Correct Answer - Option 2 : 0.5
Concept:
By-Pass factor:
The inability of a coil to cool or heat the air to its temperature is indicated by a factor called the by-pass factor (BPF) or Coil Bypass Factor.
This is mainly due to coil inefficiency and some amount of air just bypassing the coil. A coil with low BPF has better performance. BPF can also be defined as the ratio of air that is unaffected by the coil to the total quantity of air passing over the coil.
\(BPF =\frac{{{T_{coil}} - \;{T_{air - out}}}}{{{T_{coil}} - \;{T_{air - in}}}}\;\)
Calculation:
Given:
Tcoil = 30°C, Tair-in = 20°C, Tair-out = 25°C
\(BPF =\frac{{{T_{coil}} - \;{T_{air - out}}}}{{{T_{coil}} - \;{T_{air - in}}}}\;= \frac{{30 - 25}}{{30 - 20}} = 0.5\)
∴ the by-pass factor of the heating coil is 0.5
