Heat transfer characteristics of titanium/water two-phase closed thermosyphon

Abstract

Experimental investigations were carried out to study heat transfer characteristics of titanium (commercially pure titanium, TA2)/water two-phase closed thermosyphon (Ti/H 2O TPCT). Experiments of copper/water (Cu/H 2O) TPCT with same dimension and manufacturing process had also been performed for contrast. Experimental results show that there are no remarkable differences of heat transfer coefficients in evaporator ( h e ) between the two kinds of TPCTs, whereas surprisingly the experimental results of heat transfer coefficient in condenser ( h c ) of Ti/H 2O TPCTs are about 2–3 times more than that of Cu/H 2O TPCTs, moreover the Nusselt’s theoretical correlation based on laminar filmwise condensation is not suitable for simulating the h c of Ti/H 2O TPCTs. Experimental results and theoretical analysis of surface free energy difference between condensate and solid surface indicate that the mixed condensation mode with dropwise and filmwise condensation coexisting on titanium surface result in the higher h c for Ti/H 2O TPCTs. Experiments on condensation mechanism of titanium surface are ongoing to further validate the point.