Radiator Fan Question

Aero · Jun 24, 2004

Ok so here it is.

I have a 2 row Aluminum 27 inch Radiator. Pretty much I am going to be installing two fans side by side 7 inch fans on the outside of the rad. (inbetween the grill and the rad)

Here is the question, would it have better cooling to have them on the top of the rad or the bottom.

The reason being is that I have a trannie cooler on the front as well.

WORTH · Jun 24, 2004

whats wrong with the fan that is on it? Or do you just have extra money laying around this month? I can get rid of that for you if you'd like

PS. if you don't mount that oil cooler properly I'm gonna kick your ass

smokem · Jun 24, 2004

Technical Answer:

Putting the fan on the area of the radiator where the water is the hottest is advantageous because this is where you’ll have the largest temperature difference.

By adding a fan you’re essentially increasing the convective heat transfer coefficient and the increase in the convective heat transfer coefficient from the fans should be approximately the same no matter what portion of the radiator you put them on.

As a result you will see a bigger heat transfer gain in the portion of the radiator that the fans are over if you put it over the hotter part of the radiator.

However, since this reduces the temperature through the cooler part of the radiator, that portion won’t be as effective as it was before thus offsetting some of the gains from the fans.

If you put the fans on the cooler part of the radiator, you won’t lose any performance from the hotter portion, but the gains in the portion of the radiator that the fans are over won’t be a large as if they were over the hotter part of the radiator.

Quick answer:

It’s difficult to tell (without doing calculations) which will net the higher heat transfer rate, however, it’s my opinion that it probably won’t make much difference either way.

Hope that helps

Aero · Jun 24, 2004

WORTH said:
whats wrong with the fan that is on it? Or do you just have extra money laying around this month? I can get rid of that for you if you'd like

PS. if you don't mount that oil cooler properly I'm gonna kick your ass

I like the one I got I spent a good amount of time sandblasting it and painting it

I am talking on the other side of the rad, the front side.

Besides your already getting my clutch assembly

Extra money? naw It all goes to you anyways.

Besides I am running new lines and remounting the current trannie cooler that is attached to the rad.

Aero · Jun 24, 2004

smokem said:
Technical Answer:

Putting the fan on the area of the radiator where the water is the hottest is advantageous because this is where you’ll have the largest temperature difference.

By adding a fan you’re essentially increasing the convective heat transfer coefficient and the increase in the convective heat transfer coefficient from the fans should be approximately the same no matter what portion of the radiator you put them on.

As a result you will see a bigger heat transfer gain in the portion of the radiator that the fans are over if you put it over the hotter part of the radiator.

However, since this reduces the temperature through the cooler part of the radiator, that portion won’t be as effective as it was before thus offsetting some of the gains from the fans.

If you put the fans on the cooler part of the radiator, you won’t lose any performance from the hotter portion, but the gains in the portion of the radiator that the fans are over won’t be a large as if they were over the hotter part of the radiator.

Quick answer:

It’s difficult to tell (without doing calculations) which will net the higher heat transfer rate, however, it’s my opinion that it probably won’t make much difference either way.

Hope that helps

So what your trying to tell me is that I have a 50/50 chance whether I put them on the top of the rad or the bottom of the rad.

It is a crossflow Rad as well.

smokem · Jun 24, 2004

Aero said:
So what your trying to tell me is that I have a 50/50 chance whether I put them on the top of the rad or the bottom of the rad.

It is a crossflow Rad as well.

Yeah. I don't think you'll notice any difference from one location to another.

I'd just put them where it's most convenient.

Pakrat · Jun 24, 2004

I could be wrong on this, but if I am understanding what you are doing it sounds like you are leaving a stock or exisiting fan in, which appears to be a puller in the normal location between radiator and engine and are now looking at installing one on the other side which would be a pusher fan? If that is correct than I beleive that is a big no no. Even though it would appear to be logical, from what I have heard, this can cause more problems and not actaully be a benefit at all. If I misunderstood or am wrong than I'll just shut up and go back to not getting my own car to run.

WORTH · Jun 24, 2004

Pakrat said:
I could be wrong on this, but if I am understanding what you are doing it sounds like you are leaving a stock or exisiting fan in, which appears to be a puller in the normal location between radiator and engine and are now looking at installing one on the other side which would be a pusher fan? If that is correct than I beleive that is a big no no. Even though it would appear to be logical, from what I have heard, this can cause more problems and not actaully be a benefit at all. If I misunderstood or am wrong than I'll just shut up and go back to not getting my own car to run.

LMAO, he's being a PutZ, he hasn't even driven it far enough to warm up yet and he's putting fans on , besides after I'm done with him he wont be able to afford GAS , is it ethical to add all my '46 pickup parts to his Bill???

Aero · Jun 24, 2004

Hey I am just getting the knowledge beforehand why not ask early

You can add all the 46 pick up parts you want as long as the truck gets to stay at my house

Worth can you confirm Pak's concern about putting fans on the front of the radiator?

GaPonyFarm · Jun 24, 2004

You don't want to put both a pusher and a puller fan on the car, you'll ruin the efficiency of each.

WORTH · Jun 25, 2004

Aero said:
Hey I am just getting the knowledge beforehand why not ask early

You can add all the 46 pick up parts you want as long as the truck gets to stay at my house

Worth can you confirm Pak's concern about putting fans on the front of the radiator?

Personally I don't like electric fans at all. The only reason I can see to use an electric fan is if you are racing the car and are trying to squeeze every last ounce of power out of it. There are too many negatives and not enough positives for me to do it.

GaPonyFarm · Jun 25, 2004

I guess you've never been stuck in traffic. That's where an electric fan is worth its wait in gold.

I guess you Cape Cod boys just have it easy and let the chauffeur worry about it! j/k

WORTH · Jun 26, 2004

GaPonyFarm said:
I guess you've never been stuck in traffic. That's where an electric fan is worth its wait in gold.

I guess you Cape Cod boys just have it easy and let the chauffeur worry about it! j/k

I know you were being sarcastic, but most people don't need an electric fan. A good blade and a shrowd does a very good job cooling. I don't live in downtown dallas, so I can't compare what I have seen to those guys, but I have also heard from a lot of people down there that have no problems once they put a shrowd on the car.

You have to keep something in mind when your making improvements to your car. Not all new technoligy is better. Just because they do it on a 2004 car doesn't mean it is superior to what was on a 1965 car. The temps were just as hot in 1965 as they are now and we all managed to drive our cars without carrying a gallon of water in the trunk

The other thing I see a lot of people doing here is going after a solution to a problem before they figure out what the problem is.

We just watched Pakrat replace his ignition system before he figured out why his car wasn't running. Throwing parts at a car is a very expensive way to fix a problem. I hear a lot of people complaining about the amount of money it costs to maintain a classic car, when in reality they are far cheaper than maintaining a 10 year old car. And in the case of mustangs, it's easier to find a part for a 65 Mustang than it is to find a part for a 90 econoline. Trust me I own one, right now I need a throttle cable for it and they are no longer available from the dealer and the aftermarkets aren't making them yet. I'm still in search of that baby.

You have to be patient and figure out your problem before you start spending money on it. Just cause it looks pretty don't mean it works

Pakrat · Jun 28, 2004

In my own defense, I don't think my case is a perfect example to your point (but I do agree) simply because even though my fuel filter was partially responsible for my problem, one of my sets of points was indeed fried, and I had bought the pertronix kit almost a year ago but just never gotten around to installing it until it was finally necessary. My only additional expense (and completely necessary in my eyes) was upgrading my cheap 2 dollar filter with a 9 dollar filter and also buying the flamethrower coil to compliment my pertronix kit. That's one newer fangled technology that I think is absolutely better than the original points.

Now, if you want to site the case a year ago when I replaced my solenoid and starter motor (though the motor was on it's last leg as it turns out) before admitting that my less than one year old battery was actually a dud and had a bad cell, well than that scenario probably better makes your point for you.

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