Oscillatory heat transfer in helically coiled tube with fully developed turbulent oscillation flow

An experiment was conducted to investigate the effects of oscillation on transient and time average heat transfer characteristics for fully developed turbulent flow in an uniformly heated helical coiled tube. The phase lag of transient coefficient of local heat transfer relative to the phase feature of flow rate oscillations was also studied. The experimental range of parameters is as follows: Re=25000-125000, oscillations frequency f=0.05-0.003, which corresponds to the thermal hydrodynamic oscillations encountered in a helical coiled tube boiling channel. A correlation for predicting the time-averaged heat transfer coefficient of single-phase turbulent flow under unsteady or oscillatory condition was proposed. The secondary flow mechanisms and the effects of interaction between the flow rate oscillation and secondary flow were analyzed on the basis of experimental data. Some new phenomena were observed and explained.