A Laboratory Setup for Observation of Loop Heat Pipe Characteristics

Heat pipes, loop heat pipes and capillary pumped loops are heat transfer devices driven by capillary forces with high-effectiveness & performance, offering high-reliability & flexibility in varying g-environments. They are suitable for spacecraft thermal control where the mass, volume, and power budgets are very limited. The Canadian Space Agency is developing loop heat pipe hardware aimed at understanding the thermal performance of two-phase heat transfer devices and in developing numerical simulation techniques using thermo-hydraulic mathematical models, to enable development of novel thermal control technologies. This loop heat pipe consists of a cylindrical evaporator, compensation chamber, condenser along with vapor and liquid lines, which can be easily assembled/disassembled for test purposes. This laboratory setup is especially designed to enable the visualization of fluid flow and phase change phenomena. There are transparent windows in the compensation chamber that enable the monitoring of the fluid characteristic. The setup demonstrated typical loop heat pipe performance. Three working fluids (water, acetone and methanol) were used in the characterization of the loop heat pipe. Visual observations have confirmed an opinion, generally held among heat pipe specialists, that loop heat pipes are tolerant to bubble generation in the compensation chamber; this tolerance however strongly depends on the intensity of boiling.