Forced convection heat transfer characteristics in a circular tube with low-melting-point quaternary nitrate

doi:10.19799/j.cnki.2095-4239.2020.0020

Abstract

Abstract:

The forced convection heat transfer characteristics of a low-melting-point quaternary nitrate in a tube-type heat exchanger are studied under different conditions to verify the applicability of the classical convection heat transfer correlation in this case. Based on the heat transfer experiment of the molten salt in the inner tube and the heat transfer oil on the shell side of the tube-type heat exchanger, the inlet and outlet temperatures of the molten salt and heat transfer oil in the test section of the tube-type heat exchanger are obtained. Further, the total heat transfer coefficients of the molten salt and heat transfer oil are obtained. Using the Wilson separation method, the convective heat transfer coefficient on the molten salt side is obtained from the total heat transfer coefficient to study the convective heat transfer characteristics of molten salt in a circular tube. Results show that the Reynolds number of the low-melting-point quaternary salt is 1 × 10⁴—5 × 10⁴, the Prandtl number is 4.9—15.5, and the total heat transfer coefficient of the molten salt and the heat transfer oil is 670—1300 W·m^-2·K^-1 in the fully developed turbulent region. The convective heat transfer coefficient on the molten salt side is 2900—7800 W·m^-2·K^-1. Subsequently, the correlation between convection and heat transfer in case of the low-melting-point quaternary salt in the turbulent section of the tube is obtained according to the experimental data. By comparing the experimental data with the classical convection correlations, the classical convection correlation is observed to be still applicable to convection heat transfer in a tube containing low-melting-point quaternary nitrate. This study provides reference data for the practical application of molten salt in solar thermal power generation.

Key words: molten salt, forced convection, heat transfer, turbulent section

CLC Number:

TM 121

ZHANG Chunyu, GUO Hang, WU Yuting, ZHANG Cancan, YE Fang, MA Chongfang. Forced convection heat transfer characteristics in a circular tube with low-melting-point quaternary nitrate[J]. Energy Storage Science and Technology, 2020, 9(4): 1091-1097.

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名称	单位	拟合公式	适用范围
比热容c_p_,s	J·(g·K)^-1	c_p_,s=1.77878-7.55155×10^-4t	220 ℃≤t≤450 ℃
导热系数λ_s	W·(m·K)^-1	λ_s=3.83349-0.02857t+8.07852×8.07852×10^-5t²-7.24056×10^-8t³	250 ℃≤t≤500 ℃
黏度η_s	Pa·s	η_s=0.44845e^(621.738/^t⁾ ×10^-3	220 ℃≤t≤450 ℃
密度ρ_s	kg·m^-3	ρ_s=2.22744-9.43393×10^-4t	220 ℃≤t≤450 ℃

名称	单位	拟合公式
比热容c_p_,o	kJ·(kg·K)^-1	c_p_,o=0.0034t+1.7051
导热系数λ_o	W·(m·K)^-1	λ_o=-1.744×10^-5t+0.1243
黏度ν_o	10^-6m²·s^-1	ν_o=48.328e^-^t^/21.403+0.8431
密度ρ_o	kg·m^-3	ρ_o=-0.6311t+1026.75

参数	范围	误差
熔盐进口温度	252.1～404.5 ℃	±0.1 ℃
熔盐出口温度	247.2～395.4 ℃	±0.1 ℃
导热油进口温度	124.6～145.2 ℃	±0.1 ℃
导热油出口温度	131.4～165.3 ℃	±0.1 ℃
导热油流量	0.465 kg/s	±1.2%

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