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Diagramatic operation of a thermal wheel Ljungström Air Preheater by Swedish engineer Fredrik Ljungström (1875–1964). A thermal wheel, also known as a rotary heat exchanger, or rotary air-to-air enthalpy wheel, energy recovery wheel, or heat recovery wheel, is a type of energy recovery heat exchanger positioned within the supply and exhaust air streams of air-handling units or rooftop ...
DOAS air handling unit with heat recovery wheel and passive dehumidification. A dedicated outdoor air system (DOAS) is a type of heating, ventilation and air-conditioning system that consists of two parallel systems: a dedicated system for delivering outdoor air ventilation that handles both the latent and sensible loads of conditioning the ventilation air, and a parallel system to handle the ...
For both, a 20-inch (500 mm) box fan makes the last side of the cube and is duct taped to the filters, sealing the system so that air is drawn through the filters and out of the box. [ 21 ] [ 16 ] Rosenthal later improved the design by adding a shroud on the fan: this cardboard cutout covers the corners of the box fan to improve the system’s ...
Air streams are mixed to save energy and improve energy efficiency by partially recirculating conditioned air.. The most common application for an air-mixing plenum is the mixing of return air (or extract air) with fresh air to provide a supply air mixture for onward distribution to the building or area which the ventilation system is serving. [1]
The duct flange normally has 3/4" bolts at 6" nominal; spacing. Duct flange angle thickness needs to be designed for duct plate tensile stresses, as flanges will bend. 5/16" or 3/8" angle thicknesses are common. See above photo of round duct elbows, transitions, and stiffeners. The duct elbow radius is from 1 1/2 to 2 times the duct diameter.
Some HRSGs include supplemental, or duct firing. These additional burners provide additional energy to the HRSG, which produces more steam and hence increases the output of the steam turbine. Generally, duct firing provides electrical output at lower capital cost. It is therefore often utilized for peaking operations.
Box connectors join conduit to a junction box or other electrical box. A typical box connector is inserted into a knockout in a junction box, with the threaded end then being secured with a ring (called a lock nut ) from within the box, as a bolt would be secured by a nut.
The fan maintains a constant static pressure in the discharge duct regardless of the position of the VAV box. Therefore, as the box closes, the fan slows down or restricts the amount of air going into the supply duct. As the box opens, the fan speeds up and allows more air flow into the duct, maintaining a constant static pressure. [11]