Preliminary Experimental Study Of High Temperature Molten Salt Heat Pipe

Heat pipes with simple structure and low manufacture cost is a kind of highly efficient heat transfer components, which has been widely used in aerospace, waste heat recovery, electronic cooling, solar energy and some other fields. When the heat pipe with Alkali metals as heat transfer fluid works, rupture of the heat pipe wall will leads to the leak of alkali metals to circumambient medium or air when strongly chemical reactions such as fire, explosion probably happened, which may cause huge losses and casualties. Leakage of toxic organic mediums as the heat transfer fluid of heat pipes may cause a similar losses in case of rupture of the pipe wall. In order to improve the comprehensive performance of heat pipe, this paper employs molten salts as heat transfer fluid of heat pipes, which is in explosive, inexpensive and environment friendly. Several kinds of heat pipes are developed with molten salt as the heat transfer working fluid. We set up the molten salt gravity heat pipe start-up performance test bench and do some start-up experiments.By start-up experiments of the 40 g mixed nitrate heat pipe and naphthalene heat pipe, we get different variations of the axial temperature of the heat pipe. The condensation section temperature of the mixed nitrate heat pipe can be raised to 130 ℃, it showed the mixed nitrate heat pipe is feasible. The result show that the start-up time of mixed nitrates heat pipe is shorter than the heat pipe of naphthalene and the mixed nitrates heat pipe is superior to the heat pipe of naphthalene in the stability. By start-up experiments of the different filling amounts mixed nitrate heat pipe, we get different variations of the axial temperature of the heat pipe. The temperature of the condensation section is reduced with the increase of the quality of the working fluid. The start-up performance is the best with 40 g working fluid.By mixed nitrate heat pipe inclination angle experiment, we get different variations of the axial temperature of the heat pipe. The optimum inclination angle for molten salt heat pipe is 50°in case of temperature of evaporation section kept lower than 400℃. The optimum inclination angle is 30°, when the temperature of evaporation section is 450℃. By start-up experiments of mixed bromide salt heat pipe、hitec heat pipe and solar salt heat pipe, we get different variations of the axial temperature of the heat pipe. The condensation section temperature of molten salt heat pipes do not change, the heat pipes do not start.This paper designs the Knudsen cavity and builds the experimental bench of the working fluid vapor pressure with simultaneous thermal analyzer. The vapor pressure of Zn、NaBr and mixed nitrate are measured. The vapor pressure formulas are fitted. The surface tension of mixed nitrate is measured by the tester of Physical properties. We obtain the variations of surface tension with temperature.