Efficient Gas Stove

Gas stoves are the most popular cooking stoves around the world. The heat from a gas stove is more controllable than an electric hotplate. It is also cheaper and usually more efficient (the in efficiency of an hotplate comes from production and transmission losses of electricity).

Yet a gas stove is a very inefficient device in itself. The inefficiency comes from the use of open flames in the stove. The flame is essentially hot gases. The hot gases are only able to partially transfer its heat to the cooking pot. The rest is lost to the surroundings. This can be easily verified by the fact that the surroundings of a gas stove is significantly warmer than the surroundings of a electric hotplate. The kitchen also gets uncomfortably hot in warm climates.

The open flames of a gas stove is a significant fire hazard. The exhaust from the stove may also buildup dangerous levels of carbon-dioxide in a closed in environment.

I propose an efficient stove design which keeps the flames in a closed chamber. After the hot gases of the flame heats the cooking pot, it is used to preheat the intake air. The exhaust escapes through a chimney which can be ducted outside to keep the kitchen cool and safe.

Please follow the links for illustrations.The cooking pot should make a more or less good seal with the stove when the pot sits on top. Thus the convection loss is stopped.

The stove has two chambers separated by a flower shaped thin aluminum wall. The intake air enters through the bottom of the stove and rises through the inner chamber. The hot exhaust travels down the outer chamber and exits to the chimney. The suction of the updraft in the long chimney helps the hot exhaust to travel down the chamber. A small fan on the chimney can help start the updraft. While the hot air is travelling down, it exchanges some of its heat to the intake air rising through the inner chamber. The large surface area of the flower shaped wall facilitates the heat exchange. The outer wall of the stove may be covered with some kind of insulation to reduce heat loss.

As the intake air is heated as it rises through the inner chamber, the convection current helps it move up wards. The gas enters in to the burner located at the top of the inner chamber through a venturi and create more suction for the intake air.

The actual gain in efficiency is hard to reckon with out lots of experimentation. This was supposed to be my winter project. Never got the time to finish it. I built a model with candles and aluminum foils. It seems to work, but I never had the time to do a controlled experiment. Feel free to try it yourself.

One possible improvement idea is to have corrugations in the flower shaped wall between the inner and outer chamber for better heat exchange.

The design was done in Solidworks. I can post the file on request. (cc)(science commons)