Development of a High Capacity Two-Phase Thermosyphon Gas-Fired Water Heater

摘要

A program was undertaken to design, construct, and test a prototype high capacity two-phase thermosyphon gas-fired water heater, with a firing rate of 200,000 Btu/hr and a 120-gallon storage tank, and to evaluate the cost, performance, and potential market for such heaters. Numerous heat exchanger variations were constructed and tested to identify viable configurations. A 1,000-hour life test was performed on six different heat exchanger configurations in order to examine their resistance to evaporator tube erosion. The finished prototype was found to operate with 79-80% recovery efficiency and 0.84% standby loss. A field test unit operated for six months in San Diego, California, with indications that mineral deposit accumulation on the condenser is not a serious problem. The newly developed two-phase thermosyphon heat exchanger is of higher capacity than previous designs and uses an erosion-resistant copper alloy to avoid evaporator degradation. The system was predicted to have a payback period of from one to three years when compared to existing conventional water heaters.