Experimental Research On Heat Transfer And Flow Resistance Characteristics Of Upward-Flow Heat Transfer Tube With Self-Rotating Aluminum Twisted-Tapes

The paper introduced the significance, research progress and current situation of heat transfer enhancement and anti-scaling technology, and then explained the test equipment and the equipment of the upward-flow heat transfer tube inserted with self-rotating aluminum twisted tapes.The experiments consisted of two parts: the cold state experiment and the heat state experiment.The cold state experiment took the twenty twisted-tapes and one straight tape as samples, the water as working fluid flowing upwards in the heat trsnsfer tube inserted with twisted-tapes. The changes of pressure drop as well as the friction coefficient were compared respectively, the correlations of flow resistance and friction coefficients were established using nonlinear fitting, the relationships between the structural parameters of the twisted-tape and flow resistance were revealed, and rotating characteristics of the twisted-tapes combined with theoretical formula were also analyzed. It is worth mentioning that theoretical formula of and the friction coefficient were deduced firstly, and the agreement with the experimental results was verified.The heat state experiment took the nine twisted-tapes and one straight tape as samples, the mechanism of the heat transfer enhancement was shown, the heat transfer characteristics of the tube inserted with twisted tapes heated by saturated steam was studied, and the basic principles of Wilson graphic solution were introduced. The changes of the total heat transfer coefficient and heat-transfer coefficient were compared, and the heat transfer enhancement of the twisted-tape inserted in up-flow tube was verified through performance evaluation.The results indicated that pressure drop and the friction coefficient increased when inserting the twisted-tape and the straight tape, the maxium pressure drop was two times of the plain tube; friction theoretical formula of the pressure drop and flow resistance coefficient coincided with the test results; total transfer coefficient for the tube with twisted-tape increased eight to twenty-five percent, the heat transfer enhancement in the up-flow tube was poorer than that in the down-flow tube, but also had practical value.