Analytical Investigation of Expansion Waves in Two-phase Flows with Different Sound Speeds

Abstract

Recently, by the appearance of the refrigeration air conditioning system and heat pump system using the two-phase flow ejector, the efficiency of the cycle has been largely improved in comparison with the conventional system. In mixing section of the ejector, the suction flow of the subsonic single-phase gas refrigerant flows through the outside of the driving flow of the supersonic two-phase refrigerant. Within these flow fields, shock and expansion waves that affect the performance of the ejector can occur; therefore, such effects must be taken into account in the design of the ejector system. In this study, the expansion waves generated in flow fields with different speeds of sound are researched analytically by changing the momentum and thermal relaxation times. From analysis results, we successfully made expansion waves which occur in the flow field with two-phase flow and single phase gas flow, even though single-phase gas flows were subsonic. The reason, why expansion waves exist in subsonic state is due to the relaxation phenomena between the phases and the pseudo-like-convergent nozzle effect in the single-phase gas flow. The results of this study provide a clue that can help us better understand fluid flow phenomena in the mixing section of the ejector.