Thermal conductance measurement method and thermal conductance measurement system

Abstract

[Problem] To identify the thermal conductance of a heat source and contribute to the effective utilization of unused thermal energy. [Solution] The present invention involves: making a heat conduction path having a cooling source at one end be connected via the other end to a heat source to be measured (S10); installing a heating element, which can be controlled so that the amount of heat generation fluctuates by applying fluctuating heating energy, in the heat conduction path, and measuring the temperature in the heat conduction path to acquire a first temperature when affected by the heat generation of the heating element and a second temperature when not affected by the heat generation of the heating element (S30, S50); and calculating the heat conductance of the heat source on the basis of the difference (S60) between the first temperature and the second temperature and the heating energy when the first temperature is measured (S80). As a result, the heat conductance of the heat source can be calculated without the need for identifying the specific heat, mass, or the like of the heat source, so that it is possible to contribute to the effective utilization of unused thermal energy of the heat source.

Description

Thermal conductance measurement method and thermal conductance measurement system

[0001] The present invention relates to a thermal conductance measurement method and a thermal conductance measurement system for measuring the thermal conductance of a heat source.

[0002] For example, thermal energy is discarded as waste heat in industrial plants that handle thermal energy, various devices that use heat sources, combustion devices, internal combustion engines, incinerators, hot spring water flow paths, exhaust ducts, chimneys, steam pipes, etc. Research into the effective use of such unused thermal energy has been conducted for some time (see, for example, Patent Documents 1 and 2), but a large amount of thermal energy is still being released into the atmosphere, which is one of the causes of global warming and other issues.

[0003] Japanese Patent No. 5299324 Japanese Patent Application Laid-Open No. 2014-174027

[0004] To effectively utilize unused thermal energy from a heat source, a simulation approach based on basic information such as the heat receiving area and heat amount per unit area of ​​the high-temperature heat source to which a heat exchanger or the like is attached, the heat dissipation on the low-temperature heat source, and information on the heat exhaust system is effective. The most important factor in such simulations is the thermal conductance at the heat receiving point, which represents the thermal resistance of the heat source, and is necessary to measure and estimate the amount of heat received through the heat exchanger or the like in advance. However, the importance of thermal conductance in effectively utilizing unused thermal energy has been overlooked. The present invention was made in consideration of the above-mentioned problems, and its purpose is to understand the thermal conductance of heat sources and contribute to the effective utilization of unused thermal energy.

[0005] (Modes of the Invention) The following modes of the invention are intended to exemplify the configuration of the present invention and are described by item to facilitate understanding of the various configurations of the present invention. Each item does not limit the technical scope of the present invention. Therefore, while taking into consideration the best mode for carrying out the invention, even if some of the components of each item are replaced or deleted, or other components are added, they may also be included in the technical scope of the present invention.

[0006] (1) A method for measuring the thermal conductance of a heat source, comprising: connecting one end of a heat conduction path having a cooling source at the other end to the heat source; placing a heat generating element in the heat conduction path that can be controlled so that the amount of heat generated varies when a varying heating energy is applied; measuring the temperature in the heat conduction path to obtain a first temperature when the heat source is affected by the heat generated by the heat generating element and a second temperature when the heat source is not affected; and calculating the thermal conductance of the heat source based on the difference between the first temperature and the second temperature and the heating energy used when the first temperature was measured.

[0007] The thermal conductance measurement method described in this section measures the thermal conductance of a heat source having unused thermal energy that is being discarded. Specifically, a heat conduction path having a cooling source at one end is connected to the heat source at the other end, thereby diverting heat so that it flows from the heat source toward the cooling source. The heat conduction path used in this case is formed of a material whose properties, such as thermal conductivity, are known in advance. Furthermore, a heating element is installed in the heat conduction path, i.e., between one end of the heat conduction path where the cooling source is installed and the other end of the heat conduction path connected to the heat source. The installed heating element is one that can be controlled so that the amount of heat generated varies when a varying heating energy is applied. Here, the heat conduction path on which the heating element is installed in advance may be connected to the heat source.

[0008] Furthermore, the temperature in the heat conduction path configured as described above is measured to obtain a first temperature when the device is affected by heat generated by the heating element and a second temperature when the device is not affected by heat generated by the heating element. Here, the first temperature may be a temperature measured in the heat conduction path when the heating element is controlled to vary its heat output. Depending on the situation, the second temperature may be calculated from the first temperature measurement result to eliminate the influence of heat generated by the heating element, or may be a temperature measured in the heat conduction path when the heating element is not generating heat. Next, the difference between the first and second temperatures obtained as described above is calculated to extract temperature change data that varies due to the influence of the fluctuating heat generated by the heating element. The thermal conductance of the heat source is then calculated based on the extracted temperature change data and the heating energy applied to the heating element when the first temperature was measured.

[0009] Regarding the relationship between heat quantity and temperature, in a range where there is no phase change and the temperature changes only slightly, heat quantity is proportional to temperature, with mass and specific heat as constants. Therefore, considering that the addition of heating energy results in no change in mass or specific heat and an increase in temperature equal to the temperature change data, the "product of mass and specific heat" can be expressed as the value obtained by dividing the "heat quantity in a state where no heating energy is applied" by the "temperature in a state where no heating energy is applied (second temperature)" or the value obtained by dividing the "heat quantity in a state where heating energy is applied" by the "temperature in a state where heating energy is applied (first temperature)." Furthermore, the "product of mass and specific heat" can also be expressed as the value obtained by dividing the heating energy by the temperature change data, provided that radiation and thermal conduction, which cause errors, are so small that they can be ignored.

[0010] Furthermore, because thermal resistance is the temperature difference between two points divided by the heat flow rate (amount of heat flowing per unit time) between the two points, the temperature change data can be expressed as a value divided by the heating energy in the above relationship. Furthermore, since this thermal resistance includes all thermal resistances from the heat source to the heat conduction path, thermal conductance can be expressed as the reciprocal of thermal resistance, and considering the heat-receiving area of ​​the heat conduction path, it is clear that the thermal conductance per unit area can be calculated from the temperature change data and heating energy. This allows the thermal conductance of a heat source to be calculated based on the temperature change data caused by the heating element and the heating energy applied to the heating element at that time, without the need to know the specific heat or mass of the heat source. Knowing the thermal conductance in this way contributes to the effective utilization of unused thermal energy in the heat source. Moreover, thermal conductance can be determined even when internal information about the heat source, such as its specific heat, pressure, and physical density, is unknown, or even when the pressure and density fluctuate over time.

[0011] (2) A thermal conductance measurement method according to the above paragraph (1), which uses a Peltier element as the heating element, applies AC power as the heating energy at a predetermined frequency different from the fluctuating frequency of the heat flow from the heat source, extracts data on the frequency component of the predetermined frequency from the calculation result of the difference between the first temperature and the second temperature, and calculates the thermal conductance of the heat source based on the extraction result. The thermal conductance measurement method described in this paragraph uses a Peltier element as the heating element installed in the heat conduction path. Furthermore, by applying AC power of a predetermined frequency as the heating energy to the Peltier element, the amount of heat generated from the Peltier element fluctuates in an AC manner. The predetermined frequency of the AC power is set to a frequency different from the fluctuating frequency of the heat flow from the heat source to the heat conduction path.

[0012] Then, after calculating the difference between the first temperature when affected by heat generated by the heating element and the second temperature when not affected by heat generated by the heating element, data on the frequency component of the above-mentioned predetermined frequency is extracted from the calculation result.The thermal conductance of the heat source is calculated based on the temperature difference data extracted in this way and the AC power applied to the Peltier element.That is, by applying modulation power to the Peltier element at a frequency different from the fluctuation frequency of the heat flow from the heat source and extracting and using data on the frequency component of that modulation frequency, the thermal conductance is calculated while excluding the fluctuation component of the heat flow, etc.This allows the thermal conductance to be calculated more accurately.

[0013] (3) A thermal conductance measurement method according to the above (1) or (2), further comprising, when calculating the thermal conductance of the heat source, calculating a total thermal resistance from the heat source to the heat conduction path based on the difference between the first temperature and the second temperature and the heating energy when the first temperature is measured, and then calculating the thermal resistance inside the heat source based on the total thermal resistance. The thermal conductance measurement method described in this section measures the thermal resistance inside the heat source in addition to the thermal conductance of the heat source. As mentioned in the above (1), the thermal resistance calculated from the temperature change data (the difference between the first temperature and the second temperature) and the heating energy (the heating energy when the first temperature is measured) is the total thermal resistance including all the thermal resistances from the heat source to the heat conduction path. In other words, this total thermal resistance includes the thermal resistance inside the heat source, whose information such as specific heat, pressure, and physical density is unknown, the thermal resistance of the heat-receiving portion of the heat conduction path made of a material with known properties such as thermal conductivity, and the thermal resistance of the heat-conducting portion of the heat conduction path. Therefore, the thermal resistance inside the heat source is calculated based on the total thermal resistance as described above and the thermal resistance of the heat conduction path, which is known because it is made of a material with known thermal conductivity. As a result, even if the information inside the heat source is unknown, the thermal resistance inside the heat source can be determined from the calculated total thermal resistance and the known thermal resistance information.

[0014] (4) A system for measuring the thermal conductance of a heat source, comprising: a heat generating element that can be controlled to vary the amount of heat generated, sandwiched between two heat conducting media made of materials with known thermal conductivities; a heat conduction modulation unit that is installed so that heat is conducted from the heat source to one of the two heat conducting media; a cooling source that has a lower temperature than the heat source and is installed so that heat is conducted from the other of the two heat conducting media; a heat generating element control unit that controls the heat generating element by applying varying heating energy to the heat generating element; a temperature measurement unit that measures the temperature of a temperature measurement point set at a predetermined position on either or both of the two heat conducting media; and a calculation processing unit that performs calculation processing, wherein the calculation processing unit calculates, from the measurement results of the temperature measurement unit, a difference between a first temperature when affected by heat generated by the heat generating element and a second temperature when not affected, and calculates the thermal conductance of the heat source based on the difference and the heating energy when the first temperature was measured.

[0015] The thermal conductance measurement system described herein measures the thermal conductance per unit area of ​​a heat-receiving surface that can be extracted from a heat source having unused thermal energy. The system includes a thermal conductance modulation unit, a cooling source, a heating element control unit, a temperature measurement unit, and a calculation processing unit. The thermal conductance modulation unit has a configuration in which a heating element is sandwiched between two thermally conductive media, and the heating element is controllable so that its heat generation amount varies. The two thermally conductive media are formed of materials with known thermal conductivities. The thermal conductance modulation unit configured as described above is installed so that heat is conducted from the heat source to one of the two thermally conductive media. The cooling source has a lower temperature than the heat source to be measured and is installed so that heat is conducted from the other of the two thermally conductive media. In other words, the thermal conductance modulation unit and the cooling source are installed as part of a heat conduction path that shunts heat from the heat source so that heat flows from the heat source to the cooling source.

[0016] The heating element control unit controls the heating element of the thermal conduction modulation unit, providing the heating element with fluctuating heating energy to vary the amount of heat generated by the heating element. The temperature measurement unit measures the temperature at a temperature measurement point, which is set at a predetermined position on either or both of the two thermal conduction media of the thermal conduction modulation unit. The calculation processing unit performs various calculation processes in the system, including the following calculations. That is, the calculation processing unit obtains, from the measurement results of the temperature measurement points by the temperature measurement unit, a first temperature when affected by heat generated by the heating element and a second temperature when not affected by heat generated by the heating element, as described in section (1) above. Then, by calculating the difference between these values, temperature change data resulting from the influence of the fluctuating heat generated by the heating element is extracted.

[0017] Furthermore, the calculation processing unit calculates the thermal conductance of the heat source to be measured, as described in (1) above, based on the extracted temperature change data and the heating energy applied to the heat source by the heat source control unit when the temperature measurement unit measures the first temperature. This allows the thermal conductance of the heat receiving surface that can be collected from the heat source to be calculated without needing to know the specific heat or mass of the heat source. Furthermore, since the structure shunts heat from the heat source to be measured through a heat conduction path including a thermal conduction modulation unit and a cooling source and measures the temperature at the thermal conduction modulation unit in the heat conduction path, it is possible to measure heat sources in various environments, including heat sources that contain corrosive gases or gas-liquid mixtures with fluctuating medium densities. Furthermore, there is no need to consider durability, such as corrosion, and durability and reliability are significantly improved.

[0018] (5) A thermal conductance measurement system according to the above paragraph (4), wherein the heating element is a Peltier element, the heating element control unit applies, as the heating energy, AC power having a predetermined frequency different from a fluctuating frequency of the heat flow from the heat source, and the calculation processing unit extracts data on the frequency component of the predetermined frequency from the calculation result of the difference between the first temperature and the second temperature, and calculates the thermal conductance of the heat source based on the extraction result. In the thermal conductance measurement system described in this paragraph, the heating element of the thermal conductance modulation unit is a Peltier element, and the heating energy applied to this Peltier element by the heating element control unit is AC power having a predetermined frequency, so that the amount of heat generated from the Peltier element fluctuates in an AC manner. The predetermined frequency of the AC power in this case is set to a frequency different from the fluctuating frequency of the heat flow from the heat source to the thermal conductance modulation unit or the like.

[0019] The calculation processor then calculates the difference between the first temperature when the temperature is affected by heat generated by the heating element and the second temperature when the temperature is not affected by heat generated by the heating element, and extracts data on the frequency component of the above-mentioned predetermined frequency from the calculation result. Furthermore, the calculation processor calculates the thermal conductance of the heat source based on the extracted temperature difference data and the AC power applied to the Peltier element from the heating element control unit. That is, as mentioned in (2) above, by applying modulation power to the Peltier element at a frequency different from the fluctuation frequency of the heat flow from the heat source and extracting and using data on the frequency component of that modulation frequency, the thermal conductance is calculated while eliminating the fluctuation component of the heat flow. This allows the thermal conductance to be calculated more accurately.

[0020] (6) The thermal conductance measurement system according to (4), wherein at least three temperature measurement points are set in the one heat conduction medium at intervals along the direction of heat conduction from the heat source, and the calculation processing unit uses the temperatures measured at the at least three temperature measurement points by the temperature measurement unit and the intervals between the at least three temperature measurement points to determine whether the heat flow from the heat source is in a steady state, and calculates the thermal conductance of the heat source if it is determined that the heat flow is in a steady state. In the thermal conductance measurement system described in this paragraph, at least three temperature measurement points are set in one heat conduction medium, which is disposed on the heat source side of the two heat conduction media of the thermal conduction modulation unit. These at least three temperature measurement points are set in the one heat conduction medium at intervals along the direction of heat conduction from the heat source.

[0021] The calculation processor then uses the temperatures measured by the temperature measurement unit at the at least three temperature measurement points and the spacing between the at least three temperature measurement points to determine whether the heat flow from the heat source is in a steady state. That is, the temperatures measured at the at least three temperature measurement points, all set on one heat conduction medium, are considered to decrease linearly from the heat source side depending on the spacing between the temperature measurement points, provided that the heat flow from the heat source is in a steady state rather than a transient state. For example, if there are three temperature measurement points set at equal intervals, and the heat flow from the heat source is in a steady state, the temperature difference between the temperature measurement point on the heat source side and the central temperature measurement point is considered to be approximately equal to the temperature difference between the central temperature measurement point and the temperature measurement point on the cooling source side. Therefore, the calculation processor uses this relationship to determine whether the heat flow from the heat source is in a steady state, and calculates the thermal conductance if it is determined to be in a steady state. This prevents thermal conductance from being measured even when the heat flow from the heat source is in a transient state, and thermal conductance is measured only when the heat flow is in a steady state, thereby improving the reliability of thermal conductance measurements.

[0022] (7) The thermal conductance measurement system according to the above paragraph (4), wherein at least one temperature measurement point is set in the one heat conduction medium and at least one temperature measurement point is set in the other heat conduction medium, and the calculation processing unit determines whether the amount of heat passing through the thermal conduction modulation unit is normal based on the magnitude relationship between the temperature measured by the temperature measurement unit at the temperature measurement point of the one heat conduction medium and the temperature measured at the temperature measurement point of the other heat conduction medium, and calculates the thermal conductance of the heat source if the amount of heat passing through the thermal conduction modulation unit is normal. In the thermal conductance measurement system described in this paragraph, at least one temperature measurement point is set in one heat conduction medium of the two heat conduction media of the thermal conduction modulation unit that is to be arranged on the heat source side, and at least one temperature measurement point is set in the other heat conduction medium that is to be arranged on the cooling source side. The calculation processing unit then determines whether the amount of heat passing through the thermal conduction modulation unit is normal based on the magnitude relationship between the temperature measured by the temperature measurement unit at the temperature measurement point of one of the thermal conduction media and the temperature measured at the temperature measurement point of the other thermal conduction medium.

[0023] That is, if the amount of heat passing through the thermal conduction modulation unit is normal, the temperature measured at the temperature measurement point of one of the heat conduction media on the heat source side will be higher than the temperature measured at the temperature measurement point of the other heat conduction media on the cooling source side. On the other hand, if the amount of heat passing through the heat source is insufficient or if the influence of the heat source is transient, the temperature measured at the temperature measurement point of the other heat conduction media on the cooling source side will be higher than the temperature measured at the temperature measurement point of one of the heat conduction media on the heat source side. This temperature magnitude relationship also applies to the temperature measurement point closest to the heat source and the temperature measurement point closest to the cooling source when multiple temperature measurement points are set for one of the heat conduction media and the other heat conduction media. Therefore, the calculation processing unit uses this relationship to determine whether the amount of heat passing through the thermal conduction modulation unit is normal and, if determined to be normal, calculates the thermal conductance. This prevents thermal conductance from being measured even when the amount of heat passing through the thermal conduction modulation section is abnormal, and thermal conductance is measured only when the amount of heat passing through is normal, thereby improving the reliability of thermal conductance measurements.

[0024] (8) In the thermal conductance measurement system described in paragraphs (4) to (7), when calculating the thermal conductance of the heat source, the calculation processor further calculates a total thermal resistance from the heat source to the heat conduction path based on the difference between the first temperature and the second temperature and the heating energy when the first temperature was measured, and calculates the thermal resistance inside the heat source based on the total thermal resistance. In the thermal conductance measurement system described in this paragraph, the calculation processor calculates the thermal resistance inside the heat source in addition to the thermal conductance of the heat source. That is, as mentioned in paragraphs (1) and (3) above, the total thermal resistance calculated from the temperature change data and the heating energy includes the thermal resistance inside the heat source, the thermal resistance of the heat-receiving portion of the heat conduction path, and the thermal resistance of the heat-conducting portion of the heat conduction path. Therefore, using this, the calculation processor calculates the thermal resistance inside the heat source based on the total thermal resistance and the thermal resistance of the heat conduction path, which is known because it is made of a material with known thermal conductivity, etc. This allows the thermal resistance inside the heat source to be determined even if information about the inside of the heat source is unknown.

[0025] Since the present invention is configured as described above, it is possible to grasp the thermal conductance of the heat source and contribute to the effective use of unused thermal energy.

[0026] FIG. 1 is a block diagram showing an example of the configuration of a thermal conductance measurement system according to an embodiment of the present invention. FIG. 2 is an image diagram showing an example of the installation of a heat conduction path used in the thermal conductance measurement system according to an embodiment of the present invention, together with a model of the thermal resistance from a heat source to the heat conduction path. FIG. 3 shows an example of the structure of a thermal conductance modulation unit used in the thermal conductance measurement system according to an embodiment of the present invention, where (a) is a top view, (b) is a side view, (c) is a bottom view, and (d) is a cross-sectional view taken along the arrows A-A in (b). FIG. 4 is a flow chart showing an example of the procedure of a thermal conductance measurement method according to an embodiment of the present invention. (a) is a schematic diagram showing the relationship between heat quantity and temperature, and (b) is an excerpt showing the thermal conductance in the schematic diagram of (a).

[0027] Embodiments of the present invention will now be described with reference to the drawings. Here, identical or corresponding parts are designated by the same reference numerals throughout the drawings. Furthermore, detailed descriptions of parts identical or corresponding to those in the prior art will be omitted. FIG. 1 shows an example of the configuration of a thermal conductance measurement system 10 according to an embodiment of the present invention for measuring the thermal conductance at a heat-receiving surface that can be extracted from a heat source 50 (see FIG. 2 ) to be measured, as well as measuring the thermal resistance inside the heat source 50. As shown in the figure, the thermal conductance measurement system 10 includes a thermal conductance modulation unit 12, a cooling source 36, a heating element control unit 40, a temperature measurement unit 44, and a calculation processing unit 48. The thermal conductance modulation unit 12 includes a heating element 14 and two heat conduction media 16. FIG. 3 shows an example of the detailed structure of the thermal conductance modulation unit 12.

[0028] As shown in FIG. 3 , the thermal conduction modulation unit 12 has a configuration in which a heating element 14 is sandwiched between two heat conduction media 16. In this embodiment, two cylindrical heat conduction media 16 are connected by four bolts 24, with the heating element 14 disposed between them. The heating element 14 generates varying amounts of heat in response to varying heating energy. In this embodiment, the heating element 14 is formed by a Peltier element 14A, and a control line 32 is connected to supply power as heating energy to the Peltier element 14A. As can be seen in FIG. 3( d ), a heat dissipation sheet 28 is disposed between the Peltier element 14A and the two heat conduction media 16, thereby enhancing thermal conductivity. The opposing surfaces of the two heat conduction media 16 are provided with recesses for accommodating the heat dissipation sheet 28 and portions of the Peltier element 14A.

[0029] The two heat conduction media 16 are formed of a material with a known thermal conductivity, such as, but not limited to, aluminum or copper. Furthermore, one of the two heat conduction media 16, heat conduction medium 16A, has three measurement holes 20 drilled therein. In this embodiment, these three measurement holes 20 are equally spaced apart in the vertical direction in FIGS. 3(b) and 3(d) and extend toward the center of the heat conduction medium 16A, which is circular in plan view as shown in FIG. 3(a). Furthermore, temperature measurement points MP1 to MP3 are set in the three measurement holes 20 at positions near the center of the circular heat conduction medium 16A in plan view. Therefore, the three temperature measurement points MP1 to MP3 are equally spaced apart in the vertical direction in FIG. 3(d).

[0030] In contrast, one measurement hole 20 is drilled in the other of the two heat conduction media 16, the heat conduction medium 16B, and this measurement hole 20 extends toward the center of the heat conduction medium 16B, which is circular in bottom view as shown in FIG. 3( c). A temperature measurement point MP4 is also set in the measurement hole 20 of this heat conduction medium 16B, near the center of the circular heat conduction medium 16B in bottom view. That is, the temperature measurement points MP1 to MP4 are set near the heating element 14, sandwiching the heating element 14 between them. Due to the number of measurement holes 20 and temperature measurement points MP, the heat conduction medium 16A has a larger vertical width in FIGS. 3( b) and 3( d) than the other heat conduction medium 16B.

[0031] As shown in FIG. 2 , the thermal conduction modulation unit 12 configured as described above is used as part of a heat conduction path 54 that is installed to divert heat from the heat source 50 to be measured. In the embodiment shown in FIG. 2 , a heat exchanger is installed via a heat outlet from the heat source 50, and the thermal conduction modulation unit 12 is further installed there via a thermal junction member. The thermal conduction modulation unit 12 is installed so that heat from the heat source 50 is conducted to one of the heat conduction media 16A, in other words, so that one of the heat conduction media 16A is located on the upper side in FIG. 2 . Therefore, in the thermal conduction modulation unit 12, heat is conducted from the upper side to the lower side in FIGS. 3( b) and (d). The other heat conduction medium 16B of the thermal conduction modulation unit 12, which is located on the lower side in FIG. 2 , is connected to the cooling source 36 (also shown in FIG. 1) via a thermal junction member.

[0032] The cooling source 36 has a lower temperature than the heat source 50 to be measured, which generates a heat flow in which heat diverted from the heat source 50 flows toward the cooling source 36. For this reason, the right side of FIG. 2 illustrates a model evaluation circuit, which likens the heat flow to an electrical flow, from the V heat source to GND via multiple R resistors. As can be seen from this circuit, each component constituting the heat conduction path 54 through which heat flows has a thermal resistance. These thermal resistances can be determined by knowing the thermal conductivity of the materials constituting each component except for the heat source 50. The heat source 50 to be measured, as shown in FIG. 2, may be any component that contains unused thermal energy. Examples of such heat sources 50 include, but are not limited to, industrial plant equipment that handles thermal energy, various devices that use heat sources, combustion equipment, internal combustion engines, incinerators, flow paths for hot spring water, exhaust ducts, chimneys, steam pipes, and the like.

[0033] Returning to FIG. 1 , the heating element control unit 40 controls the heating element 14 of the thermal conduction modulation unit 12 by providing fluctuating heating energy to the heating element 14. In this embodiment, AC power (modulation power) of a predetermined frequency is supplied to the Peltier element 14A as heating energy via a control line 32 as shown in FIG. 3 . The predetermined frequency of the AC power is set to a frequency different from the fluctuating frequency of the heat flow from the heat source 50, which is previously determined. The temperature measurement unit 44 measures the temperature of the temperature measurement point MP set as described above in the thermal conduction medium 16 of the thermal conduction modulation unit 12. The temperature measurement unit 44 of this embodiment is configured to acquire the temperature of the temperature measurement point MP via, for example, a platinum Pt100 resistance temperature detector or a thermocouple, and measure the temperature at the temperature measurement point MP over a wide temperature range at high speed, although this is not limited thereto. The calculation processing unit 48 performs various arithmetic operations in the thermal conductance measurement system 10. Details of some of the calculation operations performed by the calculation processing unit 48 will be described later.

[0034] The thermal conductance measurement system 10 according to the embodiment of the present invention is not limited to the configuration shown in FIGS. 1 to 3 . Some of the components shown in FIGS. 1 to 3 may be omitted or replaced, or new components may be added. Furthermore, the components shown in FIG. 1 represent the functional divisions of the thermal conductance measurement system 10 and do not directly represent the individual devices constituting the thermal conductance measurement system 10. The system may be configured with various hardware, software, or a combination thereof. For example, the heating element 14 may be configured with something other than a Peltier element 14A, as long as it can be controlled to vary the amount of heat generated. Furthermore, the heat conduction path 54 may have a different configuration from that shown in FIG. 2 , as long as it includes the thermal conduction modulation unit 12 and the cooling source 36. Furthermore, the shape and number of components of the thermal conduction modulation unit 12 may differ from those in the embodiment shown in FIG. 3 , and the number and positions of the temperature measurement points MP may also be set arbitrarily.

[0035] Next, with reference to Fig. 4, a thermal conductance measurement method according to an embodiment of the present invention, which is executed using the above-described thermal conductance measurement system 10, will be described. For the configuration of the thermal conductance measurement system 10, please refer to Figs. 1 to 3 as appropriate. Note that the flowchart shown in Fig. 4 shows an example of the flow of steps in the thermal conductance measurement method, and the steps in the thermal conductance measurement method are not limited to this flowchart. Therefore, some of the steps shown in Fig. 4 may be changed, deleted, or rearranged, and new steps may be added.

[0036] S10 (connecting the heat conduction path): For example, as shown in FIG. 2 , the other end of a heat conduction path 54 having a cooling source 36 at one end and a thermal conduction modulation unit 12 at the middle is connected to the heat source 50 to be measured. At the same time, other components of the thermal conductance measurement system 10 are installed and connected. For example, the heat acquisition portion of the temperature measurement unit 44 is installed at a temperature measurement point MP set in the thermal conduction medium 16 of the thermal conduction modulation unit 12. S20 (controlling the heating element): The heating element control unit 40 starts controlling the heating element 14 of the thermal conduction modulation unit 12. That is, in this embodiment, AC power having a predetermined frequency (modulation frequency) different from the fluctuation frequency of the heat flow from the heat source 50 is supplied to the Peltier element 14A so that the current waveform becomes, for example, a sine wave.

[0037] S30 (Temperature Measurement): The temperature measurement unit 44 measures the temperature at the temperature measurement points MP set on the heat conduction medium 16. Specifically, the temperature is measured at temperature measurement points MP1 to MP3 set on one heat conduction medium 16A of the heat conduction modulation unit 12 and at temperature measurement point MP4 set on the other heat conduction medium 16B. Measurements are made at a sampling interval at least twice the modulation frequency of the AC power supplied from the heating element control unit 40 to the Peltier element 14A. Furthermore, for subsequent processing, the measured analog temperature data is converted to digital temperature data by the calculation processing unit 48 or a separately provided A / D converter. It is preferable to perform this A / D conversion with as high a resolution as possible. The temperature measured in this step corresponds to the first temperature (see symbol TW in FIG. 5A) when the temperature is affected (modulated) by the heat generated by the heating element 14.

[0038] S40 (state determination): The calculation processing unit 48 determines whether the heat flow from the heat source 50 is in a steady state and whether the amount of heat passing through the thermal conduction modulation unit 12 is normal. First, to explain the heat flow determination, the calculation processing unit 48 determines the heat flow using the temperatures measured at the three temperature measurement points MP1-MP3 of one of the heat conduction media 16A and the spacing between these three temperature measurement points MP1-MP3. Specifically, if the heat flow from the heat source 50 is in a steady state, it is assumed that the heat flow from the heat source 50 side to the cooling source 36 side decreases linearly. Therefore, in this embodiment, in which the three temperature measurement points MP1-MP3 are set at equal intervals, it is assumed that the temperature difference between the temperature measurement point MP1 on the heat source 50 side of the heat conduction medium 16A and the central temperature measurement point MP2 is approximately equal to the temperature difference between the central temperature measurement point MP2 on the heat conduction medium 16A and the temperature measurement point MP3 on the cooling source 36 side. On the other hand, if the heat flow from the heat source 50 is in a transient state, the above relationship breaks down, and an event occurs in which the temperature difference between the temperature measurement points MP1 and MP3 divided by 2 is not equal to the temperature difference between the temperature measurement points MP1 and MP2 or the temperature difference between the temperature measurement points MP2 and MP3. Using this, the calculation processing unit 48 determines whether the heat flow from the heat source 50 is in a steady state. Even if four or more temperature measurement points MP are set on one of the heat conduction media 16A, the heat flow can be determined using the above relationship.

[0039] Next, the determination of the amount of heat will be explained. The calculation processing unit 48 determines the amount of heat based on the magnitude relationship between the temperatures measured at three temperature measurement points MP1 to MP3 of one heat conduction medium 16A and the temperature measured at temperature measurement point MP4 of the other heat conduction medium 16B. Specifically, if the amount of heat passing through the thermal conduction modulation unit 12 is normal, it is assumed that the temperature gradually decreases from the heat source 50 side toward the cooling source 36 side. For this reason, in this embodiment, it is assumed that the measured temperatures at temperature measurement points MP1, MP2, MP3, and MP4, which are lined up along the temperature transfer direction from the heat source 50 side to the cooling source 36 side, are arranged in descending order.

[0040] On the other hand, if the heat quantity is abnormal due to excessive modulation by the heating element 14 (Peltier element 14A), the above relationship is disrupted, resulting in, for example, the temperatures at temperature measurement points MP1 to MP3 becoming approximately equal or lower than the temperature at temperature measurement point MP4. Using this information, the calculation processing unit 48 determines whether the heat quantity passing through the thermal conduction modulation unit 12 is normal. Even if two or fewer or four or more temperature measurement points MP are set on one thermal conduction medium 16A, or even if two or more temperature measurement points MP are set on the other thermal conduction medium 16B, the heat quantity can be determined using the above relationship. If it is determined in step S40 that the heat flow from the heat source 50 is in a steady state and the heat quantity passing through the thermal conduction modulation unit 12 is normal, the process proceeds to the next step. If a transient state of the heat flow or an abnormality in the heat quantity is detected, the configuration of the heat conduction path 54, the measurement timing, the AC power supplied to the Peltier element 14A, and other factors are reviewed.

[0041] S50 (Calculate Average Temperature): The calculation processor 48 calculates the average temperature of the temperatures measured in S30. In this embodiment, AC power is applied to the Peltier element 14A to vary the heat generation. Therefore, the influence (modulation) of temperature fluctuations by the Peltier element 14A causes the temperature to fluctuate up and down in an AC manner. Therefore, by calculating the average temperature using, for example, a moving average, temperature data is extracted that eliminates the influence of temperature fluctuations by the Peltier element 14A. This processing is performed using a low-pass filter or other filter with filter characteristics that eliminate fluctuations due to modulation. This calculation of the average temperature is performed for each temperature measurement point MP, or for only a specific temperature measurement point MP. Subsequent processing is performed using the data at the temperature measurement point MP where the average temperature was calculated in this step. The temperature calculated in this step corresponds to the second temperature (see symbol T0 in FIG. 5A) when there is no influence from heat generation by the heating element 14 (unmodulated state).

[0042] S60 (Difference Calculation): The calculation processing unit 48 calculates the difference between the temperature (first temperature) measured in S30 and the average temperature (second temperature) calculated in S50. This extracts temperature change data (see the symbol ΔT in FIG. 5A) that varies due to the influence (modulation) of temperature fluctuations caused by the Peltier element 14A. S70 (Frequency Component Extraction): The calculation processing unit 48 extracts frequency component data of the frequency (modulation frequency) of the AC power applied to the Peltier element 14A from the temperature change data calculated in S60. This eliminates noise, such as fluctuation components of the heat flow from the heat source 50. Examples of extraction methods include using a low-pass filter to extract only data near the modulation frequency, using a band-pass filter centered on the modulation frequency, performing synchronous detection (baseband detection), and performing two-stage shift detection using baseband detection or multiple PSN modulators, but detailed descriptions of these methods will be omitted here.

[0043] S80 (calculation of thermal conductance): The calculation processing unit 48 calculates the thermal conductance of the heat source 50 to be measured. Here, FIG. 5A shows a schematic diagram of the relationship between the amount of heat (unit: J) and the temperature (unit: K), where m denotes the mass of the heat source 50, c denotes the specific heat of the heat source 50, TW denotes the temperature in the modulated state (first temperature), T0 denotes the temperature in the unmodulated state (second temperature), Q0 denotes the original amount of heat of the heat source 50, and QW denotes the amount of heat added with the heat generated by the heating element 14. That is, within a range of slight temperature change without phase change, the amount of heat is proportional to the temperature with the mass m and specific heat c as constants, resulting in the relationship shown in FIG. 5A, which can be expressed by the following equation: Q0(J) = m c T0(K) QW(J) = m c TW(K) Furthermore, Figure 5(a) shows the relationship of the following formula, where W (unit: J) is the heating energy applied to the Peltier element 14A during modulation, and ΔT is the difference between the temperature TW in the modulated state and the temperature TO in the unmodulated state, and shows that the temperature has increased by ΔT due to the addition of the heating energy W: QW(J) = Q0(J) + W(J)

[0044] From the above relationships, the following equations hold: m⋅c = Q0(J) / T0(K) = QW(J) / TW(K) Furthermore, the following equations hold for the temperature change ΔT occurring in response to the heating energy W: m⋅c = W(J) / ΔT(K) From these equations, the following relationships hold: Q0(J) / T0(K) = W(J) / ΔT(K) Q0(J) = T0(K) / ΔT(K)⋅W(J) However, because this equation does not include the thermal resistance ratios within the heat conduction path 54 shown in FIG. 2, it is necessary to take modulation efficiency into account. Furthermore, since the heating energy W applied to the Peltier element 14A during modulation is actually modulation power (AC power), the symbol P (unit: W) is used to represent modulation efficiency. Taking into account the conversion between the heating energy W (J) and the modulation power P (W), the following equations are obtained: Q0(J) = T0(K) / ΔT(K) P(W) η(%) This equation shows that the heat quantity possessed by the heat source 50 can be estimated using only the temperature information that changes due to modulation, and that if the modulation power P and modulation efficiency η are values ​​specific to the thermal conductance measurement system 10, then the only unknown quantity is the thermal resistance of the heat source 50, and therefore the thermal conductance of the heat source 50 can be estimated based on this equation.

[0045] Here, thermal resistance is the temperature difference between two points divided by the heat flow rate (amount of heat per unit time) flowing between the two points, and is therefore shown as the slope of the graph represented by "m·c" in FIG. 5(a) (see symbol θ in FIG. 5(b)). Therefore, if thermal resistance is designated as Rth, it can be calculated using the following formula: Rth (°C / W) = ΔT (K) / W (J). Since this thermal resistance Rth includes all thermal resistances within the heat conduction path 54 shown on the right side of FIG. 2, if the unknown thermal resistance of the heat source 50 is designated as Rrs and the thermal resistance present in the measurement system is designated as Rse, the thermal resistance Rrs of the heat source 50 can be found as follows: Rrs (°C / W) = Rth (°C / W) - Rse (°C / W)

[0046] Furthermore, as a general-purpose unit, thermal conductance, excluding the heat-receiving area of ​​the heat conduction path 54 relative to the heat source 50, is expressed as the reciprocal of thermal resistance. That is, "tan θ" in FIG. 5B corresponds to the thermal conductance of the heat-receiving surface in contact with the heat source 50. The calculation processing unit 48 calculates the thermal conductance of the heat source 50 in this manner. It is important to handle heat values ​​that also include the modulation efficiency η. Note that the modulation power P (W) shown here is a value specific to the measurement system. Since heat quantity is defined as the amount of heat per unit time, if the modulation power P can be adjusted and converted to 1 (J), the value of ΔT can be used as is. Therefore, by appropriately adjusting the ratio with the modulation power P, the calculation formula can be simplified, further reducing the load on the microcomputer and other components of the calculation processing unit 48.

[0047] S90 (calculate thermal resistance): The calculation processing unit 48 calculates the thermal resistance inside the heat source 50 to be measured. As mentioned in S80 above, the thermal resistance Rth (°C / W) including all thermal resistances in the heat conduction path 54 shown on the right side of FIG. 2 is calculated as a combined resistance value corresponding to the following formula: Rth (°C / W) = (R heat source + R bonding material + R device) × (R device + R bonding material + R cooling source) ÷ ((R heat source + R bonding material + R device) + (R device + R bonding material + R cooling source)) This is the thermal resistance calculated from the temperature measurement point MP, and Kirchhoff's first law and second law (Ohm's law) used in electrical circuit networks can be applied to the thermal resistance. This Rth is the parallel connection of the series thermal resistances on the heat source side, i.e., the sum of the R heat source + the thermal resistance of the R bonding material on the heat source side + the R device on the heat source side, and the sum of the R cold heat source + the R bonding material on the cold heat source side + the R device on the cold heat source side. This is the parallel resistance calculation formula for the electrical circuits R1 and R2. Rth can be calculated as R = (R1 x R2) / (R1 + R2). However, the thermal resistance of the modulation device R device is added to both the heat source side and the cold heat source side, and the ratio is device-specific, but here it is shown as a common value. Of the thermal resistances that make up the thermal resistance Rth described above, all but the R heat source are known by the thermal conductivity of the materials that make up each. Therefore, the calculation processing unit 48 uses these values ​​to calculate the thermal resistance (R heat source) inside the heat source 50.

[0048] In this case, if the thermal conductivity and geometry of the heat exchanger connected to the heat source 50 and the thermal interface material that conducts heat from there are measured in advance, and the heat flow is diverted to form a heat flow circuit as shown in Figure 2, the only unknown thermal resistance is the thermal resistance within the heat source 50. In other words, the thermal resistance within the heat source 50 can be calculated without determining the physical properties required to calculate the thermal energy of the material that transfers heat within the above-mentioned equipment, such as the industrial plant equipment mentioned as an example of the heat source 50. Furthermore, the thermal resistance value R of the cooling source 36 can be treated as close to zero when a function that maintains a constant cooling side temperature, such as a circulator, is used, thereby further simplifying the calculation formula. Furthermore, if the thermal interface material connected to the heat exchanger on the heat source 50 side and the thermal interface material connected to the cooling source 36 have the same shape and the thermal resistance value (R interface material) of each is the same, the calculation is further simplified.

[0049] Furthermore, when determining the thermal resistance of a known value, it is necessary to estimate the temperature of the V heat source based on the temperature information measured at the temperature measurement point MP, taking into account the characteristics of the heat exchanger and thermal conduction modulation unit 12, which have a temperature function. In other words, because the temperature of the heat outlet where the V heat source heat exchanger is attached is generally not measured, the thermal resistance of a known material with the above temperature characteristics must be estimated from the temperature information at the temperature measurement point MP. For this estimation, an electrical circuit serving as an equivalent model evaluation circuit, shown on the right side of Figure 2, is used. For example, temperature information observed at temperature measurement points MP1 to MP4 of the thermal conduction modulation unit 12 is implemented in an electrical circuit simulator. A simulation is then performed to simulate the transient phenomenon in which the V heat source fluctuates from 0 volts to a predetermined voltage, and a parametric analysis is performed on the observed changes at the temperature measurement points MP1 to MP4 and the temperature function of the heat exchanger and thermal conduction modulation unit 12, which have a temperature coefficient. Next, a thermal resistance value table with an appropriate temperature function is adopted as a method for matching the temperature fluctuations observed at the temperature measurement point MP with the results of a simulation performed on a circuit simulator using the V heat source as the circuit power supply voltage. As a result, even if the temperature of the heat exchanger's heat outlet is not measured, the temperature changes at the temperature measurement points MP1 to MP4 are used to calculate the thermal resistance inside the heat source 50 regardless of the temperature of the heat source 50.

[0050] The embodiment of the present invention having the above-described configuration can achieve the following effects. Specifically, a thermal conductance measurement method according to the embodiment of the present invention uses a system 10, such as that shown in FIGS. 1 to 3, to measure the thermal conductance of a heat source 50 having unused thermal energy that is being exhausted. Specifically, a heat conduction path 54 having a cooling source 36 at one end is connected to the heat source 50 at the other end, thereby diverting heat so that it flows from the heat source 50 toward the cooling source 36 (see S10 in FIG. 4). The heat conduction path 54 used in this case is formed of a material whose properties, such as thermal conductivity, are known in advance. Furthermore, a heating element 14 is installed in the heat conduction path 54, i.e., between one end of the heat conduction path 54 where the cooling source 36 is installed and the other end of the heat conduction path 54 connected to the heat source 50. The heating element 14 to be installed can be controlled so that the amount of heat generated varies when a varying amount of heating energy W is applied.

[0051] Furthermore, the temperature in the heat conduction path 54 configured as described above is measured to obtain a first temperature TW when the heat conduction path 54 is affected by the heat generated by the heating element 14 and a second temperature TO when the heat conduction path 54 is not affected by the heat generated by the heating element 14 (see S30 and S50 in FIG. 4 and FIG. 5A). Next, the difference ΔT between the obtained first temperature TW and second temperature TO is calculated to extract temperature change data ΔT that has changed due to the influence of the fluctuating heat generated by the heating element 14 (see S60 in FIG. 4 and FIG. 5A). Then, the thermal conductance of the heat source 50 is calculated based on the extracted temperature change data ΔT and the heating energy W applied to the heating element 14 when the first temperature TW was measured.

[0052] 5(a), the "product of mass and specific heat" m·c can be expressed as the value obtained by dividing the "amount of heat in a state where no heating energy is applied" Q0 by the "temperature in a state where no heating energy is applied (second temperature)" T0, or the value obtained by dividing the "amount of heat in a state where heating energy is applied" QW by the "temperature in a state where heating energy is applied (first temperature)" TW. Furthermore, the "product of mass and specific heat" m·c can also be expressed as the value obtained by dividing the heating energy W by the temperature change data ΔT, if the heat conduction that generates radiation and errors is so small that it can be ignored.

[0053] Furthermore, because thermal resistance is the temperature difference between two points divided by the heat flow rate (amount of heat flowing per unit time) between the two points, the above relationship can be expressed as the temperature change data ΔT divided by the heating energy W. Furthermore, considering that this thermal resistance includes all thermal resistances from the heat source 50 to the heat conduction path 54, that thermal conductance can be expressed as the reciprocal of thermal resistance, and the heat-receiving area of ​​the heat conduction path 54, it is clear that the thermal conductance per unit area can be calculated from the temperature change data ΔT and the heating energy W (see S80 in FIG. 4 ). This allows the thermal conductance of the heat source 50 to be calculated based on the temperature change data ΔT changed by the influence of the heating element 14 and the heating energy W applied to the heating element 14 at that time, without needing to know the specific heat c or mass m of the heat source 50. Knowing the thermal conductance in this way contributes to the effective utilization of unused thermal energy in the heat source 50. Furthermore, the thermal conductance can be determined even when information inside the heat source 50, such as the specific heat c, pressure, and physical density of the heat source 50, is unknown, or even when the pressure and density of the heat source 50 fluctuate over time.

[0054] The thermal conductance measurement method according to the embodiment of the present invention utilizes a Peltier element 14A as the heating element 14 installed in the heat conduction path 54. The heating energy W applied to the Peltier element 14A is AC power (modulated power) P of a predetermined frequency, which causes the amount of heat generated by the Peltier element 14A to fluctuate in an AC manner. The predetermined frequency of the AC power P is set to a frequency different from the fluctuating frequency of the heat flow from the heat source 50 to the heat conduction path 54. After calculating the difference ΔT between the first temperature TW when affected by the heat generated by the heating element 14 and the second temperature TO when not affected by the heat generated by the heating element 14, data on the frequency component of the predetermined frequency is extracted from the calculation result (see S70 in FIG. 4 ). The thermal conductance of the heat source 50 is calculated based on the extracted temperature difference data and the AC power P applied to the Peltier element 14A. That is, by applying modulated power P to the Peltier element 14A with a frequency different from the fluctuation frequency of the heat flow from the heat source 50 and extracting and using data on the frequency component of that modulated frequency, it is possible to calculate the thermal conductance while eliminating the fluctuation component of the heat flow, etc. This makes it possible to calculate the thermal conductance with greater accuracy.

[0055] Additionally, the thermal conductance measurement method according to the embodiment of the present invention measures the thermal resistance inside the heat source 50 in addition to the thermal conductance of the heat source 50. As described above, the thermal resistance calculated from the temperature change data ΔT (the difference between the first temperature TW and the second temperature TO) and the heating energy W (the heating energy used to measure the first temperature TW) is the total thermal resistance including all the thermal resistances from the heat source 50 to the heat conduction path 54. That is, this total thermal resistance includes the thermal resistance inside the heat source 50, whose information such as specific heat, pressure, and physical density is unknown, the thermal resistance of the heat-receiving portion of the heat conduction path 54, which is made of a material with known properties such as thermal conductivity, and the thermal resistance of the heat-conducting portion of the heat conduction path 54. Therefore, the thermal resistance inside the heat source 50 can be calculated based on the total thermal resistance and the thermal resistance of the heat conduction path 54, which is made of a material with known properties such as thermal conductivity. As a result, even if the information about the inside of the heat source 50 is unknown, it is possible to grasp the thermal resistance as information about the inside of the heat source 50 from the calculated total thermal resistance and the known thermal resistance information.

[0056] On the other hand, a thermal conductance measurement system 10 according to an embodiment of the present invention measures the thermal conductance per unit area of ​​a heat-receiving surface that can be extracted from a heat source 50 having unused thermal energy. As shown in FIG. 1 , the thermal conductance measurement system 10 includes a thermal conduction modulation unit 12, a cooling source 36, a heating element control unit 40, a temperature measurement unit 44, and a calculation processing unit 48. As also shown in FIG. 3 , the thermal conduction modulation unit 12 has a configuration in which a heating element 14 is sandwiched between two heat conduction media 16. The heating element 14 is controllable so that its heat generation amount varies, and the two heat conduction media 16 are formed of materials with known thermal conductivities. The thermal conduction modulation unit 12 having such a configuration is installed so that heat is conducted from the heat source 50 to one of the two heat conduction media 16, heat conduction medium 16A. The cooling source 36 has a lower temperature than the heat source 50 to be measured, and is installed so that heat is conducted from the other of the two heat conduction media 16, heat conduction medium 16B. That is, as shown in FIG. 2, the thermal conduction modulation unit 12 and the cooling source 36 are installed as part of a heat conduction path 54 that diverts heat from the heat source 50 so that heat flows from the heat source 50 toward the cooling source 36.

[0057] The heating element control unit 40 controls the heating element 14 of the thermal conduction modulation unit 12, applying fluctuating heating energy W to the heating element 14 to vary the amount of heat generated by the heating element 14. The temperature measurement unit 44 measures the temperature at a temperature measurement point MP, which is set at a predetermined position on one or both of the two thermal conduction media 16A and 16B of the thermal conduction modulation unit 12, as shown in FIG. 3(d). The calculation processing unit 48 performs various calculation processes in the system 10, and as part of these processes, performs the following calculations. That is, from the measurement results of the temperature measurement point MP by the temperature measurement unit 44, the calculation processing unit 48 obtains a first temperature TW when affected by the heat generated by the heating element 14 and a second temperature TO when not affected by the heat generated by the heating element 14, as described in the thermal conductance measurement method. Then, the calculation processing unit 48 calculates the difference ΔT between these values ​​to extract temperature change data ΔT caused by the fluctuating heat generated by the heating element 14.

[0058] Furthermore, the calculation processing unit 48 calculates the thermal conductance of the heat source 50 to be measured, as described in the thermal conductance measurement method, based on the extracted temperature change data ΔT and the heating energy W applied to the heating element 14 by the heating element control unit 40 when the temperature measurement unit 44 measures the first temperature TW. This makes it possible to calculate the thermal conductance at the heat-receiving surface that can be sampled from the heat source 50 without having to know the specific heat c or mass m of the heat source 50. Moreover, because the structure shunts heat from the heat source 50 to be measured through the heat conduction path 54 including the thermal conduction modulation unit 12 and the cooling source 36 and measures the temperature at the thermal conduction modulation unit 12 in the heat conduction path 54, it is possible to measure heat sources 50 in various environments, including heat sources 50 through which corrosive gases and gas-liquid mixtures with fluctuating medium densities flow. Furthermore, there is no need to consider durability, such as corrosion, and durability and reliability can be significantly improved.

[0059] Furthermore, in the thermal conductance measurement system 10 according to the embodiment of the present invention, the heating element 14 of the thermal conduction modulation unit 12 is a Peltier element 14A, and the heating energy W provided to this Peltier element 14A by the heating element control unit 40 is AC power P of a predetermined frequency, so that the amount of heat generated by the Peltier element 14A fluctuates in an AC manner. The predetermined frequency of the AC power P is set to a frequency that is different from the fluctuating frequency of the heat flow flowing from the heat source 50 to the thermal conduction modulation unit 12, etc. Then, the calculation processing unit 48 calculates the difference ΔT between the first temperature TW when affected by the heat generated by the heating element 14 and the second temperature T0 when not affected by the heat generated by the heating element 14, and then extracts data of the frequency component of the above-mentioned predetermined frequency from the calculation result.

[0060] Furthermore, the calculation processing unit 48 calculates the thermal conductance of the heat source 50 based on the temperature difference data ΔT extracted in this manner and the AC power P applied to the Peltier element 14A by the heating element control unit 40. That is, as mentioned in the thermal conductance measurement method, by applying to the Peltier element 14A a modulated power P with a frequency different from the fluctuation frequency of the heat flow from the heat source 50 and extracting and using data on the frequency component of that modulated frequency, it is possible to calculate the thermal conductance while excluding the fluctuation component of the heat flow, etc. This makes it possible to calculate the thermal conductance with greater accuracy.

[0061] 3, in the thermal conductance measurement system 10 according to the embodiment of the present invention, three temperature measurement points MP1 to MP3 are set in one of the two heat conduction media 16 of the heat conduction modulation unit 12, heat conduction medium 16A, which is disposed on the heat source 50 side. These three temperature measurement points MP1 to MP3 are set at intervals in one heat conduction medium 16A along the conduction direction of heat flowing from the heat source 50 (the up and down direction in FIG. 3(d)). The calculation processing unit 48 then uses the temperatures measured by the temperature measurement unit 44 at these three temperature measurement points MP1 to MP3 and the intervals between these three temperature measurement points MP1 to MP3 to determine whether the heat flow from the heat source 50 is in a steady state (see S40 in FIG. 4). In other words, the temperatures measured at the three temperature measurement points MP1 to MP3 set on one of the heat conduction media 16A are considered to decrease linearly from the heat source 50 side depending on the spacing between the temperature measurement points MP1 to MP3, provided that the heat flow from the heat source 50 is in a steady state rather than a transient state.

[0062] For example, in the embodiment shown in Figure 3, when three temperature measurement points MP1 to MP3 are set at equal intervals, it is considered that, if the heat flow from the heat source 50 is in a steady state, the temperature difference between the temperature measurement point MP1 on the heat source 50 side and the central temperature measurement point MP2 will be approximately equal to the temperature difference between the central temperature measurement point MP2 and the temperature measurement point MP3 on the cooling source 36 side. Therefore, the calculation processing unit 48 uses this relationship to determine whether the heat flow from the heat source 50 is in a steady state, and calculates the thermal conductance if it is determined to be in a steady state. This prevents the thermal conductance from being measured even when the heat flow from the heat source 50 is in a transient state, and allows the thermal conductance to be measured only when the heat flow is in a steady state, thereby improving the reliability of the thermal conductance measurement.

[0063] Furthermore, in the thermal conductance measurement system 10 according to the embodiment of the present invention, one temperature measurement point MP4 is set on the other of the two heat conduction media 16 of the thermal conduction modulation unit 12, the other heat conduction medium 16B, which is located closer to the cooling source 36. The calculation processing unit 48 then determines whether the amount of heat passing through the thermal conduction modulation unit 12 is normal based on the magnitude relationship between the temperatures measured by the temperature measurement unit 44 at the temperature measurement points MP1 to MP3 on one heat conduction medium 16A and the temperature measured at the temperature measurement point MP4 on the other heat conduction medium 16B (see S40 in FIG. 4). That is, if the amount of heat passing through the thermal conduction modulation unit 12 is normal, the temperatures measured at the temperature measurement points MP1 to MP3 on the one heat conduction medium 16A closer to the heat source 50 will be higher than the temperature measured at the temperature measurement point MP4 on the other heat conduction medium 16B closer to the cooling source 36.

[0064] On the other hand, if the amount of heat passing through from the heat source 50 is insufficient or if the influence of the heat-generating body 14 is transient, it is expected that the temperature measured at the temperature measurement point MP4 on the other heat conduction medium 16B on the cooling source 36 side will be higher than the temperature measured at the temperature measurement points MP1 to MP3 on the other heat conduction medium 16A on the heat source 50 side. This temperature magnitude relationship also applies to the three temperature measurement points MP1 to MP3 set on one heat conduction medium 16A. Therefore, the calculation processing unit 48 uses this relationship to determine whether the amount of heat passing through the thermal conduction modulation unit 12 is normal and calculates the thermal conductance if it is determined to be normal. This prevents the thermal conductance from being measured even when the amount of heat passing through the thermal conduction modulation unit 12 is abnormal, and allows the thermal conductance to be measured only when the amount of heat passing is normal, thereby improving the reliability of the thermal conductance measurement.

[0065] Furthermore, the thermal conductance measurement system 10 according to the embodiment of the present invention calculates the thermal resistance inside the heat source 50 in addition to the thermal conductance of the heat source 50 using the calculation processing unit 48. That is, as mentioned in the thermal conductance measurement method according to the embodiment of the present invention, the total thermal resistance calculated from the temperature change data ΔT and the heating energy W includes the thermal resistance inside the heat source 50, the thermal resistance of the heat-receiving portion of the heat conduction path 54, and the thermal resistance of the heat-conducting portion of the heat conduction path 54. Therefore, using this, the calculation processing unit 48 can calculate the thermal resistance inside the heat source 50 based on the total thermal resistance as described above and the thermal resistance of the heat conduction path 54, which is known because it is made of a material with known thermal conductivity, etc. This makes it possible to determine the thermal resistance inside the heat source 50 even if information about the inside of the heat source 50 is unknown.

[0066] More specifically, it is common to represent the heat conduction circuit shown in Figure 2, which shows the total thermal resistance, as a thermal circuit network, and then to represent the thermal circuit network as an electrical circuit network. For example, a model is created by replacing thermal resistance with electrical resistance and applying Kirchhoff's first and second laws, and then calculating the balance of heat at each junction by substituting Kirchhoff's first law. Using this calculation method, the thermal resistance of the heat receiving part, the thermal resistance of the heat conducting part, the thermal resistance of the thermoelectric modulator 12, and the thermal resistance of the cold heat source 36 can be determined in advance. This narrows the unknown thermal resistance to the thermal resistance within the heat source 50 as seen from the heat receiving part. Therefore, by utilizing Kirchhoff's theorem and the recently developed electronic circuit simulators and their inverse analysis tools, it is possible to identify the unknown part, i.e., calculate the thermal resistance within the heat source 50.

[0067] Going further, the thermal resistance can be considered a scalar quantity specific to the heat source 50, which can be captured as an instantaneous value from the thermal conductance measurement system 10. The ability to accurately measure this scalar quantity within the heat source 50 means that installing multiple thermal conductance measurement systems 10 along the same heat source 50 path allows for accurate measurement of the thermal resistance value within the heat source 50 at measurement points with different positional information. Therefore, by further extending Kirchhoff's law, these multiple measurement points can be set, for example, between two points separated by a certain distance, and the thermal resistance value within the heat source 50 can be determined at each point. This allows for the construction of a heat flow circuit equivalent to a Wheatstone bridge in an electrical circuit as the heat flow paths between the two points, and the unknown thermal resistance connecting the two points in the Wheatstone bridge in an electrical circuit can also be determined. Because this unknown thermal resistance represents the internal thermal resistance connecting two points along the heat flow path, the range of applications is expanded, making it possible to measure the thermal resistance value of a heat medium between installed heat flow paths.

[0068] Furthermore, by calculating the internal thermal resistance value not only as a scalar quantity but also as a vector quantity, and capturing the frequency fluctuation that occurs when the thermal fluctuation frequency propagates between two points at the other end, the movement speed of the medium that generates the heat flux between these two points can also be grasped. This is because the time difference in the heat flow fluctuation between the two points is considered to be a mutual temperature fluctuation, the second temperature change mentioned above is considered to be a frequency change, and by capturing the phase change, the heat medium movement speed between these two points can be considered to be indirectly measured, making it possible to calculate the heat medium movement speed within the heat source 50.

[0069] Furthermore, the ability to accurately measure the thermal resistance value inside the heat source 50 indicates that it is possible to grasp the amount of recoverable heat when reusing surplus heat from the heat source 50. In other words, since the thermal potential of the heat source 50 can be actually measured, it is also possible to build a system that measures the amount of recoverable heat that can be reused from the heat source 50 being measured by setting a usable temperature range.

[0070] 10: thermal conductance measurement system, 12: thermal conduction modulation unit, 14: heating element, 14A: Peltier element, 16 (16A, 16B): thermal conduction medium, MP (MP1 to MP4): temperature measurement point, 36: cooling source, 40: heating element control unit, 44: temperature measurement unit, 48: calculation processing unit, 50: heat source, 54: thermal conduction path, W: heating energy, P: AC power (modulated power), TW: first temperature (temperature in modulated state), T0: second temperature (temperature in unmodulated state), ΔT: difference between first temperature and second temperature (temperature change data)

Claims

1. A method for measuring the thermal conductance of a heat source, comprising: connecting one end of a heat conduction path having a cooling source at the other end to the heat source; placing a heating element in the heat conduction path that can be controlled so that the amount of heat generated varies when a varying heating energy is applied; measuring the temperature in the heat conduction path to obtain a first temperature when the heat source is affected by the heat generated by the heating element and a second temperature when the heat source is not affected; and calculating the thermal conductance of the heat source based on the difference between the first temperature and the second temperature and the heating energy when the first temperature was measured.

2. A thermal conductance measuring method according to claim 1, characterized in that a Peltier element is used as the heating element, AC power of a predetermined frequency different from a fluctuating frequency of the heat flow from the heat source is applied as the heating energy, data of a frequency component of the predetermined frequency is extracted from a calculation result of a difference between the first temperature and the second temperature, and the thermal conductance of the heat source is calculated based on the extraction result.

3. A thermal conductance measurement method as described in claim 1 or 2, characterized in that when calculating the thermal conductance of the heat source, a total thermal resistance from the heat source to the heat conduction path is calculated based on the difference between the first temperature and the second temperature and the heating energy when the first temperature is measured, and the thermal resistance inside the heat source is calculated based on the total thermal resistance.

4. A system for measuring the thermal conductance of a heat source, comprising: a heat generating element that can be controlled to vary the amount of heat generated, sandwiched between two thermally conductive media made of materials with known thermal conductivity, a thermal conduction modulation unit that is installed so that heat is conducted from the heat source to one of the two thermally conductive media; a cooling source that has a lower temperature than the heat source and is installed so that heat is conducted from the other of the two thermally conductive media; a heat generating element control unit that controls the heat generating element by providing varying heating energy to the heat generating element; a temperature measurement unit that measures the temperature of a temperature measurement point set at a predetermined position on both or either of the two thermally conductive media; and a calculation processing unit that performs calculation processing, wherein the calculation processing unit calculates, from the measurement results of the temperature measurement unit, a difference between a first temperature when affected by heat generated by the heat generating element and a second temperature when not affected, and calculates the thermal conductance of the heat source based on the difference and the heating energy when the first temperature was measured.

5. The thermal conductance measurement system according to claim 4, characterized in that the heating element is a Peltier element, the heating element control unit applies AC power of a predetermined frequency different from a fluctuating frequency of the heat flow from the heat source as the heating energy, and the calculation processing unit extracts data of a frequency component of the predetermined frequency from a calculation result of the difference between the first temperature and the second temperature, and calculates the thermal conductance of the heat source based on the extraction result.

6. The thermal conductance measurement system of claim 4, wherein at least three of the temperature measurement points are set on the one of the thermal conduction media at intervals along the direction of heat conduction from the heat source, and the calculation processing unit uses the temperatures measured at the at least three temperature measurement points by the temperature measurement unit and the intervals between the at least three temperature measurement points to determine whether the heat flow from the heat source is in a steady state or not, and calculates the thermal conductance of the heat source when it is determined that the heat flow is in a steady state.

7. The thermal conductance measurement system according to claim 4, characterized in that at least one of the temperature measurement points is set in one of the thermal conduction media and at least one of the temperature measurement points is set in the other of the thermal conduction media, and the calculation processing unit determines whether the amount of heat passing through the thermal conduction modulation unit is normal or not based on the magnitude relationship between the temperature measured by the temperature measurement unit at the temperature measurement point of one of the thermal conduction media and the temperature measured at the temperature measurement point of the other of the thermal conduction medium, and calculates the thermal conductance of the heat source if it is determined to be normal.

8. A thermal conductance measurement system as described in any one of claims 4 to 7, characterized in that when calculating the thermal conductance of the heat source, the calculation processing unit further calculates a total thermal resistance from the heat source to the heat conduction path based on the difference between the first temperature and the second temperature and the heating energy when the first temperature is measured, and calculates the thermal resistance inside the heat source based on the total thermal resistance.

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