For the sake of discussion, tell me how water can move so fast through a radiator to shed it's heat and yet pick up heat in the engine moving at the same rate. Heat transfer happens on the molecular level and the speed the water flows across the exchanger would be meaningless I would think. I'm no thermodynamics engineer but this makes sense to me. If the speed of the water were a factor, then the water would not pick up the heat in the first place.
Set me straight if I am wrong.

 

Fixnair: The heat transfer is much more efficient in the engine where the water directly contacts the hot metal than in the radiator where the water has to transfer it's heat to metal and then to the air. To demonstrate, stand outside when the temperature is 75 degrees and you will not feel cold because your body heat is transferring to the air slower than the body is regenerating the heat. Now stand neck deep in a swimming pool that is at 75 degrees and you will get cold rather quickly because your body heat is transferring to the water much faster (more efficiently) than it is being replaced. The water must stay in the radiator much longer to release the heat it picks up in the engine. Thermodynamics says heat can move to a colder area (be removed) cold cannot be added.