Example 22.2 Cooking with a Pressure Cooker Known: pressure regulator (petcock) ·Initially1 kg water 30 min Qin 1atm>p=75kPa(gage) 1atm 100 kPa ● unsteady System boundary. H20 m=I kg V=6L Determine: CV p=75 kPa(gage) Vapor e>Higher p, ·T2,m2 T(133C Liquid Assumptions: ·Uniform flow 0m=500W ·△PE,△KE→0 one exit and no inlets ·p(thus T)constant Steam leaves as a saturated vapor ·Wcy→0 上游充通大学 Mar/29,Wed,2017 7 SHANGHAI JLAO TONG UNIVERSITYMar/29, Wed, 2017 7 Example 22.2 Cooking with a Pressure Cooker Higher p, T (133˚C) pressure regulator (petcock) Known: • Initially 1kg water • 30 min Qin 1atmp=75kPa(gage) • 1atm = 100 kPa • unsteady Determine: • T2 , m2 Assumptions: • Uniform flow • ∆PE, ∆KE  0 • p (thus T) constant • Steam leaves as a saturated vapor • WCV0 CV one exit and no inlets