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    Experimental investigation of the thermal efficiency of a new cavity receiver design for concentrator solar technology
    (Elsevier, 2024) Alkhalaf, Qusai; Lee, Daeho; Kumar, Raj; Thapa, Sashank; Singh, Amar Raj; Akhtar, Mohammad Nishat; Asif, Mohammad
    The most popular design for solar energy receivers that achieves great thermal performance is a cavity receiver. This study experimentally compared two novel shapes of cavity receivers: conical-cylindrical-conical (CCC) and double cylindrical, with conventional conical and cylindrical designs, to examine the effectiveness of solar energy receivers. The findings indicate that the CCC shape demonstrated a higher level of efficiency, as it performed better than all other shapes that were examined. Results emphasized the influence of radiation intensity on receiver efficiency, with all shapes exhibiting improved performance at higher intensities, maximizing at 1000 W/m2. Lower friction factors were desirable for minimizing heat losses and maximizing efficiency, resulting in values of 0.078, 0.09, 0.1, and 0.12 for CCC, conical, double cylindrical, and cylindrical shapes at a flow rate of 2 L/min, respectively. The temperature differences for CCC, conical, double cylindrical, and cylindrical shapes are computed as 6.4 degrees C, 5.7 degrees C, 5 degrees C, and 4.3 degrees C, respectively. The thermal efficiencies of the CCC, conical, double cylindrical, and cylindrical shapes are computed as 86.5 %, 81.5 %, 79.9 %, and 68.9 %, respectively, at a flow rate of 2 L/min.
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    Parametric optimization of an impingement jet solar air heater for active green heating in buildings using hybrid CRITIC-COPRAS approach
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2024) Kumar, Raj; Kumar, Sushil; Agbulut, Uemit; Guerel, Ali Etem; Alwetaishi, Mamdooh; Shaik, Saboor; Saleel, C. Ahamed
    This work aimed to optimize the parameters of discrete multi-arc shaped ribs (DMASRs) in a solar air heating system (SAHS) through multi-criteria decision-making techniques. In the experiment, the roughness parameters of DMASRs were varied to find the best parameter combination for optimal SAHS performance. The relative rib height (Hr /H) was varied from 0.025 to 0.047 , and the relative rib pitch (Pr /H) was varied from 0.58 to 3.1. The results obtained for the Nusselt number and friction factor, which determine the performance of the SAHS system, depend on the geometrical parameters of the roughness. The parameters of DMASRs did not show any discernible trend. Hence, a multi-decision criteria approach that uses criteria importance through inter-criteria correlation (CRITIC) and complex proportional assessment (COPRAS) hybrid techniques was employed to determine the best parameter combination for optimal performance. The novel aspect of this study includes the use of a hybrid method (experimental and analytical) to optimize the performance of SAHS roughened with DMASRs hindrance promoters and predictions of outcomes using a hybrid CRITIC-COPRAS approach. The experimental and analytical examination through the use of the hybrid CRITIC-COPRAS approach is an essential component of this research that contributes to the optimization of the design parameters of such SAHS. The finding demonstrated that when Re = 19000, Pr/H = 1.7, and Hr/H = 0.047 were reached, the SAHS obtained an optimal thermohydraulic performance of 4.1.