Rotary heat exchangers
What is a rotary heat exchanger?
The short answer: a rotating wheel with a multitude of small ducts made of aluminum is what a rotary heat exchanger consists of.
The extract air is cold and cools down the ducts which transfer the cooling to the hotter supplied air. Cooling energy is very effectively recovered (up to 86%) whilst moisture is recovered with a sorption-treated rotor.
Different types of rotors
Rotary heat exchangers from Swegon are available in three different variants:
- Maximum Temperature Efficiency (MTE) which has the highest temperature efficiency
- Standard Temperature Efficiency (STE) is the trade-off between high temperature efficiency and lowest possible pressure drop
- Maximum Pressure Efficiency (MPE) offers the lowest possible pressure drop.
All performance types can be selected with different materials.
The combination of different performance types and various surface treatments provide great flexibility, allowing optimisation while meeting different needs.William Lawrance, Product Group Manager, Swegon
The combination of different performance types and various surface treatments provide great flexibility, allowing optimisation while meeting different needs.
Different types of rotors
VARIOUS SURFACE TREATMENTS
Aluminium rotors are normally used in commercial buildings where temperature efficiency is most important. Sorption rotors are used when moisture is to be recovered for both summer and winter operations and epoxy rotors are used when there is a risk of corrosion attack, e.g. in coastal climates.
The rotor recovers both heat and cold, and with a sorption-treated rotor it also recovers moisture. During summer operations, the heat exchanger “dehumidifies” the outside air, which reduces the moisture precipitation in the cooling coil - the latent cooling capacity - and lowers the overall cooling capacity. This is not only reducing operating costs, but also lower investment costs and improves comfort in the winter.
Winter operations usually mean a dry indoor climate, but a sorption-treated rotor recovers the moisture content of the extract air and increases the moisture content of the supply air.
Humidity control and optimisation
Maintaining acceptable humidity levels is key for providing optimal comfort and limiting the spread of diseases. Sorption rotors are very efficient in recovering humidity - 70-90% humidity recovery efficiency can be achieved using modern coating technology. Both temperature and humidity efficiencies are controlled with rotation speed. By controlling the heat exchanger’s rotation speed, humidity recovery can be optimised.
GOLD units with RECOsorptic heat exchanger has a built-in function to recover and maintain indoor humidity levels, enabling an optimal indoor climate.
Learn more about our solution for hygrostatic rotor control.
Minimising internal leakage
While rotary heat exchangers offer high temperature efficiency, there is a risk of extract air being transferred to the supply air. Internal leakage needs to be avoided because it adversely affects the air quality and the energy consumption.
Leakage can be divided into two types:
- Direct leakage past the seals
- Carry over
All types of leakage must be considered when calculating specific fan power (SFP), using defined methods for measuring the performance of heat exchangers including the OACF and EATR.
Learn more about how to minimise internal leakage and what to consider when calculation SFP on Swegons website.
For a wide range of applications
Rotary heat exchangers provide optimum temperature and energy efficiency and are suitable for most applications, except when there are strict requirements around odour transfer and hygene. Different types of rotors makes it flexible to suit offices, hotels, schools etc.