Colorado State University program for developing, testing, evaluating and optimizing solar heating systems. Project status report for the months of December 1995 and January 1996

The Colorado State University Solar Energy Applications Laboratory is currently testing several solar domestic hot water heating systems. The experimental systems are fully instrumented to yield data appropriate for in-depth analyses of performance. One of these systems is an unpressurized drainback system with a load-side heat exchanger. An analysis of the performance of this heat exchanger is the focus of this paper. Analytical calculations for the effectiveness and convective heat transfer coefficients from correlations are compared against the experimental data. Three models for the convective heat transfer coefficients are analyzed and yield results that underpredict the measured heat transfer from 23% to 72%. TRNSYS simulations were performed using the average effectiveness (the calculated effectiveness varies from 0.68 to 0.95); the results compare favorably with experimental results, indicating that a constant effectiveness is an adequate model for the system