Method for measuring thermal contact resistance of thin test piece

Abstract

The invention discloses a method for measuring contact thermal resistance of a thin test piece, and relates to the technical field of thermal resistance testing. A first gel sheet is stacked between a heating rod and a cooling rod, and a temperature sensor is arranged between a thin test piece A, a thin test piece B and the first gel sheet or between the gel sheet and the thin test piece; and calculating the contact thermal resistance between the thin test piece A and the thin test piece B by calculating the total thermal resistance value and subtracting the inherent thermal resistance values of the thin test piece A and the thin test piece B. Compared with a traditional steady-state direct method, a temperature sensor does not need to be inserted into a thin test piece, for the thin test piece which is difficult to connect with the temperature sensor, the TCR measuring process is simpler and more convenient, certain reference significance is achieved for engineering practice, and the adopted gel sheet has constant thermal resistance under vacuum and atmospheric pressure, so that the TCR measuring accuracy is improved. Due to the constant thermal resistance of the gel sheet and the independence of the gel sheet on the contact pressure and the air pressure, the accuracy of a measurement result is realized.

Description

Technical Field

[0001] The invention relates to the technical field of thermal resistance testing, in particular to a method for measuring the contact thermal resistance of a thin test piece. Background Art

[0002] The steady-state direct method used in the traditional measurement of contact thermal resistance mainly consists of a heating rod and a cooling rod, a temperature sensor, a thermal insulation material, a heater, a cooler, a load handling mechanism, and a controller. Five platinum resistance temperature detectors (RTDs) with a diameter of 0.5 mm are inserted into the holes drilled on the heating and cooling rods at equal intervals and bonded with silver paste to measure the temperature distribution of the heating and cooling rods. Precision calibration is performed at three standard points of 0, 100, and 200 ° C, respectively, with an accuracy of 0.01 ° C. The five sensors in the heating and cooling rods ensure accurate measurement in case one or both of the sensors lose adhesion to the rod in the vacuum. There is an electric heater on the heating rod and a Peltier cooler through a heat sink under the cooling rod. A gold-plated stainless steel plate surrounds the rod as a radiation shield to prevent heat from being lost from the rod to the surrounding environment through radiation. In order to minimize the lateral temperature difference between the shield and the rod, the radiation shield is in direct contact with the heat sink. In addition, a thermal insulation material made of PEEK (polyetheretherketone) covers the radiation shield, heater, and cooler.

[0003] But the study found that this method is not suitable for measuring the TCR of thin specimens. Because it is very difficult, and sometimes even impossible, to accurately connect the sensor to a thin specimen. However, in many applications, it is often necessary to measure the TCR of thin specimens. Therefore, how to measure the TCR of thin pieces is a question worth exploring. Summary of the invention

[0004] In view of this, the present invention proposes a method for measuring the contact thermal resistance of a thin specimen. The method does not require inserting a temperature sensor into the thin specimen, and the measurement method is simpler and more convenient.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for directly measuring the contact thermal resistance of a thin specimen comprises the following steps:

[0007] Step 1: Measure the thickness of thin specimen A and thin specimen B, denoted as δ A With δ B , measure the thermal conductivity values ​​of thin specimen A and thin specimen B, respectively denoted as k A With k B , calculate the inherent thermal resistance R of thin specimen A A =δ A / k A , calculate the inherent thermal resistance R of thin specimen BB =δ B / k B , thermal resistance value unit is m 2 K / W;

[0008] Step 2, stacking the first gel sheet, the first temperature sensor, the thin specimen A, the thin specimen B, the second temperature sensor and the second gel sheet in sequence between the heating rod and the cooling rod;

[0009] Step 3, calculating the temperature difference ΔT between the first temperature sensor and the second temperature sensor, and using the traditional steady-state direct method to calculate the heat flux q of the contact surface between the thin specimen A and the thin specimen B;

[0010] Step 4, calculating the thermal resistance R=△T / q between the first temperature sensor and the second temperature sensor;

[0011] Step 5: Calculate the contact thermal resistance R between thin specimen A and thin specimen B A-B =RR A -R B .

[0012] Furthermore, the first gel sheet is used to adhere the first temperature sensor to the surface of thin specimen A, and the second gel sheet is used to adhere the second temperature sensor to the surface of thin specimen B; the first gel sheet and the second gel sheet have the same size, and the thickness of the first gel sheet and the second gel sheet are both greater than the first temperature sensor and the second temperature sensor.

[0013] Furthermore, the contact surface area between the first gel sheet and the thin specimen A is equal to the contact surface area between the second gel sheet and the thin specimen B, and the difference between the contact surface area between the gel sheet and the thin specimen and the contact surface area between the gel sheet and the heating rod / cooling rod does not exceed 5%.

[0014] Furthermore, the first gel sheet and the second gel sheet are both silicone gel mixed with high thermal conductivity ceramic powder.

[0015] A method for indirectly measuring the contact thermal resistance of a thin specimen comprises the following steps:

[0016] Step 1: Place the gel sheet between the heating rod and the cooling rod, and measure the thermal resistance of the gel sheet under a pressure of 10-500KPa, and record it as R 凝胶 ;

[0017] Step 2: Measure the thickness of thin specimen A and thin specimen B, denoted as δ A With δ B , measure the thermal conductivity values ​​of thin specimen A and thin specimen B, respectively denoted as k A With k B , calculate the inherent thermal resistance R of the thin specimen A A =δ A / k A , calculate the inherent thermal resistance R of thin specimen B B =δ B / k B , thermal resistance value unit is m 2 K / W;

[0018] Step 3, stacking the first gel sheet, the thin specimen A, the thin specimen B and the second gel sheet in sequence between the heating rod and the cooling rod; wherein the size and material of the first gel sheet and the second gel sheet are consistent with the gel sheet in step 1; and the heating rod and the cooling rod both include a platinum resistance temperature detector;

[0019] Step 4: Measure the total thermal resistance R between the heating rod and the cooling rod using the platinum resistance temperature detectors on the heating rod and the cooling rod. 总 ;

[0020] Step 5: Calculate the contact thermal resistance R between thin specimen A and thin specimen B A-B =R 总 -R 凝胶1 -R 凝胶2 -R A -R B ;

[0021] Among them, R 凝胶1 With R 凝胶2 are the thermal resistance values ​​of the first gel sheet and the second gel sheet respectively, and:

[0022] R 凝胶 =R 凝胶1 =R 凝胶2 .

[0023] Furthermore, the first gel sheet is used to adhere the heating rod to the surface of the thin specimen A, and the second gel sheet is used to adhere the cooling rod to the surface of the thin specimen B; the contact surface area between the first gel sheet and the thin specimen A is equal to the contact surface area between the second gel sheet and the thin specimen B, and the difference between the contact surface area between the gel sheet and the thin specimen and the contact surface area between the gel sheet and the heating rod / cooling rod is no more than 5%.

[0024] Furthermore, the first gel sheet and the second gel sheet are both silicone gel mixed with high thermal conductivity ceramic powder.

[0025] Due to the adoption of the above technical solution, the beneficial effects of the present invention compared with the prior art are:

[0026] 1. Compared with the traditional steady-state direct method, the present invention does not need to insert a temperature sensor into a thin specimen, and for thin specimens that are difficult to connect temperature sensors, the process of measuring TCR is simpler and more convenient, which has certain reference significance for engineering practice.

[0027] 2. The gel sheet used in the present invention has a constant thermal resistance both under vacuum and atmospheric pressure. The constant thermal resistance of the gel sheet and its independence from contact pressure and air pressure achieve the accuracy of the measurement results. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] A method for directly measuring the contact thermal resistance of a thin specimen comprises the following steps:

[0030] Step 1: Measure the thickness of thin specimen A and thin specimen B, denoted as δ A With δ B , measure the thermal conductivity values ​​of thin specimen A and thin specimen B, respectively denoted as k A With k B , calculate the inherent thermal resistance R of the thin specimen A A =δ A / k A , calculate the inherent thermal resistance R of thin specimen B B =δ B / k B , thermal resistance value unit is m 2 K / W;

[0031] Specifically, in this embodiment, thin specimen A and thin specimen B are made of copper, and both have a thickness of 3 mm, that is, δ A =δ B =3mm. The thermal conductivity of thin specimens A and B was tested to be 380W / (m·k), i.e. k A =k B =380W / m·k. According to the formula R=δ / k, the thermal resistance values ​​of thin specimen A and thin specimen B are calculated respectively, that is, R A =R B =7.89×10 -6 m 2 ·K / W.

[0032] Step 2, stacking the first gel sheet, the first temperature sensor, the thin specimen A, the thin specimen B, the second temperature sensor and the second gel sheet in sequence between the heating rod and the cooling rod;

[0033] Specifically, in this embodiment, two platinum resistance temperature detectors (RTDs) with a diameter of 0.5 mm are respectively adhered to the back of thin specimen A and thin specimen B with silver paste. The temperature sensors are precisely calibrated at three standard points of 0, 100, and 200°C, with an accuracy of 0.01°C.

[0034] Step 3, calculating the temperature difference ΔT between the first temperature sensor and the second temperature sensor, and using the traditional steady-state direct method to calculate the heat flux q of the contact surface between the thin specimen A and the thin specimen B;

[0035] In this embodiment, the temperature difference ΔT is 0.25K when the pressure is 100KPa, the vacuum is 0.1Pa, and the temperature is 80°C. Five platinum resistance temperature detectors (RTDs) with a diameter of 0.5 mm are inserted into the holes drilled on the heating and cooling rods at equal intervals and bonded with silver paste to measure the temperature distribution of the heating and cooling rods. According to the formula q = (q 1 +q 2 ) / 2 calculates the heat flux q through the interface, where q 1 ,q 2 are the average values ​​of heat flux through thin specimen A and thin specimen B, respectively. This value can be directly calculated by the steady-state direct method equipment. After measurement, this value is q = 2.07 × 10 3 W / m 2 .

[0036] Step 4, calculating the thermal resistance R=△T / q between the first temperature sensor and the second temperature sensor;

[0037] In this embodiment, R = 1.21 × 10 -4 m 2 ·K / W.

[0038] Step 5: Calculate the contact thermal resistance R between thin specimen A and thin specimen B A-B =RR A -R B .

[0039] Furthermore, the first gel sheet is used to adhere the first temperature sensor to the surface of thin specimen A, and the second gel sheet is used to adhere the second temperature sensor to the surface of thin specimen B; the first gel sheet and the second gel sheet have the same size, and the thickness of the first gel sheet and the second gel sheet are both greater than the first temperature sensor and the second temperature sensor.

[0040] (1) In this embodiment, R A-B =RR A -R B =1.05×10 -4 m 2 ·K / W. The transient method was used for verification. After testing, the R measured by the transient method was 1.07×10 -4 m 2 The error rate of K / W is less than 5%, which proves the effectiveness of this method.

[0041] Furthermore, the contact surface area between the first gel sheet and the thin specimen A is equal to the contact surface area between the second gel sheet and the thin specimen B, and the difference between the contact surface area between the gel sheet and the thin specimen and the contact surface area between the gel sheet and the heating rod / cooling rod does not exceed 5%.

[0042] Furthermore, the first gel sheet and the second gel sheet are both silicone gel mixed with high thermal conductivity ceramic powder.

[0043] A method for indirectly measuring the contact thermal resistance of a thin specimen comprises the following steps:

[0044] Step 1: Place the gel sheet between the heating rod and the cooling rod, and measure the thermal resistance of the gel sheet under a pressure of 10-500KPa, and record it as R 凝胶 ;

[0045] Step 2: Measure the thickness of thin specimen A and thin specimen B, denoted as δ A With δ B , measure the thermal conductivity values ​​of thin specimen A and thin specimen B, respectively denoted as k A With k B , calculate the inherent thermal resistance R of the thin specimen A A =δ A / k A , calculate the inherent thermal resistance R of thin specimen B B =δ B / k B , thermal resistance value unit is m 2 K / W;

[0046] Specifically, in this embodiment, thin specimen A and thin specimen B are made of copper, and both have a thickness of 3 mm, that is, δ A =δ B =3mm. The thermal conductivity of thin specimens A and B was tested to be 380W / (m·k), i.e. k A =k B =380W / m·k. According to the formula R=δ / k, the thermal resistance values ​​of thin specimen A and thin specimen B are calculated respectively, that is, R A =R B =7.89×10 -6 m 2 ·K / W.

[0047] Step 3, stacking the first gel sheet, the thin specimen A, the thin specimen B and the second gel sheet in sequence between the heating rod and the cooling rod; wherein the size and material of the first gel sheet and the second gel sheet are consistent with the gel sheet in step 1; and the heating rod and the cooling rod both include a platinum resistance temperature detector;

[0048] Step 4: Measure the total thermal resistance R between the heating rod and the cooling rod using the platinum resistance temperature detectors on the heating rod and the cooling rod. 总 ;

[0049] Specifically, in this embodiment, the total thermal resistance R between the heating rod and the cooling rod of the first gel sheet, the thin specimen A, the thin specimen B, and the second gel sheet is measured at a pressure P of 100 KPa, a vacuum degree of 0.1 Pa, and a temperature of 80°C. 总 =5.90×10 - 4 m 2 ·K / W.

[0050] Step 5: Calculate the contact thermal resistance R between thin specimen A and thin specimen B A-B =R 总 -R 凝胶1 -R 凝胶2 -R A -R B ;

[0051] Among them, R 凝胶1 With R 凝胶2 are the thermal resistance values ​​of the first gel sheet and the second gel sheet respectively, and:

[0052] R 凝胶 =R 凝胶1 =R 凝胶2 .

[0053] (3) Specifically, in this embodiment, R 凝胶 =R 凝胶1 =R 凝胶2 =2.35×10 -4 m 2 ·K / W. R A-B =1.04×10 - 4 m 2 ·K / W. The transient method is used for verification. After testing, the R A-B =1.07×10 -4 m 2 The error rate of K / W is less than 5%, which proves the effectiveness of this method.

[0054] Furthermore, the first gel sheet is used to adhere the heating rod to the surface of the thin specimen A, and the second gel sheet is used to adhere the cooling rod to the surface of the thin specimen B; the contact surface area between the first gel sheet and the thin specimen A is equal to the contact surface area between the second gel sheet and the thin specimen B, and the difference between the contact surface area between the gel sheet and the thin specimen and the contact surface area between the gel sheet and the heating rod / cooling rod is no more than 5%.

[0055] Furthermore, the first gel sheet and the second gel sheet are both silicone gel mixed with high thermal conductivity ceramic powder.

[0056] In this embodiment, the first gel sheet and the second gel sheet are λ-GEL gel sheets produced by Taica Co., Ltd. This gel is a silicone gel mixed with high thermal conductivity ceramic powder. Due to its extremely high softness and viscosity, the TCR can be greatly reduced. The gel sheet is placed between the heating rod and the cooling rod. After testing, no matter how small the contact pressure is, and after applying a large initial contact pressure, no matter what gas pressure is applied, the TCR of the gel sheet remains constant at 2.35×10 -4 m 2 K / W (Note: This value includes the contact thermal resistance between the heating rod / gel sheet and the cooling rod / gel sheet). This can be explained by the fact that the gel sheet is completely adhered to the surface and the gas trapped in the interface cannot be driven off even under very high vacuum.

[0057] In summary, compared with the traditional steady-state direct method, the present invention does not need to insert a temperature sensor into a thin specimen, and for thin specimens that are difficult to connect temperature sensors, the process of measuring TCR is simpler and more convenient, which has certain reference significance for engineering practice. The gel sheet used has a constant thermal resistance under vacuum and atmospheric pressure. The constant thermal resistance of the gel sheet and its independence from contact pressure and air pressure achieve the accuracy of the measurement results.

[0058] Those skilled in the art will appreciate that the embodiments described are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to the embodiments described. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for directly measuring the contact thermal resistance of a thin specimen, characterized in that: The following steps are involved: Step 1: Measure the thickness of thin specimen A and thin specimen B, denoted as δ A With δ B , measure the thermal conductivity values ​​of thin specimen A and thin specimen B, respectively denoted as k A With k B , calculate the inherent thermal resistance R of thin specimen A A =δ A / k A , calculate the inherent thermal resistance R of thin specimen B B =δ B / k B , thermal resistance value unit is m 2 K / W; Step 2, stacking the first gel sheet, the first temperature sensor, the thin specimen A, the thin specimen B, the second temperature sensor and the second gel sheet in sequence between the heating rod and the cooling rod; Step 3, calculating the temperature difference ΔT between the first temperature sensor and the second temperature sensor, and using the traditional steady-state direct method to calculate the heat flux q of the contact surface between the thin specimen A and the thin specimen B; Step 4, calculating the thermal resistance R=△T / q between the first temperature sensor and the second temperature sensor; Step 5: Calculate the contact thermal resistance R between thin specimen A and thin specimen B A-B =RR A -R B .

2. A method for directly measuring the contact thermal resistance of a thin specimen according to claim 1, characterized in that: The first gel sheet is used to adhere the first temperature sensor to the surface of the thin specimen A, and the second gel sheet is used to adhere the second temperature sensor to the surface of the thin specimen B; the first gel sheet and the second gel sheet have the same size, and the thickness of the first gel sheet and the second gel sheet are both greater than the first temperature sensor and the second temperature sensor.

3. A method for directly measuring the contact thermal resistance of a thin specimen according to claim 1, characterized in that: The contact surface area between the first gel sheet and the thin specimen A is equal to the contact surface area between the second gel sheet and the thin specimen B, and the difference between the contact surface area between the gel sheet and the thin specimen and the contact surface area between the gel sheet and the heating rod / cooling rod is no more than 5%.

4. A method for directly measuring the contact thermal resistance of a thin specimen according to claim 1, characterized in that: The first gel sheet and the second gel sheet are both silicone gel mixed with high thermal conductivity ceramic powder.

5. A method for indirectly measuring the contact thermal resistance of a thin specimen, characterized in that: The following steps are involved: Step 1: Place the gel sheet between the heating rod and the cooling rod, and measure the thermal resistance of the gel sheet under a pressure of 10-500KPa, and record it as R 凝胶 ; Step 2: Measure the thickness of thin specimen A and thin specimen B, denoted as δ A With δ B , measure the thermal conductivity values ​​of thin specimen A and thin specimen B, respectively denoted as k A With k B , calculate the inherent thermal resistance R of thin specimen A A =δ A / k A , calculate the inherent thermal resistance R of thin specimen B B =δ B / k B , thermal resistance value unit is m 2 K / W; Step 3, stacking the first gel sheet, the thin specimen A, the thin specimen B and the second gel sheet in sequence between the heating rod and the cooling rod; wherein the size and material of the first gel sheet and the second gel sheet are consistent with the gel sheet in step 1; and the heating rod and the cooling rod both include a platinum resistance temperature detector; Step 4: Measure the total thermal resistance R between the heating rod and the cooling rod using the platinum resistance temperature detectors on the heating rod and the cooling rod. 总 ; Step 5: Calculate the contact thermal resistance R between thin specimen A and thin specimen B A-B =R 总 -R 凝胶1 -R 凝胶2 -R A -R B ; Among them, R 凝胶1 With R 凝胶2 are the thermal resistance values ​​of the first gel sheet and the second gel sheet respectively, and: R 凝胶 =R 凝胶1 =R 凝胶2 。 6. A method for indirectly measuring the contact thermal resistance of a thin specimen according to claim 5, characterized in that: The first gel sheet is used to adhere the heating rod to the surface of the thin specimen A, and the second gel sheet is used to adhere the cooling rod to the surface of the thin specimen B; the contact surface area between the first gel sheet and the thin specimen A is equal to the contact surface area between the second gel sheet and the thin specimen B, and the difference between the contact surface area between the gel sheet and the thin specimen and the contact surface area between the gel sheet and the heating rod / cooling rod is no more than 5%.

7. The method for indirectly measuring the contact thermal resistance of a thin specimen according to claim 5, characterized in that: The first gel sheet and the second gel sheet are both silicone gel mixed with high thermal conductivity ceramic powder.