JP2009180452A - Water heat exchanger for water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water heat exchanger for a water heater improving an even heating effect of water by improving heat exchange performance between a heat exchange medium and the water, and capable of effectively suppressing generation of blue water or generation of mound-less type pitting corrosion. <P>SOLUTION: A first inner tube 4 carrying the heat exchange medium of a high temperature is, in one part of its outer circumference face, abutted on and thermally contacted to one part of an outer circumference face of a second inner tube 6 carrying the water and formed by copper or a copper alloy applied with tin plating on an inner face. An inner circumference face of an outer tube 8 is abutted on and thermally contacted to a portion of the outer circumference face of the first inner tube 4 not contacting the outer circumference face of the second inner tube 6. A portion of the outer circumference face of the second inner tube 6 not contacting the outer circumference face of the first inner tube 4 is abutted and thermally contacted with respect to a portion of the inner circumference of the outer tube 8 not contacting the outer circumference face of the first inner tube 4, to compose the water heat exchanger 2 for a water heater. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water heat exchanger for a hot water heater, and more particularly to a water heat exchanger for a water heater for performing heat exchange between a high-temperature heat exchange medium such as a refrigerant mainly composed of carbon dioxide and water. It is.

  Conventionally, as a water heat exchanger for a water heater that performs heat exchange between a high-temperature heat exchange medium (refrigerant) and water, a flow path for circulating the heat exchange medium (hereinafter referred to as a refrigerant flow path). And a flow path (hereinafter abbreviated as a water flow path) through which water to be heat-exchanged is configured by combining two heat transfer tubes, and heat exchange is performed between the refrigerant and water. Various heat exchangers have been used. Moreover, as a heat exchange medium (refrigerant) used in such a water heat exchanger, instead of the conventional chlorofluorocarbon-based refrigerant, the warming coefficient is changed from the viewpoint of protecting the ozone layer and preventing global warming. Low natural refrigerants have attracted attention, and in recent years, water heat exchangers using such natural refrigerants have been developed. Among such natural refrigerants, when carbon dioxide gas is used, it is particularly attracting attention because high-temperature and high-pressure gas conditions can be obtained.

  By the way, as a water heat exchanger for a hot water heater of a type that performs heat exchange between a refrigerant mainly composed of carbon dioxide gas and water, conventionally, the refrigerant is circulated inside as exemplified below. Various proposals have been made in which one heat exchanger is configured by combining a heat transfer tube and a heat transfer tube through which water flows.

  For example, in Japanese Patent Laid-Open No. 2006-170571 (Patent Document 1), a refrigerant is circulated in two inner pipes twisted or twisted in a spiral shape, while the two inner pipes are accommodated. A double-tubular heat exchanger having a structure in which water is allowed to flow in the pipe is disclosed. In this case, the refrigerant flow pipe (inner pipe) on the high temperature side is completely enclosed in the water flow pipe (outer pipe) on the low temperature side. Although it has the advantage that it is kept low, it has the disadvantage that it is difficult to increase the heat transfer area to the water side. For this reason, in patent document 1, although the flow path length is lengthened by twisting the refrigerant flow pipe in a spiral shape and the heat transfer area to the water side is increased, the increase in the heat transfer area is still achieved. This effect was not sufficient, and it was difficult to reduce the size of the heat exchanger.

  Further, in the double multi-tubular heat exchanger proposed in Patent Document 1, there is a risk that the refrigerant leaks into the water flowing outside due to damage of the refrigerant flow pipe, etc. In the case of applying to a water heat exchanger for a water heater, it is necessary to avoid the refrigerant from being mixed into the water used also for beverages. In Patent Document 1, as shown in FIG. The leak detection pipe is employed as a refrigerant flow pipe (inner pipe). However, this complicates the structure and increases the cost.

  On the other hand, in Japanese Patent Application Laid-Open No. 2002-228370 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2006-90697 (Patent Document 3), a refrigerant flow having a structure in which a refrigerant channel tube is disposed outside a water channel tube. Although a heat exchanger of a path pipe winding type has been clarified, the contact area between the water flow path pipe and the refrigerant flow path pipe is sufficient in the structure proposed in Patent Document 2. Therefore, there is a problem that heat transfer performance from the refrigerant to water is low and it is difficult to exhibit sufficient heat exchange performance. For this reason, in order to improve the heat transfer performance of the heat exchanger of such a form, in Patent Document 3, a plurality of mountain valley bottom portions are continuously provided in a spiral shape on the outer periphery of the water flow channel pipe, and the mountain valley bottom portion is provided. However, the contact area is not increased sufficiently, and in addition, the heat from the refrigerant is released to the outside air, resulting in heat exchange performance. It was hard to say that it was a good heat exchanger.

  Furthermore, Japanese Patent Application Laid-Open No. 2003-14383 (Patent Document 4) discloses a heat exchanger having a structure in which a refrigerant channel tube is arranged so as to be pushed into a water channel tube. Since the outer surface is recessed and the coolant channel tube is fitted into the recess, the contact area between the coolant channel tube and the water channel tube is increased compared to the type described in Patent Document 2 above. Although the heat transfer performance could be improved, it was still difficult to say that it was sufficient. In addition, although the form shown by FIG. 5 of patent document 4 arranges two refrigerant | coolant flow path pipes up and down, in order to increase a contact area, the number of such a refrigerant | coolant flow path pipe | tube is used. However, in that case, the disadvantage that the heat of the refrigerant is released from the refrigerant flow pipe to the outside air is not escaped, and the heat exchange performance is good. It cannot be said that it has a good heat exchange performance.

  Here, FIG. 6 shows a cross-sectional view of a heat exchanger 30 configured in the type disclosed in Patent Document 4, in which three refrigerant flow pipes 32 are respectively provided as water flow paths. It is configured in a structure in which it is arranged in close contact with three recesses 36 provided on the outer surface of the tube 34. Moreover, the heat flow from one refrigerant flow pipe 32 in such a heat exchanger 30 is shown in FIG. There, the heat from the refrigerant flowing in the refrigerant channel pipe 32 heats the water flowing through the inner region 40 via the contact portion 38 between the refrigerant channel pipe 32 and the water channel pipe 34, and the heat However, while it is also transmitted to the water flowing through the other regions 42 and 44, the heat from the refrigerant is also dissipated to the outside air 46. In such heat transfer, the temperature of the water in the region 40 close to the contact portion 38 is high, while the water in the region 42 located on both sides of the contact portion 38 and close to the inner peripheral surface of the water flow channel pipe 34 is Under the influence of the outside air 46, the water cannot be heated sufficiently and becomes low-temperature water. For this reason, there is a large difference in water temperature in the water flow path (34), and a soaking state is obtained. It is difficult.

  Moreover, components such as calcium contained in water such as tap water are likely to precipitate in a region heated to a high temperature (approximately 85 ° C. or higher). For this reason, in the inner region 40 described above, The problem inherent in the formation of scale due to precipitation is inherent. Then, by using the heat exchanger 30 for a long period of time, the formed scale adheres to the flow path wall, and the adhesion amount (thickness) increases with time, so that the flow path The problem of reducing the cross-sectional area and eventually closing the flow path is inherent, and such a problem is not limited to the type of Patent Document 4, and Patent Documents 2, 3 It is a problem that can occur even in such types.

  By the way, in these water heat exchangers for water heaters, copper and copper alloys having a high heat exchange rate and good workability are often used as the material constituting the water flow pipe. And, in the case where such a water flow pipe, that is, a portion where water flows is made of copper or a copper alloy, when the pH of the water changes to the acidic side or the alkaline side, the pipe material copper Or a copper alloy becomes easy to melt | dissolve in water as a bivalent copper ion. In addition, the dissolved copper ions react with soap, carbon dioxide gas, etc., and blue water is easily generated.

In addition, the water flowing through these pipes contains various components, and problems caused by such components, for example, when using groundwater with a large amount of free carbonic acid, I 'type pitting corrosion In addition, there is a risk that the divalent copper ions eluted from the tube material precipitate the soluble SiO _{2 in} water to form a scale and cause a moundless pitting corrosion as described above. It was a thing. In addition, these pitting corrosions not only make holes in the heat transfer tubes, but also have a problem that scales such as water scales are easily attached to the surface roughened by the corrosion products on the surface, and the heat exchange performance is deteriorated. Yes.

  For this reason, in order to effectively suppress the formation of scale as described above, it is important to achieve soaking in the water flow path (34), so that water to be heat-exchanged is heated as uniformly as possible. By making it possible, the heat exchange performance and cost advantages are fully demonstrated, scale formation is effectively suppressed, and generation of blue water and moundless pitting corrosion is also effectively suppressed. The realization of a water heat exchanger for a water heater that has a function that can be performed is desired.

JP 2006-170571 A JP 2002-228370 A JP 2006-90697 A JP 2003-14383 A

  Here, the present invention was made in the background of such circumstances, the place to solve the problem is to improve the heat exchange performance from the high temperature heat exchange medium to the water to be heat exchanged, A water heater water heat exchanger that can improve the uniform heating effect of water to be heat-exchanged and effectively suppress the generation of blue water and moundless pitting corrosion is relatively simple and compact. In a simple structure, the manufacturing cost is to be realized at a low cost.

  In the present invention, in order to solve such problems, heat exchange is performed between the first inner pipe through which the high-temperature heat exchange medium is circulated in the pipe and the high-temperature heat exchange medium. A water heat exchanger for a hot water heater comprising a second inner pipe through which water to be circulated and an outer pipe that houses and holds the first and second inner pipes in the pipe; One inner pipe is brought into contact with a part of the outer peripheral surface of the second inner pipe and brought into thermal contact with a part of the outer peripheral surface thereof. While the outer peripheral surface of the tube is not in contact with the inner peripheral surface of the outer tube, the second inner tube is formed of copper or a copper alloy while being in thermal contact with the inner peripheral surface of the outer tube. The inner surface is tin-plated and is not in contact with the outer peripheral surface of the first inner tube of the outer peripheral surface. In the portion, the water for water heaters is brought into contact with a portion of the inner peripheral surface of the outer tube that is not in contact with the outer peripheral surface of the first inner tube, and is in thermal contact with the portion. A heat exchanger is the gist thereof.

  According to one of the desirable embodiments of the water heat exchanger for a water heater according to the present invention, a groove portion extending in the tube axis direction is formed in the outer peripheral surface of the second inner tube so as to be recessed, While the first inner tube is closely accommodated in the groove, the outer tube is advantageously fitted so as to be in close contact with the first and second inner tubes. It will be.

  According to another preferred embodiment of the present invention, the first inner tube and the second inner tube are in contact, the first inner tube and the outer tube are in contact, and The contact between the second inner tube and the outer tube is achieved by mechanical pressure bonding, and thermal contact is formed.

  Furthermore, in the water heat exchanger for hot water supply according to the present invention, desirably, the high-temperature heat exchange medium is configured as a refrigerant mainly composed of carbon dioxide gas.

  Furthermore, according to one of the other desirable embodiments of the water heat exchanger for a hot water heater according to the present invention, the inlet corner of the groove formed in the outer peripheral surface of the second inner pipe is a curved portion, The inner surface of the curved portion is configured as a curved surface having a radius of curvature of 1.0 mm or more in a cross section perpendicular to the tube axis direction.

  Thus, in the water heat exchanger for a hot water heater according to the present invention, high-temperature heat exchange that circulates in the first inner pipe via the thermal contact portion between the first inner pipe and the second inner pipe. The heat from the medium is transferred to the water flowing through the second inner pipe, and the first inner pipe is brought into thermal contact with the outer pipe, thereby The heat from the exchange medium is transferred and diffused to the outer tube, and the heat can be effectively suppressed from being released to the outside air. In addition, the heat transfer action through the thermal contact portion between the outer tube and the second inner tube can also be effectively exhibited, so that the water flowing through the second inner tube is 1 Heat is transferred from the first inner pipe of the book at a plurality of portions of the second inner pipe located around the first inner pipe, and thereby, more effective soaking of water in the second inner pipe. This could be achieved.

  In addition, as described above, the soaking of the water flowing in the second inner pipe is effectively suppressed, so that the formation of the local heating region of the water is effectively suppressed, thereby being included in the water. Precipitation of components such as calcium is advantageously suppressed, and as a result, scale formation can be effectively suppressed.

  Further, according to the present invention, the second inner pipe that is the water flow path is made of a material made of copper or a copper alloy, and the inner surface thereof is tin-plated. It can be effectively suppressed that a certain copper or copper alloy dissolves in water as divalent copper ions. As a result, the generation of blue water during use of the heat exchanger and the heat exchanger can be suppressed. The effective corrosion resistance is advantageously realized.

  In addition, in the water heat exchanger for a water heater according to the present invention, the first inner pipe, the second inner pipe, and the outer pipe that accommodates them are assembled in a form in which they are in contact with each other. The target heat exchanger is formed, in which the first inner pipe through which the high-temperature heat exchange medium is circulated is completely enclosed in the outer pipe. Even when the inner pipe is damaged, the heat exchange medium leaks into the gap between the outer pipe and the first and second inner pipes. Since it has a function and it is not necessary to use a leakage detector tube having a special structure as in the prior art, a water heat exchanger for a water heater can be configured with a relatively simple structure and a compact structure. Therefore, the manufacturing cost can be low. .

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

  First, FIG. 1 and FIG. 2 show an embodiment of a water heat exchanger for a hot water heater according to the present invention. FIG. 1 is a perspective view of one end side cross section showing the arrangement of inner and outer tubes in the longitudinal direction (tube axis direction) of such a water heat exchanger, and FIG. 2 is shown in FIG. It is explanatory drawing which expands and shows the cross section of the direction perpendicular | vertical to a tube axis | shaft which is a cross section of the water heat exchanger. As is clear from these figures, the water heat exchanger 2 includes three of the first inner pipe 4 having a small diameter through which a high-temperature heat exchange medium is circulated and the high-temperature heat exchange medium. A large-diameter second inner pipe 6 in which water to be heat-exchanged between the pipes and the first and second inner pipes 4 and 6 are accommodated and held in the pipe. The outer tube 8 is formed in close contact with each other.

  More specifically, the first inner tube 4 is generally composed of a tubular body having a small outer diameter: about 3 to 7 mm and a wall thickness: about 0.4 to 1.2 mm, and a circular section. Here, the three are arranged with a phase difference of about 120 ° in the circumferential direction. The second inner tube 6 is made of copper or a copper alloy, and is formed of a large-diameter tube body having a size enough to be in contact with the inner surface of the outer tube 8 and having an inner surface plated with tin. A concave groove 10 having a semicircular or arcuate cross section having a depth capable of accommodating the first inner tube 4 is provided on the outer peripheral surface thereof so as to extend in a direction parallel to the tube axis. Further, the concave grooves 10 are arranged in three strips with a phase difference of about 120 ° in the circumferential direction. The first inner tube 4 is accommodated and held in the three concave grooves 10 of the second inner tube 6 so as to be in close contact with the arc-shaped inner surface. -ing

  In addition, the outer tube 8 is generally constituted by a tube having a large diameter of about 12.7 to 25.4 mm and a wall thickness of about 0.4 to 0.8 mm and a circular section. The first and second inner tubes 4 and 6 are accommodated so as to be inscribed in the outer tube 8. In other words, the second inner tube 6 and the first inner tube 4 accommodated in the recessed groove 10 are disposed in the outer tube 8 at the outer peripheral surface portion located at the maximum diameter of the second inner tube 6. It can come into contact with the peripheral surface. Therefore, there, the first inner tube 4 is brought into contact with a part of the outer peripheral surface of the second inner tube 6 and in thermal contact with a part of the outer peripheral surface thereof. Furthermore, the second inner tube 6 is in contact with the inner peripheral surface of the outer tube 8 and in thermal contact with a portion not in contact with the outer peripheral surface of the second inner tube 6. However, in the portion of the outer peripheral surface that is not in contact with the outer peripheral surface of the first inner tube 4, the inner peripheral surface of the outer tube 8 is not in contact with the outer peripheral surface of the first inner tube 4. It has a structure in which they are brought into contact with each other and brought into thermal contact.

  Therefore, in the water heat exchanger 2 having such a structure, as shown in FIG. 3, the heat from the high-temperature heat exchange medium flowing in the first inner pipe 4 is the heat flow. The water flowing through the inner region 14 is heated via the contact portion 12 between the first inner tube 4 and the second inner tube 6 (specifically, the inner surface of the concave groove 10), and the heat Is transferred to the water flowing through the other regions 16 and 18, and at the same time, the heat from the high-temperature heat exchange medium is transferred to the outside through the contact portion 20 between the first inner tube 4 and the outer tube 8. Heat transferred to the tube 8 and further diffused through the outer tube 8 flows through regions 16 located on both sides in the circumferential direction of the groove 10 via the contact portion 22 between the outer tube 8 and the second inner tube 6. It will be transmitted to the water. As a result, the temperature of the water flowing through the regions 16 located on both sides in the circumferential direction of the concave groove 10 of the second inner pipe 6 can be effectively increased, and thus flows through the second inner pipe 6. Therefore, the uniformity of the temperature of the water to be produced can be effectively improved.

  In this way, the uniformity of the temperature of the water circulated in the second inner pipe 6 is improved, and the formation of such a locally heated region of the fluid is suppressed, whereby the second inner tube From the point that the heating temperature of the water flowing in the pipe 6 can be effectively increased, and thus the temperature of the heat exchange medium flowing in the first inner pipe 4 for heating such water can be lowered. The local rise in the water temperature in the region 14 can be advantageously avoided, and the precipitation of components such as calcium in the fluid can be effectively suppressed. As a result, the formation of scale is advantageously suppressed. As a result, even if the water heat exchanger 2 is used over a long period of time, if the cross-sectional area of the flow path is reduced due to the adhesion of the scale to the flow path wall, The problem of blocking the roads Is the need also no longer be taken into.

  Moreover, in the water heat exchanger 2, the opening portion of the concave groove 10 of the second inner tube 6 is surrounded by the first inner tube 4, the second inner tube 6, and the outer tube 8. Since the space 26 is formed in the tube axis direction, when the first inner tube 4 through which the high-temperature heat exchange medium is circulated is damaged, the high-temperature heat exchange medium is It leaks into the space 26 and is guided in the tube axis direction. Therefore, by detecting the presence or absence of such a heat exchange medium in the space 26, the function as a leak detection tube is also exhibited. Therefore, it is not necessary to use a leak detection tube having a complicated structure as in the prior art. Therefore, a water heat exchanger for a water heater is configured as a relatively simple structure and a compact structure. It is possible to make Cost is also to be done and inexpensive.

  In the water heat exchanger 2, as the first inner tube 4 and the outer tube 8, pipes of various metal materials conventionally used in heat exchangers can be used. The outer tube 8 is formed of a material made of copper or copper alloy having a high thermal conductivity, so that the heat exchange performance of the water heat exchanger 2 can be further improved. 4 is also preferably made of a material made of copper or a copper alloy, like the outer tube 8, so that further improvement in heat exchange performance can be expected, in addition to the water heat exchanger. Even when the scrap 2 is scrapped, there is an advantage that the handling becomes easy.

  Further, when the water heat exchanger 2 having such a structure is manufactured, the contact portion 12 between the first inner tube 4 and the second inner tube 6, or the contact between the first inner tube 4 and the outer tube 8. The contact portion 22 between the portion 20 and the second inner tube 6 and the outer tube 8 may be joined by brazing or the like, but in the present invention, these three tubes are used. The technique of mechanically press-fitting each other by means of combined drawing or the like is preferably employed. Incidentally, in the case of brazing, it is easy to cause a shortage of the contact area due to brazing failure, and also tends to cause performance variation, and there is also a concern about problems such as yield reduction due to brazing failure, In a state in which the first inner pipe 4 is assembled in the concave groove 10 of the second inner pipe 6, the three pipe bodies ( 4, 6, and 8) are mechanically pressure-bonded to each other, there is no such problem, and the target water heat exchanger 2 can be advantageously manufactured by a relatively simple processing operation. Become.

  In addition, as a method of applying tin plating to the inner surface of the second inner tube 6 that is a water flow path of the water heat exchanger 2 shown in FIG. 1 or FIG. 2, a conventionally known displacement plating method or chemical method is used. A tin-plated copper pipe and a method for manufacturing the same are appropriately adopted. For example, as disclosed in Japanese Patent Laid-Open No. 4-45282, the inside of the pipe is plated from an end opening of a copper pipe for a water / water heater. A method of manufacturing an inner surface Sn-plated copper tube for a water / water heater can be used in which a liquid is circulated to form a Sn (tin) plating film having a predetermined thickness on the inner surface of the copper tube. According to such a method of performing tin plating on the inner surface of the copper tube by displacement plating or chemical plating, it is possible to form a tin plating film on the inner surface of the copper tube easily and inexpensively. is there.

  By the way, when configuring the water heat exchanger (2) for a water heater, generally, the refrigerant channel pipe (4) and the water channel pipe (6) are assembled and integrated, and then bent. Thus, the final shape of the heat exchanger is finished. In such a water heater water heat exchanger (2), when tin plating is applied to the inner surface of the water flow pipe (6), for example, a heat transfer tube whose inner surface is previously subjected to tin plating is used. When used as a water flow channel pipe, it is assembled with a refrigerant flow channel pipe, and a method of bending is adopted, in particular, a small crack occurs on the surface of tin plating during bending, or depending on the core bar used for bending, There is a risk of damage to the tin plating film. Moreover, there is a risk that the corrosion resistance of the tin-plated film is reduced at the microcracked portion or the missing portion.

  For this reason, the coolant channel pipe and the water channel pipe are assembled, and the integrated one is bent and processed into a final heat exchanger shape, and then the tin plating solution is circulated into the water channel pipe Thus, a displacement plating method or a chemical plating method for forming a tin plating film on the inner surface of the water channel tube is advantageously employed as a method for coating a sound tin plating film in the water channel tube, and By adopting such a technique, it is possible to effectively eliminate the fear that the tin plating film on the inner surface of the water channel pipe will be damaged.

  However, after processing the heat transfer tube into the final heat exchanger shape in this way, the tin plating solution is circulated into the water flow channel tube, and the inner surface of the water flow channel tube is tinned by the displacement plating method or the chemical plating method. In the case of performing a plating film formation process, a sound tin plating film is formed on the entire surface of the flow channel regardless of the shape of the water flow channel pipe through which the tin plating solution is circulated. It is not a thing, but a certain condition is required for the flow path shape.

  Therefore, in the water heat exchanger 2 configured according to the present invention, desirably, a concave groove formed on the outer peripheral surface of the second inner pipe 6 through which water to be heat-exchanged flows. The ten entrance corners 24 have a curved shape, and the inner surface thereof is configured to give a curved surface having a curvature radius (R) of 1.0 mm or more in a cross section perpendicular to the tube axis direction. Are advantageously employed. By adopting such a shape, even when a tin plating film is formed by a displacement plating method or a chemical plating method, a sound tin is formed over the entire inner surface of the second inner pipe 6 that is a water flow path. It is possible to form a plating film. That is, when the curvature radius (R) is less than 1.0 mm, the tin plating solution may not sufficiently flow into the entrance corner 24 and it is difficult to cover with a healthy tin plating film. The fear of becoming.

  Note that the water heat exchanger for a hot water heater according to the present invention is not to be construed as being limited in any way by the specific description according to the exemplary embodiment, and the present invention is based on the knowledge of those skilled in the art. The present invention can be carried out in a mode to which changes, modifications, improvements, and the like are added, and all such modes are within the scope of the present invention as long as they do not depart from the gist of the present invention. It should be understood.

  For example, the first inner tube 4 is arranged in a direction parallel to the tube axis as shown in FIG. 1, and an appropriate number of first tubes are spirally formed in the tube axis direction as shown in FIG. It is also possible to dispose the inner tube 4 of the second inner tube 6, and in this case, the concave groove 10 provided on the outer peripheral surface of the second inner tube 6 also has a tube axis. It will be spirally formed in the direction.

  Further, even when the number of the first inner pipes 4 is arranged, an appropriate number is selected according to the purpose. For example, when four first inner pipes 4 are arranged, As shown in FIG. 5, a structure having a phase difference of about 90 ° in the circumferential direction is advantageously employed.

  In the following, one of the representative embodiments of the present invention will be shown to clarify the features of the present invention. However, the present invention is not restricted by the description of such embodiments. It goes without saying that it is not a thing.

  First, in order to obtain the water heat exchanger (2) according to the present invention having the structure shown in FIGS. 1 to 3, the outer tube (8) has an outer diameter: 17.2 mm, an inner diameter: 15.8 mm, and a wall thickness: A 0.7 mm thick circular tube with a simple circular cross section was prepared. As the first inner tube (4), three smooth circular tubes having an outer diameter of 5.0 mm, an inner diameter of 4 mm, and a thickness of 0.5 mm and having a simple cross section were prepared. Furthermore, as the second inner tube (6), a circular large-diameter smooth tube with a simple cross section having an outer diameter of about 22.2 mm and a wall thickness of 0.7 mm was prepared. The three types of smooth tubes were made of phosphorous deoxidized copper (JIS-H-330-C1220).

  Then, in order to obtain the target water heat exchanger (2), the large-diameter smooth tube that gives the second inner tube (6) is preliminarily shaped into a shape close to the final shape and formed. A small-diameter smooth tube that gives the first inner pipe (4) is inserted and assembled into the arc-shaped concave groove (10), and the assembled pipe is further attached to a large-diameter groove that gives the outer pipe (8). After insertion into the smooth tube, the desired water heat exchanger (2) was produced by subjecting the drawn diameter to expansion and contraction according to a conventional method.

  For comparison, the hydrothermal exchanger (30) shown in FIGS. 6 to 7 without the outer pipe (8) is connected to the first and second inner pipes (4, 6) described above. ) Was used to produce two types of smooth tubes.

Using the two types of water heat exchangers (2, 30) thus obtained, the thermal uniformity of the water flowing through the second inner pipe (6, 34) was evaluated. The conditions such as the flow rate were as follows.
Fluid to be heat exchanged: water
Flow rate: 1L / min, 2L / min,
Outlet temperature: 65 ° C
Heat exchange medium (refrigerant): Carbon dioxide refrigerant
Flow rate: 2 L / min per pipe, total flow rate: 6 L / min
Inlet temperature: 80 ° C
Inlet pressure: 10 MPa

  And in order to evaluate the soaking | uniform-heating property of these two water heat exchangers (2, 30), a thermocouple is affixed on the flow path inner surface near the water outlet (refrigerant inlet) of a heat exchanger, and surface temperature is set. It was measured. As a result, in the water heat exchanger (2) according to the present invention, it was confirmed that the maximum temperature difference of the heated water was within 1 ° C., and the temperature could be effectively equalized. On the other hand, in the conventional water heat exchanger (30) in which the outer pipe (8) is not provided, it is clear that the maximum temperature difference is 2 ° C. and the temperature equalization is not sufficient. became.

It is one end side cross-section perspective explanatory drawing which shows an example of the water heat exchanger for water heaters according to this invention. It is explanatory drawing which expands and shows the cross section of the water heat exchanger for water heaters shown by FIG. FIG. 3 is a partially enlarged partial view of FIG. 2 showing a heat flow. It is explanatory drawing corresponding to FIG. 1 which shows another example of the water heat exchanger for water heaters according to this invention. It is a cross-sectional enlarged explanatory view corresponding to FIG. 2 which shows the further another example of the water heat exchanger for hot water supply according to this invention. It is a cross-sectional explanatory drawing which shows an example of the conventional heat exchanger. It is a partial expansion explanatory view which shows the heat flow of the heat exchanger shown by FIG.

Explanation of symbols

2 Water Heat Exchanger 4 First Inner Tube 6 Second Inner Tube 8 Outer Tube 10 Concave Groove 12, 20, 22 Contact Portion 14, 16, 18 Region 24 Entrance Corner 26 Space

Claims (5)

A first inner pipe in which a high-temperature heat exchange medium is circulated in the pipe, a second inner pipe in which water to be exchanged with the high-temperature heat exchange medium is circulated in the pipe, and the first And a water heat exchanger for a hot water heater constituted by an outer pipe that houses and holds the second inner pipe in the pipe,
The first inner pipe is brought into contact with a part of the outer peripheral surface of the second inner pipe and brought into thermal contact with a part of the outer peripheral surface of the first inner pipe. In the portion that is not in contact with the outer peripheral surface of the inner tube, the second inner tube is made of copper or a copper alloy while being in contact with the inner peripheral surface of the outer tube and being in thermal contact therewith. Formed and tin plated on the inner surface thereof, and in the portion of the outer peripheral surface not in contact with the outer peripheral surface of the first inner tube, the first of the inner peripheral surface of the outer tube A water heat exchanger for a water heater, wherein the water heat exchanger is brought into contact with a portion that is not in contact with the outer peripheral surface of the inner tube and is in thermal contact.   A groove portion extending in the tube axis direction is formed in the outer peripheral surface of the second inner tube so as to be recessed, and the first inner tube is closely accommodated in the groove portion. The water heat exchanger for hot water supply according to claim 1, wherein the outer pipe is externally fitted so as to be in close contact with the second inner pipe.   Contact between the first inner tube and the second inner tube, contact between the first inner tube and the outer tube, and contact between the second inner tube and the outer tube, The water heat exchanger for a water heater according to claim 1 or 2, wherein each is realized by mechanical pressure bonding to form a thermal contact.   The water heat exchanger for a hot water heater according to any one of claims 1 to 3, wherein the high-temperature heat exchange medium is a refrigerant mainly composed of carbon dioxide gas. The entrance corner of the groove formed on the outer peripheral surface of the second inner tube is a curved portion, and the inner surface of the curved portion is 1.0 mm or more in a cross section perpendicular to the tube axis direction. The water heat exchanger for a hot water heater according to any one of claims 2 to 4, wherein the water heat exchanger is a curved surface having a radius of curvature.

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