Experimental study on improvement of pool boiling cooling systems in dielectric liquid using honeycomb structures manufactured by additive manufacturing

Date

2024-1-23

Author

Malyemez, Muhammed Çağlar

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Maintaining new electronic devices within the permitted operating temperature ranges requires effective thermal management technologies. Microelectronic technology advancements have enabled silicon chips to be produced with smaller transistors. Additionally, as the number of transistors in microchips increases, their power consumption also increases. As a result, the heat flux that needs to be removed from these devices is constantly increasing. High heat flux is one of the most critical problems of thermal design engineers. The increase in heat flux is one of the most essential factors in developing electronic cooling technologies. Traditional cooling methods are insufficient for these high heat fluxes. Phase change-based thermal management methods are promising to remove high heat fluxes from electronic devices. Pool boiling is one of the most convenient multi-phase cooling systems in terms of applicability. This study includes experimental studies on improving the boiling pool cooling system using surface modifications fabricated using additive manufacturing. Surface modifications that cannot be produced with traditional manufacturing methods are made with the Selective Laser Melting method, aiming to optimize the design parameters. Surface modifications are manufactured from AlSi10Mg powder, and the thermal conductivities of the manufactured parts are determined as a result of material characterization tests. Pool boiling experiments are carried out in HFE-7100 liquid under saturated conditions and atmospheric pressure. These experiments are carried out in a controlled laboratory environment, temperature and pressure measurements are taken during the experiments, and imaging is performed with a high-speed camera. In this study, the pool boiling performances of twenty-five types of test pieces are evaluated. The manufactured surface modifications have a honeycomb structure with hexagonal openings. Also, some of these modifications have side square openings. During the experiments, the effects of surface roughness, size of hexagonal openings, modification height, length of side square openings, and distribution of repeating cells on the boiling performance are examined. In order to improve performance, it is aimed to increase the critical heat flux and heat transfer coefficient, eliminate the initial boiling hysteresis, and start the nucleate boiling regime at low temperatures. As a result of the experiments, these four goals are achieved, and significant improvements are observed. Thanks to the surface modification, boiling starts at a lower heat flux with a significant decrease of more than 10 °C in the surface temperature. While an increase of more than 3.48 times is observed for the critical heat flux, the maximum heat transfer coefficient improves by 2.56 times. These improvements are attributed to the increase of heat transfer and active nucleation areas, improvement of the capillary-assisted suction effect, and separation of liquid-vapor flow paths thanks to surface modifications. Based on the results obtained, optimization of design parameters is discussed. The combined use of the boiling pool cooling system and additive manufacturing methods offers promising solutions for electronic cooling.

Subject Keywords

Pool Boiling, Electronic Cooling, Selective Laser Melting, Critical Heat Flux Improvement, Heat Transfer Coefficient Improvement, Bubble Visualization, Capillary Assisted Suction, Liquid-vapor Flow Path Separation

URI

https://hdl.handle.net/11511/108703

Collections

Graduate School of Natural and Applied Sciences, Thesis