P.K. Nagarajan

Experimental investigation of a semi circular trough solar water heater

This paper studies the experimental analysis of a semi circular trough absorber solar water heater with baffles for improving the outlet water temperature. To increase the contact time of water with solar radiation and decreasing the flow rate of water baffles are kept in the absorber at a distance of 0.1 m. Studies are conducted for different flow rates of water in the absorber and flow rates increased by 2, 4, 8 and 16 times the base value of 0.133 kg/min. Results show that there is an increase in the outlet water temperature by 66.5 and 50°C with respect to inlet temperature during summer and winter, respectively, with an average inlet temperature of 34°C at minimum mass flow. The maximum water temperature during summer and winter conditions are found as 65 and 60°C respectively. Also, results show that the percentage increase in temperature of outlet water and average water temperature depends on solar intensity.

Geometrical variations in solar stills for improving the fresh water yield—A review

AbstractWater consumption by humanity is one of the major yardsticks to assess its civilization. Humans depend on groundwater sources for drinking. Some of these underground water sources cannot be used for drinking due to pollution. To solve the issues related to drinking water, several methods are employed, and a promising one is solar desalination. This paper communicates a review of different geometrical shapes of solar still. The present study concludes that the geometry in the solar still significantly influences the yield of fresh water.

Theoretical analysis of a triangular pyramid solar still integrated to an inclined solar still with baffles

Abstract This paper presents the theoretical analysis of a triangular pyramid solar still integrated to an inclined solar still with baffles. The performance of the solar still depends on water mass inside the basin. The yield of triangular pyramid solar still is increased by integrating it to an inclined solar still with baffles. Analytically, the water mass inside the basin is increased from 20 to 100 kg. Theoretical results show that the increase in water mass decreases the yield from 6% to 46% during the daytime, whereas due to thermal energy storage at higher mass, the yield during the nighttime increases from 46% to 86% with integration. Similarly, a triangular pyramid solar still is theoretically analysed for its performance.

Experimental Validation of Fresh Water Production Using Triangular Pyramid Solar Still with PCM Storage

In the study work effect of PCM on the triangular pyramid solar still was experimentally investigated for the climatic condition of Chennai. Experimental studies were conducted and the use of PCM on storage was compared with a solar still without PCM and the PCM used is paraffin wax. The latent heat energy storage is increased with the use of paraffin wax while the energy stored is utilized during the absence of solar radiation by rejecting its heat through the basin to water for further evaporation. The temperatures of various elements of the solar still were measured using a thermocouple. Results show that there is an increase in productivity of 20% when compared to the solar still without PCM.

Enhancing the thermal performance of Al2O3/DI water nanofluids in micro-fin tube equipped with straight and left-right twisted-tapes in turbulent flow regime

ABSTRACT This article communicates the thermal performance, heat transfer rate, and friction factor of Al2O3/DI water nanofluids at different concentrations in a micro-finned tube with tube helical inserts for different twist ratios. The thermal performance, heat transfer coefficient, and friction of the present study is also compared with a plain tube for validation. From the study, it is identified that the micro-finned tube with tube insert performance is higher as compared with a plain tube. Similarly, an empirical relation for Nusselt number (Nu) and friction factor (f) is estimated for straight twisted tube and left-right combination. The deviation between experimental and theoretical values for left-right twist and straight twist is found as 3 and 7% for Nusselt number and 7 and 9% for friction factor, respectively. Similarly, while analyzing the thermal performance, it was found that the maximum performance achieved was with a micro-fin tube with left-right twist with nanofluid concentration of 0.2%.

Effect of forced cover cooling technique on a triangular pyramid solar still

Abstract In the present study a triangular pyramid solar still is theoretically analysed by flowing air over the entire surface of the glass from the top to analyse the improvement in yield of fresh water. The effect of water mass and wind velocity was theoretically analysed. The results show that there is a significant improvement in the yield of fresh water to about 10.1 kg/m2 with a maximum velocity of air (U = 40 m/s) at a least water mass of 20 kg inside the basin. For practical cases the yield of fresh water depends on naturally occurring wind velocity and the results show that the improvement in yield is 104% with an increase in velocity from 0.5 to 4 m/s.

Experimental evaluation of friction factor and heat transfer enhancement of twisted tape inserts using TiO 2 –water nanofluids

This paper studies the experimental evaluation of TiO2 nanofluids in enhancing the heat transfer rate and friction factor on a micro-finned tube fitted with twisted tape inserts. Results show that the enhancement in heat transfer and pumping power completely depends on the concentration ratio of nanoparticles, pitch ratio and the type of pitch. Comparisons were made with the previous study with different operating parameters such as twist ratio and twist type. Viscosity of nanofluid increases with an increase in the concentration, which leads to increased pressure drop and pumping power. For the Reynolds number (Re = 4000), the maximum performance ratio was found as 2.1, 2, for concentration of 0.1 and 0.05, respectively. The addition of microfin arrangement inside the circular tube enhanced the performance ratio with minimum concentration of TiO2 nanofluid.

Experimental study on thermal conductivity of solution combustion synthesized MgO nanoparticles dispersed in water and ethylene glycol (50:50) binary mixture

In this present investigation, experiments were conducted on the magnesia nanoparticles (8–18 nm) synthesized by the solution combustion method, which was dispersed in the binary mixture of water-ethylene glycol (50:50) to prepare stable MgO–water-ethylene glycol (50:50) nanofluids through continuous 26h ultrasonication. The effect of nanoparticle concentration (0 to 0.2 vol%) and temperature (25°C to 60°C) on the thermal conductivity of the nanofluids was investigated. The results clearly indicate that an increase in the nanoparticle concentration increases the thermal conductivity of the nanofluid. Similarly the thermal conductivity of the nanofluid increases with increase in temperature. The enhanced thermal conductivity in the nanofluids may be due to either or both, the Brownian movement and the nano-interfacial layering. The maximum enhancement of 16% was obtained at 0.2 vol% nanoparticle concentration and at 60°C. An accurate correlation, modeling the thermal conductivity as a function of nanoparti...