We all know that it is necessary to ventilate the houses, commercial premises, offices, etc., but when we are at 0ºC outside it may not seem a very good idea to put air at that temperature in our comfortable environment at 21ºC. To solve this, there are heat recoverers( or energy recoverers), devices that take advantage of the heat from the air that we extract to heat the air that we introduce in our premises
What are heat recovery devices?
When we ventilate a place in winter there is usually an extraction and an air supply, therefore we” throw " hot air into the street and replace it with cold air that we take from the outside, giving an extra job to our heating system.
If we use a heat recuperator the thing changes, the air we extract from the premises, before " throwing” it into the street, we pass it through an exchange nucleus where it gives part of its heat to the air that enters from the outside. We see it clearly in this scheme:
Heat recovery core
There are other types of recoverers, but the most common is the plates you see in the image. The so-called enthalpic or rotary models “play” also with air humidity in addition to temperature, but we will not go into them here.
How much will I save with a heat recovery device?
Let's take an example of an office space that is used 8h a day and has 50 people working continuously.
By having 50 people at the premises we would need an outside air supply of 2. 250m3 / h by regulation. Suppose a certain moment of a winter day with low temperatures around 2ºC, what happens?
Without heat recovery: we will have an instant thermal demand of 30kW of heating, of which almost 15kW correspond to the load due to the amount of air at 2 ° C that we are putting in the premises.
With heat recuperator: now we put a heat recuperator in the same room at the same moment as in the previous case, by regulation this recoverer should have an efficiency of at least 44%, therefore those 15kW corresponding to the outside air would become about 6.6 kW.
As we see, in the second case (with recuperator) we would have a punctual thermal demand of 21.6 kW instead of the 30kW that we would have without the recuperator, obtaining a 28% total savings in the heating of the area.
You can check these resources in various languages about heat recovery: in Swedish - Värmeåtervinning, Danish - Varmegenvinding and German - Wärmerückgewinnung.
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