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. 2021 Jul 8;7(7):e07489.
doi: 10.1016/j.heliyon.2021.e07489. eCollection 2021 Jul.

An optimisation study of a solar tower receiver: the influence of geometry and material, heat flux, and heat transfer fluid on thermal and mechanical performance

Hashem Shatnawi  1   2 , Chin Wai Lim  1 , Firas Basim Ismail  3 , Abdulrahman Aldossary  2
Affiliations

An optimisation study of a solar tower receiver: the influence of geometry and material, heat flux, and heat transfer fluid on thermal and mechanical performance

Hashem Shatnawi et al. Heliyon. .

Abstract

The solar receiver is considered the cornerstone of the solar tower power system. In particular, it receives high-temperature heat flux rays, and extracts the maximum heat energy to be transferred to the heat transfer fluid, while minimising any thermal and mechanical stresses. Reducing the solar receiver size helps to reduce the loss of spillage; consequently, the thermal stress increases. Using a solar receiver with inserted triangular longitudinal fins enhances the heat transfer as well as strengthens the receiver tube. This study aims to optimise the number of fins, heat flux aiming point, heat transfer fluid, nanoparticle effect with molten salt as the base fluid, and type of receiver material. Non-uniform heat flux with the cosine and Gaussian effects have been considered. When the number of fins (N) increases, the maximum temperature (Tmax) decreases and the heat transfer is enhanced. When N = 20, Tmax = 656.4 K and when N = 1, Tmax = 683.55, while the efficiency for N = 1 is greater by 3% compared to when N = 20. The cosine distribution of heat flux has a higher maximum temperature than the Gaussian distribution by 29% and is 102% higher in receiver efficiency. The thermal efficiency when the heat flux is aimed at the middle point of the receiver is higher by 10% compared with a lower or upper aiming point. Using Al2O3 nanoparticles with a concentration of 0.5 wt.% increases the thermal efficiency by 14% more than when using pure molten salt when Re = 38000. Using liquid sodium is not required to monitor the peak heat flux, and by adding triangular fins the displacement and thermal stress are 6.5 % lower compared to a smooth receiver.

Keywords: External receiver; Liquid sodium; Longitudinal internal fins; Nanofluid; Solar tower power; Thermal stress.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Receiver dimensions and fins distributions.
Figure 2
Figure 2
Heat flux distribution with neglecting the Gaussian effect.
Figure 3
Figure 3
Heat flux distribution with considering the Gaussian effect.
Figure 4
Figure 4
Finer mesh in 3D receiver tube.
Figure 5
Figure 5
Validation of Nusselt numbers for a smooth tube, Re = 14000 to 38000.
Figure 6
Figure 6
Temperature gradient at the receiver outlet, with Re = 14000.
Figure 7
Figure 7
Average Nusselt number with different fins number.
Figure 8
Figure 8
Maximum temperature with different fins number.
Figure 9
Figure 9
Peak Contour temperature.
Figure 10
Figure 10
Receiver efficiency with different numbers of fins, N = 1,7 &20.
Figure 11
Figure 11
3D-Non-uniform heat flux distribution of the receiver tube.
Figure 12
Figure 12
Axial inward heat flux along the receiver tube with Gaussian effect.
Figure 13
Figure 13
Maximum temperature for Cosine and Gaussian heat fluxes.
Figure 14
Figure 14
Receiver thermal efficiency with different heat flux distrbuiton.
Figure 15
Figure 15
Different angle spans of Gaussian non-uniform heat flux distribution.
Figure 16
Figure 16
Receiver thermal efficiency with different aiming angles.
Figure 17
Figure 17
Temperature distribution from the heated side, Re = 14000.
Figure 18
Figure 18
The maximum temperature at Re = 14000.
Figure 19
Figure 19
Maximum temperature with different Re. with fixed internal diameter.
Figure 20
Figure 20
The maximum temperature at Re = 14000 with different receiver thicknesses.
Figure 21
Figure 21
The maximum temperature with different receiver materials at Re = 14000.
Figure 22
Figure 22
The maximum temperature for different receiver materials.
Figure 23
Figure 23
Temperature contour with different receiver materials at Re = 14000.
Figure 24
Figure 24
Average Nusselt number for nanofluid with different weight ratios.
Figure 25
Figure 25
Heat transfer coefficient with different weight ratios.
Figure 26
Figure 26
Thermal efficiency with different weight ratios.
Figure 27
Figure 27
Maximum Temperature distribution from the heated side, Re = 14000.
Figure 28
Figure 28
Temperature contour at Re = 14000.
Figure 29
Figure 29
Maximum temperature with different weights ratios.
Figure 30
Figure 30
Validating liquid sodium and Nusselt number, compared with [44].
Figure 31
Figure 31
Maximum temperature with different heat transfer fluid, at Re = 14000.
Figure 32
Figure 32
Heat transfer coefficient with different heat transfer fluids. Effect of different HTF with same flow rate.
Figure 33
Figure 33
Maximum temperature with different HTF, with constant Re & Q.
Figure 34
Figure 34
Temperature gradient for different HTF.
Figure 35
Figure 35
Receiver length with distance between clips.
Figure 36
Figure 36
Total displacement of the receiver with ends encastred.
Figure 37
Figure 37
Total displacement with distance between clips = 1, 2, and 5m.
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References

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