Car radiator heat transfer

[mzamora]

Hello!

I've been dealing with the idea of using a car radiator for cooling an electric engine. The engine has the connectors made for hoses and it can be cooled with glycol/water (50/50).

But, I can't find any good piece of advice related to the heat transfer coefficient of any car radiator nor the head loss of the water that goes inside it. I know I can make a rough guess, but I'd prefer not.

The only experimental values I found:
- A 4025 Btu/min car radiator and its curves (of course that heat depends on the flow, at least)

http://www.maplesoft.com/view.aspx?SF=6403/Radiator.pdf‎

- This curve on slide 19

http://es.scribd.com/doc/35669547/Heat-Transfer-in-Radiators

that looks like a good piece of info, but has no references

Do you know more about this topic? I saw that there are papers related to nanoparticles used to improve cooling properties, but also no detailed info. It's important to note too that the temperature ranges will probably differ.
For now, I'll make a wild guess and let fly some numbers.

 

[EdStainless]

If you have a specific new radiator then the mfg should have published design curves the cover delta T, flow, delta P, and Q at various loads.
Still it sounds like you are in for a bit of testing.
What will you be using for a pump? That will make a big difference.

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Plymouth Tube

 

[mzamora]

I wish there were design curves, but I haven't found them. I'm not buying an special radiator, but a spare one for some small car.
For the pump, I'll probably use a DC pump like this one

http://martinsliquidlab.org/2011/03/09/laing-ddc-1-ddc-1t/

 

[willard3]

You can estimate the cooling required for the Hp/fuel rate of the engine on which the radiator was used.

 

[mzamora]

Yes, I can guess a rough estimate that way, BUT this depends on the rpm of the motor too. With a DC pump, revolutions and flow will be lower, changing the regime of the radiator...

 

[LittleInch]

You appear to have at least 5 variables - inlet water temp, air temp, water flow rate, air flow rate and radiator efficiency / no of fins not to mention cross flow or return flow or vertical flow, I'm not surprised you can't find any reference material. My start guess is that with a decent fan speed (take the fan from the same car), then at 90C in you'll be capable of emitting something like 15 kW.

I hope you've just made an error in listing those DC "pumps". They are minute compared to the flow in a car radiator. What size motor are you talking about cooling here??

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mzamora]

It's an 45 kW electric motor. Worst case scenario, it'll leak 6kW as heat. That's why I'm trying to put a small pump. I put a larger pump of the same king and prices go from USD100 to USD400 which is too much for us.

 

[LittleInch]

There are small pumps and very small pumps. Work out the water flow rate needed to carry away 6kW of heat based on say a 20C rise in temperature then go looking for your pump. Also check out the flow and temp rise of the cooling water from the motor supplier as it all depends on how well the HX inside the motor is designed. I think you'll find it needs much more flow than the micro DC pump you list in your earlier post. Don't forget you need a fan to blow air through your radiator as well. Car radiators have a fine fin arrangement and whilst you will get some convection current going on, it almost certainly won't be enough for 6kW from a small car radiator and the radiator will be designed for vertical mounting.

I think you're concentrating on the wrong thing.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[1gibson]

Check into automotive intercooler pumps. 1999+ ford lightning, 03/04 mustang cobra, use a nice bosch centrifugal pump. Should be within your price range and I am guessing higher flow than the one you listed. On a related note, the ballpark heat loads from a water/air intercooler might be closer to your electric motor than to an internal combustion engine. Check out the rest of the OEM heat exchanger system, I don't think there are fans so you would have to find some. The heat exchangers are a common aftermarket upgrade, so I am guessing you can find good data on the OEM heat exchanger vs aftermarket upgrades.

If that doesn't pan out (gut feeling says it will put you pretty close) then look for other applications that are similar to what you are trying to do. Maybe also look into automotive heater cores, you'd just be using it backwards and you'd have no real starting point for a pump.

 

[mzamora]

Oh my! 1gibson that pump is awesome! Too bad I'm not in the US, but I'm gonna look for it next monday.
Thanks for the advice LittleInch, but money is a factor too. With that in mind, car radiator seems to be the cheapest choice.
Those temperatures of the heat exchanger I haven't find them neither.

 

[LittleInch]

If you want cheap then get a dishwasher pump, they work at high temps and run continually at reasonable flows. If you've got a 45 kw motor you must have a decent power supply.

I kind of struggle to see why you're going to all this trouble, but it's been fun commenting on it....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[tbuelna]

mzamora-

I don't know of any automotive engine coolant heat exchanger that is designed for rejecting a 6kW load. That is a far smaller heat load than any automotive application requires.

Instead, I'd suggest looking at commercial liquid-to-air heat exchanger systems that use an electric fan.