Heat Transfer Fundamentals

Modes of Heat Transfer

• Conduction: transfer of heat between objects in physical contact
  • Occurs due to vibration of particles
  • More efficient in solids than liquids or gases
• Convection: transfer of heat through movement of fluids
  • Occurs due to difference in density between hot and cold fluids
  • Can be natural (e.g. hot air rising) or forced (e.g. using fans)
• Radiation: transfer of heat through electromagnetic waves
  • Occurs in all directions, not requiring a medium
  • Can travel through vacuum

Heat Transfer Mechanisms

• Heat Capacity: amount of heat energy required to change the temperature of an object
  • Measured in joules per kilogram per degree Celsius (J/kg°C)
• Specific Heat Capacity: heat capacity of a substance per unit mass
  • Measured in joules per kilogram per degree Celsius (J/kg°C)
• Latent Heat: energy required to change the state of a substance (e.g. melting or boiling)
  • Measured in joules per kilogram (J/kg)

Heat Transfer Equations

• Fourier's Law of Heat Conduction: rate of heat transfer through conduction
  • Q = -k * A * (dT/dx)
  • Q: heat transfer rate, k: thermal conductivity, A: cross-sectional area, dT/dx: temperature gradient
• Newton's Law of Cooling: rate of heat transfer through convection and radiation
  • Q = h * A * (T_s - T_e)
  • Q: heat transfer rate, h: heat transfer coefficient, A: surface area, T_s: surface temperature, T_e: environment temperature

Applications of Heat Transfer

• Heat Exchangers: devices that facilitate heat transfer between fluids
  • Examples: radiators, heat sinks, and boilers
• Thermal Insulation: materials that reduce heat transfer
  • Examples: fiberglass, foam, and reflective insulation
• Refrigeration and Air Conditioning: systems that use heat transfer to cool or heat spaces
  • Examples: refrigerators, air conditioners, and heat pumps

Understand the basics of heat transfer, including modes of heat transfer (conduction, convection, radiation), heat transfer mechanisms (heat capacity, specific heat capacity, latent heat), equations (Fourier's Law, Newton's Law of Cooling), and applications (heat exchangers, thermal insulation, refrigeration).