Design optimization of a two-phase solar water heater using R-123

Design of a vapor transport solar water heater using R-123, an environmentally safe alternative to R-11, is optimized to maximize thermal performance and minimize life cycle cost. Optimal systems for one- and two-story homes are identified in a parametric study of collector area, condenser heat transfer area, water storage tank volume and circulating refrigerant volume for the Solar Rating and Certification Corporation rating procedure. Selection of collector and heat exchanger areas is critical to performance. With warm and cloudless ambient conditions, the most economic system is a large collector area, low efficiency system capable of meeting nearly 100% of the load. Under more realistic operating conditions, the best design will place more emphasis on efficiency. The condenser should have sufficient surface area to avoid significant increases in collector operating temperatures. Thermal performance is relatively insensitive to either refrigerant or water storage volume.