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[en] The heat transfer and entropy generation analysis upon the single-phase flow of antifreeze and water (50:50) mixture with solution combustion-derived oxomagnesium nanoparticle (volume concentration, φ = 0.05, 0.2, 0.6%) through a micro-fin tube equipped with snug fit twisted tapes (twist ratio, Y = 6, 8, 10) are investigated. The Nusselt number and friction factor enhancement are attributed towards the enhancement in the thermo-physical properties of the nanofluid, micro-fin tube geometry and the twisted tape twist ratio. The maximum Nusselt number, friction factor and performance evaluation criteria are achieved corresponding to Y = 6, φ = 0.6%. At φ = 0.6%, the Bejan number values lesser than 0.5 signify the domination of frictional entropy generation over thermal entropy generation. Therefore, the optimal Reynolds number of 7600, 7900 and 8000 for Y = 10, 8 and 6 is the limit till which the 0.6% concentrated nanofluid is deemed efficient. In addition to this, the nanofluid density measured before and after the test runs signifies the maximum particle loss at 0.6% volume concentration and lower twist ratio due to the spiral and centrifugal effects. The enhanced particle size observed based on the DLS measurements taken before and after the fluid flow test runs signifies the impact of centrifugal and spiral flow effects on the fluid molecules. The Nusselt number and friction factor correlations are predicted based on the measured data.
[en] This paper studies the experimental and exergy analysis of solar still with the sand heat energy storage system. The cumulative yield from solar still with and without energy storage material is found to be 3.3 and 1.89 kg/m2, respectively for 8-h operation. Results show that the exergy efficiency of the system is higher with the least water depth of 0.02 m (mw = 20 kg). Competitive analysis of second law efficiency shows that the exergy efficiency improves the system by 30% than conventional single slope solar still without any heat storage. The maximum exergy efficiency with energy storage material is found as 13.2% and it is less than the conventional solar still without any material inside the basin.