Shobhana Singh

Design parameters for concentrator assisted solar distillation system

Analytical expressions for the water temperature of an active solar distillation unit with collectors and concentrators have been derived in terms of system and climatic parameters. It is analytically shown that the efficiency of the system with a concentrator is higher than that with a collector.

Analytical thermal modelling of multi-basin solar still

Based on energy balances for different components of a multi-basin solar still, namely, the basin-liner, the water mass and the glass cover, analytical expressions for water and glass temperatures have been derived in terms of climatic and design parameters of the system. It is inferred that the daily yield is a maximum for the least water depth in each basin

Analytical expression for thermal efficiency of a passive solar still

Abstract Using energy balance equations for the different components of a passive solar still (namely, glass cover, water mass and basin liner), the effect on its thermal efficiency of water flowing over the glass cover with uniform velocity has been studied analytically. The efficiency is found to increase due to the water flow at higher depths of water in the basin. The result is validated by the experimental results of other authors.

Design criteria for an active biogas plant

The design criteria for thermal heating of an active, fixed-dome type biogas plant are presented. The effects of the heat exchanger and collector panel have been incorporated in the thermal analysis. The thermal efficiency of the system can be optimised by increasing the flow rate of the working fluid between the heat exchanger and the collector loop.

Performance evaluation of solar dryer system for optimal operation: mathematical modelling and experimental validation

An analytical moisture diffusion model which considers the influence of external resistance to mass transfer is developed. The methodology to determine constant and variable moisture diffusion coefficients, Deff is proposed. A laboratory model of mixed-mode solar dryer is constructed to perform 16 experiments for different performance dependent variables under simulated indoor conditions. The potatoes (Solanum tuberosum) of Kufri Safed variety have been chosen as the test food product. The range of variables investigated is absorbed thermal energy (150–750 W/m2); air mass flow rate (0.009–0.022 kg/s); loading density (1.08–4.33 kg/m2) and sample thickness (5–18 mm). The efficiency results have been analysed to identify the value of each process variable leading to optimal operation of dryer. The study reveals that dryer with sample thickness of 8 mm and loading density of 4.33 kg/m2 can operate optimally for absorbed energy of 450 W/m2 and air mass flow rate of 0.017 kg/s.

Thermal Testing Methods for Solar Dryers

Solar food drying is a complex heat and mass transfer phenomena which depend on a number of drying process-dependent parameters such as operating conditions and characteristics of the food product to be dried. The variation in these parameters significantly affects the overall performance of the dryer system. Since commercial growth and acceptance of any solar dryer system momentously depend on its performance guarantee, the development of a standard methodology for their thermal testing has become necessary. The standard testing method not only provides better performance management of the dryer system but allows the manufacturers to achieve competitive efficiency and good product quality by comparing the available designs. In this chapter, an extensive review of solar dryer performance evaluation has been carried out. Furthermore, the chapter describes the existing testing procedures for the most common designs of solar dryers and the related practices used in the measurement, evaluation, and description of overall performance, including a variety of food product dried in scientific investigations.

Nonlinear whistler wave model for lion roars in the Earth’s magnetosheath

In the present study, we construct a nonlinear whistler wave model to explain the magnetic field spectra observed for lion roars in the Earth’s magnetosheath region. We use two-fluid theory and semi-analytical approach to derive the dynamical equation of whistler wave propagating along the ambient magnetic field. We examine the magnetic field localization of parallel propagating whistler wave in the intermediate beta plasma applicable to the Earth’s magnetosheath. In addition, we investigate spectral features of the magnetic field fluctuations and the spectral slope value. The magnetic field spectrum obtained by semi-analytical approach shows a spectral break point and becomes steeper at higher wave numbers. The observations of IMP6

Parametric CFD Analysis to Study the Influence of Fin Geometry on the Performance of a Fin and Tube Heat Exchanger

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Testing method for thermal performance based rating of various solar dryer designs

plasma waves and magnetometer experiment reveal the existence of short period magnetic field fluctuations in the magnetosheath. The observation shows the broadband spectrum with a spectral slope of −4.5 superimposed with a narrow band peak. The broadband fluctuations appear due to the energy cascades attributed by low-frequency magnetohydrodynamic modes, whereas, a narrow band peak is observed due to the short period lion roars bursts. The energy spectrum predicted by the present theoretical model shows a similar broadband spectrum in the wave number domain with a spectral slope of −3.2, however, it does not show any narrow band peak. Further, we present a comparison between theoretical energy spectrum and the observed spectral slope in the frequency domain. The present semi-analytical model provides exposure to the whistler wave turbulence in the Earth’s magnetosheath.

New approach for thermal testing of solar dryer: Development of generalized drying characteristic curve

Heat transfer and pressure loss characteristics of a fin and tube heat exchanger are numerically investigated based on parametric fin geometry. The cross-flow type heat exchanger with circular tubes and rectangular fin profile is selected as a reference design. The fin geometry is varied using a design aspect ratio as a variable parameter in a range of 0.1-1.0 to predict the impact on overall performance of the heat exchanger. In this paper, geometric profiles with a constant thickness of fin base are studied. Threedimensional, steady state CFD model is developed using commercially available Multiphysics software COMSOL v5.2. The numerical results are obtained for Reynolds number in a range from 5000 to 13000 and verified with the experimentally developed correlations. Dimensionless performance parameters such as Nusselt number, Euler number, efficiency index, and area-goodness factor are determined. The best performed geometric fin profile based on the higher heat transfer and lower pressure loss is predicted. The study provides insights into the impact of fin geometry on the heat transfer performance which help escalate the understanding of heat exchanger designing and manufacturing at a minimum cost.