A standard heat flow sensor for radiometric heat flow measurement

Abstract

This invention discloses a standard heat flux sensor for measuring radiative heat flux, belonging to the field of radiative heat flux measurement technology. It comprises a housing, a heat sink, a first absorption cavity, a first thermopile, and an aperture. The aperture is fixedly installed on one side of the opening of the housing and has an aperture hole. The heat sink is fixedly installed inside the housing and has a water-cooling channel for cooling. The first absorption cavity is an open conical shell structure, with its opening coaxially fitted into the inner cavity of one end of the heat sink along the direction towards the aperture hole. An electrically heated wire, capable of being electrically connected to a power source, is embedded between the inner and outer walls of the first absorption cavity. The hot end of the first thermopile abuts against the open end of the first absorption cavity, and the cold end abuts against the heat sink. The aperture hole transmits radiative heat flux, the inner wall of the first absorption cavity absorbs the heat from the radiative heat flux, and the first thermopile outputs a thermoelectric potential corresponding to the temperature difference. This standard heat flux sensor can accurately calibrate working radiative heat flux sensors.

Description

Technical Field

[0001] This invention belongs to the field of radiative heat flux measurement technology, and specifically relates to a standard heat flux sensor for radiative heat flux measurement. Background Technology

[0002] Radiation heat flux measurement is widely used in the development of my country's spacecraft. For example, in the development of models, such as flight telemetry and ground rocket engine testing, a large number of radiation heat flux sensors are used to measure the heat flux on the surface of the spacecraft and the heat flux of the engine exhaust flame, so as to provide data for model development.

[0003] To ensure the accuracy and reliability of heat flux sensor measurements, it is necessary to design a heat flux standard device for the calibration and traceability of radiative heat flux sensors, so as to calibrate and standardize the radiative heat flux sensors used in operation.

[0004] Traditionally, foil-type heat flux sensors are used as standard heat flux sensors to calibrate working radiative heat flux sensors. However, as the measurement time increases, the heat sink temperature of the foil-type heat flux sensor rises, making it unable to maintain a stable reference temperature, which affects the measurement results. Therefore, foil-type heat flux sensors can only achieve short-term radiative heat flux measurements. In addition, since the foil-type heat flux sensor has a surface heat flux absorption structure, its absorptivity is generally around 0.9, which cannot accurately measure radiative heat flux data. Summary of the Invention

[0005] In view of this, the present invention proposes a standard heat flux sensor for measuring radiative heat flux, which improves the absorption rate of radiative heat flux through a conical absorption cavity and maintains a stable reference temperature of the heat sink by setting a water-cooling channel, thereby enabling accurate standard calibration of the working radiative heat flux sensor.

[0006] The present invention adopts the following technical solution: A standard heat flux sensor for measuring radiative heat flux includes a housing, a heat sink, a first absorption cavity, a first thermopile, and an aperture. The aperture is fixedly installed on one side of the opening of the housing, and the aperture is provided with an aperture hole; The heat sink is fixedly installed inside the outer casing, and the heat sink is provided with a water-cooling channel for cooling. The first absorption cavity is an open conical shell structure, with its opening coaxially sleeved in the inner cavity of one end of the heat sink along the direction towards the aperture hole, and an electric heating wire that can be electrically connected to a power source is embedded between the inner wall surface and the outer wall surface of the first absorption cavity. The hot end of the first thermopile abuts against the open end of the first absorption cavity, and the cold end abuts against the heat sink; The aperture is used to transmit radiant heat flow. The inner wall of the first absorption cavity absorbs the heat of the radiant heat flow, generating a temperature difference between the hot and cold ends of the first thermopile. The first thermopile outputs a thermoelectric potential corresponding to the temperature difference.

[0007] Furthermore, the first absorption cavity includes a base layer, a black coating layer, and a gold plating layer; The inner wall of the base layer is provided with a black coating layer to absorb radiant heat flow, and the outer wall is provided with a gold plating layer to reflect stray heat flow. The heating wire is embedded in the base layer.

[0008] Furthermore, the base layer is made of pure silver.

[0009] Furthermore, the aforementioned standard heat flux sensor also includes an insulation layer; The insulation layer is sandwiched between the base layer and the black coating layer or the base layer and the gold plating layer, and is used to prevent the first absorption cavity from radiating heat outward.

[0010] Furthermore, the insulation layer is an aluminized polyimide film.

[0011] Furthermore, a first annular flange is provided at the open end of the first absorption cavity; The first thermopile includes a first annular insulating frame and a first series thermocouple fixedly wound around the first annular insulating frame; The first annular insulating frame is sandwiched between the first annular flange and the end face of the heat sink near the aperture. The hot end of the first series thermocouple is sandwiched between the first annular insulating frame and the first annular flange, and the cold end of the first series thermocouple is sandwiched between the first annular insulating frame and the end face of the heat sink near the aperture.

[0012] Furthermore, the first annular insulating skeleton is made of nylon.

[0013] Furthermore, the aforementioned standard heat flux sensor also includes a second absorption cavity and a second thermopile; The structure of the second absorption cavity is the same as that of the first absorption cavity, and its opening is coaxially sleeved in the inner cavity of the other end of the heat sink in a direction away from the aperture. The hot end of the second thermopile abuts against the second heat sink, and the cold end abuts against the second absorption cavity, so that the first thermopile and the second thermopile are reversed; A thermoelectric potential is output between the hot end of the first thermopile and the cold end of the second thermopile to counteract the effect of the temperature drift of the heat sink on the thermoelectric potential.

[0014] Furthermore, the inner wall surface of the aperture is polished to increase the reflectivity of the inner wall surface of the aperture to radiated heat flow.

[0015] Furthermore, the outer surface of the aperture is polished to increase the reflectivity of the outer surface of the aperture to radiant heat flow.

[0016] Beneficial effects: (1) The heat sink is equipped with a water-cooling channel for cooling. The first absorption cavity is an open conical shell structure. Its opening is coaxially sleeved in the inner cavity of one end of the heat sink along the direction towards the aperture. An electric heating wire that can be electrically connected to the power supply is embedded between the inner wall and the outer wall of the first absorption cavity. The hot end of the first thermopile abuts against the first absorption cavity, and the cold end abuts against the first heat sink. In this way, the radiant heat flow is absorbed by the inner wall of the first absorption cavity through the aperture, which will generate a temperature difference between the hot end and the cold end of the first thermopile. Then the first thermopile outputs a thermoelectric potential corresponding to the temperature difference. According to the thermoelectric equivalence principle, heat can be generated by the electric heating wire to make the first thermopile output an equal thermoelectric potential, thereby obtaining the magnitude of the radiant heat flow and completing the calibration of the working radiant heat flow sensor. The structure is simple and compact and easy to use.

[0017] Furthermore, the conical shell structure of the first absorption cavity can improve the absorption rate of radiative heat flow, and the cooling water flowing into the water-cooled channel can keep the heat sink at a constant reference temperature, thereby improving the accuracy of the standard heat flow sensor in measuring radiative heat flow.

[0018] (2) A black coating layer is provided on the inner wall of the base layer of the first absorption cavity, which can improve the absorption rate of radiative heat flow. A gold plating layer is provided on the outer wall, which can reflect stray heat flow and make the measurement accuracy of radiative heat flow higher.

[0019] (3) The base layer is made of pure silver, which has excellent thermal conductivity. It can make the heat generated by the electric heating wire quickly and evenly distributed on the first absorption cavity, improve the measurement accuracy of the heat generated by electric heating, and thus ensure that the radiation heat flow can be accurately obtained through the thermoelectric equivalence principle.

[0020] (4) The insulation layer is sandwiched between the base layer and the black coating layer or the base layer and the gold plating layer, which can prevent the first absorption cavity from radiating heat outward and improve the accuracy of the radiative heat flow measurement.

[0021] (5) The structure of the second absorption cavity is the same as that of the first absorption cavity and is symmetrically arranged with the first absorption cavity. The first thermopile and the second thermopile are reversed. When the heat sink has temperature drift, the output change of the first thermopile and the output change of the second thermopile cancel each other out, thus avoiding the influence of heat sink temperature drift on the radiative heat flow measurement results and improving the accuracy of radiative heat flow measurement.

[0022] (6) Polishing the inner wall of the aperture can increase the reflectivity of the inner wall of the aperture to radiative heat flow and improve the accuracy of radiative heat flow measurement.

[0023] (7) The outer surface of the aperture is polished, which can increase the reflectivity of the outer surface of the aperture to the radiative heat flow, reduce the heat absorption of the outer surface of the standard radiative heat flow sensor during use, and reduce the pressure of the water cooling system supplying cooling water to the water cooling channel. Attached Figure Description

[0024] Figure 1 A schematic diagram of the assembly structure of a standard heat flux sensor for measuring radiative heat flux provided in an embodiment of the present invention; Figure 2 for Figure 1 Schematic diagram of the structure of the first absorption cavity; Among them, 1-first thermopile, 2-aperture, 3-aperture hole, 4-first absorption cavity, 5-outer shell, 6-second thermopile, 7-second absorption cavity, 8-heat sink, 9-water cooling pipeline, 10-water cooling channel, 11-base layer, 12-black coating layer, 13-electric heating wire, 14-reflective layer. Detailed Implementation

[0025] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 As shown, a standard heat flux sensor for measuring radiative heat flux comprises a heat sink 8, a housing 5, a first absorption cavity 4, a first thermopile 1, and an aperture 2, wherein: The aperture 2 is fixedly installed on one side of the opening of the outer shell 5 (the aperture 2 and the outer shell 5 are made of the same material in the figure), and the aperture 2 is provided with an aperture hole 3; the heat sink 8 is fixedly installed inside the outer shell 5, and the heat sink 8 is provided with a water cooling channel 10 connected to the water cooling pipe 9, which can cool the heat sink 8 and keep its reference temperature constant; the first absorption cavity 4 is an open conical shell structure, and its opening is coaxially sleeved in the inner cavity of one end of the heat sink 8 along the direction towards the aperture hole 3, and an electric heating wire 13 that can be electrically connected to the power supply is embedded between the inner wall surface and the outer wall surface of the first absorption cavity 4; the hot end of the first thermopile 1 abuts against the open end of the first absorption cavity 4, and the cold end abuts against the heat sink 8.

[0027] Aperture 2 is used to transmit radiant heat flow. The inner wall of the first absorption cavity 4 absorbs the heat from the radiant heat flow, causing the temperature of the first absorption cavity 4 to rise, thereby generating a temperature difference between the hot and cold ends of the first thermopile 1. The first thermopile 1 outputs a thermoelectric potential corresponding to the temperature difference. The radiant heat flow absorbed by the first absorption cavity 4 q With thermoelectric potential The following functional relationship exists between them: q =K·

[0028] The radiant heat flow is cut off, and the electric heating wire 13 is heated by the power supply, so that the first thermopile 1 outputs an equal potential. According to the thermoelectric equivalence principle, the heat Q generated by the electric heating wire 13 is related to the radiant heat flow. q The values ​​are equal, and the heat Q generated by the electric heating wire 13 is known, and the thermoelectric potential is... Since it is also known, the coefficient K in the above function can be solved, and thus the working radiative heat flux sensor can be calibrated.

[0029] like Figure 2 As shown, the first absorption cavity 4 includes a pure silver base layer 11, a black coating layer 12, and a gold-plated reflective layer 14. The inner wall of the base layer 11 is provided with a black coating layer 12 for absorbing radiant heat flow, and the outer wall is provided with a gold-plated reflective layer 14 for reflecting stray heat flow. The electric heating wire 13 is embedded in the base layer 11.

[0030] Specifically, the manufacturing process of the first absorption cavity 4 employs an electroplating process. Specifically, a constantan heating wire 13 is wound using a double-wire non-inductive method between the inner and outer walls of the first absorption cavity 4, and then wrapped with insulating varnish. Finally, electroplating is performed, embedding the heating portion of the heating wire 13 between the inner and outer walls of the first absorption cavity 4, making it an integral part of the cavity. Thus, the heat generated by the heating wire 13 is entirely applied to the first absorption cavity 4. When the electrical power heating causes the temperature difference signal generated by the sensor to equal the temperature difference signal generated by the radiant heat flow, the radiant heat flow power and the electrical power are equivalent, thereby achieving absolute measurement of the heat flow.

[0031] In addition, a heat insulation layer (not shown in the figure) can be provided between the base layer 11 and the black coating layer 12 or between the base layer 11 and the gold-plated reflective layer 14 to prevent the first absorption cavity 4 from radiating heat outward. In this embodiment, a 5μm thick aluminum-plated polyimide film is wrapped between the base layer 11 and the gold-plated reflective layer 14 as a heat insulation layer.

[0032] More specifically, the first thermopile 1 includes a first annular insulating frame made of nylon and multiple pairs of constantan-copper thermocouples connected in series and fixedly wound around the first annular insulating frame. The thermopile increases the sensitivity of radiative heat flux measurement compared to thermocouples. Furthermore, as... Figure 1As shown, the open end of the first absorption cavity 4 is provided with a first annular flange. A first annular insulating frame is sandwiched between the first annular flange and the end face of the heat sink 8 near the aperture 2. The hot end of the series thermocouple is sandwiched between the first annular insulating frame and the first annular flange, and the cold end of the series thermocouple is sandwiched between the first annular insulating frame and the end face of the heat sink 8 near the aperture 2. If the thermal resistance of the first annular insulating frame is too high, the excessively high temperature will damage the first thermopile 1. If the thermal resistance of the first annular insulating frame is too low, the temperature difference between the first absorption cavity 4 and the heat sink 8 will be small, which is not conducive to the accurate measurement of radiative heat flow. The nylon material selected in this embodiment has suitable thermal resistance, which can ensure that the first thermopile 1 will not be damaged by excessive temperature, and also ensure the measurement sensitivity of radiative heat flow.

[0033] As an improvement, such as Figure 1 As shown, a second absorption cavity 7 is also provided at the other end of the heat sink 8. The structure of the second absorption cavity 7 is the same as that of the first absorption cavity 4, and the opening of the second absorption cavity 7 is coaxially fitted into the inner cavity of the heat sink 8 in the direction away from the aperture 2 (the electric heating wire in the second absorption cavity does not need to be connected to an external power source; the electric heating wire is embedded in the second absorption cavity to make the structure of the second absorption cavity consistent with the structure of the first absorption cavity, so that the physical parameters of the first absorption cavity and the second absorption cavity, such as heat capacity, are consistent). Correspondingly, a second thermopile 6 with the same structure as the first thermopile 1 is provided, but the second... The hot end of thermopile 6 abuts against the second heat sink 8, and the cold end abuts against the second absorption cavity 7, effectively reversing the connection between the first thermopile 1 and the second thermopile 6. By designing the second absorption cavity 7 and the second thermopile 6 symmetrically to the first absorption cavity 4 and the first thermopile 1, if the heat sink 8 experiences temperature drift, the thermoelectric potentials generated by the first thermopile 1 and the second thermopile 6 will produce additional thermoelectric potentials of the same magnitude but opposite direction caused by the temperature drift. These additional thermoelectric potentials can cancel each other out, thus avoiding the influence of temperature drift of the heat sink 8 caused by changes in ambient temperature on the measurement results. In this embodiment, an output cable is led out from the hot end of the first thermopile 1 and the cold end of the second thermopile 6 to output the thermoelectric potential.

[0034] More specifically, in this embodiment, the aperture 2 is made of hard aluminum alloy, and the diameter of the aperture hole 3 is designed to be 2mm, with a machining accuracy of 0.01mm. Design analysis shows that the temperature difference between the aperture 2 and the heat sink 8 is generally maintained at around 1.5℃. The linear expansion coefficient of the aperture 2 is 22E-6. Therefore, the aperture diameter of the aperture hole 3 will not change significantly due to temperature variations, and its impact on the measurement results is negligible. Furthermore, the inner wall surface of the aperture hole 3 is polished to increase the reflection of radiant heat flow. Simultaneously, because the outer surface of the aperture 2, i.e., the outer surface of the standard radiant heat flow sensor head, is directly exposed to a large amount of radiant heat flow, to reduce surface heat absorption during use, reduce head temperature rise, and decrease water circulation system pressure, an aluminum plating and polishing process is used on the outer surface of the aperture 2. This controls the radiant heat absorption rate of the outer surface to be below 0.05, thereby reducing the heat absorption of the sensor head. Furthermore, to ensure that more of the radiative heat flow energy entering the inner surface of the aperture 2 is absorbed by the first absorption cavity 4, the inner surface of the aperture 2 is also treated with a high reflectivity surface. In this embodiment, the reflectivity of the inner surface of the aperture 2 is higher than 0.95.

[0035] Experiments have verified that this standard radiative heat flux sensor can achieve a range of 0.1~400 W / cm². 2 The heat flow measurement has an accuracy of 1% and can be used as a heat flow transfer standard for calibration testing of working radiative heat flow sensors. In the future, this radiative heat flow standard sensor can also be extended to civilian measurement fields, such as fire detection and industrial furnace body measurement.

[0036] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A standard heat flux sensor for measuring radiative heat flux, characterized in that, Includes an outer casing, a heat sink, a first absorption cavity, a first thermopile, and an aperture; The aperture is fixedly installed on one side of the opening of the housing, and the aperture is provided with an aperture hole; The heat sink is fixedly installed inside the outer casing, and the heat sink is provided with a water-cooling channel for cooling. The first absorption cavity is an open conical shell structure, with its opening coaxially fitted into the inner cavity of one end of the heat sink along the direction towards the aperture. An electric heating wire capable of being electrically connected to a power source is embedded between the inner and outer walls of the first absorption cavity. The first absorption cavity includes a base layer, a black coating layer, and a gold plating layer. The inner wall of the base layer is provided with a black coating layer for absorbing radiant heat flow, and the outer wall is provided with a gold plating layer for reflecting stray heat flow. The heating wire is embedded in the base layer. The hot end of the first thermopile abuts against the open end of the first absorption cavity, and the cold end abuts against the heat sink; the open end of the first absorption cavity is provided with a first annular flange; the first thermopile includes a first annular insulating frame and a first series thermocouple fixedly wound around the first annular insulating frame; the first annular insulating frame is sandwiched between the first annular flange and the end face of the heat sink near the aperture; the hot end of the first series thermocouple is sandwiched between the first annular insulating frame and the first annular flange, and the cold end of the first series thermocouple is sandwiched between the first annular insulating frame and the end face of the heat sink near the aperture. It also includes a second absorption cavity and a second thermopile; the structure of the second absorption cavity is the same as that of the first absorption cavity, and its opening is coaxially sleeved in the inner cavity of the other end of the heat sink along the direction away from the aperture; the hot end of the second thermopile abuts against the second heat sink, and the cold end abuts against the second absorption cavity, so that the first thermopile and the second thermopile are reversed; a thermoelectric potential is output from the hot end of the first thermopile and the cold end of the second thermopile to offset the influence of the temperature drift of the heat sink on the thermoelectric potential; an electric heating wire is embedded in the second absorption cavity, and the electric heating wire in the second absorption cavity does not need to be connected to an external power source; The aperture is used to transmit radiant heat flow. The inner wall of the first absorption cavity absorbs the heat of the radiant heat flow, generating a temperature difference between the hot and cold ends of the first thermopile. The first thermopile outputs a thermoelectric potential corresponding to the temperature difference.

2. A standard heat flux sensor for measuring radiative heat flux as described in claim 1, characterized in that, The base layer is made of pure silver.

3. A standard heat flux sensor for measuring radiative heat flux as described in claim 2, characterized in that, It also includes the insulation layer; The insulation layer is sandwiched between the base layer and the black coating layer or the base layer and the gold plating layer, and is used to prevent the first absorption cavity from radiating heat outward.

4. A standard heat flux sensor for measuring radiative heat flux as described in claim 3, characterized in that, The insulation layer is an aluminized polyimide film.

5. A standard heat flux sensor for measuring radiative heat flux as described in claim 1, characterized in that, The first annular insulating skeleton is made of nylon.

6. A standard heat flux sensor for measuring radiative heat flux as described in any one of claims 1-5, characterized in that, The inner wall surface of the aperture is polished to increase the reflectivity of the inner wall surface of the aperture to radiant heat flow.

7. A standard heat flux sensor for measuring radiative heat flux as described in any one of claims 1-5, characterized in that, The outer surface of the aperture is polished to increase the reflectivity of the aperture surface to radiant heat flow.

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