JP3308437B2 - Water heater heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger of a water heater for heating supplied water to make hot water and supplying hot water to a bathtub or a hot water faucet.

[0002]

2. Description of the Related Art Conventionally, a plurality of fins are juxtaposed in a heat absorbing portion so that water supplied to a water heater can be efficiently subjected to heat transfer in a heat absorbing portion heated by combustion and exhaust of a burner. A heat exchanger is known which has a configuration in which a heat absorbing tube for instantaneously heating supplied water is bent a plurality of times in a meandering manner so as to cross the heat absorbing portion many times while penetrating each fin. A plurality of portions of the heat absorbing tube crossing the heat absorbing portion will be referred to as a “pass” hereinafter.
Call. In this heat exchanger, while hot water is being used, the water in the water supply pipe is heated each time it passes through each path and rises in temperature, and reaches the highest temperature (= set hot water temperature) at the outlet of the most downstream path communicating with the hot water pipe. Hot water.

[0003]

By the way, when the use of hot water is interrupted in the heat exchanger, the movement of water in the heat absorbing tube stops at that point. However, since each of the fins is generally made of a material having a high thermal conductivity such as a copper plate, heat near the outlet of the most downstream path (the outlet of the heat absorbing portion) is
Since the water is transmitted to other parts through the fins, the water temperature in the heat absorbing part gradually becomes uniform. Therefore, for example, as shown in FIG. 1, when the hot water supply is interrupted, the water temperature at the outlet of the most downstream path indicated by reference numeral 6 is approximately 25 ° C., which is the water temperature during steady hot water supply (while hot water supply is being used). (Approximately 1 indicates the most upstream path communicating with the water supply pipe,
Reference numerals 2 to 5 indicate respective paths provided between the paths 1 and 6).

[0004] Therefore, when the hot water supply is resumed in this state, even if the heating of the heat absorbing portion is promptly resumed, the outlet water temperature until the water temperature at the outlet of the most downstream path becomes the highest is formed. However, there is a problem that the temperature of the hot water does not reach the set hot water temperature, which gives a discomfort to a user such as a shower.

Therefore, a bypass pipe for bypassing the heat absorbing pipe and a flow control valve for controlling the bypass flow rate ratio are provided in the bypass pipe, and a part of the supply water flows through the bypass pipe to keep the water temperature in the heat absorbing section at a high temperature. At the same time, there has been proposed a heat exchanger configured to prevent a drop in hot water temperature at the time of re-hot water supply.

However, since the flow control valve is expensive, it can be used only for high-end models. Therefore, a method of controlling the bypass flow ratio to be constant without providing the flow control valve in the bypass pipe has been proposed.

[0007] In this method as well, by flowing a part of the supply water to the bypass pipe side at a predetermined flow ratio, the average water temperature in the heat absorbing portion during the interruption of the hot water supply is shown in FIG. 1 as shown in FIG. It can be kept at a higher temperature (30 ° C.). But,
Actually, after the hot water supply is interrupted, the water from the bypass pipe is mixed with the hot water from the endothermic pipe at the same ratio as during normal tapping immediately after the hot tap, and the hot water temperature after mixing is the same as that when there is no bypass pipe. Therefore, the temperature of the hot water immediately after the re-starting of the hot water was 25 ° C. as in the above case, and there was no effect of preventing the temperature of the hot water immediately after the re-starting of the hot-water.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for controlling the use of hot water after interrupting the use of hot water without providing a flow control valve for controlling a bypass flow ratio in a bypass pipe that partially bypasses a heat absorbing pipe for heating feed water. An object of the present invention is to provide a heat exchanger of a hot water supply device capable of preventing a drop in hot water temperature immediately after re-hot water supply.

[0009]

SUMMARY OF THE INVENTION A heat exchanger of a water heater according to the present invention has a starting end connected to a water supply pipe and an end connected to a tapping pipe so that the heat exchanger as a whole has a single water passage. It is provided with the formed heat absorbing tube, and is configured as follows.

That is, a first bypass pipe connecting the water supply pipe and a specific location of the heat absorption pipe, and a second bypass pipe connecting the water supply pipe and a location upstream of the specific location of the heat absorption pipe. Having.

[0011] The specific location is selected at a position upstream of the end of the heat absorbing tube.

More specifically, the specific location is a position where the amount of heat absorbed from the start end of the heat absorbing tube to the specific location is greater than the amount of heat absorbed from the specific location to the end of the heat absorbing tube.

[0013] In a preferred embodiment according to the present invention, the heat absorbing tube is formed such that the inside diameter on the upstream side of the specific location is smaller than that on the downstream side.

In a modification of the above embodiment, the inner diameter of the first bypass pipe is set so that the amount of water flowing through the first bypass pipe is equal to or less than the amount of water flowing upstream of a specific portion of the heat absorbing pipe. Is selected.

According to the present invention, the specific location to which the first bypass pipe is connected is a position upstream of the end of the heat absorbing pipe and between the starting end of the heat absorbing pipe and the specific location. By selecting a position where the amount of heat absorbed is greater than the amount of heat absorbed between the specific location and the end of the heat absorbing tube, it is possible to raise the average water temperature of the heat absorbing tube while hot water supply is interrupted, Further, since it is possible to prevent the feed water from directly mixing into the hot water from the heat absorbing pipe, the hot water temperature immediately after the hot water can be raised.

In addition, according to the present invention, the water supply pipe is provided with the second bypass pipe connecting the water supply pipe and the heat absorption pipe on the upstream side of the specific point, so that the water supply is bypassed by the second bypass pipe. The temperature of the hot water at the portion of the heat absorption tube to be heated can be further increased.

According to the preferred embodiment of the present invention, the heat absorbing tube is formed such that the inside diameter on the upstream side of the specific location is smaller than that on the downstream side, so that a decrease in the flow rate of the water supply at the upstream side portion can be prevented. In addition, it is possible to prevent a decrease in the rate of heat transfer from the heat absorption pipe to the water supply. Therefore, local boiling in the heat absorbing tube can be easily prevented.

Further, according to the modification of the above embodiment, the flow rate of the first bypass pipe is equal to or less than the flow rate of a portion of the heat absorbing tube upstream of a specific portion, and therefore, the same as above. In addition, it is possible to prevent a decrease in the flow rate of the water supply at the upstream portion of the specific location, and it is possible to prevent a reduction in the rate of transfer of heat from the heat absorbing tube to the water supply. Therefore, local boiling in the heat absorbing tube is easily prevented.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 3 is a block diagram showing the overall configuration of a water heater to which one embodiment of the present invention is applied.

The water heater includes a heat exchanger 7 which is heated by the combustion exhaust gas of a burner (not shown), and a heat absorbing pipe 13 which supplies water from a water supply source (not shown) to the heat exchanger 7.
A water supply pipe 1 for supplying water (see FIG. 4) and a water flow sensor 3 for detecting water flow in the water supply pipe 1 are provided. The water heater also supplies hot water from a drum cooling unit 5 for cooling a burner (not shown) and a heat exchanger 7 (heat absorbing tube 13) to a bathtub and a hot water supply faucet (neither is shown). A hot water supply pipe 9 is also provided.

In the above configuration, when it is determined from the detection signal from the water flow sensor 3 that there is water flow at a predetermined flow rate or more, a controller (not shown) for controlling each part of the water heater is provided.
Performs combustion control of a burner (not shown) so that hot water at a hot water set value set by a temperature setting unit (not shown) is obtained from the heat exchanger 7.

FIG. 4 shows a detailed configuration of the heat exchanger 7 of FIG.

The heat exchanger 7 is bent in a meandering manner a plurality of times as a whole so as to traverse the heat absorbing portion 11 many times to receive the combustion exhaust gas of the burner, and to supply hot water through the water supply pipe 1. One heat absorbing tube 13 is provided. The heat exchanger 7 has a plurality of fins 15 arranged in parallel with the heat absorbing portion 11 in order to enhance the heat transfer property of the entire heat absorbing tube 13, and directly connects the downstream end of the water supply tube 1 to a downstream portion of the heat absorbing tube 13. A bypass pipe 17 for allowing a part of water to flow into the heat absorption tube 13 from the most upstream side to flow from a downstream portion of the heat absorption tube 13.

The heat absorbing tube 13 constitutes a single pipe (that is, the heat absorbing tube 13) as a whole by connecting a plurality of portions (paths) crossing the heat absorbing portion 11 substantially in parallel and connecting the respective paths. It is composed of a plurality of connecting tubes formed in a substantially U-shape.

In the present embodiment, the heat absorbing tube 13 includes six paths and five connecting tubes as shown. Therefore, in the following description, regarding each of the above paths, the most upstream path communicating with the water supply pipe 1 is the first path 12, and the most downstream path communicating with the hot water supply pipe 9 is the sixth (final) path 22. ,
Each path between the first path 12 and the sixth path 22 is sequentially referred to as a second path 14, a third path 16,
These are referred to as a fourth pass 18 and a fifth pass 20. On the other hand, for each connecting pipe, the connecting pipe connecting the first path 12 and the second path 14 is the first connecting pipe 24, the fifth path 20 and the sixth path 22.
The fifth connecting pipe 32 and the first connecting pipe 24
The second connecting pipe 26, the third connecting pipe 28, and the fourth connecting pipe are arranged in this order from the upstream side to the downstream side.
It is referred to as a coupling tube 30.

In this embodiment, as shown in FIG.
The coupling pipe 30 is a junction of the bypass pipe 17.
The first to twelfth to fourth paths upstream of the junction
The inner diameter of the path 18 is determined by the fifth path 20 and the sixth path 20 in order to prevent a decrease in the flow rate of the feedwater in each of the paths and a decrease in the rate of transfer of heat transmitted from each path to the feedwater due to the decrease in the flow rate.
The diameter is set smaller than the inner diameter of the path 22.

As shown in FIGS. 5 and 6, all the fins 15 are penetrated by the first path 12 to the sixth path 22, so that the first path 12 to the sixth path 22 respectively Are thermally connected to each other through the fins 15 of the first and second fins.
That is, when a burner (not shown) is controlled by a controller (not shown) for combustion and heat from the burner is given to each fin 15, the first to sixth passes 12 to 22 pass from each fin 15. Heats the water passing through each pass by depriving the transferred heat. On the other hand, water supply pipe 1
When the combustion of the burner is stopped by stopping the flow of water to the burner, heat from the hottest hot water in the sixth pass 22 and heat from the relatively hot hot water in the fifth pass 20 and the fourth pass 18 are respectively Of the coldest water in the first path 12 through the fins 15
The water is transmitted to the relatively low-temperature water in the path 14 and the third path 16. As a result, the temperature in the heat exchanger 7 gradually becomes uniform.

In the present embodiment, the bypass flow rate of the feed water is set so that the highest average water temperature is obtained in the heat absorbing section 11 immediately after the hot water supply is stopped after the hot water supply is interrupted, and the hot water is kept at the high average water temperature. A bypass pipe 17 having a ratio set to 0.5 is employed, and the water supply pipe 1 and the fourth coupling pipe 30 are directly connected via the bypass pipe 17. Therefore, only the remaining 0.5 of the supply water flows into the first path having the lowest temperature, whereby the average water temperature in the heat absorbing section 11 slightly increases.

Here, if the bypass flow rate ratio of the bypass pipe 17 is 0.5, the flow rate of the supply water in the first path 12 to the fourth path 18 upstream of the fourth connection pipe 30 does not decrease so much, and accordingly The rate of heat transfer from each pass to the water supply also does not decrease. For this reason, the temperature in the first to fourth paths 12 to 18 rises, and there is no such a problem that local boiling occurs and noise increases. Therefore, it is desirable not to make the bypass flow rate ratio too large in order not to cause local boiling.

Next, the reason why by setting the joining position of the bypass pipe 17 having the above-described configuration to the fourth connecting pipe 30, it is possible to obtain hot water at the highest average water temperature immediately after re-watering after the stop of hot water supply is used. This will be described with reference to FIG.

In FIG. 7, a broken line (straight line) 19 indicates the bypass flow rate of the feed water, and a solid line (curve) 21 indicates the average water temperature in each (six) passes when the hot water supply is interrupted.

In order to set the average water temperature to about 32 ° C. (the maximum value) indicated by the reference numeral 23, the bypass flow rate ratio is set so that at least about 60 to 65% of the amount of heat absorbed by the entire heat absorbing tube 13 is obtained. 0.5 and the merging position should be near the exit of the fourth pass 20. This is the following (1)
It is supported by the formula. Hereinafter, description will be made using this equation (1). (THmax−TC) / 2 (TSmax−TC) (1) where TC: supply water temperature, TSmax: maximum set hot water temperature, TH
max: The temperature value of the heat absorption tube 13 immediately before the water in the bypass tube 17 joins the hot water in the heat absorption tube 13, and is represented by TS (set hot water temperature value).
= Temperature value that does not boil even at TSmax.

Here, TSmax = 75 ° C., THmax = 90 ° C.
Assuming that TC = 5 ° C. for the winter season, these values are substituted into the above equation (1) to obtain (90−90).
5) / 2 (75-5) = 0.607 is obtained. Also,
Both TSmax and THmax are the same as the above values.
Assuming that C = 20 ° C., these values are calculated by the above (1).
By substituting into the equation, (90−20) / 2 (75−
20) = 0.636 is obtained. From this calculation result, the bypass pipes are connected such that the ratio of the heat absorption amount of the heat absorption pipe upstream of the merging position of the bypass pipes to the total heat absorption quantity of the heat absorption pipes is about 60% to about 65%. It can be seen that a coupling tube should be selected. That is, in the heat exchanger including six paths as in the present embodiment, the merging position of the bypass pipe 17 is the fourth coupling pipe 30 located at the outlet of the fourth path 20. Match.

According to the above configuration, the junction of the bypass pipe 17 is set to the fourth coupling pipe 30 which can obtain an amount of heat absorption of about 60% to about 65% of the total heat absorption of the heat absorbing tube 13. Therefore, the average water temperature in the heat absorbing section 11 during the interruption of hot water supply is higher than 25 ° C. shown in FIG. 1 or 30 ° C. shown in FIG.
It will be 2 ° C. (see FIG. 8). This value is a temperature close to 30 ° C. in FIG. However, in the above configuration, as in the heat exchanger described with reference to FIG. 2, the hot water from the heat absorbing section and the water from the bypass pipe are not mixed at the heat absorbing section outlet, and the junction of the bypass pipe is located at the final path or in the vicinity thereof. Since there is no danger of water mixing with hot water such as a heat exchanger set in the site,
Hot water is discharged at 32 ° C, which is the average water temperature in the heat absorbing section. Therefore, it is possible to prevent a drop in the tapping temperature immediately after the tapping out of hot water supply.

In the present embodiment, the junction of the bypass pipe 17 is connected to the fourth joint so that the highest average water temperature (32 ° C.) can be obtained immediately after the hot water is re-discharged and the hot water can be discharged at the high average water temperature. Although the pipe 30 is used, the average water temperature and tap water temperature are set to 30 ° C. even when the junction is near the outlet of the second path 14 (the second coupling pipe 26) where at least about 30% of the heat absorption is obtained. (See FIG. 7). In view of the fact that there is no danger of water being mixed into the hot water and that the undershoot can be reduced by increasing the chances of absorbing the heat of the water, the confluence portion can be formed by the heat absorbing portion 11.
It is desirable to set the fourth path 20 on the upstream side rather than near the exit so that the distance to the exit can be lengthened.

FIG. 9 shows a heat exchanger to which another embodiment of the present invention is applied.

The difference between the present embodiment and the above-described embodiment is that the heat exchanger according to the present embodiment further increases the average water temperature in the heat absorbing section by using the above-described bypass pipe (hereinafter, referred to as “the heat exchanger”).
In addition to the first bypass pipe 17), the water supply pipe 1 and the second
The second embodiment is also provided with a second bypass pipe 19 which is piped so as to be directly connected to the second coupling pipe 26 at the outlet of the path 14. In the second bypass pipe 19, the bypass flow rate of the feed water is set to 0.1.
Three are adopted.

According to the above configuration, in addition to the first bypass pipe 17, the second bypass pipe 19 that directly connects the water supply pipe 1 and the second connection pipe 26 is provided, so that the heat generated during the interruption of the hot water supply is provided. The average water temperature in the exchanger 7 becomes 35 ° C., which is higher than 32 ° C. shown in FIG. 8 (see FIG. 10). In the present embodiment, since the hot water from the heat absorbing tube and the water from the bypass tube are not mixed at the outlet of the heat absorbing portion as in the heat exchanger described with reference to FIG. Hot water will be discharged at the water temperature of 35 ° C. Therefore, also in this embodiment, similarly to one embodiment, it is possible to prevent a drop in tapping temperature immediately after tapping again after hot water supply is stopped.

FIGS. 11 to 13 show first to third modified examples according to other embodiments of the present invention, respectively.

Although the heat exchanger shown in each of the above figures has four paths for convenience of illustration, it is theoretically different from the heat exchangers of the other embodiments having six paths. There is no point.

First, in the heat exchanger of FIG.
A first bypass pipe 57 that joins a first connection pipe 55 that connects the first and second paths 53, and a second bypass pipe 6 that joins a second connection pipe 61 that connects the second path 53 and the third path 59
3, a third bypass pipe 69 that joins a third coupling pipe 67 that connects the third path 59 and the fourth path 65, and a fourth bypass pipe 71 that joins an outlet of the fourth path 65 are provided.

Next, in the heat exchanger of FIG.
A first bypass pipe 79 that joins a first connection pipe 77 that connects the third path 3 and the second path 75, and a second bypass pipe 8 that joins a second connection pipe 83 that connects the second path 75 and the third path 81
5, a third bypass pipe 91 that joins a third coupling pipe 89 that connects the third path 81 and the fourth path 87 is provided.

Further, in the heat exchanger of FIG.
The first bypass pipe 99 and the first path 9 branch from the first coupling pipe 97 connecting the third path and the second path 95 and join the second coupling pipe 103 connecting the second path 95 and the third path 101.
A second bypass pipe 107 branching from the inlet of the third path and joining the outlet of the fourth path 105 is provided.

In each of these modifications, a plurality of bypass pipes are provided in different modes, respectively, and the average water temperature in the heat absorbing portion is further raised to further improve the tapping property immediately after the tapping. It is also possible to prevent drainage from occurring in the heat absorbing tube.

Next, while comparing the heat exchanger according to the embodiment of the present invention with two types of heat exchangers according to the prior art,
The reason why the heat exchanger according to the embodiment of the present invention is superior to the two types of heat exchangers according to the related art will be described with reference to FIGS. In the following description, for the sake of simplicity, in each of the embodiments and the related art, a heat exchanger in which the number of passes of the heat absorbing tube is “4” will be described as an example.

First, the surface temperature Tw of the heat absorbing tube is obtained by the following equation (2) (see also FIG. 14).

[0048]

(Equation 1) Equation (2) is used to determine the wall temperature (= temperature higher than the dew point of the combustion gas) of the heat absorbing tube that can prevent the generation of drain (water droplets) in the heat absorbing tube.
This equation (2) indicates that the wall temperature of the heat absorption tube rises when the amount of water passing through the heat absorption tube decreases (that is, when the bypass flow rate ratio of the water supply is large), and the wall temperature of the heat absorption tube rises when the hot water temperature is high. Is shown.

Here, the set hot water temperature value (TS) is set to a relatively high temperature of 75 ° C. where the bypass flow ratio cannot be increased, and the feed water temperature value (TC) is set to a relatively low temperature of 5 ° C. where the bypass flow ratio cannot be increased. , The maximum hot water temperature (THmax) in the endothermic tube,
90 ° C that does not cause local boiling in the endothermic tube
, Respectively. These conditions are derived from the fact that so-called temperature control type water heaters are the mainstream in recent years. Then, the bypass flow ratio α to the bypass pipe of the supply water is obtained using the following equation (3), and the hot water temperature in the heat absorbing pipe at the time of tapping at the set hot water temperature of 40 ° C. is calculated using the equation (2) and the like. ,
With reference to FIGS. 15 to 18, the effect in each embodiment and the effect in the above-described related art will be compared. α = 1 − ｛(hot water temperature immediately after merging of bypass water and hot water in heat absorbing pipe−water temperature) / (hot water temperature immediately before merging of bypass water and hot water in heat absorbing pipe−water temperature)…… (3) Here, in each of the heat exchangers shown in FIGS. 15 to 17, the heat absorption rates of all the paths are assumed to be the same (that is, 25%), and the bypassed feed water and the hot water in the heat absorption pipe are connected. Is 90 ° C., and the water temperature (water supply temperature) at point A, which is the branch point between the first path and the bypass pipe, is 5 ° C.

First, in the conventional heat exchanger shown in FIG. 15, if the temperature of the hot water immediately after the merging of the bypassed feed water and the hot water in the heat absorbing tube is set to 75 ° C., the bypass flow ratio α of the bypass pipe 135 becomes (3 ), Α = 1 − ｛(75−5) / (9
0-5)｝ = 0.176. Next, the bypass pipe 13
5 of the hot water supply pipe 137 located downstream from the junction of No. 5
Is 40 ° C., the temperature of the hot water at the point E located on the upstream side of the merging portion of the fourth path 131 is given by E = ｛F (FA) / (1) according to the equation (2). −α)｝ + A = ｛(40
−5) / (1−0.176)｝ + 5 = 47.5 and 4
7.5 ° C.

The temperature of the hot water at the point D of the third connecting pipe 133 connecting the third path 127 and the fourth path 131 is D = E.
− (EA) × 0.25 (= endothermic coefficient) = 47.5− (4
7.5-5) × 0.25 = 36.9, which is 36.9 ° C. The temperature of the hot water at the point C of the second connecting pipe 129 connecting the second path 123 and the third path 127 is C = D− (E−
A) × 0.25 = 36.9− (47.5-5) × 0.2
5 = 26.3, 26.3 ° C. Furthermore, the first pass 1
The temperature of the hot water at the point B of the first connection pipe 125 connecting the first path 21 and the second path 123 is B = C− (E−A) × 0.25 = 2
6.3− (47.5-5) × 0.25 = 15.7 and 1
5.7 ° C. In this way, the hot water temperatures at points B to E are respectively obtained.

Next, in the conventional heat exchanger shown in FIG. 16, the hot water temperature at the point F, which is the outlet of the fourth path 153, is set to 75 ° C.
Then, the temperature of the hot water at the point D of the second coupling pipe 149 located downstream of the junction of the bypass pipe 151 is D = F−
(F−A) × 0.50 = 75− (75−5) = 40,
40 ° C. Since the hot water temperature is the temperature immediately after the bypass water supply and the hot water in the heat absorbing pipe have joined, the bypass flow rate ratio α of the bypass pipe 151 is calculated by the following equation (3).
−5) / (90−5)｝ = 0.59.

Here, assuming that the hot water temperature at point F is set to 40 ° C., the hot water temperature at point E of third connecting pipe 155 connecting third path 147 and fourth path 153 is E = F- (F-
A) × 0.25 = 40− (40−5) × 0.25 = 3
1.3 at 31.3 ° C. The temperature of the hot water at the point D is D = E− (FA) × 0.25 = 31.3− (4
0-5) × 0.25 = 22.6, 22.6 ° C.
Further, the temperature of the hot water at point C located downstream of the second path 143 (= the hot water temperature immediately before the merging of the bypass water and the hot water in the heat absorbing pipe).
Is given by C = ｛(DA) / (1-0.5) according to the equation (2).
9) {+5 = {(22.6-5) / (1-0.59)}
+ 5 = 48 at 48 ° C. Further, the temperature of the hot water at the point B of the first connecting pipe 145 connecting the first path 141 and the second path 143 is B = C− (CA) × 0.5 = 48− (48
−5) × 0.5 = 26.5, which is 26.5 ° C. In this way, the hot water temperatures at points B to E are respectively obtained.

Next, in the heat exchanger according to the embodiment of the present invention shown in FIG. 17, if the hot water temperature at the point G, which is the outlet of the fourth path 173, is 75 ° C., the fourth Pass 17
3 and the bypass flow rate ratio β of the second bypass pipe 177
Is given by equation (3), β = 1 − ｛(75−5) / (90−
5)｝ = 0.176.

The temperature of the hot water at the point D of the second connecting pipe 171 downstream of the junction of the first bypass pipe 167 is
Since the hot water temperature at the point F of the path 173 downstream of the junction of the second bypass pipe 177 is 90 ° C., D = F−
(F−A) × 0.50 = 90− (90−5) × 0.50
= 47.5 and 47.5 ° C. The bypass flow rate ratio α of the first bypass pipe 167 is given by α = 1 according to the equation (3).
-{(47.5-5) / (90-5)} = 0.50.

Here, assuming that the hot water temperature at point G is set to 40 ° C., the hot water temperature at point F is calculated by the following equation (2).
-A) / (1-β)｝ + A = ｛(40-5) / (1-
0.176)｝ + 5 = 47.5, which is 47.5 ° C.
The temperature of the hot water at the point E of the third coupling pipe 175 is E = F−
(FA) x 0.25 = 47.5-(47.5-5) x
0.25 = 36.90, 36.90 ° C. Also,
The hot water temperature at the point D is D = E− (FA) × 0.25 = 3
6.90− (47.5-5) × 0.25 = 26.30
And 26.30 ° C. Also, the point C of the second pass 163
(Part upstream of the junction of the first bypass pipe 167)
The temperature of the hot water is calculated by the equation (2) as C = ｛(DA) / (1-
α)｝ + A = {(26.3-5) / (1-0.50)}
+ 5 = 47.60, which is 47.60 ° C. Furthermore, the first
The hot water temperature at the point B of the coupling pipe 165 is B = C− (CA) ×
0.50 = 47.60− (47.60−5) × 0.50
= 26.3, 26.3 ° C. In this way, the hot water temperatures at points B to F are obtained, respectively. Note that FIG.
, 161 is a first pass, and 169 is a third pass.

Here, when comparing the heat exchanger of the embodiment (FIG. 17) with the heat exchanger of FIG. 15, in the heat exchanger of the embodiment, a part of the first bypass pipe 167 and the second bypass pipe 177 are connected. Although the first path 161 to the fourth path 173 are bypassed, the bypass flow rate ratio is changed as shown in FIG.
Can be set larger than that of the bypass pipe 135. Therefore, in FIG. 18 (where the respective temperature values are plotted), as shown by the straight line 181 and the straight line 183, in the section from the entrance of the third pass to the exit of the fourth pass, the hot water temperature is substantially the same for both, but In the section from the first pass inlet to the second pass outlet, the heat exchanger according to the embodiment has a higher hot water temperature than the heat exchanger in FIG. Therefore, when viewed as a whole, the heat exchanger according to the embodiment can have a higher average water temperature than the heat exchanger of FIG. 15, and particularly, for several minutes (for example, It is possible to improve the tapping property at the time of tapping again after interrupting the use of hot water supply (for 5 minutes) and to further improve the drain prevention effect.

On the other hand, comparing the heat exchanger of the embodiment (FIG. 17) with the heat exchanger of FIG. 16, at least the bypass flow ratio of the first bypass
51, without being much smaller than that of the first bypass pipe 1
67 and the second bypass pipe 177, the first pass 1
61 to the fourth path 173 can be bypassed. Therefore, as shown by the straight line 181 and the straight line 185 in FIG. 18, in the section from the first pass entrance to the second pass exit, the hot water temperature is substantially the same in both sections, but in the section from the third pass entrance to the fourth pass exit. Then, the hot water temperature of the heat exchanger according to the embodiment is higher than that of the heat exchanger of FIG. Therefore, as a whole, as in the above case, the heat exchanger according to the embodiment can have a higher average water temperature than the heat exchanger of FIG. 16, and in particular, because the average water temperature is higher, It is possible to improve the tapping property at the time of tapping again after interrupting the use of hot water supply for several minutes, and to further improve the drain prevention effect.

The above description relates only to one embodiment of the present invention, and does not mean that the present invention is limited to only the above-described content.

[0060]

As described above, according to the present invention,
Prevents a drop in hot water temperature immediately after resuming hot water after interrupting hot water supply, even if a bypass pipe that bypasses a part of the heat absorption pipe for heating feed water does not have a flow control valve that controls the bypass flow rate ratio The heat exchanger of the water heater which can perform the operation can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a state of hot water temperature in each path of a conventional heat exchanger.

FIG. 2 is an explanatory diagram showing a state of hot water temperature in each path of the conventional heat exchanger.

FIG. 3 is a block diagram showing the overall configuration of the water heater of one embodiment.

FIG. 4 is an explanatory diagram showing a detailed configuration of the heat exchanger of FIG. 3;

FIG. 5 is an explanatory diagram showing a positional relationship between a fin and each path.

FIG. 6 is an explanatory diagram showing a positional relationship between a fin and each path.

FIG. 7 is an explanatory diagram showing an average water temperature state and a bypass flow rate ratio in each path.

FIG. 8 is an explanatory diagram showing a state of hot water temperature in each pass of the embodiment.

FIG. 9 is an explanatory diagram showing a detailed configuration of a heat exchanger according to another embodiment.

FIG. 10 is an explanatory diagram showing a state of hot water temperature in each pass of another embodiment.

FIG. 11 is a diagram showing a heat exchanger of a first modified example of another embodiment.

FIG. 12 is a diagram showing a heat exchanger of a second modified example of another embodiment.

FIG. 13 is a diagram showing a heat exchanger according to a third modification of the other embodiment.

FIG. 14 is an explanatory diagram relating to a formula for obtaining a surface temperature of a heat absorbing tube.

FIG. 15 is a diagram showing a configuration of a conventional heat exchanger.

FIG. 16 is a diagram showing a configuration of a conventional heat exchanger.

FIG. 17 is a diagram showing a configuration of a heat exchanger of the embodiment.

FIG. 18 is a diagram comparing the hot water temperature in each pass between the embodiment and the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water supply pipe 7 Heat exchanger 9 Hot water supply pipe 11 Heat absorption part 12 1st path 13 Heat absorption pipe 14 2nd path 15 Fin 16 Third path 17 Bypass pipe 18 4th path 20 5th path 22 6th path 24 1st connection pipe 26 second connecting pipe 28 third connecting pipe 30 fourth connecting pipe 32 fifth connecting pipe

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kiyotaka Nakano 431-1 Uozakihama-cho, Higashi-Nada-ku, Kobe-shi, Hyogo Prefecture Inside Nippon Yupro Co., Ltd. Inside Nippon Yupro Co., Ltd. (72) Inventor Hiroki Maruyama 43-1, Uozakihama-cho, Higashinada-ku, Kobe-city, Hyogo Prefecture Inside (72) Inventor Takayuki Otani 43-1 Uozakihama-cho, Higashinada-ku, Kobe-shi, Hyogo Japan Nippon Yupro Incorporated (56) References Hikaru 5-52654 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F24H 1/14 F24H 9/00 F24H 1/10 302

Claims (3)

(57) [Claims] 1. A heat exchanger for a water heater, comprising: a heat absorbing tube having a starting end connected to a water supply pipe and an end connected to a tapping pipe and formed as a whole as one water passage. A first bypass pipe connecting the water supply pipe and a specific location of the heat absorption pipe; and a second bypass pipe connecting the water supply pipe and a location upstream of the specific location of the heat absorption pipe. The specific location is a position on the upstream side of the end of the heat absorption tube, and the amount of heat absorbed from the start end of the heat absorption tube to the specific location is between the specific location and the end of the heat absorption tube. The heat exchanger of the water heater where the amount of heat absorbed is greater. 2. The heat exchanger for a water heater according to claim 1, wherein the heat absorbing tube has a smaller internal diameter on the upstream side than the specific location on the downstream side. 3. The heat exchanger of a water heater according to claim 1, wherein a flow rate of the first bypass pipe is equal to or less than a flow rate of a portion of the heat absorption pipe upstream of the specific location. As described above, the heat exchanger of the water heater in which the inner diameter of the first bypass pipe is selected.