The wind test on heat loss from three coil cavity receiver for a parabolic dish collector

The heat loss from cavity receiver in parabolic dish system determines the efficiency and cost effectiveness of the system. A modified three coil solar cavity receiver of inner wall area approximately three times of single coil receiver, is experimentally investigated to study the effect of fluid inlet temperature (Tfi=50 degrees C to 75 degrees C) and cavity inclination angle (theta = 0 degrees to 90 degrees) on the heat loss from receiver under wind condition for head on wind and side on wind velocity at 3 m/s. Overall it was found that the natural and forced convection total heat loss increases with increase in mean fluid temperature. The combined heat loss decreases sharply with the increase in cavity inclination and observed to be maximum for horizontal position of receiver and minimum with the receiver facing vertically downward for all investigations. The maximum heat loss in wind test (V=3m/s) is 1045 W at theta=0 degrees cavity inclination at mean fluid temperature 68 degrees C and minimum at 173 W theta=90 degrees at 53 degrees C. Total heat loss from the receiver under wind condition (V=3m/s) is up to 25% higher (1.25 times at 0 degrees inclination) than without wind at mean fluid temperature similar to 70 degrees C and minimum 19.64 % (1.2 times at 90 degrees inclination) in mean temperature similar to 50 degrees C. In horizontal position of the receiver (theta=0 degrees), the total heat loss by head on wind is about 1.23 times (18% higher ) as compared to side on wind (at fluid mean temperature similar to 70 degrees C). For receiver facing downward (theta=90 degrees), for head-on wind, total heat loss is approximately the same as that for side-on wind

Numerical investigation of semiempirical relations representing the local Nusselt number magnitude of a pin fin heat sink

Heat transfer augmentation study using air jet impingement has recently attained great interest toward electronic packaging systems and material processing industries. The present study aims at developing a nondimensional semiempirical relation, which represents the cooling rate (Nu) in terms of different geometric and impinging parameters. The spacing of the fin (S/dp) and the fin heights (H/dp) are the geometric parameters, while the impinging Reynolds number (Re) and nozzle‐target spacing (Z/d) are the impinging parameters. During the plot of the Nusselt profile, three vital secondary peaks are observed due to local turbulence of air over the heat sink. To incorporate this nonlinear behavior of the Nusselt profile in developing nondimensional empirical relations, the Nusselt profiles are divided into different regions of secondary rise and fall. Four different sets of the semiempirical relation using regression analysis are proposed for Z/d ≤ 6, H/dp ≤ 4.8 with S/dp ≤ 1.58, S/dp > 1.58 and for Z/d > 6, H/dp > 4.8 with S/dp ≤ 1.58, S/dp > 1.58. These empirical relations benefit the evaluation of the cooling rate (Nu) without any experimentation or simulation

Variations in gas properties in laminar micro-convection with entrance effect

The present work investigates the influence of property variations of air in laminar forced convection with entrance effect. Two-dimensional micro-sized geometry (with axisymmetry) with constant wall heat flux boundary condition is considered to predict flow behaviour and thermal development. The continnum-based conservation equations are numerically solved to account for non-rarefaction scaling effects due to variations in fluid properties. At the microscale, results for Nusselt number show significant deviation from conventional theory that does not consider additional mechanisms that surface. The effect of property variation in Graetz problem for low subsonic flow is also studied.© Elsevie

A comparative study between the conventional and advanced biomass pretreatment methods applied on the Napier Grass used as a biomass

This paper presents a comparative analysis of the traditional and advanced pretreatment methods on the Napier Grass used as a biomass. It is a perennial C-4 type grass belongs to a sugarcane family, also called as Pennisetum Purpureum. It is found in abundance all across the world and traditionally used as a cattle feed stock in India.The author made an attempt for better effectiveness of the Napier Grass processing towards better productivity by using various pretreatment methods viz: Spectrophotometry, High Performance Liquid Chromatography, Enzyme Hydrolysis and Sonication.Napier Grass has lignocellulosic fibers with structural carbohydrates that requires pretreatment and enzymatically saccharified before they fermented into monomeric sugars and biofuel. The experimentation is carried out to examine the release of structural carbohydrate from Napier Grass using dilute acid pretreatment. In order to accelerate the process, the protein-rich fungus biomass Rhizopus Oligosporus has been added to the crude Napier Grass juice.It has been observed that, if green processed Napier Grass is treated with 5% concentrated sulfuric acid for a time span of 45 min at 120 °C, that results to yield the highest concentration of glucose from hemicellulose and cellulose with the highest quantum of xylose.The experimental result shows an increase in monomeric sugar that released from Napier Grass fibers after enzymatic saccharification process and the xylose and glucose concentrations achieved to 85.5% by dry weight of Napier grass

The Wind Test on Heat Loss from Three Coil Cavity Receiver for a Parabolic Dish Collector

The heat loss from cavity receiver in parabolic dish system determines the efficiency and cost effectiveness of the system. A modified three coil solar cavity receiver of inner wall area approximately three times of single coil receiver, is experimentally investigated to study the effect of fluid inlet temperature (Tfi=50°C to 75 °C) and cavity inclination angle (θ = 0° to 90°) on the heat loss from receiver under wind condition for head on wind and side on wind velocity at 3 m/s. Overall it was found that the natural and forced convection total heat loss increases with increase in mean fluid temperature. The combined heat loss decreases sharply with the increase in cavity inclination and observed to be maximum for horizontal position of receiver and minimum with the receiver facing vertically downward for all investigations. The maximum heat lossin wind test (V=3m/s) is 1045 W at θ=0° cavity inclination at mean fluid temperature 68 °C and minimum at 173 W θ=90° at 53°C. Total heat loss from the receiver under wind condition (V=3m/s) is up to 25% higher(1.25 times at 0° inclination) than without wind at mean fluid temperature ~70°C and minimum 19.64 % (1.2 times at 90° inclination) in mean temperature ~50 °C . In horizontal position of the receiver (θ=0°), the totalheat loss by head on wind is about 1.23 times (18% higher ) as compared to side on wind (at fluid mean temperature ~ 70°C). For receiver facing downward (θ=90°), for head-on wind, total heat loss is approximately the same as that for side-on wind