SOME SAGE ADVICE

[GrUmPyBoDgEr]

Ed,

modern alloy radiators are, as Rohan has so accurately described, extremely efficient in doing their job.
The many hundreds of paper thin fins have even more mini fins pierced into them to provide even more cooling area presented to the airflow.
These fins are a push fit over the coolant tubes which in turn are only slightly thicker than the fins themselves.
Earlier alloy radiators did, as you mention, have the fins brazed/soldered to the tubes; a method that does provide better conductivity but the pushed on fins can be much more closely spaced & subsequently make up for that minimal loss of conductivity.
The tube ends maybe either brazed/soldered into the matrix endplates or even be pushed in & sealed with tiny O-Rings.
In order to achieve even better cooling those tubes are often ovalised so that a greater number of tubes may be fitted within a given matrix height.
Unfortunately one of these radiators is not a "radiator for life"
The extremely thin Alloy fins & tubes will succumb to corrosion & leak (irreparably)
Also the very compact fin spacing will clog with insects & rubbish much more quickly than older designs & a blow through with an airline will help occasionally.

My two penneth

Cheers
John

Seems we were hitting the Keyboards simultaneously Rohan!

[elansprint71]

Thanks Pete

I love being proved wrong as I know someone else had to do some work to look things up. I did a quick search and came up with some sites that had Delta's and theda's and a bunch of engineering terms so I flushed them and just went with my gut. That the luminum ones are lighter...

Gary

No problem Gary!

Ed- Don't forget if you paint your radiator black, there is a further set of calculations to be made:
The radiation energy per unit time from a black body is proportional to the fourth power of the absolute temperature and can be expressed with Stefan-Boltzmann Law as
q = ? T4 A (1)
where
q = heat transfer per unit time (W)
? = 5.6703 10-8 (W/m2K4) - The Stefan-Boltzmann Constant
T = absolute temperature Kelvin (K)
A = area of the emitting body (m2)

Or you could just fit what ya got.

[mikealdren]

Pete,
You need to paint copper rads to stop corrosion and, as you say, black radiates heat best and matt is better than gloss for heat transfer but it doesn't stay clean (and black) so gloss is better in practice.

Does the colour effect outweigh the insulation effect of the paint? I suspect not or aluminium radiators would be painted black rather than left unpainted.

As John says, blowing out the flies and muck probably increases the life and performance of the rad the most.

Mike

[Galwaylotus]

There are three modes of heat transfer, conduction, convection, and radiation. The unit on a car should probably be called a convector as the majority of heat is transferred by convection with the airflow through it. Conduction transfers heat from the cooling fluid through the tube walls and into the fins. There is also a radiation effect but, as previously mentioned, the effects are small in relation to the other modes. Radiant heat is what you feel when you open the bonnet with the engine hot but not running (along with a little convection from the air that has been warmed) or the warmth of the sun when you step out from the shade.

[elansprint71]

How about calling it a Heat Exchanger? I hope this thread is not becoming serious, I'll move on if it is.

[patrics]

Why not get the original recored it?s obviously worked well for you up to now and should you ever come to sell it, it would stay legal for racing at least in the UK.

Regards
Steve

[GrUmPyBoDgEr]

How about calling it a Heat Exchanger? I hope this thread is not becoming serious, I'll move on if it is.

Well you bloomin' started all the thermodynamic stuff; don't chicken out now

[elansprint71]

Why not get the original recored it?s obviously worked well for you up to now and should you ever come to sell it, it would stay legal for racing at least in the UK.

Regards
Steve

I'm not sure that a "26/R" would pass scrutineering in the UK with anything other than an homologated Heat Exchanger, i.e. made from alluminium. Which is where I came in.

[elansprint71]

How about calling it a Heat Exchanger? I hope this thread is not becoming serious, I'll move on if it is.

Well you bloomin' started all the thermodynamic stuff; don't chicken out now

It was not my fault, offisher; all that talk of brass/tin and brass radiators turned me 'ead. Honest.

[twincamman]

OHOH Pete has raised an ugly question -----who said 26R originally came with an aluminium rad????? Lotus cant --perhaps more of the legend --ed---------------------------------------- [dont leave yet Elansprint its about to get interesting]

[ardee_selby]

Pete,

From your experience, does the increased convection/heat exchange efficiency, of the aluminium "radiator", generate more hot air (that has to find it's way out from under the bonnet) or is it balanced out by the improved cooling of the engine in the first place?

Cheers - rd

[GrUmPyBoDgEr]

Pete,

From your experience, does the increased convection/heat exchange efficiency, of the aluminium "radiator", generate more hot air (that has to find it's way out from under the bonnet) or is it balanced out by the improved cooling of the engine in the first place?

Cheers - rd

The amount of heat to be dissipated by the radiator remains the same because the heat is generated by the engine.
A modern radiator will remove the heat from the coolant more effectively but the amount of heat is purely dependent on the output from the engine.
If the intention is to run the engine cooler then yes more heat will be removed by the radiator & pass through the engine room.

Cheers
John

[twincamman]

soooo there is a given amount of heat dissipated and/or transferred from the rad via the coolant to the atmosphere by a 'tin' rad as opposed to an aluminum rad we are looking at a differential number from tin to aluminium as there is a base amount of heat exchanged in normal operation ??? we may be looking for the heat transfer difference between tin and aluminum--ed [ this post hurts my head ]

[GrUmPyBoDgEr]

soooo there is a given amount of heat dissipated and/or transferred from the rad via the coolant to the atmosphere by a 'tin' rad as opposed to an aluminum rad we are looking at a differential number from tin to aluminium as there is a base amount of heat exchanged in normal operation ??? we may be looking for the heat transfer difference between tin and aluminum--ed

No Ed,

The materials used are just one lesser factor when taking into account the alternatives you are talking about. The radiator design i.e. the number, size & shape of the fins & coolant tubes are the most important factors.

[twincamman]

I can drive fast ---- -and my car is yellow== ---I like it - - please call a nurse --ed [ nurse says I have experienced gross rad overload ]