Water is essential for food security, industrial output, ecological sustainability, and a country’s socioeconomic progress. Water scarcity and environmental concerns have increased globally in recent years as a result of the ever-increasing population, rapid industrialization and urbanization, and poor water resource management. Even though there are sufficient water resources, their uneven circulation leads to shortages and the requirement for portable fresh water. More than two billion people live in water-stressed areas. Hence, the present study covers all of the research based on water extraction from atmospheric air, including theoretical and practical (different experimental methods) research. A comparison between different results is made. The calculated efficiency of the systems used to extract water from atmospheric air by simulating the governing equations is discussed. The effects of different limitations, which affect and enhance the collectors’ efficiency, are studied. This research article will be very useful to society and will support further research on the extraction of water in arid zones.

The purpose of this paper is to estimate the quantity and quality of the useful energy that could be converted to work, this analysis was carried out based on the energy and exergy analysis by using the first and second laws of thermodynamics. This paper study the effect of varying the ambient temperature on the performance of the turbine. Results showed increasing in exergy destruction in the turbine solely and in each of its three components(Air compressor, Combustion chambers and the gas turbine) with increasing in ambient temperature. Also results showed by keeping the load unchanged, the exergy destruction are bigger in higher ambient temperatures than in lower ones. The exergy destruction concentrated in the combustion chambers, where the percent of exergy destruction in the combustion chambers to the total exergy destruction in the plant was(87%) followed by the air compressor(9%) and the lower exergy destruction was in the gas turbine(4%).

Heat transfer enhancement employing an elliptical tube inside a circular tube to increase the heat transfer rate without increasing in pressure drop is investigated. The flow rate inside the narrow is in the range of Reynolds number 10,000 to 100,000. Commercial software is used to solve the governing equations (continuity, momentum, and energy) by adopting a finite volume method (FVM). The electrical heater is connected around the circular tube to apply uniform heat flux (3000 W/m2) as a boundary condition. The volume concentrations are in the range of 0.25% to 1% with different TiO2 nanoparticle diameters in the range of 27 nm to 50 nm dispersed in water. The results indicate that the elliptical annulus tube can enhance heat transfer and friction factor by approximately 19% and 6% than the circular tube respectively. Results show that the heat transfer enhancement is significantly increasing as the volume concentrations increase and the nanoparticles size diameter decrease.

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Flat plate solar collector (FPSC) is popular for their low cost, simplicity, and ease of installation and operation. In this work, FPSC thermal performance was analyzed. It's compared to diamond/H2O nanofluids. The volume percentage and kind of nanoparticles are analyzed numerically that validation with experimental data available in the literature. The hot climate of Iraq is employed to approximate the model. The numerical study is performed by using ANSYS/FLUENT software to simulate the case study of problem. Due to less solar intensity after midday, temperatures reduction. The greatest collector thermal efficiency is 68.90% with 1% ND/water nanofluid, a 12.2% increase over pure water. The efficiency of 1% nanofluid is better than other concentrations because of a change in physical properties and an increase in thermal conductivity. Since the intensity of radiation affects the outlet temperature from the solar collector and there is a direct link between them, this increases the efficiency of the solar collector, especially around 12:30 pm at the optimum efficiency.

Increasing temperature of cell’s surface considers one of the most parameters that affected the performance of Photovoltaic thermal collector (PV/T). A numerical study aid by Ansys Fluent was employed in this study to invesitgate the performance of PV solar cell energy analysis under the same climatic condition of Sherqat-Iraq. A validated CFD model was used in this investigation. It was included six cases four concentrations of (Fe3O4/water) nanofluid, one employed pure water and one used non-cooling PV. The collector of PV/T contains an absorber plate made of Aluminium and serpentine pipe made of copper. The system worked under laminar regime at a constant flow rate (0.0075kg/sec). The results showed that the using of nanofluid as coolant increasing the overall efficiency of PV compared with the water-cooling and non-cooling PV solar cell. It was concluded that the highest thermal and electrical effeciencies are 19.5% and 55.45% respectively when using 1% volume fraction of nanofluid.

This study utilized Nanofluid as a cold fluid in evaluating the counter flow double tube heat exchanger, which was one meter long, had an outer diameter of 19 mm, and an inner diameter of 9.5 mm made from copper. Water was the basic fluid, with the size of 40 nm and a volume concentration of (0.5%)  and (1%), respectively, of CuO nanoparticles being added. At 2 L/min and 4 L/min and 6 L/min, the Nanofluid flows inside the inner tube. At 20°C, the Nanofluid enters the heat exchanger. The flow of hot water into the heat exchanger is 4 L/min through an annular space with an entry temperature of 65 °C. to achieve better heat exchanger performance, the experimental results will be compared to those obtained when using pure water. The improvement in performance with Nanofluid as a working fluid was discovered during experiment analysis. (40%) maximum heat exchanger effectiveness obtained at Nanofluid flow rate of 2 L/min has (0.5%) volume concentration ,effectiveness (54%) at (1%)  a volume concentration.