Convection. Radiant heat. Grilling. And how to make our barbecue fire hot fast.
It’s BBQ time and we are hungry! How can we get our barbecue fire hot fast so that we can start grilling, cooking and eating our food, especially those yummy chicken wings?
Radiant heat is heat transferred from the glowing charcoal or coals by electromagnetic radiation to the food. This happens because every heat source also radiates light waves (a type of electromagnetic radiation). When atoms in food absorb the some of this energy, they move and vibrate more vigorously. On a macroscopic scale, this is heat that cooks the food.
In convection, air heated by a charcoal fire expands and rises. As the hot air rises and cooks the food, colder air is drawn quickly toward the fire. This cold air brings with it a fresh supply of oxygen to feed the fire, making the fire hotter. The cold air subsequently heats up and rises too, to be replaced by more cold air and oxygen, thus repeating the cycle.
This flow of hot and cold air creates a draft (just like how a chimney works). Adjusting this draft changes the speed and temperature of grilling. The greater the draft, the more oxygen is drawn in, and the faster the fire will burn. The coals will also become hotter. The increased convection and radiant heat cooks our food more quickly.
In a charcoal barbecue grill, you can control the draft by adjusting the vents under the grill. In many parts of Southeast Asia, however, street food hawkers use a handheld fan to “fan the flames” when they are grilling. Either way, the draft stokes the fire, or more accurately, it stokes the wind beneath the wings. We can do the same for our BBQ!
The science of radiant heat in grilling is also at work for microwaves and toasters. What about the science of convection — which other forms of cooking and types of cooking equipment use it? Share your answers with me!
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photos: in order – istockphoto/4kodiak; depositphotos/aruba2000; macrovector; istockphoto/brittak