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Lecture Comments (1)

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Post by nguyen yen on May 9, 2012

pro. jishi, in example 2 refrigerator, what does the data 'the ice tray compartment is at -23 and the room temperature 27' use for? Or it is supposed to be 'the room temperature is 17'??

Heat Engines and Second Law of Thermodynamics

  • The heat flow statement of the second law of thermodynamics: Heat flows spontaneously from a substance at high temperature to a substance at lower temperature; it does not flow spontaneously in the reverse direction.
  • Essential features of a heat engine:
    1. Heat is supplied to the engine at high T
    2. Part of the input heat is used to do work
    3. The remainder is rejected at a lower T.
  • Efficiency of a heat engine e = 1 – Qc/QH, where QH is the input heat taken in at the higher T, and Qc is the heat rejected at the lower T.
  • Kelvin-Planck statement of the second law: It is impossible to construct a heat engine, operating in a cycle, with efficiency e equal to 1.
  • Heat pump: It takes energy from a cold object, along with energy input by work, and it rejects heat to a hot reservoir.
  • Clausius statement of the second law: It is impossible to construct a machine that transfers energy from a cold object to a hot object without the input of energy by work.

Heat Engines and Second Law of Thermodynamics

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Introduction 0:13
    • Statement of Conservation of Energy
    • Flow of Heat from Hot to Cold
  • Heat Engines: Kelvin-Plank Statement 4:36
    • Steam Engine
    • Efficiency of Engine
    • Kelvin Plank Statement of Second Law
  • Example 17:01
    • Heat Engine with Efficiency 25%
    • Work Done During 1 cycle
    • Power
  • Heat Pump: Clausius Statement 20:47
    • Refrigerator
    • Coefficient of Performance (COP)
    • Clausius Statement
    • Impossible Engine
  • Equivalence of Two Statements 36:51
    • Suppose Kelvin-Plank Statement is False
    • Clausius Statement is False
  • Extra Example 1: Heat Engine Cycle
  • Extra Example 2: Refrigerator