Search Results

The CPL technology has been under development for the last 15 years. Many technical and manufacturing issues have been worked out. However the deprimes of capillary pumps have remained the most difficult problem to solve. The Advanced CPL (A-CPL) design concept was proposed in an effort to make the capillary pumps more tolerant to both vapor and noncondensible gases. A test loop was constructed to demonstrate the operational principles of the A-CPL at room temperature. Freon 134a was chosen as the working fluid so that Teflon tubing could be used as the loop transport lines for flow visualization purposes.

Capillary Pumped Loops (CPL) are projected to be the primary heat transport device for the next generation spacecrafts and satellites. The major shortcoming of a traditional CPL system has been its inability to tolerate vapor and/or non-condensible gas (NCG) bubbles when they are present in the liquid side of the loop. The vapor/NCG bubbles ultimately caused the capillary pumps to fail. A novel CPL design concept, called Advanced CPL or A-CPL, was introduced to create deprime resistant capillary pumps. The main idea of the A-CPL was to generate a liquid flow through the capillary pump core to flush out vapor/NCG bubbles.

Heat transfer characteristics of a Loop Heat Pipe (LHP) are difficult to predict due to the complex nature of thermal interaction between the LHP itself and the environment it operates in. The overall thermal conductance varies not only with the power input, sink temperature and ambient temperature as expected, but also with the system initial condition and/or previous history of its operation. Hence, the analytical modeling of LHPs often yielded inaccurate results when compared with the actual data. The U.S. Naval Research Laboratory (NRL) recently completed the development of a transient LHP model. Accordingly, NRL carried out an extensive LHP test program, in part, to provide test data for the model verification. In this paper, description of the test program and results of the model verification will be presented.