HEAT TRANSFER ENHANCEMENT MECHANISM OF SPIRAL FLOW LED BY THE SELF-CLEANING TWISTED TAPE FOR VERTICAL CONDENSERS IN NH{sub}3 REFRIGERATING UNITS

摘要

The twisted tape in vertical condensers of refrigerating units can not only self-clean the fouling continuously, but also enhance heat transfer. By the observation experiments of the flow process with and without the self-rotating tape, the comparison experiment of the different twisted tapes between with and without holes along the centerline, and the comparison experiment of different rotating speed of the same tape, it is deduced that the controlling mechanism of heat transfer enhancement is the fluid spiral flow led by the twisted tapes in tubes. Just from the angle of heat transfer enhancement, it is concluded that the short twisted pitch is the optimal structure and the slower rotating speed of the tape is more effective than the higher speed according to the mechanism. The heat transfer coefficient is increased by more than 20% over that without the tape.