Insulator tube armored heating tube with resistance heating body made of low-melting-point alloy

Abstract

An insulator tube armored heating tube with a low-melting-point alloy as a resistance heating body is characterized in that the low-melting-point alloy is filled into an insulator tube with a certain length and a certain section geometric dimension, so that the low-melting-point alloy in the insulator tube has a certain resistance value, and metal electrodes are inserted into the two ends of the insulator tube to be in contact with the low-melting-point alloy; one end of the metal electrode is in contact with the low-melting-point alloy, and the other end extends out of the insulator tube and is sealed and packaged to form an insulator tube armored heating tube; after the metal electrode is electrified, the solid-state low-melting-point alloy is used as a resistor body to be heated to be molten, solid-liquid phase change heat storage is performed, and the temperature of the low-melting-point alloy is always at the melting point temperature of the low-melting-point alloy through temperature control; a plurality of insulator tube armored heating tubes with the low-melting-point alloy as the resistance heating body are connected in series, in parallel or in series-parallel composite connection to form a large-area heater; the heating mode of the insulator tube armored heating tube with the low-melting-point alloy as the resistance heating body on a heated object is a combined mode of a non-contact infrared radiation heating mode, a direct contact heat conduction mode and an infrared radiation heating mode. The infrared radiation heating mode is infrared heating of the tube wall of the composite material insulator tube mixed with the high infrared radiation composite oxide powder to a heated object, and infrared heating of the tube wall of the composite material insulator tube mixed with the high infrared radiation composite oxide powder to the heated object, and high infrared radiation composite oxide particles doped in the low-melting-point alloy to the heated object.

Description

Technical Field

[0001] An insulated tube armored heating tube using a low-melting-point alloy as the resistive heating element relates to the field of thermal heating technology. Background Technology

[0002] The heating element in a typical low-temperature heating tube is a resistance wire, and the armored tube is made of stainless steel or quartz glass. Because the surface area of ​​the resistance wire in the heating tube is very small, that is, the area used for heating and heat exchange is very small, and the heating power per unit area needs to be very high, that is, the surface power density of the resistance wire is very high, the temperature of the resistance wire can only be increased. The resistance wire needs to be heated to above 500°C before it can radiate and convect through the stainless steel tube and quartz glass tube to heat the object being heated. In other words, the surface temperature of the stainless steel tube and quartz glass tube is high, so they cannot be used for direct contact heating at temperatures below 300°C. At the same time, due to the small heat capacity of the heating tube, smooth temperature control cannot be achieved.

[0003] This invention discloses an insulated tube-armored heating tube using a low-melting-point alloy as the resistive heating element, which effectively avoids the drawbacks of general low-temperature heating tubes. A low-melting-point alloy tube is inserted into an insulated tube of a certain length and cross-sectional geometry, giving the low-melting-point alloy a specific resistance value. Metal electrodes are inserted into both ends of the insulated tube to contact the low-melting-point alloy. The two ends of the insulated tube are sealed, with one end of the metal electrode contacting the low-melting-point alloy and the other end extending out of the insulated tube, forming an insulated tube-armored heating tube using the low-melting-point alloy as the resistive heating element. When the metal electrodes are energized, the solid low-melting-point alloy acts as a resistive element and is heated to melting, undergoing a solid-liquid phase change for heat storage. Temperature control ensures that the temperature of the low-melting-point alloy remains at its melting point, allowing for direct contact heating of the object being heated. Multiple such insulated tube-armored heating tubes using the low-melting-point alloy as the resistive heating element can be connected in series, parallel, or a combination of series and parallel to form a large-area heater. Summary of the Invention

[0004] An insulated tube armored heating tube using a low-melting-point alloy as the resistive heating element is disclosed. The low-melting-point alloy is inserted into an insulated tube of a certain length and cross-sectional geometry, giving the alloy a specific resistance value. Metal electrodes are inserted into both ends of the insulated tube to contact the low-melting-point alloy. The insulated tube is sealed with one end of the metal electrodes in contact with the alloy and the other end extending out of the tube, forming the insulated tube armored heating tube using the low-melting-point alloy as the resistive heating element. When the metal electrodes are energized, the solid low-melting-point alloy is heated to melting, resulting in a solid-liquid phase change and heat storage. Temperature control maintains the temperature of the low-melting-point alloy at its melting point. The heater consists of multiple insulated tube armored heating tubes with low melting point alloy as the resistive heating element, connected in series, parallel, or a combination of series and parallel connections to form a large-area heater. The heating method of the insulated tube armored heating tube with low melting point alloy as the resistive heating element is a combination of non-contact infrared radiation heating, direct contact heat conduction, and infrared radiation heating. The infrared radiation heating method is infrared heating of the heated object by the insulated tube wall of the composite material incorporating high infrared radiation composite oxide powder, and infrared heating of the heated object by the insulated tube wall in low-temperature molten salt doped with high infrared radiation composite oxide particles.

[0005] The insulating tube is made of polytetrafluoroethylene (PTFE), silicone, or glass. The maximum operating temperature of the PTFE tube is below 270°C, the maximum operating temperature of the silicone tube is 280°C, and the maximum operating temperature of the glass tube is 300°C. The insulating tube is either circular or rectangular.

[0006] The aforementioned insulating tube is formed by mixing 5% to 25% by volume of composite oxide powders of ferric oxide, manganese dioxide, copper oxide, chromium trioxide, and cobalt oxide with high infrared emissivity and an average particle size of less than 2 micrometers during the molding process. This mixture forms polytetrafluoroethylene (PTFE) composite material and silicone composite material, which are then extruded to form PTFE composite tubes and silicone composite tubes with high infrared emissivity. This improves the infrared radiation heating efficiency of the heating tube with insulator-clad low-temperature molten salt as the resistance heating element.

[0007] The composite oxide powder used for mixing polytetrafluoroethylene composite materials and silicone composite materials is a mixture of oxides with the following weight fractions: 10%~30% ferric oxide, 50%~70% manganese dioxide, 7.5%~12.5% ​​copper oxide, 2.5%~5% chromium trioxide, and 7.5%~12.5% ​​cobalt oxide. The oxides are ground to an average particle size of less than 2 micrometers, then calcined at 1000℃~1200℃, crushed, ground again to an average particle size of less than 2 micrometers, and dried before being used for mixing polytetrafluoroethylene composite materials and silicone composite materials.

[0008] The low-melting-point alloy is a low-melting-point alloy composed of two, three, or four metals selected from Bi, Pb, Sn, and Cd, with a melting point of 145℃~200℃. The composition of the low-melting-point alloy is designed based on the binary, ternary, or quaternary phase diagrams of Bi, Pb, Sn, and Cd, according to the isothermal heating temperature of the heated object. The melting point of the low-melting-point alloy is controlled, and its melting point temperature is the controlled isothermal temperature of the heating tube. Typical low-melting-point alloys include: Pb 32% Sn 50% Cd 8% melting point: 145℃; Bi 50% Pb 50% melting point: 160℃; Pb 38% Sn 62% melting point: 183℃; and Bi 20% Sn 80% melting point: 200℃.

[0009] The low-melting-point alloy is a low-melting-point alloy-based composite material. This composite material is a mixture of the low-melting-point alloy and composite oxide particles (iron oxide, manganese dioxide, copper oxide, chromium oxide, and cobalt oxide) with high infrared emissivity and a particle size of 0.2 mm to 1 mm, comprising 40% to 65% of the volume of the insulating tube. After melting, the low-melting-point alloy fills the gaps between the composite oxide particles. The non-conductivity and volume percentage of the composite oxide particles are used to adjust and control the resistance value of the low-melting-point alloy inside the insulating tube armored heating tube, thereby controlling the heating power under constant voltage and improving the infrared radiation heating efficiency of the insulating tube heater.

[0010] The composite oxide particles used in the low-melting-point alloy-based composite material are a mixture of oxides with a weight fraction of 10%~30% ferric oxide, 50%~70% manganese dioxide, 7.5%~12.5% ​​copper oxide, 2.5%~5% chromium trioxide, and 7.5%~12.5% ​​cobalt oxide. The oxides are ground to an average particle size of less than 2 micrometers, then calcined at 1000℃~1200℃, crushed and pulverized to a particle size of 0.2mm~1mm, and dried before being used in the manufacture of the low-melting-point alloy composite material.

[0011] The low-melting-point alloy is cast or extruded into a circular or rectangular cylinder with a diameter slightly smaller than the internal geometric dimensions of the insulating tube and a length 1 to 2 times its geometric dimensions. The circular or rectangular cylinders are placed one by one into the insulating tube to the designed length. The electrodes are vacuum-sealed and placed in a heating furnace and heated until the low-melting-point alloy is completely melted and in contact with the metal electrodes. The heating tube, which is armored with the low-temperature molten salt as the resistance heating element, is placed into a mold and cooled to form an insulated tube armored heating tube with the low-melting-point alloy as the resistance heating element.

[0012] The alloy powder of the melting point alloy is mixed evenly with a certain proportion of the composite oxide particles, and then pressed into a press mold to form a circular or rectangular cylinder with a diameter slightly smaller than the internal geometric dimensions of the insulating tube and a length 1 to 2 times its geometric dimensions. The circular or rectangular cylinders are placed one by one into the insulating tube to the designed length. The metal electrode is vacuum sealed and placed in a heating furnace and heated until the low melting point alloy is completely melted and fills the gaps between the composite oxide particles and contacts the metal electrode. The heating tube armored with the low melting point alloy as the low-temperature molten salt resistance heating element is placed into a mold and cooled to form an insulated tube armored heating tube with the low melting point alloy resistance heating element, which is convenient for installation.

Claims

1. An insulated tube armored heating tube using a low-melting-point alloy as a resistive heating element, characterized in that: a low-melting-point alloy is inserted into an insulated tube of a certain length and cross-sectional geometry, giving the low-melting-point alloy in the insulated tube a certain resistance value; metal electrodes are inserted into both ends of the insulated tube to contact the low-melting-point alloy; the two ends of the insulated tube are sealed with one end of the metal electrode in contact with the low-melting-point alloy and the other end extending out of the insulated tube to form an insulated tube armored heating tube; when the metal electrodes are energized, the solid low-melting-point alloy is heated to melt as a resistive element, and heat is stored through a solid-liquid phase change; the temperature of the low-melting-point alloy is kept at its melting point temperature by temperature control. Multiple insulating tube armored heating tubes with low melting point alloy as resistance heating element are connected in series, parallel, or a combination of series and parallel to form a large-area heater; the heating method of the insulating tube armored heating tube with low melting point alloy as resistance heating element is a combination of non-contact infrared radiation heating, direct contact heat conduction, and infrared radiation heating. The infrared radiation heating method is infrared heating radiated by the composite material insulating tube wall mixed with high infrared radiation composite oxide powder to the heated object, and infrared heating radiated by the low melting point alloy doped with high infrared radiation composite oxide particles to the heated object.

2. According to claim 1, the insulating tube is: a polytetrafluoroethylene tube, a silicone tube, or a glass tube; the insulating tube is a circular tube or a rectangular tube.

3. According to claim 1, the insulator tube is made by mixing 5% to 25% by volume of composite oxide powders of ferric oxide, manganese dioxide, copper oxide, chromium trioxide, and cobalt oxide with high infrared emissivity and an average particle size of less than 2 micrometers during the molding process of the insulator tube to form polytetrafluoroethylene composite material and silicone composite material, which are then extruded to form polytetrafluoroethylene composite material tube and silicone composite material tube with high infrared emissivity, so as to improve the infrared radiation heating efficiency of the heating tube with insulator tube armored low temperature molten salt as resistance heating element.

4. According to claim 1, the composite oxide powder is a mixture of oxides with the following weight fractions: 10%~30% ferric oxide, 50%~70% manganese dioxide, 7.5%~12.5% ​​copper oxide, 2.5%~5% chromium trioxide, and 7.5%~12.5% ​​cobalt oxide. The mixture is ground to an average particle size of less than 2 micrometers, then calcined at 1000℃~1200℃, crushed, ground again to an average particle size of less than 2 micrometers, and dried before being used in the mixing of the polytetrafluoroethylene composite material and the silicone composite material.

5. According to claim 1, the low-melting-point alloy is a low-melting-point alloy composed of two, three, or four metals selected from Bi, Pb, Sn, and Cd, with a melting point of 145℃~200℃. The composition of the low-melting-point alloy is designed based on the binary, ternary, or quaternary phase diagrams of Bi, Pb, Sn, and Cd according to the isothermal heating temperature of the heated object, and the melting point of the low-melting-point alloy is controlled. The melting point temperature of the low-melting-point alloy is the controlled isothermal temperature of the heating tube.

6. According to claim 1, the low-melting-point alloy is a low-melting-point alloy-based composite material, wherein the low-melting-point alloy-based composite material is a mixture of the low-melting-point alloy and composite oxide particles of ferric oxide, manganese dioxide, copper oxide, chromium oxide, and cobalt oxide with high infrared emissivity and a particle size of 0.2 mm to 1 mm, comprising 40% to 65% of the volume of the insulating tube. After melting, the low-melting-point alloy fills the gaps between the composite oxide particles. The non-conductive nature and volume percentage of the composite oxide particles are used to adjust and control the resistance value of the low-melting-point alloy inside the insulating tube armored heating tube, i.e., the heating power under constant voltage and to improve the infrared radiation heating efficiency of the insulating tube heater.

7. According to claim 1, the composite oxide particles are a mixture of oxides with a weight fraction of 10%~30% ferric oxide, 50%~70% manganese dioxide, 7.5%~12.5% ​​copper oxide, 2.5%~5% chromium trioxide, and 7.5%~12.5% ​​cobalt oxide, which are ground to an average particle size of less than 2 micrometers, calcined at 1000℃~1200℃, crushed and pulverized to a particle size of 0.2mm~1mm, and dried before being used in the manufacture of the low melting point alloy composite material.

8. According to claim 1, the low-melting-point alloy is cast or extruded into a circular or rectangular cylinder with a diameter slightly smaller than the internal geometric dimensions of the insulating tube and a length 1 to 2 times its geometric dimensions. The circular or rectangular cylinders are placed one by one into the insulating tube to the designed length. The electrodes are vacuum-sealed and placed in a heating furnace and heated until the low-melting-point alloy is completely melted and in contact with the metal electrodes. The insulated tube armored heating tube with the completely melted low-melting-point alloy is placed in a mold and cooled to form an insulated tube armored heating tube with the low-melting-point alloy as the resistive heating element.

9. According to claim 1, the alloy powder of the low melting point alloy is mixed evenly with a certain proportion of the composite oxide particles, and then pressed into a press mold to form a circular or rectangular cylinder slightly smaller than the internal geometric dimensions of the insulator tube and with a length 1 to 2 times its geometric dimensions. The circular or rectangular cylinders are then placed one by one into the insulator tube to the designed length. The metal electrode is then vacuum-sealed and placed in a heating furnace and heated until the low melting point alloy is completely melted and fills the gaps between the composite oxide particles, and the low melting point alloy contacts the metal electrode. The insulator tube armored heating tube, after the low melting point alloy is completely melted, is placed in a mold and cooled to form an insulator tube armored heating tube with the low melting point alloy as the resistive heating element, which is convenient for installation.