Conservation of Mass - The Continuity Equation

Conservation of Mass - The Continuity Equation Law of conservation of mass The law states that mass can neither be created nor be destroyed. Conservation of mass is inherent to a control mass system (closed system). The mathematical expression for the above law is stated as: ∆m/∆t = 0,    where m = mass of the system For a control volume (Fig.9.5), the principle of conservation of mass is stated as Rate at which mass enters = Rate at which mass leaves the region + Rate of accumulation of mass in the region OR Rate of accumulation of mass in the control volume                                                         + Net rate of mass efflux from the control volume = 0      (9.1) Continuity equation The above statement  expressed analytically in terms of velocity and density field of a flow is known as the equation of continuity. Fig 9.5    A Control Volume in a Flow Field