JP2002071215A - High-efficiency water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively recover latent heat without raising the internal pressure of a combustion chamber. SOLUTION: In the combustion chamber 2, two heat exchangers of a main heat exchanger 8 and an auxiliary heat exchanger 9 are provided, and a fan 10 which sucks combustion air into the combustion chamber 2 from an air supplying opening 11 and discharges the air in the chamber 2 to the outside of a water heater through a discharge port 12 is provided on the exhaust-side downstream side of the auxiliary heat exchanger 9. The heat exchanger 9 is composed of a liquid tank 14 used for storing water, an exhaust air passage 15 which connects the inside of the tank 14 to the fan 10, an introducing pipe 16 the front end section of which has a plurality of small holes and positioned in the tank 14, and a heat-exchanger pipe 17 dipped in the water of the tank 14 and connected to a water supply pipe 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater for heating water using a burner, and more particularly to a high-efficiency water heater with improved thermal efficiency.

[0002]

2. Description of the Related Art A high-efficiency water heater is known which utilizes latent heat of combustion gas in order to improve the heat efficiency of a heat exchanger. For example, in Japanese Patent No. 3041976, an indirect heat exchanger for indirectly exchanging heat between combustion gas and water that is forcibly exhausted by a fan is provided, while the combustion gas is disposed downstream of the exhaust gas in the combustion gas. A direct heat exchanger that sprays water to directly exchange heat between the combustion gas and water, and a hot water and water indirectly in a water reservoir that is located directly below the heat exchanger and stores the sprayed hot water. A water heat exchanger for heat exchange is provided, the latent heat of the steam in the combustion gas is recovered by the direct heat exchanger, the water is preheated by the water heat exchanger, and then the combustion gas is recovered by the indirect heat exchanger. An invention of a water heater for heating water with sensible heat is disclosed. Similarly, in JP-A-59-125350, the latent heat is recovered by passing a combustion gas through a liquid tank provided with water as a main component downstream of the exhaust side of the indirect heat exchanger and provided in the liquid tank. The invention of a water heater provided with a liquid-liquid heat exchanger for preheating water with a heat exchange pipe is disclosed.

[0003]

The invention of the former publication is
Since the heat exchange is performed by spraying water, the heat exchange is insufficient and efficient latent heat recovery cannot be performed. In addition, since all the spray water is drained, the amount of waste water increases. On the other hand, in the invention of the latter publication, the efficiency of latent heat recovery and the generation of waste water can be reduced by the liquid-liquid heat exchanger using the liquid tank, but the fan for supplying the combustion air requires an indirect heat exchange. Since it is a so-called push type located on the upstream side of the vessel, the internal pressure of the combustion chamber increases due to the passage of the combustion gas into the liquid tank, and the combustion gas may leak. Also, due to the recovery of latent heat, the effluent that overflows from the liquid tank will be drained, but this effluent cannot be directly discharged to sewage due to its strong acidity. Requires a neutralization device for neutralization.

Accordingly, the invention according to claim 1 provides a liquid-liquid heat exchanger that utilizes a liquid tank, while maintaining efficient latent heat recovery, while using a liquid-liquid heat exchanger to maintain the internal pressure of the combustion chamber. It is an object of the present invention to provide a high-efficiency water heater that does not cause a risk of combustion gas leakage due to rising. on the other hand,
According to the fifth aspect of the present invention, in order to recover the latent heat of the combustion gas, an additional device such as a liquid-liquid heat exchanger is required in addition to the indirect heat exchanger as described in the above two publications, leading to an increase in cost. Therefore, it is an object of the present invention to provide a high-efficiency water heater that can increase thermal efficiency with a simple configuration without using these additional devices.

[0005]

In order to achieve the above object, the present invention is directed to a main heat exchanger for indirectly exchanging heat between combustion gas and water in a combustion chamber provided with a burner. And a downstream side of the main heat exchanger on the exhaust side thereof has a liquid tank through which a combustion gas passes, and an auxiliary heat exchanger that exchanges heat between the liquid tank and water supplied to the main heat exchanger, and a combustion chamber. , A high-efficiency water heater is provided downstream of the auxiliary heat exchanger on the exhaust side and provided with a fan that sucks and exhausts combustion air from a burner in the combustion chamber. The invention according to claim 2 provides the liquid tank with a simple structure for neutralizing the pH value of the effluent from the liquid tank without using a neutralization device. An overflow pipe for draining a liquid exceeding a predetermined water level is provided, and the waste water in the overflow pipe is mixed with the waste water discharged to the hot water supply point via the main heat exchanger. According to the third aspect of the present invention, in addition to the object of the first or second aspect, in order to surely neutralize the effluent from the liquid tank, the overflow pipe is neutralized to neutralize wastewater in the overflow pipe. A device is provided. The invention described in claim 4 provides, in addition to the object of any of claims 1 to 3,
In order to obtain higher thermal efficiency, the intake port of the combustion air supplied to the combustion chamber is arranged near the exhaust port provided downstream of the exhaust side of the fan, and the combustion gas passing through the combustion chamber and the exhaust port is arranged. Thus, the combustion air passing through the air supply path and the air supply port can be preheated.

According to a fifth aspect of the present invention, a combustion chamber provided with a burner is provided with an air supply port through which combustion air is sucked by a fan, and combustion gas is discharged from the combustion chamber. The combustion gas passing through the combustion chamber and the exhaust port can be preheated by the combustion gas passing through the combustion chamber and the exhaust port.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a high-efficiency water heater (hereinafter, referred to as “water heater”) 1, and burner units (hereinafter, referred to as “units”) 3, 3 are provided in a combustion chamber 2. Each unit 3 is connected to each unit 3,
Branch pipes 5 and 5 branching to 3 are connected, and a switching solenoid valve 6 is provided for each branch pipe 5. Reference numeral 7 denotes a proportional valve provided on the gas pipe 4 before branching. In the combustion chamber 2, a main heat exchanger 8 serving as a sensible heat recovery unit for the combustion gas, and an auxiliary heat exchanger 9 serving as a latent heat recovery unit for the combustion gas downstream of the main heat exchanger 8 on the exhaust side. And a fan 10 that sucks combustion air into the combustion chamber 2 and discharges the air to the outside of the water heater, downstream of the auxiliary heat exchanger 9 on the exhaust side. 11 is an air supply port formed in the housing of the water heater 1;
Reference numeral 12 denotes an exhaust port, and here, an air supply port 11 is provided near the exhaust port 12. Therefore, the combustion air taken in from the air supply port 11 is sucked into the combustion chamber 2 from below the combustion chamber 2 via the air supply path 11a adjacent to the combustion chamber 2 as shown by a solid arrow, and Although it is spent on the combustion of the unit 3, since the air supply port 11 is near the exhaust port 12,
The combustion air is heat-exchanged (preheated) with the combustion gas while passing through the outer periphery of the combustion chamber 2.

On the other hand, a water supply pipe 13 connected to the water heater 1
Is first connected to the auxiliary heat exchanger 9. Auxiliary heat exchanger 9
A liquid tank 14 in which water is stored, an exhaust passage 15 connecting the inside of the liquid tank 14 and the fan 10 with an opening smaller than the bottom area of the liquid tank 14, and a base end opened in the combustion chamber 2; An introduction pipe 16 having a tip portion having a small hole formed in the liquid tank 14.
And a heat exchange pipe 17 immersed in the liquid tank 14, and the water supply pipe 13 is connected to the heat exchange pipe 17.
Further, an overflow pipe 18 whose tip is located near the upper surface of the liquid tank 14 is connected to the liquid tank 14, and water that exceeds a predetermined water level of the liquid tank 14 is supplied to the outside of the water heater 1 through the overflow pipe 18. The water is drained to the water pipe 33. 1
Reference numeral 9 denotes a water refill pipe branched from the water supply pipe 13 and connected to the liquid tank 14, and is provided with a water refill valve 20. The heat exchange pipe 17 of the auxiliary heat exchanger 9 is connected to the relay pipe 21 at the outlet of the liquid tank 14, and the relay pipe 21 is connected to the heat absorbing pipe 22 of the main heat exchanger 8. The heat absorbing tube 22 has a fin 2
Are provided, and are connected to the tapping pipe 24 on the tapping side of the main heat exchanger 8 and are guided to the outside of the water heater 1. 25 is a relay pipe 21 bypassing the main heat exchanger 8.
And a bypass pipe connected to the tapping pipe 24.

Further, the tapping pipe 24 branches to a predetermined hot water supply location and is opened and closed by hot water taps 26, 26, respectively.
Here, since the drain pipes 27, 27,... Of each hot water supply place are all connected to the overflow pipe 18, the waste water of each hot water supply place is mixed with the waste water of the overflow pipe 18 and flows to the sewer pipe 33. Will be. On the other hand, water supply pipe 13
Includes a water amount sensor 28 for detecting an amount of water flowing in the water supply pipe 13 and an incoming water temperature thermistor 29 for detecting an incoming water temperature.
The tapping pipe 24 is provided with a heat exchanger thermistor 30 for detecting the temperature of the inner body outlet of the main heat exchanger 8 and a tapping temperature thermistor 31 for detecting the tapping temperature downstream thereof.
Reference numeral 32 denotes a controller (indicated as "BC" in the figure), which receives a water amount detection signal from the water amount sensor 28 and a temperature detection signal from each thermistor, respectively. The amount of combustion output required for tapping at the set temperature is calculated from the temperature, and based on the calculation result, the opening degree control of the proportional valve 7 and the combustion control of each unit 3 by opening and closing the switching solenoid valves 6 and 6 are executed. , The number of rotations of the fan 10 is controlled.

In the water heater 1 configured as described above, when one of the hot water taps 26 is opened and water flows through the water supply pipe 13, the controller detects the amount of water by the water amount sensor 28. 32 burns units 3,3. The high-temperature combustion gas generated by the combustion of the units 3 and 3 first passes between the fins 23 of the main heat exchanger 8 to heat the water in the heat absorbing tube 22. Then, as shown by the dotted arrow, the combustion gas enters the liquid tank 14 via the introduction pipe 16 of the auxiliary heat exchanger 9 on the downstream side thereof, and passes through the liquid tank 14 as bubbles. At this time, when the liquid temperature is lower than the dew point, the H ₂ O vapor in the combustion gas generates latent heat to become water and is taken into the water, so that the water in the liquid tank 14 is heated. Therefore, the combustion gas becomes substantially equal to the liquid temperature, and is discharged from the exhaust passage 15 to the outside through the exhaust port 12 through the fan 10. Therefore, the water guided from the water supply pipe 13 into the water heater 1 exchanges heat with the water in the liquid tank 14 heated by the latent heat of the combustion gas when passing through the heat exchange pipe 17 of the auxiliary heat exchanger 9. As a result, preheating is given, and thereafter, the main heat exchanger 8 is heated by heat exchange with the high-temperature combustion gas, and is discharged as hot water from the tapping pipe 24.

As the temperature in the liquid tank 14 increases, the preheating of the water in the heat exchange pipe 17 increases accordingly.
If the temperature in the liquid tank 14 is too high and exceeds the dew point of the combustion gas, the latent heat of the combustion gas cannot be recovered, so the controller 32 controls the liquid tank thermistor 35 provided in the liquid tank 14.
Rehydration valve 20 based on the temperature detection signal obtained from
Is controlled to adjust the water temperature in the liquid tank 14. FIG.
In the graph showing the relationship between the excess air ratio (λ) and the dew point for each gas type, (A) shows an air supply temperature of 15 ° C. and a humidity of 60%, and (B) shows an air supply temperature of 30 ° C. and a humidity of 90%. %, For example, in propane (indicated by "P") or butane (indicated by "B"), an excess air ratio of 1.0
Condensation will occur below ℃. That is, the temperature in the liquid tank 14 is adjusted so that the water temperature in the liquid tank 14 becomes lower than the dew point of the combustion gas.

Then, H in the combustion gas is₂O
When the amount of water in the liquid tank 14 increases due to water
It is discharged from the flow tube 18. At this time,
NO _X, CO₂Etc. are dissolved in the liquid tank 14 and discharged.
The solution becomes strongly acidic (pH 3-5), but the overflow tube
Since a drain pipe 27 is connected to 18, the water heater 1
When using, all the hot water used at the hot water supply point is drained
The effluent is diluted to pH 5 or more.
As a pH value within the effluent standard value specified by the ordinance, etc.
It can be discharged to the water pipe 33. Specifically, gas input
In a 30000 kcal / hr water heater, 13A (natural
Gas) generates 4.88 kg / hr of drainage and pH 3
It is about the extent, but the water of 5 ° C is turned to 60 ° C by the water heater 1
In this case, the amount of water used is 545 kg / hr and the amount of drain
A place where water of 20 degrees Celsius is turned 45 degrees Celsius, 112 times of
In this case, the amount of water used is 1200 kg / hr,
6 times. To dilute the drain with this amount of waste water,
Does not fall below 5. In addition, the numerical value here
Is calculated based on thermal efficiency of 100%.
Becomes 95% or less, and the amount of latent heat and drain generation decreases.
Therefore, the pH value is on the safer side.

As described above, according to the water heater 1 of the above embodiment,
By employing an auxiliary heat exchanger 9 for direct liquid-liquid heat exchange in addition to the conventional main heat exchanger 8, the sensible heat and latent heat of the combustion gas are effectively recovered to increase the thermal efficiency. be able to. In particular, since the fan 10 for taking in the combustion air is of a suction type arranged downstream of the auxiliary heat exchanger 9 on the exhaust side, there is no danger that the combustion chamber 2 becomes negative pressure and the combustion gas leaks. Since the low-temperature combustion gas after recovery is exhausted, forced exhaustion by suction can be realized even if the fan 10 is small in size, as compared with the suction type in which the auxiliary heat exchanger 9 is not used. The size and cost of the container 1 can be reduced.

Here, the air supply port 11 is provided near the exhaust port 12, and the combustion gas passing through the combustion chamber 2 and the exhaust port 12 is used for combustion air passing through the air supply port 11 and the air supply path 11 a. Can be preheated, the thermal efficiency can be further improved with a simple configuration, and the heat radiation of the casing of the water heater 1 can be reduced. In particular, when the water heater 1 is installed outdoors, it is difficult to receive the back pressure due to the wind, and the air supply port 11 and the exhaust port 12 have the same pressure. The effect of further reducing the size of the device 10 is also obtained. Furthermore, since the discharged liquid discharged from the overflow pipe 18 of the liquid tank 14 is mixed with hot water discharged at the hot water supply point and discharged, the liquid tank 14 can be easily discharged from the liquid tank 14 without using a neutralizing device. The highly acidic effluent can be adjusted to an appropriate pH value and drained to sewage.

In the above embodiment, the overflow pipe 18
Of the effluent from the liquid tank 14 by connecting the
Although the H value is adjusted, as shown by a two-dot chain line in FIG. 1, a neutralization device 34 using granular calcium carbonate or the like as a neutralizing agent is provided in the overflow pipe 18, and the discharged liquid is discharged from the overflow pipe 18. Can be neutralized. In this way, even when the hot water supply location is a bathtub or the like and the hot water is not drained as it is, the discharged water can be reliably neutralized. Also, if the auxiliary heat exchanger 9 is also in a form in which liquid-liquid direct heat exchange can be performed in a suction type exhaust form, the shapes of the exhaust passage 15, the introduction pipe 16, the heat exchange pipe 17, and the like can be appropriately changed. For example, instead of making the outlet of the introduction pipe a small hole, a punching metal or the like may be provided in the liquid tank 14 to divide the bubbles. Further, even in a water heater provided with only the main heat exchanger 8 without using the auxiliary heat exchanger 9, if the air supply port 11 is arranged near the exhaust port 12 as in the above embodiment, the combustion gas Even if the latent heat recovery is not performed, it is possible to improve thermal efficiency by preheating the combustion air, which leads to cost reduction.

[0016]

According to the first aspect of the present invention, in addition to the conventional main heat exchanger, the auxiliary heat exchanger for direct liquid-liquid heat exchange is employed, so that the sensible heat of the combustion gas is obtained. And latent heat can be effectively recovered to increase thermal efficiency. In particular, since the fan that takes in the combustion air is a suction type that is located downstream of the auxiliary heat exchanger on the exhaust side, there is no danger of the combustion chamber becoming negative pressure and leakage of the combustion gas, and the low temperature after the latent heat is recovered. Therefore, even if the fan is small, forced exhaust by suction can be realized, and the water heater can be made compact and cost can be reduced. According to the second aspect of the present invention, in addition to the effect of the first aspect, the liquid tank is provided with an overflow pipe for draining a liquid exceeding a predetermined water level, and the drainage in the overflow pipe is passed through the main heat exchanger. By adopting a configuration in which the waste water discharged to the hot water supply location is mixed, the discharged liquid from the liquid tank can be neutralized with a simple configuration without using a neutralization device. According to the invention set forth in claim 3, in addition to the effect of claim 1 or 2, the hot water supply point is a bathtub or the like by providing the overflow pipe with a neutralization device for neutralizing wastewater in the overflow pipe. Even when the discharged hot water is not drained as it is, the discharged liquid can be reliably neutralized. According to the fourth aspect of the invention, in addition to the effects of any one of the first to third aspects, the air supply port to the combustion chamber is arranged near the exhaust port, and passes through the combustion chamber and the exhaust port. By making it possible to preheat the combustion air passing through the air supply path and air supply port with the combustion gas, the thermal efficiency can be further improved with a simple configuration,
The heat radiation of the water heater casing is also reduced. In addition, when the water heater is installed outdoors, it is difficult to receive the back pressure due to the wind, and the air supply port and the exhaust port have the same pressure, so that the load on the fan is reduced, and the size of the fan is reduced accordingly. The effect of being achieved is also obtained.

According to the fifth aspect of the present invention, in the combustion chamber having the burner, the air supply port through which the combustion air is sucked by the fan is provided in the vicinity of the exhaust port through which the combustion gas is discharged from the combustion chamber. By arranging and preheating the combustion air passing through the air supply path and the air supply port by the combustion gas passing through the combustion chamber and the exhaust port, it can be simplified without using an auxiliary heat exchanger for latent heat recovery. With the configuration, the thermal efficiency is improved, which leads to cost reduction and also reduces heat radiation of the casing of the water heater. In addition, when the water heater is installed outdoors, it is difficult to receive the back pressure due to the wind, and the air supply port and the exhaust port have the same pressure, so that the load on the fan is reduced, and the size of the fan is reduced accordingly. The effect of being achieved is also obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a water heater.

FIG. 2A is a graph showing a relationship between an excess air ratio and a dew point. (B) is a graph showing the relationship between the excess air ratio and the dew point.

[Explanation of symbols]

1. hot water heater, 2. combustion chamber, 8. main heat exchanger, 9.
・ Auxiliary heat exchanger, 10 ・ ・ Fan, 11 ・ ・ Air supply port, 1
2 ··· Exhaust port, 13 ··· Water supply pipe, 14 ··· Liquid tank, 15 ·
・ Exhaust passage, 16 ・ ・ Introduction pipe, 17 ・ ・ Heat exchange pipe, 18 ・ ・ Overflow pipe, 24 ・ ・ Hot water pipe, 27
..Drain pipe, 32..controller, 33..sewer pipe.

Claims (5)

[Claims] A main heat exchanger for indirectly exchanging heat between combustion gas and water is provided in a combustion chamber provided with a burner, and a liquid for passing the combustion gas is provided downstream of the main heat exchanger on the exhaust side. An auxiliary heat exchanger for exchanging heat between the liquid tank and water supplied to the main heat exchanger, and the burner is provided in the combustion chamber downstream of the auxiliary heat exchanger in the combustion chamber on the exhaust side. A high-efficiency water heater equipped with a fan that sucks and exhausts combustion air. 2. The liquid tank according to claim 1, wherein an overflow pipe for draining a liquid exceeding a predetermined water level is provided, and the wastewater in the overflow pipe is mixed with wastewater discharged to a hot water supply point via a main heat exchanger. High efficiency water heater described. 3. The high-efficiency water heater according to claim 1, wherein the overflow pipe is provided with a neutralizing device for neutralizing wastewater in the overflow pipe. 4. An air supply port for combustion air supplied to a combustion chamber is disposed near an exhaust port provided on the exhaust side downstream of a fan, and a combustion gas passing through the combustion chamber and the exhaust port is provided. The high-efficiency water heater according to any one of claims 1 to 3, wherein the combustion air passing through the air supply path and the air supply port can be preheated. 5. A combustion chamber provided with a burner, wherein an air supply port through which combustion air is sucked by a fan is disposed near an exhaust port from which combustion gas is discharged from the combustion chamber, and the combustion chamber and A high-efficiency water heater capable of preheating an air supply path and combustion air passing through the air supply port by the combustion gas passing through the exhaust port.