1. Introduction to Eng. Thermodynamics.pptx

Chapter 1

1. Introduction To Thermodynamics 1

2. Thermodynamic System, Surroundings and Boundary Thermodynamic system is a quantity of matter or a space which is chosen for the study. All the medium outside to the system is called surroundings . The medium which separates system from its surroundings is called boundary . System and surroundings taken together is called universe . Objective of most of the thermodynamic analysis is to study the interaction between the system and the surroundings and effects of this interaction on the system or on the surroundings. System and surroundings can interact with each other either by mass transfer or energy transfer . 2

3. Closed System Only Energy can cross the boundary of the system A system with fixed mass, no mass transfer, energy can transfer in and out Eg : a tightly capped cup of coffee, piston Cylinder device with no exits Total mass of a closed system always remains constant therefore any closed system can be completely described by the properties of particular amount of mass inside the system. Hence, a closed system is also called a control mass (CM). 3

4. Open System System in which both mass and energy transfer takes place is called open system Eg : an open cup of coffee, air compressor In case of an open system, properties of particular mass cannot describe the properties of the system for any instant. For the study of an open system, we select some specified region and analyze this region with reference to thermodynamic properties. Hence an open system is also called a control volume (CV). 4

5. Mass Energy Closed System No Yes Open System Yes Yes Isolated System No No Isolated System Neither mass nor energy can cross the boundary of system. Eg : Coffee in closed and well insulated thermos bottle 5