JP2003014309A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger with a simplified structure capable of suppressing the generation of drain and of obtaining high heat exchange efficiency. SOLUTION: Heat absorption pipes 5, 6, 7 are provided at least on 3 lines vertically while penetrating a fin 4. Water to be heated is communicated from a starting end of the heat absorption pipe 5 located on the uppermost stream side of combustion waste to a final end 7 of the heat absorption pipe located at lowermost stream side. Between each heat absorption pipe 6 on the second line 17 located on the downstream side of the first line 16 located on the uppermost stream side of combustion waste and each heat absorption pipe 7 on the third line 18 as a boundary, there are provided a plurality of offset fins 19 that are heat absorption promotion means for increasing heat exchange efficiency at the fin 4b on the downstream side at the boundary position.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat exchanger provided in a water heater or the like.

[0002]

2. Description of the Related Art Conventionally, a heat exchanger of this type provided in a water heater has a plurality of fins provided in a combustion exhaust passage of a burner and a plurality of heat absorbing tubes arranged through the fins. By providing the water to be heated through the heat absorbing tube, heat exchange is performed to generate hot water. In general, endothermic tubes
A plurality of first endothermic tube groups arranged in the left-right direction crossing the combustion exhaust flow and above the first endothermic tube group (downstream side of the combustion exhaust gas)
A second endothermic tube group arranged in the left-right direction intersecting with the combustion exhaust flow, and conducts the heated water from the start end of the first endothermic tube group toward the end of the second endothermic tube group. . Further, in order to obtain high thermal efficiency, the fin shape is expanded and a plurality of third heat absorbing tube groups arranged in the left-right direction above the second heat absorbing tube group (downstream side of the combustion exhaust gas) intersecting the combustion exhaust gas flow. Provision is made. The third
The start end of the endothermic tube group is connected to the end of the second endothermic tube group. As a result, the heat absorption area is increased and the heat exchange efficiency is improved.

However, when the heat exchanger is constructed by providing the third heat absorption tube group, when the combustion amount of the burner is reduced, the heat absorption area for the combustion amount becomes excessively large. Exhaust temperature is below the dew point around the group. As a result, the water vapor of the combustion exhaust gas becomes a drain and adheres to the surface of each endothermic tube of the third endothermic tube group or to the fins in the vicinity thereof, and there is a disadvantage that the endothermic tubes and fins are corroded and the life is shortened.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a heat exchanger having a simple structure, which can suppress the generation of drain and obtain high heat exchange efficiency.

[0005]

In order to achieve the above object, the present invention is directed to a plurality of fins provided in a combustion exhaust flow path of a burner, and a left-right direction intersecting with the combustion exhaust flow and along the combustion exhaust flow. A plurality of heat absorbing tubes arranged in the vertical direction and penetrating each fin, from the start end of the heat absorbing tube located on the most upstream side of the combustion exhaust to the end of the heat absorbing tube located on the most downstream side. In the heat exchanger for conducting the above, the endothermic tubes are arranged in at least three rows in the vertical direction, and each of the second row located on the downstream side of the first row located on the most upstream side of the combustion exhaust gas. With the boundary between the heat absorption tube and each heat absorption tube in the third row, there is provided a heat absorption promoting means for increasing the heat exchange efficiency in the fins on the downstream side of the boundary position.

In the present invention, since the heat absorption tubes are arranged in at least three rows in the vertical direction, a relatively large heat absorption area can be obtained, and high heat exchange efficiency can be obtained.

Further, according to the present invention, first, the heat absorption tubes in the second row and the heat absorption tubes in the third row located on the downstream side of the first row located on the most upstream side of the combustion exhaust gas are connected. The heat absorption promoting means is provided at the boundary position between the fins to increase the heat exchange efficiency of the fins on the downstream side of the boundary position. As a result, it is possible to suppress an extreme decrease in the surface temperature of the fins on the downstream side and the heat absorbing tubes, and it is possible to maintain the surface temperature of the fins on the downstream side and the heat absorbing tubes to a relatively high state, thereby preventing the occurrence of drainage. be able to.

Further, in the heat exchanger of the present invention, the distribution ratio of the heat exchange efficiency between the upstream side and the downstream side of the boundary position is 97: 3 to 92: 8 at the maximum combustion of the burner. It is preferable that the heat absorption area of the fins and the arrangement of the heat absorption tubes are set. The present inventor performs various experiments to obtain a relatively high heat exchange efficiency in the entire heat exchanger, and the heat exchange efficiency at which drainage does not occur on the downstream side of the boundary position is 3% to 8% of the whole. % Found necessary. By setting the heat absorption area of the fins and the arrangement of the heat absorption tubes based on this, it is possible to prevent the occurrence of drainage and configure a heat exchanger with high heat exchange efficiency.

Further, as one mode of the heat absorption promoting means in the present invention, the heat absorption promoting means may be constituted by a slit that divides the fin into an upstream side and a downstream side of combustion exhaust at the boundary position. Usually, the highest endothermic position in this type of fin is the lower edge of the fin with which the combustion exhaust contacts. This is because this type of fin has a property that the heat transfer is increased at the contact edge portion of the combustion exhaust gas and the temperature thereof is higher than the other portions. By forming a cut at the boundary position, the edge where the combustion exhaust gas contacts the boundary position can be formed on the downstream side of the boundary position. As a result, the heat exchange efficiency on the downstream side is improved, the surface temperatures of the fins on the downstream side and the heat absorbing tubes can be increased, and the structure can easily prevent the occurrence of drainage.

As another aspect of the heat absorption promoting means in the present invention, the heat absorption promoting means forms a pair of parallel cuts in a part of the fin at the boundary position, and a plate-shaped portion between the cuts is finned. It can be mentioned that it is constituted by a plurality of offset fins which are raised in the front-back direction and abut the combustion exhaust gas on the cut edges thereof. By providing the offset fin, an edge where the combustion exhaust gas strikes at the boundary position is formed at the cut and the lower edge of each offset fin. Thereby, the heat exchange efficiency on the downstream side can be improved. Furthermore, by providing a plurality of offset fins, the heat of the combustion exhaust gas can be made to circulate to the upper side of each heat absorption tube by heat conduction and be absorbed uniformly. As a result, the surface temperature of the fins on the downstream side and the heat absorbing tubes can be increased, and the occurrence of drainage can be prevented.

Further, in the present invention, the fins located on the downstream side of the combustion exhaust gas via the heat absorption promoting means are provided with a part of the fins above the respective endothermic tubes corresponding to the endothermic tubes adjacent to the left and right. It is preferable that a plurality of other offset fins are formed by forming a pair of parallel cuts and projecting a plate-shaped portion between the cuts in the front and back directions of the fins. According to each of the other offset fins, the heat of the combustion exhaust flowing between the heat absorbing pipes adjacent to the left and right can be circulated to the upper side of each heat absorbing pipe by heat conduction, and the combustion exhaust heat can be efficiently transmitted to the fins and the heat absorbing pipes. Can be made. As a result, the heat absorption area of the fin can be made relatively small and sufficient heat exchange can be performed, so that the fin can be made compact.

[0012]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view schematically showing a part of a water heater employing the heat exchanger of this embodiment, FIG. 2 is an explanatory view showing a main part configuration of the heat exchanger of this embodiment, and FIG. 3 is an offset fin. Is an explanatory perspective view showing the shape of the heat exchanger, FIGS. 4 and 5 are explanatory views showing the main configuration of a heat exchanger of another embodiment, FIG. 6 is a diagram showing a drain generation region of the heat exchanger, and FIG. It is explanatory drawing which shows the principal part structure of the heat exchanger mentioned as a comparative example.

As shown in FIG. 1, the heat exchanger A according to the present embodiment has a burner 2 located above the burner 2 of the water heater 1.
Is provided in the combustion exhaust passage 3. The heat exchanger A includes a plurality of fins 4 and endothermic tubes 5, 6, 7 penetrating each fin 4.
And an introduction pipe 8 for introducing water to be heated (tap water) is connected to the upstream side of the heat absorbing pipes 5, 6 and 7 and to be heated to the downstream side of the heat absorbing pipes 5, 6 and 7. A lead-out pipe 9 for leading out water (hot water) is connected. The inlet pipe 8 and the outlet pipe 9 are connected by a bypass water pipe 10, and the temperature of the hot water in the outlet pipe 9 can be adjusted by the mixing section 11. Further, the burner 2 has a combustion amount controlled by the hot water supply operation control means 12. The hot water supply operation control means 12 controls the combustion amount of the burner 2 based on the detection results of a water amount sensor, a hot water temperature sensor 13, a water temperature sensor 14, etc., which are not shown. Further, the hot water supply operation control means 12 is provided with a heat exchange control means 15, which will be described later in detail, so that combustion control of the burner 2 based on the temperature of the heated water in the heat absorption tubes 5, 6, 7 can be performed. It has become.

As shown in FIG. 2, the heat exchanger A includes a plurality of heat absorbing tubes 5, 6, 7 penetrating the fin 4. Each of the endothermic tubes 5, 6, 7 is a single conduit meandering through the fins 4, and includes a first endothermic tube group 16 arranged in the left-right direction on the most upstream side of combustion exhaust, and Second heat absorbing tube group 1 arranged in the left-right direction above the first heat absorbing tube group 16
7 and a third endothermic tube group 18 arranged in the left-right direction above the second endothermic tube group 17 are arranged in three rows in the vertical direction. The water to be heated is the first endothermic tube group 1 as shown by the arrow in the figure.
It is introduced from the start end of 6 and is led out from the end of the third endothermic tube group 18.

A plurality of first offset fins 19 are formed on the fins 4 between the second endothermic tube group 17 and the third endothermic tube group 18. The first offset fin 19 is shown in FIG.
As shown in FIG. 5, after forming a pair of parallel notches in a part of the fin 4, the plate-shaped portion between the notches is raised from one surface side to the other surface side. Then, the combustion exhaust gas passes through the front and back of the first offset fin 19 as shown by the arrow in FIG.

As shown in FIG. 2, an auxiliary offset fin 20 is provided below the first offset fin 19 (on the upstream side of the combustion exhaust gas). The both ends of the first offset fin 19 are the endothermic tubes 6 of the second endothermic tube group 17.
Is formed so as to face the upper side of the above, and this constitutes the heat absorption promoting means of the present invention. That is, by providing the first offset fin 19, the heat absorption region of the fin 4 is virtually divided into the upstream heat absorption region 4a and the downstream heat absorption region 4b via the imaginary line w in the drawing. As a result, an edge against which the combustion exhaust gas strikes can be formed at the lower edge of the downstream heat absorption region 4b, and heat exchange efficiency can be improved. Further, the heat of the combustion exhaust gas is circulated to the upper side of the heat absorbing tubes 6 of the second heat absorbing tube group 17 by heat conduction by the first offset fins 19, and uniform heat transfer can be obtained.
A relatively high heat exchange efficiency can be obtained.

A second offset fin 21 and an auxiliary offset fin 22 are formed between the heat absorbing tubes 7 of the third heat absorbing tube group 18. These offset fins 2
1 and 22 improve the heat exchange efficiency by causing the heat of the combustion exhaust to circulate above the heat absorbing tubes 7 of the third heat absorbing tube group 18 by heat conduction.

Here, in the heat exchanger A, as shown in FIG. 1, a temperature sensor 23 for detecting the temperature of the water to be heated is provided near the inlet of the third heat absorbing tube group 18. Then, the heat exchange control means 15 controls the combustion amount of the burner 2 in accordance with the flow rate of the heated water so that the temperature detected by the temperature sensor 23 becomes higher than the dew point of the combustion exhaust gas. It is possible to reliably prevent the drainage of the heat absorbing tubes 7 of the group 18 and the fins 4 in the vicinity thereof.

This is shown by the heat exchange efficiency distribution between the upstream endothermic region 4a and the downstream endothermic region 4b shown in FIG. 2 when the total heat exchange efficiency at the maximum combustion amount of the burner 2 is 88%. As shown in Table 1, the heat exchange efficiency of the upstream endothermic region 4a becomes 84.6 to 81.5%, and the downstream endothermic region 4b
Heat exchange efficiency of 3.4 to 6.5%.

[0020]

[Table 1]

The fuel gas species of the burner 2 is 13A-1.
In this case, the air ratio during normal combustion is around 1.6, but the dew point of the combustion exhaust gas at this time is approximately 51 to 53 ° C. Considering such variations in the air ratio, Table 1
It is preferable to set the heat exchange efficiency of the upstream endothermic region 4a to 85 to 81% and the heat exchange efficiency of the downstream endothermic region 4b to 3 to 7% based on the above data. Then, in the present embodiment, the total heat absorption areas of the first offset fins 19 and the fins 4 are set so that the heat exchange efficiency is distributed between the upstream heat absorption region 4a and the downstream heat absorption region 4b. That is, the heat exchange efficiency distribution ratio between the upstream side and the downstream side is 9
7: 3 to 92: 8, and based on this, the fin 4
The heat absorption area and the arrangement of the heat absorption tubes 7 are set. As a result, the overall heat exchange efficiency of the burner 2 at the maximum combustion amount is 88
%, It is possible to obtain a relatively high heat exchange efficiency, prevent drainage, and form a compact heat exchanger A.

Further, in the heat exchanger A, instead of the temperature sensor 23 for detecting the temperature of the water to be heated near the inlet of the third endothermic tube group 18, as shown in FIG. 1
A temperature sensor 24 may be provided near the exit of 8. In this case, the temperature sensor 24 detects the temperature of the heated water (hot water) heated through the heat exchanger A. Then, in the heat exchange control means 15, the temperature of the heated water at the inlet of the third endothermic tube group 18 is calculated from the temperature detected by the temperature sensor 24, the hot water supply capacity, the heat exchange efficiency data, etc., and the calculated temperature is calculated. The combustion amount of the burner 2 may be controlled according to the flow rate of the water to be heated so that is higher than the dew point of the combustion exhaust gas. Specifically, referring to Table 1, for example, the combustion amount of the burner 2 is controlled so that the temperature of the heated water (hot water) heated through the heat exchanger A becomes 57 ° C. or higher. Also by this, it is possible to reliably prevent the drainage of the heat absorbing tubes 7 of the third heat absorbing tube group 18 and the fins 4 in the vicinity thereof.

Next, another embodiment of the present invention will be described. In the heat exchanger B of another embodiment, as shown in FIG. 4, each of the heat absorption tubes 5, 6, 7 penetrating the fin 25 has a structure shown in FIG.
The first heat-absorbing tube group 16 is arranged in the left-right direction on the most upstream side of the combustion exhaust, and the second heat-absorbing tube group is arranged above the first heat-absorbing tube group 16 in the left-right direction. Endothermic tube group 1
7 and a third endothermic tube group 18 arranged in the left-right direction above the second endothermic tube group 17 are arranged in three rows in the vertical direction.

The fin 25 is provided with a cut 26 between the second endothermic tube group 17 and the third endothermic tube group 18, which constitutes the endothermic promoting means of the present invention. That is, by providing the cut 26, the edge contacting the combustion exhaust can be formed, and the heat exchange efficiency of the lower edge of the downstream endothermic region 25b can be improved. Further, in the downstream endothermic region 25b divided by the cut 26, the heat transfer between the upstream endothermic region 25a and the downstream endothermic region 25b is greater than that in the first offset fin 19 (see FIG. 2) described above. Is small. Therefore, in order to obtain sufficient heat exchange efficiency, it is necessary to make the heat absorption area of the downstream heat absorption region 25b of the fin 25 relatively large. Therefore, when a more compact structure is desired, for example, as in the heat exchanger B ′ shown in FIG. 5, the offset fins 27 and the auxiliary offsets are provided between the heat absorbing tubes 7 of the third heat absorbing tube group 18. By forming the fins 28, downsizing can be achieved.

Here, the heat exchanger A of each of the above-mentioned embodiments
A test for confirming the drain generation condition in the cases B and B will be described with reference to FIG. In this test, in addition to the heat exchangers A and B, a heat exchanger C having a structure shown in FIG. 7 was used for comparison. The heat exchanger C, as shown in FIG.
The arrangement of the heat absorption tubes 5, 6 and 7 is the same as that of the heat exchangers A and B, but the fins 29 are not provided with the structure corresponding to the heat absorption promoting means of the present invention.

In FIG. 6, when the burner 2 (see FIG. 1) has the maximum combustion amount, the heat exchange efficiency is maximized when the amount of water to be heated in the endothermic tubes 5, 6, 7 is maximum and the outlet temperature ( The heat exchanger outlet temperature) is at a minimum. Solid lines a, b, and c are the drain generation regions (drain lines) of the heat exchanger A (shown in FIG. 2), the heat exchanger B (shown in FIG. 4), and the heat exchanger C (shown in FIG. 7), respectively.
Is shown. When it is below the drain line, drain is generated in the third endothermic tube group 18. As a result, the alternate long and short dash lines a ′, b ′, c ′ indicate the control temperature of the outlet heated water temperature at which drainage does not occur in the third heat absorption tube group 18 of each heat exchanger A, B, C. As is clear from FIG. 6, in the heat exchangers A and B of the above-described respective embodiments, the drain line can be formed at a lower position than the heat exchanger C of the comparative example. As a result, according to the heat exchangers A and B of the respective embodiments, it is apparent that the hot water outlet temperature can be made relatively low, so that drainage can be prevented and high heat exchange efficiency can be obtained.

In each of the above-described embodiments, the plurality of endothermic tubes 5, 6, 7 are arranged in three rows in the vertical direction, but even if they are arranged in three rows or more, the uppermost part ( It goes without saying that drainage can be reliably prevented by controlling the temperature of the endothermic tube group located at the most downstream portion of the combustion exhaust gas.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a part of a water heater using a heat exchanger according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a main configuration of a heat exchanger of this embodiment.

FIG. 3 is an explanatory perspective view showing the shape of an offset fin.

FIG. 4 is an explanatory diagram showing a main part configuration of a heat exchanger of another embodiment.

FIG. 5 is an explanatory diagram showing a main configuration of a heat exchanger according to another embodiment.

FIG. 6 is a diagram showing a drain generation region of the heat exchanger.

FIG. 7 is an explanatory diagram showing a main configuration of a heat exchanger of a comparative example.

[Explanation of symbols]

A, B, B '... Heat exchanger, 2 ... Burner, 3 ... Combustion exhaust flow passage, 4, 25 ... Fin, 5, 6, 7 ... Endothermic tube, 16 ... First endothermic tube group (first row) Each heat absorbing tube), 17 ... Second heat absorbing tube group (each heat absorbing tube in the second row), 18 ... Third heat absorbing tube group (third
Each heat absorption tube in the row), 19 ... First offset fin (heat absorption promoting means), 21 ... Second offset fin (other offset fin), 26 ... Cut (heat absorption promoting means).

Claims (5)

[Claims] 1. A plurality of fins provided in a combustion exhaust flow passage of a burner, and a plurality of fins arranged in a horizontal direction intersecting the combustion exhaust flow and in a vertical direction along the combustion exhaust flow, and the heat absorption penetrating each fin. In a heat exchanger including a pipe, from the start end of the endothermic pipe located on the most upstream side of the combustion exhaust gas to the end of the endothermic pipe located on the most downstream side, the endothermic pipe in the vertical direction. Boundary between each heat-absorbing tube in the second row and each heat-absorbing tube in the third row, which is arranged in at least three rows and is located on the downstream side of the first row, which is located on the most upstream side of the combustion exhaust gas. As a heat exchanger, the heat exchanger is provided with heat absorption promoting means for increasing heat exchange efficiency in the fins on the downstream side of the boundary position. 2. The distribution ratio of the heat exchange efficiency between the upstream side and the downstream side of the boundary position at the maximum combustion of the burner is 97:
The heat exchanger according to claim 1, wherein the heat absorption area of the fins and the arrangement of the heat absorption tubes are set so as to be 3 to 92: 8. 3. The heat exchanger according to claim 1, wherein the heat absorption promoting means is constituted by a cut that divides the fin into an upstream side and a downstream side of combustion exhaust at the boundary position. 4. The heat absorption promoting means forms a pair of parallel cuts in a part of the fin at the boundary position, and bulges a plate-shaped portion between the cuts in the front and back direction of the fin to cut combustion exhaust gas. The heat exchanger according to claim 1, wherein the heat exchanger is constituted by a plurality of offset fins that abut against the edge. 5. The fins located on the downstream side of the combustion exhaust gas via the heat absorption promoting means have a pair of parallel fins at a position above the respective endothermic tubes corresponding to the left and right adjacent endothermic tubes. The heat exchange according to any one of claims 1 to 4, wherein a plurality of other offset fins are formed by forming notches and projecting a plate-shaped portion between the notches in a front and back direction of the fins. vessel.