Evaluation of Packed Bed Solar Air Heater with Wire Matrices : Performance Evaluation of Packed Bed Solar Air Heater with Wire Matrices

Solar air heaters are generally used for low to moderate thermal energy requirements. These systems are cheap and easy to maintain, but due to the disadvantage of low thermal efficiency and because of low convective heat transfer coefficient between the absorber plate and the energy extracting carrier fluid, air. Several methods have been proposed for the enhancement of heat transfer coefficient of such collectors. Use of porous packing material in the collector duct is one of the methods. It considerably enhances the energy collection rate by increasing heat transfer rate between a carrier fluid and the absorber of the solar duct. 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 Following correlations have been developed for Colburn factor and friction factor in terms of porosity and operating parameters. Jh= 0.1765[(1/nP)0.6156)(pt/dw)0.1229]0.6651 Rep-0.4767 fp = 2.0291[(1/nP)0.3521)(pt/dw)0.0