JP2002033183A - Heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device capable of efficiently performing heat exchange. SOLUTION: This heating device comprises a metallic cylindrical tube 2 slightly smaller in diameter than a nonmetallic cylindrical tube 1 concentrically arranged on the inside of the cylindrical tube 1, and the cylindrical tube 2 is heated to a prescribed temperature by a proper means to heat a gas forcedly blown and passed into the cylindrical tube 1. A bar-like fluid shielding matter 3 slightly smaller in diameter than the cylindrical tube 2 is concentrically arranged on the inside of the cylindrical tube 2, so that the gas passing in the cylindrical tube 1 is passed through slight clearances between the cylindrical tube 1 and the cylindrical tube 2 and between the cylindrical tube 2 and the shielding matter 3 at high speed, whereby the heat exchange can be efficiently performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a heat exchanger of a heating apparatus for heating a gas such as air or gas.

[0002]

2. Description of the Related Art In such a conventional heating apparatus for heating a fluid, when a metal pipe is heated and a fluid is passed through a pipe to perform heating, the heat transfer coefficient when the fluid is a liquid is as follows. 250 to 5000 kcal / m ² hr ° C., and the heat transfer coefficient when the fluid is gas is 10 to 250 kcal / m ² h.
r ° C., which is a large difference.

The amount of heat transfer is calculated by the following equation. When heating a metal tube to heat a fluid passing therethrough, it can be seen from the following equation that the liquid can be heated easily, but the gas cannot be heated easily.

Q = α × S × (T ₁ −T ₂ ) (1) Q: Heat transfer amount T ₁ : Temperature of high temperature part α: Heat transfer coefficient T ₂ : Temperature of low temperature part S: Area Therefore, when heating a gas, in order to obtain a heat transfer amount, the area of the high temperature part is increased as a conventional method. Or,
The method of keeping the temperature of the high temperature part high was common. This increases the size of the heat exchanger. Alternatively, there has been a problem that the structure of the heat exchanger is complicated in order to maintain the high temperature portion at a higher temperature.

[0005]

In the above equation ( ₁ ), the method of increasing the heat transfer amount (Q) without changing the temperature (T ₁ ) and the electric heating area (S) of the high-temperature portion increases the heat transfer coefficient (α). It turns out that it is effective to do so.

[0006] One way to increase the heat transfer coefficient is to increase the velocity of the fluid flowing along the hot surface.

As a method of increasing the passage speed by flowing a gas in a pipe, there is a method of increasing the amount of air passing through the pipe. In this method, the heat transfer coefficient increases, and the amount of heat transfer increases. There is a problem that the temperature of the fluid cannot be expected to rise due to an increase in the air volume.

When the diameter of the pipe is reduced, the velocity of the fluid is increased and the heat transfer coefficient is increased. However, the heat transfer area is reduced by reducing the diameter of the pipe, thereby reducing the heat transfer area. In order to cover this, it is necessary to increase the length of the tube to secure a heat transfer area. However, when the length of the tube is increased, there is a problem that the means for heating the tube becomes large.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made to increase the flow rate without changing the temperature and heat transfer area of the high-temperature portion and without increasing the gas passage amount. The heat transfer rate is increased by increasing the heat transfer coefficient.

[0010] For this purpose, the present invention provides a metal cylindrical tube inside a nonmetallic cylindrical tube and a rod-shaped fluid shield inside the metal cylindrical tube so that the metal cylindrical tube can be brought to a predetermined temperature. Heat is exchanged efficiently by heating and passing gas at a high speed through these gaps.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to arrange a metal cylindrical tube slightly smaller in diameter than a nonmetallic cylindrical tube on the concentric circle inside the nonmetallic cylindrical tube, In a heating device that heats a gas that is forcibly blown and passed through a non-metallic cylindrical tube by heating to a predetermined temperature at
A rod-shaped fluid shield with a diameter slightly smaller than that of the metal cylindrical tube is arranged concentrically inside the metal cylindrical tube, and the gas passing through the non-metal cylindrical tube is between the non-metal cylindrical tube and the metal cylindrical tube and The heat exchange is performed efficiently by passing through a small gap between the metal cylindrical tube and the rod-shaped fluid shield at a high speed.

Further, the rod-shaped fluid shield provided inside the metal cylindrical tube has both ends formed in a conical shape so that the gas passing through the gap between the metal cylindrical tube and the rod-shaped fluid shield at a high speed can be prevented. The heating device has a reduced flow path resistance.

According to the present invention, an electromagnetic induction heating coil is provided outside a nonmetallic cylindrical tube, the metal cylindrical tube is heated by electromagnetic induction heating, and the temperature of the metal cylindrical tube is detected to control the electromagnetic induction heating. The temperature of the metal cylindrical tube can be controlled to a predetermined temperature by feeding back to the above.

A gas is forcibly blown along a metal cylindrical tube controlled at a predetermined temperature, and the tube is provided inside the metal cylindrical tube as a means for increasing the wind speed of the gas and increasing the heat transfer coefficient. A rod-shaped fluid shield with a slightly smaller diameter is arranged concentrically, and gas passing through the non-metallic cylindrical tube has a small gap between the non-metallic cylindrical tube and the metal cylindrical tube, and a small gap between the metal cylindrical tube and the fluid shield. The heat transfer rate is increased by passing at a high speed, and the heat transfer area is increased by flowing air to both sides of the metal cylindrical tube to efficiently exchange heat.

[0015] Further, the rod-shaped fluid shield provided inside the metal cylindrical pipe has both ends conical so as to reduce the flow path resistance against gas passing through the gap between the metal cylindrical pipe and the rod-shaped fluid shield. This has the advantage that there is no need to increase the size of the blower that sends gas.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic structural view of a heating device showing one embodiment of the present invention. FIG. 2 is a schematic structural view of a heating apparatus showing another embodiment.

In FIG. 1, reference numeral 1 denotes a non-metallic cylindrical tube (hereinafter referred to as a non-metallic tube), and reference numeral 2 denotes a metal cylindrical tube (hereinafter referred to as a non-metallic tube 1) having a diameter slightly smaller than that of the non-metallic tube 1 disposed inside the non-metallic tube 1. Metal tube). The metal tube 2 is arranged concentrically with the non-metal tube 1. Reference numeral 3 denotes a rod-shaped fluid shield slightly smaller in diameter than the metal tube 2 disposed inside the metal tube 2, and is disposed on a concentric circle of the metal tube 2.

Reference numeral 4 denotes a heating coil for performing electromagnetic induction heating as one means for heating the metal tube 2, and is provided on the outer peripheral portion of the non-metal tube 1. Reference numeral 5 denotes a blower that sends gas, for example, air around the heated metal tube 2. Reference numeral 6 denotes a cooling fan for sending cooling air to cool the heating coil 4 provided on the outer peripheral portion of the non-metallic tube 1. 7, the cooling air sent from the cooling fan 6 ensures that the heating coil 4
It is an air blowing guide to be sent to.

Reference numeral 8 denotes a temperature detector attached to a terminal of the metal tube 2, which detects the temperature of the metal tube 2 and sends a signal to a control unit 9 of the electromagnetic induction heater to control heating, thereby controlling the heating. Is controlled to a predetermined temperature.

In FIG. 2, reference numeral 3 'denotes a rod-shaped fluid shield slightly smaller in diameter than the metal tube 2 disposed inside the metal tube 2, and both ends are formed in a conical shape. This is a shape for reducing the resistance to the gas flowing around and minimizing the pressure loss. Other configurations are the same as those in FIG.

Next, the operation of the present embodiment having the above configuration will be described.

By operating the control unit 9 of the electromagnetic induction heating apparatus, the heating coil 4 is energized to supply a high-frequency current to heat the metal tube 2. When the temperature of the metal tube 2 rises, the temperature detector 8 detects this and sends a signal to the control unit 9 to control the heating, so that the temperature of the metal tube 2 is maintained at a predetermined temperature.

Next, when the blower 5 is operated, the gas sent from the blower 5 is slightly heated between the non-metallic tube 1 and the metallic tube 2 and between the metallic tube 2 and the rod-shaped fluid shield 3, that is, heated. Flows around the metal tube 2 at high speed. When the gas flows at a high speed, the number of Reynold nozzles increases, the heat transfer coefficient also increases, and the heat transfer amount also increases.

When the amount of air blown out from the blower 5 is the same, for example, when the rod-shaped fluid shield 3 inside the metal tube 2 is not provided, the cross-sectional area through which the gas passes increases, the flow velocity decreases, and the number of Reynolds nozzles decreases. The transmissivity also decreases and the amount of heat transfer decreases. In addition, since the gas also flows in a place where resistance to the flow is small, it flows in the center of the tube far from the high-temperature metal tube 2, and if it passes therethrough without contacting the high-temperature metal tube 2, heat cannot be transferred. Results.

Therefore, in the present invention, by disposing the rod-shaped fluid shield 3 inside the metal tube 2, the gas passage area is reduced, the flow velocity is increased, and all the flowing gas is heated to a high temperature. Therefore, heat is sufficiently transferred from the high-temperature metal tube 2 to the gas.

In the embodiment shown in FIG. 2, gas is formed between the rod-shaped fluid shield 3 ′ and the metal tube 2 by forming the front and rear ends of the rod-shaped fluid shield 3 ′ in a streamlined shape (conical shape). Since the gas flow becomes smooth without flowing into the slight gap between the gaps and after passing through the gap and disturbing the gas flow, the resistance is small, the pressure loss due to the flow is small, and the gas flow is 2, the gas and the metal tube 2 are sufficiently brought into contact with each other to ensure heat transfer.

When heat is transferred from the metal tube 2 to the gas, the temperature of the metal tube 2 decreases. This is detected by the temperature detector 8 and fed back to the control unit 9 of the electromagnetic induction heating device. As a result, a high-frequency current is supplied to the heating coil 4 so that the metal tube 2 is heated and heating control for maintaining a predetermined temperature is performed.

When a high-frequency current flows through the heating coil 4, the metal tube 2 is heated and the temperature of the heating coil 4 also rises due to self-heating. If the temperature of the heating coil 4 rises abnormally, the electric resistance of the heating coil 4 will fall and a high-frequency current will flow abnormally, leading to a failure of the electromagnetic induction heating device. Therefore, it is necessary to keep the temperature of the heating coil 4 below a predetermined temperature. For this reason, when the electromagnetic induction heating device is operated, the cooling fan 6 is operated to blow cold air in the atmosphere onto the heating coil 4, and the heat generated in the heating coil 4 is radiated to the atmosphere to reduce the temperature of the heating coil 4. It is to keep at a predetermined temperature.

If the non-metallic tube 1 is made of a material having a very low thermal conductivity, such as a ceramic pipe, the temperature of the heating coil 4 side hardly rises even if the inside of the non-metallic tube 1 is at a high temperature. Even if the metal tube 2 is maintained at a high temperature, the temperature of the heating coil 4 does not increase.

[0030]

According to the present invention, by disposing a rod-shaped fluid shield inside a metal pipe, the gas passage area is reduced, the flow velocity is increased, and all the flowing gas flows along the metal pipe heated to a high temperature. As a result, the heat is sufficiently transferred from the high-temperature metal pipe to the gas.

Further, by forming the front end and the rear end of the rod-shaped fluid shield into a streamlined shape, when gas flows into a small gap between the rod-shaped fluid shield and the metal tube and after passing through the gap, a vortex is generated to generate gas. Since the flow does not disturb and the flow of the gas becomes smooth, the resistance is small and the pressure loss due to the flow is small.

If the non-metallic tube is made of a material having a very low thermal conductivity, such as a ceramic pipe, the temperature of the heating coil side does not rise even if the inside of the non-metallic tube is at a high temperature. Even if maintained, the temperature of the heating coil does not rise.

Further, the metal pipe provided inside the non-metal pipe is in a floating state without contacting the non-metal pipe, and gas flows through the gap between the non-metal pipe and the metal pipe. Even though the high temperature is not conducted to the non-metallic tube, wasteful heat is not dissipated from the metal tube and the non-metallic tube is not heated. It will improve.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of a heating device showing one embodiment of the present invention.

FIG. 2 is a schematic structural view of a heating device showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-metallic cylindrical pipe (non-metallic pipe) 2 Metallic cylindrical pipe (metallic pipe) 3 Rod-shaped fluid shield 4 Heating coil 5 Blower

Claims (2)

[Claims] 1. A metal cylindrical tube (2) having a diameter slightly smaller than that of the nonmetallic cylindrical tube (1) inside the nonmetallic cylindrical tube (1).
Are arranged concentrically, the metal cylindrical tube (2) is heated to a predetermined temperature by appropriate means, and the gas which is forcibly blown through the non-metallic cylindrical tube (1) and passes therethrough is heated. In the apparatus, a rod-shaped fluid shield (3) having a diameter slightly smaller than that of the metal cylindrical tube (2) is arranged concentrically inside the metal cylindrical tube (2), and the inside of the non-metallic cylindrical tube (1) is disposed. The passing gas passes through a small gap between the non-metallic cylindrical pipe (1) and the metallic cylindrical pipe (2) and a small gap between the metallic cylindrical pipe (2) and the rod-shaped fluid shield (3) at a high speed, thereby being efficient. A heating device characterized by a structure that exchanges heat well. 2. A cylindrical fluid pipe (2) and a rod-shaped fluid shield (3), wherein both ends of a rod-shaped fluid shield (3) provided inside a metal cylindrical pipe (2) are formed in a conical shape. 2. The heating device according to claim 1, wherein the flow path resistance is reduced for a gas passing through the gap between the high-speed and high-speed.