Continuing with the current series, which examines engineering concepts as they are used in the kitchen, this blog will focus on the oven. The oven is a thermally insulated box which can be utilized for baking, cooking and general heating. The first oven was used in Central Europe in 29,000 BC but was not much more than a boiling pit. In 17th century BC Ancient Greeks designed portable ovens from clay, which were mainly used for baking bread. In the early part of the 19th century a coal oven was developed out of heavy cast iron. The first electric oven wasn’t invented until the late 19th century, but it was so inefficient that very few were ever sold. Slowly the technology improved to the point where the conventional oven became a household staple. The modern ovens of today are typically one of two types; either natural gas or electric. The most useful selling point is that ovens can cook in a variety of ways. The most common method is by heating from below for baking or roasting. If the oven heats from the top it can provide broiling or grilling. In order to more evenly cook an object some ovens have a fan and use convection heat transfer.
Thermal Management in an Oven
An electric oven is a fairly simple piece of technology, and works with just a large coiled wire. The wire works like a large resistor which resists the flow of electricity and builds up a large amount of energy that becomes heat. When an oven turns on, an electric charge is sent to one of two sets of coils. The lower coil is temperature controlled and will heat to a specified temperature and remain constant. The upper coil is the broiler coil. When a charge enters that coil it will heat very quickly to its maximum possible temperature without a temperature control until it is turned off. When an oven uses a fan it is known as a convection oven and utilizes convection heat transfer. Convection ovens can roast food more quickly and evenly by the circulation of hot air.
Other Applications of an Oven
Aside from cooking, an oven’s design can be manipulated to provide a vast array of uses. In the industrial field a furnace oven can be used to provide heat to an entire building or to melt substances such as glass or metal. A blast furnace is a particular type of furnace oven, which is associated with smelting, and uses a hot burning, pressurized fuel to produce a much hotter temperature. A kiln is a high temperature oven used in ceramics and cement manufacturing because it can cause minerals to become glassy, solid, and firm. An autoclave utilizes pressure which allows aqueous solutions to be heated higher than their boiling points. Lastly an industrial oven is used similar to a kiln but requires less energy and cannot reach similar maximum temperatures. These ovens are normally all made of heavy walls of steel due to their high thermal mass, and allows for the thermal energy to stay in the oven.
Whether it is at the conventional 190 degrees Celsius to cook chicken, or 820 degrees Celsius needed to melt glass, ovens retain their heat and allow the thermal energy to stay inside the oven. This allows for an efficient thermal environment.