Steady-state radiation heat flow meter with compensating plate and calibration method

Abstract

The invention relates to the technical field of heat flow measurement, and discloses a steady-state radiation heat flow meter with a compensating plate and a calibration method in order to improve the measurement precision of a radiation heat flow meter, the compensating plate is attached to the back of a thermosensitive plate, and the added compensating plate can reduce the heat loss generated by the radiation heat flow meter when the temperature difference is increased. Meanwhile, constant radiation heat flow is generated by controlling the temperature of the blackbody furnace, the radiation heat flow density is calculated according to the temperature of the thermosensitive piece and compared with the constant radiation heat flow generated by the blackbody furnace, the calibration coefficient is obtained, the calibration implementation process is simple, and the measurement precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat flux measurement, and specifically relates to a steady-state radiation heat flux meter for measuring radiation heat flux density in a vacuum environment. Background Art

[0002] A radiation heat flux meter is an instrument used to measure radiation heat flux and is applied in multiple fields such as the energy industry, aerospace, materials science and engineering, environment and meteorology. Among them, it is widely used in aerospace thermal experiments. The core value of the radiation heat flux meter lies in its ability to accurately quantify radiation heat transfer. An accurate and reliable heat flux meter is required to measure radiation heat flux in thermal experiments. Radiation heat flux meters are mainly divided into steady-state and transient types. For existing steady-state radiation heat flux meters, when the temperature difference between the ambient temperature and the temperature of the radiation heat flux meter increases, the heat loss (radiative heat leakage and heat conduction heat leakage) of the radiation heat flux meter increases, and the measurement result of its heat flux density has an error, resulting in a decrease in the measurement accuracy of the radiation heat flux meter.

[0003] Currently, in the calibration principle of heat flux meters, blackbody radiation calibration is widely used. By heating the inside of the blackbody furnace to a high temperature to provide an ideal temperature field, irradiating the heat flux meter placed therein, and accurately calculating this radiation heat flux according to the ideal blackbody radiation heat transfer theory, the heat flux meter can be calibrated. However, the process of precisely controlling the temperature of the blackbody furnace is cumbersome, the implementation process is complex, and the temperature of the blackbody cavity is uneven during temperature control, thus affecting the calibration accuracy. Summary of the Invention

[0004] In order to avoid the deficiencies of the above-mentioned prior art, the present invention provides a steady-state radiation heat flux meter with a compensating sheet and a calibration method to improve the measurement accuracy of the radiation heat flux meter. The technical solutions adopted to solve the above technical problems are as follows:

[0005] On the one hand, the present invention provides a steady-state radiation heat flux meter with a compensating sheet. As Figure 1 shown, a compensating sheet is arranged on one side of the heat-sensitive sheet inside the main body.

[0006] A multi-layer heat insulation part is arranged between the heat-sensitive sheet and the compensating sheet to reduce the heat loss between the heat-sensitive sheet and the compensating sheet.

[0007] A multi-layer heat insulation part is arranged between the compensating sheet and the inner wall of the main body to reduce the heat loss from the compensating sheet to the installation surface of the radiation heat flux meter.

[0008] The surfaces of the heat-sensitive sheet and the compensating sheet are uniformly coated with a black heat-absorbing coating of the same material.

[0009] A first temperature sensor is attached to the bottom of the heat-sensitive sheet. During use, the side of the heat-sensitive sheet with the heat-absorbing coating faces the inside of the blackbody furnace cavity.

[0010] On the other hand, a calibration method for a steady-state radiation heat flux meter with a compensating piece is provided, including the following steps:

[0011] S1. As shown in Figure 2 , attach a second temperature sensor, a third temperature sensor, a fourth temperature sensor, and a fifth temperature sensor to the furnace cover at the mouth end of the blackbody furnace cavity, the front end, the middle end, and the rear end of the outer cylinder wall respectively, and set heating components around the outer cylinder wall and at one end opposite to the cavity mouth; place the radiation heat flux meter to be calibrated at the inner cavity mouth of the blackbody furnace under a vacuum environment, with the heat-sensitive piece facing the inside of the blackbody furnace cavity;

[0012] S2. Control the heating components to change the temperature of the blackbody furnace, generate different fixed radiation heat fluxes, and calculate the magnitude q of the radiation heat flux density at the cavity mouth b :

[0013]

[0014] where q b is the radiation heat flux density at the cavity mouth, ε b is the effective emissivity of the ideal blackbody furnace cavity mouth, T b is the temperature of the blackbody furnace, σ is the Stefan-Boltzmann constant equal to 5.67×10 -8 W / (m 2 ·K 4 ), T2 is the temperature detection value of the second temperature sensor, T3 is the temperature detection value of the third temperature sensor, T4 is the temperature detection value of the fourth temperature sensor, and T5 is the temperature detection value of the fifth temperature sensor;

[0015]

[0016] where A1 is the inner surface area of the cavity, A2 is the surface area of the cavity mouth, and ε is the surface emissivity of the inner cavity coating;

[0017] S3. Calculate the calibration coefficient of the radiation heat flux meter by obtaining the temperature detection value of the first temperature sensor and the ambient temperature. The specific formula is as follows:

[0018]

[0019] where C is the calibration coefficient of the radiation heat flux meter, T1 is the temperature detection value of the first temperature sensor, T0 is the ambient temperature, σ is the Stefan-Boltzmann constant equal to 5.67×10 -8 W / (m 2 ·K 4 ), substitute the radiation heat flux density q b in S2 into the above formula to obtain the calibration coefficient at different temperature differences between the heat flux meter and the ambient temperature.

[0020] Technical effects:

[0021] 1. On the basis of the original thermal sensitive chip, the present invention adds a compensation chip. During the measurement process, on the one hand, the radiant heat flux received by the compensation chip is the same as that of the thermal sensitive chip, reducing the heat loss on the back of the thermal sensitive chip. On the other hand, multiple layers of heat insulation parts are pasted between the thermal sensitive chip and the compensation chip, and the compensation chip compensates for the heat loss of the thermal sensitive chip, further reducing the radiant heat leakage of the thermal sensitive chip. At the same time, multiple layers of heat insulation parts are pasted behind the compensation chip, reducing the heat loss between the compensation chip and the installation surface of the heat flux meter.

[0022] 2. Under a constant ambient temperature, the present invention controls the temperature of the blackbody furnace through a heating component to generate different fixed heat fluxes. The implementation process of this temperature control method is simple, improving the calibration efficiency and facilitating engineering applications. Taking the average value of the temperature detection values of the second, third, fourth, and fifth temperature sensors as the temperature of the blackbody furnace reduces the influence of the non-uniformity of the blackbody furnace temperature on the magnitude of the radiant heat flux density at the cavity opening. Formula ③ calculates the effective emissivity of the cavity opening based on the surface emissivity of the coating inside the blackbody furnace, the internal surface area of the cavity, and the surface area of the cavity opening, and substituting it into Formula ① can also reduce the influence of the uncertainty of the surface emissivity of the coating inside the blackbody furnace on the magnitude of the radiant heat flux density at the cavity opening. When calibrating, the heat conduction heat leakage is ignored, simplifying the calibration formula. The calibration coefficient is calibrated through the calibration formula ④ of the radiant heat flux meter, obtaining the calibration coefficient of the radiant heat flux meter at different temperature differences between the heat flux meter temperature and the ambient temperature. The radiant heat flux density is corrected by the calibration coefficient corresponding to different temperature differences, reducing the measurement result error, thereby improving the measurement accuracy of the radiant heat flux meter. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the internal component structure of the steady-state radiant heat flux meter of the present invention.

[0024] Figure 2 It is a schematic diagram of the blackbody furnace calibration of the present invention.

[0025] Figure 3 It is a curve showing the change of the calibration coefficient of the radiant heat flux meter of the embodiment of the present invention with the difference between the heat flux meter temperature and the ambient temperature.

[0026] Wherein: 1. Thermal sensitive chip, 2. Compensation chip, 3. Multiple layers of heat insulation parts, 4. Blackbody furnace, 5. Radiant heat flux meter, 6. First temperature sensor, 7. Second temperature sensor, 8. Third temperature sensor, 9. Fourth temperature sensor, 10. Fifth temperature sensor, 11. Heating component. Detailed Embodiment

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts using the embodiments of the present invention belong to the scope of protection of the present invention.

[0028] In this embodiment, the heat-sensitive sheet 1 and the compensating sheet 2 are made of metal sheets with good thermal conductivity, such as copper sheets. Its temperature range can be very wide, such as -60°C to 120°C.

[0029] Furthermore, the multi-layer heat insulation part 3 is formed by cross-laminating a reflective screen and a spacer layer. The reflective screen is characterized by low emissivity and high absorptivity, and is used to reduce radiative heat leakage. The spacer layer material is characterized by a small thermal conductivity coefficient and a small contact area with the reflective screen, and is used to reduce conductive heat leakage. In this embodiment, the low emissivity of the reflective screen means less than or equal to 0.2, and the high absorptivity means greater than or equal to 0.8. For example, a double-sided aluminized polyimide film, and the thickness of the reflective screen is 6 - 12μm. The spacer layer is preferably a polyester mesh, the thickness of the mesh spacer layer is 75 - 200μm, and the mesh size is 2 - 6mm. The number of layers of the multi-layer heat insulation part is 5 - 15 layers.

[0030] The calibration method of the radiant heat flux meter 5 adopts the method of blackbody furnace radiation calibration. In the embodiment, the blackbody furnace 4 is made of a metal with a high thermal conductivity coefficient to obtain better temperature uniformity. The inner surface of the blackbody furnace 4 is coated with a black coating with a high emissivity. The radiant heat flux meter 5 to be calibrated is placed at the furnace opening of the blackbody furnace 4. The size of the compensating sheet 2 is the same as the size of the cavity opening of the blackbody furnace 4. The heating component 11 pasted on the outer cylinder wall controls the temperature of the blackbody furnace 4. The second temperature sensor 7, the third temperature sensor 8, the fourth temperature sensor 9, and the fifth temperature sensor 10 are respectively pasted on the furnace cover, the front end, the middle end, and the rear end of the blackbody furnace.

[0031] By detecting the temperature detection values of the second, third, fourth, and fifth temperature sensors, according to the surface emissivity, the inner surface area, and the cavity opening surface area of the coating inside the blackbody furnace 4, the magnitude of the cavity opening radiant heat flux density is calculated by Equation ①, which greatly reduces the influence of the uncertainty of the surface emissivity of the black paint inside the blackbody furnace 4 on the magnitude of the cavity opening radiant heat flux density:

[0032]

[0033] Where T b is the temperature of the blackbody furnace, ε b is the effective emissivity of the ideal blackbody cavity opening, σ is the Stefan-Boltzmann constant equal to 5.67×10 -8 W / (m 2 ·K 4), T2 is the temperature detection value of the second temperature sensor, T3 is the temperature detection value of the third temperature sensor, T4 is the temperature detection value of the fourth temperature sensor, and T5 is the temperature detection value of the fifth temperature sensor.

[0034]

[0035] In the formula, A1 is the inner surface area of the blackbody cavity, A2 is the surface area of the cavity opening, and ε is the emissivity of the inner surface of the cavity.

[0036] By detecting the temperature detection value of the first temperature sensor, according to the ambient temperature, the calibration coefficient of the radiation heat flux meter is calculated by Equation ④. Ignoring the heat conduction loss of the radiation heat flux meter and simplifying the calibration formula for engineering applications, the calibration formula of the radiation heat flux meter is:

[0037]

[0038] In the formula, C is the calibration coefficient of the radiation heat flux meter, T1 is the temperature detection value of the first temperature sensor, T0 is the ambient temperature, and the radiation heat flux density q at the cavity opening b is substituted into the above formula to obtain the calibration coefficient at different temperature differences between the heat flux meter and the ambient temperature.

[0039] During use, the steady-state radiation heat flux meter 5 with a compensating piece in this embodiment is fixed at the inner cavity opening of the blackbody furnace 4, and the side of the heat-absorbing coating of the radiation heat flux meter 5 faces the inner surface of the blackbody furnace 4 to ensure that all the radiation heat flux at the cavity opening is radiated onto the radiation heat flux meter 5. In this embodiment, the temperature of the blackbody furnace 4 is controlled to reach -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, etc. respectively by the heating components 11 pasted on the outer surface of the blackbody furnace 4, so as to generate different radiation heat fluxes. Through the temperature detection values of the first temperature sensor 6, the second temperature sensor 7, the third temperature sensor 8, the fourth temperature sensor 9, the fifth temperature sensor 10 and the ambient temperature sensor (not shown in the figure), under vacuum conditions and with the ambient temperature kept constant at -60°C, the radiation heat flux density at the cavity opening of the blackbody furnace 4 and the calibration coefficient of the radiation heat flux meter at different temperature differences between the heat flux meter and the ambient temperature are obtained from Formulas ① and ④. As Figure 3 shown, when the temperature difference between the radiation heat flux meter and the ambient temperature becomes larger, the heat loss of the radiation heat flux meter also becomes larger. By calibrating at different temperature differences between the radiation heat flux meter and the ambient temperature, the measurement accuracy of the radiation heat flux meter is improved.

[0040] The content not described in detail in this specification belongs to the well-known prior art in the art. At the same time, for those of ordinary skill in the art, there will be changes in the specific implementation manners and application scopes according to the idea of the present invention. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A steady-state radiation heat flux meter with a compensating film, characterized in that, On one side of the heat-sensitive sheet (1) inside the main body, a compensating sheet (2) is provided. A plurality of heat insulation parts (3) are arranged between the heat-sensitive sheet (1) and the compensating sheet (2) to reduce the heat loss between the heat-sensitive sheet (1) and the compensating sheet (2). A plurality of heat insulation parts (3) are arranged between the compensating sheet (2) and the inner wall of the main body to reduce the heat loss from the compensating sheet (2) to the installation surface of the radiation heat flowmeter. The surfaces of the heat-sensitive sheet (1) and the compensating sheet (2) are evenly coated with a black heat-absorbing coating of the same material. A first temperature sensor (6) is attached to the bottom of the heat-sensitive sheet (1).

2. The steady-state radiation heat flux meter with a compensating piece according to claim 1, wherein, The plurality of heat insulation parts (3) are formed by alternately laminating a reflective screen and a spacer layer. The reflective screen is a double-sided aluminized polyimide film with a low emissivity and a high absorptivity, which can reduce radiative heat leakage. The spacer layer is a polyester mesh with a low thermal conductivity, which can reduce heat conduction heat leakage.

3. The steady-state radiation heat flux meter with a compensating piece according to claim 2, characterized in that, The emissivity of the reflective screen is less than or equal to 0.2, and the absorptivity is greater than or equal to 0.

8. The thickness of the reflective screen is 6 - 12 μm; the thickness of the spacer layer mesh is 75 - 200 μm, and the mesh size is 2 - 6 mm; the number of layers of the plurality of heat insulation parts is 5 - 15 layers.

4. A calibration method for the steady-state radiation heat flux meter with a compensating piece according to claim 1, characterized in that, It includes the following steps: S1. Attach a second temperature sensor (7), a third temperature sensor (8), a fourth temperature sensor (9), and a fifth temperature sensor (10) to the furnace lid at the cavity opening end, the front end, the middle end, and the rear end of the outer cylinder wall of the blackbody furnace (4) respectively. Heating components (11) are arranged around the outer cylinder wall and at one end opposite to the cavity opening; Place the radiation heat flowmeter (5) to be calibrated at the inner cavity opening of the blackbody furnace (4) in a vacuum environment, with the heat-sensitive sheet (1) facing the inner cavity of the blackbody furnace. S2. Control the heating component (11) to change the temperature of the blackbody furnace (4), generate different fixed radiant heat fluxes, and calculate the magnitude q of the radiant heat flux density at the cavity opening b : Among them, q b is the radiant heat flux density at the cavity opening, ε b is the effective emissivity at the cavity opening of the ideal blackbody furnace, T b is the temperature of the blackbody furnace, σ is the Stefan-Boltzmann constant equal to 5.67×10 -8 W / (m 2 ·K 4 ), T2 is the temperature detection value of the second temperature sensor, T3 is the temperature detection value of the third temperature sensor, T4 is the temperature detection value of the fourth temperature sensor, and T5 is the temperature detection value of the fifth temperature sensor; Where A1 is the inner cavity surface area, A2 is the cavity opening surface area, and ε is the inner cavity surface emissivity. S3. Calculate the calibration coefficient of the radiation heat flowmeter by obtaining the temperature detection value of the first temperature sensor and the ambient temperature. The specific formula is as follows: where C is the calibration coefficient of the radiation heat flux meter, T1 is the temperature detection value of the first temperature sensor, T0 is the ambient temperature, and σ is the Stefan-Boltzmann constant equal to 5.67×10 -8 W / (m 2 ·K 4 ). Substitute the radiation heat flux density q b at the cavity opening in S2 into the above formula to obtain the calibration coefficient at different temperature differences between the heat flux meter and the ambient temperature.

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