Direct Expansion Solar Collector and Heat Pump. Final Report

摘要

The system discussed is a hybrid heat pump/solar collector combination in which solar collectors replace the outside air heat exchanger found in conventional air-to-air heat pump systems. The solar panels ordinarily operate at or below ambient temperature, eliminating the need to install the collector panels in a glazed and insulated enclosure. The collectors simply consist of a flat plate with a centrally located tube running longitudinally. Solar energy absorbed by exposed panels directly vaporizes the refrigerant fluid. The resulting vapor is compressed to higher temperature and pressure; then, it is condensed to release the heat absorbed during the vaporization process. In the absence of solar input, the panel temperature will drop, and significant amounts of energy will be extracted from the ambient air by convection, radiation, and condensation of moisture. The direct-expansion collector design is described and compared with other flat-plate collector designs. Its operation is analyzed and models are presented that allow optimization of the design with respect to certain of its parameters. Control and monitoring of the demonstration system are addressed, and the tests conducted with the demonstration system are described. Areas are pointed out where difficulties arose, and additional work is suggested. The entire heat pump system is modelled, including predicted performance and costs, and economic comparisons are made with conventional flat-plate collector systems. Software listings of certain modelling programs are appended. (ERA citation 07:061129)