two-phase flow, injector, low pressure
Vapor-liquid injector is a passive device in which thermal energy of vapor is used to compress and heat a cold liquid. In the past such injectors were used extensively for feeding water into boilers, especially of steam engines. Recently an interest in the two-phase injectors revived with new proposals of their application in thermal engineering, refrigeration and air conditioning. Low-pressure steam-water injectors may be applied as thermal driven liquid pump in absorption and steam ejection refrigeration systems. In this paper a close attention is paid to steam-water injectors in which superheated steam of relatively low pressure is the driving medium. Paper presents selected results of experimental and theoretical studies of a such type of steam-water injector. Experimental research was conducted on a laboratory scale injector made of transparent material. The measured parameters were the pressure and temperature distributions in the injector as well as inlet mass flow rates of both fluids. The measurements were conducted for constant inlet flow conditions during the injector stable operation. Between the measurements, inlet water flow rate and/or outlet back-pressure varied. Experimental flow characteristics of a low-pressure steam-water injector is presented. In theoretical part of the study, recorded distributions of pressure and temperature in the injector mixing chamber were used to evaluate the heat transfer coefficient for the vapour-liquid condensing flow. In the paper, also attention was paid to the evaluation of heat transfer coefficient during condensation in the mixing chamber.