上浒充通大￥ SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lectures 16 Chapter 5 Mass and Energy Analysis of Control Volume Analysis Spring,2017 Prof.,Dr.Yonghua HUANG 强 AMMAMRA http://cc.sjtu.edu.cn/G2S/site/thermo.html 1日G
Engineering Thermodynamics I Lectures 16 Spring, 2017 Prof., Dr. Yonghua HUANG Chapter 5 Mass and Energy Analysis of Control Volume Analysis http://cc.sjtu.edu.cn/G2S/site/thermo.html
Closed system/Open system Closed system(CM) Open system (CV) T2,V2 D2 T State 1 ---> pT,v inlet exit > A Pr Ty Vi m Besides 0&W,energy accompanying State 2 mass as it enters or exits. Objective of Chap.5:develop illustrate the use of the CV forms of the conservation of mass and conservation of energy 上游究通大学 Mar/15,Wed,2017 2 SHANGHAI JLAO TONG UNIVERSITY
Mar/15, Wed, 2017 2 Closed system/Open system Closed system(CM) Open system (CV) State 1 State 2 p1 , T1 , v1 p2 , T2 , v2 m p1 , T1 , v1 p2 , T2 , v2 inlet exit Objective of Chap. 5: develop & illustrate the use of the CV forms of the conservation of mass and conservation of energy Q W Besides Q & W, energy accompanying mass as it enters or exits. pi , Ti , vi pe , Te , ve
Developing the mass rate balance Dashed line defines the control volume boundary mi nev(①) nev(t+△) Region i LRegion e m →m; Time t Time t+△t me→ Study: the fixed quantity of matter m as time elapses: mev(t)+mi=mev(t At)+me mev(t At)-moy(t)=mi-me me(t+△t)-nev(t) mi me △t △t△t 上游充通大 Mar/15,Wed,2017 3 SHANGHAI JIAO TONG UNIVERSITY
Mar/15, Wed, 2017 3 Developing the mass rate balance Study: the fixed quantity of matter m as time elapses: mi me m
conservation of mass principle min=50 kg Dashed line defines the control volume mi boundary One-inlet,one-exit control volume system mev(t) > me Inlet i mcv(t+△t)-mev(t) mi me Exit e △t △t △t At time t time rate of change of time rate of flow time rate of flow mass contained within of mass in across of mass out across the control volume at time t inlet i at time t exit e at time t Multi-streams dmev At time t: dt mi me → L Mass flow rate (SI units:kg/s) 上游充通大 Mar/15,Wed,2017 4 SHANGHAI JIAO TONG UNIVERSITY
Mar/15, Wed, 2017 4 conservation of mass principle At time t mcv(t) mi me At time t: Mass flow rate (SI units: kg/s) Multi-streams One-inlet, one-exit control volume system
Evaluating the mass flow rate ri velocitys、 time interval dm dA Volume Control volume (CV) of matter Incremental area Control surface(CS) amount of mass A:area crossing dA during =pVn△t)dA the time interval△t Divided by△t ≥(N.a) Muti-streams instantaneous rate Integration over A of mass flow =pVn dA 防= PVn dA across dA 上究大学 Mar/15,Wed,2017 5 SHANGHAI JIAO TONG UNIVERSITY
Mar/15, Wed, 2017 5 Evaluating the mass flow rate m velocity time interval : area Incremental area Divided by ∆t Integration over A Muti-streams