Numerical investigation on heat transfer rate from the outside environment into the electronic compartment of the measurement-while-drilling tools

With the increase of drilling depth, a large number of high-temperature wells with bottom hole temperatures of more than 150°C appear. However, conventional measurement-while-drilling (MWD) instruments are no longer suitable. Therefore, it is necessary to design a new MWD instrument suitable for high-temperature downhole for a long time. Compared with other active refrigeration methods, a split-Stirling cryocooler is the best choice. In this paper, a new active cooling system is designed, based on the split-Stirling cryocooler. The heat transfer rate entering the instrument cabin of MWD from the external environment is calculated, and the effects of the heat transfer device, insulation material, circuit board, split-Stirling cryocooler, and working condition on heat transfer rate are discussed. The results show that the thermal conductivity of insulation material has a great influence on heat transfer rate. The thermal conductivity of the insulation material filled with the gap in the cabin must be small enough. Meanwhile, the influence of the length of the circuit board is greater than the height and width. If conditions permit, the double-layer circuit can be used. And the thermal power of the circuit board has no effect on the heat transfer rate entering the instrument cabin from outside.