Enthalpy wheels are starting to become a common device in Heating, Ventilating and Air Conditioning (HVAC) Systems. They transfer heat and humidity between the exhaust and supply air. Their net effect is to bring the supply (incoming) air closer in temperature and humidity to the exhaust air and to reduce the load on the heating and cooling systems.
A well-designed enthalpy wheel will recover 60% to 80% of the energy that would otherwise be needed to heat or cool fresh air. Their installation in a HVAC plat allows to reduce the initial investment and the operating costs.
An enthalpy wheel is positioned so that the exhaust air and the supply air travel through it in opposite directions through separate ducts (see diagram). The incoming air travels through the wheel before it enters the rest of the HVAC system.
As it rotates, it absorbs heat and moisture from the warmer air stream and loses heat and moisture to the cooler air stream. Usually this means the supply air is warmed and humidified in the winter and cooled and dehumidified in the summer.
Most wheels consist of an aluminum honeycomb structure within a supporting frame. The honeycomb structure provides maximum surface area, least air pressure drop, light weight and high structural strength. The aluminum is coated with a desiccant such as silica gel that can continually absorb and release moisture.
Available types are:
- Condensing type rotors: it is the economic solution used in ordinary air conditioning applications. These rotors condense and thus remove the excess humidity in the air.
- Absorbing type rotors: they are used to transfer humidity from one air stream to the other, within certain temperature limits, in comfort air conditioning applications. Surfaces of the rotor have the characteristic of absorbing humidity.
- Enthalpy type rotors: they can transfer high amounts of humidity from one air stream to the other, through the desiccant coated material of the rotor. They are most effective in high temperature and high humidity conditions. Through their ability of pre-cooling and de-humidification, they tend to decrease the total cooling requirement of the system, resulting in application of a smaller size chiller.
Through control of the rotation speed by a frequency converter, capacity can be adjusted based on varying climatic conditions and reduction of airflow thought them in Variable Flow installation.
For more information refer to the available documentation and/or contact Climaeuro Technical Office.
