CHE 3010 - Thermodynamics of Chemical Processes Venkat Padmanabhan, PhD Department of Chemical Engineering Tennessee Tech University Lecture 2 - Basic Concepts 8/29/2018 CHE 3010 - Thermodynamics Tennessee Tech University 1
System and Surroundings SURROUNDINGS SYSTEM System: Quantity of matter or a region of space under consideration Surroundings: Anything outside the thermodynamic system is called the surroundings Boundary: The system is separated from the surroundings by the boundary (can be fixed or moving) BOUNDARY 2
Types of Thermodynamic Systems Open systems There may be both mass and energy transfer across the boundary SURROUNDINGS mass transfer across the boundary SYSTEM BOUNDARY energy transfer across the boundary 3
Types of Thermodynamic Systems Closed systems There is NO mass transfer across the boundary. Energy transfer may be there NO mass transfer across the boundary energy transfer across the boundary 4
Types of Thermodynamic Systems Isolated systems There is NO mass or energy transfer across the boundary NO mass transfer across the boundary energy transfer across the boundary INSULATION 5
Thermodynamic Properties A set of quantities that uniquely define the thermodynamic state of the system E.g. temperature, pressure, mass, volume, density, refractive index, surface tension, boiling point, freezing point, specific heat, internal energy, etc. Thermodynamic Properties Extensive Properties (depend on the size) Intensive Properties (do NOT depend on the size) The ratio of two extensive properties is an intensive property 6
Thermodynamic Properties Temperature Measured using thermometer, thermistor, thermocouple, etc. Units Celsius (C), Fahrenheit (F), Kelvin (K), Rankine (R) F = (9/5)C + 32 K = (C + 273.15) R = (9/5)(C + 273.15) Pressure - Barometric (atmospheric), Gauge, and Absolute pressure Units Pascal (Pa), N/m 2, Kg/(m.s 2 ), J/m 3 Absolute pressure = Gauge pressure + Barometric pressure 7
Thermodynamic Properties Specific Property A property that is expressed per unit mass Molar property A property that is expressed per unit mole Both are intensive properties P2.1 What is the specific volume of a 10 Kg cube of side 2 m? Q. Can you express specific volume in terms of any other intensive property? 8
Thermodynamic Equilibrium Equilibrium A state of balance. There are no unbalanced potentials or driving forces A system in equilibrium experiences NO changes when it is isolated from its surroundings A system is in thermodynamic equilibrium ONLY if it is in thermal equilibrium (temperature is same through out), mechanical equilibrium (pressure is same through out), and chemical equilibrium (chemical potential is same through out) A system in equilibrium is one of the thermodynamic states of the system 9
Energy Kinetic Energy (K) (1/2)mv 2 [m is the mass] m v Potential Energy (P) mgh [g is the gravitational acceleration] Other (chemical) potentials: Internal Energy (U) Gibbs Free Energy (G) m h Enthalpy (H) Helmholtz Free Energy (A) 10
The Law of Conservation of Energy Total energy of an isolated system is constant; energy can be transformed from one form to another, but can be neither created nor destroyed m Initially at rest at a height h Energy in the form of potential energy P = mgh VACUUM h Finally traveling down with a velocity v Energy in the form of kinetic energy K = (1/2)mv 2 Potential Energy is not destroyed and Kinetic Energy is not created Potential Energy has been converted to Kinetic Energy 11
The Law of Conservation of Energy P2.2 An object with a mass of 100 kg is dropped from a height of 20 m in vacuum. If the acceleration due to gravity is g = 9.8 m/s 2, what is the final velocity of the object just before hitting the ground? If the same object is dropped from the same height on moon, where g = 1.6 m/s 2, what is the final velocity? 12