In HVAC systems, heat exchangers are called HRV (Heat Recovery Ventilation). They extract a certain volume of stale air from a building, and replace it with an equal volume of fresh air from outside.
More complex systems incorporate a moisture exchange system for arid or very humid climates. These systems are called ERVs.
|from |
|return |
|vents | ____________________________
| | | |_____________|__________ _____________|_____________
| | +----> stale 8 \ / 8 # <---- outside
| | _______________8_ \ \ / / _8__#_______________intake
| | | | ^ \ \ X / / ^ ^ |
| v | | f \ _| /X\ |_ / f f |
| | | a \ /XXX\ / a i |
|air | | n \ /heatX\ / n l |
|return | | \/exchngX\/ t |
|duct | | /\XcoreXX/\ e |
| | | / \XXXXX/ \ r |
| | | | / \XXX/ \ |
| | | | / \X/ \ |
| | |_____________|___/ X \______|_____________
| | +----- clean / \ -----> outside
| v | _______________ ________/ \___________________________exhaust
| v | |____________________________|
| to |
|furnace|
|or A/C |
The Heat Exchange Core
/
/ /
/ /o/
/ /o/ /
__________/ /o/ /o/
oooooooooo|/o/ /o/
----------|o/ /o/
|/ /o/
----------| /o/
oooooooooo|/o/
----------|o/
__________|/
Thousands of tubules are stacked together, layered in alternating directions. When the air is forced thru this honeycomb
arrangement, the temperature of outgoing and incoming air will equalize. This means that the stale air sent outside will be cooled by the fresh air coming in, itself warmed coming in. The process works both ways, so in the summer, the process is reversed.
Source: http://energy-publications.nrcan.gc.ca/pub/home/Operating_and_Maintaining_your_HRV.cfm
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