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The thermal management problem of IGBT is becoming more and more prominent, and it is urgent to develop a new cooling technology with high efficiency, stability and flexibility. Based on the main problems and bottlenecks in the current IGBT module cooling, was conducted a detailed analysis and evaluation of the widely used IGBT cooling technologies, as well as spray cooling, jet impingement cooling technology and micro-channel cooling technology, which are the hot spots of the current research. It shows that compared with other cooling technologies, micro-channel cooling technology, especially microchannel flow boiling cooling technology, has the advantages of compact structure, strong heat transfer capacity, high heat transfer coefficient, less working fluid charge, and good temperature uniformity performance, which have great development prospects in the field of thermal management of electronic devices. Thus, in this paper, it was proposed that microchannel flow boiling cooling is an optimal solution to the thermal management of new electronic devices, which provides an important reference for the design and application of IGBT module heat sinks.

Immersion cooling is widely used for thermal management of servers. The two-phase immersion cooling, which transfers heat by boiling, possesses efficient temperature control ability under intensive heat generation. In the process of temperature control through boiling, the generation and transportation of bubbles play a crucial role in calculating the heat-transfer capacity. Therefore, it holds immense significance to obtain a profound understanding of the mechanisms underlying bubble formation and detachment. Currently, numerous mechanistic explanations and empirical correlations have been proposed to elucidate the various parameters of bubbles during the boiling process. These findings were considered to be valuable references when selecting appropriate boiling media and designing efficient heating surfaces. To comprehensively present the progress of bubble formation and heat transfer in the boiling system, the forces exerted on the bubbles are highlighted in this article. A meticulous review of bubble-force analysis and correlation formulae pertaining to various relevant parameters (e.g., nucleation sites density, bubble growth rate, bubble growth period, and detachment frequency) was conducted. This review article was also expected to provide a novel foundation for further exploration of enhanced boiling heat transfer. [ABSTRACT FROM AUTHOR]

As the carriers of massive data, data centers are constantly needed to process and calculate all kinds of information from various fields and have become an important infrastructure for the convenience of human life. Data centers are booming around the world, accompanied by the problems of high power consumption and poor heat dissipation. One of the most effective solutions to these problems is to adapt a two-phase liquid immersion cooling technology, which is a more energy-saving and efficient method than the traditional cooling methods; the reason for this is mainly that in two-phase liquid immersion cooling technology, the heat transfer caused by the phase change of liquid coolants (electronic fluoride liquids) helps to cool and improve the temperature uniformity of electronic components. However, the requirements for the electronic fluoride liquids used in two-phase liquid immersion cooling systems are strict. The thermophysical properties (saturated vapor pressure, density, surface tension, viscosity, thermal conductivity and latent heat of vaporization, etc.) of the liquid coolants play a very key role in the heat dissipation capacity of two-phase liquid immersion cooling systems. However, it is not always easy to obtain new electronic fluoride liquids under many actual conditions and reasonable prediction models of their thermophysical properties could contribute to the preliminary screening of the coolants. Thus, the prediction models of their key thermophysical properties (saturated vapor pressure, saturation density, surface tension, viscosity and thermal conductivity) are reviewed, and the accuracy and practicality of these prediction models in predicting the thermophysical properties of electronic fluoride liquids (FC-72, HFE-7100 and Novec 649) are evaluated. This work will provide a valuable reference for actual engineering applications. [ABSTRACT FROM AUTHOR]

Some alternative refrigerants with excellent environmental performance often have different flammable limits. When refrigerant leaks, the external space may have a certain explosion risk if the refrigerant is not diffused timely. To understand the leakage and diffusion characteristics of the refrigerant, an improved gas leakage model was proposed in this paper, and the accuracy verification of the improved model was developed. Based on the above works, taking R290 as the research object, the variation law of the field strength between the leaked gas and external space and the influence of different initial leakage pressures on the field strength characteristics were analyzed. The simulation results showed that when the initial leakage pressure was 2 MPa, the R290 gas entered the external space as a supersonic jet, the gas underwent continuous expansion and compression processes in the near-field area and a Mach disk was formed within the flow area. During this process, parameters, such as the temperature, pressure, velocity and density of the leaked R290 gas, changed dramatically, and then the gas gradually returned to room temperature and normal pressure through interaction with the external space. The flammable area formed by the leaked R290 was mainly concentrated in the local flow area below the leak hole, and the existence of the Mach disk caused the R290 high concentration area to increase. With the increase in the initial leakage pressure, the distance from the Mach disk to the leak hole and the circumferential diameter of the Mach disk increased, and the flammable area increased slightly in the horizontal direction, whereas the flammable area increased significantly in the vertical direction. [ABSTRACT FROM AUTHOR]

In the application of pulsating heat pipes (PHPs), the lengths of the adiabatic sections are usually determined by the distance between the heat source and the heat sink, and have important effects on the performance of PHPs. However, there was little research on the effect of the adiabatic section lengths on the performance of PHPs. In this work, a new transient numerical model was proposed to investigate the transient flow and the heat transfer for PHPs with various adiabatic section lengths of 60, 120, 180, and 240 mm. Based on the numerical results, the flow and the heat transfer characteristics of the PHPs were analyzed. It was found that the flow velocities in the PHP with different adiabatic lengths increased with the increase in the heat input, and the mean velocity was calculated to be in the range of 0.139–0.428 m/s, which was consistent with the previous experimental results. The start-up performance of the PHP was better with shorter adiabatic section length. Furthermore, the thermal resistances of the PHPs with different adiabatic section lengths were calculated to analyze the effects of the adiabatic section length on the performance of the PHP. The results showed that when the heat input was 20 W, the PHP with the adiabatic section of 60 mm showed the lowest thermal resistance, whereas the PHP with longer adiabatic section length presented lower thermal resistance at high heat input (≥25 W). [ABSTRACT FROM AUTHOR]