Experimental and numerical simulation on heat transfer characteristics of vertical cesium heat pipes

Medium-temperature cesium heat pipes’expensive cost and the active chemical properties of cesium medium, lead to a big difficulty for experimental study. Thus, it is of great significance to analyze and predict the start-up characteristics and internal phase-change heat transfer of the cesium heat pipe by numerical simulation. Firstly, the frozen start-up experiment of a vertical cesium heat pipe was carried out, and based on current heat pipe simulation models, an adaptive model with consideration of the linkage of evaporator and condenser was established by UDF. As proved, the maximum temperature difference of the heat pipe wall between the experimental and the numerical simulation result was less than 20K, and the sudden temperature drop at the end of the condenser was present realistically, which proved the accuracy of the model. Secondly, based on the frozen start-up experiment of a vertical cesium heat pipe with variable heating power, the evolution of wall temperature and internal phase distribution of the heat pipe during the start-up process was simulated, and the average difference of wall temperature was used to evaluate the temperature uniformity over the effective length. At last, with various evaporator lengths (200mm and 120mm), heating powers (1028.2W and 844.4W) and filling ratios (8.8%, 12% and 15%), the phase distribution, temperature distribution and pressure distribution were compared and analyzed in simulation. The optimum matching condition of the evaporator length and the filling ratio was obtained by considering of the effective working length, temperature uniformity, condensate stacking and dry-out phenomena in the evaporator. The content had great potential significance for the optimal design of heat pipes. © 2024 Chemical Industry Press Co., Ltd.. All rights reserved.