Hi Christep & 25F,
To add on from what's been said above;
The 747-400's have a system known as A.C.C.M. This automatically regulates the temp at 24C after an hour of manual intervention.
Scenario:- Flight deck set the temp on the dial at the one O'clock position (22C-23C) during preflight (assuming that is as comfortable as they felt when they walked up to the flight deck!).
If the purser now feels that say the Economy section is too hot he/she can adjust the temp accordingly at a panel near her/him.
About an hour in cruise the ACCM kicks in and re-adjusts the temp to 24C and stays there until re-adjusted then an hour later kicks in again...........and so on..
In my company when the load is high and esp during meal service, crew are encouraged to turn on a Higher Flow of air for a period at the descretion of the Crew. This however increases fuel consumption.
During climb and descent the rate of airflow as defaulted to high.
Hope this helps Cheers.