Heat recovery

Heat recovery

What is heat recovery?

Heat recovery is a process of preheating of cool supply air by warm exhaust air. Warm air is not exhausted through the open window but transfers most of its heat to supply air in a heat recovery exchanger before being exhausted.

What is Heat Recovery Efficiency?

Heat recovery efficiency = utilizing of waste heat for cool fresh air preheat. Heat recovery efficiency must be between 0 and 100 %.

Zero Efficiency is efficiency of open window - warm air is exhausted without any additional use while cool fresh air is supplied to the room which is cooled down to outer temperature.

100% Efficiency (technically impossible) would occur if the supply air heats to temperature of the exhaust air. The room would be ventilated with no energy loss.

Achiavable Heat Recovery Efficiency in the common air-handling equippment false somewhere between 30 to 90 %, while efficiency above 60 % is considered good, above 80 % excellent. The heat recovery efficiency for DUPLEX units is between 52 to 90 % (it depends on the unit size, air flow and the heat recovery exchanger type).

Heat Recovery Application

The heat recovery exchangers are mostly fitted directly in the ventilation units. This allows to use the heat recovery actually in all building types with hygienic mandatory ventilation - appartments and family houses, commercial buildings, swimming pools, industrial buildings.
Lately, due to increasing price of energy, heat recovery is increasingly used in residential buildings. Heat recovery exchangers can be used even in air-conditioned buildings - where during the summer season it serves as "cold recovery" - supplied warm air is cooled by air-conditioned exhaust air.

Calculate the temperature of supply air downstream of heat recovery exchanger and your heat saving.

Indoor air temperature
[5 to 40°C]
Outdoor air temperature
[-25 to 20°C]
Heat recovery Efficiency
[0 to 100%]
Supply air temperature
Exhaust air temperature
 When using heat recovery, it is enough to prereheat 
 the supply air by  °C instead of  °C.
You save reheat by  °C 

Instruction: Enter the indoor and outdoor air temperature and efficiency.

Note: The output calculation is only approximate and does not take uneven flow and possible condensation into account.