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HVAC School - For Techs, By Techs

Sep 22, 2016

In this episode of HVAC School, Bryan talks to some apprentices about basic thermodynamics. That is the fancy scientific way of saying that we're moving heat.

The way we think of "hot" and "cold" is relative to our comfort. However, the scientific concepts of "hot" and "cold" are very different from our relative understandings of those qualities. For instance, there is only ONE value of "cold" in the universe: absolute zero (0 kelvins, -460°F). Any temperature above that contains heat.

Heat and temperature are NOT synonymous. Instead, heat refers to molecular motion, and temperature is an average measurement of molecular motion. Therefore, not all heat results in a temperature change. For example, adding heat to an ice cube at 32°F (0°C) changes the ice cube from a solid to liquid water. The heat added is called latent heat. Heat cannot move unless there is a differential in temperature, and it always moves from an object with more heat to one with less heat. Everything in nature tends towards equilibrium, and heat is no exception. In those cases, heat transfer will theoretically occur until both objects are at the same temperature.

There are three main methods of moving heat: conduction, convection, and radiation. Conduction moves heat when a warmer object touches a cooler one. Convection occurs when heat moves through a fluid. Radiation occurs when heat moves on electromagnetic waves, such as when the sun's heat passes through a window.

Join us as we cover:

  • Heat & temperature and the difference
  • Boiling and superheat
  • Fahrenheit, Celsius, and Kelvin scales
  • Absolute zero
  • Molecular motion
  • Hot and cold
  • British Thermal Units (BTUs)
  • Tons of air conditioning (and BTU/ton)
  • Energy conversions
  • Pressure and its effect on temperature
  • Conduction, convection, radiation
  • How heat transfer works in HVAC/R systems


If you want to learn more about heat transfer, check out this article.

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