US2109986A - Cooling unit for refrigerating machines - Google Patents

Description

March], 1938. L. w. ATCHISON COOLING UNIT FOR REFRIGERATING MACHINES 2 Sheets-Sheet 1 Filed NOV. 27, 1935 Fig.1.

Inventor: Leonard Wjtchison, '=l 0. M

is AttoThey.

March 1, 1938. w c -uso 2,109,986

COOLING UNIT FOR REFRIGERATING MACHINES Filed Nov. 27, 1935 2 Sheets-Sheet 2 Fig.5.

4 zc 23 24 mm...

I n 7 1 w I I Inventor:

Leonard \M Atchison,

is Attorney.

Patented Mar. 1, 1938 UNITED STATES COOLING UNIT FOR BEFBIGERATING MACHINES Leonard W. Atchison, Schenectady, N. Y., assignor to General Electric Company. a corporation of New York Application November 27, 1935, Serial No. 51,846

My invention relates to healing units or evaporators for refrigerating machines.

This application is a continuation in part of my application Serial. No. 7,683, filed February 23, 1935, and assigned to the General Electric Company, assignee of this present application.

It is an object of my invention to provide a simple and improved cooling unit or evaporator of the flooded type for refrigerating machines having a plurality of surfaces for supporting freezing trays or the like, which shall afford an efficient circulation of liquid refrigerant, and which shall be easy to manufacture.

Another object of my invention is to provide a sheet metal evaporator having an improved freezing surface affording high heat absorbing capacity.

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 drawings, in which Fig. 1 shows a household refrigerator utilizing an evaporator embodying my invention; Fig. 2 is an enlarged perspective view of the evaporator shown in Fig. 1; Fig. 3 is a plan view of the sheet metal portions of the evaporator shown in Fig. 1 prior to bending. Fig. 4 is an enlarged sectional view on the line 44 of Fig. 3; Fig. 5 is an enlarged view of a portion of the conduit shown in section in Fig. 4 showing the distribution of refrigerant therein and Fig. 6 is a front elevation of a cooling unit including two evaporators, such as the one shown in Fig. 1.

Referring to the drawings, in Fig. 1 I have shown a household refrigerator comprising a cabinet Ill having a food compartment II and a door l2 for closing the compartment. The compartment ii is cooled by an evaporator or cooling unit I3 arranged in the upper portion thereof and supplied with refrigerant from a refrigerating machine mounted on the top of the cabinet. The refrigerating machine comprises a closed casing it in which is arranged a motor and a compressor, an air cooled condenser i5 having a conduit I6, and a float valve chamber I1. During operation of the motor and compressor within the casing i4, refrigerant is compressed and discharged into the conduit I6 of the condenser i5 where it is cooled and liquefied, and then flows through a connection Hi to the float valve chamber l1. When a predetermined amount of liquid refrigerant has collected in the float valve chamber ll, a float arranged therein rises and admits refrigerant through a conduit IE to the evaporator iii. The liquid refrigerant is vaporized by the absor tion of heat from the chamber H and the vapor col-- lects in a cylindrical header 20 from which it is withdrawn through a. conduit 2! and is returned to the casing M. This cycle of operation continues as long as the compressor within the casing is operating. The temperature within the compartment II is regulated thermostatically in the usual manner by controlling the operation of the motor which drives the compressor within the casing M.

It is desirable to provide an evaporator which shall have a plurality of surfaces on which freezing trays or the like may be supported, and which shall provide an efficient circulation of liquid refrigerant in order rapidly to freeze the water or food within the trays. Furthermore, it is desirable that the evaporator be of simple construction. I attain these advantages by constructing the evaporator of two sheets of metal having indentations formed therein and shaped to provide adequate surface for cooling the air in the compartment and a plurality of surfaces for supporting freezing trays and the like. The indentations are arranged to form a header and a plurality of depending U-shaped refrigerant circulating passages or conduits wherein liquid refrigerant may be recirculated, and a sinuous passage or conduit for supplying refrigerant to the depending passages and for producing a circulation of refrigerant therein. Portions of the refrigerant passages are arranged in the freezing tray supporting surfaces so as to provide for the absorption of heat from the freezing trays and the like.

Referring now to Fig. 2, the evaporator I3 is made of inner and outer sheet metal portions,,

which in the construction shown comprise inner and outer sheets 22 and 23 respectively. The sheets 22 and 23 are made of stainless steel or other suitable material and are provided with indentations or corrugations forming the cylindrical header 20 adjacent the upper ends of the sheets, a plurality of depending u-shaped passages or conduits 25, each communicating at both ends with the lower portion of the header, a sinuous conduit 26, a manifold 21', and a plurality of ducts 28 connecting the manifold 21 and the lower portion of each of the U-shaped passages 25. The sheets 22 and 23 are bent to form side walls 28 and 30 of the evaporator, and top and bottom walls 3| and 32 respectively providing upper and lower surfaces 3la and 32a for supporting freezing trays and the like. The depending U-shaped passages 25 extend downwardly from the header 20 within the side wall 29 and across the bottom wall 32, and the sinuous conduit 26 extends in part across the top wall 3! and in part within the side wall 30. The sheets 22 and 23 are secured together around their edges and between the indentations by welding, brazing, or in any other suitable manner, the front and rear edges of the sheet 22 being folded over the edge of the sheet 23, as shown at 2i. A flange 33 formed on the sheet 22 and at the end thereof remote from the header flts against the side wall 29 and is welded or otherwise secured thereto. A metal sheet 34 is welded to the upper end of the side wall 30 and constitutes a side wall for an upper freezing chamber. The wall 29 and the wall 34 are provided with flanges 35 and 36 respectively, for securing the evaporator to a removable top wall of the refrigerator cabinet. The arrangement of the header and passages within the walls of the evaporator is clearly shown in Fig. 3.

In constructing the evaporator shown in Fig. 2, the outer sheet 23 is cut and stamped while flat as shown in Fig. 3. One side of the header 20, the U-shaped passages or conduits 25, the manifold 21, ducts 28, a passage 31, and the portions of the sinuous conduit 28, which are to lie within the side wall, are formed in the outer sheet 22. The inner sheet 22 is cut and stamped while flat so as to provide the other half of the header 2l| and the indentations forming the portion of the sinuous conduit 26, which is to lie within the top wall at, these indentations being clearly shown in dotted lines in Fig. 3. The two sheets 22 and 23 are then secured together face to face. and are welded together around the edges and between the indentations so as to form a pressure-tight and fluid-tight evaporator, and the edges of the sheet 22 are folded over the opposite edges of the sheet 23, as indicated at 24 in Fig. 2. The flange 33 is formed at the end of the sheet 22 remote from the header 2|! and the flange 25 is formed at the other end thereof and the sheets are bent to form the evaporator shown in Fig. 2, the sheet 23 being the outside sheet. The bends are so located that the U-shaped passages 25 lie within the side wall 29 and the bottom wall 22, and so that the manifold 2! lies along the corner between the bottom wall 22 and the side wall 20. The top wall 3i extends from the wall 30 toward the wall 29 and the flange 23 is welded to the wall 29 thereby forming an enclosed freezing chamber in the lower portion of the evaporator between the top and bottom walls 3| and 32. After the sheets 22 and 23 have been formed in this manner, the wall 84 is welded or otherwise secured to the top of the wall 20 to complete the evaporator and to form an upper freezing chamber. It will be noted that the indentations in the sheet 22 lie on the outside of the evaporator, and the indentations in the sheet 22 lie on the lower side of the top wall 3|; both freezing tray supporting surfaces are thus made flat to give good heat exchange contact, and further, a flat surface is provided for the welding of the flange 82 to the side wall 28.

All the refrigerant which is supplied to. the evaporator must pass through the sinuous conduit 20 before reaching the manifold 21 and the circulating passages 25 since the sinuous conduit is in series between the supply conduit l8 and the manifold. During normal operation of the refrigerating machine, refrigerant flows through the passage 20 at a substantially constant rate, that is, the pounds of refrigerant passing therethrough per second do not change. I have found that the cross-sectional area of {the conduit 26 should be proportioned with respect to the normal rate of flow therethrough so that the vaporized refrigerant which flows at a relatively high velocity forces the liquid refrigerant in the conduit toward all the interior surfaces thereof. when the conduit is proportioned to give this characteristic of operation, as shown in Fig. 5, the vapor 26a flows through the center of the conduit and the liquid 26b flows in an envelope about the vapor in intimate contact with the interior of the conduit and the entire interior surface is maintained wet with liquid refrigerant thereby greatly increasing the heat absorbing capacity of the conduit. In Fig. 5, for purpose of illustration, the vaporized refrigerant has been shown as having a cross-section of smooth periphery. It should be understood, however, that there is turbulence of the liquid refrigerant and that drops or waves of liquid may be present in the vapor stream. However, if the velocity of the refrigerant is sufficiently high a layer of liquid refrigerant will be maintained on all of the interior surfaces of the conduit. If the velocity is too low the upper side of the conduit will be dry except for the occasional splashing of liquid due to the wave action along the conduit. The effective heat absorbing surface is also increased by making the conduit thin and flat so that from to 55 per cent or substantially one half of the surface of the conduit lies in the freezing tray supporting surface adjacent any articles placed therein for cooling. Highly efllcient operation under normal conditions for household refrigerating machine evaporators will be obtained when the depth of the conduit 26 is made between 20 and '75 thousandths of an inch, depending on the capacity of the machine and the refrigerant used, the width of the conduit, the mean or average width when the width is variable as in Fig. 5, being between five and nine times the depth. The figures given are only illustrative of depths and widths that have been used in evaporators of the construction shown in Fig. 2, and do not fix any definite cross sections. Those skilled in the art will determine the area of the cross section suitable for any particular construction, capacity and refrigerant, by tests of different cross sections under the conditions with which they are dealing. This construction provides a freezing shelf or other evaporator surface having a high heat absorbing capacity even when the evaporator is constructed of a material such as stainless steel which has areiatively low coeflicient of thermal conductivity. It will be observed that the conduit 25 is a conduit of the non-flooded type. The distribution of the liquid refrigerant over the entire inner periphery of an evaporator conduit of the non-flooded type is especially useful in the case of a horizontal conduit and this is particularly the case where a horizontal conduit is made of a relatively poor heat conductor such as stainless steel.

Referring now to Figs. 2 and 3, liquid refrigerant is admitted to the evaporator I I through the conduit [9, enters the passage 21, and flows into the sinuous passage 26 through which it circulates and from which it flows into the manifold 21. Refrigerant from the manifold 21 flows through the ducts 28 and into the lower portion of the depending U-shaped passages or conduits 25 in which the refrigerant induces a circulation, the refrigerant circulating up one side of each of the passages 25 into the header and from the header down the other sides of the passages. Gaseous refrigerant is withdrawn from the header above the level of liquid refrigerant therein through the conduit 2|. In this manner the walls of the evaporator produce adequate refrigeration to cool the air in the food compartment of the cabinet, and freeze articles on the surfaces lie and 22a.

Refrigerant, which is vaporized in the sinuous passage 26, increases the pressure in the passage and forces refrigerant from the manifold 21 and through the ducts 23 into the U-shaped passages or conduits 25. This flow of refrigerant will take place even though refrigerant is not being supplied to the evaporator from the float valve chamber H, as long as heat is being absorbed by the evaporator and is vaporizing refrigerant in the sinuous passage 26. The liquid and gaseous refrigerant entering the U-shaped passages 25 will produce a circulation therein which will assist the thermally induced circulation in the passages in either direction of flow. This arrangement whereby the U-shaped passages are provided with ducts for admitting refrigerant at the lower ends thereof is not my invention, but is the invention of Delbert F. Newman, and is described and claimed in his copending application Serial No. 3,651, riled January 26, 1935, now Patent No. 2,060,633, granted November 10, 1936, and assigned to the General Electric Company, assignee of my present invention.

It is sometimes desirable to provide a larger capacity cooling unit having additional surfaces for supporting freezing trays and the like, and for cooling the compartment in which it is used. In order to accomplish this, I secure together side by side two evaporators of the type shown in Figs. 1 and 2 and described above. An equalizer conduit of large diameter is provided to connect the headers and to maintain the same level of liquid refrigerant in both evaporators, and also to equalize the pressures therein. A large capacity cooling unit constructed in this manner is shown in Fig. 6 and comprises evaporators 38 and 39 which are each of the construction shown in Figs. 1, 2, 3, 4 and 5, the evaporator 33 being of greater width than the evaporator 38. The evaporators 38 and 39 are provided with supporting flanges 40 and ii respectively above the headers of the evaporators, and with supporting flanges 42a and 430. on extended side walls 42 and 43 respectively on the sides of the evaporators remote from the headers, and the cooling unit may be secured in a refrigerator cabinet by connecting these flanges to the top wall of the cabinet. Liquid refrigerant is admitted to the cooling unit through a conduit 44 and to the evaporators 3a and 39 through connections 45 and 46 respectively. Headers 41 and 48 of the evaporators 38 and 33 respectively are provided with an equalizer connection which in this construction comprises a conduit or tube 49 of relatively large diameter which connects the headers at the level of liquid refrigerant and equalizes the liquid levels in the evaporators, and also the gas pressures therein. Gaseous refrigerant is withdrawn from the cooling unit through a suction connection 5|) communicating with the header 48 above the level of liquid refrigerant therein. During operation of the cooling unit shown in Fig. 6 there is a rapid circulation of refrigerant throughout the passages within the surfaces for supporting the freezing trays, and a large tray supporting area is available to freeze ice, desserts, or the like. Furthermore, a large area for cooling the air within the cabinet is provided. It will be understood that the circulation of liquid refrigerant in the evaporators 33 and 39 is the same as that described in connection with Figs. 2 and 3, except that liquid refrigerant may flow between the evaporators and the gaseous refrigerant is withdrawn only from the header 39.

While I have shown and described my invention as applied to an evaporator for household refrigerators, other applications will readily be apparent to those skilledin the art, I do not, therefore, desire my invention to be limited to the particular construction shown and described, and 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 in the United States is:

1. A flooded evaporator for refrigerating machines comprising a header for containing liquid refrigerant, a plurality of separate U-shaped refrigerant circulating conduits depending from said header, each of said U-shaped conduits communicating at both ends with said header below the normal liquid level of the refrigerant therein, means including said U-shaped conduits for providing a side wall of said evaporator and a surface for supporting freezing trays and the like, means for supplying refrigerant to said U-shaped conduits and for producing a circulation of refrigerant in said U-shaped conduits, means including a sinuous conduit communicating with said circulation producing means for providing a second wall of said evaporator and another surface for supporting freezing trays, means for supplying refrigerant to said sinuous conduit, and means for withdrawing gaseous refrigerant from said header.

2. A flooded evaporator for refrigerating machines comprising sheet metal portions joined together about their edges and forming two side walls and top and bottom walls of a freezing chamber, said top and bottom walls having surfaces for supporting freezing trays and the like, a header formed between said sheet metal portions above said top wall, a plurality of U-shaped refrigerant circulating conduits communicating at both ends with said header, said U-shaped conduits extending between said sheet metal portions in one of said side walls and in said bottom wall, a sinuous conduit extending between said sheet metal portions in the other of said side walls and in said top wall, means for supplying liquid refrigerant to said sinuous conduit, a manifold communicating with said sinuous conduit and extending between said sheet metal portions near said bottom wall, means including a plurality of ducts connecting said manifold and said Ushaped conduits for injecting refrigerant into said U-shaped conduits to induce a circulation of refrigerant therein, and means for withdrawing gaseous refrigerant -from said header.

3. A flooded evaporator for refrigerating machines comprising two sheet metal portions joined together about their edges and formed to provide two side walls and top and bottom walls of a freezing chamber, said top and bottom walls providing an upper and a lower surface for supporting freezing trays and the like, one of said side walls extending above said upper supporting surface, a header formed in said one side wall, means for securing the edge of said top wall to said one side wall, means including a wall secured to the other side wall of said evaporator for supporting said evaporator and for providing an upper freezing chamber therein, means including a plurality of conduits formed between said sheet metal portions and communicating with said header for providing refrigerant circulating paths within said side walls and within said top and bottom walls, means supplying refrigerant to said evaporator for producing a circulation of refrigerant in said conduits, and means for withdrawing gaseous refrigerant from said header.

4. A cooling unit for refrigerating machines including two refrigerant headers arranged at substantially the same level, means including a group of depending refrigerant circulating conduits communicating with the first of said headers and forming a freezing chamber, means including a group of depending refrigerant circulating conduits communicating with the second of said headers and forming a second freezing chamber, means for supplying liquid refrigerant to each of said groups of refrigerant circulating conduits, means including an equalizing connection between said headers for maintaining the same level of liquid refrigerant in both of said headers and for maintaining both of said headers at the same pressure, and means for withdrawing gaseous refrigerant from said cooling unit.

5. Refrigerating apparatus having a thin flat refrigerating conduit of the non-flooded type, means for supplying liquid refrigerant to said conduit and for withdrawing refrigerant from said conduit, the cross-sectional area of said conduit being so proportioned with respect to the normal operating capacity of the means for supplying and withdrawing refrigerant that the vaporized refrigerant flowing therein forces the liquid refrigerant flowing therein toward all interior surfaces thereof to maintain the entire interior surface of said conduit wet with liquid refrigerant.

6. Refrigerating apparatus having a flooded evaporator having side and bottom walls and comprising a header and a plurality of depending refrigerant circulating conduits communicating therewith, means including a thin fiat nonflooded conduit for providing a freezing tray supporting shelf between said side walls, means for supplying liquid refrigerant to said shelf conduit and for withdrawing vaporized refrigerant from said header, said shelf conduit having a crosssectional area so proportioned with respect to the normal operating capacity of the refrigerant supplying and withdrawing means that the vaporized refrigerant flowing therein forces the liquid refiigerant flowing therein toward all interior surfaces thereof to maintain the entire interior surface of said shelf conduit wet with liquid refrigerant, and means connecting said shelf conduit and said depending conduits for supplying refrigerant to said depending conduits and for producing a circulation of refrigerant therein.

'7. A flooded evaporator for refrigerating machines comprising sheet metal portions joined together about their edges and forming a cooling surface, said sheet metal portions having formed therein a header and a plurality of depending refrigerant circulating conduits each communicating at both ends with said header, a sinuous conduit formed between said sheet metal portions, means for supplying liquid refrigerant to said sinuous conduit, means providing communication between said sinuous conduit and said refrigerant circulating conduits for injecting refrigerant into said refrigerant circulating conduits and for producing a circulation of liquid refrigerant in said refrigerant circulating conduits, and means for withdrawing gaseous refrigerant from said header.

8. Refrigerating apparatus having a refrigerating conduit of the non-flooded type and means for supplying a vaporizabie liquid refrigerant thereto and withdrawing the vaporized refrigerant therefrom, the area of the cross section of the conduit being so small with respect to the normal operating capacity of the means for supplying and withdrawing the refrigerant as to cause the refrigerant to flow in the conduit with a velocity so high that the liquid refrigerant will cover the entire inner surface of the conduit and completely enclose the vaporized refrigerant throughout a substantial portion of the length of the conduit.

9. Refrigerating apparatus having a refrigerating conduit of the non-flooded type and means for supplying a vaporizable liquid refrigerant thereto and withdrawing the vaporized refrigerant therefrom, the area of the cross section of the conduit being so small with respect to the normal operating capacity of the means for supplying and withdrawing the refrigerant as to cause the refrigerant to flow in the conduit with a velocity so high that the liquid refrigerant will cover the entire inner surface of the conduit and completely enclose the vaporized refrigerant throughout substantially the entire length of the conduit.

10. Refrigerating apparatus having a refrigerating conduit of the non-flooded type comprising a horizontal portion, means for supplying a vaporizable liquid refrigerant to said conduit and for withdrawing the vaporized refrigerant therefrom, the area of the cross section of said horizontal portion being so small with respect to the normal operating capacity of the means for supplying and withdrawing the refrigerant as to cause the refrigerant to pass through said horizontal portion of the conduit with a velocity sufficiently high to cause liquid refrigerant to cover the entire inner surface of the horizontal portion of the conduit and enclose the vaporized refrigerant for substantially the entire length of said horizontal portion.

11. Refrigerating apparatus having a refrigerating conduit of the non-flooded type composed of a material of relatively low heat conductivity, and means for supplying a vaporizable liquid refrigerant thereto and for withdrawing the vaporized refrigerant therefrom, the area of the cross section of the conduit being so small with respect to the normal operating capacity of the means for supplying and withdrawing the refrigerant as to cause the refrigerant to flow in the conduit with a velocity so high that the liquid refrigerant will cover the entire inner surface of the conduit and completely enclose the vaporized refrigerant throughout substantially the entire length of the conduit.

12. A household refrigerator having a refrigerating conduit of the non-flooded type comprising a horizontal portion made of a relatively poor conductor of heat, and means for supplying a vaporizable liquid refrigerant to said conduit and for withdrawing the vaporized refrigerant therefrom, the area of the cross section of the horizontal portion of said conduit being so small with respect to the normal operating capacity of the means for supplying and withdrawing the refrigerant as to cause the refrigerant to flow in said horizontal portion with a velocity so high that the liquid refrigerant will cover the entire inner surface thereof and completely enclose the vaporized refrigerant throughout substantially the entire length thereof.

LEONARD W. ATCHISON.

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