Engine cooling 1

[Ibrahim M]

Howdy,

Can someone help me understand the relationship between cooling flow rate and radiator sizing ?

For a given engine, if cooling isnt sufficient, you can :

Increase flow rate, which increase energy removal rate but delta T across radiator will stay the same ?

Increasing radiator area would increase Delta T ?

The way i understand it :

Bigger radiator = extract more heat of given energy source.

More flow rate = convey more energy out of engine


I have a hard time understanding coolant syatem sizing anyone have a book on this ?

Thank you

 

[LittleInch]

Well this is really just heat transfer/ heat exchangers design.

Increasing flow rate will do very little for you. It could marginally increase energy loss as the delta T would be a little bit higher on average, but more air flow might have more impact. The exit temperature it off the radiator though would increase and hence less room to extract energy from the engine.

Increasing area provides more area for the heat transfer to occur.

Basically you need to size the radiator for a certain max air temperature at a certain min air flow to cope with the highest heat load from the engine.

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[enginesrus]

The other option is to raise the engine coolant temperature.

 

[EdStainless]

There are two heat transfer steps at work: engine to coolant, and coolant to air.
Now under steady state conditions they obviously equal each other.
Taking steps in improve one of them without addressing the other gets you no place.
Sometimes you only need to improve one side because the other is over designed.
Heat transfer from a hot source to a good medium (water based) is easy and often works fine.
Usually, the limits are the air side, so as long as the water pump is working well and there are no obstructions (check flow) increasing radiator size and air flow will improve cooling.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Engine cooling systems operate near their boiling point. This makes them sensitive to cavitation. Sometimes it's not as simple as just increasing flow. If your flow is too high and you start experiencing cavitation in the pump flow will drop off rapidly. This can also lead to erosion in the pump, thermostats, and fittings of the cooling system. Industrial engines often incorporate orifice plates in the cooling system. Head tanks or radiator caps will also help.

 

[LittleInch]

Cooling systems normally operate under some level of pressure above atmospheric to counter this effect and prevent boiling of the water, but it won't be as good as a lower temperature for sure.

Ibrahim though appears not to have logged in since posting the question so don't think we can take this much further....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.