Investigation of Gravity Effects on Electrically Driven Liquid Film Flow Boiling: A Micro-Gravity Flight Campaign in Preparation of ISS Experiment

As modern electronics develop, electronic devices become smaller, more powerful, and they are expected to operate in increasingly complex configurations. Consequently, advanced thermal management technologies are required to meet the growing demand, especially in the environment of space where two-phase heat transport systems are limited by the absence of gravity. Electrohydrodynamic (EHD) and dielectrophoretic (DEP) forces can be used to sustain stable liquid film flow boiling in the absence of gravity, which is otherwise impractical, due to the lack of a required buoyancy force to initiate bubble departure. EHD and DEP are phenomena that are represented by the interaction between electric fields and fluid flow. The DEP force especially is characterized by the unique ability to act on liquid/vapor interfaces due to a high gradient of electrical permittivity, allowing for two phase operation. This study investigates the effect of EHD conduction pumping coupled with DEP vapor extraction on liquid film flow boiling during a microgravity parabolic flight, and it characterizes the future two-phase microgravity heat transport technology prior to testing on the International Space Station (ISS). The flight results are compared to terrestrial results on the ground prior to the flight.

A circular EHD conduction pump acts as a fluid film flow mechanism that drives fluid to the center of the experimental chamber, where a square heater resides, simulating a heated electronic surface. The EHD conduction pump disc is held at a constant temperature by a recirculating chiller to ensure condensation occurs on the pumping surface. A DEP electrode sits just above the heater at the interface between the liquid and vapor at a height of 2 millimeters. This electrode provides the necessary extraction force on the vapor generated by the heater, allowing for boiling to occur, even in the absence of gravity. The working fluid is Novec 7100, an engineering fluid with favorable dielectric properties. This study has generated results in terrestrial, microgravity (0-G), and 1.8G environments, allowing for comparison between various working situations. The results of this study show that by utilizing EHD and DEP forces, the experiment can raise critical heat flux, lower the operational surface temperature of the heater, and it can successfully sustain boiling in microgravity. This unique technology has significant advantages, including low power consumption, no vibration or moving parts, light weight, and simple design. This study paves the way for future implementation of EHD-driven two-phase heat transport devices into space and aeronautical electronics applications.