US 3473348 A
Description (OCR text may contain errors)
3 Oct. 21, 1969 E. W. BOTTUM HEAT EXCHANGER Filed March 31, 1967 8 CRAIG.
EDWARD W BOTTUM.
WILSON, SETTLE, BATCHELDER ATT'YS.
United States Patent US. Cl. 62-513 1 Claim ABSTRACT OF THE DISCLOSURE A heat exchanger is provided with inner and outer concentric tubular casings defining two passageways. An inlet and an outlet are provided for each passageway to allow flow of a hot fluid through one passageway and flow of a cooler fluid through the other passageway to provide heat exchange between the fluids. A fin-like structure is provided within the inner casing. The fins may be in the form of a single heat conductive member comprised of a series of accordian folds arranged around the axis of the inner casing to provide radially extending portions in thermal contact with the inner casing.
Background of the invention Heat exchangers are employed in refrigeration systems for the exchange of heat between, for example, rela tively cold refrigerant gases and relatively warm liquid refrigerant. Heat exchangers are also employed for heat exchange of two liquids or two gases. In one type of heat exchanger for this purpose, one of the refrigerant fluids may flow through an inner tubular casing and the other refrigerant fluid may flow through a space between the inner casing and an outer tubular casing which surrounds it. For some applications, a more efiicient heat exchanger is desired, and the present invention provides an improved heat exchanger for efliciently accomplishing the desired heat exchange.
Summary of the invention A heat exchanger having inner and outer tubular casings as described above is provided with a fin-like structure within and in thermal contact with the inner casing for increasing the effective surface area of that casing and thus increasing the efficiency of heat exchange. In one embodiment the fin-like structure is in the form of two channel members which are generally U-shaped in section, the channel members being joined back to back at the center of the inner casing and having legs which extend to and contact the inner casing. In another embodiment, the fin-like structure takes the form of an accordian folded piece of metal which is arranged around the axis of the inner casing and has generally radially extending portions in thermal contact with the inner casing. Both embodiments increase the efficiency of heat exchange and yet are relatively easy to fabricate and assemble in a heat exchanger.
Accordingly, it is 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 in which a fluid flowing through a tubular casing of the exchanger contacts a fin-like structure which extends the surface area of the casing and thus improves the heat transfer.
A further object of the invention is to increase the effective surface area of a tubular casing in a heat exchanger by the use of channel members provided within the tubular casing.
Another object of the invention is to increase the effective surface area of a tubular casing in a heat ex- Ice changer by the use of a member having accordian folds arrayed about an axis of the casing.
Other objects of this invention will appear in the following description and appended claim, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.
On the drawings:
FIGURE 1 is a longitudinal sectional view of a heat exchanger and schematically illustrating the heat exchanger connected in a refrigeration system in accordance with one embodiment of the invention;
FIGURE 2 is a cross sectional view of the embodiment of FIGURE 1 showing an accordian folded member within an inner casing;
FIGURE 3 is a longitudinal sectional view of a heat exchanger in accordance with another embodiment of the invention; and
FIGURE 4 is a cross sectional view of the embodiment of FIGURE 3 showing two back to back channel members within an inner casing.
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 drawings, 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.
As shown on the drawings:
The heat exchanger 10 of FIGURES l and 2 include an outer tubular casing 12 and an inner tubular casing 14 disposed concentrically within the outer casing. A core 16, which may be a rod or a tube, extends axially through the center of the inner casing 14, and where the core 16 is in the form of a tube as illustrated in FIGURES l and 2, the ends of the tube are closed by plugs 19 and 20 so that no flow takes place through the center of the core 16. The space between the core 16 and the inner tubular casing 14 provides one passageway through which a refrigerant fluid may flow, and the space between the inner tubular casing 14 and the outer tubular casing 12 provides an outer passageway through which another refrigerant fluid may flow.
In the particular heat exchanger being described by way of example, hot refrigerant liquid flows through the outer passageway 18 and cold refrigerant gases flow through the inner passageway 17, andheat exchange between these two fluids takes place through the wall of the inner tubular casing 14. It is desirable to flow the warmer fluid through the outer passageway 18 because the outer tubular casing 12 is then warm enough to preclude condensation of moisture from the ambient atmosphere onto casing 12, and this avoids rusting problems. Most of the inner tubular casing 14 is not exposed to the atmosphere, so condensation on that tube is also avoided. Since rusting is avoided, the outer and inner casings 12 and 14 at the inner core 16 may be made of steel. A copper fitting may be used on the exposed inlet of the inner casing to completely avoid the corrosion problem.
Two end caps 22 and 24 are provided, and the end caps have larger diameter ends 26 and 28 and smaller diameter ends 30 and 32. The larger diameter ends 26 and 28 fit over the outer tubular casing 12 at opposite ends thereof, and the smaller diameter ends 30 and 32 receive the inner tubular casing 14 and hold it in a centered position within the outer tubular casing 12. There is a close fit between the smaller diameter ends 30 and 32 of the caps 22 and 24 respectively and the inner tubular casing 14, and this joint may he brazed so that the casing 14 is held firmly in place. An inlet tube 32 and an outlet tube 34 extend through the outer tubular casing 12 respectively and communicate with the outer passageway 18 within outer tubular casing 12. Thus, hot liquid refrigerant enters the casing 12 through inlet tube 32, flows longitudinally of casings 12 and 14 through the outer passageway 18, and leaves outer casing 12 through the outlet tube 34. Cold gaseous refrigerant enters the inner tubular casing 14 at the right-hand end thereof as viewed in FIG- URE l, flows to the left through inner passageway 17 and leaves the inner casing 14 at the left-hand end thereof as viewed in FIGURE 1. Thus, the ends of the inner tubular casing 14 provide an inlet and an outlet for the inner passageway 17.
Within the inner passageway 17 there is a fin-like structure 36 which physically and thermally contacts the inner tubular casing 14 and also the core 16. The configuration of this fin-like structure 36 is shown best in FIGURE 2, and it may be seen there that structure 36- is in the form of a heat conductive member which is comprised of a series of accordian folds arrayed around the central axis of the tubular casings in the inner passageway 17. The structure 36 thus has a plurality of radially extending portions such as 38 and 40, curved portions 42 which contact the core 16 and additional curved portions 44 which contact the inner tubular casing 14. The edges of structure 36 at the ends thereof may be bent over to form tabs 45 which impart some turbulence to the gas flowing through the inner passageway. When the cold gaseous refrigerant passes through the inner passageway 17, it contacts the surfaces of the inner casing 14, the heat conductive structure 36, and the core 16. Heat is transferred from the hot liquid flowing through passageway 18 to the surfaces just referred to and is absorbed by the cold gases. Thus, the structure 36 and the core 16 serve to increase the effective surface area of the inner casing 14 to increase the rate of heat transfer to the cold gaseous refrigerant.
FIGURE 1 illustrates the heat exchanger schematically connected into a refrigeration system. The inlet 102 of the heat exchanger 10 is connected to the outlet of the source of cool refrigerant gas 104, normally an evaporator, by line 106. Cold refrigerant gas is thus injected into one end of the heat exchanger. Line 112 leads from the outlet 108 of the inner casing member 14 and is normally connected to the inlet of a compressor. The outlet of the source of warm refrigerant liquid 114 is connected to the inlet 32 of the outer casing 12 via line 118. Line 120 leads from the outlet 34 of the outer casing 12 and is normally connected to the inlet of the system evaporator.
It will be noted in the above-described system that the connections 32, 34 of the outer casing 12 are incorporated into the refrigeration system in a manner causing warm refrigerant liquid from the condensor 114 to flow from left to right as viewed in FIGURE 1, while the connections 102, 108 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 FIG. 1, thus resulting in a desirable counter-current flow which results in maximum heat exchange.
It will be understood, of course, that the utility of the heat exchanger 10 is not limited to flow of hot liquid through passageway 18 and cold gases through passageway 17. The gases could flow through passageway 18 and the liquid through passageway 17 if desired. Also, the exchanger could be used to heat exchange two liquids or two gases if desired. The exchanger 10, however, is particularly well suited to exchange heat between hot liquid refrigerant flowing through passageway 18 and cold gaseous refrigerant flowing through passageway 17.
Another embodiment of the invention is shown in FIGURES 3 and 4. The overall const uction of thi embodiment is similar to the embodiment of FIGURES 1 and 2, but a different type of fin structure is provided in the heat exchanger as will become apparent. The heat exchanger 50 of FIGURES 3 and 4 includes an outer tubular casing 52 and an inner tubular casing 54 supported concentrically within the outer casing by the end caps 56 and 58. The end caps 56 and 58 have larger diameter ends 60 and 62 which fit over the outer tubular casing 52 and smaller diameter ends 64 and 66 which receive the inner tubular casing 54 and hold it in place. There is an outer passageway 68 between casings 52 and 54 and an inner passageway 70 within the inner casing 54.
Tubes 72 and 74 extend through the wall of outer casing 52 and provide an inlet and an outlet for the outer passageway 68. Thus, hot liquid refrigerant can flow in inlet tube 72, through the passageway 68 and out through the outlet tube 74.
An inlet tube 76 fits on the right-hand end of inner tubular casing 54, and an outlet tube 78 fits on the lefthand end of the inner tubular casing 54. Cold gaseous refrigerant flows in through inlet tube 76, through the inner pasageway 70 and out through the outlet tube 78. Heat transfer takes place through the wall of the inner tubular casing 54.
Fitting within the inner tubular casing 54 is a heat conductive structure 80 which provides additional effective surface area for the inner tubular casing 54. This structure 80, which may be seen best in FIGURE 4, consists of two channel member 82 and 84. The channel members are substantially U-shaped in cross section and have back portions 86 and 88 which abut each other and which are fastened together as by welding. The legs 90, 92, 94 and 96 of the channel members extend outwardly from the back portions 86 and 88 to the inner tubular casing 54. The leg members just referred to are in physical and thermal contact with the inner tubular casing 54 and also conduct heat supplied through that casing wall. Cold refrigerant gas flowing through the inner passageway 70 contacts the channel members 82 and 84 as well as the surface of the casing member 54, and heat supplied from the hot refrigerant liquid flowing through the outer passage 68 is transferred through casing 54 and channel members 82 and 84 t0 the cold refrigerant gases. The channel members 82 and 84 extend longitudinally from the inlet tube 76 to the outlet tube 78 and thus extend over the full length of the inner passageway 70. The edges at the ends of the channel members may be bent over to provide tabs 98 and 100 which serve to deflect the flow of gas through the inner passageway to make that flow somewhat turbulent and thereby increase heat transfer.
It may be noted that the inlet and outlet tubes 72 and 74 for the outer passageway 68 have their mouths 73 and 75 directed laterally of the tubular casings 52 and 54. This is for the purpose of directing the incoming gas along a circular or helical path as it comes into the outer passageway 68 and as it travels along that passageway and flows out through the outlet tube 74. The mouth portions 33 and 35 of the inlet and outlet tubes 32 and 34 of the embodiment of FIGURES l and 2 may also be directed in this manner for the same purpose. The tubes 32, 34, 72 and 74 may be simply cut at an angle to provide the laterally directed mouth portions, or the mouths of the tubes may be bent at to the bodies thereof to properly orient the mouths.
Thus, the invention provides a heat exchanger which exhibits improved heat transfer due to the relatively great surface area provided in one of the passageways for flow of fluid. The added surface area may be provided by the use of a fin-like structure as has been described, and the fin structure may take the form of channel members or an accordian folded member or some other related configuration which provides increased surface area. The heat exchanger is easy to fabricate and assemble, and it should have a long operating life.
1. In a refrigeration system including a source of warm refrigerant liquid, a source of cool refrigerant gas, and a heat exchanger, said heat exchanger functioning to cause heat exchange between the relatively cold gases and the relatively warm liquid, said heat exchanger comprising an outer casing member, an inner tubular casing, means supporting said casings with said inner casing concentrically within said outer casing and spaced radially therefrom, said casings being made of thermally conductive material and at least said outer casing being fabricated of steel, said casings defining a first passageway therebetween and a second passageway within said inner casing, an inlet and an outlet for each of said passageways to allow flow of warmer fluid through the first passageway and flow of cooler fluid through the second passageway to provide for heat exchange between said fluids, said inlet and said outlet for said first passageway each comprising a tube extending through said outer casing and terminating in a mouth directed laterally of said first pas sageway for providing a helical flow of fluid about and along said first passageway, a heat conductive member comprising a plurality of accordion folds arranged about the axis of said inner casing and having a plurality of radially extending portions in thermal contact with said inner casing so that said member provides extended surface area for said inner casing to contact fluid flowing through said second passageway, said heat conductive member extending longitudinally of said inner casing between said inlet and outlet thereof, a core of thermally conductive material extending along the axis of said inner casing and extending through the center of and in thermal contact with said heat conductive member, the inlet of the outer casing member being connected to the outlet of the source of warm refrigerant, and the inlet of the inner casing member being connected to the outlet of the source of cool refrigerant.
References Cited UNITED STATES PATENTS 2,091,119 8/1937 Saint-Jacques l56 X 2,135,235 11/1938 Hurford et al. 165154 X 2,506,595 4/1950 Preston 165-156 2,698,162 12/1954 Riesgo 165--l54 2,797,554 7/ 1957 Donovan 62513 X 2,847,193 8/1958 Carter 165-156 X FOREIGN PATENTS 911,987 12/ 1962 Great Britain.
977,455 12/ 1964 Great Britain. 1,208,314 1/ 1966 Germany.
ROBERT A. OLEARY, Primary Examiner A. W. DAVIS, Assistant Examiner US. Cl. X.R. 165-154, 156, 179