Method for evaluating heat transfer, and apparatus for evaluating heat transfer

Abstract

The present invention provides a heat transfer evaluation method and a heat transfer evaluation apparatus that can accurately and easily determine the degree of heat transfer. [Solution] The heat transfer evaluation method comprises: a first step of heating or cooling a test piece Tp by bringing a fluid F into contact with a part of the test piece Tp; a second step of performing convection of air for a predetermined time in a closed space 10L formed on the other side of the test piece Tp; a third step of measuring the temperature inside the closed space 10L; and a fourth step of comparing the temperature when using a test piece Tp1 that has not been treated on the other side with the temperature when using a test piece Tp that has been treated on the other side.

Description

Technical Field

[0001] The present disclosure relates to a method for evaluating heat transfer and a heat transfer evaluation device.

Background Art

[0002] Patent Document 1 discloses a method for measuring the heat transfer coefficient in a metal fin covered with an oxide film containing carbon nanotubes. Here, the heat transfer coefficient is a parameter indicating the degree of ease of heat transfer (the degree of heat transfer) through the contact surface between two objects (for example, a solid and a fluid). It is known that the magnitude of the heat transfer coefficient does not depend on the material of the object. Also, it is known that the magnitude of the heat transfer coefficient increases as the momentum of the fluid flow along the contact surface increases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, when mass-producing fins like those shown in Patent Document 1, it is necessary to inspect whether samples taken from the mass-produced products meet the required quality standards to perform quality control on the mass-produced products. For fins used in heat exchangers like those shown in Patent Document 1, it is conceivable that checking whether the heat transfer coefficient falls within a predetermined range could be one of the quality control items. However, as mentioned above, the heat transfer coefficient does not depend on the material and therefore does not need to be controlled, so there are no commercially available evaluators, and no method has been established for easy evaluation during mass production. Even the evaluation device that performs the heat transfer coefficient measurement method disclosed in Figure 7 of Patent Document 1 is a device that can perform evaluation relatively easily, but the measurement results of the heat transfer coefficient vary due to human factors in the installation, such as variations in the thickness of the thermal conductive grease applied between the test piece and the stainless steel block in which the heater is installed, or air entering between the test piece and the stainless steel block. Therefore, it is not a method for easy evaluation during mass production. Furthermore, the evaluation apparatus for performing the heat transfer coefficient measurement method disclosed in Figure 8 of Patent Document 1 is an apparatus that uses test pieces that are difficult to manufacture, as they must be made solely for evaluation purposes. Therefore, it cannot be used for quality control during mass production, where samples must be taken from mass-produced products. Thus, the inventors of the present application have found through their research that if a method is created that can improve the heat transfer coefficient, the above-mentioned problem of being unable to perform quality control during mass production will arise.

[0005] This disclosure is made based on the circumstances described above, and aims to provide a heat transfer evaluation method and a heat transfer evaluation apparatus that can accurately and easily grasp the degree of heat transfer. [Means for solving the problem]

[0006] The heat transfer evaluation method of the first disclosure is: A first step involves bringing a fluid into contact with a portion of the test specimen to heat or cool the test specimen, A second step involves performing air convection for a predetermined time within a closed space formed on the other side of the test specimen, A third step involves measuring the temperature inside the enclosed space, A fourth step involves comparing the temperature when using the test specimen without processing the other side with the temperature when using the test specimen with the other side processed. It is equipped with.

[0007] The heat transfer evaluation device of the second disclosure is A closed space that is closed by attaching the test specimen, A fluid flow space through which fluid flows so as to be in contact with the surface of the test specimen opposite to the closed space, A temperature detection unit for detecting the temperature inside the enclosed space, It is equipped with.

[0008] This configuration allows for the detection of temperature within a closed space while minimizing the influence of the external environment on the enclosed space.

[0009] Therefore, the degree of heat transfer can be accurately and easily determined. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the heat transfer evaluation device of Embodiment 1. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a schematic diagram showing a test specimen. [Figure 4] This is a schematic diagram showing the processing unit. [Figure 5] This graph shows an example of the change in the magnitude of the load current density applied to a substrate attached to a processing device. [Figure 6] This is a schematic diagram of a graph showing the temperature change in a closed space when a test specimen is attached to a heat transfer evaluation device. [Figure 7] This graph shows the temperature change in a closed space when test specimens under different conditions are attached to a heat transfer evaluation device. [Modes for carrying out the invention]

[0011] A preferred embodiment in the present disclosure will be described.

[0012] In the heat transfer evaluation method of the first disclosure, the fluid can be a liquid. In this case, compared with the case of using a gas for the fluid, it is possible to improve the accuracy of heating or cooling of the test piece.

[0013] In the heat transfer evaluation method of the first disclosure, the measured temperature can be the average value of the temperatures at a plurality of positions in the closed space. In this case, a measured temperature that rounds off the variations at the positions in the closed space can be obtained.

[0014] In the heat transfer evaluation apparatus of the second disclosure, the test piece can be attached from either above or below the closed space, and the temperature detection unit can be arranged on the side away from the test piece in the closed space. In this case, the temperature of the air in a state where heat exchange is evenly performed between the air in the closed space and the test piece can be adopted as the measured temperature.

[0015] In the heat transfer evaluation apparatus of the second disclosure, a plurality of temperature detection units can be provided in the closed space and arranged at different positions in the closed space from each other. In this case, a measured temperature that rounds off the variations at the positions in the closed space can be obtained.

[0016] <Embodiment 1> Embodiment 1 in which the heat transfer evaluation apparatus 10 according to the present disclosure is embodied will be described with reference to FIGS. 1 to 7. In the following description, the vertical direction in the heat transfer evaluation apparatus 10 is represented using the Z-axis shown in FIG. 1. The positive direction on the Z-axis is taken as the upward direction.

[0017] [Configuration of Heat Transfer Evaluation Apparatus] As shown in FIGS. 1 and 2, the heat transfer evaluation apparatus 10 of Embodiment 1 includes a fluid circulation unit 10A, a closed space formation unit 10B, a plurality of temperature detection units 10C, a plurality of external temperature detection units 10D (see FIG. 2), a chiller 10E (see FIG. 1), and an arithmetic unit 10F (see FIG. 2).

[0018] The fluid flow section 10A is made of, for example, synthetic resin. The fluid flow section 10A is cylindrical in shape. A fluid flow space 10G is formed in the fluid flow section 10A. The fluid flow space 10G is formed as a downward recess on the upper end surface of the fluid flow section 10A. The fluid flow space 10G is cylindrical in shape and is formed concentrically with respect to the fluid flow section 10A. The fluid flow section 10A is provided with an inlet passage 10H and an outlet passage 10J. Specifically, the inlet passage 10H and the outlet passage 10J are provided protruding from the lower end surface of the fluid flow section 10A and are in communication with the fluid flow space 10G.

[0019] An annular recess 10K is formed on the upper end surface of the fluid flow section 10A, surrounding the fluid flow space 10G. An O-ring 10S is fitted into the recess 10K so as to protrude slightly upward.

[0020] The closed space forming section 10B is made of, for example, synthetic resin. The closed space forming section 10B is cylindrical in shape. A closed space 10L is formed in the closed space forming section 10B. The closed space 10L is formed as an upward recess on the lower end surface of the closed space forming section 10B. The closed space 10L is cylindrical in shape and is formed concentrically with respect to the closed space forming section 10B. The inner diameter of the closed space 10L is the same as the inner diameter of the fluid flow space 10G. Multiple through holes 10M are formed radially through the outer circumferential surface of the closed space forming section 10B (see Figure 2). Each through hole 10M communicates with the upper end of the inner circumferential surface of the closed space 10L (see Figure 1). Each through hole 10M is evenly distributed in the circumferential direction with respect to the inner circumferential surface of the closed space 10L (see Figure 2). The vertical position of each through hole 10M is the same (see Figure 1).

[0021] Multiple temperature sensing units 10C may use, for example, known thermocouples. A wire W is connected to each temperature sensing unit 10C. Each temperature sensing unit 10C is located within a closed space 10L, and the wire W is led out to the outside through each through-hole 10M. Each temperature sensing unit 10C is located between the inner circumferential surface of the closed space 10L and the center Ca, and is positioned on a virtual circumference Vc concentric with the closed space 10L (see Figure 2). Each temperature sensing unit 10C is located at a different position within the closed space 10L. The temperature sensing units 10C detect the temperature within the closed space 10L.

[0022] Multiple external temperature sensing units 10D use known thermocouples or the like, similar to those used in the temperature sensing unit 10C. A wire W is connected to each external temperature sensing unit 10D. Each external temperature sensing unit 10D is positioned such that the wire W is held by a holding part 10N provided on the outer circumferential surface of the closed space forming unit 10B, and is exposed above the holding part 10N (see Figure 2). The holding parts 10N are evenly distributed in the circumferential direction with respect to the outer circumferential surface of the closed space forming unit 10B (see Figure 2).

[0023] A known type of chiller 10E is used. The chiller 10E has a storage section 10P for storing fluid F inside, and the storage section 10P is connected to an inlet passage 10H and an outlet passage 10J. Three-way valves Tb1 and Tb2 are provided in the middle of the inlet passage 10H and the outlet passage 10J, and a bypass passage Cp is provided between the three-way valves Tb1 and Tb2. For example, water or oil can be used as the fluid F. In other words, the fluid F is a liquid. For example, a heater (not shown) is provided in the storage section 10P. For example, the state of the three-way valves Tb1 and Tb2 is operated so that the storage section 10P and the bypass passage Cp are in communication and the fluid F does not flow into the fluid flow space 10G, and the fluid F stored in the storage section 10P is heated to a predetermined temperature by the heater. The fluid F is sent to the inlet passage 10H by a pump (not shown) installed in the chiller 10E, and returns to the storage section 10P via the bypass passage Cp and the outlet passage 10J. In other words, the fluid F circulates in the order of storage section 10P, inlet passage 10H, bypass passage Cp, and outlet passage 10J. When the fluid F has been heated to a predetermined temperature, the state of the three-way valves Tb1 and Tb2 is changed so that the storage section 10P and the fluid flow space 10G are in communication, and the fluid F does not flow into the bypass passage Cp. This allows the fluid F, heated to a predetermined temperature, to flow into the fluid flow space 10G.

[0024] The calculation unit 10F is configured as a control circuit, for example, consisting of a microcomputer. As shown in Figure 2, the calculation unit 10F is connected to the wires W of each temperature detection unit 10C and the wires W of each external temperature detection unit 10D. The calculation unit 10F receives voltage values ​​corresponding to the temperature of the air inside the closed space 10L from each temperature detection unit 10C and voltage values ​​corresponding to the temperature of the outside air from each external temperature detection unit 10D as measured values ​​Mv1 and Mv2 via the wires W. Based on these measured values ​​Mv1 and Mv2, the calculation unit 10F determines the temperature of the air inside the closed space 10L and the temperature of the outside air. The heat transfer evaluation device 10 is configured in this way.

[0025] [Composition of the test specimen] As shown in Figure 3, the test specimen Tp has a base material B formed into a flat plate by rolling a metal such as aluminum or copper, and a carbon nanotube-containing oxide film Fo covering one side of the base material B. The outer shape of the test specimen Tp is a perfect square (see Figure 2). The carbon nanotube-containing oxide film Fo is formed in a film form by containing carbon nanotubes in a metal oxide obtained by oxidizing the same type of metal as the base material B. The carbon nanotube-containing oxide film Fo has countless thread-like filaments Fi extending from it. The material of the thread-like filaments Fi is the same as the metal oxide that forms the carbon nanotube-containing oxide film Fo. The other side of the base material B, which is part of the base material B, does not have the carbon nanotube-containing oxide film Fo formed on it, and the other side of the plate is exposed. The thickness of the carbon nanotube-containing oxide film Fo is approximately 30 nm to 1500 nm. The thickness of the test specimen Tp is, for example, approximately 0.05 mm to 0.5 mm.

[0026] [An example of a method for forming a carbon nanotube-containing oxide film on a substrate] First, substrate B is immersed in 99.5% pure ethanol and ultrasonically cleaned for 5 minutes. Next, the dried substrate B is attached to the processing apparatus P shown in Figure 4. Specifically, the processing apparatus P has a processing tank Pt and a current supply unit Cs. Processing liquid Pl is stored in the processing tank Pt.

[0027] For example, treatment solution Pl is prepared by adding sodium hydroxide, a 0.2% carbon nanotube dispersion, and a conductivity modifier to purified water. For example, the concentration of sodium hydroxide in treatment solution Pl is 1.7 g / L. For example, the concentration of carbon nanotube dispersion in treatment solution Pl is 1.64 ml / L. For example, the concentration of conductivity modifier in treatment solution Pl is 0.44 g / L. The temperature of treatment solution Pl is room temperature (20°C to 30°C).

[0028] The current supply unit Cs includes a pair of electrodes E1 and E2, a first conductive path Cp1 provided between the pair of electrodes E1 and E2, a pair of power supplies Ps1 and Ps2, a second conductive path Cp2 connecting the pair of power supplies Ps1 and Ps2 in series, and a switching unit Sw. The pair of electrodes E1 and E2 are made of, for example, a flat plate made of stainless steel alloy (SUS304). For example, each electrode E1 and E2 is immersed in a processing liquid Pl stored in a processing tank Pt with its plate surface parallel to each other and spaced a predetermined distance apart, with its plate thickness direction oriented horizontally (left-right direction in Figure 4). The upper ends of each electrode E1 and E2 protrude from the processing liquid Pl.

[0029] The first conductive path Cp1 is positioned so as not to come into contact with the processing liquid Pl. The first conductive path Cp1 is electrically connected to each of the upper ends of the electrodes E1 and E2 that protrude from the processing liquid Pl.

[0030] Known DC power supplies are used for the pair of power supplies Ps1 and Ps2. The pair of power supplies Ps1 and Ps2 are arranged so as not to come into contact with the processing liquid Pl and the first conductive path Cp1. For example, the power supplies Ps1 and Ps2 are designed to allow adjustment of the magnitude of the output current.

[0031] The second conductive path Cp2 is positioned so as not to come into contact with the processing liquid Pl and the first conductive path Cp1. The second conductive path Cp2 is electrically connected to the positive terminal of power supply Ps1 and the negative terminal of power supply Ps2.

[0032] For example, a known double-throw switch is used for the switching unit Sw. The switching unit Sw is located in the center of the first conductive path Cp1, between the negative terminal of power supply Ps1 and the positive terminal of power supply Ps2. A movable contact Mc is provided in the switching unit Sw. The movable contact Mc can change between a first conductive state in which the negative terminal of power supply Ps1 and the first conductive path Cp1 are connected, a second conductive state in which the positive terminal of power supply Ps2 and the first conductive path Cp1 are connected, and a non-conductive state in which neither power supply Ps1 nor Ps2 are connected to the first conductive path Cp1. In this way, the processing unit P is configured.

[0033] Substrate B is electrically connected to the center of the second conductive path Cp2, immersed in the processing liquid Pl stored in the processing tank Pt, and positioned between the pair of electrodes E1 and E2. The plate surface of substrate B is positioned directly opposite the plate surfaces of each electrode E1 and E2. In this way, substrate B is attached to the processing apparatus P.

[0034] Next, the switching unit Sw is switched to a first conductive state, a second conductive state, and a non-conductive state at predetermined timings. Specifically, the case where current flows in the direction of arrow A shown in Figure 4 is defined as the + direction. Then, the switching unit Sw is switched to allow current to flow through the substrate B in the pattern shown in Figure 5.

[0035] Next, substrate B is removed from the processing apparatus P and immersed in purified water for ultrasonic cleaning for 5 minutes. Then, the oxide on the surface of substrate B is hydrated by immersing it in 98°C hot water for 15 minutes. Finally, substrate B is dried by blowing air onto it. In this way, a test specimen Tp is prepared in which a carbon nanotube-containing oxide film Fo is formed on one side of substrate B (see Figure 3).

[0036] [An example of the procedure for attaching test specimens to the heat transfer evaluation device] First, the test specimen Tp is placed on the fluid flow section 10A so as to block the fluid flow space 10G from above. Specifically, the test specimen Tp is placed on the fluid flow section 10A such that each of its four sides is in contact with the four positioning pins 10Q that protrude upward from the upper end surface of the fluid flow section 10A. At this time, the entire upper end of the O-ring 10S that protrudes upward from the recess 10K is tightly in contact in an annular shape with the plate surface of the test specimen Tp on the side where the carbon nanotube-containing oxide film Fo is not formed.

[0037] Next, the closed space forming section 10B is attached. Specifically, the open end of the closed space 10L is positioned opposite the upper surface of the test piece Tp (the surface on which the carbon nanotube-containing oxide film Fo is formed), and the closed space forming section 10B is placed on the fluid flow section 10A so as to cover the test piece Tp from above. For example, multiple insertion holes 10R corresponding to each positioning pin 10Q are formed on the lower end surface of the closed space forming section 10B (see Figure 1). By inserting each positioning pin 10Q into each insertion hole 10R, the closed space forming section 10B and the fluid flow section 10A are positioned coaxially (see Figure 1). Then, the closed space forming section 10B and the fluid flow section 10A are fixed together with multiple bolts Bo and nuts Nu (see Figure 1). As a result, the O-ring 10S is pressed against the test piece Tp and comes into close contact with the lower surface of the test piece Tp. The open end of the closed space 10L is then closed by the upper surface (other side) of the test specimen Tp. The carbon nanotube-containing oxide film Fo faces the closed space 10L. In this way, the closed space forming section 10B and the fluid flow section 10A maintain a state in which the test specimen Tp is held from above and below. The closed space 10L is closed by attaching the test specimen Tp from below the closed space 10L. The temperature sensing section 10C is located on the side of the closed space 10L away from the test specimen Tp.

[0038] A heat transfer evaluation device 10 with a test specimen Tp attached is placed in a constant temperature bath (not shown). A known constant temperature bath is used. The temperature in the constant temperature bath is set to a predetermined temperature (for example, about 20°C) and the constant temperature bath is operated. The state of the three-way valves Tb1 and Tb2 is set so that the storage section 10P and the bypass passage Cp are in communication, and the fluid F does not flow into the fluid flow space 10G, and the operation of the chiller 10E is started. Then, the fluid F circulates between the storage section 10P and the bypass passage Cp while being heated by a heater (not shown). When the fluid F has been heated to a predetermined temperature, the state of the three-way valves Tb1 and Tb2 is set so that the storage section 10P and the fluid flow space 10G are in communication, and the fluid F does not flow into the bypass passage Cp. As a result, the fluid F heated to a predetermined temperature flows into the fluid flow space 10G. For example, the predetermined temperature of the fluid F is 85°C. The fluid F flows through the fluid flow space 10G so as to be in contact with the surface of the test specimen Tp opposite to the closed space 10L.

[0039] When fluid F flows into the fluid flow space 10G, the air within the fluid flow space 10G is pushed out by the fluid F. As a result, the fluid F comes into even contact with the underside of the specimen Tp that closes the fluid flow space 10G, and the heat of the fluid F is transferred to the specimen Tp. Then, the heat from the specimen Tp is transferred to the air in the closed space 10L, and natural convection occurs in the air within the closed space 10L. Here, natural convection is the flow of air caused by temperature variations in the air within the closed space 10L. If the state of natural convection is maintained for a predetermined time, the temperature of the air in the closed space 10L asymptotically approaches a temperature T1 that is lower than the temperature of the fluid F (85°C) (see Figure 6). Temperature T1 is the asymptotic temperature of the specimen Tp.

[0040] Here, a larger asymptotic temperature T1 means that more heat was transferred from the specimen Tp to the air in the enclosed space of 10L. Conversely, a smaller asymptotic temperature T1 means that heat transfer from the specimen Tp to the air in the enclosed space of 10L was inactive. In other words, based on the magnitude of the asymptotic temperature T1, we can understand the degree of heat transfer in the specimen Tp and estimate the magnitude of the heat transfer coefficient in the specimen Tp.

[0041] Figure 7 shows the results of measuring the temperature change of air in a closed space 10L by attaching test specimen Tp and test specimens Tp1, Tp2, and Tp3, which are under different conditions than test specimen Tp, to the heat transfer evaluation device 10. Test specimen Tp is a sample in which a carbon nanotube-containing oxide film Fo is formed on one side of an aluminum plate (the other side). The graph for test specimen Tp is shown by a solid black line. Test specimen Tp1 is a sample of an aluminum plate in the as-rolled state (i.e., one side and the other side are untreated). The graph for test specimen Tp1 is shown by a dark gray dotted line. Test specimen Tp2 is a sample of a copper plate in the as-rolled state (i.e., one side and the other side are untreated). The graph for test specimen Tp2 is shown by a dark gray solid line. Test specimen Tp3 is a sample in which one side of an aluminum plate (the other side) is anodized. The graph for test specimen Tp3 is shown by a light gray solid line.

[0042] Each graph in Figure 7 plots the average value of the measured value Mv1 input from multiple temperature sensing units 10C. T3 represents the temperature outside the heat transfer evaluation device 10, and plots the average value of the measured value Mv2 input from multiple external temperature sensing units 10D. T3 was measured simultaneously when measuring the temperature change of the air in the closed space 10L for each test specimen (Tp, Tp1, Tp2, Tp3). In reality, T3 was obtained as a measurement result corresponding to each test specimen (Tp, Tp1, Tp2, Tp3). However, since all of them were approximately 20°C from the start to the end of the measurement, only one T3 is plotted in Figure 7.

[0043] The sdr (surface area ratio: an index indicating the increased area due to irregularities) on the side of test specimen Tp where the carbon nanotube-containing oxide film Fo was formed (the other side) was 150, and the emissivity was 0.82. The sdr on the side of test specimen Tp3 where the anodized treatment was applied (the other side) was 198, and the emissivity was 0.84. In other words, the degree of irregularities and surface area on the plate surface of test specimen Tp3 are greater than those on the plate surface of test specimen Tp. The emissivity of test specimen Tp3 is almost the same as that of test specimen Tp. Furthermore, the sdr of test specimens Tp1 and Tp2 is 0.8, and the emissivity is 0.06.

[0044] As shown in Figure 7, the graphs for test specimens Tp1, Tp2, and Tp3 largely overlap, and their asymptotic temperatures T2 were all approximately 33.6°C. In contrast, the asymptotic temperature T1 in the graph for test specimen Tp was clearly larger than the asymptotic temperatures T2 in the graphs for test specimens Tp1, Tp2, and Tp3, at 34.5°C. From the results of the graphs for test specimens Tp1 and Tp2, it can be seen that, as is common sense in physics, the degree of heat transfer does not depend on the difference in material. From the results of the graphs for test specimens Tp and Tp3, it can be seen that, similarly, as is common sense in physics, the degree of heat transfer does not depend on the difference in surface area due to minute irregularities or on emissivity. In other words, the asymptotic temperature T1 in the graph of test specimen Tp was greater than the asymptotic temperature T2 in the graphs of test specimens Tp1, Tp2, and Tp3, which is thought to be due to the treatment of forming a carbon nanotube-containing oxide film Fo on the other side (i.e., the degree of heat transfer (heat transfer coefficient) increased), and this is correctly reflected in the evaluation.

[0045] Here, Equation 1 shows the formula representing the improvement rate Ru of heat transfer of test specimen Tp relative to test specimens Tp1, Tp2, and Tp3. T1 is the asymptotic temperature in the graph of test specimen Tp, T2 is the asymptotic temperature in the graphs of test specimens Tp1, Tp2, and Tp3, and T3 is the temperature outside the heat transfer evaluation device 10.

[0046]

number

[0047] For example, when mass-producing a product that has undergone a process to form a carbon nanotube-containing oxide film Fo similar to that of test specimen Tp, a sample taken from the mass-produced product is attached to the heat transfer evaluation device 10 to measure the asymptotic temperature T1. Then, the improvement rate Ru is determined using the asymptotic temperature T1 of this sample, the previously measured asymptotic temperature T2, and the external temperature T3 of the heat transfer evaluation device 10. By confirming whether the determined improvement rate Ru falls within a range that is above a predetermined lower limit and below a predetermined upper limit, product quality control can be performed. In other words, the heat transfer evaluation device 10 can perform quality control by estimating the magnitude of the heat transfer coefficient in test specimen Tp by understanding the degree of heat transfer in test specimen Tp.

[0048] [An example of a procedure for evaluating heat transfer in a test specimen] First, the test specimen Tp is held from above and below by the closed space forming section 10B and the fluid flow section 10A, and the heat transfer evaluation device 10 with the test specimen Tp attached is placed in a constant temperature bath (not shown). The temperature in the constant temperature bath is set to a predetermined temperature (for example, about 20°C), and the constant temperature bath is operated. Then, the state of the three-way valves Tb1 and Tb2 is set so that the storage section 10P and the bypass passage Cp are in communication, and fluid F does not flow into the fluid flow space 10G, and the operation of the chiller 10E is started. Fluid F circulates between the storage section 10P and the bypass passage Cp while being heated by the heater. This state is maintained until the fluid F is heated to a predetermined temperature (85°C).

[0049] Next, the first step is performed, in which fluid F is brought into contact with a portion of the test specimen Tp to heat the specimen Tp. Specifically, the state of the three-way valves Tb1 and Tb2 is set so that when the fluid F is heated to a predetermined temperature, the storage section 10P and the fluid flow space 10G are connected, and fluid F does not flow into the bypass passage Cp. As a result, the fluid F heated to a predetermined temperature flows into the fluid flow space 10G. The inflow of fluid F into the fluid flow space 10G begins at approximately 100 seconds in Figure 7. At this time, the air in the fluid flow space 10G is pushed out by the fluid F, the fluid flow space 10G is filled with fluid F, and the fluid F comes into even contact with the lower surface of the test specimen Tp that closes the fluid flow space 10G. Then, the heat of the fluid F is transferred to the test specimen Tp.

[0050] Next, a second step is performed in which air convection is carried out for a predetermined time in a closed space 10L formed on the other side of the test specimen Tp. Specifically, heat transfer from the fluid F to the test specimen Tp is continued by continuing the operation of the chiller 10E. In the second step, natural convection occurs in the air within the closed space 10L as the heat from the test specimen Tp is transferred to the air within the closed space 10L. After a predetermined time has elapsed, the temperature of the air within the closed space 10L asymptotically approaches an asymptotic temperature T1 that is lower than the temperature of the fluid F (see Figure 7).

[0051] Next, a third step is performed to measure the temperature inside the closed space 10L. Specifically, after the second step is performed for a time when it can be considered that the temperature has asymptotically approached the asymptotic temperature T1 (approximately 4600 seconds after the start of fluid F inflow into the fluid flow space 10G), the temperature of the air inside the closed space 10L is measured for a predetermined time by multiple temperature detection units 10C. For example, in Embodiment 1, the calculation unit 10F repeats the measurement 100 times every second (i.e., for 100 seconds), starting from approximately 4600 seconds after the start of fluid F inflow into the fluid flow space 10G. Specifically, the calculation unit 10F calculates the average value of the measured values ​​Mv1 input from each temperature detection unit 10C 100 times and stores it as a group of average values. Then, the calculation unit 10F calculates the average value in the group of average values ​​and adopts the average value in the group of average values ​​as the asymptotic temperature T1 of the air inside the closed space 10L. In other words, the temperature inside a 10L enclosed space is the average value of the temperatures measured at multiple locations within that space.

[0052] Next, a fourth step is performed to compare the temperature when using test specimen Tp1, which has not been treated on other sides, with the temperature when using test specimen Tp, which has been treated on other sides. Specifically, multiple specimens Tp1, Tp2, and Tp3 are prepared in advance, and the asymptotic temperature T2 (see Figure 7) of the air in the closed space 10L with each test specimen Tp1, Tp2, and Tp3 installed is measured using the heat transfer evaluation device 10, and the average value and standard deviation of each asymptotic temperature T2 are calculated. The method for calculating each asymptotic temperature T2 is the same as the procedure for calculating the asymptotic temperature T1 of test specimen Tp. The standard deviation was approximately 0.2°C. In addition, the calculation unit 10F calculates the average value Mv2 measured from multiple external temperature detection units 10D as the external temperature T3 of the heat transfer evaluation device 10 (see Figure 7).

[0053] The calculation unit 10F then calculates the heat transfer improvement rate Ru in the test specimen Tp according to the formula shown in Equation 1. The improvement rate Ru is obtained by subtracting the temperature outside the heat transfer evaluation device 10 T3 from the asymptotic temperature T1 in the test specimen Tp, and dividing that value by subtracting the temperature outside the heat transfer evaluation device 10 T3 from the asymptotic temperature T2 in the test specimens Tp1, Tp2, and Tp3. This is done by comparing the temperature (asymptotic temperature T2) when using test specimens Tp1, Tp2, and Tp3 that have not been treated on one side (one side), with the temperature (asymptotic temperature T1) when using test specimen Tp that has been treated on one side (one side). In this way, the calculation unit 10F grasps the degree of heat transfer in the test specimen Tp.

[0054] As described above, the heat transfer evaluation method of Embodiment 1 comprises a first step of heating or cooling the test piece Tp by bringing a fluid F into contact with a part of the test piece Tp; a second step of performing air convection for a predetermined time in a closed space 10L formed on the other side of the test piece Tp; a third step of measuring the temperature inside the closed space 10L; and a fourth step of comparing the temperature when using a test piece Tp1 that has not been treated on the other side with the temperature when using a test piece Tp that has been treated on the other side. Therefore, it is possible to detect the temperature inside the closed space 10L while suppressing the influence of the external environment on the inside of the closed space 10L.

[0055] Therefore, the degree of heat transfer can be measured accurately and easily.

[0056] In the heat transfer evaluation method, the fluid F is a liquid. Therefore, compared to the case where a gas is used for fluid F, it is possible to improve the accuracy of heating the test specimen Tp.

[0057] In the heat transfer evaluation method, temperature is the average value of measured temperatures at multiple locations within a closed space of 10L. Therefore, it is possible to obtain a temperature that rounds off the variations at different locations within the closed space of 10L.

[0058] The heat transfer evaluation device 10 includes a closed space 10L that is closed when a test piece Tp is attached, a fluid flow space 10G through which fluid F flows so as to be in contact with the surface of the test piece Tp opposite to the closed space 10L, and a temperature detection unit 10C that detects the temperature inside the closed space 10L. Therefore, it is possible to detect the temperature inside the closed space 10L while suppressing the influence of the external environment on the inside of the closed space 10L.

[0059] Therefore, the heat transfer coefficient can be measured accurately and easily.

[0060] In the heat transfer evaluation device 10, the test specimen Tp is mounted from below in the closed space 10L, and the temperature sensing unit 10C is positioned on the side of the closed space 10L away from the test specimen. Therefore, it is possible to measure the temperature of the air in the closed space 10L after heat has been evenly exchanged between the air and the test specimen Tp.

[0061] In the heat transfer evaluation device 10, multiple temperature detection units 10C are provided within the closed space 10L, and are positioned at different locations within the closed space 10L. Therefore, it is possible to obtain a measured temperature that rounds off variations in position within the closed space 10L.

[0062] This disclosure is not limited to the embodiments described above and in the drawings, and the technical scope of this disclosure also includes, for example, the following embodiments.

[0063] (1) The shape of the enclosed space may be a hemisphere, a rectangular prism, or the like. (2) The number of temperature sensing units and the number of external temperature sensing units are not limited to the number in Embodiment 1. In addition, the temperature sensing units may be arranged in a vertical direction within a closed space. (3) The test specimen does not have to be flat. For example, it may be a test specimen with multiple fins rising from another part of it. In this case, it is necessary that all of the fins are contained within the enclosed space. (4) The fluid filling the fluid flow space is not limited to a liquid; it may also be a gas. (5) When cooling the test specimen to cool the air in a closed space, it is advisable to reverse the vertical direction in the heat transfer evaluation device. (6) When forming a carbon nanotube-containing oxide film on the other side of the substrate, other methods such as sputtering or wet plating may be used. Furthermore, the substrate may be subjected to a treatment that forms a thin film on its surface that is different from the material of the substrate, rather than being limited to a carbon nanotube-containing oxide film. (7) The timing and duration for executing the third step are not limited to the embodiments described above. [Explanation of Symbols]

[0064] 10...Heat transfer evaluation device, 10C...Temperature detection unit, 10G...Fluid flow space, 10L...Closed space, F...Fluid, Tp...Test piece with other parts treated, Tp1, Tp2, Tp3...Test pieces with other parts not treated

Claims

1. A first step involves bringing a fluid into contact with a portion of the test specimen to heat or cool the test specimen, A second step involves performing air convection for a predetermined time within a closed space formed on the other side of the test specimen, A third step involves measuring the temperature inside the enclosed space, A fourth step involves comparing the temperature when using the test specimen without processing the other side with the temperature when using the test specimen with the other side processed. A method for evaluating heat transfer.

2. The method for evaluating heat transfer according to claim 1, wherein the fluid is a liquid.

3. The heat transfer evaluation method according to claim 1, wherein the temperature is the average value of measured temperatures at multiple locations within the closed space.

4. A closed space that is closed by attaching the test specimen, A fluid flow space through which fluid flows so as to be in contact with the surface of the test specimen opposite to the closed space, A temperature detection unit for detecting the temperature inside the enclosed space, A heat transfer evaluation device equipped with the necessary components.

5. The test specimen is attached from either above or below the enclosed space. The heat transfer evaluation apparatus according to claim 4, wherein the temperature sensing unit is located on the side away from the test piece in the enclosed space.

6. The heat transfer evaluation apparatus according to claim 4, wherein a plurality of temperature sensing units are provided within the closed space and are arranged at different locations within the closed space.

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