US 3335790 A
Description (OCR text may contain errors)
Aug. 15, 1967 ARPAD ARANYI ETAL 3,335,790
HEAT EXCHANGER WITH CROSSING HELICOIDAL TUBES Filed March 18, 1966 Arpa'cl Ara'nyi IN VE N TORS Attorney Guszfa'v Gergely United States Patent 6 Claims. 61. 165-109 ABSTRACT OF THE DISCLOSURE Heat exchanger having a cylindrical housing with an inlet and an outlet for a first fluid and substantially completely filled with a packing formed by crossing coaxial layers of oppositely turned helicoidal tubes forming within the channel of the housing baflles with relatively narrow interstitial openings imparting turbulence to the entire mass of liquid passing through the channel. The tubes 7 surround a core.
Our present invention relates to a heat exchanger in which two fluids of initially different temperatures pass in close proximity to each other, but along different paths, for the purpose of heating or cooling one of the fluids at the expense of the other.
A typical field of application of such heat exchangers is in the cooling of lubricating oil taken from and returned to the crankcase of an automotive engine or the like.
Other fields of use are in food-processing plants, in the chemical industry, in steam engines, in systems for supplying oil as a fuel or a motive fluid to internal-combustion (e.g. Diesel) engines or to hydraulic machinery.
. In heat exchangers in which one of the fluids (e.g. oil) is considerably more viscous than the other, it is customary to let this fluid pass along a substantially straight path and at a relatively slow rate through an elongated, generally cylindrical chamber and to conduct the other, more mobile fluid (e.g. water, steam, air or some other gas) through one or more pipes of undulating or helical shape designed to increase the residence time of the latter fluid in the chamber. It is also the practice, for more eflicient heat exchange, to let the two fluids move in counterflow to each other. a
These techniques, however, are not always completely satisfactory, particularly when heat is to be extracted from a relatively viscous liquid, such as oil, having a low heattransfer coefiicient (a). Such a liquid, on being chilled by contact with the thermally conductive pipes carrying the colder fluid, tends to congeal into a relatively sluggish boundary layer covering the outer pipe surfaces and mini: m-izing, by reason of its own low thermal conductivity, the transfer of heat from the more remote portions of the hot liquid to the cooling pipes. This not only lowers the efliciency of the system but is objectionable in many instances on account of the lack of homogeneity of the discharged liquid with reference to, say, its lubricating qualities.
It is, therefore, the general object of the present invention to provide an improved heat exchanger which avoids the aforestated disadvantages and which is particularly, though not exclusively, useful in conjunction with viscous fluids of low heat-transfer coeflicient.
This object is realized, in accordance with our invention, by the provision of a heat exchanger whose elongated, preferably cylindrical housing, forming a channel for a first fluid, contains a thermally conductive structure including a plurality of coaxial helicoidal elements of alternating direction of pitch, this structure being constituted at least in part by a conduit or conduits carrying a second fluid in heat-exchanging relationship with the first fluid; the helicoidal elements, which may be fluid-carrying pipes and/or ribs mounted on the outer surfaces of such pipes, subdivide the elongated channels into a plurality of intercommunicating helicoidal zones which deflect the first fluid from its linear path and force it to move with both radial and tangential velocity components so that turbulence is imparted to this fluid and the deposition of a sluggish boundary layer is substantially prevented.
The term helicoidal is used in this context to describe coiled configurations of a generally helical nature wherein the spacing and other dimensions of successive turns are not critical and need not be uniform.
FIG. 1 is a longitudinal sectional view of a heat eX- changer according to a first embodiment;
FIG. 2 is a fragmentary view of a second embodiment, shown partly in axial section and partly in elevation;
FIG. 3 is a partly sectional and partly elevational view of a third embodiment; and
FIG. 4 is a fragmentary view of a modification of the structure shown in FIG. 2.
In the several views of the drawing, A designates a first fluid, which may be a relatively viscous liquid such as oil, whereas B identifies a second fluid which may be a more mobile liquid or gas.
In FIG. 1 there is shown a heat exchanger whose housing 1 has a cylindrical peripheral wall with frustoconical ends terminating in a pair of axially aligned ports 1a, 1a for the admission and discharge of the fluid A. Extending axially within the housing 1, and supported therein by means of radial stays 2a, is a solid elongated core 2 of a diameter substantially equal to that of the ports 1a, 1a. Core 2 is surrounded by an inner tier of helicoidally interleaved pipes 3 of good thermal conductivity which are spaced apart to define a multithread helicoidal path around the core; these pipes 3, in turn, are encased within a second tier of similar pipes 4 which are coiled in the opposite direction but have substantially the same spacing and pitch angle as the former. The multithread helicoidal path defined by the pipes 4 communicates at numerous locations with the flow path formed by the pipes 3 so that the fluid stream A will distribute itself throughout the housing and will be turbulently deflected in three dimensions before exiting from outlet port 1a.
A second fluid B may traverse all the interleaved and nested pipes 3, 4 in series or in parallel; as shown in FIG. 1, fluid enters one of the inner conduits 3 and leaves one of the outer conduits 4 in the vicinity of port 1a so that part of this fluid flows countercurrent to fluid A.
In FIG. 2 there is shown a modified housing whose cylindrical peripheral wall 21 is formed at opposite ends with lateral inlet and outlet ports 21b (only one shown) for the fluid stream A; a conical transverse partition 6 at each end of cylindrical wall 21 has apertures 21a leading to respective helicoidal pipes 3', 3", 4 and 4" which surround a straight central tube v5 and are disposed in four nested tiers of alternate pitch direction. Adjoining each end of the cylindrical housing wall 21, and secured to it by rivets or other fasteners 22, is a frustoconical end wall 7 with a respective entrance or exit port, only the end wall carrying the entrance port 7a being shown in this figure. Fluid B, introduced into port 7a, enters the confronting open end of tube 5 as well as the apertures 21a leading to the pipes 3', 3", 4' and 4", traversing all these conduits in its passage toward the exit port at the opposite end of the housing. The thermally conductive structure constituted by these conduits again serves to deflect the fluid A, moving in counterflow to fluid B, in a swirling flow onto a path of many helicoidal and radial branches.
The embodiment of FIG. 3 comprises a housing 31, generally similar to housing 1 of FIG. 1, whose frustoconical end walls are penetrated by inlet and outlet ducts 8, 8 for the fluid A that open into an inner space defined by a generally cylindrical partition 9 which parallels the wall of housing 31 and forms therewith an annular channel 32 for the passage of fluid B; the latter is admitted into this channel by way of a lateral inlet port 31b, and, in flowing toward a lateral exit port 3111' at the opposite housing end, partly traverses a pipe 10 which extends for the most part axially within housing 31 as a bypass to channel 32. The outer periphery of pipe 10 and the inner periphery of partition 9 carry respective helicoidal ribs 11, 12 of opposite pitch direction which again divide the space occupied by fluid A into a plurality of nested helicoidal zones. Naturally, the entire integral structure 9-12 is made of a highly heat-conductive metal, e.g. copper or stainless steel, to facilitate heat exchange between the two fluids.
The provision of helicoidal fins or ribs on a conduit for fluid B, designed to deflect the external fluid A as illustrated in FIG. 4 a modification of the system of FIG. 2 wherein a central tube 45, provided with helicoidal ribs 45a, replaces the plain tube 5 surrounded by the inner tier of helicoidal pipes 3. Moreover, if desired, these helicoidal pipes (or those of the system of FIG. 1) could also be provided, in whole or in part, with such external helicoidal ribs.
A heat exchanger according to this invention may be directly connected, by its axial ports such as those shown at 1a, 1a, or 8, 8', in a pipeline carrying one of the fluids to be heated or cooled. We have found that, by virtue of the present improvement, the volume of such heat exchangers is only about a third or a fourth of that of conventional devices of comparable heat-exchanging capacity and that the rate of flow for the control fluid B is similarly reduced.
It may be mentioned that a system of the type as shown in FIG. 2, with separate cylindrical and frustoconical housing sections 21 and 7, may be extended at will by the insertion of addional cylindrical sections through which the fluid B passes in succession; fluid A may be led into the several housing sections by suitable external connections between their respective side ports 21b. Such a system may also be used, for example, as a water heater of considerably greater compactness than conventional boilers, with the water (fluid B) entering and leaving axially via ports 7a and manifolds 6 while the hot combustion gases (fluid A) from a fire chamber are introduced and withdrawn laterally via ports 21b. Conversely, the system of FIG. 2 may also be utilized as a condenser for live steam, with cooling water B introduced at 7a and with the discharge port 21b turned downwardly to serve as a drain for condensate A. A further use would be in a refrigeration or air-conditioning system with the air circulated as the fluid A while a suitable coolant is employed as the fluid B. Naturally, the devices shown in FIGS. 1 and 3 may be utilized in analogous manner for similar purposes.
The system of FIG. 3 is particularly adapted for the cooling of gases. Fluid A, for example, may be a gas to be fractionated by selective condensation of some higherboiling constituent thereof.
The arrangements specifically described and illustrated are, of course, capable of various modifications without departing from the spirit and scope of our invention as defined in the appended claims.
1. A heat exchanger comprising an elongated housing forming a channel for a first fluid, first inlet and outlet means on said housing communicating with said channel, thermally conductive conduit means traversing said housing in a generally longitudinal direction and forming a path for a second fluid in heat-exchanging relationship with said first fluid, and second inlet and outlet means on said housing at the ends of said path, said conduit means forming part of a thermally conductive structure including a plurality of alternately crossing coaxial helicoidal tubes in turns of opposite senses which extend within said channel between said second inlet and outlet and subdivide said channel into a plurality of intercommunicating baflies whereby turbulence is imparted to said first fluid, said coaxial helicoidal tubes forming a packing substantially filling said channel and forming narrow interstices therebetween for the passage of said first fluid.
2. A heat exchanger as defined in claim 1 wherein said housing has a substantially cylindrical peripheral wall and a pair of substantially conical end walls adjoining said peripheral wall, said end walls having vertices provided with ports forming part of one of said inlet and outlet means for the admission and discharge of one of said fluids.
3. A heat exchanger as defined in claim 1 wherein said structure includes a central member surrounded by said tubes and extending axially within said peripheral walls.
4. A heat exchanger as defined in claim 3 wherein said member is a solid core.
5. A heat exchanger as defined in claim 3 wherein said member is a tube open toward said ports.
6. A heat exchanger as defined in claim 2 wherein said ports form part of said first inlet and outlet means, said conduit means being provided with terminations constituting said second inlet and outlet means and extending laterally from said housing for the introduction and withdrawal of said second fluid.
References Cited UNITED STATES PATENTS 1,769,265 7/1930 Labus 163 X 1,852,490 4/1932 Sullivan 165156 X 1,893,484 1/1933 Belt 1651S6 X 2,888,251 5/1959 Dalin 165-156 X FOREIGN PATENTS 453,328 12/1948 Canada.
621,980 9/1961 Canada.
585,917 11/1958 Italy.
ROBERT A. OLEARY, Primary Examiner. A. W. DAVIS, Assistant Examiner.