US 3446032 A
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Description (OCR text may contain errors)
May 27, 1969 w. BQTTUM HEAT EXCHANGER Filed March 10, 1967 EMWEMQEQQ INVENTOR.
I EDWARD W. BOTTUM.
WILSON, SETTL E BATCHELDER Al ATT'YS. CR 6 United States Patent 3,446,032 HEAT EXCHANGER Edward W. Bottum, 9357 Spencer Road, Brighton, Mich. 48110 Filed Mar. 10, 1967, Ser. No. 622,132 Int. Cl. F28f N06, N36
U.S. Cl. 62-513 1 Claim ABSTRACT OF THE DISCLOSURE The present invention relates to a heat exchanger for a refrigeration system, and more particularly to a heat exchanger for the exchange of heat between a relatively cold fluid and a relatively warm fluid, the heat exchanger employing improved means for placing the fluids in heat exchange relationship.
Background of the invention Heat exchangers are employed in refrigeration systems for the exchange of heat between fluids, generally the relatively cold refrigerant gases from the evaporator and relatively warm liquid refrigerant from the condenser. The refrigerant gas which is exhausted from the evaporator of the refrigeration system is relatively cold. The liquid refrigerant which is drawn from the condenser of a refrigeration system is relatively warm. In order to improve the efliciency of the refrigeration system, it is desirable to heat exchange the warm liquid with the cold gas. The heat exchanger of the present invention provides an improved means for efliciently effectuating the desired heat exchange. Other fluids are, however, also heat exchanged. For example, cold evaporator gas may be heat exchanged with warm compressor gas.
It is therefore an object of the present invention to provide an improved heat exchanger for a refrigeration system.
Another object of the invention is to provide a heat exchanger wherein the liquid refrigerant is caused to follow a helical path around an element through which the refrigerant gas passes, the helical path causing the liquid to have good contact with said element and also increasing the velocity of the liquid, both of which result in improved heat transfer.
A further object of the invention is to provide an element for the passage of refrigerant gas therethrough and refrigerant liquid thereover, the element having longitudinally extending flutes in the wall thereof to increase the heat transfer surface and also to improve the wiping action of the refrigerant as it passes thereover.
An additional object of the invention is to provide, in the element through which the refrigerant gas passes, an internally spiralled member which maintains the refrigerant gas in direct wiping action with the internal surface of the element.
A further object of the invention is to provide an increased heat transfer surface in the element through which the refrigerant gas passes.
Other objects of this invention will appear in the following description and appended claim, reference being had to the accompanying drawing forming a part of this specification wherein like reference characters designate corresponding parts in the several views.
In the drawing:
FIGURE 1 is a view in perspective of the heat exchanger of the present invention with a portion of the external casing broken away for the purpose of clarity and schematically illustrating the heat exchanger connected in a refrigeration system; and
FIGURE 2 is a view of the element within the heat exchanger through which the refrigerant gas passes with parts broken away for the purpose of clarity.
Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.
Refering to FIGURES 1 and 2, it will be noted that the heat exchanger 10 comprises an outer elongated tubular casing member 12 and an inner elongated casing member 14. The inner casing member 14 is fabrricated of a material having high thermal conductivity properties.
The outer casing 12 has an inlet 16 and an outlet 18. The inlet 16 is connected to, for example, the condenser of a refrigeration system while the outlet 18 is connected to, for example, the evaporator of a refrigeration system. Warm liquid refrigerant is drawn from the condenser and passes into the heat exchanger 10 via the inlet 16. The liquid refrigerant then passes over the outer surface of the inner casing 14 and exits from the heat exchanger via the outlet 18.
The inner casing 14 has a central portion 20 of reduced diameter. The portion 20 is spaced from the interior surfaces of the outer casing 12 to define a passageway for the flow of liquid refrigerant through the exchanger. The ends 22, 24 of casing 14 are enlarged and contact the interior surface of casing 12. The juncture thereof is sealed as by brazing or soldering. An inlet fitting 26 and an outlet fitting 28 extend from the casting 14. The juncture of the fittings 26, 28 with the casing 14 are sealed as by soldering or brazing.
It will be noted that the casing 14 has longitudinally extending flutes 30 spaced around the entire periphery thereof. The flutes 30 serve a dual purpose. Firstly, fluting of the casing 14 results in a larger surface area available for heat transfer. This is true both with respect to the liquid refrigerant which flows across the exterior surface and the refrigerant gas which flows across the interior surface. The flutes also provide a better wiping action of the fluids on the heat transfer surface. This improves the heat transfer coeflicient.
A helically wound coil 32 is provided on the reduced diameter portion 20 of the casing 14. The coil 32 defines, along with the casing surfaces, a helical passageway for flow of the liquid refrigerant. This results in directing the flow of liquid refrigerant as close to the fluted surface of casing 14 as possible and improves the wiping action of the liquid as it passes thereover. The liquid is forced to sweep the surface of casing 14 and cannot form into separate flow pockets or strata. The stratum closest to casing 14, in elfect, acts as an insulator and thereby decreases the heat transfer rate. Such strata may form if the liquid flows longitudinally across the surface of element 14 rather than helically therearound. An additional advantage in use of the coil 32 is that the passageway formed by the coil acts as a restriction to the flow of liquid. Restricting the flow results in increasing the velocity of flow. An increase in velocity is advantageous because improved heat exchange is achieved at higher velocities.
Referring to FIGURE 2, it will be noted that a spiral metallic strip 34 is provided within casing 14. The edges 36 of the strip 34 are in contact with the internal surfaces of the casing 14. The strip 34 extends from end portions 22, 24 across the length of the portion 20. The strip 34 forms a helical passageway for the flow of gas through the casing 14. This is advantageous in that it maintains the gas in direct wiping action with the internal fluted surface of casing 14 in a manner similar to the coil 32. This improves the heat transfer between the liquid flowing through casing 12 and the gas flowing through casing 14. Additionally, the spiral strip provides additional heat transfer area.
It will be noted that the strip 34 has transverse corrugations 36. The corrugations 36, in addition to providing a larger heat transfer surface, cause turbulence. This turbulence improves the contact between the gas and the heat transfer surfaces to result in increased heat transfer.
In the construction described, the liquid refrigerant enters through inlet 16 and exits through outlet 18 while the gas enters through inlet fitting 26 and exists through outlet fitting 28. This results in a counter-current flow of the gas and liquid. Such a counterflow results in the most eflicient heat transfer. However, the gas and liquid may flow in the same direction if this is desired for installation purposes.
The juncture of the casing 14 with the casing 12 has been disclosed as being brazed or soldered. Alternately, the ends of the casing 14 may be spun or swaged to result in a mechanically sound fluid tight connection. In such a construction, there are no internal joints. An end cap construction may also be used as an alternate to directly mechanically connecting casing members 12 and 14.
The casing 14 may be constructed of a material which is not easily corroded, such as copper. However, in view of the fact that casing 14 is entirely contained within casing 12, it may be fabricated of a material such as steel because it will not be subjected to corrosion or rusting caused by moisture or other materials in the ambient atmosphere.
FIGURE 1 illustrates the heat exchanger schematically connected into a refrigeration system. The inlet 28 of the heat exchanger 10 is connected to the outlet of an evaporator 38 via line 40. Cold refrigerant gas is thus injected into one end of the heat exchanger. The outlet 26 of the inner casing member 14 is connected to the inlet of compressor 42 via line 44. The outlet of the compressor 42 is connected to the inlet of a condenser 46 via line 48. The outlet of the condenser 46 is connected to the inlet 18 of the outer casing 12 via line 50. The outlet 16 of the outer casing 12 is connected to the inlet of the evaporator 38 via line 52.
It will be noted in the above-described system that the connections 16, 18, of the outer casing 12 are incorporated into the refrigeration system in a manner causing warm refrigerant liquid from the condenser 46 to flow from left to right as viewed in FIGURE 1, while the connections 26, 28 of the inner casing member 14 are incorporated into the refrigeration system to cause the cold refrigerant gas from the evaporator to flow from right to left as viewed in FIGURE 1, thus resulting in the desired countercurrent flow which results in maximum heat exchange.
Having thus described my invention, I claim:
1. In a refrigeration system including a condenser, a compressor, an evaporator and a heat exchanger, said heat exchanger functioning to cause heat exchange between the relatively cold gases from the evaporator and the relatively warm liquid from the compressor, said heat exchanger comprising an outer casing member, an inner casing member positioned therein, said inner casing member being fabricated from thermally conductive material, the inner casing member being spaced from the interior surface of the outer casing member, said inner casing member being fluted in the direction of fluid flow to provide both an interior and an exterior fluted surface to increase the heat transfer surface thereof and to assist in maintaining turbulent flow of fluid, a helically spiralled strip member Within said inner casing member to define, with the inner surface of said inner casing member, a helical path for the flow of fluid through said inner casing member, said strip member being transversely corrugated, a helical coil provided on the exterior surface of said inner casing member to define a helical passageway for the flow of fluid through said outer casing member, each of said casing members having an inlet and an outlet, the inlet of the outer casing member being connected to the outlet of the condenser, the outlet of the outer casing member being connected to the inlet of the evaporator, the inlet of the inner casing member being connected to the outlet of the evaporator and the outlet of the inner casing member being connected to the compressor.
References Cited UNITED STATES PATENTS 2,120,754 6/1938 Newton -154 3,177,936 4/ 1965 Walter 165-109 X FOREIGN PATENTS 481,806 10/ 1916 France. 1,208,314 1/ 1966 Germany.
ROBERT A. OLEARY, Primary Examiner.
A. W. DAVIS, Assistant Examiner.
US. Cl. X.R.