ME235Lecture%201-2-3

# ME235Lecture%201-2-3 - Thermodynamics (VM235) Lecture 1...

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1 Thermodynamics (VM235) Lecture 1 Instructor : Arvind Atreya – E205 JI building aatreya@umich.edu Teaching Assistant David: LiDan198401@gmail.com Key concepts for today: Introduction and applicability of Thermodynamics Some definitions – vocabulary of Thermodynamics Phases and properties of a pure substance. Properties required to define a state. What is Thermodynamics? You have already experienced it. Difficulty lies in generalizing our experience; filtering it down to a few laws; learning how to apply these laws to systems we engineers design and use. Here is what I want you to do: If a person masters the fundamentals of his subject and has learned to think and work independently, he will surely find his way and besides will better be able to adapt himself to progress and changes than the person whose training progress and changes than the person whose training principally consists in the acquiring of detailed knowledge. – Albert Einstein So, please read ahead and come prepared with good questions for the class.

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2 How do we apply thermodynamics to substances? Clearly, we have to first define the substance. 1. We do that by drawing a boundary around what we wish to study. EXAMPLE: 2. We then need to say what is happening at the boundary? Can work, heat, mass cross the boundary? This makes for many definitions: Definition Work Heat Mass Isolated System No No No Closed System Also called Control Yes No Mass Open System Also called Control Volume
3 Imaginary boundary

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4 3. Next we need to define what is in the system? Microscopic definition? or Macroscopic (average) behavior? Continuum hypothesis This opens up a can of worms: Is the material in the system liquid, gas or solid ? – phase? What are the essential properties that uniquely characterize the system? – pressure, temperature, mass, density? What is a property? – Intensive? Extensive? Criteria to differentiate between intensive and extensive properties By specifying the P, T, ρ and V we hopefully would have specified the state of the system, but if the state is changing how should we specify it? 4. This leads to the concept of equilibrium. Is the system in equilibrium with its surroundings? What do we mean by equilibrium? Mechanical , thermal and chemical equilibrium (a) Quasi-equilibrium (b) Non-equilibrium In quasi-equilibrium, the system goes through states that can be defined at every point. Under non-equilibrium, such a definition is not possible. We shall show later that this is the most optimum and most impractical.
5 We have now hinted upon the system undergoing a process quasi-equilibrium or non-equilibrium. Clearly, a process occurs when the system changes its state from state1 to state2.

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## This note was uploaded on 09/15/2010 for the course ME 235 taught by Professor Borgnakke during the Fall '07 term at University of Michigan.

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ME235Lecture%201-2-3 - Thermodynamics (VM235) Lecture 1...

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