I know we said that we would keep this information pretty basic, so don't get scared off just yet. The latter two (2) shown above used extensively throughout your HVAC equipment. Heat always wants to find and equal, either through warming other objects, and thereby cooling itself, or taking heat from another object in order to equalize itself with the surroundings. We are going to take each of these examples above and break them down to their basics. We will be using food to explain these examples because, well, I like to eat and now a fair amount about food :^).
The first example is Radiation. Radiating transfers heat the source to the first solid object the heat waves encounter without heating the air around it. This differs from transferring heat to objects through direct contact, like conducting or through air, like convecting. When you use a microwave oven to cook your food, this is an example of radiating. The "Micro Waves" go through the air without heating air and solely heat the object in the oven. Radiant floor board heaters are a good example of Radiant heat. As the coils in the heater gain temperature, and typically begin to glow, they heat the first object in which the heat waves contact.
The next example is Conduction. Conduction uses direct contact to transfer heat between sources. Think of Conduction as taking your hot food out of the microwave and holding the plate in your hand. You can feel the your hand holding the plate getting warmer and the food is now becoming cooler. Your plate is now starting to condition the food, much the same way and air conditioner conditions the air. The heat exchangers use this method to transfer heat. On some pieces of equipment, there are two water tanks, one is for cooling, one is for heating. These tanks are filled with water and metal plates. As the unit calls for warmth, the metal plate absorbs the heat from the water, and transfers it into the furnace.
The final example is Convection. The easiest way to describe convection is now that your hot plate of food is sitting on the counter since the plate became to hot for you to hold because of the previous method. You now begin to blow on or fan your food to cool it down. Your are passing cooler air over a hot object which is convecting into the air above it and therefore you are now conditioning your food. Your air conditioner uses convection throughout the system in the form of air, water, and refrigerant inside the ductwork and the equipments piping. As you feel the air come out of your ductwork, this is the most apparent example of convection in your HVAC system.
Next time you cook some food, take a moment and look at all the conditioning of the food you just did. Once you break it down into individual steps, it really is amazing and hopefully you have found this explanation to be informative and easy to understand. Next we will look at the specific components and selection. Thanks for reading, and we'll see ya on the roof!
