Fundamentals of Engineering
Thermodynamics Chapter 5
Name the two statements of the Second Law - answerClausius and Kelvin-Planck
Clausius statement - answerIt is impossible for any system to operate in such a way
that the sole result would be an energy transfer by heat from a cooler to a hotter body.
(Heat cannot naturally flow from a colder body to a hotter body.)
thermal reservoir - answera special kind of system that always remains at constant
temperature even though energy is added or removed by heat transfer
Kelvin-Planck statement - answerIt is impossible for any system to operate in a
thermodynamic cycle and deliver a net amount of energy by work to its surroundings
while receiving energy by heat transfer from a single thermal reservoir. (Single thermal
reservoir systems are impossible.)
Primary benefits of Second Law - answer1. helps to predict direction of process
2. helps establish conditions of equilibrium
3. determine the best theoretical performance
4. determines factors for best theoretical performance
Secondary benefits of Second Law - answer1. Lays temperature scale (Kelvin)
independent of the properties of any thermodynamic substance
2. Helps evaluate and find properties (h/u) in terms of properties readily obtained by
experiment.
analytical form of the Kelvin-Planck statement - answerW_cycle <= 0 for a single
thermal reservoir
Entropy Statement of the Second Law - answerIt is impossible for any system to
operate in a way that entropy is destroyed.
Entropy - answerextensive property that is not conserved (can be created but never
destroyed)
Reversible process (theoretical) - answerif both the system and surroundings can be
returned to their initial states after the process has occurred.
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