JP7470280B2 - Heat exchanger and hot water device equipped with same - Google Patents

Description

The present invention relates to a type of heat exchanger that is used as a component of a hot water device such as a water heater and recovers heat from a heating medium such as combustion gas using a heat transfer tube, and to a hot water device equipped with the same.

An example of a heat exchanger is described in Patent Document 1.
In the heat exchanger described in the same document, a serpentine heat transfer tube is used as a heat transfer tube for recovering heat from combustion gas. The serpentine heat transfer tube has a configuration in which a plurality of straight tube sections are connected via a plurality of bent tube sections. In the above document, a plurality of heat transfer tubes are used as such a serpentine heat transfer tube, and these are stacked, for example, in the vertical direction. In addition, adjacent heat transfer tubes are arranged, for example, offset from each other in the horizontal direction, so that the combustion gas can easily act on each heat transfer tube.

On the other hand, the curved tube sections of each of the heat transfer tubes are flattened and made thinner than the straight tube sections. This allows adjacent heat transfer tubes to be placed closer to each other. As a result, it is possible to reduce the overall width of the multiple heat transfer tubes in the stacking direction, thereby making it possible to reduce the size of the entire heat exchanger.

However, the above-mentioned conventional technology still has room for improvement, as described below.

First, since each bent tube section of the serpentine heat transfer tube is formed into a flattened shape overall, there is a disadvantage in that the resistance (flow path resistance) when the fluid to be heated flows inside the heat transfer tube becomes large.
Secondly, the amount of machining required to flatten the entire bent tube section increases the residual stress, which is undesirable as it can cause stress cracks in the heat transfer tube. During use of the heat exchanger, the heat transfer tube may be subjected to large pressure due to, for example, the water hammer phenomenon, so it is desirable to minimize the residual stress.
Thirdly, as a means for flattening each curved tube portion of a serpentine heat transfer tube, for example, as shown in Fig. 13, a means for pressing the curved tube portion 21 of the heat transfer tube 2e in a direction intersecting the bending direction of the curved tube portion 21 is considered. However, when such a pressing is performed, a force is generated that tries to deform both ends of the curved tube portion 21 in a direction opening up, as shown by the arrow Na. In Patent Document 1, since the amount of pressing is large, the above-mentioned deformation is likely to occur, and there is a risk that the heat transfer tube 2e will differ from its original specifications.

Patent No. 4143431

The present invention was conceived in light of the above-mentioned circumstances, and aims to provide a heat exchanger that can eliminate problems such as high flow resistance in serpentine heat transfer tubes and the generation of a large amount of residual stress in the heat transfer tubes, while also enabling appropriate reduction in overall size, and a hot water device equipped with the same.

To solve the above problems, the present invention provides the following technical solutions:

The heat exchanger provided by the first aspect of the present invention has a serpentine shape in which a plurality of straight pipe sections extending in a predetermined x direction and arranged at intervals in a z direction intersecting the x direction are connected in series via a plurality of curved pipe sections, and is provided with a plurality of heat transfer tubes arranged in a layered manner in a y direction intersecting the x and z directions in an area where a heating medium flows, and these plurality of heat transfer tubes are adjacent to each other in the y direction, and the plurality of straight pipe sections are in a non-overlapping state when viewed in the y direction, and the plurality of curved pipe sections are arranged in a layered manner in an area where a heating medium flows, and the ... arranged in a layered manner in a y direction intersecting the x and z directions. A heat exchanger having first and second heat transfer tubes that are misaligned in the z direction so that they partially overlap each other, and at least the curved tube portion of the first heat transfer tube among the first and second heat transfer tubes has a first recess that partially reduces the thickness in the y direction at the portion that overlaps with the curved tube portion of the second heat transfer tube compared to the other portion of the curved tube portion, and a portion of the curved tube portion of the second heat transfer tube is fitted into this first recess.

According to this configuration, since a part of each curved tube portion of the second heat transfer tube is fitted into the first recess provided in each curved tube portion of at least the first heat transfer tube among the first and second serpentine heat transfer tubes adjacent to each other, the arrangement pitch of the first and second heat transfer tubes in the y direction can be reduced. As a result, the overall width of the multiple heat transfer tubes in the y direction can be reduced, and the size of the heat exchanger can be reduced. In addition to the above, the present invention further provides the following effects.
First, unlike Patent Document 1, the entire curved pipe section of the heat transfer tube is not formed flat, and only a first recess is partially provided in a part of the curved pipe section, thereby making it possible to reduce the resistance (flow path resistance) when the fluid to be heated flows inside the heat transfer tube.
Secondly, compared to the method of forming the entire bent pipe section into a flat shape as described in Patent Document 1, the processing for partially providing the first recess in the bent pipe section requires a smaller amount of processing and can reduce residual stress. Therefore, stress cracks are less likely to occur in the heat transfer tube, and the heat transfer tube can have sufficient durability against, for example, the water hammer phenomenon.
Thirdly, when the bent portion of the heat transfer tube is pressed to form the first recess, the amount of pressing can be reduced, which prevents the heat transfer tube from being significantly deformed in the direction in which both ends of the bent portion open, unlike the case described with reference to Fig. 13, and appropriately eliminates the risk of the heat transfer tube becoming different from its original specifications.

In the present invention, preferably, the first recesses are provided in pairs on both side portions of each of the curved tube portions of the first heat transfer tube that face each other in the y direction.

With this configuration, compared to providing a first recess on only one of the two predetermined side portions of each curved tube section, it is possible to reduce the depth of each first recess while reducing the arrangement pitch of the first and second heat transfer tubes in the y direction. If the depth of the first recess is increased, there is a risk that the residual stress resulting from the processing of this first recess will increase, but with the above configuration, it is possible to reduce the arrangement pitch of the heat transfer tubes while avoiding such a risk.

In the present invention, preferably, the first recess is provided on only one of the two side portions that face each other in the y direction of each of the curved tube portions of the first heat transfer tube.

This configuration simplifies the structure of the heat transfer tube compared to when a pair of first recesses are provided on both sides of each predetermined side surface of each curved tube section.

In the present invention, preferably, each of the curved pipe portions of the second heat transfer tube is provided with a second recess that partially reduces the thickness in the y direction compared to other parts of each of the curved pipe portions, and the formation locations of the first and second recesses are fitted together.

With this configuration, it is possible to reduce the arrangement pitch of the multiple heat transfer tubes in the y direction while reducing the depth of each of the first and second recesses. This is therefore even more preferable in terms of reducing residual stress caused by forming the first and second recesses. Furthermore, compared to a configuration in which only the first recess is provided, it is also possible to reduce the arrangement pitch of the multiple heat transfer tubes in the y direction, further promoting miniaturization of the heat exchanger.

In the present invention, preferably, the second heat transfer tube is a heat transfer tube having the same shape and size as the first heat transfer tube, but is turned upside down.

This configuration makes it possible to reduce the manufacturing costs of the heat exchanger compared to using first and second heat transfer tubes with different shapes and sizes.

The hot water device provided by the second aspect of the present invention is characterized by including the heat exchanger provided by the first aspect of the present invention.

With this configuration, the same effects as those described for the heat exchanger provided by the first aspect of the present invention can be obtained.

Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment of the invention, taken in conjunction with the accompanying drawings.

1 is a schematic perspective view showing an example of a heat exchanger according to the present invention. 2 shows a schematic configuration of a hot water device using the heat exchanger of FIG. 1, and the heat exchanger shown by the solid line in the figure corresponds to the cross-sectional view taken along line II-II in FIG. FIG. 2 is a cross-sectional view taken along line III-III of FIG. FIG. 4 is a perspective view showing heat transfer tubes (first and second heat transfer tubes) used in the heat exchanger shown in FIGS. 1 to 3. 5A is a front view of a main part of the heat transfer tube shown in FIG. 4, (b) is a cross-sectional view taken along line Vb-Vb of (a), (c) is a side view taken along line Vc of (a), (d) is a cross-sectional view taken along line Vd-Vd of (a), and (e) is a cross-sectional view taken along line Ve-Ve of (a). 6A is a front view of the essential parts of the heat transfer tubes shown in FIG. 5 in a stacked state, FIG. 6B is a cross-sectional view taken along line VIb-VIb of FIG. 5A, and FIG. 6C is a cross-sectional view taken along line VIc-VIc of FIG. FIG. 11 is a perspective view showing another example of the present invention. 8A is a front view of a main portion of the heat transfer tube shown in FIG. 7, FIG. 8B is a cross-sectional view taken along line VIIIb-VIIIb of FIG. 8A, and FIG. 8C is a cross-sectional view taken along line VIIIc-VIIIc of FIG. FIG. 11 is a perspective view showing another example of the present invention. 10A is a front view of a main portion of the heat transfer tube shown in FIG. 9, FIG. 10B is a cross-sectional view taken along the line Xb-Xb of FIG. 9A, and FIG. 10C is a cross-sectional view taken along the line Xc-Xc of FIG. FIG. 11 is a perspective view showing another example of the present invention. 12A is a front view of the main part of the heat transfer tube shown in FIG. 11, FIG. 12B is a cross-sectional view taken along line XIIb-XIIb of FIG. 12A, and FIG. 12C is a cross-sectional view taken along line XIIc-XIIc of FIG. FIG. 13 is an explanatory diagram showing the operation of the conventional technology.

The preferred embodiment of the present invention will be described in detail below with reference to the drawings.

A heat exchanger HE shown in FIGS. 1 to 3 includes a case 1, a plurality of serpentine heat transfer tubes 2, and a pair of water inlet and hot water outlet headers 7a, 7b.

The case 1 has a generally rectangular cylindrical or frame shape with an open top and bottom, and a heating medium is supplied into the inside of the case 1 .
2 shows a hot water device WH using a heat exchanger HE. In this hot water device WH, a burner 80 and another heat exchanger 81 are provided on the upper side of a case 1. The other heat exchanger 81 is a primary heat exchanger for recovering sensible heat, and the heat exchanger HE in this embodiment is a secondary heat exchanger for recovering latent heat. In the hot water device WH, the combustion gas (heating medium) generated by the burner 80 travels downward and passes through the heat exchangers 81 and HE in sequence, whereby sensible heat and latent heat are sequentially recovered from the combustion gas, and the recovered heat is used to heat hot water. This hot water is supplied to, for example, a hot water tap in a kitchen, a hot water tap in a bathroom, or a bathtub.

The plurality of heat transfer tubes 2 are made of a metal such as stainless steel, are serpentine heat transfer tubes, and are housed within the case 1 .
More specifically, as shown in FIG. 3 , each heat transfer tube 2 extends in the front-to-rear direction of the case 1 (an example of the x-direction in this invention) and has a serpentine shape in which a number of straight pipe sections 20 are arranged at intervals in the up-down height direction (an example of the z-direction in this invention) and are connected in series via a number of curved pipe sections 21 that are semicircular arc-shaped when viewed from the side.
Both ends of each heat transfer tube 2 penetrate the side wall 10 of the case 1 and are connected to headers 7a, 7b provided on the outer surface of the side wall 10. As a result, hot water supplied from the outside to the header 7a passes through each heat transfer tube 2, reaches the header 7b, and is discharged. In this process, the hot water is heated by the combustion gas.

The heat transfer tubes 2 are divided into first and second heat transfer tubes 2A and 2B, which are provided with first and second recesses 3A and 3B. This will be explained in more detail below.

The heat transfer tubes 2 are arranged in the width direction of the case 1 (the left-right direction in FIG. 2, which is an example of the y direction in the present invention), but adjacent heat transfer tubes 2 are offset in position by an appropriate dimension La in the vertical height direction. In this embodiment, the lower side is the first heat transfer tube 2A(2), and the higher side is the second heat transfer tube 2B(2). The first and second heat transfer tubes 2A, 2B are offset in position so that the straight tube sections 20 do not overlap each other in the vertical height direction. However, portions of the curved tube sections 21 overlap each other (the overlapping sections OV are shown by the symbols OV in FIG. 3).

As shown in FIG. 4, the first recesses 3A are provided at the positions of the curved pipe sections 21 of the first heat transfer tube 2A that correspond to the overlapping portions OV. As shown in FIG. 5, the first recesses 3A are offset from the center line CL of the curved pipe section 21, and are provided in pairs on the left and right sides of the curved pipe section 21 (sides facing in the y direction) facing each other. As a result, the width Lb of the curved pipe section 21 where the pair of first recesses 3A are formed is smaller than the width Lc of the other portions (corresponding to the outer diameter of the heat transfer tube 2). The first recesses 3A can be formed by applying partial press processing to the curved pipe section 21.

The second recesses 3B are provided at the positions of the curved pipe portions 21 of the second heat transfer tube 2B that correspond to the overlapping portions OV. Here, the second heat transfer tube 2B in this embodiment corresponds to a configuration in which the first heat transfer tube 2A is turned upside down. Therefore, the second recesses 3B are provided in pairs on the left and right sides of each curved pipe portion 21, facing each other, in the same manner as the first recesses 3A described above.
The first and second heat transfer tubes 2A, 2B are set in a state in which the formation locations of the first recesses 3A and the second recesses 3B are fitted together, i.e., the formation locations of the second recesses 3B are fitted into the first recesses 3A, and the formation locations of the first recesses 3A are fitted into the second recesses 3B) (see Figures 2 and 6).

Next, we will explain the operation of the heat exchanger HE.

First, as already described, in the overlapping portion OV of each curved tube portion 21 of the first and second heat transfer tubes 2A, 2B, the portions where the first and second recesses 3A, 3B, which have a reduced width, are formed fit together. Therefore, it is possible to arrange the straight tube portions 20 of the first and second heat transfer tubes 2A, 2B so that they overlap in the width direction of the case 1 by an appropriate dimension Ld, as shown in the partially enlarged view of FIG. 2. As a result, it is possible to reduce the overall width L1 of the multiple heat transfer tubes 2 and reduce the size of the heat exchanger HE.

The first and second recesses 3A, 3B are only partially provided in each bent pipe section 21. Therefore, the presence of the first and second recesses 3A, 3B prevents the flow resistance of hot and cold water from becoming significantly large when it flows inside the heat transfer tube 2, and it is possible to prevent the risk of having difficulty in passing water through the heat transfer tube 2. In addition, when the first and second recesses 3A, 3B are provided in each bent pipe section 21 by pressing, the first and second recesses 3A, 3B can be relatively small in size, so the amount of pressing (deformation) can be reduced. Therefore, it is possible to reduce residual stress due to pressing and provide excellent durability. Furthermore, if the amount of pressing on the bent pipe section 21 is large, there is a risk that the heat transfer tube 2 will be deformed so that both ends of the bent pipe section 21 open, but in this embodiment, such a risk can be eliminated.

Figures 7 to 12 show other embodiments of the present invention. In these figures, elements that are the same as or similar to those in the previous embodiment are given the same reference numerals as those in the previous embodiment.

7 and 8, the first and second recesses 3A, 3B are provided only on one side of the left and right side portions of the curved tube portion 21 of each of the first and second heat transfer tubes 2A, 2B, and the first and second recesses 3A, 3B are not provided on the other side. The second heat transfer tube 2B has a configuration in which the first heat transfer tube 2A is turned upside down, as in the above embodiment.
8(c), on one side of the bent pipe portion 21 of the first heat transfer tube 2A, the portion where the second recess 3B is formed is fitted into the portion where the first recess 3A is formed. On the other hand, on the opposite side of the bent pipe portion 21 of the first heat transfer tube 2A, the portions where the first and second recesses 3A, 3B are not formed are arranged in contact with or close to each other.

In this embodiment, as shown in FIG. 8(b), the straight tube sections 20 of the first and second heat transfer tubes 2A, 2B can be overlapped by an appropriate dimension Le in the width direction of the case 1. Therefore, as in the previous embodiment, the overall width of the multiple heat transfer tubes 2 (2A, 2B) can be reduced. Compared to the previous embodiment in which the first and second recesses 3A, 3B are provided on both the left and right side portions of the curved tube section 21, it is also possible to simplify the configuration of each heat transfer tube 2.

9 and 10, the first heat transfer tube 2A is provided with a pair of first recesses 3A on both the left and right side surfaces of each bent tube portion 21, whereas the second heat transfer tube 2B is not provided with a portion corresponding to the second recesses 3B. An existing serpentine tube body can be used as the second heat transfer tube 2B.
As shown clearly in FIG. 10C, parts of the bent pipe portions 21 of the second heat transfer tube 2B are directly fitted into the pair of first recesses 3A of the first heat transfer tube 2A.

In this embodiment, as shown in FIG. 10(b), the straight tube sections 20 of the first and second heat transfer tubes 2A, 2B can be overlapped by an appropriate dimension Lf in the width direction of the case 1. Therefore, as in the previous embodiment, it is possible to reduce the overall width of the multiple heat transfer tubes 2 (2A, 2B). Since an existing heat transfer tube that does not have the second recess 3B can be used as the second heat transfer tube 2B, it is possible to reduce manufacturing costs.

11 and 12, the first heat transfer tube 2A is provided with a first recess 3A only on one of the left and right side surfaces of each bent tube portion 21. The second heat transfer tube 2B is not provided with a portion corresponding to the second recess 3B.
As clearly shown in FIG. 12(c), a part of the curved pipe section 21 of the second heat transfer tube 2B is fitted into the first recess 3A of the first heat transfer tube 2A, while the outer circumferential surface of the curved pipe section 21 of the second heat transfer tube 2B abuts or is in close proximity to the side opposite the first recess 3A.

In this embodiment, as shown in FIG. 12(b), the straight tube sections 20 of the first and second heat transfer tubes 2A, 2B can be overlapped by an appropriate dimension Lg in the width direction of the case 1. Therefore, as in the previous embodiment, it is possible to reduce the overall width of the multiple heat transfer tubes 2 (2A, 2B). As the second heat transfer tube 2B, an existing heat transfer tube that does not have the second recess 3B can be used, and the first heat transfer tube 2A has the first recess 3A on only one side, which makes it possible to reduce manufacturing costs.

The present invention is not limited to the above-described embodiment. The specific configuration of each part of the heat exchanger and hot water device according to the present invention can be freely designed and modified in various ways within the intended scope of the present invention.

The specific shape, size, depth, etc. of the first and second recesses are not limited, and their shapes may be different depending on whether they are provided on both the left and right side surfaces of the curved tube portion of the heat transfer tube or only on one side.
In the above-described embodiment, of the multiple heat transfer tubes that are shifted in the vertical direction, one on the lower side is described as the first heat transfer tube and the other is described as the second heat transfer tube, but this is not limited to this and may be reversed from the above-described embodiment.
In the above embodiment, the x and y directions in the present invention are substantially horizontal directions, and the z direction corresponds to the vertical height direction, but the present invention is not limited to this, and these directions can be selected appropriately. For example, it is also possible to configure a configuration in which multiple heat transfer tubes lying in a substantially horizontal position are stacked (arranged) in the vertical height direction, that is, the y direction is the vertical height direction. In this case, the overall width of the multiple heat transfer tubes in the vertical height direction can be reduced, thereby making it possible to reduce the size of the heat exchanger.

The heat transfer tube is serpentine, but the specific size, number, and material of the straight and curved sections are not limited. The heat transfer tube can be formed by bending a single tube member, but instead, the straight and curved sections can be formed from separate members and connected together.

The heating medium in the present invention is not limited to the combustion gas generated by the burner, but may be high-temperature exhaust gas or the like.
The heat exchanger according to the present invention can be used for purposes other than latent heat recovery.
The hot water system in the present invention is a concept that includes hot water systems for hot water heating, snow melting, etc., in addition to hot water supply systems for general hot water supply and hot water supply for baths.

HE Heat exchanger WH Water heating device 1 Case 2 Heat transfer tube 2A, 2B First and second heat transfer tubes (heat transfer tubes)
3A, 3B First and second recesses

Claims (4)

The heat transfer tube has a serpentine shape in which a plurality of straight pipe sections extending in a predetermined x direction and arranged at intervals in a z direction intersecting the x direction are connected in series via a plurality of curved pipe sections, and is provided in a region where a heating medium flows, with a plurality of heat transfer tubes being stacked and arranged in a y direction intersecting the x and z directions;
The heat exchanger includes first and second heat transfer tubes that are adjacent to each other in the y direction and are offset in the z direction such that the straight tube portions do not overlap each other and portions of the curved tube portions overlap each other when viewed in the y direction,
a first recess and a second recess are provided in each of the bent pipe portions of the first and second heat transfer tubes to partially reduce a thickness in a y direction at a mutually overlapping portion compared to other portions;
The first recesses are arranged offset in the z direction from a center line in the width direction of each of the curved pipe portions of the first heat transfer tube in the z direction, and are provided on one side of both side surfaces of each of the curved pipe portions facing each other in the y direction so that a plurality of the first recesses are not present at the same time.
the second recessed portion is disposed offset from a width direction centerline of each of the curved pipe portions of the second heat transfer tube in the z direction to a side opposite to a direction in which the first recessed portion is offset, and is provided so as not to coexist in plurality on one side of both side surface portions of each of the curved pipe portions facing each other in the y direction,
a heat exchanger including a heat transfer tube having a shape and size identical to that of the first heat transfer tube, the second heat transfer tube being configured as an inverted heat transfer tube in the z-direction, and the first and second recesses being fitted together at their respective locations . 2. The heat exchanger of claim 1,
a pair of the first recesses are provided on both side surfaces of each of the curved pipe portions of the first heat transfer pipes that face each other in a y direction. 2. The heat exchanger of claim 1,
a first recess provided on only one of both side surfaces of each of the curved pipe portions of the first heat transfer pipes that face each other in a y direction; A water heating system comprising the heat exchanger according to any one of claims 1 to 3.

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