An Analysis of Engine Cooling in Modern Passenger Cars

Heat-transfer phenomena characteristic of automobile engines and the requirements imposed by automobile cooling-systems upon coolants are discussed.

Under severe driving conditions, heat transfer by nucleate boiling takes place at the engine cylinders. As a consequence, engine hot-spot temperatures increase with increasing coolant boiling-point. The heat transport to the radiator is proportional to the density and specific heat of the coolant, the difference between radiator inlet and outlet temperatures, and the flow rate. The radiator heat-transfer coefficient is essentially limited by the heat transfer at the radiator air-side.

A correlation has been established between coolant properties and coolant performance in an automobile engine indicating that the safety margin against overboiling increases with increasing density, specific heat, and boiling point of the coolant.