TWI760248B - Transient thermal diffusivity measurement method of heat dissipation module - Google Patents

Abstract

A method for measuring the transient thermal diffusivity of a heat dissipation module is mainly to select two measurement points on the surface of a heat dissipation module, and make the two measurement points located on the same side of a thermal center point but at different distances, and then separately Measure the temperature of the two measuring points, and substitute the following formula (1), wherein the formula (1) is an analytical solution to the energy equation;

After substituting the above equation (1), the following equations (2) and (3) can be obtained to obtain M;

Finally, the distance X1 between M and the first measurement point and the temperature T1 at a certain moment in the transient state are substituted into the formula (1), and the value of the thermal diffusivity α can be obtained. The value of the thermal diffusivity α is Used to represent the transient thermal diffusion performance of the cooling module.

Description

Transient thermal diffusivity measurement method of heat dissipation module

The present invention is related to the measurement technology of thermal diffusivity, in particular to a method for measuring the transient thermal diffusivity of a heat dissipation module.

The heat dissipation module is a device widely used in computers or heat-generating chip modules (such as LED light panels). Most of the known heat dissipation modules currently have a plurality of heat dissipation fins disposed on or integrally formed on a metal base plate (aluminum or copper), and the metal base plate is attached to a heat source, thereby providing heat energy to the heat source to the side. Square conduction and upward conduction through the plurality of heat dissipation fins to dissipate heat.

The aforementioned technology of using the metal base plate as a heat dissipation module to attach to the heat source, the effect of metal heat conduction can be considered acceptable when the heat energy of the heat source is not high, but in the current computer CPU (Central Processing Unit) or LED light board Under the situation that the heat energy generated per unit time is getting higher and higher, the above-mentioned technology of using the metal base plate as the heat dissipation module is obviously not enough to use the speed of metal heat conduction. Therefore, some people propose to use a vapor chamber (vapor chamber) to be placed under the metal bottom plate and attached to the heat source, so as to become a heat dissipation module including a vapor chamber. The characteristic of rapid temperature uniformity achieves the effect of quickly dispersing heat energy to various positions of the uniform temperature and heat conduction plate, thus obtaining a better heat dissipation effect.

However, although the current technology has been developed to use a combination of a thermally conductive plate and a heat dissipation module to enhance the heat dissipation effect, however, for the heat dissipation performance of the heat dissipation module, there are only conceptual fast and slow or The difference between good and bad is just that, there is no specific and data-based measurement technology, and the observed results can only be obtained by measuring instruments for a long time.

The main purpose of the present invention is to provide a transient thermal diffusivity energy measurement method of a heat dissipation module, which is a specific and data-based measurement technology.

Another object of the present invention is to provide a method for measuring the transient thermal diffusivity of a heat dissipation module, which can provide a user with specific measurement results, so that the user can judge whether the heat dissipation effect of the measured heat dissipation module is good. Bad.

In order to achieve the above object, the present invention provides a method for measuring the transient thermal diffusivity of a heat dissipation module, comprising the following steps A) to D): A) determining a first measurement point and a second measurement point: The surface used for the heat dissipation module to be attached to a heat source is defined as a heat conduction surface, the center point of the area where the heat conduction surface is attached to the heat source is defined as a heat center point, and the heat center point is defined as the heat center point on the heat conduction surface. A rectangle is defined as the center, and the length and width of the rectangle do not exceed the edge of the heat-conducting surface; a first measurement point and a first measuring point are arbitrarily selected between the outer side of the rectangle on the heat-conducting surface and the edge of the heat-conducting surface. Two measurement points, the straight line distance between the first measurement point and the side of the rectangle or the virtual extension of the side is greater than the straight line between the second measurement point and the side of the rectangle or the virtual extension of the side distance; B) measuring temperature: the heat dissipation module is attached to the heat source, and when the heat source is stably generating heat, the temperature of the first measurement point and the temperature of the second measurement point are respectively measured over time. change, and the heat dissipation state of the heat dissipation module no longer changes, that is, it enters a steady state; C) Substitute into the calculation formula: Substitute the temperature and distance of the first measurement point and the second measurement point into the following formula (1) And calculation: using the steady-state temperature T1 of the distance X1 of the first measurement point and the second measurement For the steady-state temperature T2 of the distance X2 from the point, substitute the following formula (1), where the formula (1) is an analytical solution to the energy equation;

，

，

，dX=X1-X2，

，

；其中，M為熱傳導與熱對流強度比，h為對流熱傳係數，K為熱傳導係數，D為特徵直徑，T為溫度，t為時間，X為位置，L為特徵長度，λ為特徵值，dx為第一量測點與第二量測點之間的距離，X1為該第一量測點與該矩形之該邊或該邊之虛擬延長線的直線距離；在上述之代入式(1)運算之後，可得下列式(2)及式(3)； in,

,

,

, dX = X 1 - X 2,

,

; where M is the ratio of heat conduction to heat convection intensity, h is the convective heat transfer coefficient, K is the heat transfer coefficient, D is the characteristic diameter, T is the temperature, t is the time, X is the position, L is the characteristic length, and λ is the characteristic value , dx is the distance between the first measurement point and the second measurement point, X1 is the straight-line distance between the first measurement point and the side of the rectangle or the virtual extension line of the side; in the above substitution formula ( 1) After the operation, the following formulas (2) and (3) can be obtained;

M can be obtained from the above formulas (2) and (3); D) Result: the temperature of the distance X1 between the M obtained in step C) and the first measurement point at a certain moment t1 in the transient state Substitute T1 into Equation (1) to obtain the value of the thermal diffusivity α, which is used to represent the transient thermal diffusivity of the heat dissipation module.

Therefore, the present invention is a specific and data-based measurement technology that can be used by the industry, and further, the present invention can provide the user with specific measurement results for the user to judge the heat dissipation effect of the measured heat dissipation module good or bad.

11: Cooling module

12: Metal bottom plate

14: cooling fins

15: Temperature and heat conduction plate

151: Thermal surface

152: Rectangle

16: Fan

O: hot center point

O1: The first measurement point

O2: The second measuring point

X1: straight line distance

X2: Straight line distance

FIG. 1 is a flow chart of a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram of a combination of a heat dissipation module according to a preferred embodiment of the present invention.

3 is a schematic diagram of the bottom surface of a heat dissipation module according to a preferred embodiment of the present invention.

FIG. 4 is a schematic diagram of the assembly of another heat dissipation module according to a preferred embodiment of the present invention.

FIG. 5 is a schematic bottom view of another heat dissipation module according to a preferred embodiment of the present invention.

In order to illustrate the technical features of the present invention in detail, the following preferred embodiments are given and described in conjunction with the drawings as follows, wherein:

As shown in FIG. 1 to FIG. 3 , a method for measuring the transient thermal diffusivity of a heat dissipation module according to a preferred embodiment of the present invention is mainly performed by the following steps:

A) Determine a first measurement point and a second measurement point: use a heat dissipation module 11 to attach to a heat source (not shown in the figure) (such as a computer's central processing unit CPU or an LED chip circuit board) The surface of the heat sink is defined as a heat conduction surface 151. In this embodiment, the heat dissipation module 11 has a metal base plate 12 and a plurality of heat dissipation fins 14 extending upward from the metal base plate 12. Its top surface is attached to the bottom surface of the metal base plate 12, and the bottom surface of the temperature-equalizing heat-conducting plate 15 is used as the heat-conducting surface 151. The heat dissipation module 11 also has a fan 16 disposed on the plurality of heat-dissipating fins 14; the The center point of the area where the thermally conductive surface 151 is attached to the heat source is defined as a thermal center point O, and a rectangle 152 is defined on the thermally conductive surface 151 with the thermal center point O as the center, and the length and width of the rectangle 152 do not exceed the thermal center point O. The edge of the heat-conducting surface 151; between the outer side of the rectangle 152 on the heat-conducting surface 151 and the edge of the heat-conducting surface 151, select a first measurement point O1 and a second measurement point O2, the first measurement The straight-line distance X1 between the point O1 and the side of the rectangle 152 is greater than the The linear distance X2 between the second measurement point O2 and the side of the rectangle 152 . In addition, in this embodiment, the second measurement point O2 is located on the vertical connection line between the first measurement point O1 and the side of the rectangle 152 , that is, the second measurement point O2 and the first measurement point O2 A measurement point O1 exhibits a linear relationship along its vertical line with the side of the rectangle 152 . In addition, in this embodiment, the size of the rectangle 152 and the size of the heat source are taken as an example for illustration. However, the size of the rectangle 152 may be smaller than the length and width of the heat source, or larger than the size of the heat source. The length and width of the heat source are considered to overlap with the heat center point O when the rectangle 152 is extremely small.

B) Measure temperature: place the heat dissipation module 11 on the heat source, and measure the temperature of the first measurement point O1 and the second measurement point O2 over time when the heat source is stably generating heat changes, and the heat dissipation state of the heat dissipation module 11 no longer changes, that is, it enters a steady state.

C) Substitute into calculation formula: Substitute the temperature and distance of the first measurement point O1 and the second measurement point O2 into the following formula (1) to calculate:

Taking the steady-state temperature T1 of the distance X1 of the first measurement point O1 and the steady-state temperature T2 of the distance X2 of the second measurement point O2, substitute the following formula (1), wherein the formula (1) is for Analytical solution of the energy equation;

，

，

，dX=X1-X2，

，

。 in,

,

,

, dX = X 1 - X 2,

,

.

Among them, M is the ratio of heat conduction to heat convection intensity, h is the convective heat transfer coefficient, K is the heat conduction coefficient, D is the characteristic diameter, T is the temperature, t is the time, X is the position, L is the characteristic length, and λ is the characteristic value, dx is the distance between the first measurement point O1 and the second measurement point O2, X1 is the straight-line distance between the first measurement point O1 and the side of the rectangle 152, and X2 is the first measurement point The linear distance between O2 and the side of the rectangle 152 .

After the above-mentioned substitution equation (1) operation, the following equations (2) and (3) can be obtained:

M can be obtained from the above equations (2) and (3).

D) Result: Substitute the temperature T1 of the distance X1 between the M obtained in step C) and the first measurement point O1 at a certain moment t1 of the transient state into the formula (1), and the thermal diffusivity α can be obtained. The value of the thermal diffusivity α is used to represent the transient thermal diffusivity of the heat dissipation module 11 .

The steps of the measurement method of the present invention have been described above, and the actual data will be used to describe the following.

Under the condition that the linear distance between the first measurement point O1 and the side of the rectangle 152 is X1=0.16m (meters) and the linear distance between the second measurement point O2 and the side of the rectangle 152 is X2=0.07m At a certain moment (ie, steady state), the temperature t1 of the first measurement point O1 = 67.5°C, and the temperature t2 of the second measurement point O2 = 71.5°C. After substituting in the above formula, the thermal diffusivity α=1.187cm ² /s can be obtained. In this way, the heat dissipation effect of the heat dissipation module 11 can be judged by the value of the thermal diffusivity α.

The above-mentioned heat dissipation module 11 is described by taking the heat dissipation module having the temperature uniformity and heat conduction plate 15 as an example. However, if the heat dissipation module does not include the temperature uniformity heat conduction plate 15, it simply has a metal base plate 12 and a plurality of heat dissipation modules. For the fins 14, as shown in FIG. 4, the method of the present invention can also be used on the bottom surface of the fins 14 to measure the value of the thermal diffusivity α of the heat dissipation module 11.

In the above description, the relationship between the second measurement point O2 and the vertical connection line between the first measurement point O1 and the side of the rectangle 152 is described. However, as shown in FIG. 5 , the fact is The second measurement point O2 may not be located on the vertical connection line between the first measurement point O1 and the side of the rectangle 152 , but presents a non-linear relationship. This is because the technique of the present application mainly calculates the straight-line distance between the first measurement point O1 and the second measurement point O2 and the side of the rectangle 152 , so even if the relationship is non-linear, the calculation can be performed. For example, as shown in FIG. 5 , if the position of the first measurement point O1 is beyond the range of the side of the rectangle 152 , the vertical connection line cannot be connected to the side. In this case, the side can be extended to obtain A virtual extension line for forming a vertical connection between the first measurement point O1 and the second measurement point O2 and the virtual extension line.

The technical focus of this case is that the first measurement point O1 and the second measurement point O2 are both located outside of one side of the rectangle 152 , that is, outside of the same side, so they belong to one-dimensional thermal diffusion measurement technology. The technology of the present invention does not include the situation that the first measuring point O1 is located outside one side of the rectangle 152 and the second measuring point O2 is located outside the other side.

To sum up, the present invention is a specific and data-based measurement technology, which can provide the user with a specific measurement result, that is, the thermal diffusivity α, for the user to judge the heat dissipation of the heat dissipation module 11 to be measured. The effect is good or bad.

11: Cooling module

15: Temperature and heat conduction plate

151: Thermal surface

152: Rectangle

O: hot center point

O1: The first measurement point

O2: The second measuring point

X1: straight line distance

X2: Straight line distance

Claims (5)

A method for measuring transient thermal diffusivity of a heat dissipation module, comprising the following steps: A) Determining a first measurement point and a second measurement point: the surface of the heat dissipation module used to attach to a heat source is defined as a heat conduction surface, and the center point of the area where the heat conduction surface is attached to the heat source is defined is a thermal center point, and defines a rectangle with the thermal center point as the center on the heat-conducting surface, and the length and width of the rectangle do not exceed the edge of the heat-conducting surface; the outer side of the rectangle on the heat-conducting surface and the Between the edges of the heat-conducting surface, a first measurement point and a second measurement point are arbitrarily selected, and the linear distance between the first measurement point and the side of the rectangle or the virtual extension of the side is greater than the second measurement point The straight-line distance between the measuring point and the side of the rectangle or the virtual extension of the side; B) Measurement of temperature: The heat dissipation module is attached to the heat source, and when the heat source is stably generating heat, the temperature of the first measurement point and the temperature of the second measurement point are respectively measured over time. And the heat dissipation state of the heat dissipation module no longer changes, that is, it enters a steady state; C) Substitute into calculation formula: Substitute the temperature and distance of this first measurement point and this second measurement point into the following formula (1) and calculation: Taking the steady-state temperature T1 of the distance X1 of the first measuring point and the steady-state temperature T2 of the distance X2 of the second measuring point, substitute the following equation (1), where the equation (1) is the equation for the energy seek analytical solution;

in,

,

,

, dX = X 1 - X 2,

,

; Among them, M is the ratio of heat conduction to heat convection intensity, h is the convective heat transfer coefficient, K is the heat conduction coefficient, D is the characteristic diameter, T is the temperature, t is the time, X is the position, L is the characteristic length, and λ is the characteristic value, dx is the first The distance between a measurement point and the second measurement point, X1 is the straight-line distance between the first measurement point and the side of the rectangle or the virtual extension of the side; After substituting the above-mentioned equation (1), the following equations (2) and (3) can be obtained;

M can be obtained from the above formulas (2) and (3); D) Result: Substitute the temperature T1 of the distance X1 between the M obtained in step C) and the first measurement point at a certain moment t1 of the transient state into the formula (1), and the thermal diffusivity α can be obtained. The value of the thermal diffusivity α is used to represent the transient thermal diffusivity of the heat dissipation module. The method for measuring transient thermal diffusivity of a heat dissipation module according to claim 1, wherein: the second measurement point is located between the first measurement point and the side of the rectangle or a virtual extension of the side connected vertically. The method for measuring transient thermal diffusivity of a heat dissipation module according to claim 1, wherein: the second measurement point is not located on the virtual extension line between the first measurement point and the side or the side of the rectangle on the vertical connection. The method for measuring transient thermal diffusivity of a heat dissipation module according to claim 1, wherein: the heat dissipation module has a metal base plate and a plurality of heat dissipation fins, and the bottom surface of the metal base plate is used as the heat conduction surface. The method for measuring the transient thermal diffusivity of a heat dissipation module according to claim 1, wherein: the heat dissipation module has a metal base plate and a plurality of heat dissipation fins, and has a heat-dissipating heat-dissipating plate on its top surface. On the bottom surface of the metal base plate, the bottom surface of the temperature uniform heat conduction plate is used as the heat conduction surface.

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