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Enhanced heat transfer performances of molten salt mixed convection in a vertical annular duct

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Abstract

The mixed convection heat transfer of upward molten salt flow in a vertical annular duct is experimentally and numerically studied. The heat transfer performances of mixed convection are measured under Reynolds number 2,500–12,000 and inlet temperature 300–400 °C, and Nusselt number of molten salt flow with cooled inner wall monotonically increases with buoyancy number. The mixed convection is further simulated by low-Reynolds number k-ε model and variable properties, and the heat transfer tendency from numerical results agrees with that from experiments. At low Reynolds number, the natural convection plays more important role in the mixed convection. As the buoyancy number rises, the thickness of flow boundary layer near the inner wall increases, while the effective thermal conductivity remarkably rises, so the enhanced heat transfer of mixed convection is mainly affected by the effective thermal conductivity due to turbulent diffusion.

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Abbreviations

c p :

Specific heat (J kg−1 K−1)

D :

Diameter (m)

D e :

Characteristic diameter (m)

g :

Gravitational acceleration (ms−2)

h :

Convective heat transfer coefficient (W m−2 K−1)

q :

Heat flux (W m−2)

r :

Radial coordinate (m)

T :

Temperature (K)

u :

Axial velocity (ms−1)

v :

Tangential velocity (ms−1)

x :

Axial coordinate (m)

β :

Volume expansion coefficient (−)

λ :

Thermal conductivity (W m−1 K−1)

ρ :

Density (kg m−3)

μ :

Viscosity (kg m−1 s−1)

v :

Kinetic viscosity (m2 s−1)

av :

Average

b :

Bulk

i :

Inner wall of annulus

in :

Inlet

o :

Outer wall of annulus

w :

Wall

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Acknowledgments

This paper is supported by National Natural Science Foundation of China (No. 51176206), National Science and Technology Support Program (No. 2014BAA01B01), and National 863 Program (No. 2013AA050503).

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Authors and Affiliations

  1. School of Engineering, Sun Yat-sen University, Guangzhou, 510006, China

    Jing Ding, Jianfeng Lu & Weilong Wang

  2. Academy of Building Energy Efficiency, Guangdong Provincial Key Laboratory of Building Energy Efficiency and Application Technology, Guangzhou University, Guangzhou, 510006, China

    Shiquan He & Jianping Yang

  3. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, China

    Shiquan He, Jing Ding, Jianfeng Lu, Weilong Wang & Jianping Yang

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  1. Shiquan He
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  2. Jing Ding
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  3. Jianfeng Lu
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  4. Weilong Wang
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  5. Jianping Yang
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Correspondence to Jianfeng Lu.

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He, S., Ding, J., Lu, J. et al. Enhanced heat transfer performances of molten salt mixed convection in a vertical annular duct. Heat Mass Transfer 50, 997–1004 (2014). https://doi.org/10.1007/s00231-014-1312-6

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  • DOI: https://doi.org/10.1007/s00231-014-1312-6

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