Oscillation characteristics of cooling system with macro- and microchannel evaporators

Abstract

This study investigated the dynamics of a pumped liquid cycle system, highlighting the impact of integrating a microchannel evaporator alongside macro-channel components. Without a microchannel evaporator in the system, the pressure drop in the macro-channel evaporator exhibit some variation but remain relatively stable. However, the integration of microchannels induces periodic oscillations in mass flow rate and pressure drops even without active heating. Detailed investigations under various operating conditions reveal the oscillation characteristics. Decreasing pump speed results in reduced amplitude of mass flow rate oscillations, while their frequency increases, indicating more rapid variations. For instance, when $Q_{\text{macro}}$ = 150 W, $Q_{\text{micro}}$ = 0 W, as the speed decreases from 450 rpm to 250 rpm, the oscillation amplitude of wall temperature decreases from 1.51 °C to 1.39 °C and the frequency increases from 0.33 Hz to 0.44 Hz. The frequency of macro-channel pressure drop oscillations increases at lower pump speeds. Similar trends are observed in microchannel pressure drop oscillations, with amplitude tending to decrease as pump speed decreases and higher pump speeds resulting in larger amplitudes. This study highlights the system's sensitivity to the existence of the microchannel evaporator. These findings provide valuable insights for the optimization and control of pumped liquid cycle, contributing to enhanced performance and efficiency.