A numerical model coupling multiple heat transfer modes to develop a passive thermal management system for logging tool

Logging tools are subjected to increasingly extreme thermal environments due to the exploration of deeper wells. Previous studies have shown that passive thermal management systems have successfully protected electronics that operate in high ambient temperature environments for up to several hours. However, the percentage of the contribution from different heat transfer modes remains unclear, and the numerical models remain incomplete. To solve this issue, a 3D numerical model that couples all heat transfer modes was proposed for passive thermal management systems of logging tool. Unlike previous simplistic models, the one proposed here considers solid heat conduction, natural air convection, thermal radiation, and the phase change heat storage processes. The accuracy of the proposed model was verified by experiments. The experimental results showed that the maximum absolute errors and the average absolute error between the simulation and experiment were 8.61 degrees C and 3.02 degrees C, respectively. The maximum percentage error between the experiment and simulation using the proposed model was 4.71 %, compared to 6.59 % for the previous model. Importantly, the heat transfer process was described in detail by numerical simulations. The results showed that the absorbed heat of the phase change materials accounted for 72.7 %, which suppressed the temperature rise of the heat sources. In addition, the proportions of thermal conduction, convection and radiation in the total heat exchange were 93.89 %, 4.32 %, and 1.79 %, respectively.