Heat transfer system and method of production

It is established that thermal energy can be effectively recovered from the air which is pumped out from a room or from a building by adding this thermal energy, in dependence on the season, using a number of heat tubes functioning in two directions, to the fresh air fed into the room or into the building. Thus, for instance, the entering warm air in the summer can be cooled by the pumped-out cool air and, in the winter, the entering cold air can be heated by the warm air going out. For an installation of this kind a great number of comparatively long heat tubes with small diameter is used. These tubes have ribs in between the two air flows to attain a heat exchange. (orig./TK)