Overview
Thermodynamics is the study of energy and its transformations. The 1st law of thermodynamics says that energy cannot be created or destroyed. In other words, energy is conserved. The 2nd law of thermodynamics says that even though energy is conse
I. Concepts and Definitions
F. Properties of a system (we use them to calculate changes in energy) 1. A property is a characteristic of a system that can be given a numerical value without considering the history of the system. Examples include T, P, , ve
Models of Working Substances
Gases Phase-change fluids (water & refrigerants) Tables A-2 to 8 & A-11 to 13 Mixtures (advanced)
Solid/ liquid Table A-3 Cp = Cv = C
Perfect gas Pv = RT Cp = constant Cv = Cp R Table A-2a for Cp. u = CvT, h = CpT. P and T are
II. Energy and the First Law of Thermodynamics
A. Energy Transfer by Work. Energy is Conserved. 1. Energy can cross the boundary of a closed system by only two mechanisms: heat transfer and work transfer. 2. The change in energy of a closed system is equa
II. Energy and the First Law of Thermodynamics
A. Energy Transfer as Heat Transfer. Energy is Conserved. 1. Energy can cross the boundary of a closed system by only two mechanisms: heat transfer and work transfer. 2. The change in energy of a closed syste
II. Energy and the First Law of Thermodynamics
A. Generic Statement of the First Law for a Closed System
Time rate of change rate energy rate energy of energy within = system enters system leaves system
No mass enters or leaves. Heat Rate form of energy
General Approach to Problem Solving
Sketch the process. Define your system. Label all known and unknown quantities. Choose a model for the working substance. Write down the mass balance equation. Write down the energy balance equation. Use specialized or
IV. First Law of Thermodynamics
A. Introduction to Open Systems 1. Analysis of flow processes begins with the selection of an open system. 2. An open system is a region of space called a control volume (CV).
Mass entering (inlet) Q
Control volume CV W
Mas
IV. First Law of Thermodynamics
D. Applications to steady flow devices 1. Heat exchangers - example: Clinker cooler for cement kiln Secondary air 520 C, 157,000 lbm/h
Clinker ? C, 151 ton/h
Cooler
Clinker 1400 C, 151 ton/h
Secondary air 20 C, 157,000 lbm/
V. The Second Law of Thermodynamics
A. Introduction 1. The first law: energy is conserved 2. The second law: certain processes do occur and certain processes dont a. example of a mechanical process (assume adiabatic, pistoncylinder device) If the pins are
V. The Second Law of Thermodynamics
E. The Carnot Cycle 1. The reversible heat engine (a piston cylinder device) that operates on a cycle between heat reservoirs at TH and TL, as shown below on a P-v diagram, is the Carnot cycle. 2. Because the cycle is r
VI. Entropy
A. Introduction 1. The first law: energy cannot be created or destroyed 2. The second law: certain processes do occur and certain processes dont 3. The magic vortex tube. Will it work or wont it? Compressed air 2 kg at 4 atm, 300 K Cold air 1
VI. Entropy
G. Entropy Change of a Pure Substance 1. T-s diagram for a pure substance Sat. vap. line Sat. liq. line P = constant
T
sg sf s
sfg = sg sf
Lesson 18, Geof Silcox, Chemical Engineering, University of Utah
VI. Entropy
2. Tabular entropy data a.
General Approach to Problem Solving
Sketch the process. Define your system. Label all known and unknown quantities. Choose a model for the working substance. Write down the mass balance equation. Write down the energy balance equation. Write down the ent
VI. Entropy
H. The Tds Relations and Changes in Entropy 4. Example Two pieces of copper, A and B, with masses 1 and 3 kg, and initial temperatures 0 and 200 C are brought together and allowed to equilibrate while insulated from the surroundings. Determine
VI. Entropy
L. Adiabatic or Isentropic Efficiencies of Steady Flow Devices 1. Turbines (T = 80-90%)
T =
w Actual turbine work =a Isentropic turbine work w s
(7-60)
Isentropic work, ws, is calculated assuming same inlet condition and same outlet pressure a
VII. Power and Refrigeration Cycles
C. The Carnot Power Cycle for an Ideal Gas 1. Description 1-2 reversible, isothermal expansion 2-3 reversible, adiabatic expansion 3-4 reversible, isothermal compression 4-1 reversible, adiabatic compression P 1 Q41=0 4
Thermodynamics I CHEMICAL ENGINEERING 2300-001 MECHANICAL ENGINEERING 2300-001 Solution to First Examination, Monday, 2009 September 28 Prof. Geoff Silcox Chemical Engineering University of Utah Open books, homework, and notes. 1) Read each problem carefu
Thermodynamics I CHEMICAL ENGINEERING 2300-001 MECHANICAL ENGINEERING 2300-001 Solution to Second Examination, Monday, 2009 November 16 Prof. Geoff Silcox Chemical Engineering University of Utah
Problem 1.0
A geothermal power plant is being operated betwe
Review of Engineering Thermodynamics
Universal Balance Equation for Any Extensive Property Accumulation = transport + generation Integrated form for some period of time:
final initial amount amount amount amount amount amount entering leaving generated c