ALBERT

Description: The effects of thermal separators within the evacuated tubes of a water-in-glass solar water heater (SWH) were numerically investigated using the commercial computational fluid dynamics (CFD) software ANSYS fluent. To validate the three-dimensional (3D) model, an experiment was performed for the passive operation of the SWH for a fortnight period, of which 3 h of recorded data was selected. The Boussinesq's approximation was employed, and the respective solar irradiance and ambient temperature profiles were incorporated. A maximum deviation of only 2.06% was observed between the experimental and numerical results. The model was then adapted for the case where thermal separators are inserted within the evacuated tubes of the SWH and both cases were run for two tilt angles, 10 deg and 40 deg. The temperature and velocity profiles within the evacuated tubes were analyzed alongside the temperature contours, thermal stratification, and overall thermal efficiency of the SWH. At a 40 deg tilt, without thermal separators, the flow streams within the evacuated tubes are restrained, and a chaotic thermal behavior was observed, thereby restricting thermal distribution to the water stored in the SWH tank. A lower tilt angle (10 deg) provided a more desirable thermal distribution. With thermal separators, however, the tilt angle preference was reversed. A faster and more uniform thermal distribution was achieved within the water tank, with a sizeable reduction in the thermal stratification at a 40 deg tilt. The overall thermal efficiency of the SWH was improved by 4.11% and 4.14% for tilt angles of 10 deg and 40 deg, respectively.

Description: Greenhouse drying shows a significant role in the bulk level of drying. In the present setup, a greenhouse dryer operating under natural convection mode was designed and fabricated. The sensible heat storage concept was applied to the bed of the drying chamber. Four different beds, namely, gravel bed, ground bed, concrete bed, and black painted gravel bed was being selected for the comparative heat transfer analyses of the proposed setup. The maximum heat gain takes place at the black painted gravel bed conditions, i.e., 53%, while for concrete bed, gravel bed, and ground bed, it is 33%, 49%, and 29%, respectively. Hence, black painted gravel bed condition is strongly recommended for maximum heat storage. The proposed setup was used for drying of tomato flakes in black painted gravel bed condition. It has been found that the moisture content in the tomato flakes has been removed from 96% to 9.10% in 13 h. The average drying efficiency of the proposed greenhouse dryer is found to be 23.49%. The comparative analysis of the performance evaluation has been done with other investigators, and it was found that the drying rate of the proposed setup shows superior performance as compared with others. The design of the proposed greenhouse setup with black painted gravel bed condition is strongly recommended for small-scale industries and farmers.

Description: This research demonstrates scale-up studies with the development of concentrating and nonconcentrating solar reactors employing suspended and supported TiO2 for the degradation of herbicide isoproturon (IPU) with total working volume of 6 L. Novel cement beads were used as support material for fixing the catalyst particles. In the case of nonconcentrating slurry reactor, 85% degradation of IPU was achieved after 3 h of treatment with four number of catalyst recycling, whereas nonconcentrating fixed-bed reactor using TiO2 immobilized cement beads took relatively more time (10 h) for the degradation of IPU (65%) due to mass transfer limitations, but it overcame the implication of catalyst filtration post-treatment. The immobilized catalyst was successfully recycled for ten times boosting its commercial applications. High photon flux with concentrating parabolic trough collector (PTC) using fixed catalysis approach with same immobilized catalyst substantially reduced the treatment time to 4 h for achieving 91% degradation of IPU. Working and execution of pilot-scale reactors are very fruitful to extend these results for a technology development with the present leads.