A falling film evaporator, where refrigerant evaporators on the outer surface of the tube and cooling water flows on the inner side, was tested for practical use in a chiller unit. Falling film heat transfer coefficients for fluorocarbon R22 on an enhanced vertical surface are obtained in a dual-tube evaporator. The heat transfer coefficients of falling film evaporation show a higher performance than those of the conventional R22 evaporator. The vertical-type falling film evaporator, with a U-bent-tube as a liquid-gas refrigerant separator, worked sufficiently in an R22 prototype chiller unit. It was confirmed that the performance of this type of falling film evaporator was greatly improved by use of the enhanced surface structure tube and by the U-bent-tube in the refrigeration cycle.

KEYWORDS: calculating, evaporators, R22, refrigerants, chillers, heat flow, heat transfer coefficient, fluorocarbons, performance, refrigeration.