Title of Invention

A HEAT EXCHANGER AND A METHOD OF PRODUCING THE SAME

Abstract

The present invention relates to a heat exchanger comprising: a substantially cylindrical metal cylinder internally having fins for receiving heat from a combustion gas and also having openings at both ends through which the combustion gas passes, a metal pipe, through which a refrigerant flows, said metal pipe being spirally wound around the outer surface of said metal cylinder in close contact with the outer surface thereof, and fixtures secured to said metal cylinder for securing both ends of said metal pipe to said metal cylinder. The present invention also relates to a method of manufacturing a heat exchanger.

Full Text

TITLE OF THE INVENTION Heat exchanger and method of producing the same BACKGROUND OF THE INVENTION The present invention relates to a heat exchanger for exchanging and transferring the amount of heat of a combustion gas to a refrigerant. I Recently, refrigerant-heating type -air-conditioning apparatus using combustion heat of gas or -oil have been put to practical use. An example of heat exchangers for conventional refrigerant-heating type air-conditioning apparatuses is described below referring to accompanying drawings. FIG. 5 is a perspective view showing a conventional heat exchanger for refrigerant-heating. FIG. 6 is a sectional view showing the heat exchanger for refrigerant-heating shown in FIG. 5. FIG. 7 is an enlarged sectional view showing the copper pipe securing portion of the heat exchanger for refrigerant-heating shown in FIG. 5. As shown in FIG* 5, the conventional heat exchanger for refrigerant-heating comprises a heat exchanger unit 1 and a burner portion 2. The heat exchanger unit 1- comprises an aluminum cylinder 3 and a bent copper pipe 4 secured to the outer surface of the aluminum cylinder 3. In addition, the heat exchanger is configured so that a combustion gas generated at the burner portion 2 provided at one end of the heat exchanger unit 1 flows through the inner space of the aluminum cylinder 3. A refrigerant, such as R22 or water, flows through the bent copper pipe 4 provided around the outer surface, of the aluminum cylinder 3. The aluminum cylinder 3 of the heat exchanger for refrigerant-heating is formed by extrusion, and the interior of the aluminum cylinder 3 is provided with a plurality of fins 3a for absorbing heat from the combustion gas generated at the burner portion 2. As shown in FIGs. 6 and 7, the copper pipe 4, through which a refrigerant for heat exchange flows, is held by caulking copper pipe holders 3b formed on the outer surface of the aluminum cylinder 3 and secured to the aluminum cylinder 3. Since the copper pipe 4 is secured by caulking the copper pipe holders 3b, heat absorbed from the fins 3a and the inner surface of the aluminum cylinder 3 is transferred to the refrigerant flowing through the copper pipe 4 via the copper pipe holders 3b. However, in the case of the conventional heat exqhanger having the above-mentioned structure, a i refrigerant alternately passes the upstream side (high temperature side) and the downstream side (low temperature side) of the combustion gas flowing through the aluminum cylinder 3. This structure causes much heat loss and i reduces heat efficiency. ; In addition, the copper pipe 4 of the conventional heat exchanger has straight pipe portions and J-shaped pipe portions, whereby the number of parts for the copper pipe is increased. Furthermore, the copper pipe 4 is inserted into the copper pipe holders 3b of the aluminum cylinder 3, and then secured to the copper pipe nolders 3b in close contact with them. It is therefore necessary to perform pipe expansion processing for expanding and securing the copper pipe 4 on the entire lengths of the longitudinal straight pipe portions of the copper pipe 4. As described above, the conventional heat exchanger requires many production steps, such as a brazing step for connecting the straight pipe portions to the U-shaped pipe portions and a pipe expansion step, resulting in higher production cost. BRIEF SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat exchanger requiring less production cost and bringing higher heat exchange efficiency. In order to attain the above-mentioned object, the heat exchanger of the present invention comprises: a substantially cylindrical metal cylinder internally having fins for receiving heat from a combustion gas and also having openings at both ends through which the combustion gas passes, 3 metal pipe, through which a refrigerant flows, said metal pipe being spirally wound around the outer surface of the metal cylinder in close contact with the outer surface thereof, and fixtures secured to the metal cylinder for securing both ends of the metal pipe to the metal cylinder. The above-mentioned structure of the heat exchanger of the present invention enhances heat exchange ; l! ■ efficiency and reduces production cost significantly. Furthermore, the production method for the heat exchanger of the present invention comprises steps of: screwing a first fixture to one end of the outer surface of the metal cylinder internally having fins for receiving heat from a combustion gas and also having openings at both ends thereof, securing one end of the metal pipe, through which a refrigerant flows, to the first fixture, winding the metal pipe around the outer surface of the metal cylinder in close contact with the outer surface thereof by rotating the metal cylinder in a predetermined direction, screwing a second fixture to the other end of the outer surface of the metal cylinder after the metal pipe is wound around the metal cylinder so as to have a predetermined number of turns, securing the metal pipe to the second fixture, and J\ cutting the metal pipe to a desirable length. The production method for the heat exchanger of the present invention requires less processing steps and is simple, thereby reducing production cost significantly. While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1 is a front view showing a heat exchanger in accordance with a first embodiment of the present invention; FIG. 2 is a side view showing the heat exchanger shown, in FIG. 1; FIG. 3 is.a magnified sectional view showing the details of a copper pipe securing portion in the heat exchanger in accordance with the first embodiment; FIG. 4 is a side view showing a method of winding a copper pipe in the heat exchanger in accordance with the present invention; FIG. 5 is the perspective view showing the conventional heat exchanger; FIG. 6 is the sectional view showing the conventional heat exchanger of FIG. 5; and FIG. 7 is the enlarged sectional view showing the details of the copper pipe securing portion in the conventional heat exchanger. It will be recognized that some or all of the Figures are schematic representations for purposes of . 'i illustration and do not necessarily depict the actual r^latjive sizes or locations of the elements shown. DETAILED DESCRIPTION OF THE INVENTION Preferable embodiments of the heat exchanger of the present invention are described below referring to drawings. A first embodiment of the heat exchanger of the present invention is described below referring to accompanying drawings. FIG. 1 is a front view showing a heat exchanger in accordance with the first embodiment of the present invention, and FIG. 2 is a side view showing the heat exchanger shown in FIG. 1. The heat exchanger shown in FIG. 1 is for refrigerant-heating for an ©ir-conditioning apparatus. This heat exchanger for refrigerant-heating is used during heating operation to heat a refrigerant. As shown in FIG. 1, the heat exchanger.for refrigerant-heating in accordance with the first embodiment comprises a heat exchanger unit 10 and a burner portion 11 provided at the right end of the heat exchanger unit 10. The heat exchanger unit 10 comprises a metal cylinder 12 which is for passing a hot gas therethrough and a metal pipe 13 which is for passing a refrigerant. The metal pipe 13 is sedured around the outer surface qf the metal cylinder 12. In the first embodiment, the metal cylinder 12 is an aluminum cylinder formed by extruding aluminum, and the metal pipe 13 is made of copper. Hereinafter, the metal cylinder 12 is referred to as "aluminum cylinder 12." and the metal pipe 13 is referred to as "copper pipe 13." As shown in FIGs. 1 and 2, the copper pipe 13 is woun^ around the outer surface of the aluminum cylinder 12 in the direction substantially orthogonal to a generating line of the outer surface of the aluminum cylinder 12. The copper pipe 13 is wound around the aluminum cylinder 12 to have a plurality of turns, with the adjacent pipe portions of the copper pipe 13 being in close contact with each other. In other words, the copper pipe 13 is wound around the outer surface of the aluminum cylinder 12 is spiral manner approximately along a periphery of a circle defined by the intersection of a plane substantially orthogonal to the center axis of the aluminum cylinder 12 and the outer surface of the aluminum cylinder 12. A refrigerant, such as R22 or water, flows through the copper pipe 13. The burner portion 11 provided at one end of the heat exchanger unit 10 is structured so as to cause a combustion gas to flow into the inner space of the aluminum cylinder 12. The aluminum cylinder 12 of the heat exchanger for refrigerant-heating is formed by extrusion, A plurality of fins 12a, 12b for efficiently exchanging heat from the combustion gas generated at the burner portion 13, are provided inside the aluminum cylinder 12. As shown in FIG. 2, the fins 12a are formed to have large shapes and the fins 12b are formed to have small shapes, and these large and small fins are provided alternately to enhance the effect of absorbing heat from the combustion gas. The fins 12a, 12b are a plurality of band-shaped projections extending in the direction substantially parallel to,the flow direction of the combustion gas. FIG. 3 is a magnified sectional view showing the details of a copper pipe securing portion in the heat exchanger for refrigerant-heating in accordance with the first embodiment. As shown in FIGs. 2 and 3, the copper pipe 13 is wound spirally around the outer surface of the aluminum cylinder 12 in close contact with the outer surface thereof with .the adjacent pipe portions of the copper pipe 13 making close contact with each other. The refrigerant inlet end and the outlet the refrigerant end of the copper pipe13 are secured to the aluminum cylinder 12 with two I '. fixtures, namely copper fixtures 15, 15. As shown in FIG. 3, the copper fixture 15 is secured with a screw 14 to the outer surface of the aluminum cylinder 12. In addition; the copper pipe 13 is welded to the copper fixture 15 by silver-alloy brazing, whereby the copper pipe 13 is firmly secured to the aluminum cylinder 12. The copper pipe 13, through which a refrigerant for heat exchange flows, is secured to the outer surface of the aluminum cylinder 12 in close contact with the outer surface thereof. Therefore, the heat of the combustion gas absorbed from the inner surface of the aluminum cylinder 12 and the large and small fins 12a, 12b formed on the inner surface of the aluminum cylinder 12 is transferred to the refrigerant flowing through the copper pipe 13 via the copper pipe 13. In the heat exchanger for refrigerant-heating in accordance with the first embodiment having the above-mentioned structure, the combustion gas generated at the burner portion 11 flows into the aluminum cylinder 12 of the heat exchanger unit 10,and the heat of the combustion gas is transferred to the aluminum cylinder 12 via the fins 12a, 12b. In the copper pipe 13, the refrigerant enters one end .of the copper pipe 13 disposed at the high-temperature portion of the aluminum cylinder 12 (the right side of the aluminum cylinder 12 in FIG. 1), namely the upstream side of the combustion gas. The refrigerant then flows to the other end of the copper pipe 13 disposed at the low-temperature portion of the aluminum cylinder 12 (the left side of the aluminum cylinder 12 in FIG. 1), namely the downstream side of the combustion gas, while absorbing heat. As described above, the heat exchanger for refr(igerant-heating in accordance with the first embodiment of the present invention is structured so that the refrigerant gradually flows from the high-temperature portion to the low-temperature portion of the heat exchanger unit 10. Therefore, the heat exchanger has far smaller heat loss 'and far higher heat exchange efficiency than the above-mentioned conventional heat exchanger. In addition, since the copper pipe 13 of the heat exchanger for refrigerant-heating in accordance with the first embodiment comprises a single copper pipe, the number of parts is far less than that for the conventional heat exchanger. Furthermore, the number of production processing steps for securing the copper -pipe 13 in accordance with the first embodiment is far less than that in accordance with the conventional production method. Consequently it is possible to attain significant reduction in production cost. Moreover, effects similar to those obtained by the above-mentioned first embodiment can also be obtained even when a nonfreezing liquid or the like is used as a refrigerant flowing through the copper pipe instead of R22 or water. Next, a heat exchanger in accordance with a second embodiment of the present invention is described below referring to accompanying drawings. FIG. 4 is a side sectional view showing a method of producing the heat exchanger in accordance with the second embodiment of the present invention. In accordance with the second embodiment, corresponding parts and components to the first embodiment are designated by the same numerals and the description thereon made in the first embodiment similarly apply. The heat exchanger in accordance with t i the second embodiment is substantially the same as the ! heat .exchanger for refrigerant-heating in accordance with the first embodiment. The second embodiment deals with a method of producing the heat exchanger for refrigerant-heating in accordance with the first embodiment. A method of producing the heat exchanger in accordance with the second embodiment is described below referring to FIG. 4. A As shown in FIG. 4, a plurality of large and small fins 12a, 12b for heat exchanging efficiency are formed alternately on the inner surface of an aluminum cylinder 12 formed by extruding aluminum. As shown in FIG. 4, large fins 12a?, and small fin 12b1 are formed on a projection 120 provided on the upper inner surface of the aluminum cylinder 12. The projection 120 is a part of the inside wall which is thicker than other portions of the aluminum cylinder 12. Copper fixtures 15 for securing a copper pipe 13 to be wound around the outer surface of the aluminum cylinder 12 are secured to the pedestal portions 120 with screws 14. By forming the pedestal portions 120 used for securing by screwing as described above, the screws 14 is prevented from being loosened and from being deteriorated due to exposure to heat at the i aluminum cylinder 12. When the copper pipe 13 is wound around the outer surface of the aluminum cylinder 12, the copper fixture 15 is first secured with the screw 14 at a predetermined position at one end of the outer surface of the aluminum cylinder 12. Next, the copper pipe 13 is inserted into a cpace between the aluminum cylinder 12 and the copper fixture 15. The copper pipe 13 is then welded by silver-alloy brazing to secure one end of the copper pipe 13 to the copper fixture 15. FIG. 4 shows a condition wherein the end of the copper pipe 13 has been secured to the copper fixture 15. Referring to FIG. 4, the aluminum cylinder 12 is rotated around the center axis thereof in the direction indicated by arrows A while a tension is applied to the copper pipe 13. As a result, the copper pipe 13 is wound spirally in close contact with the outer surface of the aluminum cylinder 12. At this time, the copper pipe 13 is wound a predetermined number of turns so that the adjacent pipe portions make close contact with each other. t After the copper 13 is wound around the aluminum cylinder 12 to have a predetermined number of turns, the trailing end of the wound portion of the copper pipe 13 is secured with another copper fixture 15 to the aluminum cylinder 12. The trailing end of the copper fixture 15 is screwed to the aluminum cylinder 12 so as to press the copper pipe 13 against the aluminum cylinder 12, just as the leading end of the wound portion of the copper pipe 13 is secured (FIG. 3). The trailing end of the copper pipe 13 is then secured to the copper fixture 15 by brazing. After the trailing end of the copper pipe* 13 is secured to the aluminum cylinder 12, the copper pipe 13 is cyt at a desirable position. The heat exchanger in accordance with the second embodiment of the present invention is produced as described above, k As clearly disclosed in the description of the ebove-mentioned second embodiment, the heat exchanger of !. .1 the, present invention is produced by directly winding a single copper pipe, namely the copper pipe 13, around the aluminum cylinder 12, Therefore, unlike the conventional heat exchanger shown in FIGs, 5 to 7, the heat exchanger of the present invention does not require pipe expansion processing for closely contacting the copper pipe with the metal cylinder or welding processing for connecting the straight pipe portions to the U-shaped pipe portions of the conventional copper pipe. Consequently, the production method for the heat exchanger of the present invention can reduce the number of production steps and production cost significantly. As described above, in the heat exchanger of the present invention, a copper pipe used as a metal pipe for flowing a refrigerant around the outer surface of an aluminum cylinder used as a metal cylinder having fins for receiving heat from a combustion gas is wound closely around the aluminum cylinder. Both ends of the metal pipe are welded to copper fixtures, and the fixtures are secured with screws. Because of the above-mentioned structure of the heat exchanger of the present invention, a refrigerant flows from the high-temperature portion to the low-temperature portion of the metal cylinder in this sequence. Therefore, the heat exchange efficiency of the heat exchanger of the present invention is improved significantly. Furthermore, since the metal pipe of the heat exchanger of the present invention comprises a single pipe, the number of metal pipe parts is far less than that of the conventional example, whereby it is possible to significantly reduce production cost. Moreover, in the heat exchanger of the present invention, a fixture is screwed to one end of the outer surface of the metal cylinder, and one end (inlet side) of the metal pipe for causing a refrigerant to flow is welded to the fixture. The metal cylinder with the metal pipe secured thereto as described above is rotated so that the metal pipe is wound while the metal pipe makes close contact with the outer surface of the metal cylinder. After the metal pipe is wound up to the other end (outlet side) thereof, the metal pipe is secured with a fixture which is screwed to the outer surface of the metal cylinder. The outlet side of the metal pipe is secured to the fixture by welding, and then cut to have a desirable length for connection. This completes the production of the|heat exchanger of the present invention. ". i As described above, the production method for the heat exchanger of the present invention does not require complicated and troublesome processes, in which the metal pipe is put in the longitudinal holders and the ■. i longitudinal holders are caulked to hold the metal pipe, as the aforementioned conventional production method. As i a result, the production method can reduce the number of production steps and production cost significantly - Apart from the above-mentioned embodiment wherein the metal pipe is welded by silver-alloy brazing to the fixture, a modified embodiment may be such that the metal pipe is welded by another connecting means, such as phosphor copper-alloy brazing. Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains, after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention. We Claim: 1. A heat exchanger comprising: a substantially cylindrical metal cylinder (12) internally having fins (12a, .12b) for receiving heat from a combustion gas and also having openings at both ends through which the combustion gas passes, a metal pipe (13), through which a refrigerant flows, said metal pipe being spirally wound around the outer surface of said metal cylinder (12) in close contact with the outer surface thereof, and fixtures (15) secured to said metal cylinder (12) for securing both ends of said metal pipe (13) to ' . i ! ■ v said metal cylinder (12). ■' | M ' ... 2* A heat exchanger in accordance with claim 1, wherein" I said metal pipe (13), through which a refrigerant flows> is wound in the direction substantially orthogonal to the generating line of the outer surface of said metal cylinder (12), and the adjacent pipe portions of said metal pipe (13) are disposed in close contact with each other. 3. A heat exchanger in accordance with claim 1, wherein said fins (12a, 12b) are formed as a plurality of band-shaped projections extending in the direction substantially parallel to the flow direction of the combustion gas, said fins (12a, 12b) are formed in substantially two sizes, namely taller type and non taller type, in height of said projections from the inner surface of said metal cylinder (12), and the two types of said projections are disposed alternately. 4. A heat exchanger in accordance with claim 1, wherein a projection (120) is a part of wall Qf said metal cylinder12), and said projection (120) is thicker than other (portions of said metal cylinder (12) for fixing said fixture (15). 5. A heat exchanger in accordance with claim 1, wherein said metal cylinder (12) is formed by extruding aluminum, and said metal pipe (13) and said fixtures (15) are made of copper. 6. A production method of a heat exchanger comprising steps of: screwing a first fixture (15) to one end of the outer surface of said metal cylinder (12) internally having fins (12a, 12b) for receiving heat from a combustion gas and also having openings at both ends thereof, securing one end of said metal pipe (13), through which a refrigerant flows, to said first fixture (15), winding said metal pipe (13) around the outer surface of said metal cylinder (12) in close contact with the outer surface thereof by rotating "said metal cylinder (12) in a predetermined direction, screwing a second fixture (15) to the other end of the! outer surface of said metal cylinder (12) after 1 said metal pipe (13) is wound around said metal cylinder (12) so as to have a predetermined number of turns, securing said metal pipe (13) to said second fixture (4.5), and cutting said metal pipe (13) to a desirable length. 7. A heat exchanger, substantially as herein described, with reference to the accompanying drawings. 8. A product ion method of a heat exchanger, ■i substantially as herein described, with reference to the accompanying drawings.

Documents:

2547-mas-1997-abstract.pdf

2547-mas-1997-claims duplicate.pdf

2547-mas-1997-claims original.pdf

2547-mas-1997-correspondance others.pdf

2547-mas-1997-correspondance po.pdf

2547-mas-1997-description complete duplicate.pdf

2547-mas-1997-description complete original.pdf

2547-mas-1997-drawings.pdf

2547-mas-1997-form 1.pdf

2547-mas-1997-form 19.pdf

2547-mas-1997-form 26.pdf

2547-mas-1997-form 3.pdf