Local Heat Transfer in Forced Convective Boiling of Ammonia and Ammonia/Water Mixture on the Vertical Flat Plate

摘要

The ocean thermal energy conversion (OTEC) and hot spring thermal conversion (STEC) are expected to be the next generation energy production systems. Both systems use a plate heat exchangers, and ammonia or ammonia/water mixture as a working fluid. Measurements of boiling heat transfer coefficients for pure ammonia and ammonia/water mixture were performed on a vertical flat plate heat exchanger, to clarify and characterize the behavior of ammonia and ammonia/water mixture on the plate evaporator. The result shows that in case of pure ammonia, the local heat transfer coefficients increase with an increase in vapor quality for almost all cases. On the other hand, in case of ammonia/water mixture, the local heat transfer coefficients decrease with an increase in vapor quality. In addition, the visualization was performed. As a result of visualization, different boiling flow pattern inside of the plate were observed at different experimental conditions as well as tube flow.