 1 of the drawing, there is shown an evaporator structure of the tube-in-sheet type, the evaporator structure comprising a sheet 1 having formed therein and integral therewith a plurality of refrigerant passages including an evaporator section 2, which may be in serpentine tubular form and which covers most of the evaporator sheet 1 and a waffie-grid accumulator section 4 which is arranged to receive from the evaporator section 2 a mixture of liquid and gaseous refrigerant and to effect separation of the two. It is to be understood that an evaporator structure of this type forms part of a refrigerating system including a compressor and a condenser (not shown) whereby condensed refrigerant is introduced from a capillary fiow restrictor or the like into the evaporator inlet 5 and gaseous or vaporized refrigerant from the accumulator 4 is returned to the compressor through the outlet or suction line 6.

During operation of a refrigerating system including an evaporator of this type, refrigeration is obtained by the evaporation of a substantial portion of the liquid refrigerant as it fiows through the serpentine evaporator section 2 the proportion of gaseous refrigerant to liquid refrigerant is increasing as the refrigerant approaches the outlet end 8 of the evaporator section.

In order to prevent the turbulence which normally results in a wafiie-grid evaporator 4 due to the injection of a relatively large amount of gaseous refrigerant into the bottom of the accumulator, means are provided in accordance with the present invention to separate the gaseous refrigerant from the liquid refrigerant before it reaches the accumulator and to bypass most of the gaseous refrigerant around the accumulator. To accomplish these ends the evaporator section 2 is connected to the bottom portion of the accumulator 4 by means of a substantially horizontal connecting passage 9 which permits the mixture of gaseous and liquid refrigerant flowing from the evaporator outlet 8 to separate by slip flow with the result that the liquid refrigerant flows as indicated by the numeral 10 along the bottom of the passage 9 as indicated in Fig. 2. Preferably, the passage 9 as indicated in Fig. 2. Preferably, the passage 9 is of a cross-sectional area somewhat larger than that of the evaporator passages. Further, in order to prevent the gaseous refrigerant above this liquid stream it from entering the aecumulator 4 there is provided a bypass or vapor bleed line 11 connecting the passage 9 ate point removed from the evaporator outlet 8 a distance suificient to assure slip flow to occur. It is to be understood that the accumulator 4, the bleed line 11 and the connecting passage 9 are all disposed in a portion of the evaporator structure 1 which is arranged in a generallyvertical position both for the purpose of bypassing only gaseous refrigerant through the bleed line 11 and also to obtain maximum separation of the remaining gaseous refrigerant from the liquid refrigerant in the accumulator 4.

The operation of the present invention may best be understood from consideration of the fact that the normal How of refrigerant through a serpentine passage forming the evaporator section 2, after partial evapora:

tion of the refrigerant, is in the form of slugs of liquid refrigerant separated by bubbles or slugs of gaseous or vaporized refrigerant. As the slugs of liquid refrigerant enter the horizontal connecting passage 9, slip flow characterized by a separation of the liquid and the vapor occurs with the result that the liquid flows along the lower portion of the passage and the vapor flows through the passage above the liquid layer 10. The vapor bleed line 11 is sized so that with normal flow variations of refrigerant through the refrigerating system, almost all ofthe vapor is withdrawn from above the liquid refrigerant layer 10 in the horizontal passage 9 so that it passes directly into the suction line 6 for return to the compressor. As a result, substantially less gaseous refrigerant enters the bottom of accumulator 4 so that there is substantially less turbulence in the accumulator. The accumulator is then better able to perform its fundamental purpose of s asm w r f decelerating the liquid speed and separating the remaining gaseous refrigerant so that it-can passto the suction line 6 without entrained liquid refrigerant.

While there has been shown and described a particular embodiment of the present invention, it will be understood that the invention is not limited thereto and it is intended by the appended claims to cover all modifications thereof within the true spirit and scope of the invention.

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

1. In a refrigerating system, a tube-in-sheet evaporator structure providing a tubular evaporator section, a wafilegrid accumulator, a substantially horizontal connecting passage connecting the outlet end of said evaporator section to the bottom portion of said accumulator, a suction line connected to the top of said accumulator and disposed above said connecting passage, and a vapor bleed line connecting said horizontal connecting passage and said suction line for bleeding gaseous refrigerant from said passage tosaid suction line.

2. In a refrigerating'system, a tube-in-sheet evaporator structure providing a tubular evaporator section, a vertically' arranged waffle-grid accumulator, a substantially horizontal connecting passage connecting the outlet end of said evaporator section to the bottom portion of said accumulator of a cross-sectional size larger than said tubular evaporator section so that a liquid-vapor mixture of refrigerant entering said passage from said evaporator will separate and the liquid refrigerant will slip flow along said passage, a suction line connected to the top of said accumulator and disposed above said connecting passage for conducting gaseous refrigerant from said accumulator and-a-vapor bleed line connecting said connecting passage and said suction line for bleeding most of the gaseous refrigerant from said passage to said suction line and thereby preventing the gaseous refrigerant from causing excessive turbulence of liquidrefrigerant in said accumulator.

References Cited in the file of this patent UNITED STATES PATENTS 2,776,549 Gerhardt Jan. 8, 1957

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