JPH11148720A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger to prevent the occurrence of corrosion due to condensate and provide the high efficiency of heat exchange. SOLUTION: A heat-exchanger comprises a heat exchanger 40 for collection of a sensitive heat to absorb mainly the sensitive heat of exhaust gas; and a heat exchanger 50 for collection of a latent heat to absorb mainly the latent heat of exhaust gas. The efficiency of heat-exchange on the heat-exchanger 40 for collection of a sensitive heat is suppressed for setting to a low value in a range at which condensate generated by absorbing the latent heat of exhaust gas is not vapor-condensed, and the heat exchanger 50 for collection of a latent heat is covered with a film 53 to protect the heat-exchanger from corrosion due to the condensate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat source which is disposed in an exhaust passage through which exhaust gas generated when fuel is burned flows, and which heats a fluid to be heated flowing through a heat receiving tube by absorbing the heat of the exhaust gas. About the exchanger.

[0002]

2. Description of the Related Art Conventionally, a heat exchanger used in a water heater or the like is a heat exchanger in which heat generated when a fuel such as methane, propane or butane is burned is disposed near a burner or the like. It was collected and heated such as water supply.

By the way, if the heat exchange efficiency of the heat exchanger is increased beyond a certain level, the recovery of latent heat from the exhaust gas proceeds, and condensed water condenses on the surface of the heat exchanger. This condensed water is nitrogen oxide (NOx) generated by oxidizing combustion air at high temperature.
Sulfur oxide (SOx) and the like generated by oxidizing the odorant added to the combustion gas to detect gas leakage and gas are dissolved, and acid water drops of pH 2-3 dissolved in nitric acid and sulfuric acid are dissolved. Has become.

[0004] If the heat condensed water condensed in this way corrodes the heat receiving tubes and fins of the heat exchanger, problems such as leakage of the internal fluid may occur. On the other hand, in the vicinity of the burner or the like, the exhaust gas temperature exceeds the heat-resistant temperature of a coating film, for example, an epoxy-based paint, for protecting the heat receiving tube and the like from corrosion by condensed water. For this reason, in the conventionally used heat exchanger, a large amount of condensed water does not condense,
The heat exchange efficiency was kept relatively low so as to be about 80% at the time of maximum combustion.

[0005]

As described above, in the conventional heat exchanger, the heat exchange efficiency is suppressed to a certain extent so that a large amount of condensed water does not form dew. Could not.

The present invention has been made in view of such problems of the prior art, and provides a heat exchanger that can obtain high heat exchange efficiency while preventing corrosion due to condensed water. It is intended to be.

[0007]

The gist of the present invention to achieve the above object lies in the following inventions. [1] A heat exchanger arranged in an exhaust path through which exhaust gas generated when burning fuel flows to absorb a heat of the exhaust gas and heat a fluid to be heated flowing through a heat receiving tube. Sensible heat recovery heat exchanger that mainly absorbs heat (4
0), and a latent heat recovery heat exchanger (50) disposed downstream of the exhaust path and mainly absorbing the latent heat of the exhaust gas, and heat in the sensible heat recovery heat exchanger (40) is provided. A heat exchanger wherein the exchange efficiency is set within a range in which condensed water generated by absorbing the latent heat of the exhaust gas does not dew.

[2] A heat exchanger which is disposed in an exhaust path through which exhaust gas generated when burning fuel flows and absorbs heat of the exhaust gas and heats a fluid to be heated flowing through a heat receiving tube. A sensible heat recovery heat exchanger (40) that mainly absorbs the sensible heat of the exhaust, and a latent heat recovery heat exchanger (50) that is disposed downstream of the exhaust path and mainly absorbs the latent heat of the exhaust gas. And the heat exchange efficiency in the sensible heat recovery heat exchanger (40) is set to a range in which condensed water generated by absorbing the latent heat of the exhaust gas does not condense, and the latent heat recovery heat exchanger (50) is provided. A heat exchanger which is coated with a film (53) for protecting the film from corrosion by the condensed water.

[3] The heat exchange efficiency of the heat exchanger for sensible heat recovery (40) is determined by changing the heat exchange efficiency of the heat exchanger for sensible heat recovery (40) when the fuel is burned at a predetermined minimum combustion amount. The heat exchanger according to [1] or [2], wherein the heat exchanger is set within a range where no condensation occurs.

[4] A tray (13) between the latent heat recovery heat exchanger (50) and the sensible heat exchanger for receiving condensed water generated by the latent heat recovery heat exchanger (50).
And the condensed water is used as the sensible heat recovery heat exchanger (40).
[1] characterized in that it is prevented from falling
The heat exchanger according to [2] or [3].

[5] The fluid to be heated is heated by the latent heat recovery heat exchanger (50) and then by the sensible heat recovery heat exchanger (40). The heat exchanger according to [1], [2], [3] or [4].

The present invention operates as follows. The heat exchange efficiency of the sensible heat recovery heat exchanger (40) is set to a range in which the condensed water generated by absorbing the latent heat of the exhaust is not dew-condensed. The sensible heat recovery heat exchanger (40), which is difficult to protect by (53) or the like, can be protected from corrosion by condensed water. The sensible heat recovery heat exchanger (40) and the latent heat recovery heat exchanger (5
0), the heat of the exhaust gas is recovered by both of them, so that even if the heat exchange efficiency of the sensible heat recovery heat exchanger (40) is kept low, a high heat exchange efficiency can be obtained by combining both.

For example, the heat exchange efficiency of the sensible heat recovery heat exchanger (40) is set to about 75% at the time of maximum combustion, and the heat exchange efficiency of the latent heat recovery heat exchanger (50) is reduced to 15%.
If set to percent, sensible heat recovery heat exchanger (40)
A high heat exchange efficiency of about 90% in total can be obtained without dew condensation occurring on the side. The heat exchange efficiency of the latent heat recovery heat exchanger (50) is determined from the difference between the heat exchange efficiency required for the entire heat exchanger and the heat exchange rate of the sensible heat recovery heat exchanger (40). I have. Each heat exchange efficiency is set by increasing or decreasing the heat transfer area such as the number and size of the fins.

Further, the latent heat recovery heat exchanger (50) is covered with a film (53) for protecting it from corrosion by condensed water. Since the latent heat recovery heat exchanger (50) is disposed downstream of the exhaust from the sensible heat recovery heat exchanger (40), the exhaust temperature is relatively low, the latent heat is mainly recovered, and a large amount of condensation is performed. Water condenses. For this reason, by covering with the film (53), the latent heat recovery heat exchanger (50) can be effectively protected from corrosion by condensed water.

The heat exchange efficiency is higher when the fuel is burned with the minimum combustion amount than when the fuel is burned with the maximum combustion amount, and condensed water is easily condensed. Therefore, by setting the heat exchange efficiency of the sensible heat recovery heat exchanger (40) on the basis of the minimum combustion, the condensed water is always supplied to the sensible heat recovery heat exchanger (40) regardless of the combustion amount. ) Can be prevented.

Further, between the latent heat recovery heat exchanger (50) and the sensible heat recovery heat exchanger (40), a tray (1) for receiving condensed water generated by the latent heat recovery heat exchanger (50).
By providing 3), it is possible to prevent the condensed water condensed on the latent heat recovery heat exchanger (50) from dropping and corroding the sensible heat recovery heat exchanger (40).

Further, since the fluid to be heated is heated by the heat exchanger for latent heat recovery (50) and then by the heat exchanger for sensible heat recovery (40), it is arranged on the downstream side where the exhaust gas temperature is low. Also in the latent heat recovery heat exchanger (50), the temperature difference with the fluid to be heated increases, and the heat exchange efficiency can be increased.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Each drawing shows an embodiment of the present invention. In the present embodiment, a heat exchanger according to the present invention is applied to a water heater 10. As shown in FIG. 2, the water heater 10 includes a combustion chamber 11, and a burner 12 is disposed below the combustion chamber 11. Above the burner 12, a sensible heat recovery heat exchanger 40 for mainly recovering the sensible heat of the exhaust gas is disposed, and further above the burner 12, a latent heat recovery heat exchanger 50 for mainly recovering the latent heat of the exhaust gas is disposed.

Between the sensible heat recovery heat exchanger 40 and the latent heat recovery heat exchanger 50, the condensed water generated by the latent heat recovery heat exchanger 50 is received, and the condensed water is transferred to the sensible heat recovery heat exchanger. 4
A receiving tray 13 is attached to prevent the tray 13 from dropping on zero. The receiving tray 13 partitions the combustion chamber 11 up and down except for a part of the right end. Exhaust after passing through the sensible heat recovery heat exchanger 40 is discharged to the opening 14 at the right end of the combustion chamber 11 without the receiving tray 13. Through latent heat recovery heat exchanger 5
The exhaust gas flows into the exhaust passage portion 15 where 0 is disposed.

The receiving tray 13 is connected to the combustion chamber 1 from the opening 14 side.
1, a drain receiver 16 for temporarily storing condensed water collected by the tray 13 is provided at a lower end portion of the slope. Drain receiver 1
A discharge passage 17 for condensed water is connected to the bottom of 6, and a neutralization treatment device 18 for neutralizing acidic condensed water is attached in the middle of the discharge passage 17.

The inlet of the latent heat recovery heat exchanger 50 is connected to a feed water pipe 21 into which feed water flows, and the outlet of the latent heat recovery heat exchanger 50 is connected to the sensible heat recovery heat exchanger 40 by a connecting water pipe 22. Is connected to the input side. Heat exchanger for sensible heat recovery 4
A hot water supply pipe 23 from which the supply water after heating flows out is connected to the outlet side of 0.

In the vicinity of the inlet of the feed water pipe 21, a water input thermistor 24 for detecting the temperature of the supplied water is provided.
On the downstream side, a water flow sensor 25 for detecting the presence or absence of water flow and the amount of water flow is attached. A hot water supply thermistor 26 for detecting the temperature of hot water to be discharged is provided near the outlet of the hot water supply pipe 23, and a water flow control valve 2 for limiting the flow rate of hot water to be discharged is provided downstream thereof.
7 are provided.

At the lower left of the combustion chamber 11, a combustion fan 28 for feeding air supply toward the burner 12 is arranged. Further, in the middle of a gas supply pipe 31 for feeding the combustion gas to the burner 12, a gas solenoid valve 32 for controlling the supply of the combustion gas on and off, an original gas solenoid valve 33, and a burner 12
Proportional valve 34 that regulates the amount of combustion gas supplied to the
Is attached.

The water heater 10 has an electric board 35 containing circuit components for controlling the operation thereof.
Is connected, for example, to a remote controller 36 which is arranged in a kitchen or the like, receives a setting operation of hot water temperature, and displays various states.

FIG. 1 shows the sensible heat recovery heat exchanger 40 and the latent heat recovery heat exchanger 50 in more detail.
The sensible heat recovery heat exchanger 40 includes a sensible heat heat receiving tube 41 through which feed water to be heated passes, and fins 42 for increasing the efficiency of recovering the heat of the exhaust gas. The sensible heat receiving tube 41 and the fins 42 of the sensible heat recovery heat exchanger 40 are both formed of copper having a good thermal conductivity.

The latent heat recovery heat exchanger 50 is composed of a latent heat receiving tube 51 through which feed water to be heated passes, and fins 52. The latent heat receiving tube 51 and the fins 52 are both formed of copper. Further, the surface of the latent heat recovery heat exchanger 50 that comes into contact with the exhaust gas (the latent heat receiving tube 51 and the fins 5).
2) is a coating 5 having acid resistance and electrical insulation.
3 coated. As the coating 53,
Epoxy, Teflon, polysulfide, fluororesin,
Silicon resin, phenol resin, or the like can be used. Here, the coating 53 is made of an epoxy-based organic paint.
Is formed.

The sensible heat recovery heat exchanger 40 has a heat exchange efficiency of about 72% during the maximum combustion of the burner 12 and about 80% during the minimum combustion.
The heat transfer area is set according to the number and size of the fins 42. On the other hand, the heat transfer area of the latent heat recovery heat exchanger 50 is set by the number of the fins 52 and the like so that the heat exchange efficiency is about 15% during the maximum combustion of the burner 12 and about 20% during the minimum combustion. ing.

FIG. 3 shows the distribution of the heat exchange efficiency of the sensible heat recovery heat exchanger 40 and the latent heat recovery heat exchanger 50. Conventionally used heat exchangers include only those corresponding to the sensible heat recovery heat exchanger 40, and the heat exchange efficiency 61 at the time of maximum combustion is set to about 80%. In this case, the heat exchange efficiency 62 during the minimum combustion
Rises to around 87 percent.

Therefore, when the heat exchanger having such heat exchange efficiency is used as it is as a heat exchanger for recovering sensible heat, and a heat exchanger for recovering latent heat is added downstream thereof, the total heat exchange Efficiency is shown in bar graph 64 at maximum combustion and bar graph 65 at minimum combustion.
It becomes a high value as shown by.

At the time of maximum combustion, a heat exchanger for recovering sensible heat,
Dew condensation hardly occurs in both of the heat exchangers for latent heat recovery, but at the time of the minimum combustion, the heat exchange efficiency 65a of the heat exchanger for sensible heat recovery is the heat exchange efficiency of the boundary entering the dew condensation area 63. Since it exceeds 85%, dew condensation occurs even in the heat exchanger for recovering sensible heat during the minimum combustion.

Therefore, in the sensible heat recovery heat exchanger 40 of the present embodiment, the heat exchange efficiency 66a on the sensible heat recovery heat exchanger 40 side at the time of minimum combustion is about 80 And the total heat exchange efficiency of the sensible heat recovery heat exchanger 40 and the latent heat recovery heat exchanger 50 is approximately equal to that shown in the bar graph 65. The heat exchange efficiency 66b of the heat exchanger 50 is set.

As described above, the heat exchange efficiency of the latent heat recovery heat exchanger 50 is determined from the heat exchange efficiency of the sensible heat recovery heat exchanger 40 during the minimum combustion and the required total heat exchange efficiency. Then, the heat transfer areas of the sensible heat recovery heat exchanger 40 and the latent heat recovery heat exchanger 50, that is, the fins 42 and 52
Number, size, etc. are determined.

When the heat transfer areas of the sensible heat recovery heat exchanger 40 and the latent heat recovery heat exchanger 50 are set as described above, the heat exchange efficiency 67a of the sensible heat recovery heat exchanger 40 side during the maximum combustion. Decreases to about 72 percent. However, since the exhaust gas temperature on the sensible heat recovery heat exchanger 40 side is less reduced, the heat exchange efficiency 67b on the latent heat recovery heat exchanger 50 side is increased to about 20%.

Since the sensible heat recovery heat exchanger 40 mainly recovers the sensible heat of the exhaust gas and hardly generates condensed water, its surface is covered with a film made of an epoxy-based organic paint or the like. Absent. The sensible heat recovery heat exchanger 4
In addition to copper, stainless steel (SUS), aluminum, or an alloy thereof may be used as a base material of the heat exchanger 50 for latent heat recovery.

Next, the operation will be described. The heat from the burner 12 is first absorbed by the sensible heat recovery heat exchanger 40 arranged near the burner 12. At this time, the heat exchange efficiency of the sensible heat recovery heat exchanger 40 is about 8 at the time of minimum combustion.
Since it is suppressed to about 0%, which is smaller than the heat exchange efficiency of condensation water (about 85%), dew condensation hardly occurs in the sensible heat recovery heat exchanger 40. That is, in the sensible heat recovery heat exchanger 40, the sensible heat of the heated exhaust gas is mainly absorbed.

The exhaust gas whose sensible heat has been recovered by the sensible heat recovery heat exchanger 40 reaches the latent heat recovery heat exchanger 50 through the opening 14. Since the temperature of the exhaust gas that has reached the latent heat recovery heat exchanger 50 has fallen to about 200 ° C. to 280 ° C., the latent heat recovery heat exchanger 50 mainly recovers the latent heat of the exhaust gas and generates a large amount of condensed water. Is a latent heat recovery heat exchanger 5
Dew condensation on 0. However, the latent heat recovery heat exchanger 50
Is not corroded by the condensed water condensed because it is covered with the film 53.

The latent heat recovery heat exchanger 50 has a speed of 50 m / min.
A large amount of condensed water of about 1 is condensed. These condensed water drops from the latent heat recovery heat exchanger 50 and
And discharged through the drain receiver 16, the discharge passage 17, and the neutralization device 18.

As described above, the condensed water condensed on the latent heat recovery heat exchanger 50 is received by the plate 13 so as not to fall on the sensible heat recovery heat exchanger 40.
The sensible heat recovery heat exchanger 40 is hardly corroded by condensed water even if it is not coated with a film, in combination with the fact that the heat exchanger 40 for sensible heat recovery does not form itself.

Since the feed water is first heated through the latent heat recovery heat exchanger 50 as shown in FIG. 2, even if the exhaust gas reaching the latent heat recovery heat exchanger 50 has a relatively low temperature, The temperature difference from the water supply is large, and the heat of the exhaust can be efficiently absorbed.

In the embodiment described above, the corrosion of the latent heat recovery heat exchanger 50 is prevented by coating with a coating film. However, in consideration of the occurrence of pinholes and the like, electrolytic protection and the like are further added thereto. You may make it.

In this embodiment, a gas water heater using combustion gas as a fuel has been described as an example. However, the fuel may be oil or kerosene, and the appliance may be one for heating a bath or heating. It may be.

[0042]

According to the heat exchanger of the present invention, since the heat exchange efficiency of the heat exchanger for sensible heat recovery is set within a range in which condensed water does not condense, it is exposed to high-temperature exhaust gas. The heat exchanger for sensible heat recovery, which is difficult to protect by a coating or the like, can be protected from corrosion by condensed water. Also, since the heat of the exhaust gas is recovered by both the heat exchanger for sensible heat recovery and the heat exchanger for latent heat recovery disposed downstream of the exhaust path, a higher heat exchange efficiency can be obtained by adding both. Obtainable.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a heat exchanger according to one embodiment of the present invention.

FIG. 2 is an explanatory view showing a water heater to which the heat exchanger according to one embodiment of the present invention is applied.

FIG. 3 is an explanatory diagram showing heat exchange efficiency of a sensible heat recovery heat exchanger and a latent heat recovery heat exchanger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Water heater 11 ... Combustion chamber 12 ... Burner 13 ... Receiving tray 14 ... Opening 15 ... Exhaust passage part 16 ... Drain receiver 28 ... Combustion fan 40 ... Sensible heat recovery heat exchanger 41 ... Sensible heat heat receiving tube 42 ... Fin 50 ... Heat exchanger for latent heat recovery 51 ... Latent heat receiving tube 52 ... Fin 53 ... Coating

Claims (5)

[Claims] 1. A heat exchanger disposed in an exhaust path through which exhaust gas generated when fuel is burned flows to heat a fluid to be heated flowing through a heat receiving tube by absorbing the heat of the exhaust gas. A sensible heat recovery heat exchanger that mainly absorbs the sensible heat of the exhaust gas, and a latent heat recovery heat exchanger that is disposed downstream of the exhaust path and that mainly absorbs the latent heat of the exhaust gas. A heat exchanger wherein the heat exchange efficiency of the heat exchanger is set within a range in which condensed water generated by absorbing the latent heat of the exhaust gas does not dew. 2. A heat exchanger disposed in an exhaust passage through which exhaust gas generated when fuel is burned flows, and heats a fluid to be heated flowing through a heat receiving tube by absorbing heat of the exhaust gas. A sensible heat recovery heat exchanger that mainly absorbs the sensible heat of the exhaust gas, and a latent heat recovery heat exchanger that is disposed downstream of the exhaust path and that mainly absorbs the latent heat of the exhaust gas. The heat exchange efficiency of the heat exchanger for heat is set to a range in which the condensed water generated by absorbing the latent heat of the exhaust gas does not condense, with a coating for protecting the latent heat recovery heat exchanger from corrosion by the condensed water. A heat exchanger characterized by being coated. 3. The heat exchange efficiency of the sensible heat recovery heat exchanger,
3. The heat exchanger according to claim 1, wherein when the fuel is burned at a predetermined minimum combustion amount, the heat exchanger for recovering sensible heat is set within a range in which condensed water does not condense. 4. A tray for receiving condensed water generated by the latent heat recovery heat exchanger is provided between the latent heat recovery heat exchanger and the sensible heat heat exchanger. 4. The heat exchanger according to claim 1, wherein the heat exchanger is prevented from dropping onto the heat exchanger. 5. The method according to claim 1, wherein the fluid to be heated is heated by the latent heat recovery heat exchanger and then heated by the sensible heat recovery heat exchanger. 4. The heat exchanger according to 4.