The current work aims to numerically investigate the impact of using (50% ZnO and 50% Al₂O₃) hybrid nanofluid (HNf) on the performance of convective heat transfer inside a horizontal wavy micro-channel. This issue represents a novel approach that has not been extensively covered in previous research and provides more valuable insights into the performance of HNfs in complex flow geometries. The conjugate heat transfer approach is used to demonstrate the influence of adding hybrid nanoparticles (50% Al₂O₃ and 50% ZnO) to pure water on the rate of heat transfer. The governing equations are numerically solved by using ANSYS FLUENT (2021 R2). The behaviors of convective heat transfer coefficient (HTC), Nusselt number (Nu) and pressure drop are presented under various volume concentrations of (1%, 2% and 3%) and Reynolds numbers (Re = 600, 1200 and 1800). The numerical results are validated against the experimental one, where the validation test shows a good agreement between them. The findings display that the highest HTC enhancement is reached at 59.5% when using a volume concentration of 3% and Re = 1800. The Nusselt number is increased with the rise in volume concentration of nanoparticles, where the value of the Nusselt number is improved by 42.25% at 3% volume concentration. The reduction in pressure is raised with an increase in volume concentration and $Re$. The results also show that the combination of dispersion characteristics, Brownian movement and nanoparticles leads to an improvement in the rate of heat transfer. It is concluded that $\text{Nu}$ and the behavior of heat transfer are considerably enhanced when using a hybrid nanofluid inside a wavy micro-channel.

This work involves an experimental study on the performance of automobile air-conditioning systems by adding Al₂O₃ nanoparticles to oil compressors to investigate their impacts on the enhancement of the speed cooling of refrigeration systems and to compare it with the system operated using only oil. The Al₂O₃ nanoparticles have been added to the oil compressor for different ranges of mass concentration (Ø = 0.1%, Ø = 0.15% and Ø = 0.2%). The stability of Al₂O₃ nanoparticles has been tested by direct observation for different time periods. The results indicated that the air conditioning system that operated by using Al₂O₃-oil was better than the system that operated with pure oil. For Ø = 0.2%, the results indicated that the cooling speed and the efficiency of the system operated with Al₂O₃-oil are increased by 13% and 18%, respectively, as compared to the pure oil system. This study shows that the thermos-physical properties of refrigerant oil are enhanced by 15% when Ø is increased.

It is common knowledge that phase-change materials are used for the purpose of thermal storage because of the characteristics that are exclusive to these materials and not found in others. These characteristics include a large capacity for absorbing heat and a large capacity for releasing heat when the phase changes; however, these materials have a low thermal conductivity. This paper presents the results of an experimental study that investigated the impact that nanoparticles of copper oxide had on reducing the temperature of solar panels. The phase change substance that was used was determined to be beeswax. The impact of adding nanoscale copper oxide at a concentration of 0.05% of the total mass of wax was investigated and compared to a reference solar panel that did not contain any nanoscale additions. The findings demonstrated that the incorporation of nanoscale copper oxide brought about a reduction of three °C in the plate's average temperature as well as a one percent improvement in its electrical efficiency. In cases where it seems that the use of nanoparticles might potentially enhance the performance of integrated solar energy systems that contain phase change.

This study numerically involves the performance of thermal insulation of different types of composite walls and roofs to demonstrate the best model that can be used for energy-efficient building construction in Iraq. The mathematical model is solved by building its code using the Transmission Matrix Method in MATLAB software. The weather data of 21st July 2022 in Baghdad City/Iraq is selected as a test day. The wall types are selected: the first type consists of cement mortar, brick, and gypsum, the second type consists of cement mortar, brick, gypsum, and plaster and the third type consists of cement mortar, brick, gypsum, air cavity, and sheathing timber. The roof types are chosen: the first type consists of reinforced concrete, gypsum, and plaster, and the second type consists of the precast concrete flag, river sand, tar, reinforced concrete, gypsum, and plaster. The obtained solutions are compared with previous studies for the same city but with different types of walls and roofs. The findings display that the second and third types of walls reduce the entry heat flux by 4% and 10% as compared to the first type of wall. Also, the results indicate that the second type of roof reduces the entry heat flux by 21% as compared to the first type of roof. The results confirm that the best models of walls and roofs in Iraq are the third and second types, respectively, as compared to other models and hence, the performance of insulation material strongly depends on the materials used while building them.