Thermal Resistance-Capacitance Network Model for a PCM Coupled Heat Pipe

A spacecraft's thermal control system is often overdesigned to reach the heat dissipation demands based on peak heat load and not orbit-average heat load. Phase Change Material (PCM) coupled heat pipe is a promising solution to avoid such overdesign, reducing the spacecraft's cost and mass. PCM canister stores heat from the electronic devices during the brief transient peaks and slowly releases it to the heat pipe, which further rejects to the thermal radiator during idle cycle time—designing a PCM canister module coupled to a heat pipe using a resistance network model forms this paper's primary objective.The PCM canister with phase change material is modeled as an interconnected network of resistances and capacitances. i.e., a part of the heat transferred to a node will be stored by the phase change phenomena (acting as capacitance), and the rest is conducted through the PCM (acting as a resistor). Further, the canister's base is thermally coupled to the evaporator end of an axially grooved cylindrical heat pipe, which is also modeled as three resistors and capacitances due to three heat regions pipe (evaporator, adiabatic, and condenser region). The network so obtained is solved iteratively to get the required heat transfer rate at the condenser end of the heat pipe. The model is used to optimize the canister dimensions and PCM fill ratio for various heat loads and cycle times relevant to spacecraft orbital motion. The significant enhancement of the operating time and reduction in the peak temperature is seen due to PCM's coupling with heat pipes. This would be very useful in spacecraft applications to reduce the thermal radiator's size (and hence mass). The concept can also be extended to terrestrial applications like high-performance laptops or servers encountering unsteady heat loads.