Thermodynamics EAS 204 Spring 2004 Class Month Day Chapter Topic Reading Due 1 January 12 M Introduction 2 14 W Chapter 1 Concepts Chapter 1 19 M MLK

Transcription

1 Thermdynamics EAS 204 Spring 2004 Class Mnth Day Chapter Tpic Reading Due 1 January 12 M Intrductin 2 14 W Chapter 1 Cncepts Chapter 1 19 M MLK Hliday n class 3 21 W Chapter 2 Prperties Chapter 2 PS M Chapter 2 Prperties PS W Chapter 2 Prperties 6 February 2 M Chapter 3 Heat&Wrk PS W Chapter 3 Heat&Wrk 8 9 M Chapter 4 First Law Chapter 4 PS W Chapter 4 First Law M Chapter 4 First Law PS W Chapter 4 First Law M Review Chapter 5 PS W Exam March 1 M Chapter 5 Secnd Law Chapter 5 PS W Chapter 5 Secnd Law 16 8 M Chapter 5 Secnd Law W Chapter 6 Entrpy Chapter 6 15 M Spring Recess n class PS 8 17 W Spring Recess n class M Chapter 6 Entrpy PS W Review M Exam 5-6 PS W Chapter 8 Gas Pwer Chapter 8 22 April 5 M Chapter 8 Gas Pwer PS W Chapter 9 Vapr Pwer Chapter M Chapter 9 Vapr Pwer PS W Chapter 9 Vapr Pwer M Refrigeratin s Chapter 10 PS W Refrigeratin s M Review PS 14 TBA FINAL

2 Curse Summary Chapter 1 Cncepts Thermdynamic system, prperties, state pint, prcess, cycle, heat and wrk. Thermdynamic prblem slving technique. Chapter 2 Fluid Prperties Real gases - steam, air, refrigerants tables Ideal gases Equatins f state - EES CD Chapter 3 Heat and Wrk Wrk in nn-flw, steady flw and unsteady flw systems. Adiabatic Prcess Chapter 4 First Law First Law fr prcesses and cycles Heat and wrk in clsed nn-flw, pen flw and unsteady flw systems. Chapter 5 Secnd Law Statement and Crllaries Heat Engines Reversible engines and refrigeratrs Carnt Chapter 6 Entrpy Secnd Law and heat engines The Entrpy prperty Isentrpic prcess Entrpy change calculatin Chapter 8 Gas Pwer s Braytn (gas turbine) cycle Ott (spark ignitin engine) cycle Diesel cycle Chapter 9 Vapr Pwer s Rankine (steam pwer) reheat, superheat and regeneratin cycles Chapter 10 Refrigeratin s Vapr Cmpressin Heat Pumps Reversed Braytn

3 THERMODYNAMICS OVERVIEW Thermdynamics Thermdynamics is the study f the relatinship between all frms f Energy beginning histrically with the relatinship between Heat and Wrk. Laws f Thermdynamics ( fundamental bservatins) Mass Balance (shuld be a law) Mass can nt be created r destryed and is cnserved. First Law Heat and wrk are equivalent Prperty energy is defined Energy can change frm, can nt be destryed, and is cnserved Secnd Law Heat can nt be cnverted cmpletely t wrk. Prperty entrpy defined. Ideal and actual heat engine efficiency.

4 THERMODYNAMICS IN DESIGN Thermdynamic Analysis Prcess Analysis Thermdynamic analysis is the first step in energy system design. Thrugh Thermdynamic Analysis the required mass flws, vlume flws, temperatures and pressures are established. Perfrmance is determined. ENERGY SYSTEMS Gasline Engines Diesel Engines Steam Pwer Plants Chemical Plants Cmpressin Systems Gas Liquefactin Fd Prcessing Plants Rcket Engines Air Cnditining Systems Refrigeratin Systems Heating Systems Gas Turbine Engines

5 Thermdynamics Cncepts Thermdynamic System Prperties State Pint Prcess Heat Wrk Energy

6 HEAT WORK Thermdynamic MASS Cntrl Vlume 3 Types f SYSTEMS Clsed Open Unsteady

7 CLOSED THERMODYNAMIC SYSTEM NON FLOW SYSTEM A MASS OF MATERIAL. Heat and Wrk can crss the system bundaries. Mass can nt. Examples: A clsed tank. A pistn cylinder. A balln Heat Wrk Cncepts System Prperties State Pint Prcess

8 OPEN THERMODYNAMIC SYSTEM STEADY FLOW THERMODYNAMIC SYSTEM A FIXED REGION IN SPACE Mass, heat and wrk can crss the system bundaries. Examples: turbine, cmpressrs, bilers, heat exchangers Cncepts System Prperties State Pint Prcess Mass in Mass ut Heat Wrk

9 UNSTEADY FLOW THERMODYNAMIC SYSTEM A VARIABLE MASS Mass, heat and wrk can crss the system bundaries Cncepts System Prperties State Pint Prcess Examples: A filling tank. An emptying tank Pistn-Cylinder Filling Heat Mass Wrk

10 Identify the thermdynamic system, 1) pen,steady flw thermdynamic system 2) clsed,nn-flw thermdynamic system 3) unsteady flw thermdynamic system in the fllwing prblems. Cncepts System Prperties State Pint Prcess 2-48 clsed system, mass f water in the pistn cylinder clsed system, mass f hydrgen in bth tanks 3-50 pen system, regin in space ccupied by the nzzle 3-74 clsed system, mass f ball 4-11 clsed system, mass f steam in the radiatr 4-84 pen system, regin in space ccupied by the turbine unsteady system, mass initially in the tank 5-84 pen system, regin in space ccupied by the heat engine pen system, regin in space ccupied by the cmpressr pen system, regin in space ccupied by the mixing chamber

11 Thermdynamic Prperties Temperature p v ρ F = 1.8 K= R= Pressure kpa, atmspheres, bar, lb/in Abslute pressure = Gage pressure + Ambient pressure Density kg/m V Vlume m V = mass v u SpecificInternalEnergy kj/kg, BTU/lb du = c c v C F v dt F, C + 32.,ft C, abslute, 3 m /kg,ft,lbm/ft 3 specifc heat at cnstant vlume, kg/jg, m /kg U InternalEnergy kj, BTU SpecificVlume /lb K, R 2 C, BTU/lbm F Cncepts System Prperties State Pint Prcess

12 Thermdynamic Prperties h Specific Enthalpy kj/kg, BTU/lbm h = u + pv c p dh = c dt specific heat at cnstant pressure, H Enthalpy kj, BTU H = m h s S Specific Entrpy kj/ p S = m s Entrpy kj/kg K C, kj/kg C, BTU/lbm F BTU/lbm F Cncepts System Prperties State Pint Prcess

13 PRESSURE P = P + abs atm P gage

14 Frce Units - frce = mass x acceleratin 1N = 1kg 1m/sec N = 1kg m/sec Mass is gravitatinal N at an acceleratin f 2 measured indirectly by measuring frceit exerts. 2 l kg mass weighs m/sec 2 the 1lb 1lb 1lb 1lb 1lb f f m f m = lb = lb m m 1 = slugs = l slug 1 ft/sec c weighs1lb g ft/sec ft/sec f at an acceleratin f ft/sec 2 Energy Units - 1J = 1N 1m Calrie 1g water at 15 1J = calries 1kJ = kg water at 15 frce x distance, mass and temperature change C raised15 C C raised15 C 1ftlb f = 1lb BTU 1lb f m 1ft 1BTU = 778 ftlb water at 60 f F raised1 F Pwer Units - energy per time 1watt 1J/sec 1kw 1kJ/sec 1HP = 550ftlb 1kw =.7457HP f /sec

15 THERMODYNAMIC STATE POINT Prperties are measured. Equatins and mdels are fitted t the data resulting in : Tables f Prperty Values Equatins f State Cmputer prperty mdules Tw prperties define the state pint f a single phase fluid. One prperty defines the state pint f a multiphase fluid. rdinate prperty abscissa prperty (T,p,v,u,h,s) Cncepts System Prperties State Pint Prcess

16 THERMODYNAMIC PROCESS A thermdynamic prcess is an interactin between a thermdynamic system and its surrundings which results in a change in the state pint f the system Reversible Prcess A prcess is reversible if the state pints f all affected thermdynamic systems, including the external system r surrundings, are returned t their riginal state pint values. Examples: - mvement f a frictinless pendulum - transfer f wrk t ptential energy withut lss - mvement f a frictinless spring Cncepts System Prperties State Pint Prcess Irreversible Prcess A prcess which can nt be reversing bringing all the affected thermdynamic prperties back t their riginal values is irreversible. Examples: - applying brakes t a mving wheel - mixing ht and cld water - transfer f heat thrugh a finite temperature difference

17 THERMODYNAMIC CYCLE A thermdynamic system underges a cycle when the system is subjected t a series f prcesses and all f the state pint prperties f the system are returned t their initial values. Cncepts System Prperties State Pint Prcess Q cycle net = cycle Q prcess p W cycle net = cycle W prcess initial pint First Law v δq = δw

18 Thermdynamic Prblem Slving Technique 1. Prblem Statement Carbn dixide is cntained in a cylinder with a pistn. The carbn dixide is cmpressed with heat remval frm T1,p1 t T2,p2. The gas is then heated frm T2, p2 t T3, p3 at cnstant vlume and then expanded withut heat transfer t the riginal state pint. 2. Schematic 3. Select Thermdynamic System pen - clsed - cntrl vlume a clsed thermdynamic system cmpsed t the mass f carbn dixide in the cylinder CO 2 p p 4. Prperty Diagram state pints - prcesses - cycle Q T2,p2 T3,p3 W v Q W T1,p1 5. Prperty Determinatin T2,p2 v T p v u h s Laws f Thermdynamics Q=? W=? E=? material flws=?