Effect of Gravity on Electrohydrodynamic Conduction Driven Liquid Film Flow Boiling

Abstract

Liquid film flow boiling is used in many terrestrial thermal management applications as a heat transport mechanism. However, it suffers in microgravity applications such as spacecraft thermal management because the gravitational body force is not present to facilitate liquid film flow and bubble removal from the heater surface. One way of overcoming these constraints is to use an electrical field to move a liquid film in the absence as well as in the presence of gravity. In this experimental study, electrohydrodynamic conduction pumping is used to rewet the heater surface during liquid film flow boiling. The experiments are performed both terrestrially and onboard a variable-gravity parabolic flight. Terrestrial steady-state results show a maximum superheat reduction of 6°C and a 62% increase in critical heat flux when the electrohydrodynamic pump is moderately activated. The parabolic flight transient results indicate that, although there was an adverse effect of electrohydrodynamic on heater surface temperature at heat flux less than (due to delayed onset of nucleate boiling), heater surface temperatures were actually lowered at higher heat flux due to activation of the electrohydrodynamic conduction pump. The microgravity results onboard the parabolic flights also pave the way for full-scale orbital testing of electrohydrodynamic-driven liquid film flow boiling onboard the International Space Station.