Cooling Efficiency

J

johnny

New member
May 10, 2011
8,287
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3
For the thermodynamics gurus present. How efficient is liquid to liquid heat transfer - as in our oil and transmission coolers relative to air to
liquid as in the radiator itself? I know it's more so, but not how much more so. Twice? power of ten or more? My only experience is with vapor
phase cooling in UHF television transmitter klystrons. They generated so much heat due to electrical inefficiency the only way you could remove it
was by heat of vaporization. Is there any great value in the outboard transmission coolers? Are we taking aim squarely at our foot if we bypass the
radiator cooler?

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
Other than "more" it would depend on the temp differential of the 2 liquids. (Duh) I think the rad cooler provides some temp stabilization both
directions as the mass of each system can store heat till it can be dissipated (scratch each others back). I don't like the in front of radiator
coolers as they are more like Harleys and Volkswagens (air cooled) when it's hot out the trans is hot, and in winter it runs too cold.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First
 
Hi Johnny

Here is a table that may give you an ideal of the difference
http://www.engineersedge.com/thermodynamics/overall_heat_transfer-table.htm
Air cooled heat exchangers look to be 100-130 for water
Tubular heat exchanger liquid to liquid looks to be 25-200
Plate heat exchanger liquid to liquid looks to be 150-700

A google search of "radiator heat transfer coefficient" will return enough hits to keep you entertained for several hours.

Hope that helps

Dave Mumert

> -----Original Message-----
> Subject: [GMCnet] Cooling Efficiency
>
> For the thermodynamics gurus present. How efficient is liquid to liquid heat transfer - as in our oil and transmission coolers
relative to
> air to liquid as in the radiator itself? I know it's more so, but not how much more so. Twice? power of ten or more? My only
> experience is with vapor phase cooling in UHF television transmitter klystrons. They generated so much heat due to electrical
> inefficiency the only way you could remove it was by heat of vaporization. Is there any great value in the outboard transmission
> coolers? Are we taking aim squarely at our foot if we bypass the radiator cooler?
>
> --johnny
 
> For the thermodynamics gurus present. How efficient is liquid to liquid heat transfer - as in our oil and transmission coolers relative to air to
> liquid as in the radiator itself? I know it's more so, but not how much more so. Twice? power of ten or more? My only experience is with vapor
> phase cooling in UHF television transmitter klystrons. They generated so much heat due to electrical inefficiency the only way you could remove it
> was by heat of vaporization. Is there any great value in the outboard transmission coolers? Are we taking aim squarely at our foot if we bypass
> the radiator cooler?
>
> --johnny

Johnny,

Ready? Take a leak, grab a drink and Hang ON....

To answer your question straight up, Yes But Expect you might like to know why. Vapor phase cooling is a very different animal and I will tough on
that at the end.

Air is handy for cooling only because there is some much of it available. But, eight pounds of air gets you about 100 cubic feet. Eight pounds of
water gets you about one gallon (0.133cuft). You have to have the mass to transfer the heat. This is just one reason that the coolers in a radiator
tank are so small. And there is an advantage to be had by cooling with the temperature controlled engine coolant. If you go to an air cooled heat
exchanger not only does it need to be a lot larger, but it should include some kind of control as neither engine lubricating oil or transmission fluid
like being too cold. Both for the same reason and that is moisture control. An engine can't avoid it because they make water as a product of
combustion and some ends up in the lubrication. The transmission is a passive thing that is the result of heating and cooling.

Transmissions need a cooler because the torque converter makes about 15Hp (38kBTU)of waste heat just dragging you down the road.

So, if I have a Toronado with a 455, where is the lubricating oil cooler for that??
Good Question:
Did you ever try to run with the valve gear (rocker) cover removed? There is oil all over the place and it is on top of the combustion chamber
cooling jacket and when it finally gets out of there it gets to run down the push rod grooves that are also on the outside of the cylinder cooling
jacket until it gets to the pan where it can get some cooling by hanging out in the airflow under the vehicle.

Now, lets look at your vapor phase cooling for a moment. This is something steam engineers know about. A BTU is the amount of heat it takes to raise
one pound of water one degree Fahrenheit. At the pressures you deal with that heat of fusion is 970 BTU/lb. So, if you can boil water and take away
970 with no (little) change in temperature, isn't that just one hell of a good idea? This is why I made a living boiling water.

Now, I hope I didn't loose you here somewhere, but if I did and you can sort of tell me where, I will be glad to try to clear it up.

Matt
--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
OK, the short of it is, use the radiator coolers, they work better than fins in the wind. The move for an outboard cooler would be outboard first,
then through the radiator cooler and you'd feed the transmission or engine oil that's at a fairly constant temp - 180 degrees or so.

Thanks,

Johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
There is no way the the trans fluid temperature cooler should be anywhere near 180 degrees leaving the radiator. You put 180 to 190 degree coolant in
the top (or one side in the case of cross flow radiators) and get much cooler coolant out the bottom (or other side). The trans cooler is always
located in the cooler side of the radiator where the coolant temperature is lower. My trans fluid temperature in the pan never exceeds 150.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
OK, it becomes clear. It looks as if p'raps only the radiator transmission fluid cooler is the move, unless you tow a lot in hilly country in the
summer, then p'raps an outboard cooler in front of the radiator cooler. And Matt, the vapor phase cooling is one thing I do understand. Given the
really poor efficiency (Electricity to RF energy) of an analog UHF transmitter, it's about the only way you can carry the generated heat away from the
thing. We were steamfitters, among other things.

Thank, guys.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
You can't just splice a cooler into just either one of the lines at the radiator. Need to tie into the line that has the trans fluid coming out of the rad. To the trans. As to cold operation. I've installed some with valves to control when I wanted to use an auxiliary cooler. I tow something all the time with our 78- 403 Royale. At times I'm up to 21,000 lbs GVW. With absolutely no extra anything done to the GMC other then the extra trans cooler. But am interested in Applied GMC's soon to come electronic fan clutch that you can even turn on as desired. And it could improve gas mileage.

Bob Dunahugh

Bob Dunahugh
 
I'd think you'd want just the opposite... do you not want the fluid going back to the transmission at a relatively stable temp, 150 - 200 degrees,
regardless of the outside temp? If it sees the radiator cooler last before returning would it not then be at that stable temperature, either cooled or
warmed by the radiator coolant as necessary?
That cooling fan system has gone through several changes in its development, the current one looks to be the best answer for our needs. As an
interest6ing aside, all the electronic clutches have a speed sensor built in, for use by the vehicle computer. Since our coaches have no computer
beyond the driver's laptop or tablet, it isn't iterated for our use, but the potential exists to run a fan tachometer if one wanted to do so. Tom
Pryor had a tach on the demo setup in Mannsfield.
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
Every aftermarket tranny coolers instructions I have ever seen has you routing the fluid downstream from the radiator. They also often cover
eliminating the rad cooler due to a leak.

I forget which one, but one had a rather lengthy writeup on the [or at least their] theory of why this was the most efficient. Short version is the
water to fluid TF was more efficient as long as the coolant was in operating range and the ext cooler is best utilized as a second stage.

In the HP world, high stall converters create a lot of heat and its common to add addl cooling. Also, on a car with marginal radiator cooling,
eliminating the rad heat exchanger and going witha larger external cooler is common.I had problems with my suercharged Monza and dropped 20F by doing
so.

However, too big a cooler mays restrict airflow to the radiator and AC condenser. I try to mount them away from those.

I suppose in very cold weather there would be such a thing as overcooling the fluid [Not a problem in FL] but as pointed out previously, the coolant
would tend to help stabilize that.

--
76 Glenbrook
 
I feel that the external cooler should be between the cooler in the radiator and the line back to the transmission. Mine has been like this for about 35 years now and it works fine.
Why would you want to cool the transmission fluid and then warm it back up in the radiator?

Emery Stora
77 Kingsley
Frederick, CO

>
> I'd think you'd want just the opposite... do you not want the fluid going back to the transmission at a relatively stable temp, 150 - 200 degrees,
> regardless of the outside temp? If it sees the radiator cooler last before returning would it not then be at that stable temperature, either cooled or
> warmed by the radiator coolant as necessary?
> That cooling fan system has gone through several changes in its development, the current one looks to be the best answer for our needs. As an
> interest6ing aside, all the electronic clutches have a speed sensor built in, for use by the vehicle computer. Since our coaches have no computer
> beyond the driver's laptop or tablet, it isn't iterated for our use, but the potential exists to run a fan tachometer if one wanted to do so. Tom
> Pryor had a tach on the demo setup in Mannsfield.
> --
> '76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "The road goes on forever, and the party never ends" --Robert Earl Keen
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Emery,

The "Chevrolet P-30 Chassis Owners' Manual" agrees with you -- put any
external cooler in the return line. Incidentally, that manual discourages
the use of such coolers, and suggests an easy way to determine whether one
is likely needed. They do included a note that it may have to be covered
during cold weather. It's worth mentioning that they suggest installing
any temperature gauge at the outlet of the converter (where the cooler line
TO the radiator exits the transmission) and that the minimum recommended
operating temperature is 150*F. 350*F there is cause to run the engine at
1200 rpm in Neutral to bring the temperature down.

That manual, which Chevrolet would, 'way back, send for free to any P-30
owner on request, is, IMHO, an excellent reference for many GMCMH topics.
Examples: Sections on Vapor Lock and corrective actions; Battery
information, including why NOT to always use the Boost Switch;
Troubleshooting for many common systems, including the Electromotor Cruise
Control some of us have installed; Detailed information on ATF, etc.; and
much more which should be studied by most of us.

At one time Billy Massey had that manual on his web site, but I couldn't
find it to provide the URL here. Billy?

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc., etc.
www.gmcwipersetc.com

> I feel that the external cooler should be between the cooler in the
> radiator and the line back to the transmission. Mine has been like this
> for about 35 years now and it works fine.
> Why would you want to cool the transmission fluid and then warm it back up
> in the radiator?
>
 
That link didn't work for me Billy

Guy Lopes
76 Birchaven "Orion"
Sacramento, CA
W6TOL

www.GMC-Guy.com

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Billy
Massey
Sent: Thursday, December 29, 2016 4:44 PM
To: gmclist
Subject: Re: [GMCnet] Cooling Efficiency

http://bdub.net/manuals/manuals/P30.zip

Emery,

The "Chevrolet P-30 Chassis Owners' Manual" agrees with you -- put any
external cooler in the return line. Incidentally, that manual discourages
the use of such coolers, and suggests an easy way to determine whether one
is likely needed. They do included a note that it may have to be covered
during cold weather. It's ... Snip ...
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Ken
The P30 manual can be found on the GMCMI.com http://gmcmi.com/ site at
http://www.gmcmi.com/wp-content/uploads/2014/05/P30-Chassis-Manual.pdf http://www.gmcmi.com/wp-content/uploads/2014/05/P30-Chassis-Manual.pdf

Emery Stora

>
> Emery,
>
> The "Chevrolet P-30 Chassis Owners' Manual" agrees with you -- put any
> external cooler in the return line. Incidentally, that manual discourages
> the use of such coolers, and suggests an easy way to determine whether one
> is likely needed. They do included a note that it may have to be covered
> during cold weather. It's worth mentioning that they suggest installing
> any temperature gauge at the outlet of the converter (where the cooler line
> TO the radiator exits the transmission) and that the minimum recommended
> operating temperature is 150*F. 350*F there is cause to run the engine at
> 1200 rpm in Neutral to bring the temperature down.
>
> That manual, which Chevrolet would, 'way back, send for free to any P-30
> owner on request, is, IMHO, an excellent reference for many GMCMH topics.
> Examples: Sections on Vapor Lock and corrective actions; Battery
> information, including why NOT to always use the Boost Switch;
> Troubleshooting for many common systems, including the Electromotor Cruise
> Control some of us have installed; Detailed information on ATF, etc.; and
> much more which should be studied by most of us.
>
> At one time Billy Massey had that manual on his web site, but I couldn't
> find it to provide the URL here. Billy?
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI & EBL,
> Manny Brakes & 1-Ton, etc., etc., etc.
> www.gmcwipersetc.com
>
>

>
>> I feel that the external cooler should be between the cooler in the
>> radiator and the line back to the transmission. Mine has been like this
>> for about 35 years now and it works fine.
>> Why would you want to cool the transmission fluid and then warm it back up
>> in the radiator?
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
OK, the brain trust - including the folks at GM Truck and Coach - say outboard cooler last. I has again learnt something valuable in the Forum. Now,
if I can just figure out why the new transmission was installed with two of the four coolers unused and the temp sender not connected, I will of
learnt even more. Sigh.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
> OK, the brain trust - including the folks at GM Truck and Coach - say outboard cooler last. I has again learnt something valuable in the Forum.
>
> Now, if I can just figure out why the new transmission was installed with two of the four coolers unused and the temp sender not connected, I will
> of learnt even more. Sigh.
>
> --johnny

Johnny,

Who installed this and in what vehicle and why are you expecting these people to be competent? (That last it a real question.)

Matt (That has witness a lot of sub-par repairs)

--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
Keep in mind with an all stock system you also have 6 gallons of fresh watter in the water heater (48 pounds appox) as heat sink ballast tank which
tends to help stabilize temperatures. This slighly mitigates the temp rise speed pulling a hill, and slighly slows the cooling of the entire system as
you decend the grade. I would think since all 4 systems are linked by their own loops ( coolant, water, engine oil, Dexron) the whole thing should
track as one system and be more stabile.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First
 
Matt - at this point I'm not sure who did the install, or under what constraints. Consequently, they'll be anonymous until 'all precincts is heard
from' to paraphrase Ring Lardiner Jr. We've seen the kind of pecking party here which can evolve from real or imagined improper work, I've no
intention of hosting one. The transmission failed after something over 6 thousand miles of proper operation. I've directions from Manny on how to
accomplish some diagnosis, I've had a miserable cold for most of a week and consequently haven't been up to doing the tests and observations. As of a
couple of days ago, I have a trolley to remove it, and ramps to put the coach up on to ease the removal. Step one is pull the pan off and see what I
find. Dipstick investigation isn't much of a help. The fluid appears normal. I can't smell with a cold, but it didn't smell burnt when the coach
came home on the hook either. In that it's synthetic, it could get surprisingly hot and still appear and smell normal.
I can't think of any failure which would produce the symptoms which won't require R&R so it's kind of moot - except that Manny asked to remove and
check the pan to see what's in it first, a simple enough task. Ferrous metal, aluminum, friction material, or a clean pan and filter would it seems
all be indicators of one or more specific problems.
Time will tell.

--johnny

--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
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