Extremum seeking micro-thermal-fluid control for active two-phase microelectronics cooling

To address increasing power densities in high power electronic devices, microchannel systems operating in the two-phase regime have been explored in recent years for high heat flux cooling applications. However, flow and thermal oscillations, frequently present in two-phase microchannel cooling, may severely compromise the cooling performance and system integrity. This paper considers the thermal-fluid control of a microchannel evaporator by regulating the inlet flow rate using a pump. The control objective is two-fold: stabilize the fluid flow and maintain a low evaporator wall temperature. The first objective is easily achieved with a proportional feedback of flow acceleration. The second objective is more challenging as the achievable wall temperature depends on the heat transfer coefficient which in turn depends on the flow rate and heat load and is typically not well characterized. In this paper, we present an adaptive extremum seeking control law which first uses the wall temperature measurement to estimate the heat transfer coefficient, and then adjusts the flow rate to maximize this estimate. Simulation results demonstrate the efficacy of the proposed scheme.