Thermodynamics

• Thermodynamics


  The study of energy conversion from one form to another
• Heat


  • Thermal energy transferred between systems due to a temperature difference
  • Transfer of thermal energy between molecules within a system
  • Measures how energy moves or flows
• Temperature


  • An absolute measure of the average total internal energy of an object
  • Describes the average kinetic energy of molecules within a material or system
  • Can be measured in Celsius, Kelvin, Fahrenheit, or Rankine
  • Thermometer measures its own temperature in equilibrium to other system
• Celsius scale


  • Named after Ander Celsius
  • Boiling point and freezing point of water at standard temperature and pressure is 100°C and 0°C
• Fahrenheit scale


  • Named after Gabrielle Daniel Fahrenheit
  • Boiling point and freezing point of water at standard temperature and pressure is 212°F and 32°F
• Kelvin scale


  • Named after Lord Kelvin aka William Thomson
  • Absolute temperature scale
  • Based on the triple point of water, 273.16 K
  • K is equal to degrees Celsius + 273.16
  • Triple point - the point at which all three phases of the substance coexist simultaneously
  • Critical point - point on a three dimensional graph of temperature
• Rankine


  • Named after William Macquorn Rankine
  • R is equal to degrees Fahrenheit + 460
• Calorie


  Amount of heat that would raise the temperature of 1 g of water 1°C higher
• Joules


  • Unit of energy
  • The SI unit for heat
• British thermal unit (BTU)


  • Unit for energy
  • Quantity of heat required to raise the temperature of 1 lb of liquid water by 1°F at a temperature that water has its greatest density
  • 1 calorie is equal to 3.969 * 10^-3 BTU is equal to 4.18 J
• Zeroth Law of Thermodynamics


  Heat will flow from high temperature to the system with low temperature until the bodies reach thermal equilibrium with each other
• Modes of heat transmission

  • Conduction - heat transfer takes from molecule to molecule through a body or through bodies in contact
  • Convection - heat transfer is due to the motion of molecules in the medium
  • Radiation - heat transfer takes place without any intervening medium
• Conductor


  Permits heat transfer between bodies
• Insulator


  Prevents heat transfer between bodies
• Thermal conductivity (k-value)


  Time rate of steady state heat flow through a unit of homogeneous material
• Thermal resistance (r-value)


  Ratio of temperature difference between the two phases of material to the rate of heat flow per unit
• Thermal conductance (c-value)


  • Time rate of steady state heat flow through a unit area of a material
  • The reciprocal of the r-value
• Temperature gradient


  • Ratio of temperature difference and thickness of the medium
  • Gradient is an increase or decrease in the magnitude of a property
• Latent heat (QL)


  Amount of heat necessary to change the phase of a system without changing its temperature
• Latent heat of fusion


  Heat necessary to change a unit mass of substance from solid to liquid state or from liquid to solid state at its melting point
• Latent heat of vaporization


  Heat required to change unit mass of substance from liquid to vapor state or from vapor to liquid state at its boiling point
• Sensible heat


  Amount of heat necessary to change the temperature of the system without changing its phase
• Specific heat


  Amount of heat required to change
• Total heat


  The sum of the latent heat and the sensible heat