Heat-exchanger coil assembly and complex thereof

Abstract: A plurality of heat-exchanger coils (9) each having a different winding diameter are provided between a header (2) of the inlet side and a header (3) of the outlet side so that the two headers are in communication with each other. The heat-exchanger coil assembly is constructed so that coils of smaller winding diameter are surrounded by coils of larger winding diameter.

Description: The present invention relates to a heat-exchanger coil assembly and a complex thereof, and more particularly to a heat-exchanger coil assembly for exchanging heat between a heat-exchanger medium accommodated in a body of a heat exchanger and a heat exchanger medium flowing in a coil. Generally a heat exchanger is based on a pipe system or a plate system, the pipe system being used when pressure resistance in the heat-exchanger medium is required. Various types of heat exchanger are based on the pipe system such as those based on a coil system or a multiple tube system. Of these, a heat exchanger based on a coil system is widely used for various purposes because the construction is simple, but the heat transfer area is smaller as compared to the tank (body) capacity, so that it is used as a heat exchanger having a relatively small capacity. Fig. 15 shows a conventional type of heat exchanger based on the coil system. A heat-exchanger coil 101 wound in a spiral form around a heat exchanger tube is provided in a body section 104, and an inlet pipe 102 and an outlet pipe 103 are provided at both ends of the coil 101. A heat-exchanger medium such as a liquid or a gas is introduced through the inlet pipe 102 into the body section 104, passes through the heat-exchanger coil 101, and is discharged through the outlet pipe 103 from the body section 104. While the heat-exchanger medium is flowing through the coil 101, heat is exchanged through the coil wall between a heat-exchanger medium in the coil 101 and that in the body section 1. In order to increase the quantity of heat being exchanged and enhance the heat-exchanging capability of the heat exchanger based on the coil system described above, it is necessary to make the heat transfer area larger by increasing the number of turns in the coil 101. However, this leads to a loss of head due to the larger friction resistance of the tube, thus requiring a larger capacity pump on the inlet side to keep the flow rate at a specified level. It is possible to exchange a larger quantity of heat with the apparatus as shown in Fig. 17. In this apparatus, there is provided a header 105 in the heat-exchanger medium inlet side and a header 106 in the heat-exchanger medium outlet side 106, and a plurality of inlet pipes 102 as well as outlet pipes 103 for the heat-exchanger coils 101 are connected respectively to the headers 105, 106. In this case, however, the efficiency is not always good. As the capacity of the body section becomes larger, so too does the space required for the installation of the heat exchanger. Fig. 18 is a cross-sectional view illustrating a U-shaped heat-exchanger, which is of the multiple tube heat-exchanger type. This type of heat exchanger comprises a plurality of U-shaped tubes 109 each having a different length respectively provided in the body section 107. Each of the U-shaped tubes 109 is supported by a metal support 110 within the body section 107, with the end sections of both the inlet and outlet sides of the tubes 109 being fixed to a header fixing plate 108. One heat-exchanger medium flows into the body section 107 from an entrance 111 and flows out from an exit 112. The other heat-exchanger medium flows into a header 114 on the inlet side from an entrance 113, flows through the plurality of U-shaped tubes 109 and goes into a header 115 on the outlet side, and flows out from the exit 116. The other heat-exchanger medium exchanges heat with the heat-exchanger medium in the body section 107 when flowing in the U-shaped tubes 109. As a plurality of U-shaped tubes 109 are used in the U-shaped heat exchanger described above, the heat transfer area is large, so that the U-shaped heat exchanger is used as a heat exchanger having a large capacity or a large scale performance in, for instance, atomic power generating facilities or the like. However, in this heat exchanger, the length of each U-shaped tube 109 is different, so that the loss of head due to tube friction resistance in each U-shaped tube 109 varies from tube to tube, and for this reason the flow velocity or flow rate of heat-exchanger medium flowing in each U-shaped tube 109 cannot be kept at a constant level. As a result, thermal stresses generated in each U-shaped tube 109 are not uniform, and distortion or cracking may easily occur in some of the U-shaped tubes. Further, the U-shaped tube 109 has a straight portion and a bending section, so that a distortion difference between the two sections becomes larger, which often causes breakage. Furthermore a supporting force at an end section of the U-shaped tubes 109 where they are fixed to the header fixing plate 108 and that in the bending section are different from each other, so that vibration of the tube may easily occur, giving rise to fatigue and cracking in a contact section of the U-shaped tube and the metal support 110. Other heat exchanger coil assemblies are disclosed in FR-A-247804, US-A-3653796, WO-A-90/10835 and US-A-2378308 (over which claim 1 has been characterised). EP-A-0610897 (which is relevant only for the purposes of novelty) discloses a heat exchanger coil assembly in which the coils are of substantially equal length to equalise the flow resistance of each coil. Thus, the present invention provides a heat-exchanger coil assembly having a first header and a second header provided spaced from said first header in a longitudinal direction of the heat exchanger coil assembly, and a plurality of heat-exchanger coils each provided between said first header and said second header so that the two headers are in communication with each other, wherein the heat-exchanger coils are arranged in a group in which all of the heat exchanger coils are of substantially the same longitudinal depth and each heat-exchanger coil has a different winding diameter so that an inner heat-exchanger coil is surrounded by another heat-exchanger coil having a larger winding diameter, said heat-exchanger coil assembly further comprising an inlet tube for introducing a heat-exchanger medium into said group of heat-exchanger coils via the first header, and an outlet tube for discharging said heat-exchanger medium from said group of heat-exchanger coils via the second header wherein said inlet tube and said outlet tube extend substantially parallel to each other, and wherein said first header and said second header are substantially at right angles to said inlet tube and said outlet tube respectively and are spaced from each other in the axial direction of said inlet and outlet tubes, wherein the number of turns of each heat exchanger coil becomes smaller and smaller from the inside of the heat exchanger coil assembly to the outside, so that each heat-exchanger coil in the group has a substantially equal length, and wherein both of said inlet tube and said outlet tube are located within a spacing smaller than the diameter of the heat-exchanger coil having the minimum winding diameter and at least one of the inlet and outlet tubes extends inside the group of heat exchanger coils. In a further preferred embodiment of the present invention, the winding diameter of each of the heat-exchanger coils is within a range expressed by the following expression: 2D + d ≤ Winding diameter ≤ (2D + d) · n/1.5 herein D indicates a tube diameter of an inlet tube as well as of an outlet tube; d indicates a tube diameter of coil, and n indicates the number of turns of a coil having the minimum winding diameter. In yet another preferred embodiment of the present invention, there is provided a complex comprising a plurality of the heat-exchanger coil assemblies, wherein the groups of heat-exchanger coils of each of heat-exchanger coil assembly are provided so that the groups have a common axial line, and the inlet tube and the outlet tube of each heat-exchanger coil assembly extend inside the heat-exchanger coil group of the next heat-exchanger coil assembly. Some preferred embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings, in which:- Fig. 1 is a plan view illustrating a first preferred embodiment of the present invention; Fig. 2 is a cross-sectional elevation viewed from the front of the embodiment shown in Fig. 1; Figs 3 and 4 illustrate arrangements of inlet and outlet tube which are outside the scope of the present invention; Fig. 5 is a plan view of a second preferred embodiment; Fig. 6 is a partially sectioned front elevation of the embodiment shown in Fig.5; Fig. 7 is a plan view of a third preferred embodiment of the present invention; Fig.8 is a partially sectioned elevation of the preferred embodiment shown in Fig. 7; Fig. 9 is a plan view of a fourth preferred embodiment of the present invention; Fig. 10 is a front view of the preferred embodiment shown in Fig. 9; Fig. 11 is an illustration of a correlation between an inlet tube and an outlet tube and a circular coil; Fig. 12 is an illustration of a correlation between an inlet tube and an outlet tube and an oval coil; Fig. 13 is a cross-sectional elevation along the axis of a heat-exchanger having a preferred heat-exchanger coil assembly in accordance with the present invention; Fig. 14 is a vertical cross-sectional elevation of the same heat-exchanger as shown in Fig. 13; Fig. 15 is a front view of a conventional type of heat-exchanger; Fig. 16 is a cross-sectional elevation along line 16-16 of Fig. 15; Fig. 17 is a plan view of another conventional type of heat-exchanger; and Fig. 18 is a cross sectional elevation of a further conventional type of heat-exchanger. In the heat-exchanger coil assembly of the first preferred embodiment of the present invention illustrated in Figs. 1 and 2, the header 2 in the inlet side is perpendicular to the axis of the inlet tube 4, ie. the component is generally L-shaped. The header 3 in the outlet side is also perpendicular to the axis of the outlet tube 5, ie, is also L-shaped. The inlet tube 4 and the outlet tube 5 are parallel to each other, and the header 2 in the inlet side and the header 3 in the outlet side are spaced from each other in the axial direction of the inlet and outlet tubes 4 and 5. A plurality of outlet holes 6 are provided in the peripheral wall of the header 2 in the inlet side at a specified spacing from each other in the axial direction. In this embodiment, there are four outlet holes 6. The header 3 in the outlet side similarly has the same number of inlet holes 7 as that of the outlet holes 6, these being provided at specified spacings from each other. A group of heat-exchanger coils 8 is provided between the header 2 in the inlet side and the header 3 in the outlet side. The group of heat-exchanger coils 8 comprises a plurality of circular heat-exchanger coils 9 each having a different winding diameter. Each of the smaller diametered heat-exchanger coils 9 is provided so that each of them is surrounded by another heat-exchanger coils 9 having a larger winding diameter. In this embodiment each of the heat-exchanger coils 9 has a common axis and thus the coils are concentric. Also, each of the heat-exchanger coils 9 has a substantially equal length. Consequently, the number of turns of each heat-exchanger coil 9 becomes smaller and smaller from the inside of the heat-exchanger to the outside. The heat-exchanger coil 9 itself is the same type of heat transfer tube as that in the conventional type, and is made with a copper tube, a steel tube or a special steel tube or the like wound in a spiral form. The top/bottom ends of each heat-exchanger coil 9 are connected to an inlet hole 7 of the header 3 in the outlet side and to the outlet hole 6 of the header 2 in the inlet side respectively. More particularly, the inner heat-exchanger coils 9 are connected to outlet holes 6 and inlet holes 7 in the base side of the headers 2 and 3, and the outer heat-exchanger coils 9 are connected to outlet holes 6 and inlet holes 7 in the top side of the headers 2 and 3. As described above, the header 2 in the inlet side and the header 3 in the outlet side are communicated to each other through the heat-exchanger coils 9. In the embodiment, both of the inlet tube 4 and the outlet tube 5 are located within a spacing smaller than the diameter of the heat-exchanger coil 9 having the minimum winding diameter. Consequently the inlet tube 4 extends inside the group of heat-exchanger coils 8. The heat-exchanger coil assembly 1 is provided in the body section of a heat-exchanger, not shown in Figs. 1 and 2. The first heat-exchanger medium such as a gas or a liquid is introduced into the body section of the assembly as a downflow through the inlet tube 4. The heat-exchanger medium flows into each of the heat-exchanger coils 9 via the outlet holes 6 of the header 2 in the inlet side, and ascends inside these heat-exchanger coils 9 in a spiral form. The first heat-exchanger medium exchanges heat with a second heat-exchanger medium in the body section, through the tube wall, while flowing through these heat-exchanger coils 9. The first heat-exchanger medium further flows into the header 3 in the outlet side via an inlet hole 7, is discharged to outside of the body section through the outlet tube 5, and is sent to the load. According to these heat-exchanger coil assemblies 1, the heat-exchanger capability is enhanced by means of using a plurality of heat-exchanger coils 9. Because each of the heat-exchanger coils 9 is provided so that the coils 9 are surrounded by another heat-exchanger coil 9 having a larger winding diameter, the space for installation thereof occupying in the body section of the heat-exchanger coil assembly 1 is saved. In other words, the heat transfer area can be made larger without increasing the body capacity. Also, each of the heat-exchanger coils 9 is not in a state of serial multiplex winding, but is wound independently, so that the loss of head pressure due to friction resistance of the tube will not become larger. Also, by increasing or decreasing the number of heat-exchanger coils 9 according to the necessity, the heat-exchanger capability can be freely set, and the heat-exchanger coil assembly can be applied to heat-exchangers in a range from small-scale to large-scale. Also, as each of the heat-exchanger coils 9 has a substantially equal length, the loss of head pressure in each heat-exchanger coil 9 becomes substantially constant. Consequently, the flow rate of the heat-exchanger medium flowing in each of the heat-exchanger coils 9 becomes uniform, and distortion or cracking due to nonuniform thermal stresses generated in parts of the heat-exchanger do not occur. For this reason, heat transfer tubes of the same shape are preferably used, which makes processing control easier. Also, the time for coil repairing and that for coil exchanging are substantially the same, so that coil maintenance is easier. In Figs. 3 and 4, the group of heat-exchanger coils 8 is indicated with a chain line for simplification. Figs. 3 and 4 do not illustrate embodiments of the present invention. Firstly, there is shown in Fig. 3 an example where the inlet tube 4 is provided outside the group of heat-exchanger coils 8 (outside of the heat-exchanger coil 9 having the maximum winding diameter), while the outlet tube 5 is provided inside the group of heat-exchanger coils 8 (inside the heat-exchanger coil 9 having the minimum winding diameter). Shown in Fig. 4 is an example where the inlet tube 4 is provided inside the group of heat-exchanger coils 8, while the outlet tube 5 is provided outside the group of heat-exchanger coils 8. It is clear that the modes shown in Figs. 1 and 2 are the most compact of these and can save space in an installation. In the second embodiment of the present invention shown in Figs. 5 and 6, the load is based on two systems and according to this system the heat-exchanger coil assembly becomes a complex comprising two regions of heat-exchanger coil. The two heat-exchanger coil assemblies 1a and 1b each have the same configuration as that of the heat-exchanger coil assembly 1 shown in Figs. 1 and 2, and the same character a or b is added to the reference numerals of the same heat-exchanger coil assembly. The two heat-exchanger coil assemblies 1a and 1b are provided as separate units in multiple stages so that these groups of heat-exchanger coils 8a and 8b have a common axial line. The common axial line is an axial line extending in the vertical direction in this embodiment. Also the inlet tube 4a and the outlet tube 5a of the heat-exchanger coil assembly 1a provided in the lower side extend inside the group of heat-exchanger coils 8b of the heat-exchanger coil assembly 1b provided in the upper side. In the case where two sections of heat-exchanger coil assembly are used, and in the case of three sections or more also, the inlet tube and outlet tube of the heat-exchanger coil assembly in the lower side are provided so that they extend inside the group of heat-exchanger coils of all the heat-exchanger coil assemblies in the upper side. In Figs. 7 and 8, a third embodiment of the present invention is shown. Circular heat-exchanger coils are used in each embodiment described above. The heat exchanger coil assembly 11 in this embodiment is one in which heat-exchanger coils 19 having an oval shape or a track shape are used. As far as other points except the shape of the heat-exchanger coil are concerned, the configuration herein is the same as that in the embodiment using the circular coils described above, and the same reference numerals are assigned to the same members. A fourth embodiment of the present invention shown in Figs. 9 and 10 comprises a complex using a plurality of the heat-exchanger coil assemblies like that shown in the embodiment of Figs. 5 and 6, and these groups of heat-exchanger coils 8a, 8b, and 8c are provided as separate units in multiple stages with a common axial line. However, in the embodiment of Figs. 7 and 8, three heat-exchanger coil assemblies 11a, 11b, and 11c are used in order to correspond to three types of load, and the point that the heat-exchanger coil 19 in an oval or track shape is used herein is different from that in the embodiment of Figs. 5 and 6. The three heat-exchanger coil assemblies 11a, 11b, and 11c have the same configuration as that of the heat-exchanger coil assembly 11 shown in Figs. 7 and 8, and the same character a, b, or c is added to the reference numerals of the same heat-exchanger coil assembly. A correlation between the inlet tube as well as the outlet tube and the circular coil is shown in Fig. 11, and when a circular coil is used as described above, the minimum winding diameter, m, of the coil is expressed by the following expression, and herein D indicates a diameter of the inlet tube 4 and the outlet tube 5, d indicates a diameter of the coil: m = 2D + d Also, given the number of turns, n, the length, L, of the coil having the minimum winding diameter is expressed by the following expression: L = Π·m·n = Π · (2D+d)· n On the other hand, the length of the coil having the maximum winding diameter is equal to L and the number of tums thereof is 1.5 (a turn and a half), so that given the maximum winding diameter of the coil, M, the relation above is satisfied with the following expression: L = 1.5 Π M With the expressions (1) and (2), the maximum winding diameter of the coil is expressed by the following expression: M = (2D + d) · n/1.5 The correlation between the inlet tube as well as the outlet tube and the coil in an oval shape is shown in Fig. 12, and when the coil in an oval shape or the coil in a track shape is used as described above, the minimum diameter of the coil, m, is expressed by the following expression: m = D + d Also, given a number of turns, n, the length, L, of the coil having the minimum winding diameter in consideration of the length D of the straight line is expressed by the following expression: L = (Π · m + 2D) · n = {Π · (D + d) + 2D} · n On the other hand, similarly in the case of the circular coil, the length of the coil having the maximum winding diameter is equal to L, and the number of turns thereof is 1.5, so that given the maximum winding diameter of the coil of M, the relation above is satisfied with the following expression: L = 1.5 (Π · M · 2D) With the expressions (3) and (4), the maximum winding diameter, M, of the coil is expressed by the following expression: M = (D + d)·n/1.5 + (2n - 3) · D/1.5 Π In the hot water generator which is the heat-exchanger applying the preferred heat-exchanger coil assembly of the present invention shown in Figs. 13 and 14, the flue 21 is provided in the bottom of the body section 20, and the furnace room 22 is formed inside the flue. The combustion equipment 23 is opened in the furnace room 22, and operation of the combustion equipment 23 is controlled by the thermostat 24 so that water 25 stored in the body section 20 is kept at the specified temperature. Flame generated in the combustion equipment 23 becomes high temperature gas in the furnace room 22, and the gas is discharged to the outside via the exhaust pipe 26. In this time, the high temperature gas heats the storage water 25 via the tube wall of the convection tube 27 and the wall of the flue 21. The body section 20 is in communication with the distilled water tank 30 via the communicating tube 29. The ball tap is provided in the distilled water tank 30, and supply water is supplied from the distilled water tube 32 so that the level of the stored water can be kept constant. The air chamber 33 is formed above the level in the body section 20, and the air chamber 33 is open to the air via the communicating tube 34, the distilled water tank 30 and the air open tube 35. With this feature, the storage water 25 is heated under ambient pressure, so that its temperature can be made not to exceed the boiling point (100°C) under normal air pressure. Provided in the body section 20 are two preferred heat-exchanger coil assemblies 1 and 11 according to the present invention. One of the heat-exchanger coil assemblies 1 comprises circular coils, while the other of the heat-exchanger coil assembly 11 comprises coils in an oval shape or track shape. The two heat-exchanger coil assemblies 1 and 11 each are connected to different load systems respectively. The load systems herein are, for instance, heating circulation systems for example heating, hot-water supply, a bath room, and a swimming pool. The first heat-exchanger medium (normally, a liquid such as water) of the load system is introduced into the body section 20 via the inlet tube 4 of the heat-exchanger coil assemblies 1 and 11. While flowing in each of the heat-exchanger coil in the groups of heat-exchanger coils 8, the first heat-exchanger medium exchanges heat with storage water 25 which is the second heat-exchanger medium, is heated thereby, and is sent to the load system via the outlet tube 5. Although description has been made for preferred embodiments of the present invention as described above, the present invention is not limited to those embodiments and it is needless to say that various modifications described below are possible as long as the modifications do not depart from the essence of the present invention. (1) The flow of the heat-exchanger medium in the heat-exchanger coil assembly 1 can be reverse to the embodiments described above. Namely, the outlet tube 5 and the header 3 in the outlet side, each can be made as an inlet tube and a header in the inlet side respectively, and the inlet tube 4 and the header 2 in the inlet side can be made as an outlet tube and a header in the outlet side respectively. (2) The winding shape of the heat-exchanger coils is not limited to a circle or an oval shape, but various types of shapes such as a polygons or the like can be applied. (3) The heat-exchanger coil assembly of the present invention is not limited to the system based on heat-exchanging of liquid to liquid, but can be utilized to such heat-exchanging as gas to gas, or gas to liquid. Also, the heat-exchanger medium flowing in the coils may be any heat-receiving medium and heating medium. (4) In Figs. 13 and 14, shown is an example of a heat-exchanger coil assembly in accordance with the present invention being applied as a heat-exchanger in a vertical type, but it can be used as a heat-exchanger in a horizontal type. Thus, at least in certain preferred embodiments, there is provided a heat-exchanger coil assembly which can enhance the heat-exchanging capability without requiring a larger capacity of the body section, and can be applied to a heat-exchanger having a large-scale performance; furthermore, there is provided a heat-exchanger coil assembly in which the heat-exchanging capability can freely be in a range of preset capacity of the body section; furthermore, there is provided a heat-exchanger coil assembly in which a plurality of heat-exchanger coils are used, but the flow rate of heat-exchanger medium flowing in these coils is kept at a constant level.

Claims: A heat-exchanger coil assembly having a first header (2) and a second header (3) provided spaced from said first header in a longitudinal direction of the heat exchanger coil assembly, and a plurality of heat-exchanger coils (9) each provided between said first header and said second header so that the two headers are in communication with each other, wherein the heat-exchanger coils are arranged in a group (8) in which all of the heat exchanger coils are of substantially the same longitudinal depth and each heat-exchanger coil has a different winding diameter so that an inner heat-exchanger coil is surrounded by another heat-exchanger coil having a larger winding diameter, said heat-exchanger coil assembly further comprising an inlet tube (4) for introducing a heat-exchanger medium into said group of heat-exchanger coils via the first header (2), and an outlet tube (5) for discharging said heat-exchanger medium from said group of heat-exchanger coils via the second header (3) wherein said inlet tube (4) and said outlet tube (5) extend substantially parallel to each other, and wherein said first header (2) and said second header (3) are substantially at right angles to said inlet tube and said outlet tube respectively and are spaced from each other in the axial direction of said inlet and outlet tubes, wherein the number of turns of each heat exchanger coil becomes smaller and smaller from the inside of the heat exchanger coil assembly to the outside, so that each heat-exchanger coil (9) in the group has a substantially equal length, and wherein both of said inlet tube (4) and said outlet tube (5) are located within a spacing smaller than the diameter of the heat-exchanger coil (9) having the minimum winding diameter and at least one of the inlet and outlet tubes extends inside the group of heat exchanger coils. A heat-exchanger coil assembly as claimed in claim 1, wherein the winding diameter of each of said heat-exchanger coils (9) is within a range expressed by the following expression: 2D + d ≤ Winding diameter ≤ (2D + d) · n/1.5 where D indicates the tube diameter of the inlet tube as well as of the outlet tube; d indicates a tube diameter of a heat-exchanger coil, and n indicates the number of turns of the heat-exchanger coil having the minimum winding diameter. A heat-exchanger coil assembly as claimed in any preceding claim, wherein the heat-exchanger coils (9) are substantially circular. A heat-exchanger coil assembly as claimed in any of claims 1 or 2, wherein the heat-exchanger coils (9) are substantially oval. A complex comprising a plurality of heat-exchanger coil assemblies (1a, 1b) as claimed in any preceding claim. A complex as claimed in claim 5, wherein the groups of heat-exchanger coils (8a, 8b) of the respective assemblies are arranged coaxially, and wherein said inlet tube (4a, 4b) and said outlet tube (5a, 5b) of at least one of the heat-exchanger coil assemblies (1a, 1b) extends within the heat-exchanger coils (9) of the adjacent heat-exchanger coil assembly.

Inventors: MARUYAMA NOBORU, MARUYAMA, NOBORU
Applicants: MARUYAMA NOBORU, MARUYAMA, NOBORU
Application year: 1995
Main classification: F28D7
IPC codes: F28D7, F24H1, F28D1