boiling is initiated within the wick. Previously, boiling in the wick was thought to be an ultimate heat transport limit. This ability to operate at higher input heat fluxes subsequently results in significantly lower mass systems as the input heat exchanger, a significant mass component, can be made more compact. Other areas of ongoing development include the investigation of alternate heat pipe envelope materials, specifically composites. If effective ways to utilize these materials can be identified, and several tests are currently underway to do just that, an order of magnitude reduction in radiator system mass can be achieved. (Paper number IAF- ICOSP89-5-5.) 5-9. An Advanced Condenser Design for Space Power Systems J. A. Bamberger & E. P. Coomes Energy Sciences Department, Pacific Northwest Laboratory, Richland, WA 99352, USA. Rankine cycle power systems serve as the backbone for terrestrial electric power generation. For in-space electric power generation, the absence of gravity raises severe questions about the viability of the Rankine cycle because two phase fluids (i.e. boiling and condensation heat transfer) are an integral part of this thermodynamic cycle and provide the most efficient means of thermal energy transport. As on-board electrical power demands increase, the high efficiency Rankine cycle with its boiler, turbine, and condenser can provide a most attractive power conversion choice for almost any thermal source being considered for use in space. An advanced condenser design would greatly enhance the applicability of Rankine cycle systems. Terrestrial condensers operate in the film condensation mode where the liquid film constitutes the dominant heat transfer resistance and the liquid is removed via gravity. In a microgravity environment the proposed mechanisms for condensate removal include suction, surface rotation, vapour shear stresses, capillary action, and mechanical wipers. Although each of these methods offers some potential, each imposes certain limitations or restrictions on the system. An advanced condenser design which uses capillary action to reduce the condensate film thickness and to improve condensation rates by a factor of two has been recently demonstrated. This advanced condenser design offers several advantages for microgravity applications: condensation enhancement with very little additional weight, no additional moving parts, and no need for high vapour velocity. This condenser design would enhance any two-phase thermal transport system being considered for space applications. This paper explores the design options for space power systems which this type of enhanced condensation and phase separation system could provide. (Paper number IAF-ICOSP89-5-9.) 6. POWER CONVERSION, CONTROL & CONDITIONING 6-1. European Regenerative Fuel Cell Technologies for Space Use Francis Baron', Ralf Philipp2 & Werner Tillmetz2 'ESTEC, Postbus 299, 2200 Noordwijk, Netherlands; 2Dornier-System GmbH, Postfach 1360, 7990 Friedrichshafen, W. Germany. Electrolyzers and fuel cells with very high efficiency and very mature development status are necessary for energy storage and supply in space. Within a study performed by Dornier System and funded by ESTEC (title: fuel Cell Component Development), European regenerative fuel cell systems (RFCS) are investigated.
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