Gravity dependence of pressure drop and heat transfer in straight two-phase heat transport system condenser ducts

Gravity dependence of pressure drop and heat transfer in straight two-phase heat transport system condenser ducts

Delil, A.A.M.

National Aerospace Laboratory NLR

1992-04-21

Condensers are crucial components of two-phase heat transport systems envisaged for future large spacecraft. To properly design such condensers, one uses experimental data, obtained from ground testing and reduced gravity aircraft and rocket flight testing, plus results of thermal modelling and scaling calculations. A frequently reported result of such activities, is that condensation lengths required in low-gravity environment exceed the corresponding lengths on earth (in horizontal ducts) up to one order of magnitude and more, while the accompanying pressure drops are almost the same. Since the flow patterns are different in the two situations, it is better to theoretically (and also experimentally) investigate the impact of gravity on condensation pressure drops and heat transfer for an identical flow pattern, namely annular-wavy-mist, observed along almost the entire condensation length (for vapour qualities ranging from close to 1 down to values below 0.1), both in low-gravity environment and in vertical downflow in a gravity field. Within the validity range of the model used the impact of gravitation on condenser pressure drop and full condensation length is shown to be manifest for two different working fluids (ammonia and Rl 14), and various duct diameters and thermal loading conditions (the power transported, the operating and sink temperatures).

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Nationaal Lucht- en Ruimtevaartlaboratorium

Campus only

NLR Technical Publication TP 92167 L

Aerospace Engineering Reports

report

(c)1992 National Aerospace Laboratory NLR