The experimental values for the outlet temperature and the heat transfer rate for air are different from the theoretical predicted values for numerous possible reasons. The external analysis of the air flow is operating under an open system. The radiator was tested close to the engine and exhaust pipe, which added surplus heat to the external system. This raised the temperature of the outlet temperature of air. Another reason for a difference between experimental and theoretical values has to do with the assumptions made for the tubes of the radiator. There are two tubes in parallel that carry the water across the radiator. The air at the inlet temperature is assumed to flow over both tubes before it is heated to the outlet temperature. Realistically, the air approaches the first tube at the inlet temperature of air. The air is then heated to a different temperature as it flows across the first tube. Therefore, the second tube of the radiator is not cooled as much as the first. This occurrence raises the outlet temperature of air, which also raises the heat transfer rate. Another assumption that could possibly have affected the results was using an estimated value for the effectiveness. The equation for the effectiveness is only exact when the heat capacity ratio