Before we start discussing the construction and principles of operation of individual types of stoves, we will explain a number of concepts, which we will deal with later in the book.

The burning process depends on the amount of air and its composition. Air mainly consists of two basic gases: oxygen forming 1/5 part and nitrogen forming 4/5 parts. Besides, they are in the air. other gases in minimal amounts, such as carbon dioxide and a variable amount of water vapor.

Nitrogen does not keep bodies burning. On the other hand, the combination of oxygen with fuel causes the phenomenon of combustion. The visible sign of combustion is a flame, emission of light and heat.

Obtaining as much heat as possible under the most economical combustion conditions is the task of heating.

Heat is a form of energy, the cause of which is the disorderly movement of molecules. As the movement of these particles increases, the body heats up.

We measure heat in calories, that is, in units of thermal energy, needed for heating 1 g of water by 1 ° C (for example. from 14.5 ° to 15.5 ° C). It is a relatively small unit of thermal energy and therefore in practice the so-called. kilocalories (symbol kcal), i.e. the amount of heat needed to heat 1 kG (1 liters) water from 14.5 ° to 15.5 °, i.e. by 1 ° C.

In addition to specifying the unit of thermal energy, there is also the concept of temperature. Temperature depends on the energy of the movement of individual molecules and indicates the degree of heating of the body or air.

We express temperature in degrees. In Europe, it is customary to measure the temperature with a thermometer with a scale from 0 do 100°, introduced by Celsius. The melting point of ice was taken as the temperature determined at 0 °, and a temperature defined by 100 ° the boiling point of water at normal atmospheric pressure. By the term "thermal effect" we mean the amount of heat released during the burning process.

Heat spreads through:

a) radiation, which means, that body, which have absorbed the thermal energy radiate it directly to the outside,

b) convection, that is, the removal of heat from the heated body indirectly through the generated air currents or a liquid, in the vicinity of this body.

It must be noted, that metals are primarily good conductors of heat, bad wood, wool, air.

Knowledge of this phenomenon is of great importance in the construction of furnaces, as we will see later.

Bodies can have a different heat capacity. This is especially important for the furnace. The heat capacity is the number of calories, which the body can swallow.

Thus, the mass of the furnace may absorb a certain amount of heat, depending on its size.

The concept of heat accumulation occurs as a consequence of absorbing and storing heat, in our case, the heat accumulation of the furnace. This heat storage occurs mainly in the inner part of the furnace structure.