Variable Conductance Heat Pipes

Variable Conductance Heat Pipe with non-condensable gas resevoir

Variable Conductance Heat Pipe with non-condensable gas resevoir

ACT fabricates VCHPs to exact aerospace requirements. These devices are manufactured under ACT’s AS 9100:2009 and ISO 9001:2008 certified Quality System. The materials used for manufacturing are certified and qualified to meet the demanding level of aerospace quality. Each extrusion is fully characterized to determine thermal and pressure containment capabilities as functions of operating temperature and fluid charge. The welding processes are performed by welders certified to AWS 17.1 Specification for Fusion Welding for Aerospace Applications.

ACT has proprietary heat pipe models to simulate each design application. These models are used to assist with the selection of the right extrusion for each application. The capillary limit, and the associated thermal transport capability of the heat pipe, is determined by taking into account the exact extruded groove geometry.

Temperature control expertise that’s second to none.

The optimum fluid charge is determined for the specific application and the effect of excess fluid charge is determined for both 0-G and 1-G operations. ACT has specialized VCHP prediction models that are used to select the reservoir size and evaluate various control techniques such as: Cold Reservoir (passive, no temperature control), Reservoir Temperature Controlled (thermostatically held at specific set point), Optimum Reservoir Temperature Controlled (active temperature control of reservoir – variable set point) and Non-Wicked Hot Reservoir (reservoir temperature coupled to vapor temperature).

The graph below shows the thermal performance of a reservoir temperature controlled VCHP that ACT built and tested for a spacecraft application. The evaporator section of the VCHP was controlled to +/-1.65°C as the input power was varied from 72 Watts to 150 Watts and as the sink temperature ranged from +15°C to -65°C. The control band achieved was in good agreement with the analytical prediction of +/-2°C.

Performance Test Data for a Variable Conductance Heat Pipe

Performance Test Data for a Variable Conductance Heat Pipe