High Heat Flux, Gravity-Independent, Two-Phase Heat Exchangers for Spacecraft Thermal Management

A significant advantage of utilizing forced convection boiling heat transfer for spacecraft thermal management applications is that high heat fluxes are yielded that allow heat exchange equipment to be substantially compacted and reduced in mass. To date, two-phase heat transfer has not been utilized aboard spacecraft due to the uncertainty of the influence of gravity on the fluid dynamics and heat transfer within the heat exchange equipment. A subcooled flow boiling regime has recently been identified in which the bubble dynamics and two-phase flow controlling the heat transfer are independent of the gravitational field. The parametric bounds of this regime have been explored using a numerical simulation of the bubble dynamics in subcooled forced convection boiling. A gravity-independent/dependent regime map has been constructed, which depends on the Jacob number, Reynolds number, Weber number, and a liquid/vapor density ratio. A subcooled forced convection boiling heat exchanger has been fabricated that will operate in the gravity-independent and dependent regimes. It is currently being tested under terrestrial conditions in order to validate the gravity-independent/dependent regime map.