Heat-Transfer Characteristics of Liquid Sodium in a Solar Receiver Tube with a Nonuniform Heat Flux

Jing Liu,Xianliang Lei,Yongqing He

doi:10.3390/en12081432

Jing Liu, Xianliang Lei + Show 1 more

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https://doi.org/10.3390/en12081432

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Abstract

This paper presents a numerical simulation on the heat transfer of liquid sodium in a solar receiver tube, as the liquid sodium is a promising heat-transfer candidate for the next generation solar-power-tower (SPT) system. A comparison between three mediums—solar salt, Hitec and liquid sodium—is presented under uniform and nonuniform heat-flux configurations. We studied the effects of mass flow rate (Qm), inlet temperature (Tin), and maximum heat flux (qomax), on the average heat-transfer coefficient (h) and the friction coefficient (f) of the three mediums. The results show that the h of liquid sodium is about 2.5 to 5 times than other two molten salts when Tin is varying from 550 to 800 K, Qm is 1.0 kg/s, and qomax is 0.1 MW/m2. For maximum heat fluxes from 0.1 to 0.3 MW/m2, the h of liquid sodium is always an order of magnitude larger than that of Hitec and Solar-Salt (S-S), while maintaining a small friction coefficient.

Highlights

Compared to the parabolic trough, Fresnel and dish collectors, the solar-power-tower (SPT) plant has the remarkable advantages, such as lower electricity cost, large-scale power generation and higher efficient thermodynamic cycles [1,2,3]
We present a numerical simulation on the heat transfer of liquid sodium under nonuniform heat flux
The heat-transfer characteristic of liquid sodium is compared with solar salt and Hitec in a the circumferential increased by about 2 ◦ K

Summary

Introduction

Compared to the parabolic trough, Fresnel and dish collectors, the solar-power-tower (SPT) plant has the remarkable advantages, such as lower electricity cost, large-scale power generation and higher efficient thermodynamic cycles [1,2,3]. The SPT is equipped with a large number of heliostats on the ground, each with a tracking mechanism that accurately reflects the reflection of sunlight onto the receiver at the top of a tall tower. In which only half of the surface of the tube is exposed to solar irradiation. This may bring about many problems, such as aggravating the plastic deformation of the receiver tube, facilitating degradation of the selective absorptive coating and decreasing the allowable solar heat flux [4,5]. The liquid metal as the promising candidate for the exposed cylindrical heat absorber of SPT has been proposed [6]

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