Heat exchanger and water heating apparatus

A heat exchanger including a gas inlet through which a combustion gas flows in and a gas outlet through which the combustion gas flows out is provided. The heat exchanger includes a housing in which the gas outlet is formed, a partition member, and a plurality of heat transfer tubes accommodated in the housing. The partition member is mounted in the housing so that there is a portion in which a flow area of the combustion gas is smaller than that of the gas inlet between the gas inlet and the gas outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Japanese Patent Application No. 2019-232566, filed on Dec. 24, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The present disclosure relates to a heat exchanger and a water heating apparatus.

Description of Related Art

Japanese Patent Laid-Open No. 2019-113280 describes a heat exchanger. The heat exchanger described in Japanese Patent Laid-Open No. 2019-113280 includes a housing and a heat transfer tube. The housing includes a first side wall, a second side wall, a third side wall, and a fourth side wall. The housing includes an upper opening defined by upper ends of the first side wall, the second side wall, the third side wall and the fourth side wall, and a lower opening defined by lower ends of the first side wall, the second side wall, the third side wall and the fourth side wall. In the heat exchanger described in Japanese Patent Laid-Open No. 2019-113280, the upper opening serves as a gas inlet which allows combustion gas to flow in, and the lower opening serves as a gas outlet which allows the combustion gas to flow out. The heat transfer tube is accommodated inside the housing. A temperature of water flowing through the heat transfer tube is raised by exchanging heat with the combustion gas.

A temperature of the combustion gas flowing inside the housing decreases as the combustion gas approaches the gas outlet. As a result, a volume and a flow velocity of the combustion gas flowing inside the housing decrease as the combustion gas approaches the gas outlet. The decrease in the flow velocity of the combustion gas flowing inside the housing leads to a decrease in efficiency of heat exchange with the water flowing through the heat transfer tube. As described above, the heat exchanger described in Japanese Patent Laid-Open No. 2019-113280 has room for improvement in the efficiency of heat exchange.

SUMMARY

The present disclosure has been made in view of the above-described problems of the related art. More specifically, the present disclosure provides a heat exchanger and a water heating apparatus with improved efficiency in heat exchange.

A heat exchanger according to a first aspect of the present disclosure is a heat exchanger including a gas inlet through which a combustion gas flows in, and a gas outlet through which the combustion gas flows out. The heat exchanger includes a housing in which the gas outlet is formed, a partition member, and a plurality of heat transfer tubes accommodated in the housing. The partition member is mounted in the housing so that there is a portion in which a flow area of the combustion gas is smaller than that of the gas inlet between the gas inlet and the gas outlet. The plurality of heat transfer tubes may meander in a plane intersecting a first direction and may be disposed to overlap each other in the first direction. The housing may include a first side wall, a second side wall, a third side wall, a fourth side wall, and a bottom wall. The first side wall and the second side wall may face each other in the first direction. The third side wall and the fourth side wall may face each other in a second direction intersecting the first direction. The gas outlet may be formed in the first side wall. The housing may have an opening defined by the first side wall, the second side wall, the third side wall and the fourth side wall. The partition member may include a first portion configured to define the gas inlet by closing a part of the opening, and a second portion configured to extend from the first portion toward the bottom wall in a plane intersecting the first direction.

The heat exchanger may further include a first header, a second header and a third header mounted on the third side wall. A water inlet may be formed in the first header. A water outlet may be formed in the second header. Each of the plurality of heat transfer tubes may include a first end portion, and a second end portion closer to the opening than to the first end portion in a third direction intersecting the first direction and the second direction. The second end portion of each of the plurality of heat transfer tubes between the second portion and the first side wall may be connected to the first header. The second end portion of each of the plurality of heat transfer tubes between the second portion and the second side wall may be connected to the second header. The first end portion of each of the plurality of heat transfer tubes may be connected to the third header.

A heat exchanger according to a second aspect of the present disclosure is a heat exchanger including a gas inlet through which a combustion gas flows in, and a gas outlet through which the combustion gas flows out. The heat exchanger includes a housing in which the gas outlet is formed, a partition member, and a plurality of heat transfer tubes accommodated in the housing. The heat exchanger may further include a plurality of heat transfer tubes accommodated in the housing. The plurality of heat transfer tubes may meander in a plane intersecting a first direction and may be disposed to overlap each other in the first direction. The housing may include a first side wall, a second side wall, a third side wall, and a fourth side wall. The first side wall and the second side wall may face each other in the first direction. The third side wall and the fourth side wall may face each other in a second direction intersecting the first direction. The gas outlet may be formed in the first side wall. The housing may have an opening defined by the first side wall, the second side wall, the third side wall and the fourth side wall and configured to serve as the gas inlet. The partition member may be closer to the gas inlet than to the gas outlet in a third direction intersecting the first direction and the second direction. The partition member may extend from one of the first side wall and the second side wall toward the other one of the first side wall and the second side wall in a plane intersecting the third direction.

A water heating apparatus according to an aspect of the present disclosure includes the above heat exchanger, a burner, and a duct. The burner produces combustion gas. The duct is connected to the gas outlet.

The above and other objectives, features, aspects and advantages of the disclosure will become apparent from the following detailed description of the disclosure as understood in connection with the accompanying drawings.

DESCRIPTION OF THE EMBODIMENTS

Details of embodiments will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be designated by the same reference numerals, and the duplicated description will not be repeated.

First Embodiment

A water heating apparatus (hereinafter, referred to as “water heating apparatus100”) according to a first embodiment will be described below.

<Schematic Configuration of Water Heating Apparatus100>

FIG. 1is a schematic view of the water heating apparatus100. As shown inFIG. 1, the water heating apparatus100includes a gas valve10, an orifice11, a venturi12, a blower13, a chamber14, a burner15, a spark plug16, a primary heat exchanger20, a secondary heat exchanger30, a duct40, a pipe.50, a pipe60, a pipe70, and a bypass pipe80. A detailed configuration of the secondary heat exchanger30will be described later.

Fuel gas is supplied to the venturi12through the orifice11by opening the gas valve10. The fuel gas supplied to the venturi12is mixed with air in the venturi12(hereinafter, the fuel gas mixed with air is referred to as a mixed gas). The mixed gas is supplied to the burner15through the chamber14by the blower13. The mixed gas supplied to the burner15is ignited and burned by sparking the spark plug16. Thus, combustion gas is generated in the burner15.

One end of the pipe50is connected to a water supply. The other end of the pipe50is connected to a water inlet30aof the secondary heat exchanger30. One end of the pipe60is connected to a water outlet30bof the secondary heat exchanger30. The other end of the pipe60is connected to a water inlet20aof the primary heat exchanger20. One end of the pipe70is connected to a water outlet20bof the primary heat exchanger20. The other end of the pipe70is connected to a hot water tap (not shown).

One end of the bypass pipe80is connected to the pipe50, and the other end thereof is connected to the pipe70. The bypass pipe80and the pipe70are connected by a three-way valve71. The duct40is connected to the secondary heat exchanger30.

Water supplied from one end of the pipe50flows through the pipe50and is supplied to the secondary heat exchanger30. A temperature of the water supplied to the secondary heat exchanger30is raised by exchanging heat with the combustion gas. The water flowing through the secondary heat exchanger30flows through the pipe60and is supplied to the primary heat exchanger20. A temperature of the water supplied to the primary heat exchanger20is raised by exchanging heat with the combustion gas. The water flowing through the primary heat exchanger20is supplied from the hot water tap through the pipe70. The combustion gas that has exchanged heat with the water flowing through the primary heat exchanger20and the secondary heat exchanger30is discharged to the outside from the duct40.

<Detailed Configuration of Secondary Heat Exchanger30in Water Heating Apparatus100>

FIG. 2is a plan view of the secondary heat exchanger30in the water heating apparatus100.FIG. 3is a cross-sectional view taken along line III-III ofFIG. 2.FIG. 4is an exploded perspective view of the secondary heat exchanger30in the water heating apparatus100.FIGS. 2 to 4also show the duct40. As shown inFIGS. 2 to 4, the secondary heat exchanger30includes a housing31, a plurality of heat transfer tubes32, a partition member33, a header34, and a header35.

The housing31has a side wall31a, a side wall31b, a side wall31c, a side wall31d, and a bottom wall31e. The side wall31aand the side wall31bface each other in a first direction DR1. The side wall31cand the side wall31dface each other in a second direction DR2. The second direction DR2is a direction that intersects the first direction DR1. The second direction DR2may be orthogonal to the first direction DR1.

A gas outlet30dis formed on the side wall31a. The combustion gas flows out from the gas outlet30d. The gas outlet30dpasses through the side wall31ain a thickness direction. The gas outlet30dis formed, for example, on the upper end side of the side wall31a. The duct40is connected to the gas outlet30d.

A plurality of through holes31caand a plurality of through holes31cbare formed in the side wall31c. The through holes31caand the through holes31cbpass through the side wall31cin the thickness direction. The through holes31caare arranged in two rows in the first direction DR1, and the through holes31cbare arranged in two rows along the first direction DR1. The through holes31caare located on the lower end side of the side wall31cfrom the through holes31cb. The number of through holes31caand the number of through holes31cbare equal to the number of heat transfer tubes32.

The housing31has an opening31f. The opening31fis defined by upper ends of the side walls31ato31d. The bottom wall31eis connected to lower ends of the side wall31ato the side wall31d. A direction from the opening31ftoward the bottom wall31efollows a third direction DR3. The third direction DR3is a direction that intersects the first direction DR1and the second direction DR2. The third direction DR3may be orthogonal to the first direction DR1and the second direction DR2.

The plurality of heat transfer tubes32is arranged to overlap each other in the first direction DR1. The heat transfer tubes32meander in a plane intersecting the first direction DR1. Each of the heat transfer tubes32has a first end portion32aand a second end portion32b. The first end portion32ais inserted through the through hole31ca, and the second end portion32bis inserted through the through hole31cb. From another point of view, the second end portion32bis closer to the opening31fthan to the first end portion32ain the third direction DR3. As described above, since the through holes31ca(the through holes31cb) are formed to be in two rows in the first direction DR1, the heat transfer tubes32overlap each other in the first direction DR1while being alternately displaced in the third direction DR3.

The partition member33is mounted in the housing31. The partition member33includes a first portion33aand a second portion33b. One end of the first portion33ain the first direction DR1is mounted near an upper end of the side wall31a. The first portion33aextends in the first direction DR1. A width of the first portion33ain the second direction DR2coincides with a width of the opening31fin the second direction DR2. Accordingly, the first portion33acloses a part of the opening31f. A portion of the opening31fthat is not closed by the first portion33aconstitutes the gas inlet30c. The combustion gas flows in from the gas inlet30c.

The second portion33bextends from one end thereof in the first direction DR1. The second portion33bextends toward the bottom wall31ein the plane intersecting the first direction DR1. That is, one side of a main surface of the second portion33bfaces the side wall31a, and the other side of the main surface thereof faces the side wall31b. The second portion33bpasses between two adjacent heat transfer tubes32in the first direction DR1.

There is a gap between a lower end of the second portion33b(an end opposite to the first portion33a) and the bottom wall31e. The combustion gas can pass through the gap. A flow area of the combustion gas in the gap between the second portion33band the bottom wall31eis smaller than a flow area of the combustion gas at the gas inlet30c.

An internal space of the housing31from the gas inlet30cto the gap between the lower end of the second portion33band the bottom wall31eserves as a first flow path. An internal space of the housing31from the gap between the lower end of the second portion33band the bottom wall31eto the gas outlet30dserves as a second flow path. A flow area of the combustion gas in the second flow path is smaller than a flow area of the combustion gas in the first flow path.

A distance between the second portion33band the side wall31ain the first direction DR1is shorter than a distance between the second portion33band the side wall31bin the first direction DR1. As a result, the number of heat transfer tubes32between the second portion33band the side wall31ais smaller than the number of heat transfer tubes32between the second portion33band the side wall31b. From another point of view, a total heat transfer area of the heat transfer tubes32in the second flow path is smaller than a total heat transfer area of the heat transfer tubes32in the first flow path.

The header34and the header35are mounted on an outer wall surface of the side wall31c. The inside of each of the header34and the header35is hollow. The header34is connected to the first end portion32a. The water inlet30ais formed in the header34. The water inlet30acommunicates with the inside of the header34. The water supplied from the water inlet30avia the pipe50is supplied to the heat transfer tube32via the header34.

The header35is connected to the second end portion32b. The water outlet30bis formed in the header35. The water outlet30bcommunicates with the inside of the header35. The water flowing through the heat transfer tube32is supplied to the pipe60from the water outlet30bvia the header35. The water supplied to the secondary heat exchanger30exchanges heat with the combustion gas while flowing through the heat transfer tube32.

<Effects of Secondary Heat Exchanger30in Water Heating Apparatus100>

A temperature of the combustion gas flowing inside the housing31decreases as it approaches the gas outlet30d. Since the volume of the combustion gas also decreases as the temperature of the combustion gas decreases, the flow velocity of the combustion gas decreases as it approaches the gas outlet30d. As a result, the efficiency of heat exchange between the combustion gas and the water flowing through the heat transfer tube32decreases on the gas outlet30dside.

However, in the secondary heat exchanger30, the partition member33is mounted in the housing31so that a portion in which the flow area of the combustion gas is smaller than that of the gas inlet30cis present between the gas inlet30cand the gas outlet30d. More specifically, in the secondary heat exchanger30, the flow area of the combustion gas in the gap between the lower end of the second portion33band the bottom wall31eis smaller than the flow area of the combustion gas at the gas inlet30c.

As a result, in the secondary heat exchanger30, the flow velocity of the combustion gas increases when passing through the gap between the lower end of the second portion33band the bottom wall31e. As described above, according to the secondary heat exchanger30, as a result of decrease in the flow velocity of the combustion gas on the gas outlet30dside being curbed, the efficiency of heat exchange between the combustion gas and the water flowing through the heat transfer tube32is improved.

When the partition member33is disposed so that the flow area of the combustion gas in the second flow path becomes smaller than the flow area of the combustion gas in the first flow path, the decrease in the flow velocity of the combustion gas in the gas outlet30dside is further curbed, and thus the efficiency of heat exchange between the combustion gas and the water flowing through the heat transfer tube32is further improved.

Second Embodiment

Hereinafter, a water heating apparatus (hereinafter, referred to as “water heating apparatus200”) according to a second embodiment will be described. Here, points different from the water heating apparatus100will be mainly described, without repeated duplicated description.

<Schematic Configuration of Water Heating Apparatus200>

The water heating apparatus200includes a gas valve10, an orifice11, a venturi12, a blower13, a chamber14, a burner15, a spark plug16, a primary heat exchanger20, a secondary heat exchanger30, a duct40, a pipe50, a pipe60, a pipe70, and a bypass pipe80. In this respect, the configuration of the water heating apparatus200is shared by the configuration of the water heating apparatus100. However, the configuration of the water heat apparatus200is different from the configuration of the water heating apparatus100in the detailed configuration of the secondary heat exchanger30.

<Detailed Configuration of Secondary Heat Exchanger30in Water Heating Apparatus200>

FIG. 5is a front view of the secondary heat exchanger30in the water heating apparatus200. InFIG. 5, positions at which the header36, the header37, and the header38are mounted are indicated by dotted lines. As shown inFIG. 5, in the water heating apparatus200, the secondary heat exchanger30has a header36, a header37, and a header38instead of the header34and the header35.

The header36is connected to the second end portion32bof the heat transfer tube32between the second portion33band the side wall31a. The header37is connected to the second end portion32bof the heat transfer tube32between the second portion33band the side wall31b. The header38is connected to the first end portions32aof all the heat transfer tubes32. The insides of the headers36to38are hollow.

Although not shown, a water inlet30ais formed in the header36. The water inlet30acommunicates with the inside of the header36. Although not shown, a water outlet30bis formed in the header37. The water outlet30bcommunicates with the inside of the header37.

The water supplied from the pipe50to the header36via the water inlet30aflows through the heat transfer tube32between the second portion33band the side wall31aand is supplied to the header38. The water supplied to the header38flows through the heat transfer tube32between the second portion33band the side wall31band is supplied to the header37. The water supplied to the header37is supplied to the pipe60via the water outlet30b.

<Effects of Secondary Heat Exchanger30in Water Heating Apparatus200>

In the heat exchanger, heat exchange with the combustion gas having a relatively low temperature is performed at a position at which the temperature of the water is relatively low, heat exchange with the combustion gas having a relatively high temperature is performed at a position at which the temperature of the water is relatively high, and thus the heat exchange becomes more efficient.

First, a temperature distribution of the combustion gas will be focused upon. The temperature of the combustion gas in a space between the second portion33band the side wall31b(hereinafter, referred to as a “first space”) is higher than the temperature of the combustion gas in a space between the second portion33band the side wall31a(hereinafter, referred to as a “second space”). The temperature of the combustion gas in the first space increases as a distance from the bottom wall31eincreases. The temperature of the combustion gas in the second space increases as it approaches the bottom wall31e.

Next, the order in which water flows will be focused upon. First, the water supplied to the header36flows through the heat transfer tube32in the second space to approach the bottom wall31eand is supplied to the header38. The water supplied to the header38flows through the heat transfer tube32in the first space away from the bottom wall31eand is supplied to the header37.

As described above, in the secondary heat exchanger30of the water heating apparatus200, since the heat exchange with the combustion gas having a relatively low temperature is performed at the position at which the temperature of the water is relatively low and the heat exchange with the combustion gas having a relatively high temperature is performed at a position at which the temperature of the water is relatively high, the efficiency of heat exchange between the combustion gas and the water flowing through the heat transfer tube32is further improved.

Third Embodiment

Hereinafter, a water heating apparatus (hereinafter, referred to as “water heating apparatus300”) according to a third embodiment will be described. Here, points different from the water heating apparatus100will be mainly described, without repeated duplicated description.

<Schematic Configuration of Water Heating Apparatus300>

The water heating apparatus300includes a gas valve10, an orifice11, a venturi12, a blower13, a chamber14, a burner15, a spark plug16, a primary heat exchanger20, a secondary heat exchanger30, a duct40, a pipe50, a pipe60, a pipe70, and a bypass pipe80. In this respect, the configuration of the water heating apparatus300is shared by the configuration of the water heating apparatus100. However, the configuration of the water heat apparatus300is different from the configuration of the water heating apparatus100in the detailed configuration of the secondary heat exchanger30.

<Detailed Configuration of Secondary Heat Exchanger30in Water Heating Apparatus300>

FIG. 6is a cross-sectional view of the secondary heat exchanger30in the water heating apparatus300.FIG. 6shows a cross-sectional view at a position corresponding to line III-III ofFIG. 2. As shown inFIG. 6, in the water heating apparatus300, the secondary heat exchanger30includes two partition members33(these are referred to as a partition member331and a partition member332). In the water heating apparatus300, the gas inlet30cis formed by the opening31f, and the gas outlet30dis formed on the lower end side of the side wall31a.

The partition member331has a flat plate shape. One end of the partition member331in the first direction DR1is mounted on the side wall31a. The partition member331extends from the side wall31atoward the side wall31bin a plane intersecting the third direction. There is a gap between the other end of the partition member331in the first direction DR1and the side wall31b. A flow area of the combustion gas in the gap is smaller than the flow area of the combustion gas at the gas inlet30c(the opening31f).

The partition member332has a flat plate shape. One end of the partition member332in the first direction DR1is mounted on the side wall31b. The partition member332extends from the side wall31btoward the side wall31ain the plane intersecting the third direction. There is a gap between the other end of the partition member332in the first direction DR1and the side wall31a. A flow area of the combustion gas in the gap is smaller than the flow area of the combustion gas at the gas inlet30c(the opening31f).

The partition member331and the partition member332are closer to the gas inlet30c(the opening31f) than to the gas outlet30din the third direction DR3. The partition member332is closer to the gas inlet30cthan to the partition member331in the third direction DR3. Accordingly, the combustion gas meanders and flows inside the housing31.

In the above, although the example in which the secondary heat exchanger30in the water heating apparatus300has the partition member331and the partition member332has been described, the secondary heat exchanger30in the water heating apparatus300may not have any one of the partition member331and the partition member332.

<Effects of Secondary Heat Exchanger30in Water Heating Apparatus300>

In the secondary heat exchanger30in the water heating apparatus300, there is a gap in which the flow area of the combustion gas is smaller than that of the gas inlet30cbetween the other end of the partition member331in the first direction DR1and the side wall31band between the other end of the partition member332in the first direction DR1and the side wall31a. Therefore, in the secondary heat exchanger30in the water heating apparatus300, similar to the secondary heat exchanger30in the water heating apparatus100, the efficiency of heat exchange between the combustion gas and the water flowing through the heat transfer tube32is improved.

Although the embodiments of the present disclosure have been described above, it is also possible to modify the above-described embodiments in various ways. Moreover, the scope of the present disclosure is not limited to the above-described embodiments. The scope of the present disclosure is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The above-described embodiments are particularly advantageously applied to a heat exchanger and a water heating apparatus having the heat exchanger.