THERMAL PERFORMANCE COMPARISONS FOR SOLAR HOT WATER-SYSTEMS SUBJECTED TO VARIOUS COLLECTOR AND HEAT-EXCHANGER FLOW-RATES

This article presents data from side-by-side experiments that shows improvements in overall SDHW system performance as a result of lowering the collector fluid flow rate for direct systems utilizing conventional return tubes. Although they are limited to one location, specific system configurations, and time periods, these experimental results support the general conclusions reached in earlier experimental and simulation studies regarding the advantage of reduced collector flow rate. Side-by-Side experiments were also performed for SDHW systems in which the tanks were fitted with return tubes designed to reduce internal tank fluid mixing. The results of these experiments show only a small difference in overall performance for the systems operated at conventional and reduced collector flow rates. Side-by-Side tests of an indirect SDHW system that employs an external heat exchanger did not show improved performance at reduced tankside flow rates.