1、核能電廠核能電廠 CFD安全分析研究室安全分析研究室Institute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis LabChapter 5 Flow Analysis Using Control Volume Institute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室2MAIN TOPICS5.1 Conservation of Mas
2、s5.2 Newtons Second Law Linear Momentum Equations 5.3 First Law of Thermodynamics Energy Equation5.4 Second Law of Thermodynamics Irreversible FlowInstitute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室35.1 Conservation of MassContinuity Equatio
3、n_1v Basic Law for Conservation of Massv For the system and a fixed, nondeforming control volume that are coincident at an instant of time, the Reynolds Transport Theorem leads toB=M and b =1Time rate of change of the mass of the coincident systemTime rate of change of the mass of the content of the
4、 coincident control volumeNet rate of flow of mass through the control surface= +Institute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室Intensive and Extensive nIntensive Property: Fluid property does not depend on the amount of material present
5、 in the system, e.g., V, a, P, T, etc.nExtensive Property: Fluid property depends on the amount of material present in the system, e.g., mass, momentum, energy, etc.Institute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室5Conservation of MassCont
6、inuity Equation_2System and control volume at three different instances of time. (a) System and control volume at time t t. (b) System and control volume at time t, coincident condition. (c) System and control volume at time t + t.Institute of Nuclear Engineering and ScienceNPP CFD Modeling and Safe
7、ty Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室6Conservation of MassContinuity Equation_3vFor a fixed, nondeforming control volume, the control volume formulation of the conservation of mass: The continuity equationRate of increaseOf mass in CVNet influx of massInstitute of Nuclear Engineering and Science
8、NPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室7Conservation of MassContinuity Equation_4vIncompressible FluidsvFor Steady flowThe mass flow rate into a control volume must be equal to the mass flow rate out of the control volume.Institute of Nuclear Engineering and ScienceNPP CFD
9、 Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室8Other Definitionv Mass flowrate through a section of control surfacev The average velocityInstitute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室9Fixed, Nondeforming Control Volume_1v W
10、hen the flow is steadyv When the flow is steady and incompressible v When the flow is not steady“+” : the mass of the contents of the control volume is increasing“-” : the mass of the contents of the control volume is decreasing.Institute of Nuclear Engineering and ScienceNPP CFD Modeling and Safety Analysis Lab核能電廠核能電廠 CFD安全分析研究室安全分析研究室10Fixed, Nondeforming Control Volume_2v When the flow is uniformly distributed over the opening in the control surface (one dimensional flow)v When the flow is nonuniformly distributed over the opening in the control surface
