Chapter 1: Thermodynamic Concepts and Terminology

1. Chapter 1: Thermodynamic Concepts and Terminology

2. 1.1 Systems: Definitions • System: Part of the universe to analyze. • Surroundings/Environment: Part of universe affected by system. • System Boundary: Separates system from surroundings. Surroundings System System Boundary Universe Chapter 1: Thermodynamic Concepts and Terminology

3. 1.1 Systems: 3 Types Chapter 1: Thermodynamic Concepts and Terminology

4. 1.1 Combustion in Open & Closed Systems PowerPoint frozen? Click here and try again Chapter 1: Thermodynamic Concepts and Terminology

5. 1.2 Properties: Definitions • Thermodynamic Properties: Describe mass and energy of system (e.g., T, P and V). • Extensive Properties: Vary with system size (e.g., V). • Intensive Properties: Independent of system size (e.g., T and P). • Specific Properties: • Divide extensive property by mass • Intensive Property • E.g., Specific Volume, v = V/m = 1/r [m3/kg] Chapter 1: Thermodynamic Concepts and Terminology

6. 1.2 Properties: Total & Specific Volumes • Total Volume: V • [m3] • Upper case V • Specific Volume: v • [m3/kg] • Lower case v Chapter 1: Thermodynamic Concepts and Terminology

7. 1.3 State • Thermodynamic State: • Collection of all Thermodynamic properties of system. • Ability to define system’s state essential in Thermodynamics • Using state principle (Chp 3), can use limited set of property data to determine all property data. Chapter 1: Thermodynamic Concepts and Terminology

8. 1.4 Changing the State of a System • Process: Change in state of system. • 4 Common Processes: • Isothermal: Constant Temperature • Isobaric: Constant Pressure • Isometric: Constant Volume • Adiabatic: No Heat Transfer P = constant (isobaric) T = constant (isothermal) P T v =constant (isometric) v =constant (isometric) v v Chapter 1: Thermodynamic Concepts and Terminology

9. 1.4 Isobaric & Isometric Processes PowerPoint frozen? Click here and try again Chapter 1: Thermodynamic Concepts and Terminology

10. 1.5 Unit Systems • Base Units: Defined by reproducible physical measurements • Derived Units: Derived from base units • SI: Metric International System • Base Units: time (s), length (m), mass (kg) • Force (N) is a derived unit from mass • USCS: U.S. Conventional System or English System • Base Units: time (s), length (ft), force (lbf) • Mass (lbm) is a derived unit from force Chapter 1: Thermodynamic Concepts and Terminology

11. 1.5 Unit Systems: gC • gC: Conversion constant • SI • USCS • 1 lbm 1 lbf Chapter 1: Thermodynamic Concepts and Terminology

12. 1.6 Property Units 1.6.1 Volume, Specific Volume and Density • Volume, V [ m3 or ft3] • Specific Volume, v [m3/kg or ft3/lbm] • Density, ρ [kg/m3 or lbm/ft3] Chapter 1: Thermodynamic Concepts and Terminology

13. 1.6.2 Pressure (P) • Pressure(P): P = Force/Area • 3 Types of Pressure • PGAGE: Measured relative to atmospheric pressure (PATM) • PABSOLUTE: Measured relative to zero pressure (perfect vacuum) • PABSOLUTE : = PATM + PGAGE • Units • SI: kPa = kN/m2 • USCS: psi = Pounds per square inch [lbf/in2] • psig = Pounds per square inch gage [lbf/in2] • psia = Pounds per square inch absolute [lbf/in2] Chapter 1: Thermodynamic Concepts and Terminology

14. H PLINE 1.6.2 Pressure (P) • Manometer: Chapter 1: Thermodynamic Concepts and Terminology

15. 1.6.3 Temperature • Absolute Zero Temperature: • Lowest Possible Temperature • Like m = 0 is smallest possible mass • Temperature Scales: • Absolute: Measured relative to absolute zero • Relative: Measured relative to non-absolute zero temperature • SI Scales and Units: • Relative: 0C, Degrees Celsius • Absolute: K, Kelvin • T(K) = T(0C) + 273.15 • USCS Scales and Units: • Relative: 0F, Degrees Fahrenheit • Absolute: ºR, Degrees Rankine • T(ºR) = T(0F) + 459.67 Chapter 1: Thermodynamic Concepts and Terminology

16. 1.6.3 Temperature Chapter 1: Thermodynamic Concepts and Terminology

17. 1.7 Converting Units • Thermodynamic analyses require unit conversions • Blindly applying “right” units to numeric answer typically leads to wrong answer (i.e., points off on tests and exams) • Keeping track of units can help identify errors • Example: Convert 500 m to miles Chapter 1: Thermodynamic Concepts and Terminology

18. 1.8 Problem Solving in Thermodynamics • Problem Statement • Solution • Diagram of System and Process • Given and Find • Assumptions • Governing Relations • Property Data • Quantitative Solution • Discussion of Results: • Does the answer make sense? • What are implications? • Average engineers have difficulty here • Great engineers excel here Chapter 1: Thermodynamic Concepts and Terminology

19. Homework problem 1.4 PROBLEM STATEMENT: A spacecraft of dry weight 50,000 lbf leaves Earth with 180,000 lbf of fuel on board flies to a planet where the acceleration due to gravity is 12 ft/s2. During the flight to the planet, 2/3 of the fuel is consumed. How much thrust does the rocket need to insure lift-off from the planet? Chapter 1: Thermodynamic Concepts and Terminology

20. Homework problem 1.6 PROBLEM STATEMENT: A gas is contained in a vertical cylinder 3 inches in diameter under a piston whose mass is 50 lbm. The local gravitational acceleration is 32.4 ft/s2 and the atmospheric pressure acting on the outside of the piston is 14.7 psia. What is the absolute pressure of the gas in the cylinder in psia? Chapter 1: Thermodynamic Concepts and Terminology

21. Homework problem 1.10 PROBLEM STATEMENT: A colleague reports that she has developed a new material which will withstand an absolute temperature three times as great as her previous best material which could endure a temperature of 2000oR. What is this new upper limit in K and oC? Chapter 1: Thermodynamic Concepts and Terminology