JP2016121817A - Water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water heater enabling removal of scale adhered to inside of a heat transfer pipe to be executed easily, enabling reduction of frequency of maintenance for removing the scale or having other functions.SOLUTION: A water heater is used for heating hot water supplied to a heat exchange section 4 by using combustion gas generated in a combustion section. The heat exchange section 4 includes: a heat transfer pipe 25 for making hot water flow; and a turbulent flow generation member 31 fitted to inside of the heat transfer pipe 25 to make the flowing hot water to promote generation of a turbulent flow. All or part of the turbulent flow generation member 31 comprises a shape memory alloy member 32 extended/contracted in the flowing direction of the hot water in the heat transfer pipe 25 caused by a temperature change of the heat exchange section 4, and the shape memory alloy member 32 comprises a coil-shaped wire having an outer diameter equal to an inner diameter of the heat transfer pipe 25.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a hot water supply apparatus, and more particularly to a hot water supply apparatus equipped with a turbulent flow generating member for generating a turbulent flow in a heat transfer tube of a heat exchanger.

  Conventionally, various hot water supply apparatuses according to heat sources such as a gas hot water supply apparatus, an electric hot water supply apparatus, and an oil hot water supply apparatus have been widely used in general households. In particular, the gas hot water supply device generates heat between a blower fan that takes in combustion air from the outside, a burner unit that mixes and burns combustion air and fuel gas, and high-temperature combustion gas and water flowing through a heat transfer tube. It has a heat exchanger that exchanges and heats the water, and an exhaust pipe and the like for discharging the exhaust gas after the heat exchange to the outside.

  As the heat exchanger, a fin-and-tube heat exchanger composed of a heat transfer tube for circulating hot water and a plurality of fins fixed to the heat transfer tube so as to transfer heat is generally applied. Heat pipes and fins made of a copper material are widely used.

  Moreover, in the above heat exchanger, for example, as described in the heat exchanger of Patent Document 1, a turbulent coil is mounted inside the heat transfer tube, and the hot water flowing through the heat transfer tube is circulated by the turbulent coil. On the other hand, a technique for preventing the occurrence of local boiling or boiling noise by promoting the generation of turbulent flow and improving the heat exchange efficiency of the heat exchanger is generally known.

Japanese Patent Laid-Open No. 10-185327

  By the way, when using tap water (hard water) having high hardness with respect to the tap water supplied to the hot water supply apparatus, calcium ions, magnesium, etc. contained in the tap water are combined with carbonate ions, sulfate ions, etc. As a result, a scale (cane stone) is formed, and this scale adheres to the inside of the heat transfer tube of the heat exchanger, so that there is a problem that the heat exchange efficiency gradually deteriorates.

  Furthermore, if the use of the hot water supply device is continued in a state where scale clogging has occurred, the heat exchanger may be damaged. For this reason, when scale clogging occurs, it is necessary to perform maintenance to remove the scale, but in hard water areas, scale clogging occurs due to short-term use, so the frequency of maintenance increases. As a result, there is a problem that the maintenance cost increases.

  An object of the present invention is to provide a hot water supply device that can easily remove scales adhering to the inside of a heat transfer tube, can reduce the frequency of maintenance for scale removal, and the like.

  The hot water supply apparatus according to claim 1 is a hot water supply apparatus that heats hot water supplied to the heat exchange section with combustion gas generated in the combustion section, wherein the heat exchange section includes a heat transfer tube for circulating hot water, In the hot water supply apparatus provided with a turbulent flow generating member for promoting the generation of turbulent flow with respect to the hot and cold water that is mounted and circulated inside the heat transfer tube, all or part of the turbulent flow generating member is the heat exchange It is characterized by comprising a member made of a shape memory alloy that expands and contracts in the flowing direction of the hot water in the heat transfer tube due to the temperature change of the part.

  According to a second aspect of the present invention, there is provided the hot water supply apparatus according to the first aspect, wherein the shape memory alloy member is made of a coiled wire having an outer diameter equal to the inner diameter of the heat transfer tube.

  According to a third aspect of the present invention, there is provided the hot water supply apparatus according to the first or second aspect, wherein the member made of the shape memory alloy is disposed directly above the combustion portion that always burns during combustion inside the heat transfer tube. .

  According to the first aspect of the present invention, all or a part of the turbulent flow generating member is constituted by a member made of a shape memory alloy that expands and contracts in the flowing direction of the hot water in the heat transfer tube due to the temperature change of the heat exchange section. The shape memory alloy member automatically expands and contracts due to temperature changes during hot-water heating and when hot-water supply is stopped, thereby easily removing the scale adhering to the inside of the heat transfer tube and preventing scale build-up Can do.

  Therefore, even if a dedicated member for scale removal is not additionally provided in the hot water supply device, the turbulent flow of hot water can be achieved by changing the material of all or part of the existing turbulent flow generating member to a member made of shape memory alloy. Since the scale removal can be realized with the promotion, the low cost and simple structure can prevent the heat exchange efficiency from being lowered and the frequency of regular maintenance for the scale removal can be reduced. Can be reduced.

  According to the invention of claim 2, since the shape memory alloy member is made of a coiled wire having an outer diameter equal to the inner diameter of the heat transfer tube, the coiled wire expands and contracts along the inner wall portion of the heat transfer tube. Thereby, the scale adhering to the inner wall part of a heat exchanger tube can be removed reliably.

  According to the invention of claim 3, since the member made of shape memory alloy is arranged directly above the combustion portion that always burns during combustion inside the heat transfer tube, the heat transfer tube is highly likely to be clogged with scale. By removing the scale, it is possible to prevent scale clogging as much as possible.

It is a schematic block diagram of the hot water supply apparatus which concerns on the Example of this invention. It is a front view of a hot water supply apparatus. It is a longitudinal cross-sectional view of the lower side from the heat exchange part of a water heater. It is a cross-sectional view of the lower heat exchange region of the heat exchange unit. It is a principal part enlarged view of FIG. 4 at the time of a hot water supply stop. It is a principal part enlarged view of FIG. 4 at the time of a hot water supply driving | operation. It is a principal part expanded sectional view of the heat exchanger tube and turbulent flow generation member which concern on a 1st modification. It is a principal part expanded sectional view of the heat exchanger tube and turbulent flow generation member which concern on a 2nd modification. It is a fragmentary perspective view of a turbulent flow generation member. It is a fragmentary perspective view of the turbulent flow generation member concerning the 3rd modification. It is a fragmentary perspective view of the turbulent flow generation member concerning the 4th modification.

  Hereinafter, modes for carrying out the present invention will be described based on examples.

First, the whole structure of the hot water supply apparatus 1 of this invention is demonstrated.
As shown in FIGS. 1 to 4, the hot water supply device 1 is applied as a heat source device such as a hot water supply device or a heating device, and uses heat contained in combustion gas generated by burning fuel gas. The gas water heater which heats water or hot water is comprised.

  That is, the hot water supply device 1 includes a blower fan 2 for supplying combustion air, a combustion unit 3 for burning fuel gas, and a heat exchange unit 4 for exchanging heat between the combustion gas and water by the combustion unit 3. And an exhaust cylinder 5 for discharging the exhaust gas after heat exchange by the heat exchanging unit 4, a control unit (not shown) for driving and controlling various pipes such as a water inlet pipe 6a and a hot water outlet pipe 6b, and various devices. Yes.

  The combustion unit 3 includes a burner unit 11 that mixes and burns fuel gas supplied from a fuel supply pipe (not shown) and combustion air supplied from the blower fan 2, and a burner can containing the burner unit 11. A body 12 and a combustion space 13 above the burner unit 11 in the burner can body 12 are provided. The burner can body 12 is configured in a rectangular parallelepiped shape having an upper opening. A blower fan 2 is provided at the lower end of the burner can body 12.

  The burner unit 11 includes ten combustion pipes 14 arranged in parallel in the left-right direction, and is configured in a multistage system including a plurality of (for example, three) combustion stages 11a to 11c (FIGS. 1 and 1). 2, see FIG. Each of the combustion stages 11a to 11c includes, for example, five, two, and three combustion pipes 14, respectively, and is connected to a corresponding fuel supply pipe. Each of the combustion stages 11a to 11c can be independently controlled by the control unit, and the number of stages and the output of the combustion stages 11a to 11c that are operated by combustion according to various operations are adjusted.

  During the hot water supply operation, for example, a one-stage combustion stage in which only the two combustion tubes 14 in the central combustion stage 11b are combusted, and a two-stage combustion stage in which the five combustion tubes 14 in the center and right combustion stages 11b and 11c are combusted. The four-stage combustion stage includes the three-stage combustion stage for burning the seven combustion tubes 14 of the left and center combustion stages 11a and 11b, and the four-stage combustion stage for burning the ten combustion pipes 14 of all the combustion stages 11a to 11c. The combustion operation is performed by switching the combustion stage. The center combustion stage 11b corresponds to a combustion section that is always combusted during a hot water supply operation.

  The burner unit 11 includes ten combustion pipes 14 and is configured in a multistage system including three combustion stages 11a to 11c. However, the burner unit 11 is not particularly limited to this structure. The number of stages and the number of combustion tubes in each combustion stage can be changed as appropriate, and the combustion stage that is always combusted during the hot water supply operation can also be changed as appropriate.

  As shown in FIGS. 2 and 3, an igniter 15 and a frame rod 16 are respectively arranged in the combustion space 13 above the combustion stage 11 b of the burner unit 11. The igniter 15 and the frame rod 16 are respectively attached to the right side portion (portion corresponding to the combustion stage 11b) of the center portion of the front side plate 12a of the burner can body 12 in the left-right direction. The frame rod 16 is attached adjacent to the right side of the igniter 15.

  The igniter 15 generates an ignition spark with an ignition target provided in the burner unit 11, thereby generating a flame in the fuel-air mixture ejected from the burner unit 11. It is attached so that it may protrude to diagonally downward.

  The flame rod 16 applies a voltage between the flames generated in the burner unit 11, and detects the current flowing from the flame rod 16 to the flame using the conductivity and rectification action due to the ionization of the flame. It is for detecting the presence or absence, and is attached so as to extend into the combustion space 13.

  As shown in FIGS. 1 to 4, the heat exchange unit 4 includes a heat exchanger 21 that recovers the heat of the combustion gas, a heat exchanger can body 22 that accommodates the heat exchanger 21, and the like. An exhaust tube 5 having an exhaust port 5a opened forward is provided at the upper end of the heat exchanger can body 22. The heat exchanger can body 22 is configured in a rectangular frame shape in plan view. The lower end portion of the heat exchanger can body 22 and the upper end portion of the burner can body 12 are joined by caulking or screw fastening. A thermal fuse 23 is provided around the heat exchanger can body 22 (see FIGS. 2 and 3).

  The heat exchanger 21 constitutes a fin-and-tube heat exchanger including a heat transfer tube 25 for circulating hot water and a plurality of fins 26 and the like fixed to the heat transfer tube 25 so that heat can be transferred. The heat transfer tubes 25 and the fins 26 are made of copper, but are not particularly limited to this material, and may be made of stainless steel.

  As shown in FIGS. 1 and 3, in the heat exchanger can body 22, the heat exchanger 21 includes an upper heat exchange region 21 </ b> A connected to the lower end of the exhaust pipe 5 (downstream side of the combustion gas flow) and the upper heat exchange region 21 </ b> A. , A two-stage structure including a lower heat exchange region 21B connected to the upper end of the combustion space 13 (the upstream side of the combustion gas flow).

  The heat transfer tube 25 includes a plurality of straight tube portions 27 arranged in parallel over two stages, and a plurality of connection tube portions 28 that connect ends of the plurality of straight tube portions 27. . Four straight pipe portions 27 are disposed in the upper heat exchange region 21A, and four straight tube portions 27 are disposed in the lower heat exchange region 21B. In each of the upper heat exchange region 21A and the lower heat exchange region 21B, The heat transfer tubes 25 are each configured in a meandering shape in plan view (see FIG. 4).

  The downstream end of the inlet pipe 6a is connected to the upstream (rear) straight pipe portion 27a of the lower heat exchange area 21B, and the downstream (front) straight pipe section 27b of the lower heat exchange area 21B is connected to the upper stage. The straight pipe portion 27c on the upstream side (front side) of the heat exchange region 21A is connected via the connecting pipe portion 28, and the straight pipe portion 27d on the downstream side (rear side) of the upper heat exchange region 21A is located upstream of the outlet pipe 6b. Connected to the side edge.

Next, the turbulent flow generating members 30 and 31 related to the present invention will be described.
As shown in FIGS. 4 to 6, the heat exchanging unit 4 includes a plurality of turbulent flow generating members 30, 31 that are attached to the inside of the heat transfer tube 25 and promote the generation of turbulent flow with respect to the flowing hot water. I have. A plurality of turbulent flow generating members 30 are attached to the plurality of straight pipe portions 27 in the upper heat exchange region 21A, and a plurality of turbulent flow generating members 31 are attached to the plurality of straight pipe portions 27 in the lower heat exchange region 21B. The plurality of turbulent flow generating members 30 and 31 are mounted so as to be in contact with the inner peripheral surface of the straight pipe portion 27.

  The turbulent flow generating member 30 and the turbulent flow generating member 31 are turbulent coils having the same shape. The total length of the turbulent flow generating members 30 and 31 is set to be approximately the same as the total length of the straight pipe portion 27. The coil diameters of the turbulent flow generating members 30 and 31 are respectively set to about 14 to 16 mm, but are not particularly limited to this size, and can be appropriately changed according to the inner diameter of the straight pipe portion 27.

  As described above, since the turbulent flow generating members 30 and 31 are attached to all the straight pipe portions 27 of the heat transfer tubes 25, a plurality of straight pipe portions 27 are caused by the stirring action of the turbulent flow generating members 30 and 31. By intentionally disturbing each water flow, the turbulent flow is promoted, and the heat in the vicinity of the wall surface of each of the plurality of straight pipe portions 27 is diffused to make the temperature uniform, thereby preventing local boiling as much as possible. Can do.

Next, materials for the turbulent flow generation members 30 and 31 will be described.
The plurality of turbulent flow generating members 30 in the upper heat exchange region 21A are each formed from a coil-shaped stainless steel wire having an outer diameter equal to the inner diameter of the straight pipe portion 27, but it is particularly necessary to limit the material to stainless steel. There is no change and can be changed as appropriate. On the other hand, the plurality of turbulent flow generating members 31 in the lower heat exchange region 21B are integrally formed from a plurality of materials, respectively.

  That is, each turbulent flow generating member 31 is formed of a shape memory alloy member 32 constituting the right side portion of the center portion and stainless steel members 33 and 34 constituting the left and right side portions thereof. The stainless steel members 33 and 34 are each formed from a coiled wire having an outer diameter equal to the inner diameter of the straight pipe portion 27. The members 33 and 34 made of stainless steel are not particularly limited to stainless steel, and can be appropriately changed. The left and right ends of the shape memory alloy member 32 are welded to the end portions of the stainless members 33 and 34, respectively.

Next, the shape memory alloy member 32 related to the present invention will be described.
As shown in FIGS. 4 to 6, the shape memory alloy member 32 constitutes a part of the turbulent flow generating member 31 and has a coil-shaped wire having an outer diameter equal to the inner diameter of the straight pipe portion 27. Formed from. The shape memory alloy member 32 is disposed directly above the combustion portion (the central combustion stage 11 b) that always burns during combustion inside the heat transfer tube 25. That is, the shape memory alloy members 32 are respectively attached to the passage portions 27e located immediately above the combustion stage 11b in the plurality of straight pipe portions 27 in the lower heat exchange region 21B.

  The shape memory alloy member 32 expands and contracts in the flowing direction of the hot water in the heat transfer tube 25 due to the temperature change of the heat exchange section 4. The shape memory alloy member 32 of this embodiment is preferably one whose shape is restored in a region where the hot water temperature is higher than a predetermined temperature (for example, 60 ° C.). That is, the shape memory alloy member 32 of the present embodiment is subjected to shape memory processing in an expanded state when the hot water temperature is equal to or higher than a predetermined temperature.

  Specifically, when the hot water temperature rises to a predetermined temperature (for example, 60 ° C.) or higher during the hot water supply operation, the shape memory alloy member 32 has an original memorized shape (extended state) as shown in FIG. Returning to FIG. 5, when the hot water temperature decreases when hot water supply is stopped, as shown in FIG. 5, the shape is released from the shape memory (contracted state). The shape memory alloy member 32 is set to a length of about 15 to 30% of the total length of the turbulent flow generation member 31 so as to correspond to the left and right width of the combustion stage 11 b of the burner unit 11. The shape memory alloy member 32 is elongated by, for example, about 10% when the hot water temperature becomes a predetermined temperature or higher during the hot water supply operation.

  As a material of the member 32 made of a shape memory alloy, a Ti-based alloy (Ti-Ni alloy, Ti-Ni-Cu alloy, etc.), an iron-based shape memory alloy, a zinc-based shape memory alloy, or the like can be selected. Among the materials, Ti-based alloys (especially Ti-Ni-Cu alloys) are desirable, but there is no need to specifically limit them, and materials and element ratios are appropriately changed according to the required transformation temperature, durability, etc. Is possible.

Next, the operation and effect of the hot water supply apparatus 1 of the present invention will be described.
During the hot water supply operation, fuel gas is supplied to the burner unit 11 from the fuel supply pipe and combustion air is supplied from the blower fan 2. The fuel gas is mixed with the air and burned, and the combustion heat (combustion gas) of the flame The water in the heat exchanger 21 is heated, and then the exhaust is discharged to the outside through the exhaust tube 5 from the exhaust port.

  On the other hand, in the heat exchanger 21, when water is supplied to the water intake pipe 6a from an external water source, this water first flows through the heat transfer pipe 25 in the lower heat exchange region 21B of the heat exchanger 21, and then. The heat exchanger 21 flows through the heat transfer pipe 25 in the upper heat exchange region 21A, and as described above, water is heated in the heat exchanger 21 to become high-temperature water, and is discharged from the hot water discharge pipe 6b to the outside.

  By the way, during the hot water supply operation, as described above, the burner unit 11 of the combustion unit 3 is operated for combustion by adjusting the combustion stage in four stages according to the required amount of heat. The combustion tube 14 can be burned with the minimum amount of combustion, and is always burned during the hot water supply operation.

  For this reason, since the passage part 27e located immediately above the combustion stage 11b of the plurality of straight pipe parts 27 in the lower heat exchange region 21B is constantly burned by the flames of the two combustion pipes 14 of the combustion stage 11b, The temperature of hot and cold water flowing through the passage portion 27e is likely to be higher than that of other passage portions, local boiling is likely to occur, and there is a tendency that scale is likely to accumulate as compared with other passage portions.

  Therefore, a portion of the turbulent flow generating member 31 that is attached to the passage portion 27e of the straight pipe portion 27 that has the possibility of local boiling is constituted by a shape memory alloy member 32, and when the hot water temperature rises, By extending the shape memory alloy member 32 and contracting the shape memory alloy member 32 when the hot water temperature decreases, the scale attached to the passage portion 27e can be removed. In addition, the scale can be removed over the entire length of the straight pipe portion 27 by expanding and contracting the entire length of the turbulent flow generating member 31 through the expanding and contracting operation of the member 32 made of shape memory alloy.

  As described above, a part of the turbulent flow generating member 31 is configured by the shape memory alloy member 32 that expands and contracts in the flowing direction of the hot water in the heat transfer tube 25 due to the temperature change of the heat exchange unit 4. The shape memory alloy member 32 automatically expands and contracts due to temperature changes during hot water supply heating and when hot water supply is stopped, thereby easily removing the scale attached to the inside of the heat transfer tube 25 and preventing scale accumulation. be able to.

  Therefore, even if a dedicated member for removing the scale is not additionally provided in the hot water supply device 1, the turbulent flow of the hot water is changed by changing a part of the material of the existing turbulent flow generating member 31 to the member 32 made of shape memory alloy. Since the scale removal can be realized with the flow promotion, the low cost and simple structure can prevent the heat exchange efficiency from decreasing and the frequency of regular maintenance for the scale removal can be reduced. Can be reduced.

  Further, since the shape memory alloy member 32 is made of a coiled wire having an outer diameter equal to the inner diameter of the heat transfer tube 25, the coiled wire expands and contracts along the inner wall portion of the heat transfer tube 25. The scale adhering to the inner wall portion of the heat tube 25 can be reliably removed.

  Furthermore, since the shape memory alloy member 32 is disposed directly above the combustion section (the central combustion stage 11b) that always burns during combustion inside the heat transfer tube 25, there is a possibility that scale clogging of the heat transfer tube 25 may occur. By removing the scale at a high point, scale clogging can be prevented as much as possible.

Next, a mode in which the above embodiment is partially changed will be described.
[1] In the above-described embodiment, a part of the turbulent flow generating member 31 is configured by the shape memory alloy member 32. You may comprise with the member made from a shape memory alloy which expands-contracts in the flow direction of the hot water in the straight pipe part 27 of the heat pipe 25. FIG.

[2] In the above-described embodiment, the turbulent flow generating member 31 which is partly formed by the shape memory alloy member 32 is attached only to the plurality of straight pipe portions 27 in the lower heat exchange region 21B. It is not necessary to limit to the structure, and similarly, the turbulent flow generating members 31 may be attached to the plurality of straight pipe portions 27 in the upper heat exchange region 21 </ b> A instead of the turbulent flow generating members 30. Further, the plurality of turbulent flow generating members 30 in the upper heat exchange region 21A may be omitted.

[3] In the above-described embodiment, the shape memory alloy member 32 is disposed immediately above the combustion portion that always burns during combustion. However, the shape memory alloy member 32 need not be limited to this position. It may be arranged at either one of the left and right end portions of the straight pipe portion 27, or may be arranged in another passage portion where the scale may be deposited, and can be changed as appropriate.

[4] In the above-described embodiment, the shape memory alloy member 32 expands when the hot water temperature rises and contracts when the hot water temperature decreases, but it is not particularly limited to this deformation. That is, as shown in FIG. 7, a part of the turbulent flow generating member 31A may be constituted by a shape memory alloy member 32A that contracts when the hot water temperature rises and expands when the hot water temperature decreases. The shape memory alloy member 32A is shortened by, for example, about 10% when the hot water temperature becomes a predetermined temperature (for example, 60 ° C.) or more during the hot water supply operation by performing a contraction operation.

[5] The turbulent flow generating member 31 of the above-described embodiment is configured as an integral part, but is not particularly limited to this structure, and may be configured separately. That is, as shown in FIGS. 8 and 9, a part of the turbulent flow generating member 31B is constituted by a member 32B made of a shape memory alloy similar to that of the above-described embodiment, and the member 32B made of the shape memory alloy is sandwiched. The left and right side portions may be formed of stainless steel members 33B and 34B (baffle plates) having a plurality of cut and raised pieces 35 formed by cutting and raising the belt-like stainless steel material alternately at predetermined intervals.

[6] The shape memory alloy member 32 of the above embodiment is made of a coiled wire, but is not particularly limited to this structure. As shown in FIG. A shape memory alloy member 32C made of the above-mentioned wire rod and a stainless steel turbulent coil 36 to which the shape memory alloy member 32C is fixed may be used. The shape memory alloy member 32C constitutes a part of the turbulent flow generation member 31C. When the shape memory alloy member 32C expands and contracts due to a temperature change, the turbulent coil 36 also expands and contracts, and the entire length of the turbulent flow generating member 31C expands and contracts.

[7] The shape memory alloy member 32 of the above embodiment is formed in a coil shape wound in the same direction, but it is not particularly limited to this structure. As shown in FIG. All or part of the member 31D may be configured by a shape memory alloy member 32D made of a single wire in which C-shaped curved portions are alternately formed at predetermined intervals.

[8] In addition, those skilled in the art can implement the present invention by adding various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. It is.

DESCRIPTION OF SYMBOLS 1 Hot-water supply apparatus 3 Combustion part 4 Heat exchange part 25 Heat-transfer tube 31, 31A-31D Turbulent flow generation member 32, 32A-32D Shape memory alloy member

Claims (3)

A hot water supply apparatus for heating hot water supplied to a heat exchanging section with combustion gas generated in a combustion section, wherein the heat exchanging section is attached to a heat transfer pipe for circulating hot water and an inside of the heat transfer pipe, and In a hot water supply apparatus provided with a turbulent flow generating member for promoting the generation of turbulent flow with respect to circulating hot water,
All or a part of the turbulent flow generating member is formed of a shape memory alloy member that expands and contracts in the flowing direction of the hot water in the heat transfer tube due to a temperature change of the heat exchange section. .   The hot water supply apparatus according to claim 1, wherein the shape memory alloy member is formed of a coiled wire having an outer diameter equal to an inner diameter of the heat transfer tube.   3. The hot water supply apparatus according to claim 1, wherein the shape memory alloy member is disposed directly above a combustion portion that always burns during combustion inside the heat transfer tube. 4.