Conceptual development and CFD evaluation of a high efficiency - Variable geometry ejector for use in refrigeration applications

Abstract

Ejector based refrigeration cycles are an alternative to the sorption systems commonly associated with solar cooling since the required high-pressure motive fluid can be generated with solar heat. However, ejectors have been unable to achieve commercial maturity due to their low thermal efficiency and their intolerance to deviations from the design point. In the present work, an ejector that implements variable geometry mechanisms is proposed and evaluated using CFD simulations. In order to address the low thermal efficiency issue, changes to the design of current ejectors are also discussed in terms of its irreversibility sources; the large momentum difference between the primary and secondary flows is a well-known irreversibility source. The resulting ejector is able to operate more efficiently than current designs while maintaining a constant efficiency when subjected to variable operating conditions.