Experimental study on flow and heat transfer of high prandtl number fluid along helical cruciform single rod

A novel type of fuel assembly made up of the helical cruciform fuel element has been utilized in the design of a fluoride-salt-cooled high-temperature reactor (FHR) named FuSTAR. The range of the Prandtl number for fluoride salt (FLiBe) is between 12 and 15. The experiment using fluoride salt at high-temperature conditions is challenging to conduct. Dowtherm A, a heat transfer fluid, is chosen as the flow working medium for this study based on the scaling criteria. The high Prandtl number fluid experimental loop for flow and heat transfer is established by Xi'an Jiaotong University. The flow and heat transfer experiment along the helical cruciform single rod is performed by this loop. The experiment has a Prandtl number range of 12–15 and a Reynolds number range of 500–10000. Different inlet temperatures have the same friction coefficient at the same Reynolds number, and this friction coefficient increases with the mass flow rate. The flow empirical correlations are fitted and compared to the correlations in the references. With a relative error of less than 15%, the experimental data and Cheng correlation had a satisfactory agreement. In addition, research is experimentally done on the effects of mass flow rate, heating power and inlet temperature on heat transfer characteristics. Heat transfer empirical correlations are fitted. The uncertainty of direct and indirect measurements is shown. The experimental results have good repeatability within the uncertainty. The experimental results presented in this work can serve as a basis for the numerical simulation of helical cruciform single-rod flow and heat transfer. In the tested Prandtl number and Reynolds number range, the empirical correlation can forecast the heat transfer coefficient and friction coefficient of high Prandtl number fluid.