One of the common water desalination apparatuses in freshwater regimes is Single Slope Solar Still (SSSS). This paper numerically investigated the heat transfer processes that took place inside the still. Also, implementing an optimization process to explore the best sustainable feed water preheating tank design. Comsol Software package (v 5.4) was utilized to develop and validate the 3D Mathematical model. The investigation included comparing four different tank designs namely are sphere, half-sphere, cone, and flat plate. In addition, the influence of altering the volume of the tank has been considered. The study revealed that the half-sphere design with a volume of 2.5 times the productivity of Conventional SSSS accompanied the highest recorded water temperature and productivity. The efficiency of the SSSS was enhanced by 27% in contrast to that without preheating.

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This work presented the numerical and experimental study of the thermal performance of a flat plate collector (FPC). This study focuses on analyzing the performance of (FPC) in the climatic conditions of Najaf and calculating the thermal energy produced by the collector for domestic use, which reduces the electricity consumption that Iraq is witnessing a severe shortage in its supply. Also, various working fluids (water, oil engine, ethylene glycol-water mixture) were tested to determine the best working fluid that improves the collector’s efficiency. The experiments were performed in Najaf, Iraq (32° 2’ N / 44° 18’ E) on January 9, 2019. The simulation study of the (FPC) is performed by COMSOL Multiphasic 5.3 software. The numerical results were validated with experimental results and there was good convergence between them. The results showed that the average daily efficiency of the solar collector (FPC) was 37.17%, and the highest outlet water temperature of the collector was 57.1Co. The collector achieved a useful cumulative useful heat during the day of about 3.3557 MW, this contributes to reducing the use of electricity and achieving the required economic feasibility of use (FPC). Finally, the engine oil gave better results in improving efficiency compared to other working fluids.

The flow of the wind near an absorber of a trough collector is analyzed. Since this absorber loss useful heat into the ambient, it is necessary to reduce that heat. The common strategy of reduction is the use of a vacuum tube. The maintaining of vacuum is difficult due to air leak or glass fracture led to find another replacement for this strategy. The idea of the present work is to put a half circular disc in front of the receiver in order to reduce the air velocity near the tube and reduce the heat transfer process. The flow is analyzed in the area to find the streamlines of flow and the behavior of air for a different air velocities and trough orientations. The analysis is done by using COMSOL Multiphysics program V4.4. The data show that the overall air velocity is reduced near the receiver as predicted.

The consumption of energy for cooling is an important issue, especially in subtropical climates where there are high temperatures and dry weather in the summer; this climate forces homeowners to use mechanical-electric cooling and ventilation. The main advantage of passive cooling is to minimize energy demands which are required to achieve thermal comfort in buildings, especially with climates exhibiting high ambient temperatures. This paper presents a detailed literature review and concept breakdown for passive cooling and ventilation in building by offering the fundamental principles of the techniques of passive cooling and ventilation. Moreover, the status of passive cooling developments along with state-of-the-art research is critically reviewed in this paper. Furthermore, the article focuses on Buoyancy air-driven ventilation. Solar control techniques are explained and classified along with techniques for heat modification and dissipation. This paper offers insight into the design considerations of different passive ventilation systems and presents recommendations for future work to achieve cost-efficient, comfortable living. Moreover, novel systems are reviewed and discussed to better understand the role of Phase Change Material (PCM) in passive cooling systems.