High altitude operations with piston engines powerplant design optimization part IV: Radiators optimum design

In high altitude operations, the cooling system takes part to the vehicle design optimization process. An integrated design of the cooling ducts is strictly necessary. At high altitudes, the cooling air is taken from high-pressure areas into an alternate, extremely optimized, path. A diffuser reduces the airspeed and increases pressure of the cooling air. Then a group of high performance finned radiators rejects the heat from coolant, air charge and oil. The high altitude, after diffuser radiator performance is discussed in this paper. At first high performance Formula 1 radiators are introduced and discussed. Experimental data are also exposed and summarized. The pressure drop and heat rejection are expressed in function or Re and Pr numbers of cooling air. Then the radiator performance at high altitude is extrapolated from the ground test data. Finally a few suggestions on radiator and cooling ducts arrangement are introduced.