Is it all we have in a radiator to exchange heat? Then no, we are not done yet.
High end car radiators are bit more sophisticated, we have fins like structures inside the radiator pipes. These are added to create turbulence in the water flowing through them. The water flowing through pipes without internal fins is streamline. Thus the heat exchange will be between outer layer of water and the air. As the outer layer of water gets cooler, It reducing the temperature difference between air and water as a result, rate of heat exchange will decrease.
Whereas in the radiator pipes with internal fins, water molecules that exchanges heat with air gets mixed up with hot water, due to turbulence created by these fins. Thus keeping the temperature of whole water uniform and high. In this way a greater amount of heat could be exchanged and coolant gets cooler at a really very fast pace.
What is the function of pressure cap in a radiator?
Temperature of engine goes way much higher than 100 degree centigrade, and water is used as a coolant in cars. But water starts boiling at 100 degrees and get converted into steam. And steam does not exchange heat at a good pace. So how water can be used as a coolant.
To solve this problem pressure caps are introduced in a radiators. Pressure cap does not allow the pressure formed in the radiator to escape created by hot water coming from engine . Thus there is an increase in pressure inside radiator as water get’s hotter. And as we know that the boiling point of a liquid increases if it is heated at a higher pressure. So pressure cap increases the boiling point of water and keeps it in liquid state even at temperatures higher than 100 degree centigrade.
Imagine if pressure in the radiator goes on increasing it could bust the radiator pipes, to short out this problem, pressure cap is equipped with a spring at its bottom, which get’s lifted up as the pressure reaches around 15psi, so pressure cap acts as a valve and release the pressure to overflow tank when it exceeds the limit of 15 psi.
Transmission Oil Cooling
Ever heard of transmission oil used in gearbox and power-steering going into radiator. In high payload vehicles we have to cool down the transmission oil and we use our radiator to remove the heat from this oil. The side of inlet port of radiator is called hot side as hot water from engine enters from this side, as water moves through pipes and gets cool and get’s out of radiator through outlet port called cold side. So we have a cylindrical structure on the cool side of radiator through which transmission oil circulates thus exchanges it’s heat with cold water.
You must also know?
We add anti-freezing additives to the water to prevent it from freezing in winters, especially in Europe, and to prevent engine from corrosion.
For better explanation about how radiator works in automobile watch the video given below: