Flat tube heat collector of electric hot water boiler with thermistor heating element and manufacturing method of flat tube heat collector

Abstract

The invention provides a flat tube heat collector of an electric water boiler with a thermistor heating element and a manufacturing method of the flat tube heat collector, and belongs to the technical field of water supply equipment. The problems that a heating element unit of an existing heat exchanger is large in size, and operation of a heating element is not reliable enough are solved. This heat exchanger is provided with thermistor heating elements which are distributed at a high density over the entire surface of a flat tube channel element, have a maximum heating temperature limit determined by the thermophysical properties of thermistors, and do not allow the surface of a plate channel element of the heat exchanger to be heated to or above the boiling point of a heat carrier. The arrangement of a gasket in the flat tube channel element ensures the laminar movement of the heat carrier. The heat exchanger has the advantages of being energy-saving, compact, high in energy efficiency and long in service life, and the manufacturing method is simple in process.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchange equipment, and relates to a flat tube collector of an electric water boiler with a thermistor heating element, which can be used as a heat exchanger for water heating systems of personal, industrial and commercial facilities. At the same time, the present invention relates to the collector and its manufacturing method. Background Art

[0002] There is known a linear electric heater in the form of a heating element, including a linear heating resistor, an insulating filler and a tubular body. The heating element is placed in a container through which water passes. When water comes into contact with the tubular body of the heating element, it is heated (see the patent "Flow-through electric water heater", RU No. 965U1, IPC F24H 09 / 20, October 16, 1995).

[0003] The main disadvantages of this kind of electric heater are: the large size of the heating element block, the unreliable operation of the heating element, when scale appears on the wall of the heating element, the heating element will burn out, the power cannot be smoothly adjusted, when switching to high power when turning on and off the heating element, the network will be interfered, due to the high surface temperature of this type of heating element, equivalent to 300 - 350 degrees Celsius, surface boiling will occur in the area where water is in contact, resulting in the decomposition of water into steam and gas, and then removed from the heating circuit. In order to compensate for the volume of the heat carrier in the heating circuit, it is necessary to organize the replenishment of the required volume of water. (See Tolopov A.L., "Autonomous low-power heating systems. Wall-mounted gas boilers and heat accumulators" study guide, MISI-MGSU Publishing House, 09.26.2022).

[0004] When using antifreeze as a heat carrier in the heating system, in the area where the antifreeze comes into contact with the surface of the heating element, boiling of the antifreeze will also occur, and then the antifreeze will decompose into acids and solid deposits, damaging the heating system. (See the article by Tolopov A.L., "Features of using antifreeze and autonomous heating systems of wall-mounted gas boilers", SOK. 2022. No. 1. pp. 48 - 50).

[0005] The heating of the heat carrier in the heat energy generator in the heating system should not exceed its boiling point. When boiling, the hardness salts contained in the water are deposited on the surface of the heating element, which will lead to a significant reduction in the efficiency of heating water and any other heat carrier. The insulating filler between the heating resistor and the heating element housing has a high thermal resistance, which will lead to a reduction in the energy efficiency of the heating system during operation and excessive energy consumption. Due to the possibility of short circuit between the heating resistor and the heating element housing and its limited service life, the reliability of these devices is low.

[0006] Known is a capacitive (thermistor) carburetor heater, which contains a disk-shaped heating wire with a thermistor fixed to its end, and the thermistor has good thermoelectric contact (see the patent "Capacitor Heater for Internal Combustion Engine Carburetor", RU No. 20254, IPC F02M 31 / 12, September 30, 1994). The positive electrode is a resistor in the form of a monomer made of semiconductor ceramic, which has an extremely large positive TCR - thermal resistance coefficient in a very narrow temperature region (the reversible phase change region of the positive electrode material), where the resistance increases by 3 - 4 orders of magnitude. Therefore, when switched on, a large amount of current flows, quickly heating the positive electrode. At the phase change temperature, the resistance increases sharply and the current drops sharply to a value that only compensates for the dissipated heat, so the positive electrode does not overheat, that is, the thermistor can maintain the temperature independently without an automatic temperature maintenance system. The thermistor heater does not have the disadvantages of a heating element.

[0007] The disadvantage of this kind of heater is that the temperature rise is not fast enough. Heat is dissipated from the outer edge of the thermistor and the surface of the heat pipe. Due to the heat loss outside the structure, there is excessive consumption of electrical energy. A thermistor heater for parts of a pipeline system and liquid and gas tanks is known (see the patent, RU No. 22154232, C1, IPC F17D 1 / 18, published on August 10, 2000).

[0008] A thermistor heater for pipeline system components and containers for liquids and gases includes at least one thermistor and means for connecting it to a power circuit, including a contact plate above the thermistor, provided with a housing with a cover, such that its heating surface can be heated with the thermistor and it can be mounted on the heated component of the system. The thermistor and the means for connecting it to the power circuit are placed in the housing. The means is provided with an electrical insulator, preferably a thermal insulator, above the thermistor contact plate, and preferably located between the housing cover and the insulator. Additionally, there is provided a sub-thermistor device for connecting to the power circuit, and a sub-thermistor contact plate with terminals is inserted into this device.

[0009] The disadvantages of this design are: Since the heating systems of buildings and commercial items require a large amount of thermal power, heating elements must be connected in series on the pipeline. The power of a single thermistor is relatively small, so it requires a very large size, which affects the final cost of the heat generator. In addition, the heat energy dissipation outside the pipeline body is very large, which affects the energy efficiency of heat generation.

[0010] A plate heat exchanger of an electric water heater with a flat thermistor heating element was selected as a prototype (see patent, RU No. 2812563, C1, IPC F28D 9 / 00, F28D 3 / 00, F28F 3 / 08, H05B 3 / 20, published on January 30, 2024). A heat exchanger of a water heater with a thermistor heating element generating heat includes heat carrier inlet and outlet pipes, inlet and outlet channels formed by parallel connection of seal members and plate channel elements of any shape with a thickness of 0.5 - 10 mm. The heat carrier moves from the inlet channel to the outlet channel through this channel. A thermistor heating element is arranged between the plate channel elements. The thermistor heating element is pressed on the plate channel elements by using threads with the upper and lower support plates to ensure the tightness of the heat exchanger. The specified pressing force of the thermistor heating element on the plate channel elements is achieved through a threaded connection with an adjusted fine thread pitch.

[0011] The disadvantages of this design are as follows: The heat carrier moves rapidly along the plate channel elements with a thickness of 0.5 - 10 mm, and the shape of the channel is arbitrary, so the heat energy transfer from the heating element to the heat carrier is restricted. As the required power of the heat exchanger increases, it is necessary to increase the size of the plate channel elements and the size of the entire heat exchanger. As the size and number of the plate channel elements increase, it becomes difficult to ensure the tightness of the connection between them. Inside the plate elements, when the heat carrier moves therein, eddy stagnation zones are generated, affecting (reducing) the energy efficiency index of heat exchange. Summary of the Invention

[0012] The object of the present invention is to provide a flat tube collector of an electric water boiler with a thermistor heating element in view of the above problems.

[0013] To achieve the above object, the present invention adopts the following technical solutions:

[0014] A flat tube collector of an electric water boiler with a thermistor heating element, the heat exchanger is made based on a collector circuit, including flat tube channel elements made of flat elliptical or rectangular thin-walled pipes with high thermal conductivity. The wall thickness of the pipes is 0.2 - 3.0 mm. Adjacent flat tube channel elements are arranged parallel to each other. The ends of the flat tube channel elements have openings and seal members. The openings and seal members cooperate to form a channel for the heat carrier to flow in and out and a channel for the thermistor heating element located between adjacent flat tube channel elements to heat the heat carrier. The flat tube channel elements and the thermistor heating element are tightly fixed by connectors arranged along the periphery of the heat exchanger passing through the side plates.

[0015] In the flat tube collector of an electric water heating boiler with a thermistor heating element as described above, a separator is provided inside the flat tube of the flat tube channel element. The separator is placed along the length of the flat tube to divide the cross-section of the flat tube into narrow channels, such that the movement of the heat carrier within the flat tube is laminar.

[0016] In the flat tube collector of an electric water heating boiler with a thermistor heating element as described above, support inserts are installed within the openings of the flat tubes of the flat tube channel element and are located at both ends of the flat tubes, ensuring the structural rigidity of the inflow and outflow channels of the heat carrier required during the assembly of the heat exchanger and ensuring its sealing performance.

[0017] Compared with the existing technology, the advantages of the present invention are as follows:

[0018] 1. It has the advantage of fire safety because the overheating of system components beyond the heating temperature of the thermistor heating element is excluded. For the heating system, the heating temperature of the thermistor heating element does not exceed 80 degrees Celsius. Additionally, the scaling and decomposition of the non-freezing heat carrier associated with the boiling process of the heat carrier are significantly reduced.

[0019] 2. It has the advantage of a compact structure. Due to the use of a thermistor heating element with a thickness of 2 - 3.5 mm, the heat flux density per unit volume of the heat exchanger is higher than that of circular cross-section tubes, making the device more compact.

[0020] 3. The reliability and service life of the thermistor heating element are significantly higher than those of traditional tubular heating elements.

[0021] 4. It has the advantage of high energy efficiency. Due to the installation of the separator, when the heat carrier moves through the channel, the contact area between the heating element and the heat carrier increases, resulting in an increase in the energy efficiency of the heat exchanger.

[0022] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a flat tube channel element with support inserts (top view sectional structure).

[0024] Figure 2 Shown is a flat tube channel element with support inserts (side view sectional structure).

[0025] Figure 3 Shown is a flat tube collector of an electric water heating boiler with a thermistor heating element (side view sectional structure).

[0026] Figure 4Shown is a flat tube collector (top view sectional structure) of an electric water boiler with a thermistor heating element.

[0027] In the figure, 1 is a flat tube; 2 is an opening; 3 is a support insert; 4 is a separator; 5 is a channel tube; 6 is a seal; 7 is a flat tube channel element; 8 is a side plate; 9 is a connecting piece; 10 is a thermistor heating element. Specific embodiments

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] As Figures 1-4 Shown, the flat tube channel element 7 includes a flat tube 1 with an opening 2, and a support insert 3 is inserted into the end of the flat tube 1 for support and sealing of the end of the flat tube 1. Inside the flat tube 1, a separator 4 of any shape is inserted along the length direction of the flat tube 1. The seal 6 for connecting the flat tube channel element 7 is an annular gasket of any shape, the thickness of which is equal to the thickness of the thermistor heating element 10, and is made of one material to ensure the sealing of the connection.

[0030] The flat tube heat exchanger with a thermistor heating element 10 includes a channel tube 5 for the heat carrier, a side plate 8, a flat tube channel element 7, a connecting piece 9, a thermistor heating element 10, and a seal 6.

[0031] The design of the flat tube collector type heat exchanger with a thermistor heating element 10 includes a plurality of flat tube channel elements 7 for the movement of the heat carrier. The plurality of flat tube channel elements 7 are connected in parallel, and seals 6 are placed between these flat tube channel elements 7 to form input and output channels for the movement of the heat carrier. The thermistor heating element 10 is arranged on the surface of the flat tube channel element 7 in a high-density manner. When it is necessary to increase the capacity of the heat exchanger, it is necessary to increase the width of the flat tube channel element 7 and increase the number of thermistor heating elements 10 thereon.

[0032] The flat tube channel element 7 for the movement of the heat carrier and the thermistor heating element 10 are fixedly pressed through an adjustable connecting piece 9, and a fine-pitch adjustable connecting piece 9 is used for metering adjustment to ensure a tight connection. The heat carrier enters the heat exchanger through the channel tube 5 on one side, and the heat carrier leaves the heat exchanger through the channel tube 5 on the flat tube channel element 7 on the other side.

[0033] Working principle of the heat exchanger: Multiple flat tube channel elements 7 are connected by seals 6 to form a common input channel, an output channel, and a channel for the heat carrier to pass through with the openings 2. The cold heat carrier enters the heat exchanger through the channel tube 5 under excess pressure, flows in along the 2 direction of the flat tube channel element 7, passes from the common input channel through the heating channel to the common output channel, and the heat carrier passes through a series of flat tube channel elements 7 in sequence. The movement of the heat carrier in the heat exchanger is indicated by the arrow ( Figure 3 ). Support inserts 3 and partition elements 4 are placed inside the flat tube channel element 7. The arrangement of the support inserts 3 ensures the rigidity of the shape of the flat tube channel element 7 in the area of the seal 6, and the arrangement of the partition elements 4 ensures the laminar flow of the heat carrier along the flat tube channel element 7. Between the flat tube channel elements 7, the thermistor heating elements 10 are arranged at a high density and are pressed against the surface of the flat tube channel element 7 by the side plates 8. The high-density arrangement of the thermistor heating elements 10 on the entire surface of the flat tube channel element 7 provides a large heating area, and the heated heat carrier enters the system through the channel tube 5.

[0034] When the heat carrier moves from the inlet to the outlet, when the width of the flat tube channel element 7 is large, there will be a stagnant area in the form of local vortices inside the flat tube channel element 7. Heating the heat carrier in the stagnant area will cause it to overheat, and then the thermistor heating element 10 located in its environment will disconnect. To ensure that the movement of the heat carrier along the flat tube channel element 7 is close to laminar flow, the width of the flat tube channel element 7 should not exceed the width of the inlet part of the channel tube 5 and the width of the inlet part of the channel tube 5. At the same time, to ensure the tightness of the periphery of the flat tube channel element 7 and the joints with adjacent manufactured flat tube channel elements 7 during the manufacture of the flat tube channel element 7, a complex process of stamping and welding using a sheet material with high thermal conductivity is required.

[0035] Method for manufacturing a flat tube collector of an electric water boiler with a thermistor heating element: To reduce the cost of manufacturing the flat tube channel element 7, the flat tube 1 is preferably made of a thin-walled round tube of a highly thermally conductive material and then compressed into a flat oval or rectangular shape according to the cross-sectional geometry, with its profile dimensions being 3 - 10 mm in height and 15 - 50 mm in width, and the wall thickness of the tube should be 0.2 - 3.0 mm. Drill holes (side holes) 2 at the ends of the flat tube channel element 7, insert support inserts 3 made of a durable material into the ends of the tube, and seal the ends of the flat tube in the area of the side holes. Before installing the support inserts 3, insert any-profile separators 4 made of a highly thermally conductive material into the flat tube channel element 7. The separator 4 is used to prevent the compression of the flow segments of the tube and ensure the laminar movement of the heat carrier along the length of the flat tube channel element 7. Due to the installation of the separator 4, the energy efficiency of the heat exchanger is improved because the contact area between the heating element and the heat carrier increases as the heat carrier passes through the channel. In this way, the flat tube channel element 7 is produced, and then the thermistor heating elements 10 are arranged on the entire surface of the flat tube channel element 7 at a high density, and a plurality of flat tube channel elements 7 are connected through seals 6 to form a common input channel and output channel and a channel for the heat carrier to pass through. Finally, the flat tube channel element 7 and the thermistor heating element 10 are clamped and fixed through an adjustable connector 9.

[0036] When using water as the heat carrier, the thermistor heating element 10 heats the heat carrier to a temperature not higher than 80 degrees Celsius, which eliminates the possibility of water boiling and the formation of scale on the inner surface of the flat channel element by the heat carrier. The surface temperature of the thermistor heating element 10 cannot be higher than the specified temperature, which is determined by the physical properties of the thermistor used. The entire temperature control process of the heat exchanger is based on the collector circuit.

[0037] Technical effects of the present invention: By arranging thermistor heating elements 10 on the entire surface of the flat tube channel element 7 at a high density, a compact plate heat exchanger is formed, which has a maximum heating temperature limit determined by the thermophysical properties of the thermistor and prevents the heating of the surface of the flat tube channel element 7 of the electrothermal exchanger from exceeding the boiling temperature of the heat carrier and forming a stagnant zone for the movement of the heat carrier in the flat tube channel element 7. The present invention has the following advantages: 1. It has the advantage of fire safety because the overheating of system components beyond the thermistor heating temperature is excluded. For the heating system, the thermistor heating temperature does not exceed 80 degrees Celsius. In addition, the scaling and decomposition of the non-freezing heat carrier associated with the boiling process of the heat carrier are significantly reduced; 2. It has the advantage of a compact structure. Due to the use of thermistor heating elements 10 with a thickness of 2 - 3.5 mm, the heat flux density per unit volume of the heat exchanger is higher than that of circular-section tubes, making the device more compact; 3. The reliability and service life of the thermistor heating elements 10 are significantly higher than those of traditional tubular heating elements; 4. It has the advantage of high energy efficiency. Due to the installation of the partition 4, when the heat carrier moves through the channel, the contact area between the heating element and the heat carrier increases, resulting in an increase in the energy efficiency of the heat exchanger.

[0038] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains may make various modifications or supplements to the described specific embodiments or use similar ways of substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0039] Since the claimed invention differs from the closest analogues in many essential features, it meets the patentability condition of "novelty".

[0040] Since the claimed invention is based on known laws of the physical world, this allows us to assert that the present invention meets the patentability condition of "utility".

[0041] Since the design of the flat tubular collector heat exchanger is not known from the prior art, it can be concluded that the device meets the patentability condition of "level of inventiveness".

[0042] Although this document uses more terms, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A flat tube collector of an electric hot water boiler with a thermistor heating element, characterized in that, The heat exchanger is made based on a collector circuit and includes a flat tube channel element (7) made of a flat oval or rectangular thin-walled tube with high thermal conductivity. The wall thickness of the tube is 0.2 - 3.0 mm. Adjacent flat tube channel elements (7) are arranged parallel to each other. The ends of the flat tube channel element (7) have openings (2) and seals (6). The openings (2) and seals (6) cooperate to form a channel for the inflow and outflow of the heat carrier and a channel for the thermistor heating element located between adjacent flat tube channel elements (7) to heat the heat carrier. The flat tube channel element (7) and the thermistor heating element (10) are fixedly clamped through a connecting member (9) arranged along the periphery of the heat exchanger and passing through a side plate (8).

2. The flat tube collector of the electric water boiler with a thermistor heating element according to claim 1, characterized in that, A partition member (4) is arranged in the flat tube of the flat tube channel element (7). The partition member (4) is placed along the length of the flat tube to divide the cross-section of the flat tube (1) into narrow channels, so that the movement of the heat carrier in the flat tube (1) is laminar flow.

3. The flat tube collector of the electric water heating boiler with a thermistor heating element according to claim 1, characterized in that, The support insert (3) is installed in the opening (2) of the flat tube of the flat tube channel element (7) and is located at both ends of the flat tube, ensuring the structural rigidity of the inflow channel and outflow channel of the heat carrier required during the assembly of the heat exchanger and ensuring its sealing performance.

Images