EXPERIMENTAL AND ANALYTICAL STUDY OF THE HEAT TRANSFER CHARACTERISTICS OF A SOLAR AIR HEATER INCORPORATING A FINNED ABSORBER
Abstract
The present study is directed toward experimentally and theoretically investigating the thermal performance of a solar collector incorporating a finned absorber. A realistic analysis is made of a general class of flat-plate solar air heaters in order to determine the significant design or operating parameters which effect collector thermal performance. The results of this analysis are used to study the parametric effect of the airflow passage arrangement, number of cover plates, cover-to-absorber plate spacing, absorber-to-back plate spacing, airflow rate, inlet-to-ambient temperature difference, insulation thickness, and wind speed. The results of this analysis indicate that collector efficiency is significantly improved by increasing the effective absorber-to-air heat transfer coefficient three to four times the value pertinent to the simple flat-plate collector at the same operating conditions. The results also indicate that collector performance is insensitive to any additional increase in the heat transfer coefficient. Based on the above finding, a continuous fin configuration has proven to be a potential improvement in collector design. Several experiments were undertaken to study the heat transfer characteristics of this type of collector design to provide more insight into the heat transfer process. An algorithm was developed to reduce the finned test absorber experimental data to yield heat transfer coefficients. Graphical heat transfer correlations are presented which can be used in the thermal analysis of finned collectors. A rigorous numerical analysis was developed in order to give the experimental results a theoretical basis. The analytical procedure is based on the simultaneous solution of the conservation equations to yield velocity, pressure, and temperature distributions from which flow characteristics are determined. Results of the numerical analysis are compared with the present experimental results and with available theoretical predictions. A direct application of these results may be to develop new collector surfaces with improved characteristics.
Degree
Ph.D.
Subject Area
Mechanical engineering|Energy
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