Inner/outer-loop control methodolgy for mulitple evaporator dryout avoidance under transient heat loads

Abstract

The increasing power density of high-performance electronics has created a need for advanced thermal management strategies. Vapor compression cycles (VCC) offer large heat transfer coefficients via low coolant temperatures and boiling heat transfer, and thus are attractive for electronics cooling. However, the high heat flux imposed by electronics requires new modeling and control techniques for VCC implementation. Challenges include transient heat loads, critical heat flux (CHF), refrigerant charge management, and multi-evaporator management. This dissertation presents research to improve the fundamental understanding of systems-level design, modeling and control of multiple evaporator VCC for high heat flux removal. An experimental testbed is presented, with the option of switching between a heated accumulator and a recuperator to maintain cycle active charge. Static component, heat transfer, and dryout models are identified, and low-order lumped dynamic system models are developed and validated for both accumulator and recuperator operation. The static and dynamic models are used to develop robust, decoupled dryout avoidance controls to provide stability, reject large thermal disturbances and improve cycle energy efficiency. Finally, experimental and simulation results are presented for control validation.