Thicker versus thinner radiator core
Thicker versus thinner radiator core
(OP)
The issue is the radiator in an antique automobile (1936 Cord). The size of the core is restricted by the grille shape, and air inflow is restricted by the hood shape. The original engineers opted for a 4" thick core to try to provide sufficient cooling capacity.
The car runs fine in 90% of use. Long hills or very slow traffic on hot days test its limits. A query by a member of our club to Harrison Radiator (GM) in the 1950s brought the response that the 4" core was needed to provide cooling at high speeds, but that its thickness reduced air flow thru it at lower speeds. They said that a 3" core would solve the cooling problem at low and medium speeds, but might be marginal at high speeds (over 70 mph).
Does this agree with current thought? Thanks. (And while we still drive our cars at highway speeds, we rarely exceed 70
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The car runs fine in 90% of use. Long hills or very slow traffic on hot days test its limits. A query by a member of our club to Harrison Radiator (GM) in the 1950s brought the response that the 4" core was needed to provide cooling at high speeds, but that its thickness reduced air flow thru it at lower speeds. They said that a 3" core would solve the cooling problem at low and medium speeds, but might be marginal at high speeds (over 70 mph).
Does this agree with current thought? Thanks. (And while we still drive our cars at highway speeds, we rarely exceed 70





RE: Thicker versus thinner radiator core
With the radiator up to par, (and the scale and rust flushed out of the rest of the cooling system as well), the problem *should* be solved. If it isn't, installing an electric fan to aid in the airflow at lower speeds would be a simple fix. My boss has a Lincoln Zephyr with a flathead V-12 that had the same problems you're experiencing. After a thorough cleaning of the radiator, fabrication of a tight-fitting shroud to pull all of the fan air through the core, etc. etc., the car still would run a little warm in stop and go traffic.
An auxiliary fan was mounted, (out of sight in front of the radiator), and wired to a thermostatically controlled switch and relay. Works like a charm, the only caveats being that the car is no longer "original".....and also that the additional electrical load from the fan meant that the charging system had to be upgraded as well. (Newer vehicles have 100 amp and up alternators for a reason!)
At lower speeds the fan really helps. It pushes a lot of air through the radiator, and expels a lot of the heat that's normally just trapped under the hood.
RE: Thicker versus thinner radiator core
RE: Thicker versus thinner radiator core
It can rot older type seals and hoses if used in to high a concentration, so care should be taken to ensure the correct rubber is used for these parts. With this, the originality of the car can be maintained.
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RE: Thicker versus thinner radiator core
Ethylene glycol tends to break down into noxious subproducts in hot environments, particularly if you get it to boil.
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RE: Thicker versus thinner radiator core
My question still, if anyone can answer, relates to the core thickness. 4" is pretty thick, and the Harrison engineers back in the '50s thought that this was done to keep the car cool at high speeds, but actually impeded cooling --- due to difficulty in getting air thru it --- at low speeds. They said a 3" core might do just the opposite. Any of you kind folks have thoughts on that?
Original radiator, incidentally, was by Jamestown. It's not quite cellular, but definitely not fin-and-tube.
RE: Thicker versus thinner radiator core
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RE: Thicker versus thinner radiator core
Thanks again, all.
RE: Thicker versus thinner radiator core
RE: Thicker versus thinner radiator core
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RE: Thicker versus thinner radiator core
My take is that you'd have to gain a lot of airflow to offset giving up 1/4 of the surface area.
There are two ways to find out: A custom thinner 'old school' radiator that is not authentic and may be of no use whatsoever, or CFD analysis. Both will cost you money that is better spent on beer.
Me, I'd save the authentic parts for the next owner, and use a modern core and auxiliary fans.
Mike Halloran
Pembroke Pines, FL, USA
RE: Thicker versus thinner radiator core
Regardless of airflow, any part of the core that is not doing its job transferring heat, will act as a bypass for coolant. More is not always better.
RE: Thicker versus thinner radiator core
RE: Thicker versus thinner radiator core
Mike Halloran
Pembroke Pines, FL, USA
RE: Thicker versus thinner radiator core
RE: Thicker versus thinner radiator core
The radiator would work more effectively if the header tank could be divided so that the water passed through the back half, then the front half in a double pass or even a triple pass if you want the entry and exit at top and bottom respectively.
A more efficient core and a more efficient fan are the best ideas to date. Poor low speed cooling is most easily solved with a bigger engine driven fan.
If it is engine driven in the original style but with more or bigger blades or turned at higher speed, or the blades have more pitch, it might even pass unnoticed, especially with the higher speed or bigger pitch method
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RE: Thicker versus thinner radiator core
For one thing, my experience with a small number of radiators suggests that the rate at which the crud plates out on the tubes is temperature dependent, so the rear (I think) rows clog first.
Mike Halloran
Pembroke Pines, FL, USA
RE: Thicker versus thinner radiator core
And Pat, the Cord has two inlet pipes to the top of the radiator (from the two sides of the V-8) but just one large outlet (to the input of the water pump) from the bottom tank. The owner of my Cord 50 years ago thought that the water was being pulled to the outlet side, so he split the top tank (side to side) with a divider inside. Don't know if that did any good. It has long since been converted back to stock, and there are no records.
You're talking about forcing the water to go down the back tubes, then up the middle tubes, then down the front tubes. I read once that much of the benefit of multi-pass configurations related to the increased turbulence. Any thoughts on that?
And thanks, guys, for putting up with this thread this long. You are all being very helpful.
Your discussion
RE: Thicker versus thinner radiator core
Yes, but that's only part of the problem. That one third of the radiator that's not accomplishing anything is letting one third of the coolant bypass the cooling process. A 4" core could virtually let half of the hot coolant circulate from the engine right back into the engine.
RE: Thicker versus thinner radiator core
Radiators are cross-flow devices & it can be shown that under many flow conditions the air exit temperatures & water temperatures coincide - after which no further cooling will occur in that section of the radiator (physics under a temperature-cross condition).
Typically, unless you have a very healthy fan pushing the air through a radiator, anything over 3 rows is a waste of metal - better to re-design the entire radiator a little more efficiently.
Why do you think Japanese radiators are only 16mm thick? :)
Des Aubery...
(adTherm Technology)
RE: Thicker versus thinner radiator core
Since I'm told that turbulence in the tubes is important to optimum heat transfer, what do you folks think of dimpled radiator tubes to increase turbulence?
Thanks again.
RE: Thicker versus thinner radiator core
RE: Thicker versus thinner radiator core
Since I'm told that turbulence in the tubes is important to optimum heat transfer, what do you folks think of dimpled radiator tubes to increase turbulence?
desA replies:
For a US/Euro radiator (horizontal tubes), the fluid velocity in the tubes is generally designed to have turbulent flow.
The Japanese split the fluid flow over many more tubes (vertical tubes). They also use fairly small water pumps. This means that the water flow velocity inside each tube is low-enough to end up with laminar flow conditions within the tubes. Dimpled tubes are then often used (or turbulators) to mechanically mix the internal fluid & push up the effective heat transfer.
Using dimpled tubes in typical US/Euro design will - already turbulent, in general, not provide much advantage - if any.
In most radiators, the airside heat-transfer coefficient dominates heat transfer (80%) & so any change to the water-side only contributes a very small advantage, if any.
Des Aubery...
(adTherm Technology)
RE: Thicker versus thinner radiator core
"In most radiators, the airside heat-transfer coefficient dominates heat transfer (80%) & so any change to the water-side only contributes a very small advantage, if any."
I'll work on the airflow issues, and thank you for the input. (Are louvered fins useful?)
But in addition. . . my car is a 70-year old American one with vertcal tubes. Might it not suffer from laminar flow which could be helped by dimpled tubes?
Thanks.
RE: Thicker versus thinner radiator core
Reynolds number: Re = density*velocity*Dh/viscosity
where: Dh = 4*Ac/P = hydraulic diameter
Ac = tube cross-sectional area
P = tube wetted perimeter
If Re < 2350, then you have laminar flow.
If you do have a laminar flow situation, then dimpled tubes could very likely be of use. Give the calculations a whirl & feed back on what Reynolds number you find. Use the lower accepted water flowrate of 40 l/min as a benchmark.
Des Aubery...
(adTherm Technology)