JPS6138779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a combustion apparatus for gas, oil, etc.
In particular, we have achieved high efficiency by improving the heat exchange method,
The purpose is to save energy.

FIG. 1 shows a conventional heat exchange type combustion device.
The following is a step-by-step explanation. The burner 1 burns the fuel supplied by the fuel supply section 2, creating a flame F. The high temperature combustion gas downstream of the flame F passes through the heat exchanger drum 3 and reaches the primary heat exchanger 4 .
The temperature of the combustion gas heat-exchanged in the primary heat exchanger 4 is lowered to about 200° C. in the primary exhaust chamber 5. In the past, combustors only had a primary heat exchanger 4, but in recent years, as energy conservation has become a priority, it has become necessary to further lower the temperature of the combustion gas. Therefore, the secondary heat exchanger 6 shown in FIG. 1 will be provided. Condensed water generated from the low-temperature combustion gas is discharged to the outside by the drain receiver 12. Although ventilation resistance increases due to the primary heat exchanger 4 and the secondary heat exchanger 6, the combustion gas is forcibly guided to the exhaust top 8 and exhausted to the outside by the fan 9 connected to the fan motor 10. . Now, the temperature in the primary exhaust chamber 5 is 200℃.
The low-temperature combustion gas that has been mixed is transferred to the secondary heat exchanger 6.
In order to exchange heat with the heat exchanger, a huge heat transfer area comparable to that of the primary heat exchanger 4 is required. Therefore, 2
The cost of materials for the secondary heat exchanger 6 increases and the price rises, which often impairs the product's marketability.

In order to solve the problems of the conventional example as described above, the present invention provides a heat exchanger with a small heat transfer area,
The target high efficiency can be achieved by recirculating combustion gas through the heat exchanger. Hereinafter, the configuration of an embodiment of the water heater will be explained with reference to FIG.

The fuel supplied by the fuel supply section 2 in the burner 1 is combusted to create a flame F. The high temperature combustion gas downstream of the flame F passes through the heat exchanger drum 3 and
The next heat exchanger 4 is reached. The burnt gas heat-exchanged in the primary heat exchanger 4 passes through the primary exhaust chamber 5 and reaches the secondary heat exchanger 6. After that, part of the combustion gas is exhausted to the outside from the exhaust top 8, and the rest is exhausted from the fan motor 1.
The air is guided to the circulation chamber 11 by the fan 9 connected to the air. Condensed water in the circulation chamber 11 is collected in a drain receiver 12 and discharged through a drain pipe 13. Further, 14 is a water supply pipe. The combustion gas in the circulation chamber 11 reaches the secondary heat exchanger 6 again while mixing with the combustion gas in the primary exhaust chamber 5.

With the above configuration, the more the recirculation amount is increased, the more the secondary heat exchanger 6 can perform sufficient heat exchange even if the heat transfer area is small. Generally, the amount of heat transfer Q is calculated by assuming that the heat transfer area is A, the overall heat transfer coefficient is U, and the logarithmic average temperature difference is △tm, then Q = UA△
Represented by tm. Since the heat transfer coefficient on the water side is very large, for convenience, the overall heat transfer coefficient U is represented by the heat transfer coefficient αg on the gas side. Then, U≈αg, and if the combustion gas flow velocity is v, it can be expressed as U≈αgv ^1/3 . Therefore, if the circulation rate is doubled as that of the main stream, the flow rate will be tripled, the overall heat transfer coefficient U will be 1.44 times, and the heat transfer area will only need to be 70%. Third
The figure shows the efficiency when the heat transfer area is kept constant and the circulation rate is changed to twice that of the mainstream. The efficiency has increased to 95%, compared to 84% without circulation.

As is clear from the above description, the combustion apparatus of the present invention is provided with a fan so as to guide the combustion gas that has passed through the secondary heat exchanger once again to the heat exchanger. Even if the heat transfer area is small, heat exchange can be performed sufficiently by recirculation, and high heat exchange efficiency can be obtained. Furthermore, by circulating the combustion gas through the secondary heat exchanger, the temperature of the combustion gas decreases and the amount of condensed water increases, making it possible to capture a large amount of heat of condensation.

[Brief explanation of the drawing]

FIG. 1 is a front view of a conventional combustion device, FIG. 2 is a front view of an embodiment of the combustion device of the present invention, and FIG. 3 is a diagram of the relationship between circulation ratio and efficiency of the combustion device of the present invention. 1... Burner, 4...Primary heat exchanger, 6...Secondary heat exchanger, 9...Fan, 12...Drain receiver.

Claims (1)

[Claims] 1 Consists of a burner that burns fuel, a primary heat exchanger that provides heat to others, a secondary heat exchanger that provides heat to others while generating condensed water, and a fan that pulls combustion gas. A combustion apparatus is provided with a fan located downstream of a primary heat exchanger so as to guide combustion gas that has once passed through the secondary heat exchanger to the secondary heat exchanger.