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Energy Recovery

April 18, 2011


Energy recovery systems exchange energy between the two counter flowing exhaust and supply air streams pickings up the sensible or both sensible and latent heat from the cooler air stream and transferring to the warmer air stream or vice versa depending on the conditions. The benefit of using energy recovery is the ability to meet IAQ Standard ASHRAE 62.1.2001 and Conserve Energy, while improving indoor air quality, and reducing total HVAC equipment capacity. Incorporation of Energy Recovery Systems also help  Designers, contractors, building owners and operators to reduce CAPITAL AND OPERATING COST of air-conditioning equipment.

The following technologies are available for transfer of energy between the two air streams:

Rotary Energy Exchangers – a rotary heat exchanger has a revolving wheel having a very large internal surface area, positioned between two adjacent ducts with opposing flow directions.

Coil Energy Recovery Loop – Also referred to as the runaround loop. They use standard finned tube coils to transfer heat to and from intermediate working fluid such as water or glycol water solution. A pump circulates the fluid between the two coils in closed loop. They are useful for sensible heat recovery only.

Heat Pipe Heat Exchangers –  Heat pipe heat exchanger consists of a number of independent finned coils. Each tube is inbuilt with a capillary wick material and thermic fluid inside. With the tubes installed horizontally one half of the exchanger will act like an evaporator and the other half like a condenser. They are useful for sensible heat recovery only.

Fixed Plate Exchangers – They are made from alternate layers of plates, formed and sealed at the edges to create two adjacent but separate flow paths. Energy transfer across the plates from one air stream to next is completely passive and driven by thermal gradient.

Thermo-siphon Heat Exchanger – Thermo siphon heat exchangers are similar in operation to heat pipes. They can operate as single coil with sealed tubes, or function with separate evaporator and condenser coils. They depend on boiling for refrigerant evaporation, which requires larger temperature difference.

Energy Recovery Wheels – Energy Recovery Wheel scores over all other types of recovery systems for being the only unit able to deliver latent transfer efficiently.

DRI offers the Highest Recovery Enthalpy Wheels in the world (Aluminum substrate coated with a choice of desiccants). DRI EcoFresh Heat Recovery Wheel, which recovers total energy (sensible as well as latent), assists in meeting all the requirements of Indoor Air Quality (IAQ), humidity control and energy saving. For more, please visit

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