Donatas Mishkinis

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.

Low Power and Low Temperature LHP for Thermal Control of Rovers

The experimental results of a propylene miniLHP with advanced stainless steel wick and novel design pressure regulating valve are presented and discussed in the paper. The LHP thermal control system has been designed for low power (below 30 W) and low temperature (control temperature set point -30 oC) operation. System has demonstrated outstanding performance and excellent capability of temperature control. The new design of pressure regulating valve allows to eliminate such undesirable effects as temperature oscillations and instability of start up and operation at low power regimes, to increase the system reliability and precision temperature control. The analysis of functionality of the pressure regulating valve as a thermal switch and temperature controller is presented.

Start‐Up Performance of A Loop Heat Pipe With Variable Heating Patterns and Periodic Cycles

Despite recent intensive investigations on performances of Loop Heat Pipes (LHP), there are still many unexplained behaviors in the start‐up and transient operation of LHPs. The start‐up of a LHP has been the most critical and important part of an LHP operation specifically for space applications. It is highly desirable to ensure reliable and reproducible start‐ups and minimize temperature overshoots. The Canadian Space Agency has conducted a series of original tests in atmosphere and vacuum, in order to characterize the LHP operation as a thermal regulation device for spacecraft applications. Special attention has been paid to start‐up conditions including environments (vacuum versus atmosphere), thermal pre‐conditions (heating/cooling history), variable heating rates (from variable conductance to constant conductance regime), and variable heating patterns (space‐characterized heating). Different start‐up results have been observed under variety of conditions. Attempts have been made to characterize the ...