JPH06300360A - Hot air generator - Google Patents

Abstract

PURPOSE:To prevent rising of temperature at 4 part of a hollow pipe by a method wherein the hollow pipe is formed in a spiral whose curvature radius is changed continuously and the spiral pipe is interposed in a way that its center, line may coincide substantially with that passage. CONSTITUTION:A heat exchanging chamber 2 and a fan 21 are arranged in a body 1. In the heat exchanging chamber 2, a hollow pipe 3 formed in a spiral whose curvature radius is reduced continuously from the downward to the upward is provided in a way that a center line of the spiral pipe 3 coincides substantially with that of the heat exchanging chamber 2, and the both ends of the hollow pipe 2 protrude outside the heat exchanging chamber 2. The hollow pipe 3 is provided with a nozzle 31 of a gas burner at a lower end and mounted with an exhaust fan 32 at an upper end. By this, the heat transmission rate of the hollow pipe 3 does not increase or decrease depending on parts, whereby the hollow pipe 3 can be heated even. In addition, the hollow pipe 3 does not pile part on part with respect to an airstream, and therefore, can be heated or cooled uniformly. Thus the hollow pipe 3 can be prevented from being heated too high at a particular part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot air generator using a hollow pipe heated by a high temperature combustion gas flowing in the pipe as a heat source.

[0002]

2. Description of the Related Art It is known that a high temperature combustion gas is caused to flow in a hollow pipe to heat the hollow pipe to a high temperature, and heat treatment is performed by utilizing radiant heat from the surface of the hollow pipe.
For example, according to Japanese Utility Model Publication No. 60-42246, in a heating furnace for heating a steel plate or the like in a vacuum state, a hollow pipe in which three places in the middle are alternately bent into a U shape and formed into a substantially M shape as a whole is provided. Then, a burner is attached to one end of the hollow pipe, a high temperature combustion gas generated by combustion of the burner is flown into the pipe of the hollow pipe to heat the hollow pipe to a high temperature, and a radiant heat from the surface of the hollow pipe causes a steel plate or the like. It is known to heat the.

[0003]

It is conceivable to dispose a hollow pipe heated by such combustion gas in the air passage and heat the air to generate warm air.
When the air is heated by the hollow pipe, the heat is mainly transferred from the surface of the hollow pipe to the air, not by the radiant heat. Therefore, on the contrary, the surface of the hollow pipe is forcibly cooled by air, so in order to heat the air efficiently, the thickness of the hollow pipe should be made as thin as possible and the temperature of the hollow pipe surface should be kept high. Need to hold. However, if the hollow pipe is bent in the middle, the combustion gas collides with the inner wall of the hollow pipe at a predetermined angle when the flow direction of the combustion gas is bent along the hollow pipe. More heat is transferred to the hollow pipe, and therefore the bent portion of the hollow pipe is locally hotter than the straight portion. In the conventional one that mainly uses radiant heat from the hollow pipe for heating, the surface of the hollow pipe is not forcibly cooled, so that the radiant heat can be sufficiently generated even if the thickness of the hollow pipe is relatively thick, In this case, even if the bent portion of the hollow pipe becomes locally high in temperature, heat is conducted through the meat portion of the hollow pipe, the local temperature difference is alleviated, and the entire hollow pipe has a uniform temperature. As described above, when heating air by heat transfer from the hollow pipe, the thickness of the hollow pipe must be made thin, so if there is a locally high temperature part, the temperature difference with the surrounding is not relaxed, There is a problem that a high temperature portion such as a bent portion deteriorates earlier than other portions.

Therefore, in view of the above problems, it is an object of the present invention to provide a hot air generator which does not locally reach a high temperature even when air is heated using a thin hollow pipe. .

[0005]

In order to achieve the above-mentioned object, the present invention provides a warm pipe in which a hollow pipe for flowing a high-temperature combustion gas in the pipe is provided in the middle of a blower passage connected to a blower for warm air blower. In the generator, the hollow pipe is formed in a spiral shape whose radius of curvature continuously changes, and the center line of the spiral is provided so as to substantially coincide with the center line of the air passage.

[0006]

The heat transfer coefficient from the combustion gas to the inner wall of the hollow pipe is determined by the collision angle of the combustion gas to the inner wall and the flow velocity of the combustion gas, and the heat transfer coefficient increases as the collision angle increases and the flow velocity increases. When the hollow pipe is formed in a spiral shape, the exhaust gas flowing in the pipe always passes through the curved pipe path, so the heat transfer coefficient does not increase or decrease locally, and the entire hollow pipe is heated uniformly. It On the other hand, if the radius of curvature of the spiral hollow pipe is continuously changed and the center line of the spiral hollow pipe is arranged so as to substantially coincide with the center line of the air blow passage, the hollow pipe may overlap with the air flow. Instead, the air from the blower uniformly contacts the entire surface of the hollow pipe and is cooled uniformly. Therefore, the hollow pipe is uniformly heated by the combustion gas and is uniformly cooled by the air from the blower, so that the hollow pipe is not locally heated.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, reference numeral 1 is a main body of a warm air generator, and a heat exchange chamber 2 is provided inside the main body 1, and air is sent into the heat exchange chamber 2 through a lower connecting window 22. The blower 21 is arrange | positioned. Therefore, the heat exchange chamber 2 constitutes a part of the air passage of the blower 21. Further, in the heat exchange chamber 2, a spiral hollow pipe 3 whose radius of curvature decreases continuously from the bottom to the top so that the center line of the spiral is substantially aligned with the center line of the heat exchange chamber 2. It is provided in such a state that both ends thereof are attached so as to penetrate through the side wall of the heat exchange chamber 2 and project therefrom. A nozzle 31 of a gas burner is provided at the lower end opening of the hollow pipe 3 so as to eject gas toward the inside of the hollow pipe 3. An exhaust fan 32 is attached to the upper end opening of the hollow pipe 3, sucks gas and combustion air into the hollow pipe 3 from the lower end opening, and the hollow pipe 3 The high temperature combustion gas generated by the combustion of the gas in the pipe No. 3 and flowing in the pipe is sucked and discharged from the upper end opening by the action of the exhaust fan 32. Then, the combustion gas sucked and discharged by the exhaust fan 32 is discharged to the outside of the main body 1 through the exhaust duct 33. An opening 11 for taking in air for blowing is formed in the lower portion of the outer surface of the main body 1, and an air filter 12 is set in the opening 11. Further, in the heat exchange chamber 1, there are mounted annular upper and lower guide plates 24 located in the spiral of the hollow pipe 3. The air blown into the heat exchange chamber 2 from the blower 21 is radially diffused by the guide plate 24, and efficiently contacts the surface of the hollow pipe 3 without passing through the central portion of the spiral. Then, the air that is in contact with the surface of the hollow pipe 3 and is heated by the heat transfer is heated by the heat exchange chamber 3
Is mainly blown to various places as warm air for heating through an air feeding duct 23 connected to the upper part of the.

By the way, in this embodiment, since the spiral shape of the hollow pipe 3 is formed so that the curvature decreases along the flow direction of the combustion gas, the collision angle of the combustion gas with respect to the inner wall of the hollow pipe 3 depends on the combustion gas. It gradually increases along the flow direction. Since the flow velocity of the combustion gas is substantially constant inside the hollow pipe 3, the heat transfer coefficient increases as the collision angle of the combustion gas with the inner wall of the hollow pipe 3 increases. On the other hand, since the temperature of the combustion gas decreases as it flows in the hollow pipe 3, the temperature of the combustion gas decreases even if the heat transfer coefficient increases, so that the hollow pipe 3 is heated substantially uniformly over the entire area. become. On the other hand, the air blown from the blower 21 is uniformly diffused in the heat exchange chamber 2 by the guide plate 24, is uniformly blown to the entire area of the hollow pipe 3, and is uniformly cooled. Therefore, in the hollow pipe 3, both heating of the inner wall and cooling of the surface are uniformly performed over the entire area, so that the temperature does not rise locally.

If the hollow pipe is formed in a spiral shape,
The curvature can be set to be relatively large as compared with the conventional one in which several parts of the hollow pipe are bent. By the way, if the straight part and the bent part are formed separately and they are added together by welding etc. to form a hollow pipe, it takes a lot of man-hours to manufacture the hollow pipe, but if it is formed in a spiral shape, the hollow pipe will be in the middle. Since it can be integrally formed without additional joints, the number of manufacturing steps can be significantly reduced. Further, in the above embodiment, since the combustion gas is sucked out from the inside of the hollow pipe by the exhaust fan 32, the inside of the pipe becomes a negative pressure, and even if a pinhole is generated in the hollow pipe due to corrosion or the like, the combustion gas leaks into the air blow. There is no fear.

By the way, in the above embodiment, the hollow pipe is wound at a constant pitch to form a spiral shape. However, like the hollow pipe 3'shown in FIG. 3, the hollow pipe 3'is arranged along the flow direction of the combustion gas. The pitches P1 to P3 are gradually narrowed, the upstream side is coarsely wound, and the downstream side is tightly wound, the blower resistance of the downstream side portion is made larger than the blower resistance of the upstream side portion, and the air sent from the blower 21 is a hollow pipe. A large amount of water flows to the upstream side of 3,
The combustion gas in the pipe may receive a large amount of heat from the upstream side portion, which is still in a sufficiently high temperature state, to efficiently obtain hot air. In order to increase the air flow resistance on the downstream side, the radius of curvature R1 to the distance from the center line CL of the spiral is
Hollow pipe 3'by increasing the reduction rate of R4 toward the downstream side
May enter more into the inside of the helix on the downstream side.

Further, in the above embodiment, the combustible gas was introduced into the pipe from the end opening of the hollow pipe and the combustible gas was burned in the hollow pipe to generate the combustion gas. However, the combustible gas was generated outside the hollow pipe. There is no problem even if the gas is burned and the high temperature combustion gas generated thereby is caused to flow into the hollow pipe.

[0012]

As is apparent from the above description, when warm air is generated using a hollow pipe heated by high temperature combustion gas flowing in the pipe as a heat source, the temperature of the hollow pipe becomes uniform over the entire area. The hollow pipe is not partially deteriorated.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 II-II sectional view

FIG. 3 is a partial front view showing another embodiment of the hollow pipe.

[Explanation of symbols]

 1 Main body (of hot air generator) 2 Heat exchange chamber 3 Hollow pipe 21 Blower 24 Guide plate 31 Nozzle

Claims (1)

[Claims] 1. A warm air generator in which a hollow pipe for flowing a high-temperature combustion gas in the pipe is provided in the middle of an air passage connected to a blower for warm air blowing, and the radius of curvature of the hollow pipe is continuously changed. A warm air generating device, characterized in that it is formed in a spiral shape and is interposed so that the center line of the spiral substantially coincides with the center line of the air passage.