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Enthalpy exchangers work based on the principle of heat and moisture transfer between two parallel airstreams. The main steps involved in the operation of an enthalpy exchanger
are as follows:
1. Exhaust Airflow: The first step is the extraction of stale air from the building. Usually, a portion of the indoor air is continuously exhausted from spaces such as bathrooms, kitchens, and other areas where humidity and pollutants are generated.
2. Heat and Moisture Recovery: The extracted air passes through one side of the enthalpy exchanger, while the other side receives fresh outdoor air. The exchanger's core, typically made of plates or a matrix with high heat and moisture transfer capabilities, separates the two airstreams.
3. Heat and Moisture Transfer: As the airstreams flow in close proximity on either side of the core, heat and moisture are transferred from the outgoing air to the incoming air through conduction. Sensible heat (temperature) and latent heat (moisture) are exchanged between the airstreams without mixing them.
4. Preconditioning the Incoming Air: The incoming fresh air absorbs the heat and moisture collected in the core, which helps to preheat or precool the air, depending on the climate conditions. This process reduces the energy required for heating or cooling the air when it enters the building's HVAC system.
5. Supplying Conditioned Air: The conditioned and preprocessed fresh air is then supplied to the building's indoor spaces through the HVAC system, providing ventilation while minimizing energy losses.
6. Discharging Exhaust Air: The air that has already transferred its heat and moisture to the exchanger is expelled outside the building as exhaust air, completing the cycle.
By recovering and reusing the energy from the exhaust air, enthalpy exchangers effectively reduce the energy demand of the HVAC system, improve indoor air quality, and enhance overall energy efficiency in buildings.