Guy Bekaert

Secondary wick operation principle and performance mapping in LHP and FLHP evaporators

High performance Loop Heat Pipe (LHP) technology has advanced to the point that they are the baseline for thermal management for a lot of spacecraft applications. Temperature control and heat dissipation are performed in an efficient, and reliable way thanks to the LHP capillary pumping system. This article summarizes the objectives and performances of a secondary wick incorporated between evaporator and loop reservoir to get the optimum performances. Evaporator co-located with a reservoir is the baseline of LHP concept. This presentation will detail the reason why the thermal disconnection between the reservoir and the evaporator and their hydraulic coupling via a secondary wick is until today the best way to reach the optimum performances of LHP. Sometimes the secondary wick is combined with a bayonet. The article will compare the design without and with this bayonet in terms of impacts on secondary wick operation and performance limitations. The physical laws driving the secondary wick design are summarized. Their performance mapping and their impacts on the evaporator operation are shown. Finally the FLHP (Free LHP) concept is explained. This concept is intended to satisfy the needs of a freely located multi-evaporators loop. The article explains how secondary wicks are used when using evaporators not capillary linked to loop reservoir.

Water Conditioning Assembly for Hermes ECLSS

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. The passive method of gettering the hydrogen (H 2) in a palladium (Pd) matrix at ambient temperature has been used. - a monitoring and measurement device, measuring the contaminants concentration of the water by means of an electrical conductivity meter joined with a temperature sensor, placed downstream of the H2-separator. - a water disinfection device using iodine. - a gas trap, based on diffusion through a filter, avoiding the blockage of the H2 separator, and placed upstream of that device. This paper presents the selected design concepts of the main constituents. Based on these concepts breadboard models of the H 2 separator and of the water quality monitoring device are described. The results of several test series, namely for: - functional efficiency - hydraulics - matrix expansion - contamination by KOH - influence of temperature - relation between conductivity and pH value are presented. The conclusions and the analysis for further development work are then explained.

A new facility for fluid sciences: The liquid structure facility

Abstract The Liquid Structure Facility (LSF) is presently under development under ESA contract. It will be able to perform a wide range of fluid science experiments taking use of the determination of the velocity, temperature, concentration fields and the interface shape deformation. This facility will be activated by telecommands and/or manually by the crew. The key points of the LSF are the different diagnostic configuration capabilities, the modularity of the facility, and the accuracy of the control at the boundary conditions (and thus of the stimuli). The LSF is structured around four different modules: • —the cell module which is exchangeable and is dedicated to an experiment or to a group of experiments, it allows to achieve a high accuracy level for the boundary conditions • —the temperature control module using a liquid cooling loop which can impose a good thermal stability to the cell module • —the diagnostic module • —the electronic and data handling module. The capabilities of the facility are described in terms of stimuli and diagnostic performances.

A new concept for a fluid science facility: The liquid structure facility

Abstract The Liquid Structure Facility (L.S.F.) is presently developed under ESA contract. This instrument will allow to perform a wide range of fluid science experiments taking use of the determination of the velocities, temperatures concentrations and also the interface shape deformations. This facility will be activated automatically or by telescience, or manually by the crew. The main drivers for the design of the L.S.F. were the different diagnostic configurations, the accurate control of the boundary conditions and the modularity of the facility. 1. The L.S.F. is composed by four different modules: 2. -the cell module which is exchangeable and dedicated to an experiment or to a group of experiments in order to achieve the accuracy level requested for the boundary conditions, 3. -the thermal stability of the cell module is obtained by a liquid cooling loop, 4. -the diagnostic module 5. -the electronic module.