1993-07-01

Water Conditioning Assembly for Hermes ECLSS 932072

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 (H2) 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 H2 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.

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