Abstract:

The different mode of compound heat transfer enhancement leads to different transfer effect. Experimental studies of comparison between different compound transfer enhancement effects on transverse corrugated(TC) tube with full-length twisted tapes of different twist ratios have been conducted with oil of high viscosity. The variation of Nusselt number and resistance coefficient with Reynolds numbers are presented, and then correlation for Nusselt number and resistance coefficient are obtained by a multivariable linear regression analysis in the range of 500<Re<7 000, 50<Pr<180. Comprehensive heat transfer performance is evaluated by the value of performance evaluation criteria. As compared with smooth tubes with full-length twisted tapes, the resistance coefficient of TC tubes with full-length twisted tape inserts can be increased by 2-5 times, theNu can be increased by 1-4 times. With the increasing ofRe, the twist ratios are less able to influence theNu. Values of PEC of TC tubes with full-length twisted tape inserts in proportion ofRe and in inverse proportion of twist ratios on the condition of laminar flow. Under the condition of transition flow, the values in inverse proportion ofRe. In addition, TC tube with twisted tape ofY=5.21 inserts has better comprehensive heat transfer performance than the others.

Key words: compound transfer enhancement, PEC, resistance coefficient, twisted tapes, transverse corrugated tube