The performance of double-pass counter flow (model A) and double-parallel flow (model B) solar air heater with V-grooved absorber plate are numerically investigated. The mathematical models are written based on energy balance equations for each element of both models. The matrix inversion method is used to numerically solve the mathematical models for solar intensity (I = 350 − 950 (W/m2)), ambient temperature (Ta = 20 (°C)), mass air flow rate range of (ṁ = 0.02–0.09 (kg/s)), and opening angle of V-grooved absorber plate of (Ø = 60°). The results are presented in terms of: Air temperature rise, useful heat gain, thermal efficiency, and thermo hydraulic efficiency. Obviously when air mass flow rate increases, model (A) produces the highest air temperature rise, useful heat gain, and thermal efficiency. As air mass flow rate increases, the thermo-hydraulic of model (B) also increases while thermo-hydraulic efficiency of model (A) decreases from air mass flow rate (ṁ = 0.05, 0.06 and 0.07 (kg/s)) for solar intensities (350, 650, and 950 (W/m2)) respectively. In terms of thermal efficiency, the model (A) is more efficient than of model (B) by (26.8470 %, 27.8890 %, and 28.2496 %) for solar intensities (350, 650, and 950 (W/m2)) respectively. In terms of thermo-hydraulic efficiency, model (A) is more efficient than that of model (B) by (12.1046 %, 20.6830 %, and 25.1215 %) for solar intensities (350, 650, and 950 (W/m2)) respectively.

We experimentally compute the local heat transfer coefficient of blend refrigerant R-410A condensing inside horizontal rectangular multiport aluminium microchannels with hydraulic diameters equal to 0.52 mm and 1.26 mm. The refrigerant flows at near-critical pressure and the cooling air flows at high temperatures proper of hot climates. The experiments are conducted in a bespoke experimental facility and micro-foil sensors are used to measure the local condensation heat flux. The heat transfer coefficient is found to increase with the mass flow rate per unit area and the vapour quality and to decrease with the ambient temperature. Correlations available in the literature do not predict our experimental data satisfactorily because of our extreme operating conditions of high pressure and high cooling air temperature. A novel correlation is therefore obtained to successfully compute the Nusselt number for the condensing annular flow regime in our high pressure and high temperature conditions.

In low-latitude areas less than 10° in latitude angle, the solar radiation that goes into the solar still increases as the cover slope approaches the latitude angle. However, the amount of water that is condensed and then falls toward the solar-still basin is also increased in this case. Consequently, the solar yield still is significantly decreased, and the accuracy of the prediction method is affected. This reduction in the yield and the accuracy of the prediction method is inversely proportional to the time in which the condensed water stays on the inner side of the condensing cover without collection because more drops will fall down into the basin of the solar-still. Different numbers of scraper motions per hour (NSM), that is, 1, 2, 3, 4, 5, 6, and 7, are implemented to increase the hourly yield of solar still (HYSS) of the double-slope solar still hybrid with rubber scrapers (DSSSHS) in areas at low latitudes and develop an accurate model for forecasting the HYSS. The proposed model is developed by determining the best values of the constant factors that are associated with NSM, and the optimal values of exponent (n) and the unknown constant (C) for the Nusselt number expression (Nu). These variables are used in formulating the models for estimating HYSS. The particle swarm optimization (PSO) algorithm is used to solve the optimization problem, thereby determining the optimal yields. Water that condensed and accumulated inside the condensing glass cover of the DSSSHS is collected by increasing NSM. This process increases in the specific productivity of DSSSHS and the accuracy of the HYSS prediction model. Results show that the proposed model can consistently and accurately estimate HYSS. Based on the relative root mean square error (RRMSE), the proposed model PSO–HYSS attained a minimum value (2.81), whereas the validation models attained Dunkle’s (78.68) and Kumar and Tiwari’s (141.37).

In this study, three types of aerofoils were examined at various angles of attack and at a steady value then fluctuated of air flow. Then, the findings were compared to the XFOIL prediction results. The experimental and simulation results were consistent to some extent with the XFOIL prediction results. The shape of the chosen aerofoils was modified by making a slot through the blade the aerofoil and studying their effect on the aerodynamics of the modified shape. The slotted aerofoil shape was studied as it faced a fluctuated wind flow. The results revealed that the increase in angles of attack, the lift force increased and approximated its maximum value and then began to decrease with the slot. During the calculations, a case study for the number of elements was done to obtain the best mesh.The experimental and simulations were conducted by using ANSYS CFD at Reynolds number 10 6 and AOA equals (0°, 4°, 8°, 10°, 12°, 15°, 16°, 17°, 18°) for three shapes of aerofoils which are without a slot, two of which are symmetrical, NACA 0012 and NACA 0015, and one asymmetrical, which is NACA 4415. The slotted aerofoil (existence of an opening after 40% from the leading edge) which is the NACA 0015 aerofoil, was simulated.