US3902332A

US3902332A - Refrigerating systems

Info

Publication number: US3902332A
Application number: US444875A
Authority: US
Inventors: Albert Torcomian
Original assignee: Environmental Container Corp
Current assignee: Environmental Container Corp
Priority date: 1974-02-22
Filing date: 1974-02-22
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02

Abstract

A refrigerating system according to which a wall structure has an interior surface region defining at least part of an interior space the temperature of which is to be reduced with respect to the temperature of the outer ambient atmosphere. This wall structure has an exterior surface region which is exposed to the ambient atmosphere and an intermediate insulating region situated between the interior and exterior surface regions. A refrigerating assembly is operatively connected with the above wall structure for reducing the temperature of the interior space, and this refrigerating assembly includes an evaporator at least part of which is formed by the interior surface region of the wall structure, a condenser at least part of which is formed by the exterior surface region of the wall structure, and a compressor communicating with the evaporator and condenser for circulating a refrigerant therethrough.

Description

United States Patent Torcomian Sept. 2, 1975 REFRIGERATING SYSTEMS 3,306,353 2/1967 Burne 165/172 [75] Inventor: Albert Torcomian, Havertown, Pa.

Primary Examiner-William J. Wye [73] Ass1gnee: Envlron Comamer Attorney, Agent, or FirmSteinberg & Blake 1 Corporation, New York, NY.

[21 1 Appl' 444,875 A refrigerating system according to which a wall structure has an interior surface region defining at least 52 us. c1. 62/451; 62/452; 62/453; p of an interior Space the vwrhiher'ature of which is 2/42 2 419 to be reduced with respect to the temperature of the [51] Int. Cl. F25d 23/06 Outer ambient atmosphere- This wall structure has an 581 Field 61 Search 62/451, 452, 453, 426, exterior surface region which is exposed to the ambi- 2/405 407 419 ent atmosphere and an intermediate insulating region situated between the interior and exterior surface re- 5 R f r Cited gions. A refrigerating assembly is operatively con- UNITED STATES PATENTS nected with the above wall structure for reducing the temperature of the interior space, and this refrigerat- 2,124,110 7/1938 H611 62/451 ing assembly includes an evaporator at least part of 2,464,606 3/1949 Phllipp 62/45] 2,486,822 11/1949 Cameron l65/18O wh1ch 15 formed by the interior surface reg1on of the 2,667,763 2/1954 Harris 62 451 Structure a condenser at least Part Of which is 2,795,035 6/1957 Kafer 165/171 formed y the exterior Surface region of the Wall 2,802,348 8/1957 White 62/426 structure, and a compressor communicating with the 2,959,939 11/1960 Arzberger.. 62/451 evaporator and condenser for circulating a refrigerant 2,992,545 7/1961 Walker 62/451 the eth h, 3,092,220 6/1963 Black 62/419 3,122,006 2/1964 Jacobs 62/451 12 Claims, 9 Drawing Figures PATENTEU 21975 sumanrs 1 REFRIGERATING SYSTEMS BACKGROUND OF THE INVENTION The present invention relates to refrigerating structures.

As is well known, there are many situations where it is desirable to provide refrigerated atmospheres for purposes such as preventing spoilage of food products, air conditioning interior spaces, and the like. However, at the present time considerable difficulties are encountered because of the fact that the conventional refrigerating units can be connected to the spaces which are to be refrigerated only with difficulty and with con siderable lack of efficiency. For example in the case of transporting food products considerable loss of efficiency and difficulties are encountered in refrigerating the interior of a truck trailer or the interior of a railroad car. Thus, special constructions are required for such trailers or railroad cars, or for truck bodies which are not in the form of a trailer, and the refrigerating unit itself must be properly hooked up to the specially constructed bodies of the vehicles, occupying an undesirably large amount of space and operating with poor efficiency, so that undesirable costs are encountered.

Also in the case of air conditioners it is conventional to provide special fans which direct the air which is to be chilled over coils in order to be cooled thereby before being distributed through suitable duct systems to the spaces which are to be cooled. Such conventional air conditioning systems also operate at less than a desirable efficiency and create problems with respect to heat losses and desirable flow of the air which is to be cooled with respect to the structure which cools the same.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide structures capable of avoiding the above drawbacks by providing highly efficient relatively simple structures capable of refrigerating an interior space, whether this space forms, for example, part of a duct through which air is directed to be cooled or part of a container in which food products or the like are stored to prevent spoilage thereof.

In particular it is an object of the present invention to provide a construction according to which a considerable part of the refrigerating structure itself is formed by the wall structure of the duct, container, or the like, so that a minimum amount of refrigerating structure need be located at the exterior of and hooked up to such a wall structure while at the same time efficiency is increased and costs are reduced.

In accordance with the invention the refrigerating system includes a wall structure having an interior surface region which defines at least part of an interior space the temperature of which is to be reduced with respect to the exterior ambient temperature. This wall structure has an exterior surface region which is exposed to the ambient atmosphere and an intermediate insulating region which is situated between the interior and exterior surface regions for insulating them from each other. A refrigerating assembly includes an evaporator means which is formed at least in part by the interior surface region of the wall structure, a condenser means whichis formed at least in part by the exterior surface region of the wall structure, and a compressor means which is operatively connected with the evaporator means and compressor means for circulating a refrigerant therethrough. The intermediate insulating region of the wall structure has opposed faces formed with grooves which receive coils respectively forming part of the evaporator means and condenser means, and these coils engage interior and exterior metal skins which are adhered to the intermediate insulating region and which also form part of the evaporator means and condenser means, the compressor means being operatively connected with these coils for circulating a refrigerant therethrough.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. II is a fragmentary perspective and schematic illustration of one embodiment of a duct system to be used for air conditioning purposes in accordance with the invention;

FIG. 2 is a fragmentary perspective schematic illus tration of another embodiment of a duct system to be used for air conditioning purposes according to the invention;

FIG. 3 is a fragmentary perspective illustration of part of a container adapted to receive in its interior food products or the like which are to be refrigerated in accordance with the invention;

FIG. 4 is an exploded fragmentary perspective illustration of part of a method of manufacturing the structure of the invention, FIG. 4 also illustrating details of the structure of the invention;

FIG. 5 is a schematic sectional elevation of a stage of the method subsequent to that of FIG. 4;

FIG. 6 is a fragmentary sectional illustration showing in detail one possible refrigerating structure of the invention;

FIG. 7 is a fragmentary sectional illustration of another embodiment of a refrigerating structure according to the invention;

FIG. 8 is a schematic representation of one type type of refrigerating system according to the invention adapted to be used in connection with relatively small refrigerating containers; and

FIG. 9 is a partly fragmentary schematic illustration of a system of the invention which is adapted to be used for a refrigerating system designed for relatively large containers.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, there is illustrated therein an elongated duct 10 which in the illustrated example is of a rectangular cross-sectional configuration. This duct 10 of the invention has an exterior surface region 12 formed in part by a metal skin and an interior surface region 14 which also is formed in part by a metal skin. The exterior surface region 12 and the interior surface region 14 of the illustrated tubular wall structure 16 which forms the duct I0 are separated from each other by an intermediate region 18 of the wall means 16, this intermediate region 18 being made of a thermal insulating body so that the intermediate region 18 insulates the exterior surface region 12 and the interior surface region 14 from each other. As will be apparent from the description which follows the intermediate insulating region 18 may be made of a foam plastic such as a closed-cell urethane, while part of the exterior surface region 12 can be formed by an outer metal skin of aluminum, for example, with part of the interior surface region I4 being formed by a metal skin which also may be made of aluminum.

As will be apparent from the description below, the exterior surface region 12 includes not only the illustrated metal skin but suitable condenser coils while the interior surface region 14 includes in addition to the illustrated metal skin 14 suitable evaporator coils, and the condenser means and evaporator means which are formed in part by the exterior surface region 12 and interior surface region 14 of the wall means 16 communicate with a compressor means 20 as shown schematically in FIG. I so that the compressor means 20 together with the above evaporator means and condenser means form a refrigerating assembly capable of refrigerating the interior space which is defined at least in part by the interior surface region 14 of the wall means As is shown schematically in FIG. I, a blower 22 forms an air-moving means for moving air through the duct 10. Thus, the refrigerating circuit which includes the compressor means 20 also includes the condenser means at the exterior surface region 12 and the evaporator means at the interior surface region 14 of the wall means 16, and this refrigerating assembly will reduce the temperature of the air within the duct means It) so as to chill the air thus enabling the duct means It) to carry out an air-conditioning function.

According to the embodiment of the invention which is illustrated in FIG. 2. the elongated tubular duct 24 is of a circular cross section and has an exterior surface region 26 corresponding to the exterior surface region 12 as well as an interior surface region 28 corresponding to the interior surface region 14, these surface re gions 26 and 28 being insulated from each other by an intermediate insulating region 30 of the illustrated tubular wall means 32 which thus is the same as the wall means 16 except that it is of a circular cross sectional configuration rather than a rectangular cross sectional configuration. The exterior surface region 26 includes a tubular metal skin of aluminum, for example, which is circular in cross section and which engages condenser coils embedded in an outer face of the tubular intermediate insulating wall region 30 which may be made of urethane, thus being of the same material as the intermediate wall region 18. The interior surface region 28 includes also an inner tubular metal skin of circular cross section engaging the evaporator coils em bedded at an inner face of the insulating body 30 and engaging the metal skin. The compressor means 34 communicates with the coils of the condenser means which includes the exterior surface region 26 and the evaporator means which includes the interior surface region 28 of the wall means 32 so as to circulate a suitable refrigerant therethrough. As is shown schematically in FIG. 2 a suitable fan 36 is situated at part of the interior space defined by the inner surface region 28 for driving air therethrough to be refrigerated in the i'nanner described above in connection with FIG. 1.

Referring to FIG. 3, there is illustrated therein in a fragmentary schematic manner part of a container 38 adapted to store in its interior perishables, for example, such as food products and the like, so that when this container is situated in a freight car or on a suitable truck, the products stored in the container 38 will not spoil.

In the illustrated example the container 38 has an upper wall structure which may be made of a suitable interior insulating body 42 which is surrounded and engaged by a suitable exterior skin 44 made of any suitable metal, for example.

in addition the container 38 has a floor structure 46 made also of an interior insulating body 48 surrounded and engaged by a suitable covering 50 which may be in the form of a metal skin also. However it is preferred to provide the inner surface region 52 of the floor structure 46 with extrusions formed so as to provide grooves which extend longitudinally along the interior of the container for providing a more efficient support of the food products and for collecting moisture which may settle between the grooves of the extrusions used for this purpose.

Each of the opposed side wall structures 54 of the container 38 have a construction in accordance with the present invention in the illustrated example, although it is of course equally possible to provide such a structure not only at the side walls 54 but also at the top wall 40 in the bottom wall 46. The ends of the container 38 are not illustrated. These ends can take any desired construction for tightly closing the interior space of the container 38, and this container may be provided with any suitable door through which access may be had to the interior of the container 38. Such a door may be formed for example, by the upper wall structure 40 or by one of the unillustrated end walls.

The side walls 54 according to the invention are each provided with an interior surface region 56 and an exterior surface region 58 separated by an intermediate insulating wall region 60. Thus the interior and exterior surface regions of the wall structures 54 may include metal skins of aluminum or the like which directly engage coils embedded in the opposed faces of the intermediate insulating regions 60 which may be made of a foam urethane, for example. The unillustrated coils which engage the interior skin at the inner surface region 56 of each wall structure 54- form therewith an evaporator means while the unillustrated coils which engage the exterior metal skin at the exterior surface region 58 form therewith a condenser means, and this evaporator means and condenser means at each wall region communicates with a compressor as described above in connection with FIGS. 1 and 2 so that in this way the interior space of the container 38 can be refrigerated.

FIG. 4 illustrates schematically further details of any of the above wall means 116, 32, or 54, as well as part of the method for manufacturing the same. Thus any of the above wall means includes the intermediate insulating body fragmentarily illustrated in FIG. 4- by the intermediate insulating body 62 made, for example, of a closed-cell urethane. This body of thermal insulating material 62 has an outer face 6 which is visible in FIG. 4 and an opposed inner face 66. These

faces

64 and 66 are suitably routed so as to be formed with grooves 68 and '70, respectively. These grooves match the configuration of coils '72 and 74, respectively. Thus after the grooves 68 and '71) are formed the coils '72 and '74 can be seated therein.

FIG. 4 shows an outer metal skin 76 made of aluminum, for example, this skin 76 being adapted to engage the coils 72 as well as the outer face 64 of the insulating body 62. Also FIG. 4 illustrates an inner metal skin '78 made of aluminum, for example. and adapted to engage the coils 74 as well as the face 66 of the body 62.

As is shown in FIG. 4 an adhesive in the form of a suitable glue, for example, is applied, as by being sprayed from nozzles 80 to the surfaces of the

skins

76 and 78 which are respectively to engage the

faces

64 and 66. This adhesive may also be applied to the

faces

64 and 66, and the application of the adhesive may take place either before or after the

coils

72 and 74 are received in the

grooves

68 and 70, respectively.

Thus it will be seen that with the structure of FIG. 4 the coils 72 together with the skin 76 will form the exterior surface region of a wall means such as the wall means 16, 32, or 54, and this construction will form a condenser means of the refrigerating assembly. On the other hand, the coils 74 together with the inner metal skin 78 will form an evaporator means of the refrigerating assembly.

With the

coils

72 and 74 thus assembled in the grooves of the insulating body 62 and with the

skins

76 and 78 respectively engaging the outer face 64 and inner face 66 of the body 62, the resulting assembly is placed in an evacuated atmosphere 81 shown in FIG. 5 in a schematic manner. Thus the evacuated atmosphere 81 may be created between a plastic sheet 82 which is impervious to air and which is fluid-tightly connected with a base 82 made of concrete, for example, and formed with suitable suction passages 84 communicating with a suction pump 86. The sheet 82, before being tightly assembled with the base 82 is separated from the base to permit the assembly of FIG. 4 to be situated in the space 81. Thus FIG. 5 shows the intermediate insulating body 62 between the metal skins 76 and 78, with the

coils

72 and 74 begin omitted from FIG. 5 for the sake of clarity. The introduction of this assembly of FIG. 4 into the atmosphere 81 takes place prior to setting and drying of the adhesive applied by way of the spray nozzles 80.

In addition FIG. 5 shows a board 87 made of plywood, for example, and resting on the metal skin 78. The upper ends of the bores 84 are situated beyond the assembly of

components

62, 76, and 78 so that the space 81 will communicate freely through the bores 84 with the suction pump 86.

As a result of the creation of the evacuated atmo' sphere 81, the exterior atmospheric pressure will tightly press the

skins

76 and 78 against the insulating body 62, with ths distribution of the pressure being enhanced by way of the board 87 which acts in the nature of a platen pressing the entire assembly against the top surface of the base 82. The result is not only a tight engagement between the metal skins and the insulating body but also the elimination of any bubbles in the adhesive which might not be favorable to the desired thermal conditions. After elapse of a suitable time the entire assembly is removed from the atmosphere 81 and another assembly is introduced to be tightly assembled together in the evacuated atmosphere 81 while the ad hesive sets, so that the finished wall means can be removed from the evacuated atmosphere 81 without any danger of the parts becoming separated from each other.

As is shown in FIG. 6, the intermediate insulating wall region 86, made of a suitable closed-cell urethane, for example, may be formed in each of its opposed faces with grooves 88 of semicircular cross section for receiving a coil structure 90 which may be either the coil 72 or the coil 74. This c-oil structure has a cross section matching that of the groove 88. Initially the flat outer surface of the coil 90 may be situated slightly beyond the face of the insulating body 86 which is engaged by the metal skin 92 which may be either the metal skin 76 or the metal skin 78. Because of the fact that the foam plastic insulating body 86 is compressible to some extent during the assembly of the parts in the evacuated atmosphere 81 the skin 92 will engage the entire exposed surface of the body 86 pressing the coil 90 into the groove 88 to achieve an assembly as illustrated in FIG. 6.

However, it is also possible to provide an arrangement as shown in FIG. 7 according to which the insulating foam plastic body 94 has grooves 96 of substantially rectangular cross section receiving a metal wool filler 98 in which the coil 100 is seated, this coil 100 also having the same cross section as the coil 90 so that it has a flat surface to engage: the metal skin 102 which is adhered to a face of the body 94 in the manner described above. Thus, with either of the structures of FIGS. 6 and 7 there will be a highly efficient thermal connection between the coils and the metal skins. With the embodiment of FIG. 7 in particular the metal wool filler 98 will provide an exceedingly effective thermal connection while the embodiment of FIG. 6 is also highly effective because of the large area of contact between the flat surface of the coil 90 and the flat surface of the skin 92.

In connection with FIG. 7 it is to be noted that the metal wool filler 98 may be made of any suitable metal such as copper, steel, aluminum, or the like.

FIG. 8 illustrates schematically a basic refrigerating assembly of the invention for a relatively small container. Thus FIG. 8 shows at the left a thermally conductive metal skin 104 which forms part of a condenser means. This metal skin 104 of the illustrated condenser means directly engages the coils 106 which are embedded in an insulating body which is not illustrated in FIG. 8, in the manner described above in connection with FIGS. 6 and 7, with the metal skin 104 engaging the insulating body as was described above in connection with FIGS. 4-7.

At the right FIG. 8 shows an evaporator means which includes the thermally conductive metal skin 108 which directly engages the evaporator coils 110, this structure of the skin 108 and coils 110 engaging the surface of the insulating body which is opposed to that which engages the

components

104, 106. FIG. 8 also shows the electrically driven compressor means 112. The evaporator coil 110 has an outlet 114 communicating with the compressor 112 through a suction accumulator unit 116. The discharge 118 of the compressor 112 communicates with an inlet 120 of the condenser coils 106. The discharge 122 of the condenser coils 106 communicates with an inlet 124 of the evaporator coils through a dryer unit 126 in which dehydration takes place as well as through a TX valve or capillary tube 128 provided in a known way to achieve expansion of the fluid flowing through the inlet 124 into the evaporator coil 110. In this way a suitable refrigerant such as Freon, for example, can be circulated through the condenser means and evaporator means of FIG. 8 by way of the compressor means 112. Of course this system can be used with any of the above-described embodiments of FIGS. 1-3.

FIG. 9 shows a system similar to that of F IG. 8 but altered to provide a refrigerating cycle suitable for large containers. Thus in the case of FIG. 9 the evaporator coils 130 engage a metal skin 132 forming the interior surface region of a wall means which is larger than that of FIG. 8. The discharge of the evaporator coil I flows through a heat exchanger 134 before reaching the suction accumulator 136 which corresponds to the suction accumulator 116 of FIG. 8. From the suction accumulator 136 the refrigerant flows to the electrical compressor means 140 which corresponds to the compressor means 112 except that it is of a larger size and greater capacity. The discharge 142 of the compressor means returns the refrigerant through the heat exchanger unit 134 so that heat exchange takes place between the inlet and outlet of the compressor 140, before the refrigerant flows from the compressor in the direction illustrated to the inlet of the condenser coils 144 which correspond to the coils 106 and which engage the illustrated metal skin 148 which corresponds to the metal skin 104. These alterations of FIG. 9 with respect to the illustration of FIG. 8 enable the system of FIG. 9 to be suitable for use with relatively large refrigerator containers.

Thus it will be seen that with all of the abovedescribed embodiments of the invention the wall means which surrounds and at least partly defines the interior space whose temperature is to be reduced includes an inner surface region which forms an evaporator means and an outer surface region which forms a condenser means, the latter evaporator and condenser means communicating with the compressor means, so that in this way a highly effective refrigerating system can be achieved for practically any desired purpose.

As is apparent from the above description, the structure of the invention forms a structural heat exchanger according to which any structure such as the wall of a room, for example, may be cooled.

What is claimed is:

I. In a system for providing at an interior space a temperature lower than that prevailing at an exterior ambient atmosphere, wall means having an interior surface region which defines at least part of the interior space, an exterior surface region exposed to the ambient atmosphere, and an intermediate insulating region for thermally insulating the interior and exterior surface regions from each other, and a refrigerator assembly for refrigerating said interior space, said refrigerator assembly including evaporator means situated at and formed in part by said interior surface region of said wall means, condenser means situated at and formed in part by said exterior surface region of said wall means, and compressor means operatively connected to and communicating with said evaporator means and condenser means for circulating a refrigerant therethrough while reducing the temperature of the interior space with respect to the ambient atmosphere, said wall means including an exterior metal skin and condenser coils carried by the intermediate insulating region of said wall means and engaging said exterior metal skin to form said condenser means therewith, and said wall means including an interior metal skin and evaporator coils carried by the intermediate insulating region of said wall means and engaging said inte rior metal skin to form said evaporator means therewith, said insulating region including opposed outer surfaces formed with grooves which receive the coils of said condenser means and said evaporator means, and said coils being of a non-circular cross section and having opposed side edges between which said coils have a flat surface extending without interruption between said side edges and completely filling the area between said side edges, and said coils engaging said metal skins over the entire areas of said flat surfaces of said coils.

2. The combination of claim 1 and wherein said wall means is of an elongated tubular configuration and forms a duct through which air is adapted to flow.

3. The combination of claim 2 and wherein an airmoving means is situated at the interior of said duct for directing air through said interior space to be refrigerated thereby.

4. The combination of claim I and wherein said wall means forms part of a container in which perishables such as food products and the like are stored.

5. The combination of claim 1 and wherein said compressor means includes a discharge conduit feeding refrigerant to said condenser means and a suction conduit receiving refrigerant from said evaporator means, said condenser means having an outlet communicating with an inlet of said evaporator means, and dryer means communicating with said outlet of said condenser means and said inlet of said evaporator means for drying refrigerant flowing from said condenser means to said evaporator means and suction accumulator means situated in the path of flow of refrigerant between said evaporator means and compressor means.

6. The combination of claim 5 and wherein a heatexchanger means is operatively connected with the conduit through which refrigerant flows from said evaporator means to said suction accumulator means and with the discharge of said compressor means through which refrigerant flows from said compressor means to said condenser means. I

7. The combination of claim 1 and wherein said wall means forms part of a container adapted to be situated in a freight car for shipping perishables, said container having a pair of opposed side walls each of which forms part of said wall means and a bottom wall having an inner grooved surface on which material to be refrigerated is stored.

8. The combination of claim 1 and wherein said coils are of a semicircular cross section having a diameter formed by said fiat surface of said coils and an outer convexly curved surface forming the remainder of said semi-circular cross section.

9. The combination of claim 8 and wherein said grooves match the configuration of said outer curved surfaces of said coils.

10. The combination of claim 8 and wherein said grooves carry a thermally conductive medium in which said coils are seated.

11. The combination of claim 10 and wherein said thermally conductive medium is a metal wool.

12. The combination of claim 1 and wherein said skins are glued to opposed outer faces of the insulating region of said wall means.

Claims

1. In a system for providing at an interior space a temperature lower than that prevailing at an exterior ambient atmosphere, wall means having an interior surface region which defines at least part of the interior space, an exterior surface region exposed to the ambient atmosphere, and an intermediate insulating region for thermally insulating the interior and exterior surface regions from each other, and a refrigerator assembly for refrigerating said interior space, said refrigerator assembly including evaporator means situated at and formed in part by said interior surface region of said wall means, condenser means situated at and formed in part by said exterior surface region of said wall means, and compressor means operatively connected to and communicating with said evaporator means and condenser means for circulating a refrigerant therethrough while reducing the temperature of the interior space with respect to the ambient atmosphere, said wall means including an exterior metal skin and condenser coils carried by the intermediate insulating region of said wall means and engaging said exterior metal skin to form said condenser means therewith, and said wall means including an interior metal skin and evaporator coils carried by the intermediate insulating region of said wall means and engaging said interior metal skin to form said evaporator means therewith, said insulating region including opposed outer surfaces formed with grooves which receive the coils of said condenser means and said evaporator means, and said coils being of a non-circular cross section and having opposed side edges between which said coils have a flat surface extending without interruption between said side edges and completely filling the area between said side edges, and said coils engaging said metal skins over the entire areas of said flat surfaces of said coils.

3. The combination of claim 2 and wherein an air-moving means is situated at the interior of said duct for directing air through said interior space to be refrigerated thereby.

4. The combination of claim 1 and wherein said wall means forms part of a container in which perishables such as food products and the like are stored.

6. The combination of claim 5 and wherein a heat-exchanger means is operatively connected with the conduit through which refrigerant flows from said evaporator means to said suction accumulator means and with the discharge of said compressor means through which refrigerant flows from said compressor means to said condenser means.

8. The combination of claim 1 and wherein said coils are of a semicircular cross section having a diameter formed by said flat surface of said coils and an outer convexly curved surface forming the remainder of said semi-circular cross section.