Abstract
The inherent characteristics of a damper can be defined in terms of the square root ratio of the loss coefficient at the fully open position to the loss coefficient at any other blade angle. It is shown experimentally with these devices that, over a wide range of blade angles, there is a linear relationship between the logarithm of the loss coefficient and the blade angle. A number of blade sizes, shapes and configurations were tested and shown to obey this empirical relationship. It is shown that, with suitable design, the inherent characteristic is an exponential decay. Where the damper is required to modulate the air flow rate with a constant pressure drop in the system, a method of sizing dampers is proposed to produce a near linear characteristic over full travel.
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