Cooling Load

[repeatoffender]

Im just curious as to how you begin to design your cooling system

How do you quantify the amount of cooling required?

Do you work off of datalogging or incylinder - waterjacket heat transfer modelling

Or a selection of both?

[Maverik]

Look for "radiator design" in the find feature and it will begin to tell you what you need to know. Datalogging to me is the best to use to figure out what your cooling load is. If you can get deltaT across the engine, and an older radiator (both water and air side) as well as pressuredrops you should have a very good idea of what type of loading you are putting into the engine. If you don't have any good logging, modeling isn't a bad idea if you know what you are doing. If not, you might have to guess... a popular number thrown around for FSAE cars is 15 kwatts, but make sure you make a good educated decision before you build anything.
Dan

[repeatoffender]

Thankyou Maverik

I have already read through the radiator design thread. But i am more interested in the cooling load.

assuming 15kW i dont believe is enough. the same as people assuming 1/3 of the power output. cooling load will vary with varying engine operating conditions, notably rpm, throttle and equivalence ratio. so just assuming a number would be highly inefficient

has anyone done some research into this area?

[Travis Garrison]

I believe that's what Maverik was getting at...if you actually want to know you'll probably have to research/test it yourself...but those that have researched it, and most of the sources on the subject are telling you that it averages out to ~1/3 engine output.

[ben]

Originally posted by gOon:
cooling load will vary with varying engine operating conditions, notably rpm, throttle and equivalence ratio. so just assuming a number would be highly inefficient


You have no choice - the capacity of the system to cool is fixed because you have a fixed radiator and a fixed duct. I guess you could use a variable flow rate pump, but in the end a good rule of thumb (1/3 engine power) followed by some testing is in order.

Once again is that not the point of this comp?

Ben

[drivetrainUW-Platt]

Originally posted by ben:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by gOon:
cooling load will vary with varying engine operating conditions, notably rpm, throttle and equivalence ratio. so just assuming a number would be highly inefficient


You have no choice - the capacity of the system to cool is fixed because you have a fixed radiator and a fixed duct. I guess you could use a variable flow rate pump, but in the end a good rule of thumb (1/3 engine power) followed by some testing is in order.

Once again is that not the point of this comp?

Ben </div></BLOCKQUOTE>

you can put the radiator in different places, allowing for more capacity with longer lines, ours is right next to the engine this year, still havent tested to see how it does at holding it to operating temp

[Scott Sinclair]

Get the running time and fuel comsumption figures from a previous endurance event and using the calorific value and specific gravity of the fuel you can work out the total energy produced during the event.

The only assumption you need to make is the amount being produced as heat, which like mentioned above is said to be around 1/3. However the radiator dissipates less than this due to the heat loses through radiation off the block and cooling hoses. Somewhere around 25% of the total is still a conservative guess (imo).

Scott Sinclair
(Ex UWA Motorsport)

[repeatoffender]

Thanks guys for your replies

Scott, the approach is correct and i have access to all of the motec log files from previous comps and during testing.

i am currently looking at correlations between mass flow and heat rejection. i just dont see that sizing a radiator off of 1/3 power is efficient enough for our team.

if you can size your radiator for worst case scenario (which may even be less than 1/3 power) then you could implement control measures to reduce 'waste' heat being rejected to the cooling system, where it could be used elsewhere http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Cody the Genius]

...then you could implement control measures to reduce 'waste' heat being rejected to the cooling system, where it could be used elsewhere.

by control measures do you mean a thermostat? Or were you just joking about having a really neat heated seat and leg warmers?

[repeatoffender]

im talking about the poosibility of a combination of electronic bypass thermostat control along with variable water pump speed and fan control

[Marshall Grice]

exactly how does any of that make for a smaller radiator or a lighter car?

[Scott Sinclair]

Goon,

If you use a "variable water pump speed" theres no need for an "electronic bypass thermostat"...
With an Eletcric water pump, when the waters not hot enough, turn the pump to nearly zero...when the water heats up, turn the pump up. You can then ditch the therostat altogether.

Scott

[repeatoffender]

Scott

Thats not entirely true, its true for controlling temperatures once the engine is already warm. But that solution will not help for cold starts as you still pass water through the radiator.

Im still deciding whether theres a need for that atm with FSAE cars. Probably not though