Heating tube with insulating coating and method for processing an insulating coating

Abstract

The application relates to a heating pipe with an insulating coating and a processing method of the insulating coating, which comprises a heat-conducting insulating pipe, a silver electrode fixed on the outer side of the upper end and the lower end of the heat-conducting insulating pipe, an electric heating film coated on the outer side of the heat-conducting insulating pipe, the electric heating film being arranged between the two silver electrodes, the upper side edge and the lower side edge of the electric heating film being respectively in conduction with the two silver electrodes, and the electric heating film and the two silver electrodes being further coated with an insulating coating, the insulating coating being coated and sintered by a mixture of low-temperature glass powder, aluminum oxide powder, acidic aluminum phosphate and water glass; the application prolongs the service life of the electric heating film, greatly improves the thermal shock stability of the electric heating film, simultaneously plays a heat preservation and heat insulation role to improve the thermal efficiency; in addition, a temperature controller can be directly attached on the insulating coating to closely sense the temperature change, so that the response time of the temperature controller is shortened to eliminate the safety hidden danger.

Description

TECHNICAL FIELD

[0001] The present application relates to a heating tube with an insulating coating and a processing method of the insulating coating. BACKGROUND

[0002] Most of the rapid heating water heaters use ceramic or quartz glass heating tubes as heat sources. The ceramic or quartz glass heating tube uses the principle that the electric heating film coated on the surface of the tube body generates heat after being electrified to heat the water flowing through the tube. The electric heating film on the existing heating tube directly contacts with the outside world. The water vapor and dust in the air are easy to oxidize the electric heating film, and then cause the electric heating film to corrode, resulting in a shorter service life of the electric heating film. Moreover, the electric heating film is easy to crack when the environmental temperature changes sharply, so the thermal shock stability is poor. At the same time, a large part of the heat generated by the electric heating film is lost to the outside, resulting in a low thermal efficiency. In addition, because the electric heating film is electrified after being electrified, the temperature controller cannot be directly installed on the surface of the electric heating film. The temperature controller can only be installed away from the electric heating film, so that the temperature controller cannot sense the surface temperature of the electric heating film at close range, resulting in a long response time of the temperature controller. In case of dry burning without water in the tube, the temperature controller cannot quickly sense the temperature change, which has a security risk and needs to be further improved. SUMMARY

[0003] In view of the above status of the prior art, the technical problem to be solved by the present application is to provide a heating tube with an insulating coating and a processing method of the insulating coating, which prolongs the service life of the electric heating film, greatly improves the thermal shock stability of the electric heating film, improves the thermal efficiency, and eliminates the security risk.

[0004] The technical scheme adopted by the present application to solve the above technical problem is: a heating tube with an insulating coating, characterized in that it comprises a heat-conducting insulating tube, one silver electrode is fixedly sleeved on the outer side of each of the upper and lower ends of the heat-conducting insulating tube, an electric heating film is coated on the outer side of the heat-conducting insulating tube, the electric heating film is arranged between the two silver electrodes, the upper and lower side edges of the electric heating film are respectively in conductive communication with the two silver electrodes, and an insulating coating is further coated on the outside of the electric heating film and the two silver electrodes, the thickness of the insulating coating is 15-25 um, and the insulating coating is formed by coating and sintering a mixture of low-temperature glass powder, aluminum oxide powder, acidic aluminum phosphate and water glass.

[0005] Preferably, the material of the heat-conducting insulating tube is ceramic or quartz glass.

[0006] Preferably, the processing method of the insulating coating of the heating tube, characterized in that it comprises the following steps:

[0007] (1) mixing low-temperature glass powder and aluminum oxide powder in a certain proportion to form a powder mixture;

[0008] (2) adding the powder mixture into a ball mill to perform ball milling to form a ball-milled mixture;

[0009] (3) adding the ball-milled mixture and the acidic aluminum phosphate into the water glass in proportion and uniformly stirring to prepare a slurry;

[0010] (4) screen printing the slurry on the surface of the heat-conducting insulation tube by means of a screen plate to form an insulation slurry layer;

[0011] (5) placing the heat-conducting insulation tube with the insulation slurry layer screen-printed thereon into a high-temperature tunnel kiln to sequentially perform preheating, medium-temperature sintering, high-temperature sintering and temperature decreasing and cooling to form a product.

[0012] Preferably, the low-temperature glass powder in the step (1) has a mass percentage of 94% to 96%, and the alumina powder has a mass percentage of 4% to 6%.

[0013] Preferably, the ball-milled mixture in the step (2) has a particle size of less than 50 um.

[0014] Preferably, the ball-milled mixture, the acidic aluminum phosphate and the water glass in the step (3) have volume percentages of 90%, 2% and 8% respectively.

[0015] Preferably, the screen plate in the step (4) has a fineness of 180 to 250 meshes.

[0016] Preferably, the insulation slurry layer in the step (4) has a thickness of 25 to 35 um.

[0017] Preferably, the preheating, the medium-temperature sintering and the temperature decreasing and cooling in the step (5) each have a time of 3 minutes, and the high-temperature sintering has a time of 6 minutes.

[0018] Preferably, the medium-temperature sintering in the step (5) has a temperature of 200℃, and the high-temperature sintering has a temperature of 850℃.

[0019] Compared with the prior art, the advantages of the present application are as follows: the insulation coating of the present application can isolate the electrothermal film from air, so that the water vapor and dust in the air cannot contact the surface of the electrothermal film, thereby preventing the surface of the electrothermal film from being oxidized, and prolonging the service life of the electrothermal film; the insulation coating has a low thermal expansion coefficient, can effectively buffer the deformation of the electrothermal film, and even when the environmental temperature changes sharply, the electrothermal film will not crack, thereby greatly improving the thermal shock stability of the electrothermal film, and effectively preventing the heat generated by the electrothermal film from being lost to the outside, thereby playing a role of heat preservation and insulation to improve the thermal efficiency; in addition, the temperature controller can be directly attached to the insulation coating to closely sense the temperature change, thereby shortening the response time of the temperature controller to eliminate safety hazards. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1A structural diagram of the present application;

[0021] Fig. 2 A sectional structural diagram at a silver electrode of the present application. DETAILED DESCRIPTION

[0022] Unless otherwise defined, technical and scientific terms used herein should have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein should be interpreted in accordance with the customary and regular meaning of the term. The use of "first", "second" and similar terms does not imply any order, quantity, or importance, but is merely used to distinguish one element from another. The use of "comprise", "comprises" or "comprising" and similar terms is intended to mean that the elements listed after the word encompass not only those elements listed but also other similar elements. The use of "connected", "coupled", or similar terms does not limit the term to a direct or mechanical connection, but can include an electrical connection, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are used only to indicate relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0023] In order to keep the following description of the embodiments of the present application clear and concise, the detailed description of known functions and known components is omitted.

[0024] As shown in Figs. 1-2 A heating tube with an insulating coating, comprising a heat-conducting insulating tube 1, a silver electrode 2 is fixed on the outer side of the upper and lower ends of the heat-conducting insulating tube 1, an electric heating film 3 is coated on the outside of the heat-conducting insulating tube 1, the electric heating film 3 is arranged between the two silver electrodes 2, the upper and lower side edges of the electric heating film 3 are respectively in conduction with the two silver electrodes 2, the electric heating film 3 and the two silver electrodes 2 are further coated with an insulating coating 4, the thickness of the insulating coating 4 is 15-25 um, and the material of the heat-conducting insulating tube 1 is ceramic or quartz glass.

[0025] The insulating coating 4 is coated and sintered by a mixture of low-temperature glass powder, aluminum oxide powder, acidic aluminum phosphate, and water glass.

[0026] In use, the positive and negative poles of the power supply are connected with the two silver electrodes 2 respectively, and then the upper and lower sides of the electric heating film 3 are powered, the electric heating film 3 generates heat after being powered and conducts the heat to the heat-conducting insulation pipe 1, when the water flow passes through the heat-conducting insulation pipe 1, the heat on the heat-conducting insulation pipe 1 is conducted to the water flow, so as to heat the water; the insulation coating 4 insulates the electric heating film 3 from the air, so that the surface of the electric heating film 3 is not easy to be oxidized, thereby prolonging the service life of the electric heating film 3; and the insulation coating 4 has low thermal expansion coefficient, which improves the thermal shock stability of the electric heating film 3, and can effectively play a heat preservation and insulation role, thereby improving the thermal efficiency; in addition, the temperature controller can be directly attached to the insulation coating 4, thereby sensing the temperature change at close range, so as to shorten the response time of the temperature controller and eliminate the safety hazard.

[0027] The processing method of the insulation coating 4 is as follows:

[0028] (1) The low-temperature glass powder and the aluminum oxide powder are mixed in proportion to form a powder mixture; the mass percentage of the low-temperature glass powder is 94%-96%, and the mass percentage of the aluminum oxide powder is 4%-6%.

[0029] (2) The powder mixture is added to the ball mill for ball milling to form a ball-milled mixture, and the particle size of the ball-milled mixture is less than 50um.

[0030] (3) The ball-milled mixture and the acidic aluminum phosphate are added to the water glass in proportion and uniformly stirred to adjust the slurry; the volume percentages of the ball-milled mixture, the acidic aluminum phosphate and the water glass are 90%, 2% and 8% respectively.

[0031] (4) The slurry is silk-screen printed on the surface of the heat-conducting insulation pipe 1 by means of a screen plate with fineness of 180-250 meshes to form an insulation slurry layer; the thickness of the insulation slurry layer is 25-35um.

[0032] (5) The heat-conducting insulation pipe 1 with the insulation slurry layer silk-screen printed thereon is placed in a high-temperature tunnel kiln and sequentially subjected to preheating, medium-temperature sintering, high-temperature sintering and cooling to form; the time of preheating, medium-temperature sintering and cooling is 3 minutes, and the time of high-temperature sintering is 6 minutes; the temperature of medium-temperature sintering is 200℃; the temperature of high-temperature sintering is 850℃.

[0033] The insulating coating 4 of the present application can isolate the electrothermal film 3 from air, so that the water vapor and dust in the air cannot contact the surface of the electrothermal film 3, thereby preventing the surface of the electrothermal film 3 from being oxidized, thereby prolonging the service life of the electrothermal film 3; and the thermal expansion coefficient of the insulating coating 4 is relatively low, which can effectively buffer the deformation of the electrothermal film 3, so that the electrothermal film will not crack even when the environmental temperature changes sharply, thereby greatly improving the thermal shock stability of the electrothermal film 3, and also effectively preventing the heat generated by the electrothermal film 3 from being lost to the outside, thereby playing a heat preservation and insulation role to improve the thermal efficiency; in addition, the temperature controller can be directly attached to the insulating coating 4 to closely sense the temperature change, thereby shortening the response time of the temperature controller to eliminate safety hazards.

[0034] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A heating tube having an insulating coating, characterized by, The heating pipe comprises a heat-conducting insulating tube, a silver electrode is fixed on the outer side of the upper and lower ends of the heat-conducting insulating tube, an electric heating film is coated on the outer side of the heat-conducting insulating tube, the electric heating film is arranged between the two silver electrodes, the upper and lower side edges of the electric heating film are respectively in conduction with the two silver electrodes, the electric heating film and the two silver electrodes are further coated with an insulating coating, the thickness of the insulating coating is 15-25 microns, and the insulating coating is formed by coating and sintering a mixture of low-temperature glass powder, alumina powder, acidic aluminum phosphate and water glass; The processing method of the insulating coating of the heating pipe comprises the following steps: (1) mixing low-temperature glass powder and alumina powder in a certain proportion to form a powder mixture; (2) adding the powder mixture into a ball mill to perform ball milling to form a ball-milled mixture; (3) adding the ball-milled mixture and acidic aluminum phosphate into water glass in a certain proportion and uniformly stirring to form a slurry; (4) screen printing the slurry on the surface of the heat-conducting insulating tube by means of a screen plate to form an insulating slurry layer; (5) placing the heat-conducting insulating tube with the insulating slurry layer screen-printed thereon into a high-temperature tunnel kiln to sequentially perform preheating, medium-temperature sintering, high-temperature sintering and cooling to form a final product; The temperature of the medium-temperature sintering in the step (5) is 200 DEG C, and the temperature of the high-temperature sintering is 850 DEG C.

2. The heating tube having an insulating coating according to claim 1, characterized by The material of the heat-conducting insulating tube is ceramic or quartz glass.

3. The heating tube having an insulating coating according to claim 1, wherein, The mass percentage of the low-temperature glass powder in the step (1) is 94-96%, and the mass percentage of the alumina powder is 4-6%.

4. The heating tube having an insulating coating according to claim 1, wherein, The particle size of the ball-milled mixture in the step (2) is less than 50 microns.

5. The heating tube having an insulating coating according to claim 1, wherein The volume percentage of the ball-milled mixture, acidic aluminum phosphate and water glass in the step (3) is 90%, 2% and 8% respectively.

6. The heating tube having an insulating coating according to claim 1, wherein, The fineness of the screen plate in the step (4) is 180-250 meshes.

7. The heating tube having an insulating coating according to claim 1, wherein The thickness of the insulating slurry layer in the step (4) is 25-35 microns.

8. The heating tube having an insulating coating according to claim 1, wherein, The time of the preheating, medium-temperature sintering and cooling in the step (5) is 3 minutes, and the time of the high-temperature sintering is 6 minutes.

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