Return air
The air return air duct will be moved by the difference in pressure, the air ducts, being on the bottom static head, than a room. Such a movement will be radially towards the entrance and non-directional. At a distance of 1 m from the grid, this pressure gradient will be low enough to return grilles can be located close to the power grid, the provision of General circulation provides coverage of the space. On Fig. 24.17(a), return air grilles may also be in the wall of the corridor, if far enough away from the inputs (see Fig. 24.18).
From the ceiling at the entrance and extract systems, the opportunity is presented to dissipate heat from the light trough. This may reject proportion to needs in cold, perhaps, to 20%, in the exhaust air. The return air is also warmer, improved heat to the cooling coil...
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