In the previous pages, we have reviewed almost all currently existing heating schemes and boiler pipings, and now we will look at heating contours: radiators, «warm floors», and boiler piping.
All heating devices use two physical processes: convection and radiation. Convection is formation of the upward flow of air near a heated surface. In this case, the greatest quantity of warmth is transferred to the air of the room. Practically all devices which are wall mounted use mainly convective type of heating of the room. Cold air, which has higher density, lies at the bottom of the room and when it is heated by radiators, it becomes less dense and is pushed by colder air, cools a little, becomes more dense and again flows to the radiator. Such a repeatedly iterative process heats all the air in the room. It must be noted that air is heated unevenly: by the floor it is colder, it is warmer near the ceiling, in further corners of the room it is colder, by the radiators it is warmer.
Radiant heating (also called radiation) is a stream of infrared rays from the heated surface of the heating device which increases temperature of other surfaces in the room (walls, furniture, floors). An example of radiant heating can be a «warm floor» system although here the elements of convection of air are also present. The main heat is created by warm (infrared) rays. The temperature in the room is distributed evenly and it is more comfortable for people — is warmer by the floor and cooler at head level. There is no motion of the air and therefore thermal drafts do not exist and dust does not get lifted, a feature of all convective heating devices.
Heating devices can be divided into three types. First, radiant heating devices — these include, first and foremost, infrared ceiling panels and «warm floors» and «warm walls» heating systems; at least half of the heat produced by them is radiant, and the rest is convective. The second type is convective. In these devices, cold air is run through a system of pipes containing hot warmth carrier or through a net of electric resistors, naturally or with the assistance of a fan. Passing by the heating device, the air gets heated and goes into the room where it is mixed. At least 75% of the heating of the air is convective. The third type is radiators. These devices use both types of air heating for the room: convection from 50% to 75% and radiation. Depending on the level of finning of the radiators and arrangement of these ribs, some devices emit more radiant energy and provide less convection of air, while others the opposite — more air convection and fewer infrared rays. Therefore when buying heating devices, you will see the word «convector» on the label, although in fact it is a radiator, but the manufacturer made it in such a way that the proportion of radiant energy in them is less than the proportion of convective energy. The radiators which emit more warmth by convection are more suitable for high rooms and those which emit more by radiation more suitable for low rooms.