Mixed convection heat transfer of molten salt outside coiled tube

Abstract Mixed convection heat transfer of molten salt outside coiled tube in cylinder tank was experimentally reported with Reynolds number 418–2175 and Prandlt number 5.7–8.8. Nusselt number of salt outside coiled tube was significantly higher than that inside tube, and its tendency had good agreement with available heat transfer correlations for fluid crossing tube. The heat transfer between salt and coiled tube was enhanced by forced convection, and its Nusselt number rose as Reynolds number rising. Based on available heat transfer correlations and experimental data, experimental correlation for forced convection was proposed by considering Prandtl number ratio, and it fitted with experimental data with maximum deviation of 10.1%. Natural convection played important role in heat transfer outside coiled tube for large temperature difference, and its effect increased as Reynolds number dropping. In addition, experimental correlation for mixed heat convection with combination of natural convection and forced convection was proposed, and it fitted with experimental data better than other correlations, and maximum deviation was reduced to 8.5%.