Experimental and numerical investigation on a hybrid high-temperature downhole thermal management system integrating liquid cooling and phase change material

•A high-temperature downhole HTMS integrating liquid cooling and PCM was proposed.•The temperature difference between the electronic and PCM was reduced by 51.9 °C.•The workable time was extended by 166 min compared to traditional solution.•The heat transfer enhancement mechanism was analyzed numerically.•The proposed system is promising for practical downhole applications. The downhole electronics must operate in an extremely thermal environment for several hours. Previous researches have proved that passive thermal management systems (PTMSs) are able to protect downhole electronics over extended durations. However, conventional PTMSs commonly suffer from a significant thermal resistance between the electronics and phase change materials (PCM), which restricting the efficient heat transfer to the PCM and consequently reducing the effective operating time. In this study, a hybrid thermal management system (HTMS) integrating liquid cooling and phase change thermal energy storage technique was proposed to enhance the internal heat transfer performance of downhole electronics and extend the operation duration. An active heat transfer channel was established between the electronics and PCM through liquid cooling system, and thus the generated heat was efficiently transferred and stored in PCM. The thermal performance of the proposed HTMS was investigated both experimentally and numerically. The accuracy of the numerical model was validated through experimental results, with a deviation lower than 6 %. The experimental results show that the temperature difference between the heat source and the heat storage module (HSM) was reduced by up to 51.9 °C, and the workable time was increased by up to 166 mins compared to the system without liquid cooling. The proposed HTMS exhibits superior heat transfer performance, which contributes to achieving a longer effective operation duration and holds extensive and profound application prospects in the field of thermal management for downhole electronic devices.