Steady State Performance Results for a Flexible High-Performance Variable Conductance Heat Pipe

Performance tests and analysis of a new flexible Variable Conductance Heat Pipe (VCHP) design are reported. The unit features a single liquid passage through most of the length and incorporates flexible sections to reduce transverse bending stiffness to less than 175 N/m. A feedthru plate is accommodated to enable installation of the heat pipe in a dual environment. The unit accepts a high heat flux heat input of more than 50 W/cm² and has a demonstrated thermal conductance of ∼50 W/°C (at 14 W per cm of evaporator length). The demonstrated room temperature heat transport limit is approximately 150 W-m for this 1 cm OD design as configured. The unit was first tested as a Constant Conductance Heat Pipe (CCHP) to validate ammonia charge quantity and heat transport. It was then reworked to include a gas reservoir, and the performance was again validated. The test data was then compared with the thermohydraulic model predictions and shown to be in excellent agreement. Measurements for both transport and charge quantity agreed with the model to within ∼4%. The unit was also tested at various degrees of tilt as a CCHP and performance compared to the model. Transport and optimum charge quantity were also verified for the VCHP configuration.