It seems to be a widely spread practice on the 737-800 to turn off the left recirculation fan in order to keep the noise level down in the cockpit. If I remember correctly, the purpose of the recirculation fans is to reduce bleed air demand, hence reducing fuel consumption.
Can anyone tell me if there really is a noteable difference in fuel consumption when the left fan is ON instead of OFF? Are there any concrete numbers (percentage or kgs per hour)?
Anxiously awaiting enlightenment...!
