HEAT EXCHANGER

Abstract

A method for making a heat exchanger includes providing a first outer tube, and an inner tube disposed in the first outer tube; placing a first coiled heat-transfer tube in a space defined between the inner tube and the first outer tube without being fixed to either one of an outer peripheral surface of the inner tube and an inner peripheral surface of the first outer tube, the first coiled heat-transfer tube including a plurality of coiled sections, an inside space of the heat-transfer tube defining a first flow path, a coiled space defined between coiled sections of the heat-transfer tube in the space, defined between the inner tube and the first outer tube, defining a second flow path, wherein heat is exchanged between two fluids.

Claims

1. A method for making a heat exchanger comprising the steps of: providing a first outer tube, and an inner tube disposed in the first outer tube; placing a first coiled heat-transfer tube in a space defined between the inner tube and the first outer tube without being fixed to either one of an outer peripheral surface of the inner tube and an inner peripheral surface of the first outer tube, the first coiled heat-transfer tube including a plurality of coiled sections, an inside space of the heat-transfer tube defining a first flow path for a first fluid, a coiled space defined between coiled sections of the heat-transfer tube in the space, defined between the inner tube and the first outer tube, defining a second flow path for a second fluid, wherein heat is exchanged between the first and second fluids; exerting an expansion force on the first coiled heat-transfer tube to increase a diameter of the coiled sections of the first coiled heat-transfer tube so as to be larger than the diameter the coiled sections of the first coiled heat-transfer tube naturally have, or a contraction force on the first coiled heat-transfer tube to decrease the diameter of the coiled sections of the first coiled heat-transfer tube so as to be smaller than the diameter the coiled sections of the first coiled heat-transfer tube naturally have; connecting a first tensioning joint to the first coiled heat-transfer tube, and maintaining a state in which the expansion force or the contraction force is applied to the first coiled heat-transfer tube by the first tensioning joint, such that the first coiled heat-transfer tube is subjected to the expansion force, abutting against, with a pressure, the inner peripheral surface of the first outer tube without contacting the outer peripheral surface of the inner tube, or subjected to the contraction force, abutting against, with a pressure, the outer peripheral surface of the inner tube without contacting the inner peripheral surface of the first outer tube, by an action of the first tensioning joint even when the first coiled heat-transfer tube is not fixed either to the inner peripheral surface of the first outer tube or the outer peripheral surface of the inner tube, wherein the heat exchange is performed between the first and second fluids in the state in which the expansion force or the contraction force is applied to the first coiled heat-transfer tube by the first tensioning joint.

2. The method according to claim 1, wherein the step of exerting comprises exerting the contraction force on the first coiled heat-transfer tube by fixating a first end of the first coiled heat-transfer tube and pulling a second end of the first coiled heat-transfer tube in a direction away from the first end of the first coiled heat-transfer tube before the second end of the first coiled heat-transfer tube is fixated by the first tensioning joint, or exerting the expansion force on the first coiled heat-transfer tube by fixating the first end of the first coiled heat-transfer tube and pushing the second end of the first coiled heat-transfer tube in a direction toward the first end of the first coiled heat-transfer tube before the second end of the first coiled heat-transfer tube is fixated by the first tensioning joint.

3. The method according to claim 1, wherein the first coiled heat-transfer tube is configured in such a manner that when a load equal to or less than 10 kg is applied in a coil longitudinal axis direction of the coiled heat-transfer tube, a length of the first coiled heat-transfer tube in the longitudinal coil axis direction is varied by 10% in comparison with the length of the first coiled heat-transfer tube when no load being applied therein.

4. The method according to claim 1, wherein the first coiled heat-transfer tube is made of at least a material selected from the group consisting of metals; acrylic resins; fluorine based resins; and an epoxy resin.

5. The method according to claim 4, wherein said metals are stainless steel, metal alloy, titanium, copper, or nickel; said acrylic resins are ABS, polyethylene, polypropylene or PMMA; and said fluorine based resins are polycarbonate, PTFE or PFA.

6. The method according to claim 1, wherein an outer diameter of the first coiled heat-transfer tube itself is equal to or less than 28 mm.

7. The method according to claim 1, wherein the heat exchanger further comprises an upper closing part and a lower closing part, the upper closing part closing the inner tube and the first outer tube at an upper side, the lower closing part closing the inner tube and the first outer tube at a lower side.

8. The method according to claim 7, further comprising the steps of: fixing the first coiled heat-transfer tube to the upper closing part at an upper fixing point via an upper part of the first tensioning joint; and fixing the first coiled heat-transfer tube to the lower closing part at a lower fixing point via a lower part of the first tensioning joint, wherein the first coiled heat-transfer tube is fixed to the upper and lower closing parts in a manner such that the coiled sections of the first coiled heat-transfer tube between the upper fixing point and the lower fixing point have the diameter larger than or smaller than the diameter the coiled sections of the first coiled heat-transfer tube naturally have.

9. The method according to claim 1, further comprising the steps of: providing a second outer tube outside of the first outer tube; placing a second coiled heat-transfer tube in a space defined between the first outer tube and the second outer tube without being fixed to either one of the outer peripheral surface of the first outer tube and an inner peripheral surface of the second outer tube, the second coiled heat-transfer tube including a plurality of coiled sections, and defining a third flow path for a third fluid, wherein heat is exchanged between the second and third fluids; exerting an expansion force on the second coiled heat-transfer tube to increase a diameter of the coiled sections of the second coiled heat-transfer tube so as to be larger than the diameter the coiled sections of the second coiled heat-transfer tube naturally have, or a contraction force on the second coiled heat-transfer tube to decrease the diameter of the coiled sections of the second coiled heat-transfer tube so as to be smaller than the diameter the coiled sections of the second coiled heat-transfer tube naturally have; and connecting a second tensioning joint to the second coiled heat-transfer tube, and maintaining a state in which the expansion force or the contraction force is applied to the second coiled heat-transfer tube by the second tensioning joint, such that the second coiled heat-transfer tube is subjected to the expansion force, abutting against, with a pressure, the inner peripheral surface of the second outer tube without contacting the outer peripheral surface of the first outer tube, or subjected to the contraction force, abutting against, with a pressure, the outer peripheral surface of the first outer tube without contacting the inner peripheral surface of the second outer tube, by an action of the second tensioning joint even when the second coiled heat-transfer tube is not fixed either to the inner peripheral surface of the second outer tube or the outer peripheral surface of the first outer tube, wherein coiled diameters of the first coiled heat-transfer tubes and the second coiled heat-transfer tube are concentric, and wherein the heat exchange is performed between the second and third fluids in the state in which the expansion force or the contraction force is applied to the first coiled heat-transfer tube by the first tensioning joint, and in the state in which the expansion force or the contraction force is applied to the second coiled heat-transfer tube by the second tensioning joint.

10. The method according to claim 9, wherein the step of exerting comprises exerting the contraction force on the second coiled heat-transfer tube by fixating a first end of the second coiled heat-transfer tube and pulling a second end of the second coiled heat-transfer tube in a direction away from the first end of the second coiled heat-transfer tube before the second end of the second coiled heat-transfer tube is fixated by the second tensioning joint, or exerting the expansion force on the second coiled heat-transfer tube by fixating the first end of the second coiled heat-transfer tube and pushing the second end of the second coiled heat-transfer tube in a direction toward the first end of the second coiled heat-transfer tube before the second end of the second coiled heat-transfer tube is fixated by the second tensioning joint.

11. The method according to claim 9, wherein the heat exchanger further comprises an upper closing part and a lower closing part, the upper closing part closing the inner tube and the second outer tube at an upper side, the lower closing part closing the inner tube and the second outer tube at a lower side.

12. The method according to claim 11, further comprising the steps of: fixing the first and second coiled heat-transfer tubes to the upper closing part at different upper fixing points via the upper part of the first tensioning joint and an upper part of the second tensioning joint, respectively; and fixing the first and second coiled heat-transfer tubes to the lower closing part at different lower fixing points via the lower part of the first tensioning joint and a lower part of the second tensioning join, respectively, wherein the first coiled heat-transfer tube is fixed to the upper and lower closing parts in a manner such that the coiled sections of the first coiled heat-transfer tube between the upper fixing points and the lower fixing points have the diameter larger than or smaller than the diameter the coiled sections of the first coiled heat-transfer tube naturally have, and the second coiled heat-transfer tube is fixed to the upper and lower closing parts in a manner such that the coiled sections of the second coiled heat-transfer tube between the upper fixing points and the lower fixing points have the diameter larger than or smaller than the diameter the coiled sections of the second coiled heat-transfer tube naturally have, and wherein the diameter of the coiled sections of the first coiled heat-transfer tube between the upper fixing points and lower fixing points is smaller than the diameter of the coiled sections of the second coiled heat-transfer tube between the upper fixing points and lower fixing points.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1(A) illustrates a configuration of a heat exchanger according to one embodiment of the present invention and FIG. 1(B) is a plan view thereof.

[0019] FIG. 2(A) illustrates a configuration of a heat exchanger according to another embodiment of the present invention and FIG. 2(B) is a plan view thereof.

[0020] FIG. 3(A) illustrates a configuration of a heat exchanger according to still another embodiment of the present invention and FIG. 3(B) is a plan view thereof.

[0021] FIG. 4(A) is an enlarged view of a substantial portion of the heat exchanger according to the embodiment of the present invention in assembling and FIG. 4(B) is an enlarged view of a substantial portion of the heat exchanger when the assembling processing is completed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] One embodiment of the present invention is described below with reference to the accompanying drawings. The terms up, down, left and right as used herein only refers to relative positional relationships but do not specify absolute positions.

[0023] As illustrated in FIG. 1, a heat exchanger of this embodiment includes an inner tube 5 and an outer tube 6 which have a substantially circular lateral cross section, wherein upper ends and lower ends of the inner tube 5 and the outer tube 6 are closed by an upper closing part 9 and a lower closing part 8, respectively. In this example, the inner tube 5 and the lower closing part 8 are integrally formed. According to another embodiment, not the lower closing part 8 but the upper closing part 9 may be integrally formed with the inner tube 5. Alternatively, none of the lower closing part 8 or the upper closing part 9 is integrally formed with the inner tube 5 but may be formed detachably.

[0024] A coiled heat-transfer tube 1 is placed in the space 7 defined between the inner tube 5 and the outer tube 6 such that the coiled heat-transfer tube 1 closely contacts with or pressure contacts against at least either one of an outer perimeter of the inner tube 5 or an inner perimeter of the outer tube 6. The coiled heat-transfer tube 1 pierces through the upper closing part 9 and the lower closing part 8, thereby being contactable with pipes outside the heat exchanger. However, the heat-transfer tube 1 is not fixed to either one of the outer peripheral surface of the inner tube 5 or the inner peripheral surface of the outer tube 6. A coiled space 4 is defined between turns of the coiled heat-transfer tube 1. The coiled space 4 having predetermined intervals is enclosed by the vertically adjacent different turns of the heat-transfer tube 1 and the inner and outer tubes 5, 6. The illustrated coiled heat-transfer tube 1, inner tube 5 and outer tube 6 are implemented in a cylindrical shape having a vertically uniform diameter. However, they may be formed into a shape having a vertically varying diameter (i.e., a circular truncated cone shape or an inverted circular truncated cone shape).

[0025] A fluid 2 to be processed, e.g., water, an organic solvent, a solution obtained by dissolving a solute, or a microparticle dispersion liquid, passes through an inside of the heat-transfer tube 1. A preferable material for the heat-transfer tube 1 can expand and contract and has a high corrosion and pressure resistance, and robustness against the target fluid to be processed through the heat-transfer tube. Examples of the material for the heat-transfer tube include a metal such as stainless steel, hastelloy, inconel, titanium, copper, and nickel; an acrylic resin such as ABS, polyethylene, polypropylene, and PMMA; a fluorine based resin such as polycarbonate, PTFE, and PFA; and an epoxy resin.

[0026] The external section of the heat-transfer tube 1 as the coiled space 4 (in other words, the coiled space 4 defined between the heat-transfer tube 1 and the heat-transfer tube 1) is a space for passing a heating medium 3. The heating medium 3 enters and exists through nozzles 10 formed in the upper closing part 9 and the lower closing part 8, respectively. Accordingly, the heating medium 3 can be passed through the space 7 and the coiled space 4. To efficiently and effectively exchange heat of the fluid 2 to be processed, the fluid 2 to be processed is passed upwardly (i.e., in a U direction) in FIG. 1 and the heating medium 3 is passed downwardly (i.e., in an S direction) to create an absolute counterflow. Accordingly, both of the fluid 2 to be processed and the heating medium 3 are prevented from an increase of a pressure loss, resulting in securing a large overall heat-transfer coefficient. However, a flow of both fluids in the same direction should not be excluded from consideration.

[0027] Assembly and disassembly of the heat exchanger according to the present invention are described below. Initially, the heat-transfer tube 1 is assembled with the lower closing part 8 and the inner tube 5 which are integrally formed. The above attachment can be performed smoothly by defining a suitable clearance 4c between the inner tube 5 and the heat-transfer tube 1 (See FIG. 4(A)). After the attachment, the heat-transfer tube 1 is fixed to the lower closing part 8. The fixation is performed with what having a tensioning mechanism 11. The tensioning mechanism 11 keeps the expansion or contraction force for expanding or contracting the diameter of the coiled heat-transfer tube 1 than the diameter the coiled heat-transfer tube 1 naturally has. In the illustrated example, an interlocking joint 11 is employed as the tensioning mechanism 11. In another embodiment, the tensioning mechanism may include a clamp, a saddle band, a strap, and a bracket. In addition, the tensioning mechanism may be a fixation by, for example, welding or bonding (not illustrated). The tensioning mechanism 11 may be configured only to keep the expansion or contraction force, whereas, generation of the expansion or contraction force may be performed by another mechanism. However, in a case of the interlocking joint 11, it generates as well as keeps the expansion or contraction force.

[0028] Then, the heat-transfer tube 1 is pulled in the U direction to reduce the diameter of the coiled heat-transfer tube 1, thereby bringing the heat-transfer tube 1 into close contact with or pressure contact against the inner tube 5 (FIG. 4(B)). Thereafter, the outer tube 6 slightly spaced by a gap 4d from the outer diameter of the assembled coiled heat-transfer tube 1, and the upper closing part 9 are assembled therewith. The outer tube 6 and the upper closing part 9 may be integrally formed or may be formed so as to be disassembled.

[0029] More specifically, the slight gap 4d is kept while the heat-transfer tube 1 is pulled in the U direction. The outer tube 6 is then mounted to the outside of the heat-transfer tube 1 and the upper closing part 9 is temporally attached thereto. During the temporal attachment, while the heat-transfer tube 1 is still pulled in the U direction, an upper end of the heat-transfer tube 1 is fixed to the upper closing part 9, thereby completing the attachment between the outer tube 6 and the upper closing part 9. The tensioning mechanism 11 of the upper closing part 9 may be configured to be adjustable of an upper end position of the outer tube 6 in the same manner as the interlocking joint 11 of the lower closing part 8 or may be an unadjustable fixing mechanism.

[0030] At the time, for enabling an easy assembling and disassembling, when the coiled heat-transfer tube 1 that can be expanded or contracted is varied by 10% of the expansion or contraction amount with respect to a length the coiled heat-transfer tube 1 naturally has, the load is preferably equal to or less than 10 kg. Also, for the purpose of the low flow processing, for example, in various chemical experiments, the outer diameter of the heat-transfer tube 1 is preferably equal to or less than 28 mm. Thereby, the coiled heat-transfer tube 1 having a smaller coil diameter can be produced and thus the heat exchanger of a smaller size can be provided.

[0031] The above example is suitable for the heat-transfer tube 1 naturally having an inner diameter larger than the outer diameter of the inner tube 5. However, in a case where the inner diameter the heat-transfer tube 1 naturally has is larger than the outer diameter of the inner tube 5 and the outer diameter the heat-transfer tube 1 naturally has is larger than the inner diameter of the outer tube 6, the following method is employable. During the above described temporal attachment, the tensile force in the U direction is released. Accordingly, the coiled heat-transfer tube 1 attempts to resume its natural size. As a result, the coiled heat-transfer tube 1 is brought into close contact with or pressure contact against the inner peripheral surface of the mounted outer tube 6. In that state where the heat-transfer tube close contacts with or pressure contacts against the outer tube 6, the upper end of the heat-transfer tube 1 is fixed to the upper closing part 9 to complete the attachment between the outer tube 6 and the upper closing part 9.

[0032] Alternatively, in a case where the inner diameter of the heat-transfer tube 1 it naturally has is larger than the outer diameter of the inner tube 5 and the outer diameter of the heat-transfer tube 1 it naturally has is smaller than the inner diameter of the outer tube 6, the following method is also employable. In other words, the heat-transfer tube 1 is attached with a suitable clearance 4c between the inner tube 5 and the heat-transfer tube 1, and the outer tube 6 having a slight gap with the outer coil diameter of the heat-transfer tube 1 is assembled with the upper closing part 9. In this state, the heat-transfer tube 1 is pulled in the vertical direction so that the upper end and the lower end thereof separate from each other by, for example, operating the interlocking joint 11 to generate the expansion or contraction force (i.e., a contraction force in this case). Thereby, the diameter of the coiled heat-transfer tube 1 is reduced to bring the heat-transfer tube 1 into close contact with or pressure contact against the inner tube 5. The expansion or contraction force is then kept to secure the close contact or pressure contact state.

[0033] In the above embodiment, the heat-transfer tube 1 is brought into close contact with or pressure contact against the inner tube 5. However, in another embodiment, the heat-transfer tube 1 is pushed downwardly into the outer tube 6 from above, i.e., in the S direction (in other words, the upper end is brought closer to the lower end) to increase the coiled diameter, thereby bringing the heat-transfer tube 1 into close contact with or pressure contact against the outer tube 6. Further, in the above example, the upper end and the lower end of the heat-transfer tube 1 is pushed or pulled in the coil axial direction. However, the upper end and the lower end of the heat-transfer tube 1 may be pushed or pulled in a direction in which a helical structure of the coil extends. The pushing or pulling direction can be changed, as required, provided that the expansion or contraction force can be generated. In the above description, the vertical orientation is exemplified, but the orientation may be inverted. More specifically, up and down can be interpreted as one side and the other side, respectively.

[0034] According to the above invention, the heat-transfer tube 1 can be placed in the space 7 defined between the inner tube 5 and the outer tube 6 so as to be on a concentric circle of the inner and the outer tubes. Therefore, the coiled space 4 sandwiched between the adjacent coiled sections of the heat-transfer tube 1 in the space 7 can be used as a flow path of the heating medium 3. The heat exchanger according to the present invention can be disassembled with ease according to a reversed procedure of the above assembling method.

[0035] In the case where the coiled heat-transfer tube 1 is not fixed in the space 7, the heat-transfer tube 1 may expand or contract due to the flow resistance of the heating medium 3, which may invite a case that the pitches between the coiled sections of the heat-transfer tube 1 become tight. In other words, the flow resistance of the heating medium 3 causes the coiled sections of the heat-transfer tube 1 become closer to each other and finally the coiled heat-transfer tube 1 may move to a direction the coiled space 4 is eliminated. In this case, since the heating medium 3 becomes not to pass smoothly in the coiled space 4, there arises a problem that the heat exchange cannot work at all, that the effective/efficient heat exchange cannot be performed, or that breakage or short-life of the heat-transfer tube 1 may be induced. In the present invention, although the heat-transfer tube 1 is not fixed, the heat-transfer tube 1 close contacts with or pressure contacts against at least either one of the outer perimeter of the inner tube 5 or the inner perimeter of the outer tube 6. Therefore, the coiled heat-transfer tube 1 can be prevented from the displacement caused due to the flow resistance that is generated by the flow of the heating medium 3. As a result, the above described problems can be solved.

[0036] The heat-transfer tube 1 may include a plurality of heat-transfer tubes. The number of the heat-transfer tubes 1 to be assembled together is not particularly limited. The number is determined according to a necessary flow rate of the fluid to be processed or the number of types of fluids to be treated. Examples of assembling the plurality of heat-transfer tubes are illustrated with reference to FIGS. 2(A) and 2(B), and FIGS. 3(A) and 3(B). For example, as illustrated in FIG. 2, in a case of assembling the heat-transfer tubes 1 having the same coiled diameter, the heat-transfer tube 1a and the heat-transfer tube 1b are assembled with the lower closing part 8 (or the upper closing part 9) and the inner tube 5, which are integrally formed, and are fixed at different positions on the lower closing part 8. Then, the heat-transfer tube 1a and the heat-transfer tube 1b are brought into close contact with or pressure contact against the inner tube 5 by the above described mechanism, followed by being further assembled with the outer tube 6 and the upper closing part 9 (or the lower closing part 8). Accordingly, the plurality of heat-transfer tubes 1 can be assembled. In another embodiment, as illustrated in FIG. 3, the coiled heat-transfer tubes 1 may be implemented in a manner that the diameters of the coiled heat-transfer tubes are located on concentric circles. In this case, the heat-transfer tube 1a is assembled with the lower closing part 8 (or the upper closing part 9) and the inner tube 5 which are integrally formed. The heat-transfer tube 1a is then brought into close contact with or pressure contact against the inner tube 5 by the above described mechanism. Then, the outer tube 6a spaced from the outer diameter of the coiled heat-transfer tube 1a by the slight gap is assembled therewith. Subsequently, the heat-transfer tube 1b is assembled with the lower closing part 8 (or the upper closing part 9) to bring the heat-transfer tube 1b into close contact with or pressure contact against the outer peripheral surface of the outer tube 6a by the above described mechanism. Then, the outer tube 6b and the upper closing part 9 (or the lower closing part 8) are assembled therewith. Accordingly, the plurality of heat-transfer tubes 1 can be assembled. In the embodiment illustrated in FIG. 3, the coiled spaces 4a and 4b are defined. Even in a case where more than three heat-transfer tubes are assembled together, this configuration can be implemented using a material and an assembling method similar to those described above. In this case, the assembly can be performed by a combination of the assembly based on the same diameter and the assembly based on the concentric circles.

[0037] As described above, passed through the heat-transfer tube 1 is the fluid 2 to be processed such as water, organic solvent, solution that is produced by dissolving solute, and microparticle dispersion liquid to be used in the low flow processing, more specifically, used in various chemical experiments. Therefore, the heat-transfer tube 1 often needs to be replaced depending on experiment descriptions. Furthermore, in a case where solid and powder contained in the fluid 2 to be processed, or solute dissolved in the fluid 2 to be processed is precipitated due to a change of temperature or concentration or due to drying, such solid matters may adhere or clog inside the heat-transfer tube 1 to invite a necessity of replacement of the heat-transfer tube 1.

[0038] In a submerged heat exchanger or double-pipe heat exchanger which is used in the typical low flow processing, especially, in various chemical experiments, a good efficiency in heat exchange cannot be expected. Therefore, the structure of the heat exchanger according to the present invention solves the above problems of the submerged heat exchanger and the double-pipe heat exchanger. Further, as described above, in a case when the heat-transfer tube 1 is required to be replaced, the heat exchanger according to the present invention is characterized in that it can be assembled or disassembled very easily because the heat exchanger according to the present invention has a very simple structure in comparison with the multipipe heat exchanger and the plate type heat exchanger. Also, in addition to the easy replacement of the heat-transfer tube, the heat exchanger can be easily disassembled and cleaned, so that it is not necessary to dispose the heat exchanger itself or perform a costly cleaning of the heat exchanger as it is done in the conventional heat exchanger.

[0039] There are a plurality of modes for achieving the close contact with or the pressure contact against the inner tube 5 and the outer tube 6 by using the elastic deformation of the heat-transfer tube. Such modes are described below.

First Mode

[0040] It is provided that the outer diameter of the inner tube 5 is , the inner diameter of the outer tube 6 is , the inner diameter of the coiled heat-transfer tube 1 is , and the outer diameter of the coiled heat-transfer tube 1 is . If the inner diameter of the coiled heat-transfer tube 1 is larger than or equal to the outer diameter of the inner tube 5 ( ), when the inner tube 5 is inserted into the heat-transfer tube 1 leaving it in the natural state and, the heat-transfer tube 1 is pulled in a direction in which both ends separates from each other after the insertion, the outer diameter of the inner tube 5 comes to be equal to the inner diameter of the heat-transfer tube 1 by the external force to bring the heat-transfer tube 1 into close contact with or pressure contact against the inner tube 5. Here, even in a case of , the inner diameter may be increased by compressing the heat-transfer tube 1 in order to facilitate the insertion.

Second Mode

[0041] If the inner diameter of the coiled heat-transfer tube 1 is smaller than the outer diameter of the inner tube 5 (>), the inner tube 5 is inserted while the heat-transfer tube 1 is compressed to expand the inner diameter . After the insertion, when the compressing force is released and the heat-transfer tube 1 is then pulled, as required, the outer diameter of the inner tube 5 becomes equal to the inner diameter of the heat-transfer tube 1 due to the elastic deformation of the heat-transfer tube 1, thereby bringing the heat-transfer tube 1 into close contact with or pressure contact against the inner tube 5.

Third Mode

[0042] If the outer diameter of the coiled heat-transfer tube 1 is smaller than or equal to the inner diameter of the outer tube 6 (), the heat-transfer tube 1 in its natural state is inserted into the outer tube 6 and, the heat-transfer tube 1 is then compressed after the insertion, the inner diameter of the outer tube 6 comes to be equal to the outer diameter of the heat-transfer tube 1 by the external force, thereby bringing the heat-transfer tube 1 into close contact with or pressure contact against the outer tube 6. Even in a case of , the heat-transfer tube 1 may be pulled to reduce the outer diameter thereof in order to facilitate the insertion.

Fourth Example

[0043] If the outer diameter of the coiled heat-transfer tube 1 is larger than the inner diameter of the outer tube 6 (<), the heat-transfer tube 1 is pulled to reduce the diameter thereof, and then inserted into the outer tube 6. After the insertion, when the pulling force is released and the heat-transfer tube 1 is then compressed, as required, the inner diameter of the outer tube 6 comes to be equal to the outer diameter of the heat-transfer tube 1, thereby bringing the heat-transfer tube 1 into close contact with or pressure contact against the outer tube 6.

TABLE-US-00001 TABLE 1 Relation between Close- diameters contacting before State of heat-transfer External force after component insertion tube 1 during insertion insertion Inner tube 5 Natural state or Pulling force compressed state Inner tube 5 > Compressed state Unnecessary or Pulling force Outer tube 6 Natural state or pulled Compressing force state Outer tube 6 < pulled state Unnecessary or Compressing force

DESCRIPTION OF REFERENCE NUMERALS

[0044] 1: Heat-Transfer Tube [0045] 3: Heating Medium [0046] 4: Coiled Space [0047] 5: Inner Tube [0048] 6: Outer Tube [0049] 8: Lower Closing Part [0050] 9: Upper Closing Part [0051] 11: Tensioning Mechanism