Development of a Capillary Structure for the Hermes Water Evaporator Assembly

The development of a capillary structure for the Hermes Water Evaporator Assembly (WEA) is described. The WEA is one of the heat sinks of the (Active Thermal Control Systems) water cooling loop. The capillary structure is needed to retain and distribute evaporating water on the internal surface of an aluminium cylinder facing the cold two phase side of the heat exchanger.

It consists of grooves which are very similar to the axial grooves of aluminium/ammonia heat pipes.

The evaporative heat exchanger is described, the requirements to the capillary structure are reported, analysis and design of the capillaries are outlined and finally the description of the set-up and the results of a subscale test are presented.