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A two-dimensional model to calculate the radial heat transfer coefficient in a heat pipe evaporator with trapezoidal grooves is extended to highly efficient so-called ‘Re-Entrant’ groove geometries. Results from the model are compared with experimental values. Good agreement is found. For further theoretical studies the heat transfer model is combined with liquid flow characteristics in axial groove direction. Based on these numerical studies, an advanced capillary structure is developed to improve the heat transfer coefficient. The new structure consists of the Re-Entrant grooves with additional micro grooves which are manufactured on top of them. It is modeled in a first attempt by superposition of two two-dimensional heat transfer models. A parameter study shows that for certain dimensions of the micro grooves the overall evaporative heat transfer coefficient considerably increases compared to the standard Re-Entrant groove geometry.

The Combined 2 Phase Loop Experiment (COM2PLEX) is a SPACEHAB rooftop test facility to investigate the 0-g behavior of three different capillary-pumped loops. A flawless operation of these devices under actual space environment is an essential precondition for successful applications of this technology in future space projects. Four European companies have developed COM2PLEX in a co-operative effort under contract to ESA/ESTEC. All capillary pumped loops are of the Loop-Heat-Pipe type. The hardware shall be flown on STS 107, scheduled for launch in March 2001. At the time of writing this paper all loops are in manufacturing or under acceptance testing.

An ESA technology programme led to the successful development of an aluminum extruded heat pipe family based on a multi re-entrant grooves design and using ammonia as working fluid. This family, called High Capacity Grooved Heat Pipe (HGP), has been submitted to a space qualification programme according to ESA standards (ESA PSS-49; see ref.[1]), which aimed to fulfill an as large as possible range of potential applications. Therefore, four heat pipe diameters (11 mm, 15 mm, 20 mm and 25 mm), two heat pipe outer shapes (circular, saddles integrated) and two heat pipe configurations (straight, bent) have been selected for going into this space qualification. The space qualification programme, started in 1994, ended up early 1997. The present paper presents the HGP heat pipe family characteristics and the space qualification programme.

This paper presents the last developments which have been performed at SABCA under internal funding, and the application of this work on the Technological Telecommunication Satellite STENTOR. The High Performance Capillary Pumped Loop ( HPCPL ) has been defined to get a reliable operation mode under a very wide range of operation conditions. Preliminary results have been already presented (ref. (1)), showing the high performances and the reliable functional characteristics of the HPCPL. The present paper emphasises the last developments which have been performed at SABCA.

The paper presents the results of various SABCA activities in the field of two-phase heat transport, being a critical review and analysis of existing capillary pumped loops, the identification of the needs of future capillary pumped two-phase thermal control systems, the development of capillary evaporators, which incorporates nickel porous structures, that can provide a pumping pressure up to 38000 Pa, and the solving of the problem of capillary pump cavitation. These activities have led towards the development of a reliable multi-evaporator/condenser capillary pumped loop, which is discussed in details. A test loop configuration is described. The presented results of various tests clearly prove the viability of the concept for future applications. Proposed flight demonstrations are presented.

The Water Supply Assembly (WSA) is part of the Liquid Management Section (LMS) of the Hermes Environmental Control and Life Support Subsystem (ECLSS) (see ref. [1] and [2]). The WSA has to provide pure water for drinking and food preparation (rehydratation of dry food and beverage powder) and to provide pure water for hygiene purposes (oral hygiene and towel wetting). To obtain different desired temperatures (as well as different quantities of water to be dispensed), a heating device, using electrical foils, and a cooling device, using a water/water heat exchanger have been designed with regard to the critical mass and power requirements. Two dispensers are used to fill food/beverage or hygiene (towels) containers. As part of the Hermes C1 phase, breadboard models of the heating device (heater) and of the cooling device (chiller) have been manufactured and functionally tested.

This paper presents results of new development work carried out in the context of the Water Conditioning Assembly (WCA) which is part of the Liquid Management Section (LMS) of the Hermes Environmental Control and Life Support Subsystem (ECLSS) (see ref [1] and [2]). Its task is to condition and monitor the quality of highly pure water which has been produced in two fuel-cell stacks by the oxidation of hydrogen. This water will be used for different cooling elements (e.g. water evaporator, water sublimator) and as potable water for drinking and food purposes. The assembly consists mainly of: a hydrogen separator, providing for removal of dissolved and gaseous residual hydrogen from the fuel-cell water.

In the frame of an ESA technology program, the development of a High Capacity Grooved Heat Pipe (HGP), based on the thermal requirements of the next generation of telecommunication satellites, was contracted to SABCA. Different promising concepts and methods of groove technology were reviewed. A trade-off and design study was performed on potential HGP concepts, taking into account theoretical performances (on earth and in micro-gravity), ease of manufacturing and of assembly as well as the heat pipe working reliability and priming capability. The two finally selected concepts were aluminium extruded heat pipes (outer diameter of 25 mm, vapour core diameter of 15 mm), based on a multi re-entrant grooves concept or on a mixed rectangular/re-entrant grooves concept.