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The present work investigated thermal performance and heat transfer characteristics of a solar parabolic trough collector using Al2O3/DI‐H2O nanofluids. Nanofluids of varying concentrations (0.05% ϕ ≤ 0.5%) with mass flows (0.0083–0.05 kg/s) were considered for turbulent regime (2401 ≤ Re ≤ 7202) analysis. Experiments were carried out as per ASHRAE 93(2010) standards. By thermal performance analysis using Al2O3 nanofluid, it was understood that the collector efficiency improved up to 56% at a maximum volume concentration of ϕ = 0.5% and flow rate of 0.05 kg/s. The heat transfer study comparing Al2O3 nanofluid with pure water showed appreciable reduction in temperature gradient and surface temperature of the absorber. The heat transfer characteristics such as Nusselt number and friction factor relating to Reynolds number fits the experimental and predicted data and found within the limits of ±5.35% and ±9.61% for Nusselt number and friction factor respectively. Moreover, a similar empirical correlation was developed for collector efficiency, which was identified to be within the limit of ±1.02%. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1149–1159, 2018

Heat generated during the friction stir welding (FSW) process is of complex nature and plays a vital role in influencing the quality of the fabricated joints. In this experimental research, an thermo mechanical process model was formulated to estimate the values of peak temperatures generated during the employment of FSW tools with four different pin geometries (namely cylindrical, taper cylindrical, square and triangle) for joining of AZ80A Mg alloy flat plates, to understand their significant role in influencing the size of the grains, their mechanical strength and in the quality of the joints. The peak temperature values of the formulated thermo mechanical process model are found to be consistent with that of the actual experimental results and exhibited relatively very small variation It was observed that the joints fabricated by taper cylindrical pin geometry was found to possess very fine sized grains, due to the generation of ideal peak temperature (ie., 348 0 C which is nearly 81-82% of the melting temperature of AZ80A Workpiece).

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IntroductionGreater growth of population and industries results in shortage of fresh water. Earth is almost covered with a larger water source and smaller land mass. People used to drink large amount of water for their thirsty need. Water available in the form of rivers, lakes cannot be consumed directly without pre-processing, as these need some purification process in order to remove bacteria and undissolved salts. In early days the possible method of getting pure water is heating the brackish water and condensing them back to get fresh water by burning fossil fuels. Due to the exhaustion of coal, crude oil and increases in global warming, the evolution of using renewable energy for getting fresh water evolved during the late 20th century. One of the best energy source applied is solar energy. Source of energy from sun is mostly environmental friendly and non polluting clean energy source. Basin type still is the most aged process of producing fresh water [1][2][3][4][5][6][7][8][9][10]. The fresh water conversion rate from the solar still system is predominantly depends on the solar intensity. The basin water temperature increases continuously due to heat energy emitted from the sun in the form of solar intensity. After reaching the boiling point of water, the water evaporates and it condenses on the solar still condenser cover. The various techniques employed in solar still, to raise the temperature of water and hence increases the productivity was studied from the detailed literatures reviews of Ravishankar et al. [11], Kabeel et al. [12] and Manokar et al. [13][14][15]. From the detailed literature studies it is clear that water temperature can be improved by either feeding waste warm water or pre heat the water by incorporating the different solar collectors or concentrators. Gupta et al. [16] theoretically analyzed the intermittent flow of waste warm water to the double basin solar still similarly same analyses was done by Yadav et al. in single basin solar still [17]. Sodha et al. [18] and Tiwari et al. [19] experimentally investigated the performance of solar still utilizing the warm water from the industry. Tiwari et al. [20] keep up a higher temperature difference between the water and collector cover by increasing the water temperature by flowing waste hot water in the basin and decrease the collector cover temperature by flowing the cold water above the surface of collector cover. This would results in increase in both evaporation and condensation

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