컨덕턴스의 개념을 사용한 공압관 시스템의 유량 예측

Conductance is a concept contrary to flow resistance and is extensively being used as a flow index on how easily fluid is transported through a pneumatic pipe or a fluid device. It can be very useful in specifying the characteristic values of flow rate regardless of the kind of the pneumatic devices and pipes used. ISO6358 states that the flow rate characteristics of pneumatic devices should be based on the sonic conductance and the critical pressure ratio in which flow is choked at a minimum cross sectional area of the devices. Such a regulation of flow rate characteristics is quite different from the flow rate equations concerned with incompressible flows. However, researches on the flow conductance are very rare to date and systematic investigation is needed for standardization of pneumatic devices. In the present study, a computational fluid dynamics method has been applied to solve the compressible Navier-Stokes equations with two-equation turbulence models. The present CFD results were validated with existing experimental data. Values of the conductances and friction factors at the inlet and outlet of a pneumatic pipe were used to assess the flow rates. The present results show that the conductance depends on the pressure ratio at the inlet and outlet of the pipe.