Circulation and exhaust ventilation systems are designed to organize high-quality air exchange in various premises. The indoor unit of the ventilation unit ensures the supply of fresh air, and the exhaust part vent out the unrequired air out from the room. The number of times the change of air takes place in a room or space in an hour is called the air change rate. For different premises, Building Standards and Rules regulate different measurable values, but in any case, this coefficient is not less than 3. That is, the air in the room is replaced at least three times per hour, and together with the outflow air, the heat “leaves” the place.
To maintain the temperature balance, the supply air must be heated to a temperature of at least + 18 degree centigrade before it is directly supplied to the room. You can partially recover the lost heat with the help of recuperator. Recuperator is a system with a mechanisms that produce heat exchange between the exhaust and intake air flows inside the air ducts. But in most if not all the cases, this is not enough, and channel heaters are installed for the temperature treatment of the supplied air into the section of the duct ventilation.
For the first time, the prototype of the channel heater was applied in St. Petersburg in 1835 to heat the Imperial Academy of Art. At that time, this heating technology was beneficial. One Ammos heater could replace more than 30 heating coils (similar to modern day centralized water heating systems). Later, the Amosov furnaces heated the Winter Palace, 55 large and 29 small fire-air boilers worked for its heating. But, despite all the advantages of the revolutionary technology at that time, the prototype of the duct heater had significant drawbacks:
- Air flows in the air ducts provoked a constant vibration and noise;
- Atmospheric extremities during thunderstorms forced loud crashes to be made by the ventilation ducts;
- The air ducts overheated and quickly spoiled nearby furnishings: paintings, and even furniture.
It was the third flaw that made it necessary to abandon the use of fresh air fired heaters and in 1912 the last heater was dismantled. However the idea of space heating through fresh air did not die, rather it was simply put aside for tens of years before the advent of new technologies.