JP2005069665A - Water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly-efficient water heater requiring no neutralization processing of drain water. <P>SOLUTION: A passage of combustion exhaust gas passing through a main heat exchanger 18 is formed to be branched into a first exhaust gas chamber 23 provided with a sub heat exchanger 19 and a second exhaust gas chamber 24 provided with a drain evaporator. Accordingly, the sub heat exchanger 19 and a drain evaporator 100 are provided with high temperature the combustion exhaust passing only through the main heat exchanger 18. Due to this, heat collection is efficiently conducted using combustion exhaust gas having a high temperature in the sub heat exchanger 19, while drain evaporation is efficiently conducted using combustion exhaust gas having a high temperature in a drain evaporator 100. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a water heater provided with a heat exchanger that heats water through combustion exhaust.

2. Description of the Related Art Conventionally, in the field of water heaters, there are known water heaters including a heat exchanger to which a water supply pipe and a hot water discharge pipe are connected, a burner for heating the heat exchanger, and a fan for supplying combustion air to the burner. It has been.
Such a water heater is configured to heat the water in the heat exchanger with the combustion exhaust heat of combustion in the burner and supply hot water from the hot water outlet pipe.

By the way, in such a water heater, in order to prevent drain from being generated in the heat exchanger, high-temperature exhaust gas must be discharged without sufficient heat recovery in the heat exchanger, and a high heat exchange rate Is not obtained.
Since the drain is generated when the combustion exhaust becomes a dew point (approximately 50 to 60 ° C.) or lower, in principle, heat is exchanged to the dew point with a heat exchanger, and the sensible gas in the combustion exhaust is not generated without generating a drain. It is possible to recover heat. However, since the heat exchanger has a local low temperature part such as a heat transfer tube that is a water flow part, the exhaust gas is actually heated at a considerably high temperature in order to prevent partial drain generation in the low temperature part. It must be discharged, and sufficient sensible heat cannot be recovered.

In order to improve the recovery efficiency of combustion exhaust heat (hereinafter referred to as thermal efficiency), there is a latent heat recovery type water heater that recovers not only sensible heat of combustion exhaust heat but also latent heat by condensing water vapor in the combustion exhaust. .
The latent heat recovery type water heater is provided with a main heat exchanger mainly for the purpose of recovering sensible heat on the upstream side of the combustion exhaust passage and a sub heat exchanger mainly for the purpose of recovering latent heat on the downstream side. .
Such a latent heat recovery type water heater recovers most of the heat energy in the combustion exhaust because the sub heat exchanger recovers the latent heat in the combustion exhaust that could not be recovered by the main heat exchanger.
However, in the above-described latent heat recovery type water heater, water vapor (hereinafter referred to as drain) condensed in the process of latent heat recovery reacts with sulfur oxides (SOx) and nitrogen oxides (NOx) in the combustion exhaust gas and becomes acidic. Since it becomes (about pH 3), it must be neutralized before it is discharged into a general drainage passage such as sewage.
Therefore, in the conventional latent heat recovery type water heater, as shown in Patent Document 1, it is necessary to provide a neutralizing device for drain neutralization, which is extremely expensive. In addition, the neutralizing agent used in the neutralizing apparatus needs to be replaced at regular intervals, which is a burden on the user.

Therefore, recently, as shown in Patent Document 2, there has been proposed a water heater that evaporates the drain generated in the auxiliary heat exchanger by bringing it into contact with the combustion exhaust gas.
This water heater includes a main heat exchanger, a sub heat exchanger, and a drain evaporator in the same combustion exhaust flow path, collects sensible heat in the combustion exhaust heat in the main heat exchanger, and drains in the sub heat exchanger. The latent heat and the sensible heat that could not be recovered by the auxiliary heat exchanger are recovered, and in the drain evaporator, the drain generated by the auxiliary heat exchanger is evaporated using the combustion exhaust heat. Such a water heater needs to be the most upstream of the combustion exhaust flow path in the main heat exchanger that recovers sensible heat, but either the auxiliary heat exchanger or the drain evaporator is provided upstream. Also good.
According to this water heater, since the same amount of heat as the latent heat recovered in the auxiliary heat exchanger is used for drain evaporation, the latent heat is not recovered as a result, but in the auxiliary heat exchanger, Combustion exhaust heat can be recovered by lowering the temperature of the combustion exhaust to the dew point temperature or lower. In other words, in the auxiliary heat exchanger, it is not necessary to keep the combustion exhaust heat unnecessarily high in order to prevent the generation of drainage, and it is possible to obtain a higher recovery rate for sensible heat than in a normal water heater.
In addition, in this case, it is not necessary to provide a drain neutralizer and the cost is low.
JP 2002-195645 A JP2002-98413

  However, in the above prior art, since the auxiliary heat exchanger and the drain evaporator are provided in the same exhaust flow path, there are the following problems.

First, when the drain evaporator is provided downstream of the auxiliary heat exchanger, the most of the combustion exhaust heat reaches the drain evaporator by the main heat exchanger and the auxiliary heat exchanger. It will be collected. As the temperature of the combustion exhaust gas decreases, the saturation humidity of the combustion exhaust gas decreases and becomes close to the actual humidity. In general, however, the evaporation rate R [kg / hr · m3] is known to be proportional to the difference between the saturation humidity Hw [kg / kg] of air and the actual humidity H [kg / kg], as shown by the following equation, and combustion having a humidity close to saturation humidity Even if exhaust and drain are brought into contact with each other, the drain does not readily evaporate.
(Evaporation rate R) = (constant k) × ((saturated humidity Hw) − (actual humidity H))
Therefore, in the above case, in order to completely evaporate the collected drain, it is necessary to bother limiting the recovery rate of the combustion exhaust heat in the heat exchanger.

Further, when the drain evaporator is provided upstream of the combustion exhaust passage from the auxiliary heat exchanger, the heat energy of the combustion exhaust is changed from a liquid to a gas in the drain evaporator before reaching the auxiliary heat exchanger. It will be used when converting to. In other words, since the heat energy of the combustion exhaust gas is converted into the latent heat of the gas, the temperature of the combustion exhaust gas reaching the sub heat exchanger is lowered, but in general, the heat in the case of no state change (sensible heat recovery) The exchange rate is proportional to the difference between the combustion exhaust heat and the heat transfer tube temperature.
Therefore, the sensible heat recovery rate decreases as the temperature of the combustion exhaust gas in the auxiliary heat exchanger decreases.

The water heater according to claim 1 of the present invention for solving the above-mentioned problems is
A burner that burns fuel in the combustion chamber;
A main heat exchanger that recovers sensible heat from the combustion exhaust of the burner to heat the water flow in the heat transfer tube;
A sub heat exchanger that recovers latent heat in addition to sensible heat that could not be recovered by the main heat exchanger from the combustion exhaust that has passed through the main heat exchanger, and heats the water in the heat transfer tubes, and the sub heat A drain evaporator that heats and evaporates the drain generated by the recovery of latent heat in the exchanger;
In the water heater with
The gist is that the auxiliary heat exchanger and the drain evaporator are arranged in parallel in the exhaust passage of the combustion exhaust that has passed through the main heat exchanger so as not to be in an upstream / downstream relationship in the exhaust passage.

In the hot water heater according to claim 1 of the present invention having the above-described configuration, the auxiliary heat exchanger and the drain evaporator are not connected to each other upstream and downstream in the exhaust passage in the passage of the combustion exhaust that has passed through the main heat exchanger. Since they are arranged in parallel, high-temperature combustion exhaust gas that has passed through only the main heat exchanger is supplied to the auxiliary heat exchanger and the drain evaporator.
For this reason, in the auxiliary heat exchanger, heat recovery is efficiently performed using high-temperature combustion exhaust gas, and in the drain evaporator, drain evaporation is efficiently performed using high-temperature combustion exhaust gas.
In other words, in the secondary heat exchanger that performs heat exchange between the combustion exhaust and the secondary heat transfer tube, it is desirable to supply high-temperature combustion exhaust from the viewpoint of heat transfer speed, and drain is used to utilize the heat of the combustion exhaust. Also in the drain evaporator to be evaporated, it is desirable to supply high-temperature combustion exhaust gas having a high evaporation capability. However, in the present invention, high-temperature combustion exhaust gas can be supplied to both the auxiliary heat exchanger and the drain evaporator. .
Accordingly, the drain evaporator can efficiently evaporate the drain using the high-temperature combustion exhaust gas, and the auxiliary heat exchanger can recover the combustion exhaust heat more efficiently than the high-temperature combustion exhaust gas.

  In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the water heater of the present invention will be described below.

  As shown in FIG. 1, the water heater of this embodiment is provided with a combustion chamber 20 in the appliance casing 12, and an air supply fan 36 connected to a DC motor 48 is attached below the combustion chamber 20. The appliance casing 12 has an air supply port 30 for taking outside air as combustion air.

In the combustion chamber 20, in order from the bottom, a burner 22 that combusts a mixed gas of fuel gas and primary air from the air supply fan 36, and main heat exchange that recovers most of the sensible heat of the combustion exhaust from the burner 22. A vessel 18 is provided. Above the main heat exchanger 18 is formed a high temperature exhaust chamber 21 through which still high-temperature exhaust gas that has passed through the main heat exchanger 18 flows. A first exhaust chamber 23 and a second exhaust gas are disposed on the side of the high temperature exhaust chamber 21. A chamber 24 is provided to branch up and down. The first exhaust chamber 23 and the second exhaust chamber 24 form independent exhaust passages by an exhaust branching portion 200 provided on the middle side of the high-temperature exhaust chamber, and further, upstream and downstream of each other in the exhaust passage. Arranged in parallel so as not to be related.
The first exhaust chamber 23 is provided with a sub heat exchanger 19 that recovers sensible heat and latent heat that could not be recovered by the main heat exchanger 18.
The second exhaust chamber 24 is provided with a drain evaporator 100 that heats and evaporates the drain generated in the auxiliary heat exchanger 19.
In this way, in the exhaust passage of the exhaust gas that has passed through the main heat exchanger 18, the sub heat exchanger 19 and the drain evaporator 100 are arranged in parallel so as not to have an upstream / downstream relationship with each other.
Further, the exhaust branching unit 200 includes a plurality of burring holes 202a for guiding the drain generated in the auxiliary heat exchanger 19 to the drain evaporator 100. Details of the exhaust branching unit 200 will be described later.

Exhaust ports 44 a and 44 b are formed on the sides of the first exhaust chamber 23 and the second exhaust chamber 24 to discharge the combustion exhaust after heat exchange to the outside of the combustion chamber 20, respectively.
These exhaust ports 44a and 44b respectively face the device exhaust ports opened in the device casing 12.

  The water pipes provided in the appliance casing 12 are, in order from the upstream, the water supply pipe 14 wound around the combustion chamber 20 on the outside, the auxiliary heat transfer pipe 19a provided in the auxiliary heat exchanger 19, and the main heat exchanger 18 provided. These are the heat transfer pipe 18 a and the hot water discharge pipe 16.

The water supply pipe 14 is provided with a water side control unit 50 including a water flow sensor and a water governor.
The auxiliary heat transfer pipe 19a is made of stainless steel and collects the exhaust heat of the combustion exhaust gas that has passed through the main heat exchanger 18 and has a number of fins 19b that guide the generated drain to the exhaust branching section 200 to be described later. Prepare.
The main heat transfer tube 18a includes a number of heat recovery fins 18b that absorb combustion heat in the depth direction.

Next, the exhaust branch part 200 and the drain evaporator 100 will be described.
The exhaust branching unit 200 is provided directly below the auxiliary heat exchanger 19, branches the combustion exhaust gas that has passed through the main heat exchanger 18, guides it to the auxiliary heat exchanger 19 and the drain evaporator 100, and also uses the auxiliary heat exchanger. The drain generated at 19 is recovered.
As shown in FIG. 3, the exhaust branching unit 200 is formed by bending a single stainless steel plate, and a drainage recovery unit that recovers the drain generated in the casing fixing unit 201 fixed to the instrument casing 12 and the auxiliary heat exchanger 19. Unit 202.
A screw hole 201a is formed in the casing fixing portion 201 and is fixed to the instrument casing 12 with a stainless steel screw.
The drain collecting unit 202 is provided with a plurality of burring holes 202a.
At both ends of the drain collecting unit 202, as shown in FIG. 3, a drop preventing unit 204 for preventing the drain from falling is formed.

The drain evaporator 100 includes a drain evaporator 101 that evaporates the collected drain and a drain evaporator fixing unit 110 that is fixed to the combustion chamber 20.
The drain evaporation part 101 is comprised from the ceramic board which has drain resistance, heat resistance, and hydrophilicity.
As shown in FIG. 2, the drain evaporator fixing part 110 is made of a single stainless steel plate, and includes a combustion chamber fixing part 111 that is fixed to the combustion chamber, a fixing part 112 that sandwiches and fixes the drain evaporation part 101, and a drain It comprises a support portion 113 on which the evaporation portion 101 is placed and supported, and a drain fall prevention portion 114 that prevents the drain from falling.
A screw hole 111a is formed in the combustion chamber fixing portion 111 and is fixed to the combustion chamber 20 with a stainless steel screw.
The fixing portion 112 is formed in a U shape at both ends of the support portion 113.
As shown in FIG. 1, the support portion 113 is provided so as to form an inclination of about 10 ° with respect to the combustion chamber 20.
As shown in FIG. 1, the drain fall prevention unit 114 is formed with an inclination of about 10 ° so as to become higher toward the exhaust port 44b in order to prevent the drain from dropping out of the appliance.

When the drain generated in the auxiliary heat exchanger 19 is transferred to the drain recovery unit 202 through the fins 19b, the drain is transferred to the drain evaporation unit 101 through the burring hole 202a.
Since the drain evaporation part 101 is a hydrophilic porous ceramic, the dropped drain diffuses throughout the drain evaporation part 101.

Next, the operation of the water heater 10 configured as described above will be briefly described.
When a hot water tap (not shown) is opened, water (broken arrow in the figure) flows through the water supply pipe 14, and the burner controller 58 drives the air supply fan 36 by a detection signal from the water flow sensor in the water side control unit 50. The main solenoid valve 54 and the gas proportional valve 56 are opened to ignite the burner 22.
When the ignition operation is completed, the gas proportional valve 56 is controlled according to the difference between the tapping temperature and the set temperature to keep the outlet temperature of the heat exchanger 18 constant, and the air volume of the air supply fan 36 is adjusted according to the gas amount. adjust.

The high-temperature combustion exhaust from the burner 22 flows through the fins 18b of the main heat exchanger 18 provided upstream of the combustion exhaust passage by the air supply fan 36 to exchange heat.
In the main heat exchanger 18, only the sensible heat contained in the combustion exhaust is recovered so as not to generate drainage.
The combustion exhaust gas that has passed through the main heat exchanger 18 is guided toward the sub heat exchanger 19 and guided toward the drain evaporator 100 by the exhaust branching section 200 as shown in FIG. Fork.
The combustion exhaust gas guided to the auxiliary heat exchanger 19 is subjected to heat exchange again in the auxiliary heat exchanger 19 and then discharged from the exhaust port 44a to the outside of the appliance.
On the other hand, the combustion exhaust gas guided to the drain evaporator 100 is exhausted from the exhaust port 44b to the outside of the instrument after the collected drain is evaporated in the drain evaporator 100.

In the auxiliary heat exchanger 19, the combustion exhaust gas that has passed through the main heat exchanger 18 is further cooled to generate drainage to recover latent heat, and the sensible heat in the combustion exhaust gas that could not be recovered by the main heat exchanger. Collect.
Here, in the main heat exchanger 18, only sensible heat contained in the combustion exhaust is recovered so as not to generate drain, but drain is also generated in a local low-temperature portion existing in the main heat exchanger 18. In order to suppress this, the temperature of the combustion exhaust must be kept high to some extent, and sufficient sensible heat cannot be recovered.
On the other hand, in the auxiliary heat exchanger 19, it is not necessary to prevent the generation of drain, so that drain is generated and latent heat is recovered, and sensible heat in the combustion exhaust that cannot be recovered by the main heat exchanger 18 is recovered. Full recovery is possible.
At this time, the combustion exhaust gas that passes through the auxiliary heat exchanger 19 does not pass through the drain evaporator 100 and has a high temperature. Therefore, the temperature difference between the auxiliary heat transfer tube 19a and the combustion exhaust gas is large, and the combustion exhaust to the auxiliary heat transfer tube. The heat transfer speed to 19a becomes faster, and sensible heat can be efficiently recovered.

In addition, when the drain generated in the auxiliary heat exchanger 19 is transferred to the drain recovery unit 202 through the fins 19b, the drain is transferred to the drain evaporation unit 101 through the burring hole 202a.
Since the drain evaporation part 101 is a hydrophilic porous ceramic, the dropped drain diffuses throughout the drain evaporation part 101.

In the drain evaporation unit 101, the drain comes into contact with the combustion exhaust after passing through the main heat exchanger 18, and is heated and evaporated.
At this time, since the drain is diffused throughout the ceramic drain evaporation portion 101, the contact area between the drain and the combustion exhaust gas is large, and the combustion exhaust gas that is in contact with the drain passes through the auxiliary heat exchanger 19. The temperature is high. Therefore, the drain evaporates efficiently.
Further, since the combustion exhaust gas passing through the drain evaporator 100 does not pass through the auxiliary heat exchanger 19, unlike the conventional case where the combustion exhaust gas after passing through the auxiliary heat exchanger 19 is guided to the drain evaporator 100. Therefore, the recovery rate of the combustion exhaust heat in the auxiliary heat exchanger 19 need not be restricted.

  It should be noted that the evaporation of the drain is not performed only on the drain evaporation unit 101, but is also performed while the drain falls from the drain recovery unit 202 to the drain evaporation unit 101. That is, by increasing the interval between the drain collecting unit 202 and the drain evaporating unit 101 and increasing the drain dropping time, the drain evaporates in a shorter time.

As mentioned above, although the Example of this invention was described, this invention is not limited to such embodiment at all, Of course, it can implement with a various form in the range which does not deviate from the summary of this invention.
For example, the installation position of the drain receiver is not limited to the embodiment, and the positional relationship of the burner, the main heat exchanger, and the auxiliary heat exchanger is not limited to the embodiment. For example, a burner with a flame port facing downward, a main heat exchanger, a sub heat exchanger, and a drain evaporator are provided in this order from the top, and one of the combustion exhaust gas that has passed through the main heat exchanger to the drain evaporator. If the portion is configured to be guided using a current plate, the drain never falls into the main heat exchanger, and the main heat exchanger is not clogged by the drain.
Furthermore, the main heat exchanger and the sub heat exchanger are not limited to fin tube types as long as they perform gas-liquid heat exchange, and the sub heat transfer tubes are not limited to stainless steel as long as they have corrosion resistance. .
Further, the drain evaporator is not limited to a structure in which a stainless plate and a ceramic plate are laminated, and a corrosion-resistant ceramic coating or titanium coating may be applied to the surface of the stainless plate. In addition, the drain evaporator may be configured such that a plurality of stainless steel filters are stacked under the exhaust branch portion so that the combustion exhaust heat passes between the filters. In this case, the drain falls one by one on the stainless steel filter layer one by one, but in addition to the high thermal conductivity of stainless steel, the area of contact with the combustion exhaust of the drain increases, so the drain evaporates in a shorter time. To do.

  The present invention may be applied not only to a forced air supply / exhaust water heater provided with a fan, but also to a natural combustion type water heater. Further, the present invention is not limited to a single hot water supply device, and may be applied to a hot water heater with a bath chasing function or a hot water heater with a heating function.

It is explanatory drawing which showed the water heater of this invention Example. It is explanatory drawing which showed the drain evaporator in the water heater of this invention Example. It is explanatory drawing which showed the drain collection device in the water heater of this invention Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Instrument casing 18 Main heat exchanger 19 Sub heat exchanger 20 Combustion chamber 21 High temperature exhaust chamber 22 Burner 23 1st exhaust chamber 24 2nd exhaust chamber 36 Supply fan 18a Main heat exchanger tube 18b Fin 19a Sub heat exchanger tube 44a Exhaust port 44b Exhaust port 100 Drain evaporator 101 Drain evaporation part 202 Drain recovery part 200 Exhaust branch part

Claims (1)

A burner that burns fuel in the combustion chamber;
A main heat exchanger that recovers sensible heat from the combustion exhaust of the burner to heat the water flow in the heat transfer tube;
A sub heat exchanger that recovers latent heat in addition to sensible heat that could not be recovered by the main heat exchanger from the combustion exhaust that has passed through the main heat exchanger, and heats the water in the heat transfer tubes, and the sub heat A drain evaporator that heats and evaporates the drain generated by the recovery of latent heat in the exchanger;
In the water heater with
The hot water supply, wherein the auxiliary heat exchanger and the drain evaporator are arranged in parallel in the exhaust passage of the combustion exhaust that has passed through the main heat exchanger so as not to have an upstream / downstream relationship in the exhaust passage. vessel.

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