Numerical Investigation of Inter-Pipe Coupling and Adaptive Heat Redistribution in a Parallel High-Temperature Potassium Heat Pipe

A parallel high-temperature heat pipe (PHTHP) using potassium as the working fluid is proposed, and its thermal and flow responses under non-uniform thermal loading and an idealized single-pipe failure condition are numerically investigated. A three-dimensional Volume of Fluid (VOF) model incorporating evaporation–condensation phase change and wick capillary effects is developed. Its prediction of the axial wall temperature distribution is compared with experimental data for a single straight potassium heat pipe, yielding a root-mean-square error of 4.47 K. The thermal and flow characteristics of the proposed configuration are then investigated under symmetric operation, non-uniform heat loads, idealized single-pipe failure, and adiabatic-section bending conditions. Under symmetric operation, the two pipes exhibit nearly identical temperature, pressure, and vapor velocity distributions, indicating a symmetric and stable response. Under a 10% heat-load deviation, the inter-pipe pressure difference was approximately 50 Pa, and the relative difference in equivalent thermal resistance was 4.6%. Under an idealized single-pipe failure condition, the equivalent thermal resistance of the failed pipe increases to 2.49 times that of the normally operating one, and the model predicts vapor flow from the normally operating pipe to the failed pipe under the pressure difference between their evaporator sections. Under bending conditions, bending modifies the local vapor temperatures at the bend cross-section and the inlet of the adiabatic section. Despite this local redistribution, the equivalent thermal resistance of the bent pipe remains only slightly higher than that of the straight pipe. These results characterize the thermal and flow responses of the PHTHP under the investigated disturbances and provide a basis for further optimization of high-temperature heat pipes.