The Analysis and Prediction of Pressure Drop Oscillation in Phase-change Cooling Systems  

Technologies utilizing flow boiling in microchannel evaporators promise high heat fluxes and system efficiencies. However, boiling in microchannels also face significant challenges due to the occurrence of critical heat flux and flow instabilities, such as pressure drop oscillations. Since several system parameters can cause these issues in a two-phase system, identifying these parameters in advance can help avoid these challenges. This study investigates pressure drop oscillation in a pumped liquid cycle using both experiments and numerical modeling. The model utilizes the moving boundary modeling approach to predict system stability and capture the oscillation characteristics. Both experiments and the model determine how different combinations of system parameters, like the valve settings, pump speed, and evaporator heat load can affect system stability. The study also relates the change in flow oscillation characteristics to the system’s supply and demand pressures. This study examines why certain combination of system parameters induce flow instability and provides ways to mitigate this challenge. A general agreement between the model and experiments also demonstrates the accuracy of the moving boundary modeling approach. Consequently, this modeling approach can be useful in predicting instability, optimizing the system performance, and developing active control strategies for cooling technologies relying on flow boiling in microchannels.