"On-demand" electrohydrodynamic (EHD) heat transfer enhancement using an anionic surfactant

Transient heat transfer enhancement performance with electrohydrodynamic (E HD) augmentation was characterized using a single-phase transformer oil in a concentric wire-cylinder test section. Performance using the oil alone wa s inconsistent, but the addition of an anionic surfactant gave reproducible enhancements with rapid response times. The impact of surfactant concentra tion on enhancement behavior was investigated in both the transient and ste ady state regimes. For both high and low concentrations of surfactant addit ive, current response to step voltage changes occurred within 300 msec, and enhancement response lagged due to the thermal mass of the test article. I n the steady state, the high concentration of the additive resulted in a mu ch higher electrical power requirement but gave better enhancement and pres sure drop behavior for a given enhancement than the low concentration. Mech anisms for the positive effect of the surfactant additive are analyzed and electrochemical rate constants are obtained. Implications for the design of controllable EHD-enhanced heat transfer systems are articulated.