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I had some time on my hands so I thought I would post some basic information related to the car cooling systems. Basically, as we all know, water moves through the block & heads, absorbs heat, then moves through the radiator where it releases heat. This process is known as convective heat transfer. The study of heat transfer is known as Thermodynamics.
Part 1 - Let's start with the formula for convective heat transfer.
Qrate = h x A x delta T
Qrate = rate of heat transfer
h = convective heat transfer coefficient
A = heat transfer area
delta T = Temperature difference between the water and the component that heat is being absorbed/released to
We have 2 heat transfer processes occurring. One is internal to the engine where for a specific car, the heat transfer area "A" (engine internal surfaces) will always be the same. As the engine makes more power, the delta T will rise as the engine/head surfaces heat up so this will increase the heat transfer. The other factor, convective heat transfer coefficient, is different for various fluids but all increase with higher FLUID VELOCITY. Generally, the higher the fluid velocity the higher the coefficient. The way to understand this is to imagine fluid flowing along a surface. It tends to "stick" to the surface so the velocity at the wall is lower than the average velocity. As the fluid near the wall heats up, the rate of transferred heat goes down. When the fluid velocity is higher, it creates more turbulent flow and this helps to stir or mix the fluid so the heat transfer coefficient goes up and you transfer more heat into the fluid (water).
The same convective heat transfer process is occurring in the radiator but of course it is releasing heat to the radiator core which subsequently is being cooled by air passing past the external fins.
Simply put, with a fixed area "A" to transfer heat, the faster the water passes through the engine (and radiator), the more heat it will absorb. That means for best heat transfer, we do not want to slow the water down.
Same factors apply for radiators. But we can increase the size of the radiator to increase the size of the heat transfer area "A". Obviously, that's why big radiators with large surface areas and big fans are best for controlling water temperatures.
Note: Water is a GREAT fluid for heat transfer because it has a high specific heat capacity. That means it will absorb a lot of heat relative to it's mass.
Next is Part II - Water pumps.
Part 1 - Let's start with the formula for convective heat transfer.
Qrate = h x A x delta T
Qrate = rate of heat transfer
h = convective heat transfer coefficient
A = heat transfer area
delta T = Temperature difference between the water and the component that heat is being absorbed/released to
We have 2 heat transfer processes occurring. One is internal to the engine where for a specific car, the heat transfer area "A" (engine internal surfaces) will always be the same. As the engine makes more power, the delta T will rise as the engine/head surfaces heat up so this will increase the heat transfer. The other factor, convective heat transfer coefficient, is different for various fluids but all increase with higher FLUID VELOCITY. Generally, the higher the fluid velocity the higher the coefficient. The way to understand this is to imagine fluid flowing along a surface. It tends to "stick" to the surface so the velocity at the wall is lower than the average velocity. As the fluid near the wall heats up, the rate of transferred heat goes down. When the fluid velocity is higher, it creates more turbulent flow and this helps to stir or mix the fluid so the heat transfer coefficient goes up and you transfer more heat into the fluid (water).
The same convective heat transfer process is occurring in the radiator but of course it is releasing heat to the radiator core which subsequently is being cooled by air passing past the external fins.
Simply put, with a fixed area "A" to transfer heat, the faster the water passes through the engine (and radiator), the more heat it will absorb. That means for best heat transfer, we do not want to slow the water down.
Same factors apply for radiators. But we can increase the size of the radiator to increase the size of the heat transfer area "A". Obviously, that's why big radiators with large surface areas and big fans are best for controlling water temperatures.
Note: Water is a GREAT fluid for heat transfer because it has a high specific heat capacity. That means it will absorb a lot of heat relative to it's mass.
Next is Part II - Water pumps.