Aluminum Foil Heat Conduction

I know aluminum is a great conductor of heat energy. I also know aluminum is a great insulator of radiant heat energy. � My question: Does wrapping heated food in aluminum foil help keep the food warm?- That is: Does the foil keep food warm by reflecting back the radiant heat emanating from the food, or does the foil allow heat energy from the food to freely pass into the environment via conduction and thus be a poor material for keeping food warm?
- David Levin (age 51)
Edgewater, MD USA

The effect of trhe aluminum foil on the cooling depends on details. Since the foil wraps around the food, the main directions it conducts heat don't matter. The heat flow is at right angles to the foil surface. The shielding of the radiation by the foil should help reduce the heat flow. If, however, the foil sits on some cool material that's a good thermal conductor, then it could provide a path for heat to flow away. So whether it helps or hurts in keeping the food warm depends on what else it's touching.

Mike W.

(published on 10/05/2015)