2013-3-6 Mass Rate Balance In practice there may be several locations on the boundary through which mass enters or exits. and its are accounted for by introducing summations: d=∑m-∑m44w dt The above equation represents the mass rate balance for control volumes with several inlets and exits. Total mass contained in CV at time t is so we can(v d d pdW=∑m-∑m 47 Mass Rate Balance-Integral Form The mass flow rate written in integral from is amount of mass Volyme crossing dA during p(v Ar)dA pV dA the time interval△t fluid The general comass can be written as ,pw=(pva）-(pv,dA d Or more general d p(.元)dA = d 元=unit vector More about this in Fluid Dynamics! 48 g2013-3-6 4 Mass Rate Balance = ∑ −∑ e e i mi m dt dm & & cv (Eq. 4b) The above equation represents the mass rate balance for control volumes with several inlets and exits. ►In practice there may be several locations on the boundary through which mass enters or exits. Multiple inlets and exits are accounted for by introducing summations: 4-7 ►Total mass contained in CV at time t is so we can write Mass Rate Balance- Integral Form 4-8 ►The general conservation of mass can be written as Or more general ►The mass flow rate written in integral from is Æ Distance travelled by fluid Volume = unit vector More about this in Fluid Dynamics! Divide by Δt and integrate over area