Chapter 1 Introduction: Basic Concepts of Thermodynamics

ENGR 224 – Thermodynamics

Test #1 – Outline Spring 2011

Chapter 1 – Introduction: Basic Concepts of Thermodynamics  1st & 2nd Laws of Thermodynamics  Internal, kinetic and potential energies  Dimensions and Units: SI & AE

 gc F = m a  Nomenclature o Systems: Open vs. Closed o Properties . Intensive vs. Extensive . Molar and Specific Properties o State of a system o Processes and Process Paths . Isobaric, Isothermal & Isochoric . Thermodynamic Cycles o Equilibrium: Thermal, Chemical, Phase and Mechanical o Quasi-Equilibrium Process  Pressure: Absolute, Gauge and Vacuum o Barometer, Manometer and Differential Manometer Equations  Temperature Scales: oC, K, oR, oF o Converting between T scales o Changes in temperature

Chapter 2 – Properties of Pure Substances  Pure Substances  Phases and Phase Changes o Vaporization/Condensation, Melting/Freezing, Sublimation/Desublimation  Phase Diagrams: PV, TV & PT o Subcooled Liquid, Saturated Liquid, Saturated Mixture, Saturated Vapor, Superheated Vapor o Tsat and Psat = P* o Saturated Liquid Curve, Saturated Vapor Curve, Two-Phase Envelope, Critical Point o Isotherms and Isobars o Triple Point  Thermodynamic Data Tables o Saturation Temperature Tables and Saturation Pressure Tables o Superheated Vapor Tables and Subcooled Liquid Tables o Linear Interpolation o Double Interpolation  Vapor-Liquid Equilibrium o Partial Pressure, Vapor Pressure, Total Pressure, and Mole Fraction o Relative and Absolute Humidity o Boiling vs. Evaporation  Equations of State (EOS’s) o The Ideal Gas EOS: Always test its validity o Compressibility Factor EOS o Advanced EOS’s: Virial, Van der Waals, RK, and SRK Chapter 3 – Heat Effects

 U(T,P) and H(T,P): Real Substances, Incompressible Liquids and Ideal Gases

 Using the NIST Webbook

 Heat Capacities: Constant Volume and Constant Pressure o Integrate CV to determine U. Integrate CP to determine H. o IG CP polynomial = Shomate Equation (NIST Webbook) o IG: CP = CV + R o Solids & Incompressible Liquids: CP = CV and U = H.

 Hypothetical Process Paths (HPP’s) o Break a complicated process into steps in which just one property changes o Change in any property for the entire HPP is the sum of the changes in that property for the steps that make up the HPP. o Latent Heats: Vaporization, Fusion and Sublimation

. Clapeyron equation – Hvap = fxn(dP*/dT) . Clausius-Clapeyron Equation

 Assumes IG and Vsat vap >> Vsat liq

 Hvap from slope of LnP* vs. 1/T(K) . Antoine Equation – P* = fxn(T)

Chapter 4 – The First Law of Thermodynamics – Closed Systems  Work

o Path variable, inexact differential

o Integral of F dx

o Boundary Work: Wb =  P dV

o Sign Convention: W > 0 for work done BY the system ON the surroundings

o Quasi-Equilibrium Process: Slow, No Unbalanced Forces

.  P dV is easy to evaluate because the restraining force is just Pbulk x Across of the piston.

o Special Processes: Isothermal, Isochoric and Isobaric

. Easier to evaluate Wb.

o Shaft Work – very important for open systems, see chapter 5.

o Other kinds of work . Gravitational and Acceleration Work  It is more convenient to express these in terms of change in kinetic and potential energies . Spring Work  We will usually consider this just another form of boundary work.  Heat

o Energy that moves across the boundary of the system because of a difference in temperature.

o Moves spontaneously from hot to cold things.

o Sign Convention: Q > 0 when heat is transferred from the surroundings into the system.

o Adiabatic Processes: Qnet = 0

o Path variable, inexact differential

o Mechanisms for Heat Transfer . Conduction: Fourier’s Law . Convection: Newton’s Law of Cooling . Radiation: Stephan-Boltzmann Law  The 1st law of Thermodynamics

o Energy cannot be created or destroyed, it can only change form

o Integral Form: Q – W = Esys = { U + Ekin + Epot }sys

o Differential or Rate Form is more useful for open systems (see chapter 5)  Problem Solving Procedure

o Read Carefully, Draw a Diagram, List Given Info & List Assumptions

o Write Equations and Lookup Data then Solve Equations

o Verify Assumptions & Answer Questions !!  Special Cases of the 1st law

o Isobaric Processes: Q = H

o Isochoric Processes: Q = U  Thermodynamic Cycles st o 1 Law: Qcycle = Wcycle

o Types of Cycles . Heat Engines: Purpose is to convert heat into work

 Thermal efficiency: th = fxn(QC, QH) . Refrigeration Cycles: Use work input to remove heat from a cold object (and incidentally reject heat to a hot object)

 Coefficient of Performance: COPR = fxn(QC, QH) . Heat Pump: Use work input to add heat to a hot object (and incidentally absorb heat from a cold object)

 Coefficient of Performance: COPHP = fxn(QC, QH)

Chapter 5 – 1st law Open Systems  Mass & Energy Balances on Steady-State Processes o Flow work o Turbines, nozzles, diffusers, compressors, throttling devices, pumps, heat exchangers, mixers, splitters o SISO & MIMO  Transient Mass & Energy Balances o Uniform flow & uniform state assumptions o SISO and MIMO