Abstract
Recently, there has been significant interest in the thermal performance of parabolic trough collectors. They are capable of operating and generating highly variable temperature ranges, which can be used in various applications. This paper, therefore, addressed the thermal performance model of using a parabolic trough collector under the radiation intensity level found in Budapest city, as well as the effect of inserting a hybrid nanofluid as the thermal fluid. First, a new modified hybrid nanofluid of alumina and tungsten oxide-based Therminol VP1 is used to enhance the thermal properties of the thermal fluid to be more efficient to use. This enhancement is performed under various volume concentrations and has a volume fraction of 50:50. Second, in order to demonstrate the effectiveness of the thermal element, mathematical energy balance equations were solved and simulated using MATLAB Symbolic Tools. The simulation is presented for two cases: one under a constant radiation intensity and the other under the radiation intensity level of Budapest. For both cases, the results of the dimensionless Nusselt number, heat transfer coefficient, pressure drop, exergy efficiency, and energy efficiency are described. The major findings show that a volume concentration of 4% (Al2O3 and WO3) based Therminol VP1 was the most efficient volume concentrations in both cases. For the first case, the maximum enhancement of the Nusselt number and the heat transfer coefficient are 138% and 169%, respectively. These results enhanced the thermal and exergy efficiencies by 0.39% and 0.385% at a temperature 600 K, flow rate of 150 L/min, and radiation intensity of 1000 W/m2. For the second case, the maximum exergy and energy values are recorded at midday under Budapest’s summer climatic conditions and reach 32.728% and 71.255%, respectively, under the optimum temperature of 500 K and flow rate of 150 L/min. Accordingly, the mean improvement in thermal and exergy efficiencies approximately equal to 0.25% at a high concentration, regardless of the season (summer or winter).
Highlights
The accelerated increase in the cost of electricity is associated with a deterioration in the level of fossil fuels, which coincides with a rise in demand, in addition to the various environmental problems
The obtained results showed high accuracy compared to the Sandia National Laboratory (SNL) results for the LS2 parabolic trough collectors (PTCs) model, which were determined by Dudley [44]
When the beam radiation intensity was taken to be 1000 W/m2, and the ambient temperature was 300 K, the results showed a decrease in the thermal efficiency with the inlet temperature increase
Summary
The accelerated increase in the cost of electricity is associated with a deterioration in the level of fossil fuels, which coincides with a rise in demand, in addition to the various environmental problems. Peng et al [22] numerically compared the thermal performance of a U-shaped evacuated tube resulting from the adding several nanoparticle oxides (CuO, Al2O3, and TiO2) to water. Sarafraz and Safaei [23] experimentally assessed the effect of graphene nanoplatelet-based methanol in evacuated tube collectors under various conditions Their results showed that using 0.1% wt of graphene–methanol nanofluid leads to an improvement in the thermal efficiency of the ETSC system of 95%. Abed et al [24] numerically compared the performance enhancements of PTC receiver tubes, which was achieved by adding various nanoparticles (TiO2, Al2O3, CuO and Cu) to water under a uniform heat flux boundary. The improvement effect of tungsten oxide nanoparticles is only mentioned as a mononanofluid for two solar application types; the evacuated tube [46] and the PTC [47]
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