Heat exchanger core

Abstract: Disclosed is a heat exchanger core in which a fluid is caused to flow through a pipe body (11) rectangular in cross section so that the heat exchange is effected between the flowing fluid and a heat medium in contact with the outer walls of the pipe body (11). Within the pipe body (11), a plurality of projections (15A,15B) and/or grooves for flowing the fluid at an inclined angle with respect to the direction of the flow of the fluid (the axis of the heat exchanger core) and the streams flow through the inclined passages, respectively, and then are reversed in direction. Such a flow pattern is repeated so that the efficiency of heat transfer by conduction can be improved without the noticeable increase in pressure loss.

Description: The present invention relates to a heat exchanger core comprising the features as indicated in the precharacterising part of claim 1. Such a heat exchanger core is disclosed for example in FR-A-1 300 121. In these heat exchanger cores the heat exchange is carried out between a fluid flowing through a pipe and a heat medium outside of the pipe. The heat exchanger core is adapted for use in the evaporators of the air conditioning devices and refrigeration devices, the chemical apparatuses, the electronic equipment and the like. The heat exchanger core of the type described above is assembled with a header for flowing a fluid through the core so as to construct a heat exchanger and it is known a core called a heat transfer pipe in which the heat exchange is effected between a fluid flowing through a pipe and another fluid flowing outside of the pipe. Figs. 1 and 2 illustrate conventional heat exchanger cores, respectively, in which a plurality of fins 4A and 4B are joined to the upper wall 2 and the lower wall 3 in opposing relationship with each other of a pipe body 1 having a flat rectangular cross sectional configuration are spaced apart from each other by a suitable same distance. In the case of the heat exchanger core illustrated in Fig. 1, the fins A and B are extended in the direction perpendicular to the direction in which a fluid flows through the pipe body 1 while in the heat exchanger core illustrated in Fig. 2 the fins 4A and 4B are extended in the direction in which a fluid flows through the pipe body 1. The fin 4A extended from the upper wall 2 and the opposing fin 4B extended from the lower wall 3 are in vertically coplanar relationship with each other and in the vertical direction, a predetermined space 5 is defined between the each fin pair 4A and 4B extended from the upper and lower walls 3 and 4, respectively. In the case of the conventional heat exchanger cores of the types illustrated in Figs. 1 and 2, respectively, the heat transfer area of the inner surfaces of the pipe body 1 is increased, thereby increasing the heat transfer quantity, but the heat exchanger core of the type illustrated in Fig. 1, a fluid which flows through the pipe body 1 impinges against the fins 4A and 4B, resulting in vortex flows so that there arises the problem that compared with the increase of the heat transfer coefficient, the pressure loss is increased a little. In the case of the heat exchanger core of the type illustrated in Fig. 2, a plurality of fluid streams only flow straightly along the fins 4A and 4B in the pipe body 1 so that there arises the problem that heat transfer will not so increased even though the heat transfer surfaces are increased because the heat transfer coefficient is decreased. Japanese Laid-Open Patent No 113998/1981 or No 117097/1981 discloses another type of a heat exchanger core in which a plurality of spiral grooves are defined in parallel with each other over the inner surface of a cylindrical pipe body. However, in the case of the heat exchanger core of the type described above, due to a plurality of parallel spiral grooves within the pipe body, many vortex flows are formed within the pipe body so that there arises the problems that the pressure loss becomes higher and that the heat transfer coefficient is increased. Furthermore as a heat exchanger core used in the abovementioned electronic equipment, well known in the art is the so-called heat sink which dissipate heat from the heat generation component parts such as transistors, diodes, thyristor and the like which are mounted in an electronic device. Fig. 3 illustrates a conventional heat exchanger core of the type just described above. Electronic components parts which generate heats such as transistors, diodes, thyristors and the like 7 are threadably mounted on the upper surface of a metal base 6 of a core by means of screws 8, whereby a heat exchanger is constructed. A plurality of parallel elongated grooves 9 are formed in the undersurface of the base plate 6 and are spaced apart from each other by a suitable distance so that the upper side edges of rectangular fins 10 are snugly fitted into the elongated grooves 9. In the case of the heat exchanger of the type illustrated in Fig. 3, a plurality of air streams flow through the spaces defined by the adjacent fins 10 so that heat generated by the heat generating component parts 7 and transferred by conduction from the base plate 6 to the fins 10 is dissipated into the surrounding air. However in the case, the air which flows between the adjacent fins 10 will not be vortex flow but be laminar one so that there arises the problem that the heat transfer coefficient is low and therefore the heat transfer quantity by convention is not increased even though heat transfer surfaces are increased. FR-A-1,300,121 discloses a number of heat exchanger arrangements in which one or more channels are provided with fins or vanes to direct fluid flow at an angle to the channel axis for promoting a circulating flow. DE-A-1,160,975 shows a heat exchanger in which fluid flow channels are provided with discontinuous fins, each fin extending across the whole width of the channel. Arrangements are described in which these fins are angled to promote mixing. In view of the above, the primary object of the present invention is to provide a heat exchanger core which can substantially solve the above and other problems encountered in the conventional heat exchanger cores, and in which the heat exchanger core can have a high degree of performance and can be made compact in size and light in weight and highly reliable and dependable in operation. Accordingly, the present invention provides a heat exchanger core of the type in which fluid is caused to flow through a pipe body so that the heat exchange takes place between said fluid and a heat medium in contact with the pipe body, the pipe body being of rectangular cross-section and having a plurality of parallel grooves formed on the inner surface of two, opposing interior walls of the pipe body, the grooves being substantially equally inclined at an acute angle to the direction of fluid flow and arranged in the same direction on said opposing interior walls; characterised in that each groove on one of said opposing interior walls is arranged opposite and parallel to a respective groove on the other of said opposing walls and each of said grooves extends across the entire respective wall with the longitudinal extremities of the groove contacting the opposed side walls of the pipe body; and in that said angle is in the range of 20 to 60 degrees. The invention is more fully described with reference to the accompanying drawings in which: Figs. 1, 2 and 3 are perspective view of three prior art heat exchanger cores, respectively; Fig. 4 is a perspective view, partly broken, of a preferred embodiment of a heat exchanger core in accordance with the present invention; Fig. 5 is an end view of Fig. 4; Fig. 6 is a view used to explain the mode of operation of the preferred embodiment shown in Figs. 4 and 5; and Fig. 7 is a perspective view, partly cut out, of a modification of the preferred embodiment shown in Figs. 6. Referring next to Figs. 4 - 6, a preferred embodiment of the present invention adapted for use in large-sized heat exchanger will be described. The embodiment has a block-shaped housing 20 rectangular in cross section made of metal or alloy having a high degree of thermal conductivity such as aluminium alloy, copper, brass or the like. Within the housing 20, a plurality of flow passages 23A connected to an upper surface 21 and a plurality of flow passages 23B connected to a lower surface 22 are alternately disposed in parallel with each other. Both ends of the flow passages 23A and 23B are opened so as to flow a fluid in the horizontal direction. The upper opened end of each flow passage 23A is closed by a cover 24A which in turn is securely attached to the upper surface 21 while the lower open end of each flow passages 23B is closed by a cover 24B which in turn is securely attached to the lower surface 22. The opposing surfaces 25A and 25B of the adjacent flow passages 23A and 23B are formed with a plurality of elongated grooves 26A and 26B which have an arcuate cross sectional configuration and which are in parallel with each other. Each of the elongated grooves 26A defined at one inner surface 25A and each of the elongated grooves 26B defined at the other inner surface 25B are inclined at a same predetermined angle with respect to the horizontal direction in which the fluid flows so that the lower part of each grooves 26A, 26B with respect to the direction in which the fluid flows is looked downward, but are arrayed in the parallel direction on the inner surfaces 25A and 25B. Moreover the lower part of each grooves 26A, 26B may be looked upward. Furthermore the distance of the gap defined between the adjacent elongated grooves 26A at the inner surface 25A is equal to that of the gap between the adjacent elongated grooves 26B and the elongated grooves 26A and the elongated grooves 26B are in opposing relationship with each other in the horizontal direction. The angle of inclination of the elongated grooves 26A and 26B is in the range of 20 - 60° with respect to the direction in which the fluid flows. In order to construct the housing 20, metal-sheet blanks may be formed with the elongated grooves 26A and 26B by a press or embossing apparatus and then bent. Alternatively, by casting or an extruding machine, a plurality of metal-sheet blanks are formed with the elongated grooves 26A and 26B and the metal sheets thus processed may be spaced apart from each other by a suitable distance joined by an adhesive or braze welding. With the heat exchanger core according to the preferred embodiment of the present invention, a fluid to be subjected to the heat exchange process is caused to flow through the elongated passages 23A or 23B while a fluid which receives heat from the fluid flowing through the passages 23A is made to flow through the passages 23B or 24B, whereby the heat exchange is carried out between the two fluids. When the fluid is caused to flow in the direction indicated by the bold-line arrow, part of the fluid flows through the elongated grooves 26A and 26B as indicated by the solid-line arrows so that the heat transfer surface is increased in area. Furthermore, the fluids are caused to flow in the direction inclined at a predetermined angle with respect to the direction of the elongated grooves 26A and 26B through which the fluid flows. Thereafter within the flow passages 23A and 23B, the fluids impinge on the housing or the cover 24B and are redirected in the direction of the centerlines between the width of the flow passages 23A and 23B. As a result, the fluid is redirected in the direction which is line symmetrical with respect to the direction in which the elongated grooves 26A and 26B extend, with the direction indicated by the bold-like arrow being the axis of symmetry so that the fluid is caused to flow in the direction inclined at a predetermined angle with respect to the flow passages 23A or 23B. Next the fluid impinges on the housing or the other cover 24A and is divided into the right and left streams. Thereafter the fluid is redirected into the elongated grooves 26A or 26B to flow in the direction inclined. The streams of the fluid are mixed and are brought into contact with the whole wall surfaces of the flow passages 23A and 23B in the manner described above. According to the preferred embodiment, as described above, the fluids are caused to flow in the inclined direction in line symmetry relationship within the flow passages 23A and 23B, respectively, except the elongated grooves 26A and 26B and through the elongated grooves 26A and 26B in the flow passages 23A and 23B. As a result, the relative speed of the fluid becomes faster and the heat transfer coefficient is considerably increased as compared with the increase of the pressure loss. The fluids are mixed in the flow passages 23A and 23B so that the fluid temperatures can be maintained uniformly so that the efficiency of heat transfer can be remarkably improved. Fig. 7 illustrates a modification of the preferred embodiment. According to this modification, a plurality of heat exchanger cores described above with reference to Figs. 4 - 6 are laminated in such a manner that the flow passages 23A and 23B in the adjacent cores become perpendicular to each other. A heat radiating fluid or a heat receiving fluid is caused to flow through the flow passages 23A and 23B extended in one direction while a heat receiving fluid or a heat radiating fluid is caused to flow through the passages 23A and 23B extended in the other direction. The upper surface of the uppermost housing 20 is covered by a cover plate 24A while the undersurface of the lowermost housing 20 is covered with a cover plate 24B and a cover plate 24C is interposed between the adjacent housings 20 between the uppermost and lowermost housings 20. With the modification with the above-described construction, heat transfer can be carried out at a high degree of efficiency. According to this modification, in addition to the elongated grooves 26A and 26B in each of the flow passages 23A and 23B, projections are interposed between the adjacent elongated grooves 26A and 26B so that each flow passage may have a waveform cross sectional configuration. From the standpoint of fabrication, a flow passage having a waveform cross sectional configuration is superior to a flow passage formed with a plurality of grooves and a plurality of projections, can be used a method in which a metal-sheet blank is formed into a plate having a waveform cross sectional configuration by pressing and the plate thus obtained is folded.

Claims: A heat exchanger core of the type in which fluid is caused to flow through a pipe body (23A, 23B) so that the heat exchange takes place between said fluid and a heat medium in contact with the pipe body, the pipe body (23A, 23B) being of rectangular cross-section and having a plurality of parallel grooves (26A, 26B) formed on the inner surface of two, opposing interior walls (25A, 25B) of the pipe body, the grooves (26A, 26B) being substantially equally inclined at an acute angle to the direction of fluid flow and arranged in the same direction on said opposing interior walls (25A, 25B); characterised in that each groove on one of said opposing interior walls (25A) is arranged opposite and parallel to a respective groove on the other of said opposing walls (25B), and each of said grooves (26A, 26B) extends across the entire respective wall (25A, 25B) with the longitudinal extremities of the groove contacting the opposed side walls of the pipe body (23A, 23B); and in that said angle is in the range of 20 to 60 degrees. A heat exchanger core according to Claim 1, in which said grooves (26) have smooth curved surfaces. A heat exchanger core according to Claim 2, in which said grooves (26) are semi-circular in cross-section.

Inventors: TAKEMURA HIROSHI, TERASAKI KAZUO, TAKEMURA, HIROSHI, TERASAKI, KAZUO
Applicants: MITSUBISHI ALUMINIUM, MITSUBISHI ALUMINUM KABUSHIKI KAISHA
Application year: 1989
Main classification: F28F1
IPC codes: F28F1, F28D9, F28F13, F28F3