An improved numerical model based on the equivalent thermal conductivity method for downhole thermal management systems

The electronics in logging tools are susceptible to thermal failure due to the extreme thermal environment. Passive thermal management system (PTMS) has been proven to protect the electronics for several hours. In this paper, a numerical model based on the equivalent thermal conductivity method was developed to determine the transient temperature of downhole electronics. Compared with the traditional analytical model or numerical model considering only one single heat transfer process, the complex heat transfer in the logging tool were comprehensively considered through the proposed model. Briefly, the heat transfer processes in the vacuum bottle were theoretically calculated rather than empirically acquired, and the convective and radiative heat transfer inside the vacuum bottle was equated to the temperature -dependent thermal conductivity of air. In addition, the proposed numerical model was compared with experiments and previous numerical models to verify the accuracy of the model, and the temperature deviation of the electronics was within 5 degrees C. Moreover, the computational time was greatly reduced compared with the traditional three-dimensional numerical simulation process while ensuring the accuracy of calculation. Therefore, the proposed numerical model achieved both computational accuracy and efficiency, which was expected to be widely used in the development of PTMS for logging tools.