Evaluation of a boiling collector solar heating system: Final report, June 1986--May 1987

An experimental study of a pilot scale, self-pumping solar system utilizing a boiling collector is presented. The advantage of a self-pumping solar system is the elimination of the need for either a mechanical pump or controller. In such a system, the vapor pressure not only drives the vapor from the elevated collector to the condenser but also forces the return of the condensed liquid to the collector. The primary objectives of this study were to confirm the viability of the self-pumping design concept and to identify ways in which the system can be optimized. The pilot system is configured with a single solar collector panel, a separator, two refrigerant accumulators, a small refrigerant reservoir, a tube-in-shell heat exchanger, two water storage tanks and associated piping and valves. The system operates in two alternating cycles. During the run cycle, liquid refrigerant, R-113, is gravity-fed to the roof-mounted collector from an attic accumulator tank and a small auxiliary reservoir. Vapor exiting the collector is condensed and then collected in an accumulator at ground level. Once the liquid refrigerant stored in the upper accumulator is depleted the system switches to the pump cycle in which condensed refrigerant is returned to the elevated solarmore » collector by utilizing the pressure differential created by vapor pressure build-up in the collector. 2 refs., 19 figs., 7 tabs.« less