Heat exchanger

Abstract: A heat exchanger for a hot-water storage type gas boiler, provides an easily assembled stacked-up heat exchanger eliminating the installation of a separate hot-water pipe so that the thermal efficiency of a heat exchanger can be improved and the size thereof can be reduced. The stacked-up type heat exchanger comprises a bottom plate (600) including one or more combustion gas flues (602) for carrying combustion gas made in a burner, a return heating-water outlet (606) for delivering heating-water, and a cold-water inlet (604) for allowing in water; a first plate (100) disposed over the bottom plate (600); a fourth plate (400) disposed over the first plate (100); and a top plate (500) disposed over the fourth plate (400).

Description: The present invention relates to a heat exchanger for a gas boiler. In a conventional hot-water storage type gas boiler, a heat exchanger comprises a cylinder with a plurality of pipes therein to carry fresh water from the lower portion to the upper portion, a heating-water outlet and a return heating-water inlet disposed at the upper portion and the lower portion of the cylinder respectively, and a burner therebeneath for heating water. U.S. patents Nos. 4,432,307 and 4,644,904 disclose heat exchangers used in such hot-water storage type gas boilers. However, with the known heat exchanger for a gas boiler, as the flue and a separate hot-water pipe are installed in the heat exchanger, manufacture of the heat exchanger involves a difficult welding process. Furthermore, in order to increase the thermal efficiency of such a heat exchanger, it is necessary to increase the size of the heat exchanger, which increases the manufacturing cost and the manufacturing time. EP-A-0404259 describes a heat exchanger comprising a plurality of plates stacked one above the other and providing one or more gas flues for passage of exhaust gas, a first passageway for water to be heated, and a second passageway for heating-water, the passageways and the flue or flues being formed by cooperating portions of the plates, and wherein one or more gas flues extend upwardly through the stack with each said gas flue being defined by a respective combustion gas flue from each of said plates. As this heat exchanger is formed of a stack of plates it avoids the need for a separately welded hot-water pipe. According to the present invention a heat exchanger of the type defined above is characterised in that the plates from which the stack is made have a number of different configurations, in that cooperating portions of the plates together define said first passageway for the flow of water to be heated, the first passageway extending from a cold water inlet or a hot water outlet in the bottom one of the stacked plates to the hot water outlet or the cold water inlet in the top one of the stacked plates, and the first passageway spiralling around said gas flues, and in that said second passageway for heating-water is defined by spaces between adjacent ones of the plates interconnected by heating-water inlets in selected ones of the plates, said second passageway communicating with a heating-water inlet or outlet in the bottom plate and a heating-water outlet or inlet in the top plate. An embodiment of a heat exchanger of the invention may be used in a gas boiler and has an improved thermal efficiency as compared to the conventional heat exchanger. Thus, a smaller heat exchanger than the conventional one can be employed. As a heat exchanger of the invention is formed from stacked plates, it may be manufactured in a cost-effective manner. In an embodiment, said stacked plates comprise a bottom plate, a first plate, a fourth plate and a top plate, and the first plate has one or more said heating-water inlets, and a downwardly extending curved portion arranged to define, with an upwardly extending curved portion of said fourth plate, said first passageway for the flow of water to be heated, said first passageway being substantially ring-shaped and having a radius from the centre of the first and fourth plates, and the fourth plate also having one or more said water-heating inlets. In an alternative embodiment, said stacked plates comprise a bottom plate, first to fourth plates, and a top plate, and each of the first to fourth plates has one or more of said water-heating inlets, the first and third plates each having a downwardly extending curved portion, and the second and fourth plates each having an upwardly extending curved portion, each downwardly extending curved portion cooperating with a respective upwardly extending curved portion of the adjacent plate to thereby define said first passageway for the flow of water to be heated, said first passageway being substantially ring-shaped and having a radius from the centre of said first to fourth plates. Preferably, the heat exchanger further comprises two or more combined sets of stacked plates interposed between said bottom plate and said top plate, each said stacked set of plates comprising a first plate, a second plate, a third plate and a fourth plate. Preferably, at an end of each of the combustion gas flues, a baffle for delaying the flow of exhaust gas is provided. If preferred, the return heating-water outlet of the bottom plate can serve as a return heating-water inlet and the return heating-water inlet of the top plate, as a return heating-water outlet. Likewise, the cold-water inlet of the bottom plate and the hot-water outlet of the top plate can reverse their roles. In use of the heat exchanger, high temperature exhaust gas may be flowed through the gas flue(s), cold-water is entered and hot-water is delivered through the first passageway, and heating-water for heating a room enters the heat exchanger through the return heating-water inlet and goes out through the return heating-water outlet after heat exchange. Exhaust gas may enter through the combustion gas flue of the bottom plate, makes a heat exchange while passing through the combustion gas flues of the mid plates and is finally delivered through the combustion gas flue of the top plate. Water flows in the following way to provide a supply of hot-water. Cold-water supplied by the cold-water inlet of the bottom plate is entered into the first passageway and flows along the passageway. The passageway is formed of a doughnut shaped hot/cold flowing or supply pipe and spirals around the gas flues whereby heat exchange takes place. The water flows through several hot/cold-water flowing tubes such that it attains higher temperatures to provide hot-water. The hot-water is delivered to the hot-water outlet via the hot-water delivery pipe. Returning heating-water enters into the heat exchanger through the return heating-water inlet of the top plate, for example, and makes a heat exchange while flowing around the combustion gas flues. The heating-water between the top plate and the fourth plate is delivered to a space formed by the fourth plate and the third plate through the heating-water inlet. That is to say, while heating-water flows downwardly, the heat exchange is made and the heating-water that has reached the bottom plate is delivered out of the heat exchanger through the return heating-water outlet. It will be appreciated that in an embodiment of a heat exchanger of the invention a separate hot-water pipe is not installed in a heat exchanger by a hard welding method. The pipe is formed by a simple welding of the stack of plates. Furthermore, the stacked-up type heat exchanger of the invention has an improved thermal efficiency as compared to a conventional heat exchanger whereby the size of the heat exchanger can be reduced and the manufacturing cost similarly reduced. Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: FIG. 1 is a sectional view of a heat exchanger for a conventional hot-water storage type gas boiler; FIG. 2 is a center-line sectional view showing an embodiment of a heat exchanger for a gas boiler of the invention; FIG. 3 is a sectional view showing another embodiment of a heat exchanger of the invention; FIG. 4 is a top plan view of a first plate of the heat exchanger of FIG. 2; FIG. 5 is a top plan view of a second plate of the heat exchanger of FIG. 3; FIG. 6 is a top plan view of a bottom plate of the heat exchanger of FIG. 2; and FIG. 7 is a top plan view of a top plate of the heat exchanger of FIG. 2. FIG. 1 is a front sectional view for showing one of the embodiments of a conventional heat exchanger for a hot-water storage type gas boiler. According to FIG. 1, a heat exchanger 1 includes a heating-water heating portion 3 for heating and storing heating-water and a hot-water pipe 4. Inside heating-water heating portion 3 a plurality of flues 2 vertically passing through heating-water heating portion 3 are provided to carry exhaust gas with high temperature. At an upper portion of the outer wall of heating-water heating portion 3 a heating-water outlet 31 for delivering high temperature heating-water is provided and a return heating-water inlet 30 is disposed at the lower portion thereof. Hot-water pipe 4 made in a constant spiral line is disposed around the inner periphery of heating-water heating portion 3 to thereby make a heat exchange between hot/cold-water and heating-water. Hot-water pipe 4 also includes a cold-water inlet 40 and a hot-water outlet 41 at the lower and upper portions of heat exchanger 1 respectively so that hot/cold-water can come in and out of heating-water heating portion 3. At cold-water inlet 40 a supplementary water valve 9 is provided for supplying heating-water with supplementary water. At the lower portion of heat exchanger 1, a gas supply pipe 7 and a manifold 8 for jetting supplied fuel through gas supply pipe 7 to combustion points are provided. In addition, a baffle, not shown in FIG. 1, is provided inside flue 2 to delay the flow of exhaust gas so that more heat is transferred to heating-water. An exhaust hood 6 is mounted on heat exchanger 1 to suck the exhaust gas risen through flue 2. In the heat exchanger for a boiler constructed as above, an exhaust gas with high temperature is generated by burning the gas blown from manifold 8. The exhaust gas enters into flue 2 through a bottom surface of heat exchanger 1. At this time, the exhaust gas rising up through flue 2 exchanges heat with heating-water by way of the wall of flue 2. As such, the temperature of heating-water increases and hot-water pipe 4, located within the heating-water, is also affected by the heat. Cold-water entered into heat exchanger 1 through cold-water inlet 40 is affected by the heat while passing through hot-water pipe 4 and thereafter high temperature water is delivered out of heat exchanger 1 through hot-water outlet 41. Exhaust gas that has passed through flue 2 is concentrated at exhaust hood 6 and is exhausted out of a boiler. FIG. 2 is a cross sectional view along the center-line of the heat exchanger for a gas boiler according to the present invention. As shown in FIG. 2, the heat exchanger for a gas boiler according to the present invention is composed of a plurality of plates stacked up one over another. Hereunder, each of the plates will detailedly be described from the bottom to top portion. A bottom plate 600 has a plurality of combustion gas flues 602 passing through from bottom to top. At the end of each of combustion gas flues 602 a baffle 607 is provided for partially blocking the opening hole of combustion gas flue 602. On bottom plate 600 a cold-water inlet 604 is provided while forming a through hole. At the periphery of bottom plate 600 a circumferential bent jaw with the same height as combustion gas flue 602 is provided. At a part of the circumferential jaw a return heating-water outlet 606 is provided by making a through hole. A first plate 100 has a combustion gas flue 102 with the same form of combustion gas flue 602 of bottom plate 600 provided at an area corresponding to combustion gas flue 602 of the bottom plate 600. At an area corresponding to cold-water inlet 604, a cold-water supply pipe 108 protruded from first plate 100 toward bottom plate 600 is provided. Cold-water supply pipe 108 is connected to a lower part of a curved portion 106 formed by first plate 100. Curved portion 106 is formed in the shape of a doughnut around combustion gas flue 102 with the center of the axis of a heat exchanger. At the center of first plate 100, at the bottom surface between combustion gas flue 102 and curved portion, and at the bottom surface between curved portion 106 and the circumferential jaw, a plurality of heating-water inlets 104 are provided throughout from bottom to top. A fourth plate 400 is similar to first plate 100 in basic structure, however, the upper and lower surfaces thereof are inversed in a 180-degree arc and the direction in which combustion gas flue 402 protrudes is opposite to first plate 100. A top plate 500 includes a combustion gas flue 502 in the identical shape of combustion gas flues 102, 402 and 602 of bottom plate 600, first plate 100 and fourth plate 400. At an area corresponding to hot-water delivery pipe 408 of fourth plate 400 a hot-water outlet 504 is provided. At a part of top plate 500 a return heating-water inlet 506 is disposed. FIG. 3 is a sectional view of a heat exchanger wherein a second plate and a third plate are reciprocally stacked up according to another embodiment of the present invention. As shown in FIG. 3, the structures of bottom plate 600, first plate 100, fourth plate 400 and top plate 500 are the same as shown in FIG. 2. A second plate 200 has a combustion gas flue 202 in the same form of combustion gas flue 102 of first plate 100, which second plate 200 is disposed at the corresponding area to combustion gas flue 102 of first plate 100. At an area corresponding to curved portion 106 of first plate 100 a curved portion 206 with the inversed shape of curved portion 106 of first plate 100 is provided. A hot/cold-water flowing tube 702 is formed by fitting curved portion 106 of first plate 100 together with curved portion 206 of second plate 200. At a part of hot/cold-water flowing tube with a maximum distance from cold-water supply pipe 108 of first plate 100, a cold-water discharge outlet 208 is provided while connecting the lower part of curved portion 206 of second plate 200. At a bottom surface of second plate 200 corresponding to heating-water inlet 104, a heating-water inlet 204 with the same shape of heating-water inlet 104 is provided. A third plate is similar to first plate 100 in basic structure but it is differentiated in that a cold-water supply pipe 308 is situated at the 180-degree opposite side of cold-water supply pipe 108 of first plate 100. FIG. 4 is a top plan view of the first plate according to FIG. 2. As shown in FIG. 4, first plate 100 is formed in the shape of a circle and includes combustion gas flue 102, heating-water inlet 104 and a cold-water supply pipe 108. A total of 8 combustion gas flues 102 are disposed symmentrically around the center of the plate. At each of combustion gas flues 102 baffle 207 is installed. Between combustion gas flues 102 and at the outer area, a total of 13 heating-water inlets 104 are provided. Around combustion gas flues 102 curved portion 106 is provided which finally forms hot/cold-water flowing tube 702. At the lower part of hot/cold-water flowing tube 702 a cold-water supply pipe 108 is provided. At a part of curved portion 106 a flowing hole A which crosses the curved portion 106 is formed. FIG. 5 is a top plan view of the second plate according to FIG. 3. As shown in FIG. 5, second plate 200 is formed in the shape of a circle and includes combustion gas flue 202, heating-water inlet 204 and a cold-water supply pipe 208. A total of 8 combustion gas flues 202 are disposed symmetrically around the center of the plate. At each of combustion gas flues 202 baffle 207 is installed. Between combustion gas flues 202 and at the outer area, a total of 13 heating-water inlets 204 are provided. Around combustion gas flues 202 curved portion 206 is provided which finally forms hot/cold-water flowing tube 702. At the lower part of hot/cold-water flowing tube 702 a cold-water supply pipe 208 is provided at the opposite side of cold-water supply pipe 108 of first plate 100. At a part of curved portion 206 a flowing hole A which crosses the curved portion 206 is formed. FIG. 6 is a top plan view of the bottom plate according to FIG. 2. As shown in FIG. 6, bottom plate 600 is formed in the shape of a circle and includes combustion gas flue 602 and cold-water inlet 604. A total of 8 combustion gas flues 602 are disposed symmetrically around the center of the plate. At each of combustion gas flues 602 baffle 607 is installed. At a part of bottom plate 600 corresponding to the area of cold-water supply pipe 108, cold-water inlet 604 is provided. FIG. 7 is a top plan view of the top plate according to FIG. 2. As shown in FIG. 7, top plate 500 is formed in the shape of a circle and includes combustion gas flue 502, hot-water outlet 504 and return heating-water inlet 506. A total of 8 combustion gas flues 502 are disposed symmetrically around the center of the plate. At each of combustion gas flues 502 baffle 507 is installed. At an area corresponding to hot-water delivery pipe 408 hot-water outlet 504 is formed. At a part of top plate 500 return heating-water inlet 506 is provided. Those plates described in the foregoing are readily made by drawing and bending sheet metal by use of press mold. Each of those plates are fitted together by braze welding after being stacked up one over another. In the heat exchanger for a gas boiler according to the present invention constructed as above, hot-water and heating-water are respectively made through heat exchange with exhaust gas. At this time, hot/cold-water, heating-water and exhaust gas flow through their own passages so they are not mixed nor directly contact one another. As shown in FIG. 3, the flowing path of the exhaust gas is as follows. High temperature exhaust gas generated by the combustion of gas flows up through combustion gas flue 602 of bottom plate 600. The exhaust gas conflicts with baffle 607 at the end of combustion gas flue 602 and the rising speed thereof is lowered. Thereafter the exhaust gas is entered into combustion gas flue 102 of first plate 100. The exhaust gas in combustion gas flue 102 of first plate 100 flows into combustion gas flue 202 of second plate 200 by the same course as that of bottom plate 600. By such a way, exhaust gas passes through the combustion gas flue of each of the plates, reachs the top, and finally goes out of a heat exchanger. Hot/cold-water for supplying a user with hot-water flows in the following way. Cold-water supplied by cold-water inlet 604 of bottom plate 600 is entered into hot/cold-water flowing tube 702 formed between first plate 100 and second plate 200 through cold-water supply pipe 108. The cold-water that has flowed thereinto fills hot/cold-water flowing tube 702 in the shape of a doughnut and flows up through cold-water supply pipe 308 of third plate 300 via cold-water discharge outlet 208. At this time, the cold-water is warmed by the heat exchange with heating-water therearound. The cold-water which has entered into hot/cold-water flowing tube 704 is delivered to the opposite side hot-water delivery pipe 408 by a similar way in hot/cold-water flowing tube 702. The water that has passed through hot-water delivery pipe 408 finally becomes hot and goes out of a heat exchanger through hot-water outlet 504. At this time, hot-water outlet 504 is connected with a hot-water pipe (not shown) so hot-water can be delivered to a desired place. Heating-water flows in the following way. Cold heating-water that has been delivered to a heat exchanger through a heating pipe in a room enters into a heat exchanger through a heating pipe (not shown) connected to return heating-water inlet 506. The entered heating-water flows into space between top plate 500 and fourth plate 400 and thereafter into space formed between fourth plate 400 and third plate 300 through a plurality of heating-water inlets 404. The heating-water reaches bottom plate 600 through heating-water inlets 304, 204 and 104 formed at each of the plates respectively. The heating-water that has reached bottom plate 600 does not go out until bottom plate 600 is filled up to a certain level since a heating-water inlet is not provided at the bottom of bottom plate 600. The heating-water flowing through the plate is intermixed with other heating-water around flowing hole A provided at the curved portion. The heating-water intermixing is also made in each of the plates in such a manner. If a boiler with a larger thermal capacity is required, a couple of plates consisting of first plate 100 and second plate 200 or third plate 300 and fourth plate 400 can additionally be inserted between the bottom plate and the top plate. In such a case, the inserted plates are preferably provided in the way that the cold-water supply pipes are reciprocally provided while maintaining a 180-degree arc against the axis of heat exchanger. The inserted plates increase the area of thermal exchange and accordingly the flow of hot/cold-water and heating-water can be facilitated. Depending upon necessity, the direction of the flow of heating-water can be inversed by changing return heating-water outlet 606 of bottom plate 600 and return heating-water inlet 506 of top plate 500 with each other. Likewise, the direction of the flow of hot/cold-water can be inversed by changing cold-water inlet 604 of bottom plate 600 and hot-water outlet of top plate 500 with each other in terms of their function. Therefore, according to the stacked-up type heat exchanger for a hot-water storage type gas boiler constructed as above, a hot-water pipe is provided by stacking up and simply welding plates without installing a separate pipe by hard welding. Accordingly, the assembling is easily achieved and the thermal efficiency is improved as well. Thus the size of a heat exchanger can be smaller and the manufacturing cost is effectively reduced.

Claims: A heat exchanger comprising a plurality of plates (100, 200, 300, 400, 500, 600) stacked one above the other and providing one or more gas flues for passage of exhaust gas, a first passageway for water to be heated, and a second passageway for heating-water, the passageways and the flue or flues being formed by cooperating portions of the plates, and wherein one or more gas flues extend upwardly through the stack with each said gas flue being defined by a respective combustion gas flue (102, 202, 302, 402, 502, 602) from each of said plates (100, 200, 300, 400, 500, 600), characterised in that the plates (100, 200, 300, 400, 500, 600) from which the stack is made have a number of different configurations, in that cooperating portions (108, 106, 206, 308, 306, 406, 408) of the plates together define said first passageway (108, 702, 704, 308, 408) for the flow of water to be heated, the first passageway extending from a cold water inlet (604) or a hot water outlet in the bottom one of the stacked plates to the hot water outlet (504) or the cold water inlet in the top one of the stacked plates, and the first passageway spiralling around said gas flues, and in that said second passageway for heating-water is defined by spaces between adjacent ones of the plates interconnected by heating-water inlets (104, 204, 304, 404) in selected ones (100, 200, 300, 400) of the plates, said second passageway communicating with a heating-water inlet or outlet (606) in the bottom plate (600) and a heating-water outlet or inlet (506) in the top plate. A heat exchanger as claimed in Claim 1, wherein said stacked plates comprise a bottom plate (600), a first plate (100), a fourth plate (400) and a top plate (500), and wherein the first plate (100) has one or more said heating-water inlets (104), and a downwardly extending curved portion (106) arranged to define, with an upwardly extending curved portion (406) of said fourth plate, said first passageway for the flow of water to be heated, said first passageway (108, 702, 704, 408) being substantially ring-shaped and having a radius from the centre of the first and fourth plates, and the fourth plate (400) also having one or more said water-heating inlets (404). A heat exchanger as claimed in Claim 1, wherein said stacked plates comprise a bottom plate (600), first to fourth plates (100, 200, 300, 400), and a top plate (500), and wherein each of the first to fourth plates (100, 200, 300, 400) has one or more of said water-heating inlets (104, 204, 304, 404), the first and third plates (100, 300) each having a downwardly extending curved portion (106, 306), and the second and fourth plates (200, 400) each having an upwardly extending curved portion (206, 406), each downwardly extending curved portion (106, 306) cooperating with a respective upwardly extending curved portion (206, 406) of the adjacent plate to thereby define said first passageway (108, 702, 704, 308, 408) for the flow of water to be heated, said first passageway being substantially ring-shaped and having a radius from the centre of said first to fourth plates (100, 200, 300, 400). A heat exchanger as claimed in Claim 2 or Claim 3, further comprising two or more combined sets of stacked plates interposed between said bottom plate (600) and said top plate (500), each said stacked set of plates comprising a first plate (100), a second plate (200), a third plate (300) and a fourth plate (400). A heat exchanger as claimed in any preceding claim, wherein at an end of each of the combustion gas flues (102, 202, 302, 402, 502, 602), a baffle (107, 207, 307, 407, 507, 607) for delaying the flow of exhaust gas is provided. A heat exchanger as claimed in any preceding claim, wherein the bottom plate (600) has the heating-water inlet (606), and the top plate (500) has the heating-water outlet (506). A heat exchanger as claimed in any preceding claim, wherein the bottom plate (600) has the hot-water outlet (604), and the top plate (500) has the cold-water inlet (504).

Inventors: HONG WOONG-SUB, HONG, WOONG-SUB
Applicants: DAEWOO ELECTRONICS CO LTD, DAEWOO ELECTRONICS CO., LTD
Application year: 1995
Main classification: F24H1
IPC codes: F24H1, F28D9, F28F3