Mass and energy rate balances for throttling device SS,(1i,1e,1p),CV: 2 Conservation of mass: 0=1m1-m2 Inlet Exit Partially open valve Conservation of energy: 0=a.-%+(a兰+）-o+兰-0） Common assumptions for throttling devices -SSSF:no changes with time adiabatic:small surface area and high flow rates APE =0:small elevation change - neglect kinetic energy terms 2 2 上游充通大 April 5,2018 11 SHANGHAI JLAO TONG UNIVERSITYApril 5, 2018 11 Mass and energy rate balances for throttling device SS, (1i ,1e ,1D ), CV: Common assumptions for throttling devices – SSSF: no changes with time – adiabatic: small surface area and high flow rates – ∆PE = 0: small elevation change – neglect kinetic energy terms 2 2 1 2 1 2 V V , 2 2   h h ⇒ Conservation of energy: ⇒ Conservation of mass: 1 2