doing this from memory figures will be a bit wrong
and i have taken some liberties to make a point.... its all a bit loose and is based on high school physics
water has a specific heat capacity of about 4200J/KG i.e it takes 4.2 KJ of heat energy to heat 1kg water 1 degree C or K so water is pretty good at not having its temperature increase too much when you add in a load of heat energy
and to lower 1KG of water temperature, by 1 degree, you need to pull out 4200 joules of heat energy
iron
about 500 J/KG of heat energy to raise its temp 1 degree you don't have to put as much energy in to raise its temperature, it gets hot quick.......!
so your 1 KG of iron is going to increase by 8 degrees with 4.2KJ energy and 1kg of water will just increase by 1 degree
in theory it heats up, hot to the touch, 8 time faster
and it will reduce its temperature 8 x faster than water.
Energy goes in and out at the same rate provided nothing else changes
or for the water to get to the same temperature as the IRON you would need to cool 8KGs of iron to get the water to that temperature.
or for every 8 degrees of head temperature with associated heat energy you want to remove from the motor, you need to cool the water by 1 degree in the radiator
its ratio based is what i'm saying even if in a slightly dubious way....
coolant is about 3000 J/kg. trade off the heat carrying capacity for a much higher boiling point and a much lower freezing point. huge benefits....
but it doesn't really matter its still got a much higher heat capacity than the surroundings
brass is 380 J kg its gets very hot (temperature.... burn ya fingers ) faster than iron gets very hot, you only need 380 j to heat 1 kg of it up by 1 degree and it gets very hot way way faster than water. we can use this because it temperature will also go down faster
heat energy transfers better when the difference in temperature between the hot thing and the cold thing touching it is greatest
a really hot brass radiator is shedding heat energy to the ambient temp air faster than a cold one. air cools it quick and water heats it quick...
so we have two things at each end that get very hot fast, and can therefore cool fast
and we have water/coolant transferring the heat energy from one to the other that doesn't particularly. However, we get a great bang for our buck with water/coolant, just by lowering the temperature of every KG of water/coolant by just 1 degree, 4.2KJ energy lost for every kg of water cooled by 1 degree.
it has great heat carrying capacity.
its like getting your biggest wheel barrow out to carry home 1 potato.
then add in
flow speed
convection
the wetting agents in coolant
the raised pressure in the system
the forced air cooling of the brass radiator
and it gets well......really complicated
but ultimately the coolant or even plain water is an open freeway to transfer heat energy rather than a small side walk
total capacity of the system is key you can't have a 500CI engine cooled by a radiator the size of a postage stamp, the coolant or water volume in the system is too small
ignition timing and mixture play a bigger part
not causing the cap to vent with too high pump/heat derived pressure plays a part
you won't notice it has vented......!
total Capacity and some flow is key
making it flow faster is implemented by increasing the pressure at the pump outlet by a known value at any RPM, if you care to measure and keep the temperature stable....however that pressure is added to by an Unknown which is linked to the heat picked up from the block and heads at a specific time, fuel grade, load and rpm when the temperature is not stable. that unknown can result in coolant loss via the cap when you make big changes from standard
what do you have to do to the cooling system if you grout the block? never done it, always assumed that reducing the cooling system capacity by 1/3 to 1/2 would make it only useful for drag racing? street drivable anymore?
Dave
