The thumb of rule for air flow is 400 CFM/ton cooling and 200-300 CFM for heating (with exception of refrigerant heating cylce with heat pump, which requires high CFM), but what is the theoretical ground for this. A few thoughts:
1. Different heat exchange properties when air flowing through cooling coils and combustion heat exchangers.
2. Occupants' Comfort.
3. Different gravities of heated and cooled air.