Investigation of the dynamics of a Capillary Pumped Loop assisted with a mechanical pump: Influence of pump location

Capillary driven two-phase loops are promising solutions for cooling high power electronic devices. A significant upgrade of the operating conditions can be achieved by a small mechanical pump assistance removing the pumping limit inherent to the evaporator porous wick. However, in this couplings, the key issue is to maintain a steady vaporization regime in the evaporator. In the present study, the dynamics of a Capillary Pumped Loop assisted with a centrifugal pump is investigated with both experiments and modeling efforts. The results have revealed (i) that changing the pump location can deteriorate the system robustness with 5 times larger (2.25 kPa) evaporator pressure deviations and (ii) the appearance of a system bifurcation to undamped oscillations at high heat load. A theoretical analysis was performed in frequency domain. It has shown that the loop dynamics is affected by an unexpected transient positive feedback between the pump and the condenser. It has also shown that the loop robustness could be enhanced within a significant range of heat load by a suitable improvement of the condenser efficiency.