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# Calculating radiator/fan/flow reqd when low Delta T?

## Calculating radiator/fan/flow reqd when low Delta T?

(OP)
Trying to narrow down what type and size radiator and flow of both the water and air I should be looking at that would give me my best heat exchange efficiencies, if I want to input 50F water into a radiator that will have 100F air (60% RH) blowing through it and my goal here is the cooling down of that outgoing radiator air as best as possible.

I want to see if I can do a little better than just fooling with any random old car radiator and fan, if any can point me to what I might should be looking more at here instead. Thank you!!

### RE: Calculating radiator/fan/flow reqd when low Delta T?

You ndeed to have waaaayyyy more information than you have here to size a radiator, both airside and water side

### RE: Calculating radiator/fan/flow reqd when low Delta T?

(OP)
willard3, Like what?

The pump specs for water and size of fan reqd and radiator, all have to be specified/acquired,
none of are limiting factors that I already have here and must make other components work with.

It's a clean start, looking for whatever combo of radiator, water pump flow and fan cfm will
do best job dealing with this low delta T to extract as much heat from air flow as possible.

I'd only add that I'm wanting to not go crazy exotic or expensive, just best match for commonly
available components.

### RE: Calculating radiator/fan/flow reqd when low Delta T?

Well, for one,
> What is the power that you are trying to remove? This actually covers two things, the mass flow and the heat that's to be removed.
Also, what is the actual available cooling capacity of the coolant? 2 gpm is radically different than 200 gpm.

These two things limit the design space. The flow rates determine the maximum possible heat transfer that can occur.

"my goal here is the cooling down of that outgoing radiator air as best as possible."

This is not a sufficiently solid design goal. "As best as possible" is the theoretical limit, within reason, but that's typically beyond the plausible cost constraints, and provides you with zero margin.

TTFN (ta ta for now)
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### RE: Calculating radiator/fan/flow reqd when low Delta T?

(OP)
IRStuff, OK, let me ask it this way...

If you wanted to most efficiently cool down 100F air with 50F water run through a common car or truck radiator, which kind of car or truck radiator would you choose to use and why that particular one?

Also, seeing as it's designed for much higher Delta T's than this application, would you, if cheap/easy to do, change either the air or water rate of passage through that radiator compared to what it was originally designed for, and why?

Thanks!

### RE: Calculating radiator/fan/flow reqd when low Delta T?

You really do need to define though what you mean by "cooling down of that outgoing radiator air as best as possible"..

"Best" is too vague - do you mean the lowest possible air temperature?, greatest possible efficiency of the whole system ( air fan, pump flow etc??), max air flow? what??

If the former then you need the largest possible radiator you can and the slowest possible air velocity and highest possible water flow to cool the air down as much as possible.

Car and truck radiators are designed to reduce the water temperature and hence they all operate on a vertical or horizontal flow tube system. The air heating up is not their primary duty.

On average they are designed to drop the water temperature about 10F, 6C.
So if you can find out what the water flow was, work out the heat gain in this case in energy terms, apply that to air at 100F, work out what your desired outlet temperature is then you can work out how much air you can pass through your particular radiator.

Lots of variables so I think some sort of testing is required with variable water flow and air flow measuring temperature.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Calculating radiator/fan/flow reqd when low Delta T?

(OP)
LittleInch, Thank you for both pdf's, got them open now to dig into later tonight.

Yes, lots of variables, quickly growing awe here of those who design radiators, pumps, fans, shrouds, etc., specifying the flows through them all, to work most efficiently together as a system.

Only thing I do have nailed down, is water is 50F and air to be cooled is 100F, and without going all NASA exotic or expensive here, I just want to see what I should be aiming for in off the shelf, likely automotive, components, that'll probably work best at cooling that 100F hot air down some with 50F water.

For any given radiator, my variables I can control then, within limits, is pushing water and air through it at varying rates and volumes.

Trying to narrow down here, for this application, what kind/size of radiator to aim at acquiring and then how much air and water to try to move through it.

You'd summed it up pretty well; "If the former then you need the largest possible radiator you can and the slowest possible air velocity and highest possible water flow to cool the air down as much as possible."

Thank you.

### RE: Calculating radiator/fan/flow reqd when low Delta T?

#### Quote (Shane21)

Trying to narrow down here, for this application,

What application?

Having an application means that you know what you are trying to accomplish.

Why are you looking at coils designed to cool water with air when what you seem to want to do is cool air with water.

There is an entire universe of coils designed to do this. And every manufacturer of them has all the information you need handy on their web site.

### RE: Calculating radiator/fan/flow reqd when low Delta T?

(OP)
"There is an entire universe of coils designed to do this. And every manufacturer of them has all the information you need handy on their web site."

MintJulep, thanks, makes sense, Chilled-Water Cooling coils, I'll see what's out there.

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