How Does A Stove Provide Heat

Heat and Its Control

Perhaps no single factor is more important to man's evolution than his learning how to generate and control heat. The ancient Greeks realized this and developed an elaborate myth about Prometheus, the fire-bearing Titan god who stole fire from the gods for the benefit of man­kind. For the Romans, the Vestal Virgins were keepers of the sacred fire.

Man, of course, understood the workings of fire long before scientists were able to measure and explain the phenomenon, because that understanding was essential for survival. He needed fire to cook his food and to keep his body warm in winter. How man gained more and more control over heat and utilized it to forge his tools and weapons is fascinating in itself, but what con­cerns us here is (1) the nature of heat, (2) its effects, and (3) the factors involved in the combustion of wood and the transfer of the resulting heat to the surrounding atmosphere or living space of man.

How Hot Is Heat?

The term "heat" is used in a number of slightly dif­ferent ways. First, there is the sensation of heat. Our central nervous system is extraordinarily sensitive to heat or the lack of it, at least within a limited range. This range of heat we call "temperature," which is the objective measurement of the degree of hotness, or just exactly how hot something is. Our perception of the degree of heat in a room can often be influenced by the health of our body at the time or by our experience of heat immediately preceding our entrance into the room. For example, we often feel "chilled" when we are sick with a cold although the room temperature may be as high as 80 degrees Fahrenheit. Likewise, an outdoor storm cellar with a consistent temperature of 55 degrees F will seem quite warm to us when we step into it out of a subzero climate. Our perception of heat, then, is a psychological phenomenon that is relative to other expe­riences. Temperature is not. It is an absolute measure­ment of hotness.

Retained Heat

We also speak of heat in terms of quantity. A bathtub full of hot water (Fig. 1) contains a much larger quantity of heat than does a shallow washbasin similarly filled.

Fig. 1. There is more heat in a bathtub full of hot water than in a basin similarly filled.

Or, expressed differently, it takes a lot more heat to raise the temperature of the water in a 60-gallon water tank one degree than it does the water in a 20-gallon tank (Fig. 2). (It costs a bit more money, too!)

Materials like iron and steel will retain more heat over a longer period of time than will an equal quantity of copper or tin. In fact, it is just this ability to "store" large quantities of heat that makes iron and steel ideal materials for stovemaking. They do not store heat per­manently, however. They merely absorb large quantities of heat and then release (radiate) it more slowly than do most other materials.

Radiant Heat

This radiation, or "radiant heat," is what warms our skin when we lie in the sun or reddens our face when we sit near a big potbelly stove. Radiation (of the type we are talking about now) is converted into heat when it strikes an absorbing substance, such as our skin.

Fig. 2. Takes more heat to raise 60 gallons one degree than 20 gallons one degree.

The transfer of heat energy by radiation and absorption is a most important aspect in our consideration of wood-burning stoves (Fig. 3).

The sensation of heat is, therefore, the goal to be reached. Measuring heat is a means of determining how efficiently we can attain that goal. Containing heat in large quantities and allowing it to radiate and diffuse is the means to the end.

Tags: stove heat, wood burning stoves