Abstract:
The development of multi-kilowatt space-based systems
requires the transport of waste heat loads over long
distances in micro-gravity conditions.
In this context two-phase heat transport systems are
attractive enabling a high rate of heat transport with
low pump powers compared to single phase systems.
In this context the design of a two-phase heat exchanger
to transfer heat from a single-phase fluid (water) to a
two-phase fluid (Freon 114) is discussed.
Until reliable micro-gravity (< 10-3g) test data on the
heat transfer and pressure drop in a two-phase flows are
available, it is deemed necessary that the design of
heat exchangers' passages should promote
gravity-independent flow regimes. This would make the
design and test data, obtained at ground conditions,
applicable in micro-gravity environments.
The design concept investigated hinges on utilising a
set of helical flow passages (with small cross
sectional area) to ensure a predictable flow regime,
annular flow, up to high vapour qualities (>0.8), in
both micro-gravity and one Ig' environments.
The concept was applied to the design of a 5kW helically
coiled evaporative heat exchanger for space-based
systems, which was subsequently manufactured and tested.
Ground tests gave results close to analytical
predictions based on computer simulations of the heat
transfer and pressure drops in helical flow passages.
Finally design guideline for a two-phase evaporative
heat exchanger for space-based systems is provided,
along with . conclusions and areas to be further
researched.
