The generation of entropy and mixed convection in a nanofluid-filled 3D wavy tank containing a rotating cylinder is investigated. The top wavy surface of the tank is heated and all vertical surfaces are assumed to be adiabatic, while the bottom horizontal surface remains isothermally cold. The tank contains a solid cylinder and is saturated with an Al₂O₃–water nanofluid. The numerical simulations using the FEM are performed for the Richardson number ($0.01\le Ri\le 100$), nanoparticle volume fraction ($0\le \varphi \le 0.04$) and number of oscillations ($0\le N\le 4$). The numerical results of the present work are given in terms of 3D streamlines, isotherms and local entropy generation, as well as average heat transfer and Bejan number. The results show that for low values of the Richardson number and oscillation, heat transfer enhancement can be achieved by increasing the nanoparticle volume fraction.

Air conditioners (ACs) are more commonly used nowadays in residential and commercial buildings to achieve thermal comfort in the summer season. Due to the high outside temperature, condenser pressure was highest and ultimately resulted in high electricity consumption. One of the ways to reduce the energy consumption of AC systems and increase cooling capacity is by reducing air temperature entering the condenser by using the evaporative cooling principle. This article presents an experimental and theoretical investigation of improving the performance of the conventional air conditioning unit supported by a direct evaporative cooling system to increase the cooling capacity and reduce the consumption of power in hot and dry climates. A window-type AC unit was implemented in the experiment where the AC system is modulated to provide a wide range of various weather conditions. The results show that using evaporative cooling assist enhanced the system to overcome the many challenges by which the refrigeration capacity was increased in the range of 10–20%. Also, the results show a decrease in outlet temperature by 6–10°C, and the power consumption was reduced by about 3%. MATLAB program was used to analyze different data that were obtained. The input parameters for this program are the inlet conditions such as the weather conditions of the located city, namely the outdoor dry temperature and the outdoor relative humidity. The effectiveness and cooling capacity were calculated based on the frontal air velocity and the inlet air temperature. A comparison between the experimental and theoretical work showed a good agreement, as the relative difference is less than 9%.