Exergy evaluation of packed bed solar air heater

In view of above present investigation is planned with the following. The present investigation has been carried out with the following objectives: (1) To study performance of packed bed solar air heater for high porosity range and for different shapes of matrices. (2) Development of correlations for heat transfer coefficient and friction factor for packed bed solar air heater and its comparison with conventional design. (3) Exergy analysis of packed bed solar air heater. The present study involved outdoor experimental work for generation of heat transfer and friction data for flow in a packed bed solar air heater at different mass flow rates of air for various porosities and shapes of matrices. Data is also collected for conventional smooth duct under similar operating conditions for ensuring accuracy of experimental data. Six matrices had been tested for seven values of flow rates corresponding to flow Reynolds number of about 1000-4700 and data is collected under steady state condition. Ranges of parameters covered in this experimental investigation are as follows: Reynolds number, Re = 1000-4700 Porosity, P = 0.9614-0.9984 Number of layers, n = 3-6 It is found that in the entire range of Reynolds number, Colburn factor decreases with an increase of packing Reynolds number and volumetric heat transfer increased monotonically with a decrease in porosity. Also from the various matrices studied hexagonal shaped matrix performed lowest of all other matrices. Square shaped matrix performed best amongst the matrices studied. Following correlations have been developed for Colburn factor and friction factor in terms of porosity and operating parameters: J(h) = 0.1765[(1/nP)(0.6156))(p(t)/d(w))(0.1229)]Re-0.6631(p)-0.4767 f(p) = 2.0291[(1/nP)(0.3521))(p(t)/d(w))(0.0686)]Re-0.6759(p)-0.3897 Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.