Numerical and experimental study on heat transfer and flow features of representative molten salts for energy applications in turbulent tube flow

Abstract

This article investigated the heat transfer performance and flow friction of the molten salts in turbulent tube flow, where four salts including Hitec, Solar Salt, NaF-NaBF4, and FLiNaK were studied. A computational model was developed to analyze the flow and heat transfer features of the salts in the tube, and experiments were conducted to test the heat transfer performance of a representative salt Hitec in the tubes of a salt-oil heat exchanger. Comparison of simulation results with the experimental data shows that the average errors are smaller than ±4%, which validates the simulation model. Based on the model, firstly the influences of heat flux uniformity at the tube outer wall were examined. The results show that the non-uniform wall flux can lead to local high-temperature region but influences little on the flow friction coefficient and the heat transfer performance. Then, the model was utilized to investigate the friction and heat transfer features of the salts under broad ranges of the temperature and the velocity. Comparisons of the simulated heat transfer results with Hansen's, Sider-Tate's and Gnielinski's correlations show that the largest errors can reach +25%, +13% and-15%, respectively. Furthermore, the errors between the simulated friction coefficients and the Filonenko's correlation are smaller than ±2%, which indicates that this correlation is suitable for predicting the friction of the salts. Finally, to predict the heat transfer performance more accurately for these representative salts, a new correlation was developed. It was found that the errors between all simulation results and the proposed correlation are smaller than ±5%, while the corresponding values for 80% experiment data of three salts are also lower than ±5%. The current study can offer beneficial results and correlation for the applications of liquid salts in energy systems.

Effects of interface layer on the thermophysical properties of solar salt‐SiO 2 nanofluids: A molecular dynamics simulation

“…The temperature profile is then calculated by time averaging. The heat flux in the Z direction J can be calculated by Equation (8).…”

“…5 Molten salts are widely used in CSP systems 6 due to their low vapor pressure, high latent heat, wide operating temperature range, 7 and low price. 8 However, the relatively low SHC (<1.6 J/g K) and TC (<1 W/m K) of molten salt limit the heat storage and transfer efficiency. 9 In order to further improve the efficiency and reduce the initial investment of the CSP system, it is necessary to develop new HTFs with the desired thermophysical properties.…”

Convective heat transfer characteristics of molten salts flowing in complex flow structures: Experimental studies and progress

“…Qiu等人 [24] , 2019 鉴于此, 作者团队 [23] 在前期研究中搭建了大型熔 盐换热实验台, 系统研究了熔盐在普通的管壳式换热 器壳侧 [29] 、大小孔折流板换热器壳侧 [30] 、弓形折流板 换热器壳侧 [31] 、折流杆换热器壳侧 [32] 以及印刷电路板 换热器翼型肋片侧 [33]…”

Investigation Of Turbulent Convective Heat Transfer Of Molten Salt Flow Inside A Single-Bend Circular Pipe

“…Qiu et al [12] experimentally investigated the heat transfer performance and flow friction of four molten salts, i.e. Hitec, Solar Salt, NaF-NaBF 4 , and FLiNaK in turbulent tube flow under uniform and un-uniform heat flux.…”

“…Using a numerical method in simulating the heat transfer performance of HTFs instead of complicated, time consuming and expensive experimental methods is an appreciated approach especially if we consider the experimental limitations for such high temperature environments. Qiu et al [12] used a finite volume-based package to solve the governing equations numerically and validated the results with performed experiments for Hitec Salt and well-known empirical correlations. They used the Hansen's, Sider-Tate's, and Gnielinski's correlations for comparing the Nusselt number, with and Filonenko's correlation for friction coefficient.…”