Thermal insulation and shock shielding effects of PCM capsules using for downhole pulsed power source device

•PCM capsules are used for thermal insulation of deice in downhole.•Various stacking structures of PCM capsules are numerically studied.•Shock properties including wave, area, frequency are analyzed.•The staggered structure shows the best thermal shock shielding performance. Pulsed power sources (PPS) are commonly employed for the exploitation and extraction of shale oil in deep downhole environments. Nevertheless, the extreme conditions, such as high temperature and high pressure, pose significant challenges to the safe operation of PPS systems due to electronic failures. In this study, capsules filled with phase change material (PCM) under three layouts are proposed, aiming to provide thermal protection and shock shielding for PPS devices. Numerical methods are applied to PCM capsules, and the properties of PCM capsules are obtained through experimental measurements. Results show that the staggered stacking structure shows the best thermal protection performance, with a phase change duration 14.1 % longer than that of the double layer stacking structure. Additionally, considering the effect of the shock wave generated by the PPS, the shock properties of the ordered stacking thermal protection structure at different phase transition stages and different structures are discussed. The double layer stacking structure has a smaller shock area, and the extreme range of the peak shock wave is 34.89 kPa, which is only 0.5 times that of the single layer array, but its internal shock frequency is larger than the latter. As a result, the staggered stacking structure is recommended, considering both thermal protection and shock shielding features.