INVESTIGATION OF EVAPORATION AND CONDENSATION PROCESS OF INDUCED FLOW USING STEAM EJECTOR

Abstract

The research aims to understand the design parameters of steam ejector nozzle on the performance of flash evaporation induced by the effect of a steam jet passing through it. The research concentrates on studying the effect of ejector nozzle outlet diameter on induced flow from preheated water in a specified evaporator using a subsonic ejector. The thermal energy extracted from the condensed steam mixture in the condenser is used to heat the water in the evaporator. The experimental tests investigate the effect of nozzle geometry on the induced evaporation process by changing nozzle outlet diameter while keeping the pressure of evaporator, condenser and primary steam constant. The experimental results proved that both primary and secondary steam mass flow rates increase versus nozzle outlet diameter, while the entrainment ratio of secondary to primary steam flow rates decreases due to the restricted increase of the secondary steam mass flow rate. The mathematical model prepared to simulate the behaviour of the subsonic ejector is validated using the comparison between experimental and theoretical results. The mathematical model showed that maximum entrainment of 0.57 is obtained at a primary steam pressure of 2 bars when the nozzle outlet diameter is fixed at 1.5 mm, while minimum entrainment ratio of 0.17 is estimated at 1.5 bar pressure related to primary steam when the nozzle outlet diameter is fixed at 2.5mm. The authors recommend defining nozzle geometrical parameters according to the operating conditions of the experimental test rig to enhance ejector efficiency.