A measuring device and a measuring method for radiant cooling power

Abstract

The application belongs to the field of measuring instruments, and proposes a radiation refrigeration power measuring device and a measuring method. The device comprises a heat sink, a heat conduction layer, a thermocouple, a base layer and a power instrument. The heat conduction layer is arranged on the hot end side of the thermocouple, the heat sink is arranged at the bottom of the heat conduction layer, the base layer is arranged on the cold end side of the thermocouple, and the upper surface of the base layer is provided with a layer of radiation refrigeration material to be measured. The heat sink, the heat conduction layer, the thermocouple and the base layer jointly form a thermoelectric power generation sheet. The hot end and the cold end of the thermocouple are connected to the power instrument through wires to form a closed loop. Compared with the traditional cooling power tester, the application does not need additional power supply, additional controller and heater to complete the power measurement. The material to be measured is only needed to be placed on the surface of the base layer, and the radiation refrigeration power can be indirectly obtained by collecting the electric power through the power instrument. The application has the characteristics of simple structure and convenient operation.

Description

Technical Field

[0001] This application belongs to the field of measuring instruments, specifically relating to a measuring device and method for measuring radiative cooling power. Background Technology

[0002] The main principle of radiative cooling is to reflect solar energy (0.3–2.5µm) while simultaneously increasing the emissivity of the atmospheric window band (mainly 8–13µm), thus emitting heat into deep space through the atmospheric window, thereby reducing the temperature below ambient temperature even under solar radiation. With the in-depth research of radiative cooling technology, measuring the cooling power of materials has become an indispensable part. Compared to temperature reduction measurements, which are limited by environmental climate and latitude / longitude, cooling power measurements can more objectively reflect the cooling performance of materials and are beneficial for cross-sectional comparisons and standardized measurements. In June 2020, Ruiling New Energy Technology proposed an integrated device including a container with a measurement chamber, an atmospheric back radiation simulation component, and an atmospheric window simulation component for measuring radiative cooling power indoors. However, this device is complex, requiring heating to maintain the material at the ambient temperature, and cannot guarantee settling time, overshoot, and zero steady-state error when temperature changes occur. Therefore, there is still a need for a simpler method to achieve a breakthrough in characterizing cooling power.

[0003] There is currently no dedicated measuring device for cooling power on the market. The measurement method used in the laboratory is to use a controller to achieve temperature control under PID regulation, and to characterize the power consumed by the heating element as the cooling power. This method is difficult to implement, costly, and not easy to achieve temperature regulation. Summary of the Invention

[0004] To address the challenges of complex and difficult-to-use devices for measuring radiative cooling power, this application discloses a device for measuring radiative cooling power, employing the following technical solution:

[0005] A device for measuring the power of radiative cooling includes a heat sink, a heat-conducting layer, a thermoelectric resistor, a base layer, and a power meter; wherein a heat-conducting layer is provided on the hot end side of the thermoelectric resistor, a heat sink is provided at the bottom of the heat-conducting layer, a base layer is provided on the cold end side of the thermoelectric resistor, and a layer of radiative cooling material to be measured is placed on the upper surface of the base layer.

[0006] The heat sink, thermally conductive layer, thermoelectric resistor, and base layer together constitute a thermoelectric generator;

[0007] The power meter and the hot and cold ends of the thermoelectric resistor are connected by wires to form a closed loop.

[0008] The preferred solution is as follows:

[0009] It also includes an insulated box; the top of the insulated box is hollowed out and covered with a light-transmitting film, and the side wall of the insulated box is provided with several through holes; the thermoelectric resistor, the base layer, and the cooling layer are set inside the insulated box, and the power meter is set outside the insulated box.

[0010] The base layer is made of metal or glass.

[0011] The insulated box is made of polystyrene. Its low thermal conductivity effectively reduces the impact of external heat sources.

[0012] The light-transmitting film is made of polyethylene. It has excellent light transmission properties, and the radiation-cooling material layer under test can exchange heat with deep space through the atmospheric window via radiation.

[0013] It also includes: a wireless communication module and a host computer; the data measured in the power meter is transmitted to the host computer through the wireless communication module, and the host computer is used for data processing and outputting the radiation cooling power of the radiation cooling material layer to be tested.

[0014] The wireless communication module includes a WIFI module, a Bluetooth module, an infrared module, and an LTE cellular data communication module.

[0015] In the radiative cooling power measurement device of this application, the heat sink, the heat-conducting layer, the thermoelectric resistor, and the base layer together form a thermoelectric generator (TEG).

[0016] During measurement, the radiative cooling material layer to be measured is fixed to the substrate layer with thermally conductive silicone, and proper sealing and insulation are ensured, with the heat sink in full contact with the ambient air. At this time, the cooling layer (thin film material) at the cold end of the TEG lowers its own temperature through radiative cooling, which is then transferred to the substrate layer via heat conduction. Under the action of the heat sink, the temperature at the hot end is basically consistent with the ambient temperature. The TEG generates voltage and current based on the temperature difference between the cold and hot ends. After the power meter collects the voltage and current data from the TEG, it calculates the electrical power using P=UI, and finally obtains the cooling power based on a pre-fitted mathematical model.

[0017] Cooling power is a temperature-dependent variable and a characteristic of the material itself. By fabricating micro- and nano-structures on thin film materials to alter their physical properties, the reflectivity in the solar band and the emissivity in the 8-13µm (atmospheric radiation band) can be increased, thereby achieving a material temperature lower than the ambient temperature during the day.

[0018] A thermoelectric resistor comprises several pairs of N-type and P-type semiconductor units; these N-type and P-type semiconductor units form an electrocouple pair. When the temperatures at both ends are different, the charge carriers at the hot end have greater kinetic energy and diffuse and accumulate towards the cold end, making the number of charge carriers at the cold end greater than that at the hot end. The charge accumulated at the cold end establishes an electric field within the conductor, preventing further diffusion of charge carriers. When the conductor reaches equilibrium again, an electromotive force is generated across the conductor.

[0019] According to the Seebeck effect, the thermoelectric potential is:

[0020]

[0021] in The relative Seebeck coefficient is determined by the properties of semiconductor materials. For ambient temperature, This refers to the cold junction temperature of the TEG.

[0022] Furthermore, the relationship between the various powers generated during radiative cooling by the cooling material is as follows:

[0023]

[0024] in, Net cooling power, The material's radiant power. Solar radiation, This is atmospheric thermal radiation. To maximize the heat exchange capacity with the environment, This refers to the material temperature (i.e., the cold end temperature). The ambient temperature.

[0025]

[0026] Where A is the material area. For the spectrum and angular emissivity, For hemispherical angular integrals, This refers to the blackbody spectral radiation at temperature T. λ is the wavelength of light.

[0027] Assuming vertical emission, consider the wavelength range of 8-13µm:

[0028]

[0029] in, , , , is a constant, and T is the temperature of the cooling layer (thin film material). , , The same analysis and processing can be applied.

[0030] Finally, using the software polynomial fitting method, we can obtain:

[0031]

[0032] in, To reduce power consumption, To output electrical power to TEG, They are constants.

[0033] Therefore, the radiative cooling power can be obtained by measuring the electrical power.

[0034] Thermoelectric generators (TEGs) utilize the Seebeck effect to directly convert heat energy into electrical energy. A thin film material is placed at the cold end of the TEG, while the hot end directly contacts the environment, creating a temperature difference between the two ends. Through the Seebeck effect, a current is generated within the circuit, thus transmitting electrical power. Using techniques such as data fitting, the TEG's output electrical power can be converted into cooling power. TEGs for measuring cooling power have the following main functions and characteristics: They generate electrical power without an indirect conversion process, do not rely on external components, require no additional power supply, and do not require additional controllers or heaters; they can spontaneously achieve direct conversion from heat energy to electrical energy; they are simple, easy to measure, and have low maintenance costs: compared to methods that use temperature control to indirectly equalize heating power with cooling power, corresponding cooling power to the output electrical power of a TEG is more convenient and simple; using TEGs to measure cooling power does not use harmful media, making it safe and reliable for humans. Attached Figure Description

[0035] Figure 1 Schematic diagram of a device for measuring the power of radiative cooling;

[0036] Figure 2 Schematic diagram of the thermal insulation box structure;

[0037] Wherein: 1 is the radiation cooling material layer to be tested, 2 is the heat sink, 3 is the thermally conductive layer, 4 is the thermoelectric resistance element, 5 is the base layer, 6 is the light-transmitting film, 7 is the insulation box, 8 is the through hole, 9 is the power meter, and 10 is the host computer. Detailed Implementation

[0038] The present application will be further described below with reference to the accompanying drawings and embodiments:

[0039] Example 1

[0040] like Figure 1As shown: A measuring device for radiative cooling power includes a heat sink 2, a thermally conductive layer 3, a thermoelectric resistor 4, a base layer 5, and a power meter 9; wherein the thermally conductive layer 3 is provided on the hot end side of the thermoelectric resistor 4, the heat sink 2 is provided at the bottom of the thermally conductive layer, the base layer 5 is provided on the cold end side of the thermoelectric resistor 4, and the radiative cooling material layer 1 to be measured is placed on the upper surface of the base layer.

[0041] The heat sink 2, the thermally conductive layer 3, the thermoelectric resistor 4, and the base layer 5 together constitute a thermoelectric generator (TEG).

[0042] The power meter 9 and the hot and cold ends of the thermoelectric resistor 4 are connected by wires to form a closed circuit.

[0043] The power meter is used to measure voltage and current, calculate electrical power and cooling power. The base layer is located on the top of the device and is used to place the radiation cooling material layer to be tested. The thermoelectric resistor is located between the base layer and the thermally conductive layer, with the side closer to the base layer serving as the cold end of the TEG and the side closer to the thermally conductive layer serving as the hot end. The heat sink is located on the back of the thermally conductive layer to maximize heat exchange with the external environment and maintain the hot end temperature consistent with the ambient temperature. The power meter is connected to the output wires of the cold and hot ends of the TEG to obtain the power value.

[0044] A method for measuring radiative cooling power involves placing the radiative cooling material layer to be measured on a substrate layer, with the hot end of the TEG exposed to the air. The thermally conductive layer 3 and the heat sink 2 work together to maintain the temperature of the TEG hot end consistent with the ambient temperature. The radiative cooling material layer causes the cold end temperature of the thermoelectric element to be lower than the hot end temperature through radiative cooling, generating a voltage across the thermoelectric generator. The voltage and current can be detected in the power meter. Based on the mathematical model relationship between electrical power and radiative cooling power, the electrical power value is converted into radiative cooling power.

[0045] Example 2

[0046] like Figure 2 As shown, a measuring device for radiative cooling power, based on Embodiment 1, further includes: a heat preservation box 7; the top of the heat preservation box is hollowed out and covered with a light-transmitting film 6, and the side wall of the heat preservation box is provided with several through holes 8; a thermoelectric resistor 4, a base layer 5, a cooling layer 1 disposed inside the heat preservation box, and a power meter disposed outside the heat preservation box.

[0047] The top of the insulated box has a perforated opening similar in size to the radiative cooling material layer being tested, ensuring maximum heat exchange through the atmospheric window. Thermoelectric resistive element 4, base layer 5, and cooling layer 1 are located inside the insulated box, which helps maintain the stability of the TEG temperature, effectively reduces heat diffusion and the impact of wind, and provides a certain degree of insulation for the internal environment.

[0048] Example 3

[0049] A device for measuring radiative cooling power, based on Embodiment 1, further includes: a wireless communication module and a host computer 10; the data measured in the power meter is transmitted to the host computer through the wireless communication module, and the host computer is used for data processing and outputting the radiative cooling power of the radiative cooling material layer to be measured.

[0050] The wireless communication module includes: a WIFI module, a Bluetooth module, an infrared module, and an LTE cellular data communication module.

[0051] In one measurement example, when measuring a 1mm thick thin film of polyvinylidene fluoride (PVDF) doped with nanoscale air spheres, the film was attached to a substrate, the device was connected, and the power meter measured the TEG output voltage at 28.8mV and the current at 59.7uA. The data was transmitted to the host computer via a wireless communication module.

[0052] The calculation of this mathematical model yields a cooling power output of 69.2 W / m². Literature review shows a theoretical value of 66.7 W / m², indicating the error is within a controllable range.

Claims

1. A measuring device for radiative cooling power, characterized in that... include: Heat sink, thermally conductive layer, thermoelectric resistor, base layer, power meter, and insulation box; A heat-conducting layer is provided on the hot end side of the thermoelectric resistor, a heat sink is provided at the bottom of the heat-conducting layer, a base layer is provided on the cold end side of the thermoelectric resistor, and a radiation cooling material layer to be tested is placed on the upper surface of the base layer. The heat sink, thermally conductive layer, thermoelectric resistor, and base layer together form a thermoelectric generator, which is used to generate heat and electricity through the temperature difference between the heat sink and the environment when the radiation cooling material layer under test generates a radiation cooling effect. The power meter is connected to the hot and cold ends of the thermoelectric resistor via wires to form a closed loop, which is used to detect the electrical power generated by the thermoelectric generator and indirectly calculate the radiative cooling power based on the electrical power. The top of the insulation box is hollowed out and covered with a light-transmitting film, and the side wall of the insulation box is provided with several through holes. The thermoelectric resistor and the base layer are disposed inside the insulation box, and the power meter is disposed outside the insulation box. The insulation box is used to provide a stable measurement environment for the thermoelectric generator.

2. The measuring device for radiative cooling power according to claim 1, characterized in that: The base layer is made of metal or glass.

3. The measuring device for radiative cooling power according to claim 1, characterized in that: The insulated box is made of polystyrene.

4. The measuring device for radiative cooling power according to claim 1, characterized in that: The light-transmitting film is made of polyethylene.

5. The measuring device for radiative cooling power according to claim 1, characterized in that: Also includes: Wireless communication module, host computer; The data measured in the power meter is transmitted to the host computer via a wireless communication module. The host computer processes the data and outputs the measured radiation cooling power of the radiation cooling material layer under test.

6. The measuring device for radiative cooling power according to claim 5, characterized in that: The wireless communication module includes a WIFI module, a Bluetooth module, an infrared module, and an LTE cellular data communication module.

7. The measuring device for radiative cooling power according to any one of claims 1 to 6, characterized in that: The thermoelectric resistor includes several pairs of N-type semiconductor units and P-type semiconductor units; the N-type semiconductor units and P-type semiconductor units form a thermocouple pair.

8. A method for measuring radiative cooling power, characterized in that: The radiation cooling material layer to be tested is placed on the base layer of the radiation cooling power measuring device according to any one of claims 1 to 6. The radiation cooling material layer to be tested makes the cold end temperature of the thermoelectric resistive element lower than the hot end temperature through radiation cooling. The power meter detects the electrical power in the closed loop and converts the electrical power into radiation cooling power according to the mathematical model relationship between electrical power and radiation cooling power.

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