Thermal control of a mechanically pumped two-phase loop

Abstract

With integration and miniaturization of electronic devices, the heat dissipation has grown exponentially, necessitating feasible thermal management systems and cooling alternatives. Among them, two-phase loop cooling is deemed to be highly effective, in which the minichannel evaporator is rendered as a mechanically pumped two-phase loop (MPTL), ensuring the precise thermal control. Herein, the temperature control accuracy of MPTL has been particularly emphasized by proposing the feed-forward offset-free model predictive controller (MPC), and compared with the PI controller that has also been structurally modified (namely, improved PI controller). MPC is designed, optimized and tuned based on the unsteady-state nonlinear analysis, addressing the challenges, such as frequent heat load fluctuations and various nonlinearities/uncertainties mainly encountered during the minichannel boiling. Results depict the superiority of MPC in terms of shorter transient time (measured by set-point tracking), higher temperature control accuracy and lower absolute error (IAE) index (both determined by disturbance rejection), mitigating the effect of flow-boiling uncertainties. Especially, the average transient time of MPC on MPTL has been found at least four times shorter than that of the improved PI controller. Also, IAE index of MPC on MPTL is better than that of the improved PI controller. Meanwhile, the temperature control accuracy of MPC on MPTL during disturbance suppression is as little as 0.2 °C, while that of the improved PI is higher (1.1 °C). The temperature control of the proposed controller (MPC) is therefore satisfactory based on which it can be engaged in MPTL technology for further development of electronic applications.