how many holes to drill in thermostat to increase cooling efficiency?

[brett_celicacoupe]

you also need to remember that with thickness, the air temperature increases the further it goes through the cooler. so effectively the last 50% thickness of the radiator is doing 25% of the energy transfer

[oldcorollas]

ive spoken to a couple people who have done heat and mass transfer subjects and they say that increasing fluid velocity will always increase the amount of heat transfer.

yes and no.

the actual amoutn of heat lost from system is function of the temp difference between rad and air, and the velocity of the air.
the higher the temp of the water in the rad, the more heat that will be lost.

but at higher velocity, the amoutn of heat lost per unit coolant will be lower, so the temp of coolant returning to the engine is higher.

engine works same way, but in reverse.. you need lower temp coolant to have a higher temp difference, to be able to transfer more heat....

so in the end, it is a balance bwtween the temp differences of the air/coolant, and the engine/coolant... but the engine can tolerate lower temp difference as the coolant has better transfer due to direct contact of solid and liquid...
there will be an optimum fluid velocity depending on the heat loss from radiator and heat generated by engine.

edit: can you move the oil and steering coolers to diferent air? so they don7t obstruct or heat the air for the rad? can the aircon or IC bve moved forward, adn then some of their exhaust air ducted under rad?

[Draven]

edit: can you move the oil and steering coolers to diferent air? so they don7t obstruct or heat the air for the rad?

sounds like your best/only optiopn

[The Real Roadrunner]

can you measure the temps at various places on the core? perhaps its only using 1/2 the core for 80% of the flow?

you could convert it to a triple pass as ive had to do this on a few cars, it gives more tube length but lowers overall flow slightly.

Sillycars, yep deadly, ive had them cause more problems than they fix.

cheers
linden

[SillyCarS]

ive spoken to a couple people who have done heat and mass transfer subjects and they say that increasing fluid velocity will always increase the amount of heat transfer.

yeah ive taken fluid mech and heat transfer and have had to design exchangers on an industrial scale, for instance geothermal power.

yes the radiator doesnt follow a linear relationship between the amount of the metal (surface area) in contact with air (at a given velocity) and its abilty to cool. however, the temperature that you are comparing with half way through the radiator of a 3 core will not be as intense as the temp half way through a 2 core. as the heat is being dissipated through more metal. i say this in theory as i have not got the experience of actually fitting and seeing the results first hand. thats why i begged to ask the question, im glad OC joined in here too

EDIT: thanks linden

[SillyCarS]

the actual amoutn of heat lost from system is function of the temp difference between rad and air

this is a great point.

the next time your having a few bevvies with friends and you run out of ice, see what happens when you put hot water in your ice cube tray and put it in the freezer

EDIT: fuckin brain wave!

this supports lindens theory also that a 2 core is more effective than a 3 core, as the temp difference between the two heat reserviours is greater in the 2 core, increasing the amount of heat being transferred

i believe this is Newtons law of cooling? it literally has nothing to do with surface area and fluid flow

[oldcorollas]

from vague memory from olden days, the 3 cores were also fatter tubes, which obstructed more? and actually had less rows then the thin cored stockers = less surface area..

as you know, the heat lost is a function of temp difference, and flows.. the temp difference of the air to core for third row is much lower..
even if we assume the first 2 rows act as a 2 row, then the hot air exiting the first 2 rows reduces the efficiency of the last row by quite a lot (heck, you can calculate it better than me ).
assuming no increase in resistance, 3 core will be better, but not 50% better,... maybe 5%? 10%?... almost nto worth it anyway..
but if the addition of third core restricts the air flow (ie, volume), then the temp of the air rises as it passes over core slower and third row does nothing.. it doesn7t take much increase in air resistance, combined with increase in air temp.. top make third row useless..

in summary.. in theory, with litle extra obstruction, 3 core i sbetter, but not that much better.. but in practice, the obstruction makes the difference not worth the expenditure, when better thought into air flows and pressures may make much more difference

[SillyCarS]

sounds like your best/only optiopn

ceramic block?

[thechuckster]

fwiw: wilbo's MZ12 has same motor & box, a (de-gassed) AC cooler, a fatter FMIC and the trans cooler out front. Twin AU thermo-fans pull the air thru the stock 3-core factory radiator. Cooling is not an issue for that car.

Agreed that Townsville has higher humidity but we (Brisbane) are no slouch when it comes to hot and humid days.

Also, we're not dealing with alloy radiators.

The telling tale is the increase in coolant temp based on road-speed... that's usually an indicator of poor flow (blocked tubes) thru the radiator or insufficient fin area for conducting heat to air.

My own experience with the 18RTE was that a 3-core combined with a rear shroud and a single thermo fan did a lot better job than the 2-core with twin fans. The volume of air shifted was still significant and the heat transfer from coolant to air was more than effective for the same engine with a leaner/hotter tune.

Stu: the 3-core I got was an off-the-shelf core from Adrad fitted/stretched to the 2-core end-tanks. The tubes are the same size as the twin-core. I have no idea about fin density

[The Real Roadrunner]

this supports lindens theory also that a 2 core is more effective than a 3 core, as the temp difference between the two heat reserviours is greater in the 2 core, increasing the amount of heat being transferred

as per what OC said above RE the lesser efficiency of the extra core then compuond that with further restriction of airflow through the cores and you'll start to see why it becomes more of a problem.

hence the reason i V mounted my corollas rad/IC cores it gives more frontal area for the air to pass thru and at the same time it only needed to go thru 70mm thick cores rather than 140mm of cores.

on a 34*C day at oran park with average rear wheel speeds between 150-200kph and the average vehicle speed between 80-140kph with revs constantly above 4Krpm it would hold a water temp value of 86*C and a manifold air temp of 51*C even with the vehicle spending most of its time around 30-45* from the direction of travel. and it would do it for 10mins at a time. most cars would overheat in less than 5mins.

cheers
linden

PS did you read the link i posted earlier?

[wilbo666]

fwiw: wilbo's MZ12 has same motor & box, a (de-gassed) AC cooler, a fatter FMIC and the trans cooler out front. Twin AU thermo-fans pull the air thru the stock 3-core factory radiator. Cooling is not an issue for that car.

Note: I did have cooling issues when doing boost testing (i.e. stop, take off, stop take off, etc), but this was before I fitted a panel between the bottom of the front of the bumper and the first traverse rail to force air through the rad...

After than I no longer had cooling issues. No AC tho...

You prbly don't have a panel in the location I installed one, and it might not be that easy for you to fit one, as my IC is mounted a fair bit higher than yours so my panel is pretty well just flat... I should get a pic for you

Cheers
Wilbo

[thechuckster]

wilbo: the AC radiator is still there tho - so it adds a restriction to the air-path to the radiator.

Linden: yeah - i did read thru the brindabella thread - and the block-to-fluid heat transfer argument makes perfect sense ... but I think the water-to-air heat transfer mechanism needs a slightly different approach as it's not a closed-loop system like the coolant path and it's working with different media (e.g. air)

But we're hijacking Brett's thread so i'll stop now

[wilbo666]

wilbo: the AC radiator is still there tho - so it adds a restriction to the air-path to the radiator.

Yeah the condenser is there, but it isn't generating any heat

If I was brett I'd be getting a cheap eBay alloy rad, and seeing how it goes

Also fitting an engine driven fan should be easy as for him

Cheers
Wilbo

[cambelt]

As a rule taking the thermostat out in a engine that runs a bypass thermostat will make it overheat as the water just circulates around the bypass andnot thru the rad .
Drilling to many holes in a thermostat can creat a simmiler situation .
In relation to water hammer by drilling a hole in the thermostat ive found the oposite, with some bleed all the time clears any air thats in the system.
Dave

[Billzilla]

In relation to water hammer by drilling a hole in the thermostat ive found the oposite, with some bleed all the time clears any air thats in the system.
Dave

I was talking about water hammering, not air.