Performance study of a steam ejector in vacuum drying application

Abstract

This paper presents performance study of a steam ejector in vacuum drying application. With an experimentalset up, the effects of operating conditions to the ejector’s performance; primary pressure, flow rate of ventilatedair through the vacuum’s chamber, ejector’s back pressure, and the chamber’s temperature, were investigated.Importance parameters used to describe the ejector’s performance are the vacuum chamber’s pressure (Rs), theentrainment ratio (Rm), and the pressure lift ratio (PLR). From the study, it was shown that (1) Increasing theprimary pressure from 1-6 bar (gauge), the vacuum pressure was increased. The maximum obtained vacuumpressure was at -0.79 bar (gauge) at the primary pressure of 5 bar (gauge). (2) Increasing the flow rate of ventilated air from 0-2,500 l/min, the vacuum pressure tended to drop around 6-12%. (3) Increasing the ejector’s back pressure from 0-0.6 bar (gauge), the absolute pressure in vacuum chamber was increased with thedecrease of pressure lift ratio. (4) Increasing the chamber’s temperature from 30 oC to 50 oC and 70 oC, theentrainment ratio was raised. The maximum entrainment ratio of 0.24 was obtained at the chamber’s temperatureof 70 oC and at the primary pressure of 4 bar (gauge).

Keywords : Ejector, Steam, Vacuum drying