Development of a Passive Bypass Valve for one and two Phase Fluid Loops for Space Applications

Abstract

To cope increasing cooling demands, single-phase and two-phase fluidic cooling loops are being developed by European Satellite primes. Innovative components are currently being developed such as the Passive Bypass Valve (PBV) which autonomously diverts flow from the radiator when thermal dissipation is low, maintaining the equipment within the operating temperature range. The objective of the ESA project was to develop an Engineering Model (EM) of the PBV for single-phase and two-phase Mechanically Pumped fluid Loops (MPL) and Loop Heat Pipes (LHP) up to TRL5. The development has been conducted by the Netherlands Aerospace Centre, Nammo and OHB. A trade-off study was done for conceptual designs of the bypass valve including: (1) Bi metallic actuated, (2) Differential temperature actuated, (3) Wax actuated (4) Thermostatic sensor actuated. Technical and non-technical requirements as well as system aspects were rated as well as breadboard testing was done for the most promising concepts. The valve type 4 was selected for the design and manufacturing of the Engineering Model (EM) Passive Bypass valve. The EM valve is hydraulically actuated via capillary tube by expansion of a liquid Galden HT80 inside a remotely located sensor. The EM valve showed an adjustable range (±9⁰C) and repeatable switching as function of temperature (±10⁰ C) in three orientations tested in the single phase MPL. A small hysteresis of ±1.5⁰C (up or down in temperature) has been observed which could be related to the thermal inertia of the hydraulic liquid. The two-phase LHP test showed that the valve stabilized the sensor (payload) temperature around 33⁰±5⁰C (upper limit of the valve) at a condenser temperature of -20⁰C under varying load cases ranging from 500W down to 20W.The conclusion was that EM valve has been successfully developed and tested to TRL 4-5. Activities are defined to improve its maturity further to TRL 5-6.