How do heat exchangers work?
Heat exchangers transfer the heat energy contained in the exhaust air of a room to the newly supplied fresh air. This is heated almost to room temperature and therefore hardly needs to be reheated. A wide variety of heat exchangers are used in ventilation units. What they all have in common: They are made of many thin, highly thermally conductive aluminium or plastic sheets.
In cross-flow exchangers the warm exhaust air and the cold fresh air are directed in the opposite direction through the exchanger levels. The fresh air heats up almost to room temperature, the exhaust air cools down strongly and condenses. Therefore, cross-flow heat exchangers always require a waste water connection. Measures must be taken to prevent condensation water from freezing, clogging or even destroying the exchanger in winter.
A further development of the cross-flow exchanger is the cross-flow exchanger, where the air flows have to travel a longer distance in the exchanger. Due to the longer
The residence time of the air in the exchanger can transport even more heat energy and the efficiency increases. The better alternative are usually the rotary and battery exchangers
(ceramic heat accumulator).
The rotary heat exchanger is continuously rotated by the air flows. It absorbs heat and condensate from the exhaust air, rotates further, transfers it to the supply air and cools it down. Odours may be transferred from the exhaust air to the supply air, which is why this heat exchanger technology is not suitable for all applications.
Battery Exchangers work very similarly, but the exchanger does not move, but is alternately flown through by warm exhaust air and cold fresh air. The heat and humidity of the exhaust air is stored in the exchanger and then released back into the fresh air, which is heated as a result. These heat exchangers work similarly to a rotor exchanger, but are not necessarily round and can therefore also be used in very compact devices.