The aim of the present study is to analyze the performance of CuO nanofluids with water as the base fluid in the flat tube bent at 90°. The analytical analysis has been performed under different Reynolds number as well as nanoparticle volume concentrations. Various thermophysical properties, that is, density, thermal conductivity, viscosity, and specific heat capacity have been estimated with well-developed models of each, presented during previous studies carried out in the field of nanofluids. The simulation work has been performed with the help of the finite volume method. It was concluded from this study that heat transfer coefficient and Nusselt number of nanofluids at different volume concentrations between 0.1% to 0.5% v/v CuO is higher than that of the base fluids. The pressure drop obtained upon the use of nanofluids is found to be higher than the base fluid. The study also proves that nanofluids have a huge potential in playing an important role in decreasing sizes of heat transfer systems.

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The main aim of this study is to evaluate thermal performance and exergy analysis of a shelland-tube heat exchanger with a new technique called air bubble injection. The study has been carried out with different parameters such as flow rate, fluid inlet temperature, and different air injection techniques. The air has been injected at different locations such as the inlet of pipe, throughout the pipe, and in the outer pipe of the heat exchanger. Based on the results, the performance of the heat exchanger enhances with an increase in the flow rate and the fluid inlet temperature. The exergy loss and dimensionless exergy loss increase with a rise in the flow rate. The maximum and dimensionless exergy losses are obtained at a maximum flow rate of 3.5 l min −1 . With the air bubble injection in the heat exchanger, it has been observed that the temperature difference increases, which leads to an increase in the exergy loss. The injecting air bubbles throughout the tube section shows that minimum dimensionless exergy is 27.49% concerning no air injection.

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Nanofluids are great heat transfer carriers for collecting thermal energy in solar thermal applications. In the present study, a theoretical study of single‐slope solar still (passive type) has been carried out by incorporating CuO, Al2O3, Ag, Fe2O3, and SiC‐water nanofluids at different volume concentrations (0.02, 0.05, 0.08, 0.12, and 0.2). This analysis has been carried out with an optimum water depth of 0.02m as obtained from the experimental and theoretical studies. In order to validate the model, the experiments were conducted on solar still and then performance of still was compared. The analytical expression of the characteristic equation using Runga‐Kutta ODE, for passive single slope solar still was found to be in good agreement with experiments carried out in Patiala, India. The total deviation for both experimental and theoretical distillate output of a still for a day was found to be 12.24%. Daily production for Al2O3‐water‐based nanofluid was found to be (14.22%) higher than simple solar still without nanofluid, followed by CuO (10.82%), Ag (8.11%), Fe2O3 (7.63%) and SiC (7.61%).