Subject : Refrigeration and Air Conditioning

Topic : Psychrometry

Difficulty : Medium

By-Pass factor :

The inability of a coil to cool or heat the air to its temperature is indicated by a factor called by-pass factor (BPF) or Coil Bypass Factor. This inability is due to the coil inefficiency and some amount of air just bypassing the coil without getting affected by it. A coil with low BPF has better performance. BPF can also be defined as the ratio of air which is unaffected by the coil to the total quantity of air passing over the coil.

BPF =$\frac{t_{s}-t_{d2}}{t_{s}-t_{d1}}$ For heating coil

BPF =$\frac{t_{d2}-t_{s}}{t_{d1}-t_{s}}$ For cooling coil