DETERMINATION OF FLOW CHARACTERISTICS OF PNEUMATIC VALVES USING ISOTHERMAL CHAMBER

摘要

In this paper, alternative methods for obtaining the sonic conductance and the critical pressure ratio are presented. The methods use the isothermal chamber that can almost realize isothermal condition due to larger heat transfer area and heat transfer coefficient by stuffing metal wire in it. Using this chamber, the sonic conductance and the critical pressure ratio are obtained by measuring only pressure in the chamber. With this method, it takes only some seconds and costs lower energy than the ISO 6358 procedure. Furthermore, the authors have investigated the effect of temperature change in the isothermal chamber. In the proposed charge method, temperature change affects pneumatic characteristics measurement not so much. On the other hand, the proposed discharge method is easy to be influenced by temperature change. However, the discharge method has the merits not to depend on the dynamic characteristics of the regulator and to simplify the measurement system.