Which cooling air supply system is better for a high heat density room: underfloor or overhead?

The performance of the following four air flow systems are compared: (A) underfloor air supply/overhead return; (B) underfloor air supply/horizontal return; (C) overhead air supply/underfloor return; and (D) overhead air supply/horizontal return. The underfloor supply/overhead return system is best, because under the same heat density and the same supply air temperature, it requires the lowest supply air flow rate to realize the same average temperature and temperature distribution conditions. A ventilation ratio model for the system is proposed. Experimental results are included in this simple mathematical model. The model shows that the average inlet air temperature depends only on the ratio of supply flow rate into the room to equipment intake flow rate