Experimental investigation of the Trombe wall. Final report, October 1977-March 1979

A variable geometry test facility was constructed and an experimental program conducted to investigate the performance characteristics of the Trombe wall, passive solar heating system. The principal objective met in the research project was the determination of representative values of wall gap thermocirculation parameters for various wall geometries. Velocity and temperature profiles in the wall gap were obtained for 2, 4, and 6-inch gap widths. Maximum values for the Grashof number under measured flow conditions ranged approximately from 6 x 10/sup 5/ for the 2-inch gap to 1.5 x 10/sup 7/ for the 6-inch gap, indicating laminar flow and possibly the initiation of transitional flow regimes at the higher Grashof numbers. Turbulent flow behavior was not exhibited within the relatively broad range of test conditions studied in this research, conditions typical of one-story Trombe walls employing practical geometries. A second objective accomplished in this research was the characterization of the Trombe wall thermal efficiency for a variety of operating conditions and wall geometries. Using data collected under essentially clear-sky conditions, collector efficiency curves similar to those commonly used to describe the performance of flat-plate solar collectors were developed for the Trombe wall. The efficiency plots were determined for 2, 4, and 6-inch gap widths using linear regression fits. These regression fits were sufficiently good to validate the applicability of this approach in describing Trombe wall performance.