Posted in: Open Mind.	Tagged: Barbecuing, BBQ, Engineering, Father's Day, Food, Fun, Heat Transfer, Mechanical Engineering, Open Mind, Science, Thermodynamics.
Summer is here and with it brings barbecuing season. While the average charcoal BBQ may seem like a pretty simple appliance there is some solid engineering behind its design.
First let’s look at the charcoal briquettes. An engineer took chunks of wood and organic matter and heated it up in the absence of oxygen to produce an energy dense fuel that is fairly clean burning. This process is called pyrolysis and it removes all the moisture and fumes so that the avid BBQ enthusiast will be able to cook their food without coating it in a black smoke of tiny particles.
The BBQ itself is designed to control the combustion process. By opening and closing vents the user is able to regulate the flow of oxygen to the fuel. This directly affects the combustion rate, the rate at which energy is released in the form of heat.
And, as with any cooking process, heat transfer is an important consideration. When the coals are glowing hot they are emitting a lot of their heat as radiation. Radiation requires a direct line of sight and this is what causes one side of your food to get a nice sear on it before you flip it. When the lid to the BBQ is closed the air inside heats up and this allow for some natural convection, heat transfer from the hot air moved by its change in buoyancy (hot air rises). There is also some conduction, from relatively still hot air and the heated metal components that compose the grill (not to mention conduction through the food itself). Each one of these modes of heat transfer provide a different aspect to the grilling process. Radiation causes the sear, conduction is responsible for the grill marks and convection is responsible for the even heating and temperature of the food.
A deeper understanding of any process can lead to better results and engineering gives perspective into many of these processes. As far as grilling goes most of it can be picked up from experiences, but isn’t it more fun to know why these things happen! Happy Father’s Day to all the dads out there, no matter who does the grilling!