Thermal resistance testing device and method for immersed phase change cooling radiator

Abstract

The invention provides a thermal resistance testing device and method for an immersed phase change cooling radiator, and relates to the technical field of heat dissipation testing of high-power power electronic devices. The testing device comprises a phase change cooling testing system, a direct current power supply system and a power module testing clamp assembly. According to the device, an immersed cavity with the ratio of 1: 1 to an actual converter valve power module is taken as a test environment, and the tested power module is wholly immersed in insulating cooling liquid with the same model as an actual working condition, so that a radiator runs under real latent heat of vaporization, a steam flow field and an insulating distance, and working condition level simulation is realized. The problems that an existing testing scheme can only aim at single-phase water cooling and cooling medium phase-change-free scenes, the heat resistance testing result of the radiator is low, and the overheating risk is likely to be caused are solved. The device provides reliable data support for design and optimization of the heat radiator by accurately measuring the thermal resistance of the phase change heat radiator under the real boiling-condensation working condition, so that the accuracy and reliability of heat radiation design are improved.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation testing technology for high-power power electronic devices, and specifically to a thermal resistance testing device and method for immersion phase change cooling radiators. Background Technology

[0002] Heat dissipation, cooling, and insulation of high-power power electronic equipment are core issues that must be considered in equipment research and development. Currently, deionized water cooling and forced air cooling are relatively mature cooling technologies. However, deionized water cooling technology has a complex structure, requires a water cooling system, occupies a large area, and is complex to operate and maintain; forced air cooling technology has high operating noise and low cooling power.

[0003] With the development of high-voltage, high-capacity equipment technology, the increasing size and cost of equipment to meet cooling and insulation requirements hinder miniaturization, integration, and industrial application. Energy storage converters and offshore wind power converters also urgently require lightweight, low-noise cooling solutions. Phase change cooling technology utilizes the latent heat of vaporization of low-boiling-point insulating media to achieve efficient heat dissipation within a small volume and significantly shorten the primary insulation distance, thus solving the technical challenges of large size and difficult heat dissipation in high-power power electronic equipment. This technology will be a crucial research direction for solving insulation and cooling issues in future power electronic equipment; however, the industry lacks effective testing methods for phase change cooling radiators. Existing thermal resistance testing methods are mainly designed for single-phase cooling media (such as water and air) and cannot simulate the complex thermodynamic behavior caused by the boiling-condensation cycle during phase change. This leads to significant deviations between test results and actual operating conditions, failing to accurately reflect the steady-state performance of the radiator under real conditions. More importantly, it completely fails to capture the peak characteristics of transient thermal resistance during phase change, resulting in thermal design deviations, underestimation of overheating risks, and severely restricting the reliable application and iterative optimization of phase change cooling technology.

[0004] Therefore, there is an urgent need to develop a thermal resistance testing device and method specifically for immersion phase change cooling radiators. This would solve the problem that existing testing schemes can only be used for single-phase water cooling, where the cooling medium does not undergo phase change and cannot simulate real phase change cooling conditions. As a result, the thermal resistance test results of the radiators are too low, which can easily lead to overheating risks. Summary of the Invention

[0005] The purpose of this invention is to provide a thermal resistance testing device and method for immersion phase change cooling radiators. It creates an original 1:1 full-size, full-condition immersion phase change cooling testing environment to solve the problem that existing testing schemes can only be used for single-phase water cooling, where the cooling medium does not undergo phase change and cannot simulate real phase change cooling conditions, resulting in low radiator thermal resistance test results and the risk of overheating.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In one aspect, this specification provides a thermal resistance testing device for an immersion phase change cooling radiator, comprising: a phase change cooling testing system, a DC power supply system, and a power module testing fixture assembly; The DC power supply system and the power module test fixture assembly are electrically connected via copper busbars, and the power module test fixture assembly is placed in the center of the sealed cavity inside the phase change cooling test system. A DC power supply system is used to provide DC current to the power module under test to generate heat, and can invert the electrical energy on the DC bus into power frequency AC power to feed back to the grid; it equivalently simulates the loss of the power module under test and the heat dissipation conditions of the heat sink. A power module test fixture assembly includes a horizontal clamping mechanism and a temperature measurement unit for clamping at least one power module under test. The horizontal clamping mechanism provides a constant mechanical clamping force and conduction current to the power module under test, and the temperature measurement unit monitors the temperature of the power module under test. The power module under test is a unit composed of several power devices and a heat sink. The phase change cooling test system consists of a sealed cavity, a heat exchanger, a cooling medium, a vacuum-liquid injection module, and a circulation channel. It is used to provide circulating cooling, air isolation, and a sealed environment for the power module under test and the coolant, simulating the actual working environment of an immersion phase change cooling system.

[0007] Secondly, this specification provides a method for testing the thermal resistance of an immersion phase change cooling radiator, including: Select the heat sink to be tested in the power module under test and arrange temperature measurement points; the temperature monitoring points of the heat sink to be tested are respectively set on the anode platform, cathode platform and the immersion cooling medium of the heat sink. Apply a positive pressure of 0.5 bar to the sealed cavity and maintain it for 1 hour; The vacuum-liquid injection module evacuates the sealed cavity to a vacuum level not exceeding 500Pa, and injects fluorinated liquid through vacuum suction, with the liquid level 30mm above the upper surface of the radiator. Turn on the power module under test and apply a DC current using the DC current system; the heat generated by the power module under test causes the cooling medium to generate steam, and adjust the system exhaust valve and the magnitude of the conduction current to expel the residual air in the sealed cavity and the internal space of the phase change cooling test system; Record the temperature and pressure data of the sealed cavity. If the temperature change of the radiator surface does not exceed 1°C and the absolute pressure change of the cavity does not exceed 0.05 bar within 15 to 30 minutes, the power module under test is determined to have reached thermal equilibrium. Under thermal equilibrium, the heat dissipation power of the heat sink under test is calculated based on the DC current of the power module under test; the thermal resistance of the heat sink under test is determined based on the heat dissipation power of the heat sink under test and the temperature at each temperature measurement point.

[0008] Thirdly, this specification provides a transient thermal resistance testing method for immersion phase change cooling radiators, including: The power module under test reaches thermal equilibrium at a specific power level. The reference thermal resistance value under this steady state and the temperature at each temperature measurement point are recorded. In thermal equilibrium, a command is sent to the DC current source to cause a step change in the amplitude and power of the current passing through the power module under test in a very short time. At the same time, high-speed voltage, current and temperature data acquisition is started, and the temperature of each temperature measurement point at different times is recorded synchronously. Based on the collected transient data, the step response curve R of the transient thermal resistance as a function of time is obtained. sa (t): ;t represents the time of temperature acquisition; in, T A ( t )for t The temperature of the radiator anode platform at any given time, T K ( t )for t The temperature of the radiator cathode mesa at any given time. T f ( t )for t Temperature of the immersion radiator cooling medium at any given time, Δ P s The magnitude of power change before and after the step jump; Using the least squares method, the step response curve is fitted into an exponential function form, and key parameters for evaluating the dynamic performance of the heat sink are extracted: thermal time constant τ and peak thermal resistance R. sa_peak ; By conducting step tests with different amplitudes and power increase / decrease directions, the peak thermal resistance and thermal time constant for different power amplitudes and change directions are obtained. After function fitting, the junction temperature fluctuation under any complex power waveform can be accurately predicted.

[0009] This specification provides a thermal resistance testing apparatus and method for immersion-type phase change cooling radiators. The apparatus includes a phase change cooling testing system, a DC power supply system, and a power module under test. Using a 1:1 immersion chamber identical to an actual converter valve power module as the testing environment, the power module under test is completely immersed in an insulating coolant of the same type as in actual operating conditions. This allows the radiator to operate under realistic latent heat of vaporization, vapor flow field, and insulation distance, achieving operational-level simulation. This solves the problems of existing testing schemes, which can only target single-phase water cooling, lack phase change in the cooling medium, cannot simulate real phase change cooling conditions, and produce low thermal resistance test results, easily leading to overheating risks. By accurately measuring the thermal resistance of the phase change radiator under real boiling-condensation conditions, this apparatus reduces the deviation between laboratory thermal resistance data and actual operating conditions, providing reliable data support for radiator design and optimization, significantly improving the accuracy and reliability of heat dissipation design. It also greatly improves testing efficiency. Compared with the traditional method of 3-5 hours, this testing method compresses the single test cycle to less than 60 minutes, improving efficiency by 4-7 times, significantly shortening the heat sink R&D and testing cycle, and reducing R&D costs.

[0010] Specifically, the apparatus and method improved in this specification have the following advantages: 1. Overcoming the shortcomings of existing technologies that cannot simulate real phase change cooling conditions, a 1:1 full-size, full-condition immersion phase change cooling test environment was first constructed to evaluate the performance of the heat sink under real conditions. 2. A complete method for testing thermal resistance combining steady-state and transient conditions was proposed. In particular, the method of measuring key dynamic parameters such as transient thermal impedance and thermal time constant of heat sinks through the power step method was introduced, which fills the gap in existing testing methods and provides indispensable data support for the reliability design of power devices under dynamic conditions. 3. To address the measurement inaccuracies caused by vibration and thermal deformation in phase change environments, a highly reliable and precise integrated measurement and fixing system was designed. 4. To address the issues of high energy consumption and waste heat emissions interfering with the testing environment in traditional resistive load testing methods, a feedback DC power supply system is introduced and integrated for the first time into the field of phase change heat dissipation testing.

[0011] The device described in this manual can realistically simulate phase change environments and accurately measure steady-state and transient thermal resistance characteristics, thereby providing effective data support for radiator design verification and system reliability assessment. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a thermal resistance testing device for an immersion phase change cooling radiator provided in the embodiments of this specification; Figure 2This is a schematic diagram of the circuit topology of a DC power supply system provided in the embodiments of this specification; Figure 3 This is a front view schematic diagram of a power module test fixture assembly provided in the embodiments of this specification. Figure 4 This is a schematic diagram of a heat exchanger structure cross-section provided in the embodiments of this specification; Figure 5 This is a schematic diagram of a thermal resistance testing method for an immersion phase change cooling radiator provided in the embodiments of this specification.

[0013] Figure label: In this circuit, T1 and D1 are half-bridge rectifier circuits, T2 and D2 are half-bridge rectifier circuits, C1 is the bus capacitor, R1 is the discharge resistor, T3 and D3 are half-bridge inverter circuits, T4 and D4 are half-bridge inverter circuits, T1, D1, T2, and D2 form a full-bridge rectifier circuit, and T3, D3, T4, and D4 form a full-bridge inverter circuit.

[0014] Among them, 1. Electrical connection copper busbar, 2. Left and right horizontal clamps, 3. Insulating support rod, 4. Insulating gasket, 5. Insulating pad. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not to a precise scale, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0016] It should be noted that, in order to clearly illustrate the content of this invention, several embodiments are provided to further explain different implementations of the invention. These embodiments are enumerated rather than exhaustive. Furthermore, for the sake of brevity, content mentioned in the preceding embodiments is often omitted in the following embodiments. Therefore, content not mentioned in the later embodiments can be referred to in the preceding embodiments. Specific Implementation Example 1:

[0018] This embodiment provides a thermal resistance testing device for immersion phase change cooling radiators. (See also...) Figure 1 , Figure 2 ; First, it should be noted that the working principle of the thermal resistance testing device provided in this embodiment is as follows: The heat sink and power components are installed in a sealed enclosure immersed in coolant. A DC current is applied to the power components via a copper busbar, causing the IGCT devices to generate active power losses. The heat generated by these losses is conducted through the device's electrodes to the heat sink. The heat dissipated by the heat sink between two IGCT devices originates from the anode of one IGCT device and the cathode of the other, equivalent to the losses of a single IGCT device. The heat is conducted and diffused through the heat sink to its surface, where it comes into contact with the surrounding coolant. This causes the coolant to reach its boiling point and vaporize, forming a gaseous state. This vaporized coolant enters the upper heat exchanger, where it is cooled and changes from a gaseous state to a liquid state, flowing back to the bottom of the enclosure, thus forming a self-circulating cooling system. The coolant surrounding the heat sink undergoes a phase change and vaporization, absorbing heat and carrying away heat from the heat sink surface, achieving heat dissipation.

[0019] Based on the above working principle, the specific structure and function of each component of the thermal resistance testing device in this embodiment are described in detail: The thermal resistance testing device specifically includes: a phase change cooling testing system, a DC power supply system, and a power module testing fixture assembly; The DC power supply system and the power module test fixture assembly are electrically connected via copper busbars, and the power module test fixture assembly is placed in the center of the sealed cavity inside the phase change cooling test system. Power module test fixture assembly, including a horizontal clamping mechanism and a temperature measurement unit; A power module test fixture assembly is used to clamp at least one power module under test. The horizontal clamping mechanism is used to provide a constant mechanical clamping force and conduction current to the power module under test. The temperature measurement unit is used to monitor the temperature of the power module under test. The power module under test is a unit composed of several power devices and a heat sink. The DC power supply system is used to provide DC current to the power module under test to generate heat, and can invert the electrical energy on the DC bus into power frequency AC power to feed back to the grid; it equivalently simulates the loss of the power module under test and the heat dissipation conditions of the heat sink. The phase change cooling test system consists of a sealed cavity, a heat exchanger, a cooling medium, a vacuum-liquid injection module, and a circulation channel. The phase change cooling test system is used to provide circulating cooling, air isolation, and a sealed environment for the power module under test and the coolant, simulating the actual working conditions of immersion phase change cooling.

[0020] Furthermore, the specific internal structure of each system and component will be described in detail below: First, such as Figure 2 As shown, the DC power supply system includes a full-bridge rectifier circuit, bus capacitors, leakage resistors, a full-bridge inverter circuit, an LCL filter, and voltage and current measuring devices. The input terminal of the full-bridge rectifier circuit is connected to the AC power grid, and the output terminal is connected in parallel with the bus capacitor to form a DC bus. A discharge resistor is connected in parallel across the bus capacitor to release DC bus energy during emergency stops. The full-bridge inverter circuit has a bus capacitor connected to the DC side and an AC grid connected to the AC side via an LCL filter to achieve energy feedback. LCL filters are used to control the power quality fed back to the grid, ensuring that it meets grid connection requirements.

[0021] The voltage and current measurement device includes a Hall voltage sensor and a Hall current sensor, which respectively collect the DC bus voltage and output current, and send the sampled signals to the FPGA controller to form a closed-loop control.

[0022] The DC power supply system features energy feedback. When heating the power module under test is required, the power supply operates in rectification mode, drawing power from the grid and outputting a stable, low-ripple DC current. Electrical energy is converted into heat energy via the IGCT chip. When the test ends or the power is adjusted, the electrical energy on the DC bus is inverted into AC power at industrial frequency and fed back to the grid. Compared to traditional load bleedering schemes, this laboratory achieves a feedback efficiency of >70%, saving approximately 30,000 kWh of electricity per unit per year, and reducing background noise by more than 10 dB, thus realizing green testing.

[0023] It should be noted that the power supply system can select AC power according to the actual situation of the semiconductor devices; Secondly, the power module under test is a unit composed of several power devices and a heat sink; Specifically, this embodiment provides a preferred solution for the structure of the power under test module. Each power module under test (DUT) has a sandwich structure of heat sink-IGCT-heat sink, specifically containing three heat sinks and two IGCT chips. Adjacent units share one heat sink. The DUT is placed horizontally and parallel to the observation window. The DUT is clamped by a horizontal clamping mechanism, see [link to documentation]. Figure 3 ; The horizontal clamping mechanism adopts a symmetrical structure, including an electrical connection copper busbar 1 in the vacuum chamber, left and right horizontal clamps 2, insulating support rods 3, insulating pads 4, and insulating pads 5; the left and right horizontal clamps have built-in butterfly spring groups to provide a constant pressure of not less than 100 kN, allowing at least ±3° ball joint self-alignment, and a ball joint support is provided between the clamp and the insulating pad, with pressure unevenness ≤5%.

[0024] It should be noted that the use of a disc spring assembly in this embodiment has the following advantages: 1. Thermal Expansion Compensation: During testing, the heatsink and IGCT chip experience dramatic temperature increases and expansion. Ordinary rigid clamps would cause a sharp rise in pressure, potentially damaging the chip. A disc spring absorbs this thermal expansion through its own deformation, controlling pressure fluctuations within an extremely narrow range of ±3%, something that rigid bolt locking cannot achieve.

[0025] 2. Ensure good contact: Constant pressure ensures stable contact resistance between the power device and the heat sink interface, which is a prerequisite for accurate measurement of heat dissipation power. Pressure fluctuations will directly lead to inaccurate heat dissipation power measurement.

[0026] 3. A butterfly spring assembly is used and a constant pressure of 100kN±3% is provided to compensate for pressure fluctuations caused by thermal deformation during the test and to ensure stable contact resistance.

[0027] The insulating support rod 3 is made of high-insulation-strength ceramic material with a radius of not less than 15 mm. The insulating pad 4 and the insulating plate 5 are made of polyether ether ketone-based composite material with a thickness of not less than 2 mm and a creepage distance of ≥20 mm.

[0028] Furthermore, to ensure mechanical stability under 100kN pressure, the radius of the ceramic support rod is preferably 15mm, and to meet the DC 1200V high voltage insulation requirements, the creepage distance of the insulating pad is designed to be ≥20mm.

[0029] Furthermore, in this embodiment, the insulating support rod 3 is made of alumina ceramic, a high-insulation-strength ceramic material, with a radius of 15 mm; the insulating pad 4 is made of polyetheretherketone (PEEK)-GF30 composite material with a thickness of 2 mm; and the insulating pad 5 is made of polyetheretherketone (PEEK)-GF30 composite material with a thickness of 2 mm and a creepage distance ≥ 20 mm.

[0030] Specifically, the use of alumina ceramic for the insulating support rod 3 has the following advantages: 1. Extremely high insulation strength: In high-temperature, high-pressure fluorinated liquid vapor environments, it is essential to ensure that no creepage or breakdown occurs under DC 1200V or even higher voltages. Ceramic insulation properties are far superior to ordinary plastics or resins, making it the preferred choice for high-pressure vacuum environments; 2. Extremely high compressive strength: It can withstand a huge clamping pressure of 100 kN without deformation or breakage, providing stable mechanical support for the entire clamping system.

[0031] 3. Excellent thermal stability: Under drastic temperature changes, its deformation coefficient is extremely small, and the stability of the clamping pressure will not be affected by thermal expansion and contraction.

[0032] 4. Chemical corrosion resistance: It can withstand long-term immersion and corrosion by fluorinated coolant.

[0033] Furthermore, under a pressure of 100 kN, a sufficient cross-sectional area is required to ensure that the compressive stress remains within the safe range of the ceramic material's compressive strength, preventing it from being crushed. A radius of 15 mm is an optimized result that meets the strength requirements while also taking into account structural compactness.

[0034] Furthermore, the insulating pad 4 and the insulating plate 5 are made of PEEK-GF301, which has the following advantages: 1. The strength, rigidity, fatigue resistance and dimensional stability are greatly improved, and it can withstand 100kN of cyclic pressure for a long time without creep or fracture; 2. Insulation: It can maintain extremely high insulation resistance even in high temperature and humid environments; 3. Good machinability: It can be precisely machined into the required gasket and pad shapes.

[0035] Based on this, this horizontal fixture enables rapid replacement of heat sinks and power devices, constant pressure of 100 kN ± 3%, 20 mm creepage distance insulation, and 100% unobstructed visibility area without the need for heat sink processing.

[0036] Furthermore, IGBTs or SiC-MOSFETs can be selected as semiconductor devices to replace IGCTs in order to meet the testing requirements of power modules with different voltage and current levels. Furthermore, the power module under test is also equipped with a multi-channel temperature probe, which is used for array-level multi-point temperature measurement; the multi-channel temperature probe can sample traditional thermocouple sensors or fiber optic sensors, and fiber optic sensors have higher anti-electromagnetic interference capabilities and smaller size; The sealed chamber is a 5mm thick rectangular shell of 316L stainless steel, with an inner diameter of 1000mm × 800mm × 200mm. Metal flanges are retained at the top and bottom for mounting the condenser and vacuum-injection interface. Two 300mm × 200mm rectangular windows are machined on the front and back sides, with 5mm wide and deep sealing grooves milled around each window (i.e., a 5mm wide and deep groove is machined around the window for installing a sealing ring) and embedded with fluororubber O-rings. A 20mm thick tempered glass (or pressure-resistant polycarbonate) observation window is installed inside the window, secured by a stainless steel pressure plate and quick-release bolts, allowing for online disassembly and replacement. The metal walls ensure a safe internal pressure of 0.3MPa, while the transparent window provides visual observation of boiling. An explosion-proof membrane or safety valve is installed at the top of the chamber, with a burst pressure set at 0.35MPa, for pressure relief in case of system malfunction, ensuring experimental safety. The bottom of the chamber is designed with a 5° inclination angle, and a drain valve (DN20, fluororubber seal) is installed at the lowest point to facilitate complete drainage of the cooling medium.

[0037] It should be noted that if the moisture is not completely drained, the cooling medium will contain a high moisture content, which will cause the insulation strength of the cooling medium to decrease sharply.

[0038] Furthermore, the shape of the sealed cavity can also be cylindrical or hexagonal to adapt to different space constraints.

[0039] Based on this, the sealed cavity adopts a "metal frame + partial transparency" scheme, which improves the safety margin of positive and negative pressure, ensures the visualization of the test process, meets the requirements of long-term operation under dual working conditions of 0.3 MPa positive pressure and 500 Pa negative pressure, and effectively prevents the residue of internal cooling medium after the test.

[0040] In this embodiment, a non-contact heat exchanger is used, horizontally installed at the top, to condense the steam at the top of the chamber into liquid. The cooling water pipe is coaxially connected to the steam outlet of the circulation channel. The steam condenses inside a Ø20×5 mm 316L pipe, while the cooling water flows through an external Ø108×4 mm pipe, forming counter-current heat exchange. The condensation pipe adopts a spiral design, and the condensate returns by gravity at a 5° inclination angle at the bottom, using an external pump for circulation. See the cross-sectional view. Figure 4 .

[0041] Cooling medium, which is the same type of coolant used in the actual working conditions of the radiator, is used for heat transfer and insulation; The vacuum-injection module is used to extract air from the sealed cavity and inject coolant. The circulation channel is used to connect the sealed cavity, heat exchanger, and vacuum-liquid injection module to maintain media circulation; it is connected to the sealed cavity through the vacuum-liquid injection interface and to the vacuum-liquid injection module through the KF50 interface. Types of heat exchangers include shell-and-tube, coil, and plate-fin.

[0042] In summary, this embodiment uses a 1:1 immersion chamber, identical to the actual converter valve power module, as the test environment. The power module under test is completely immersed in an insulating coolant of the same type as the actual operating condition, allowing the radiator to operate under real latent heat of vaporization, steam flow field, and insulation distance, achieving operating condition-level simulation. This solves the problems of existing testing schemes, which can only target single-phase water cooling, have no phase change in the cooling medium, cannot simulate real phase change cooling conditions, and produce low radiator thermal resistance test results, easily leading to overheating risks. This device accurately measures the thermal resistance of the phase change radiator under real boiling-condensation conditions, reducing the deviation between laboratory thermal resistance data and actual operating conditions. It provides reliable data support for radiator design and optimization, significantly improving the accuracy and reliability of heat dissipation design. It also greatly improves testing efficiency. Compared to the traditional method's 3-5 hours, this testing method compresses a single test cycle to less than 60 minutes, increasing efficiency by 4-7 times, significantly shortening the radiator R&D and testing cycle, and reducing R&D costs. Specific Implementation Example 2:

[0044] This implementation provides a method for testing the steady-state thermal resistance of an immersion phase change cooling radiator. (See [link to relevant documentation]) Figure 5 It includes the following steps: Step 502: Select the heat sink to be tested in the power module under test and arrange the temperature measurement points; wherein the temperature monitoring points of the heat sink to be tested are respectively set on the anode platform, cathode platform and the immersion cooling medium of the heat sink under test; Specifically, three heat sinks of the same specifications and two press-fit IGCTs of the same model are press-fitted in a sandwich structure of "heat sink-chip-heat sink" and fixed with a high-rigidity clamp to ensure that the axial pressure exceeds 100kN, and then the circuit connection is completed. It should be noted that the temperature detection probes at the temperature monitoring points on the anode and cathode platforms of the radiator are placed at the pressing platform after being deeply buried. During operation, direct contact between the temperature detection probes and the cooling medium should be avoided to prevent measurement errors. The temperature monitoring points in the cooling medium submerged in the radiator are 20mm away from the submerged radiator at a horizontal distance. Furthermore, before performing step 504, the method further includes a system check step, specifically: Conduct a comprehensive inspection to ensure the monitoring status of physical quantities such as the measurement system, cooling self-circulation system, and current loop is normal. Power on the power component power supply system and debug the trigger control system to ensure the power component's control and power supply functions are normal.

[0045] Step 504: Apply positive pressure of 0.5 bar to the sealed cavity and maintain it for 1 hour to ensure that there is no leakage in the entire system. Step 506: The vacuum-injection module performs a three-stage vacuum treatment on the sealed cavity. First, it is evacuated to 1000Pa and held for 10 minutes, then evacuated to 500Pa and held for 10 minutes, and finally evacuated to ≤100Pa to ensure that the residual air content inside the cavity is ≤0.1%. Fluoride liquid is injected by vacuum suction, with the liquid level 30mm above the upper surface of the radiator. Step 508: Turn on the power module under test and apply DC current using the DC current system; the current range is set to 0.1. I n ~1.0 I n With a step size of 0.1 I n Gradually increase. The heat generated by the power module under test causes the cooling medium to produce steam. Adjust the system's exhaust valve and conduction current to expel residual air from the sealed cavity and the internal space of the phase change cooling test system. Step 510: Record the temperature and pressure data of the sealed cavity. If the temperature change of the radiator surface does not exceed 1°C within 15 to 30 minutes, the absolute pressure change of the cavity does not exceed 0.05 bar, and the fluctuation of the cooling medium circulation flow rate is less than 2%, then the power module under test is determined to have reached thermal equilibrium. Step 512: Under thermal equilibrium, calculate the heat dissipation power of the heat sink under test based on the DC current of the power module under test; determine the steady-state thermal resistance of the heat sink under test based on the heat dissipation power of the heat sink under test and the temperature at each temperature measurement point. It should be noted that, under thermal equilibrium, the heat dissipation power of the radiator is equal to the output power of the power component. Ignoring the heat dissipated by the IGCT ceramic tube through conduction, the heat dissipation power of the tested radiator can be calculated using the following formula: ; r T For the slope resistor of a power semiconductor device, V T The threshold voltage of power semiconductor devices is a unique parameter of IGCT devices and can be found in the information table of specific power semiconductor devices. The steady-state thermal resistance R of the heat sink under test sa_steady for: ; Among them, T A For the anode platen temperature of the radiator, T K For the cathode mesa temperature of the heat sink, T f The temperature of the cooling medium submerged in the radiator.

[0046] In summary, the method in this embodiment completely immerses the radiator under test in a fluorinated liquid identical to actual operating conditions, simulating real latent heat of vaporization, vapor flow field, and insulation distance, thus achieving operating-condition-level thermal resistance testing. Compared to traditional methods, this method is specifically designed for the testing needs of phase change cooling radiators, providing a testing environment close to real-world conditions. It can more accurately measure the thermal resistance characteristics during the phase change process, better reflecting the radiator's performance in practical applications. Specific Implementation Example 3:

[0048] This implementation provides a transient thermal resistance testing method for immersion phase change cooling radiators, including the following steps: Step 1: Following steps 502 to 512 in Embodiment 2, bring the power module under test to a specific power level (e.g., 50% of the rated current, i.e., 0.5). I n The system reaches a state of thermal equilibrium and records the reference thermal resistance R under this steady state. sa_steady and the temperature at each temperature measurement point; Temperature measurement points include the anode platform of the radiator, the cathode platform of the radiator, and the cooling medium immersed in the radiator. Step 2: Apply a power step disturbance and acquire data at high speed.

[0049] Under thermal equilibrium, the control system sends a command to the DC current source, causing the current through the power module under test to undergo a step change in both amplitude and power within a very short time (e.g., <100ms). I n Step jump to 0.7 I n This means increasing power by 20%. Simultaneously, high-speed voltage, current, and temperature acquisition is initiated (sampling rate no less than 10 Hz, preferably 100 Hz), synchronously and continuously recording the temperature at each measurement point at different times: T A (t), T K (t), T f (t) and the power change ΔP before and after the step jump s Based on the collected transient data, a step response curve of transient thermal resistance changing with time can be obtained: ; Using the least squares method, the step response curve is fitted into an exponential function form, and the key parameter for evaluating the dynamic performance of the heatsink is extracted: peak thermal resistance R. sa_peak Thermal time constant τ. Peak thermal resistance. R sa_peak Its value is R sa (t) The maximum value on the transient response curve. Thermal time constant τ: its value is... R sa (t) is the time required for the value to drop from the peak to 1 - 1 / e (approximately 63.2%) of the difference between the peak and the steady-state value.

[0050] It should be noted that during a power step change, due to the heat capacity of the heat sink, the temperature change lags behind the power change, resulting in a peak value R in the transient thermal resistance. sa_peak The thermal time constant τ typically appears within a very short time (milliseconds to seconds) after a power step is applied. This value is much higher than the final steady-state value and characterizes the worst-case performance of the heat dissipation system in response to instantaneous thermal shocks. It is a key indicator for assessing the short-term overload risk of a device. The thermal time constant τ characterizes the speed of the overall thermal response of the heat dissipation system; the smaller the τ value, the faster the response. This peak value is a key indicator for assessing whether a device will overheat under short-term overload conditions.

[0051] Step 3: Multi-power step testing and modeling. To comprehensively characterize the dynamic characteristics of the heatsink, steps 1 and 2 can be repeated, performing tests with different amplitudes (e.g., from 0.3...). In Up to 0.8 I n Step tests were conducted in different directions (power increase / power decrease). After collecting sufficient data, the peak thermal resistance R for different power amplitudes and directions of change can be obtained. sa_peak The thermal time constant τ, through function fitting, can be used to accurately predict junction temperature fluctuations under any complex power waveform.

[0052] This embodiment of the method goes beyond a single steady-state thermal resistance value, comprehensively characterizing the thermal performance of the heat sink under real dynamic conditions such as startup and sudden load changes. This provides irreplaceable key data for system-level reliability design and lifespan prediction. By capturing transient thermal resistance peaks, the highest junction temperature faced by power devices under short-term overload can be directly assessed, thereby mitigating the risk of failure due to transient overheating during the design phase—something traditional steady-state testing cannot achieve. The extracted thermal time constant (τ) is a standardized parameter that can be used for dynamic performance comparison and optimization between different heat sink design schemes.

[0053] In summary, the device in this embodiment can realistically simulate phase change environments and accurately measure steady-state and transient thermal resistance characteristics, thereby providing effective data support for radiator design verification and system reliability assessment.

[0054] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than those shown in the embodiments and still achieve the desired result. Furthermore, the specific order or sequential order shown in the drawings is not necessarily required to achieve the desired result; in some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0055] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A thermal resistance testing device for an immersion phase change cooling radiator, characterized in that, include: Phase change cooling test system, DC power supply system, power module test fixture assembly; The DC power supply system and the power module test fixture assembly are electrically connected via copper busbars, and the power module test fixture assembly is placed in the center of the sealed cavity inside the phase change cooling test system. The power module test fixture assembly includes a horizontal clamping mechanism and a temperature measurement unit for clamping at least one power module under test. The horizontal clamping mechanism is used to provide a constant mechanical clamping force and conduction current to the power module under test, and the temperature measurement unit is used to monitor the temperature of the power module under test. The power module under test is a standard unit composed of power devices and a heat sink. The DC power supply system is used to provide heating power to the power module under test and can invert the electrical energy on the DC bus into power frequency AC power to feed back to the grid. The phase change cooling test system consists of a sealed cavity, a heat exchanger, a cooling medium, a vacuum-liquid injection module, and a circulation channel. It is used to provide circulating cooling, air isolation, and a sealed environment for the power module under test and the coolant, simulating the actual working environment of an immersion phase change cooling system.

2. The apparatus according to claim 1, characterized in that: The horizontal clamping mechanism adopts a symmetrical structure, including: an electrical connection copper busbar (1) in the vacuum chamber, left and right horizontal clamps (2), an insulating support rod (3), an insulating pad (4), and an insulating plate (5); wherein the left and right horizontal clamps (2) are equipped with a built-in butterfly spring assembly to provide a constant pressure of not less than 100 kN, allowing at least ±3° self-aligning of the ball joint, and a ball joint support is provided between the left and right horizontal clamps (2) and the insulating plate (5), with a pressure non-uniformity of ≤5%; The insulating support rod (3) is made of high-insulation-strength ceramic material with a radius of not less than 15 mm. The insulating pad (4) and insulating plate (5) are made of polyether ether ketone-based composite material with a thickness of not less than 2 mm and a creepage distance of ≥20 mm.

3. The apparatus according to claim 2, characterized in that, The power module test fixture assembly is also equipped with a multi-channel temperature probe, which is used for array-level multi-point temperature measurement with a sampling frequency of not less than 100Hz.

4. The apparatus according to claim 3, characterized in that, The main body of the sealed cavity is a rectangular shell of 5mm thick 316L stainless steel, with an inner diameter of 1000mm×800mm×200mm. Metal flanges are retained at the top and bottom for installing the condenser and vacuum-liquid injection interface. A 300mm×200mm rectangular window is machined on both the front and back sides. The windows are surrounded by sealing grooves with a width and depth of 5mm and embedded with fluororubber O-rings. A 20mm thick tempered glass observation window is installed inside the window and fixed by a stainless steel pressure plate and quick-release bolts. The metal wall ensures a safe internal pressure of 0.3MPa, and the transparent window is used to provide visual observation of boiling. The top of the chamber is equipped with an explosion-proof membrane or safety valve, with a set burst pressure of 0.35MPa, which is used to release pressure in case of system abnormality and ensure experimental safety. The bottom of the chamber is designed with a 5° tilt angle, and a drain valve is set at the lowest point to facilitate the complete discharge of cooling medium.

5. The apparatus according to claim 4, characterized in that, The heat exchanger uses a non-contact heat exchanger to condense the steam at the top of the chamber into liquid. The cooling water pipe is coaxially connected to the steam outlet of the circulation channel. The steam condenses in the Ø2×100 cm316L pipe, and the cooling water flows through the external Ø10×110 cm pipe, forming a counter-current heat exchange. The condensation pipe adopts a spiral design, and the condensate relies on its own weight to return at a 5° inclination angle at the bottom, and is circulated externally by a pump. Cooling medium, which is the same type of coolant used in the actual working conditions of the radiator, is used for heat transfer and insulation; The vacuum-injection module is used to extract air from the sealed cavity and inject coolant. The circulation channel is used to connect the sealed cavity, heat exchanger, and vacuum-liquid injection module to maintain media circulation; it is connected to the sealed cavity through the vacuum-liquid injection interface and to the vacuum-liquid injection module through the KF50 interface.

6. The apparatus according to claim 5, characterized in that, The shapes of the sealed cavities include cylindrical and hexagonal. Types of heat exchangers include shell-and-tube, coil, and plate-fin.

7. The apparatus according to claim 6, characterized in that, The DC power supply system includes a full-bridge rectifier circuit, bus capacitors, leakage resistors, a full-bridge inverter circuit, an LCL filter, and voltage and current measurement devices. The input terminal of the full-bridge rectifier circuit is connected to the AC power grid, and the output terminal is connected in parallel to the bus capacitor to form a DC bus. A discharge resistor is connected in parallel across the bus capacitor to release DC bus energy during emergency stops. The full-bridge inverter circuit has a bus capacitor connected to the DC side and an AC grid connected to the AC side via an LCL filter to achieve energy feedback. LCL filters are used to control the power quality fed back to the grid; The voltage and current measuring device is used to collect DC bus voltage and output current, and send the sampled signals to the FPGA controller to form closed-loop control.

8. A method for testing the steady-state thermal resistance of an immersion phase change cooling radiator, applied to the apparatus described in any one of claims 1-7, characterized in that, include: Select the heat sink to be tested in the power module under test and arrange temperature measurement points; the temperature monitoring points of the heat sink to be tested are respectively set on the anode platform, cathode platform and the immersion cooling medium of the heat sink. Apply a positive pressure of 0.5 bar to the sealed cavity and maintain it for 1 hour; The vacuum-injection module performs a three-stage vacuuming process on the sealed cavity: first, it is evacuated to 1000Pa and held for 10 minutes; then, it is evacuated to 500Pa and held for 10 minutes; finally, it is evacuated to no more than 100Pa to ensure that the residual air inside the cavity is no more than 0.1%. Fluoride is injected by vacuum suction, with the liquid level 30mm above the upper surface of the radiator. Turn on the power module under test and apply a DC current using the DC current system; the heat generated by the power module under test causes the cooling medium to generate steam, and adjust the system exhaust valve and the magnitude of the conduction current to expel the residual air in the sealed cavity and the internal space of the phase change cooling test system; Record the temperature and pressure data of the sealed cavity. If the temperature change of the radiator platform does not exceed 1°C and the absolute pressure change of the cavity does not exceed 0.05 bar within 15 to 30 minutes, and the fluctuation of the cooling medium circulation flow rate is less than 2%, then the power module under test is determined to have reached thermal equilibrium. Under thermal equilibrium, the heat dissipation power of the heat sink under test is calculated based on the DC current of the power module under test; the steady-state thermal resistance of the heat sink under test is determined based on the heat dissipation power of the heat sink under test and the temperature at each temperature measurement point.

9. The method according to claim 8, characterized in that, The steady-state thermal resistance R of the heat sink under test sa_steady for: ; in, T A The temperature of the radiator anode platform under thermal equilibrium conditions. T K The temperature of the cathode mesa of the radiator under thermal equilibrium conditions. T f The temperature of the cooling medium submerged in the radiator under thermal equilibrium conditions.

10. A method for testing transient thermal resistance of an immersion phase change cooling radiator, applied to the apparatus of any one of claims 1-7, characterized in that, include: The power module under test reaches thermal equilibrium at a specific power level. The reference thermal resistance value under this steady state and the temperature at each temperature measurement point are recorded. In thermal equilibrium, a command is sent to the DC current source to cause a step change in the amplitude and power of the current passing through the power module under test in a very short time. At the same time, high-speed voltage, current and temperature data acquisition is started, and the temperature of each temperature measurement point at different times is recorded synchronously. Based on the collected transient data, the step response curve R of the transient thermal resistance as a function of time is obtained. sa (t): ;t represents the time of temperature acquisition; in, T A ( t )for t The temperature of the radiator anode platform at any given time, T K ( t )for t The temperature of the radiator cathode mesa at any given time. T f ( t )for t Temperature of the immersion radiator cooling medium at any given time, Δ P s The magnitude of power change before and after the step jump; The step response curve was fitted into an exponential function using the least squares method, and key parameters for evaluating the dynamic performance of the heat sink were extracted: thermal time constant and peak thermal resistance. By conducting step tests with different amplitudes and power increase / decrease directions, the peak thermal resistance and thermal time constant for different power amplitudes and change directions are obtained. After function fitting, the junction temperature fluctuation under any complex power waveform can be accurately predicted.

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