JPS5842833Y2 - Forced air heater - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a forced-air heater having a heat exchanger constituted by a plurality of pipes through which combustion gas generated in a burner section passes.

It is generally known that fuel gas contains sulfur (element symbol S), which is caused by moisture (H
2O) and S cause a chemical reaction (the following formula) % Formula % () The dew point of these (sulfite) sulfuric acids changes depending on the volume ratio in the gas, but in general city gas it is 80 to 120°C.

In addition, the temperature range where (sulfite) sulfuric acid causes severe metal oxidation corrosion is 80°C.
~100°C, and if the metal plate of the heat exchanger material is exposed to this temperature range, it will corrode, create holes or cracks, and cause exhaust gas to leak, ending its life.

Particularly when such a heat exchanger is incorporated into a closed hot air heater, exhaust gas may leak into the room or drain may leak from the holes.

The present invention was developed in view of the above circumstances, and it is an object of the present invention to provide an improved forced air heater that prevents the temperature of the heat exchanger from falling below the dew point temperature.

Therefore, in order to prevent the temperature of the multiple pipes that make up the heat exchanger from falling below the dew point depending on the amount of heat exchanged by each pipe, the present invention uses pipes with different amounts of heat exchange depending on the position of each pipe. The structure of the present invention is to use the pipe in the position where the amount of heat exchange between the heat exchanger and the air to be heat exchanged is large among the plurality of pipes that make up the heat exchanger. The pipe is designed to have a lower heat exchange rate than the pipe at the position where the volume decreases.

With this configuration, there is no risk that the pipe at a position where the amount of heat exchange is large will become overcooled and become below the dew point, and a forced air heater with a long life can be obtained.

Next, one embodiment of this invention will be explained with reference to the drawings.

In Figures 1 to 5, 1 is a combustion tube, 2 is a header connected to this combustion tube on the downstream side, and 3 is a header connected to this header on the downstream side, parallel to each other and parallel to combustion tube 1. Instead of multiple metal heat exchanger pipes, 3A of these pipes.

3b is a pipe located at a position where the amount of heat exchange with the heat exchange air is greatest.

4 is an auxiliary header connected to the heat exchanger pipe on the downstream side, 5 is an exhaust pipe connected to the auxiliary header on the downstream side, and 6 is an air supply/exhaust attachment connected to the exhaust pipe on the downstream side. , 7 are baffle plates provided in the combustion tube 1, which allow sufficient heat exchange 4 of the high temperature gas with the wall portion of the combustion tube 1.

A burner 8 is provided in the combustion tube 1 and is composed of a plurality of pipe-shaped burner elements 8a.

9 is a blower for indoor ventilation, and its output air flows as shown by arrow B, exchanges heat with the combustion tube 1 and heat exchanger 3, becomes high-temperature air, and is sent from the indoor ventilation grill (not shown) to the machine. Sent outside (indoors).

10 is a motor for driving the blower 9, and 11 is a gas chamber communicating with the burner 8, which is filled with combustion gas.

12 is a primary air hole bored in a part of this gas chamber; 13
Reference numeral 1 denotes an air supply hose communicating with the air supply path of the supply/exhaust attachment 6, and 14 represents combustion air passing through the air supply hose, which is generally obtained from outside.

15 is the exhaust joint, 16 is the long inner fin, 1
7 is a short inner fin, and the above long inner fin 1
6, it is formed by twisting a flat metal plate.

Reference numeral 18 indicates a forced air blower 19, an air passage extending from the air supply hose 13 to the exhaust pipe 5, 20 a main body casing, and 21
is an air guide, and 22 is a blower casing.

Next, the operation of the one shown in FIG. 2 will be explained.

When a starting switch (not shown) is turned on, the blower 19 is activated and combustion air flows as shown by arrow A.
Combustion gas is supplied from the gas chamber 11 to the burner 8 section, and combustion is performed within the combustion tube 1.

After the start of combustion, when the internal temperature rises to a certain extent, the indoor ventilation motor 10 is activated, and the warm air that has exchanged heat with the combustion tube 1 and the heat exchanger 3 is transferred to the indoor ventilation grill (not shown) by the blower 9. ) is sent into the room, and the cool air in the room is sucked into the inside of the machine by the blower 9, and then sent out as described above.

At this point, the combustion gas that has been cooled to a certain extent by the combustion tube 1 is collected in the header 2, but the temperature in this part is still high and there is no fear of dew point corrosion.

However, for heat exchange in the medium to low temperature range, that is, heat exchange downstream of header 2, the contact area with the heat exchange air is increased, so it is better to use a shell-and-tube heat exchanger because the amount of heat exchange is It would be better if the number of heat exchange pipes increased, but on the other hand, each heat exchange pipe 3
The flow velocity of the combustion gas inside is relatively slow and tends to be laminar.

Laminar heat exchange is inefficient and requires very long distances.

For this purpose, inner fins 16 and 17 made of twisted flat plates as shown in FIGS. 3 and 4 are inserted into the heat exchange pipe 3 to constantly disturb the flow inside the pipe and perform turbulent heat exchange. Increases heat exchange efficiency.

However, as shown in FIG. 5, among the heat exchange pipes 3, the pipes 3a and 3b at both ends are exposed to cold air more often than other pipes.

For this reason, if the same inner fin is inserted into all the heat exchange pipes 3, the pipes 3a and 3b will be supercooled and the temperature will be below the dew point temperature.

Therefore, short inner fins 17 are inserted into these pipes 3 a and 3 b to perform turbulent heat exchange up to the middle and laminar heat exchange thereafter, performing two-stage control of the heat exchange amount.
This is to prevent the temperature near the auxiliary header 4 from dropping below the dew point.

This provides a long-life heat exchanger.

As mentioned above, this idea is based on the fact that among the multiple pipes that make up the heat exchanger, the combustion gas generated in the burner passes through, and the pipe is located at a position where the amount of heat exchange between the heat exchanger and the air that is exchanging heat is large. , the heat exchange area is made smaller by changing the length of the inserted inner fin, for example, so that the heat exchange rate is smaller than the pipe in the position where the heat exchange amount is reduced, so the heat exchange amount increases. There is no risk that the pipes at the location will become overcooled and drop below the dew point, and this has the effect of providing a forced air heater with a long life.

[Brief explanation of the drawing]

The figures all show one embodiment of this invention; Fig. 1 is a front view showing a schematic configuration, Fig. 2 is a front view showing a section of the heat exchanger part in Fig. 1, and Fig. 3 is a front view showing a schematic configuration. A front view showing an enlarged view of the heat exchanger pipe in Figure 2, Figure 4 is the same as Figure 3 ■■-
Vertical side view of the cross section taken along line I in the direction of the arrow, No. 5
The figure is a side view showing a schematic configuration. In the figure, 1 is a combustion tube, 3 is a heat exchange pipe, 3a, 3
b is a heat exchange pipe at a position where the amount of heat exchange increases, 8 is a burner, 9 is an indoor blower, 16.17 is an inner fin, and 18 is a combustion blower. Note that the same reference numerals in the figures indicate the same parts.

Claims (1)

[Claim for Utility Model Registration] A combustion blower that forces air to the burner section, a heat exchanger into which the combustion gas generated in the burner section is introduced, and a combustion blower that sends air to the heat exchanger to generate the combustion gas. and an indoor blower that sends the heat-exchanged air indoors, wherein the heat exchanger is composed of a plurality of pipes parallel to each other,
This heat exchanger is installed so that the air from the indoor blower passes in the radial direction of the pipe, and the heat exchanger between the air and the indoor blower exchanges heat with the heat exchanger in the pipe. A forced air heater characterized in that the heat exchange area inside the pipe is set small so that the pipe at a position where the amount of heat exchange is large has a smaller heat exchange rate than the pipe at a position where the amount of heat exchange is small. .