Hot air generator

Abstract

To provide a compact hot air generator that can efficiently heat gases. [Solution] A hot air generating device that generates hot air by heating a gas, comprising a hot air box having a gas inlet and an outlet, and a heating element including a first heating rod and a second heating rod disposed inside the hot air box, wherein when the distance between the centers of the first heating rod and the second heating rod is S, and the diameters of the first heating rod and the second heating rod are d, the first heating rod and the second heating rod satisfy the following formula (1). S / d≦3····(Formula 1)

Description

Technical Field

[0001] The present invention relates to a hot air generating device.

Background Art

[0002] A hot air generating device is used as a heat source for heating process devices such as mold drying, high-quality plating drying, painting drying, food drying, drug drying, glass tube drying, resin molding preheating, and resin curing heating.

[0003] Patent Document 1 discloses an indirect hot air generating device having a combustion gas generating device for generating combustion gas, a heated gas inlet, a first heat exchanger for heating the air by performing heat exchange between the air introduced from the heated gas inlet and the combustion gas generated by the combustion gas generating device through a partition wall, a hot air outlet for taking out the air heated by the first heat exchanger as hot air, and a combustion gas outlet for discharging the combustion gas used for heating the air in the first heat exchanger as combustion exhaust gas.

[0004] Patent Document 2 discloses a hot air generating device in which a heating element incorporating a heating wire is provided at a discharge portion that discharges air at one end, and a suction port for taking in outside air is formed at the other end of a case body. A front case is formed on the other end side of the heating element, and a blower device for sucking air from the suction port and discharging air from the discharge portion is disposed in the front case. The discharge portion in which the heating element is provided is formed such that its cross-sectional area is smaller than the cross-sectional area of the front case in which the blower device is disposed, and control means for detecting the rotational speed of the motor of the blower device and controlling the energization of the heating element is provided on the other end side of the front case.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The hot air generator described in Patent Document 1 required the installation of a safety device because it uses combustion gas. Therefore, it had problems such as the generation of carbon dioxide and high noise levels during operation.

[0007] In recent years, there has been a demand for compact hot air generators that can efficiently heat gases. Patent Document 2 does not adequately address this issue. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a hot air generating device that (1) generates hot air by heating a gas, comprising a hot air box having a gas inlet and an outlet, and a heating element including a first heating rod and a second heating rod disposed inside the hot air box, wherein when the distance between the centers of the first heating rod and the second heating rod is S, and the diameters of the first heating rod and the second heating rod are d, the first heating rod and the second heating rod satisfy the following formula (1). S / d≦3····(Formula 1)

[0009] (2) The hot air generating device according to (1) above, characterized in that the hot air box is provided with a plurality of heating elements.

[0010] (3) The hot air generating device according to (2) above, characterized in that when a plurality of heating elements arranged in a direction perpendicular to the gas flow direction are defined as a heating element group, and heating element groups adjacent to each other in the gas flow direction are defined as a first heating element group and a second heating element group, the heating elements included in the first heating element group and the heating elements included in the second heating element group are arranged so as not to be adjacent in the gas flow direction.

[0011] (4) The first heating rod and the second heating rod are silicon carbide heating elements, and the hot air generating device according to any one of (1) to (3) above is characterized in this.

[0012] (5) Fins are respectively formed on the first heating rod and the second heating rod, and the hot air generating device according to any one of (1) to (4) above is characterized in this.

Advantages of the Invention

[0013] According to the present invention, a compact hot air generating device capable of efficiently heating a gas can be provided.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic diagram of a hot air generating device. [Figure 2] It is a view taken along arrow A - A when the hot air generating device of FIG. 1 is cut along the chain line C1. [Figure 3] It is a view taken along arrow B - B when the hot air generating device of FIG. 1 is cut along the chain line C2. [Figure 4] It is an enlarged view of a part of the hot air generating device corresponding to the rectangular region SQ in FIG. 1. [Figure 5] It is a plan view of a heating element (First Embodiment). [Figure 6] It is a plan view of a heating element (Second Embodiment). [Figure 7] It is a side view of a heating element (Second Embodiment).

Modes for Carrying Out the Invention

[0015] (First Embodiment) Hereinafter, a first embodiment of the hot air generating device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a hot air generating device. FIG. 2 is a view taken along arrow A - A when the hot air generating device of FIG. 1 is cut along the chain line C1. FIG. 3 is a view of the hot air generating device of FIG. 1 taken along the chain line C2 in the direction of arrow B - B. In these figures, the X-axis, Y-axis, and Z-axis are three mutually perpendicular axes. FIG. 4 is an enlarged view of a part of the hot air generating device corresponding to the rectangular area SQ of FIG. 1. FIG. 5 is a plan view of the heating element.

[0016] Referring to these figures, the hot air generating device 1 includes a hot air box 10 and a heater terminal chamber 20 adjacent to the hot air box 10. The hot air box 10 is cylindrical, and both ends in the X-axis direction are open. Gas is introduced from one opening (corresponding to the gas inlet), and hot air (heated gas) is discharged from the other opening (corresponding to the gas outlet). The type of gas varies according to the application of the hot air generating device 1. When the gas is air, a blower device having a filter such as a blower or a compressor can be used as the blowing means. When the gas is a gas with a specific component, a gas cylinder filled with the gas can be used as the blowing means. When dry air (used in semiconductor devices) is used as the gas, a dry air generating device can be used as the blowing means.

[0017] The outer wall of the hot air box 10 is constituted by a heat insulating wall 10a. However, the wall portion facing the heater terminal chamber 20 is constituted by a shield wall 10b. The heat insulating wall 10a may be ceramic. The shield wall 10b may be a SUS material (for example, SUS304) with excellent heat resistance.

[0018] On the heat insulating wall 10a facing the shield wall 10b in the Y-axis direction, a heating element support portion 10c for supporting the heating element 11 inside the hot air box 10 is provided. The heating element support portion 10c is formed in an L shape, and the number of heating element support portions 10c provided is the same as the number of heating elements 11 housed in the hot air box 10.

[0019] The heating element 11 consists of a first single-phase heating rod 11a (corresponding to the first heating rod), a second single-phase heating rod 11b (corresponding to the second heating rod), and a connecting portion 11c that connects the first single-phase heating rod 11a and the second single-phase heating rod 11b. The first single-phase heating rod 11a and the second single-phase heating rod 11b are aligned in a direction parallel to the X-axis. In other words, the first single-phase heating rod 11a and the second single-phase heating rod 11b are at the same position in the Z-axis direction.

[0020] The first single-phase heating rod 11a and the second single-phase heating rod 11b extend parallel to each other in the Y-axis direction, with one end of each connected by a connector 11c, and the other end extending through the shield wall 10b into the heater terminal chamber 20. In the heater terminal chamber 20, the first single-phase heating rod 11a and the second single-phase heating rod 11b are connected to a power supply (not shown).

[0021] In this embodiment, a U-shaped heating element is formed by connecting the ends of a first single-phase heating rod 11a and a second single-phase heating rod 11b with a connecting portion 11c, but the present invention is not limited to this. For example, the connecting portion 11c may be omitted, and the heating element 11 may be constructed using independent first and second heating rods.

[0022] In this embodiment, a compact hot air generator with excellent gas heating efficiency is realized by strictly defining the positional relationship between the first single-phase heating rod 11a and the second single-phase heating rod 11b. The positional relationship between the first single-phase heating rod 11a and the second single-phase heating rod 11b will be explained with reference to Figure 4. The first single-phase heating rod 11a and the second single-phase heating rod 11b are cylindrical shapes with approximately the same diameter. The cross-sectional center of the first single-phase heating rod 11a is defined as center 111a, and the cross-sectional center of the second single-phase heating rod 11b is defined as center 111b. This cross-section is obtained when the first single-phase heating rod 11a and the second single-phase heating rod 11b are cut in a direction perpendicular to the longitudinal direction (Y-axis direction).

[0023] Let S (hereinafter also be called the center-to-center distance S) be the distance between the center 111a of the first single-phase heating rod 11a and the center 111b of the second single-phase heating rod 11b, and let d (hereinafter referred to as the diameter d) be the diameter of the first single-phase heating rod 11a (second single-phase heating rod 11b). At this time, the first single-phase heating rod 11a and the second single-phase heating rod 11b satisfy the following equation (1). S / d≦3····(Formula 1)

[0024] By arranging the first single-phase heating rod 11a and the second single-phase heating rod 11b to satisfy equation (1), the gas flow becomes turbulent, allowing the gas to be heated efficiently. Furthermore, the increased heating efficiency of the gas allows for a smaller hot air generator. If the heating rods are placed too close together, the heat load will increase, which may lead to a reduced lifespan. Therefore, the lower limit of S / d is preferably 1.25, and more preferably 2.

[0025] The heating element 11 is preferably a ceramic heating element, and more preferably a silicon carbide heating element. Ceramic heating elements are heating elements that efficiently generate heat by utilizing Joule heating caused by electric current. Compared to gas combustion type hot air generators, they produce less carbon dioxide and operate with less noise. Furthermore, they can omit the safety devices required in gas combustion type hot air generators. Ceramic heating elements have superior heat resistance compared to metal heating elements (e.g., nickel-chromium wire), allowing them to be used in higher temperature environments. Furthermore, ceramic heating elements have a rough surface, making them prone to generating turbulence when a gas collides with them. The surface roughness of ceramic heating elements, defined by arithmetic mean roughness Ra, is generally between 3 μm and 50 μm. Sheath heaters, which consist of a metal pipe filled with heating wires and electrical insulation, are less prone to generating turbulence compared to ceramic heating elements because their surfaces are smoother. Silicon carbide heating elements are superior in terms of achieving high capacity among ceramic heating elements, making them the most suitable choice for use among ceramic heating elements.

[0026] A group of heating elements 11 arranged in the Z-axis direction (corresponding to a direction perpendicular to the gas flow direction) is defined as a group of heating elements U. Groups of heating elements U that are adjacent to each other in the gas flow direction (opposite direction to the X-axis direction) are defined as the first group of heating elements and the second group of heating elements.

[0027] In this case, it is desirable that the heating elements 11 included in the first group of heating elements and the heating elements 11 included in the second group of heating elements be arranged so that they are not adjacent in the direction of gas flow. In other words, it is desirable that the heating elements 11 included in the first group of heating elements and the heating elements 11 included in the second group of heating elements be arranged so that their positions in the Z-axis direction are different. This reduces the uneven distribution of heating elements 11 inside the hot air box 10. Furthermore, when the spacing between the heating elements 11 included in the heating element group U in the Z-axis direction is denoted as spacing Kz, spacing Kz is preferably equal. Also, when the spacing between the first heating element group and the second heating element group in the X-axis direction is denoted as spacing Kx, spacing Kx is preferably equal.

[0028] (Second Embodiment) The hot air generator of this embodiment differs from the first embodiment in that fins F are formed on the heating element 11. The other configurations of the hot air generator are the same as in the first embodiment, so a detailed explanation is omitted. Figure 6 is a plan view of the heating element 11 of this embodiment and corresponds to Figure 5. Figure 7 is a side view of the heating element 11. The fins F are arranged in a row at predetermined intervals along the longitudinal direction of the first single-phase heating rod 11a. The predetermined intervals may be equal. When the fins F arranged in a row are defined as a fin group, such fin groups are arranged in two locations in the circumferential direction. In this embodiment, the other fin group is formed at a position 180 degrees away from the other fin group. However, fin groups may be arranged in three or more locations in the circumferential direction.

[0029] Here, it is desirable to position the fins F so that their sides are in contact with the direction of gas flow. This promotes turbulence generation and increases the heat exchange efficiency. The same applies to the second single-phase heating rod 11b. Furthermore, it is desirable that the fins F on the first single-phase heating rod 11a and the second single-phase heating rod 11b be arranged in an alternating pattern (in other words, a staggered pattern). By arranging them in an alternating pattern, turbulence generation can be promoted.

[0030] (Example 1) The present invention will be described in more detail below with reference to examples. A hot air generating device was created in which 18 U-shaped silicon carbide heating elements (diameter d: 30 mm, heating length: 720 mm, end length: 200 mm, center-to-center distance S: 70 mm) were arranged in a space with internal dimensions of W: 850 x H: 800 x L: 1150. The U-shaped silicon carbide heating elements will be referred to as U-shaped heating elements. In adjacent groups of heating elements U in the direction of airflow, the U-shaped heating elements of one group U were arranged so as not to be adjacent to the U-shaped heating elements of the other group U (see Figure 1). This hot air generator has an electrical capacity of 300kW and an air intake volume of 70Nm³. 3 When operated under conditions of / min and an input air temperature of 35°C, the outlet air temperature reached 200°C.

[0031] (Example 2) In the above-mentioned hot air generator, a device similar to that in Example 1 was created, except that the distance S between the centers of the U-shaped silicon carbide heating elements was changed to 85 mm to satisfy equation (1). This hot air generator was then constructed under the same conditions as in Example 1 (electrical capacity 300 kW, input air volume 70 Nm³). 3 When the experiment was conducted at a rate of / min and an input air (IN) temperature of 35°C (in other words, the energy input was the same as in Example 1), the outlet air (OUT) temperature reached 192°C.

[0032] (Comparative Example 1) In the above-mentioned hot air generator, a device similar to that in Example 1 was created, except that the distance S between the centers of the U-shaped silicon carbide heating elements was changed to 100 mm so as not to satisfy equation (1). This hot air generator was then constructed under the same conditions as in Example (electrical capacity 300 kW, input air volume 70 Nm³). 3When the system was operated at a rate of / min and an input air (IN) temperature of 35°C (in other words, the energy input was the same as in the example), the outlet air (OUT) temperature reached 180°C. Therefore, it was found that the embodiment had superior heating efficiency. [Explanation of symbols]

[0033] 1. Hot air generator 10 Hot air box 10a Insulated wall 10b Shield Wall 10c Heating element support section 11 Heating element 11a First single-phase heating rod 11b Second single-phase heating rod 11c connector

Claims

1. A hot air generator that generates hot air by heating a gas, A hot air box having a gas inlet and an outlet, A heating element including a first heating rod and a second heating rod, which are arranged inside the hot air box, It has, When S is the distance between the centers of the first heating rod and the second heating rod, and d is the diameter of the first and second heating rods, The first heating rod and the second heating rod satisfy the following equation (1). S / d≦3...(Formula 1)

2. The aforementioned hot air box is provided with multiple heating elements. The hot air generating device according to feature 1.

3. When a plurality of heating elements arranged in a direction perpendicular to the gas flow direction are defined as a heating element group, and heating element groups adjacent to each other in the gas flow direction are defined as the first heating element group and the second heating element group, The heating elements included in the first group of heating elements and the heating elements included in the second group of heating elements are arranged so as not to be adjacent to each other in the direction of gas flow. The hot air generating device according to feature 2.

4. The first heating rod and the second heating rod are silicon carbide heating elements. A hot air generating device according to any one of the features described in 1 to 3.

5. The hot air generating device according to claim 1 or 2, characterized in that fins are formed on the first heating rod and the second heating rod, respectively.

6. The hot air generating device according to claim 3, characterized in that fins are formed on the first heating rod and the second heating rod, respectively.

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