JayMaechtlen
Industrial
What are the pros and cons of Aluminum ratiators versus brass radiators?
Jay Maechtlen
Jay Maechtlen
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radiators-Aluminum vs. copper 6
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turbododge
Automotive
Actually, the engine is the original size, but has lots of heat generating and airflow restricting parts added to it! The biggest restriction appears to be in getting the air out of the engine compartment without it "looping" back to front of the car. Most of the air exists directly under the fan, and if there is bit of tailwind when sitting still, the hot air is sucked right back in. In the past, if it was running hot at idle, you could easily get it to cool down by opening the hood to let more air through.
The grill inlets are pretty good as stock, no big bypasses, etc, and a big chin spoiler pushes the air in very well when moving. I do have a full fan shroud on it, and did a lot of experimenting with fan position in the shroud to maximum flow through the radiator without any backflow, which was initially a big problem. (ended with only 3/8" of the fan inside the shroud).
When I sped up the fan, yes, the waterpump also sped up. To prevent the pump from cavitating, I was able to find a pump with a smaller impeller that was designed to run at the speed I went to, while moving the same amount of water as I had with the old setup. I had guessed that I was moving plenty of water, and that proved to be true.
The copper/brass radiators were the standard soldered construction with high density fin count.
We now can idle in traffic all day in 100*F temperatures with never going over 190* coolant temperature.
The grill inlets are pretty good as stock, no big bypasses, etc, and a big chin spoiler pushes the air in very well when moving. I do have a full fan shroud on it, and did a lot of experimenting with fan position in the shroud to maximum flow through the radiator without any backflow, which was initially a big problem. (ended with only 3/8" of the fan inside the shroud).
When I sped up the fan, yes, the waterpump also sped up. To prevent the pump from cavitating, I was able to find a pump with a smaller impeller that was designed to run at the speed I went to, while moving the same amount of water as I had with the old setup. I had guessed that I was moving plenty of water, and that proved to be true.
The copper/brass radiators were the standard soldered construction with high density fin count.
We now can idle in traffic all day in 100*F temperatures with never going over 190* coolant temperature.
Hi 'turbododge',
>>Quote:The results lead me to believe that how the tubes and fins are laid out, and how dense they are, make more difference than what they are made of. The radiators that had the lesser resistance to airflow, because of less fins and/or thickness, did better at speed because they allowed more airflow through the radiator. The radiators that did best at idle, had more fins and/or thickness, that could dissipate the heat better at the low airflow rates at idle.
>>Quote:The aluminum radiators use big tubes and wider spacings of tubes and fins, so they can allow a lot of air through. If you can supply the air, they will cool extremely well. The copper brass use smaller tubes (burst strength issues) and high density finning, so they perform better at lower airflow rates, but you can't put enough air through them to get bigtime cooling.
--------
DA: The thermal performance of a radiator Heat-transfer & pressure-drop with increasing airflow is TOTALLY determined by the design of the multi-louver fins... One can design either aluminium or copper-brass to perform in very similar ways ie. performance curves.
The main issue is that very, very few radiator designers really know how to properly optimise the units.
A lot of what you get from aftermarket suppliers is really - 'suck-&-see' - leaving the testing up to the user. The large Automotive First Tier Suppliers will generally design a radiator to suit a particular performance - based on 1 or more 'performance points', or an 'index'.
Issue about 3 vs 4 row radiators:
In general, you can expect to see very little, if any, performance gain under vehicle operating conditions by adding the 4th row. The reason is that the cooling air has already almost reached its maximum temperature by the end of row 3, & there is then very little 'temp driving force' left for row 4...
------------
>>Quote:If radiator manufacturers start telling you they cool "X" amount better than the competition, be sure to ask them what they are running for airflow velocity and static pressure drop though the radiator, and at what heat dissipation rate they are operating (to simulate idle, cruise, full power etc). Most either don't know, won't tell, or don't care because the numbers they are giving are bogus.
DA: Try & obtain heat-transfer/pressure-drop performance curves against air-flow & water-flow... These will come from the manufacturer's wind-tunnel tests... If they can't produce these curves for you, be suspicious of claimed performance...
Best regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
>>Quote:The results lead me to believe that how the tubes and fins are laid out, and how dense they are, make more difference than what they are made of. The radiators that had the lesser resistance to airflow, because of less fins and/or thickness, did better at speed because they allowed more airflow through the radiator. The radiators that did best at idle, had more fins and/or thickness, that could dissipate the heat better at the low airflow rates at idle.
>>Quote:The aluminum radiators use big tubes and wider spacings of tubes and fins, so they can allow a lot of air through. If you can supply the air, they will cool extremely well. The copper brass use smaller tubes (burst strength issues) and high density finning, so they perform better at lower airflow rates, but you can't put enough air through them to get bigtime cooling.
--------
DA: The thermal performance of a radiator Heat-transfer & pressure-drop with increasing airflow is TOTALLY determined by the design of the multi-louver fins... One can design either aluminium or copper-brass to perform in very similar ways ie. performance curves.
The main issue is that very, very few radiator designers really know how to properly optimise the units.
A lot of what you get from aftermarket suppliers is really - 'suck-&-see' - leaving the testing up to the user. The large Automotive First Tier Suppliers will generally design a radiator to suit a particular performance - based on 1 or more 'performance points', or an 'index'.
Issue about 3 vs 4 row radiators:
In general, you can expect to see very little, if any, performance gain under vehicle operating conditions by adding the 4th row. The reason is that the cooling air has already almost reached its maximum temperature by the end of row 3, & there is then very little 'temp driving force' left for row 4...
------------
>>Quote:If radiator manufacturers start telling you they cool "X" amount better than the competition, be sure to ask them what they are running for airflow velocity and static pressure drop though the radiator, and at what heat dissipation rate they are operating (to simulate idle, cruise, full power etc). Most either don't know, won't tell, or don't care because the numbers they are giving are bogus.
DA: Try & obtain heat-transfer/pressure-drop performance curves against air-flow & water-flow... These will come from the manufacturer's wind-tunnel tests... If they can't produce these curves for you, be suspicious of claimed performance...
Best regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
I have no idea, although I paid £400k ($550-600K) for a Nocolock furnace for brazing aluminium rads.
I guess costs start to escalate when you look at the conveyor types of furnace and the sealing systems to hold in the nitrogen. also, the recirc fans in our furnace seemed an extortionate price when we had to buy replacements.
Another one for the sharp intake of breath is, Our furnace line cost a £1000 ($1500) the second you hit the "Go" button and needed 3 hours to heat up from it's idling temp.
Its an expensive game to get into but the rewards, if you can keep feeding the furnace, are incredible.
I guess costs start to escalate when you look at the conveyor types of furnace and the sealing systems to hold in the nitrogen. also, the recirc fans in our furnace seemed an extortionate price when we had to buy replacements.
Another one for the sharp intake of breath is, Our furnace line cost a £1000 ($1500) the second you hit the "Go" button and needed 3 hours to heat up from it's idling temp.
Its an expensive game to get into but the rewards, if you can keep feeding the furnace, are incredible.
>>TNT2bluz:
>>A question, if I may. What makes a cuprobraze furnace so special that one
>>needs to pay half a million dollars for one?
>>finman:
>>I have no idea, although I paid £400k ($550-600K) for a Nocolock furnace
>>>for brazing aluminium rads.
adTherm:
To braze either Copper-Brass (CuproBraze), or Aluminium (Nocolok), a CAB-type inert atmosphere furnace is required.
In order to maintain a low Oxygen value, & so prevent oxidation during the brazing process, very pure Nitrogen has to be 'stuffed' into the furnace at various points. The oxidation can occur both during the 'heat up phase' where the product temperature is raised from ambient, to brazing temperature, & during the 'brazing phase'.
For Aluminium (Nocolok), oxidation during the 'heat up phase' is not really a major consideration. Before the brazing temp is reached, the flux melts & prepares the surfaces for melt-alloy flow - removes material oxides & wets the material surfaces to enhance melt-alloy flow. After brazing, the flux solidifies & provides a protective layer against oxidation.
For Copper-Brass (CuproBraze), oxidation during the 'heat up phase' is a real problem. If too much oxygen is present with simultaneous application of heat, then a black oxide is formed. This leaves the fins looking dirty. Prior to reaching brazing temp, the binders in the 'paste' essentially form a 'fluxing gas' & partially shield the joint during brazing. If too much oxygen is present during the brazing process, then the powder oxidises & will not melt - it becomes inactive.
The net effect of the above-mentioned oxidation sensitivities is that Nocolok products can be brazed with an oxygen content of >50 ppm, in the brazing atmosphere, whereas CuproBraze needs to be kept closer to 20 ppm, otherwise major problems can occur.
To achieve these low oxygen values, experience has shown that CuproBraze now requires far more Nitrogen than an equivalent Nocolok furnace, for the same throughput. (We did not expect this at the beginning of the project.)
Thus, the ongoing running costs of a CuproBraze Furnace will be higher than for Nocolok - in terms of Nitrogen consumption.
-------------------
>>finman:
>>I guess costs start to escalate when you look at the conveyor types of
>>furnace and the sealing systems to hold in the nitrogen. also, the
>>recirc fans in our furnace seemed an extortionate price when we had
>>to buy replacements.
adTherm:
Cuprobraze lends itself to using simpler furnaces than Nocolok, since Nocolok temperatures have to be very accurately controlled as brazing temperature is approached. CuproBraze is less sensitive due to the larger gap between melting temp of braze powder (589-600'C) & brass melting temp (~980'C) - whereas for Nocolok the cladding melts at 577'C, & base aluminium at ~ 660'C... a much narrower 'brazing window'.
In this case, CuproBraze can use 'muffle-less furnaces' hence reducing manufacturing costs somewhat. But, most manufacturers have opted for 'Nocolok-style' furnaces, just in case they have to switch back to Nocolok Production if their Cuprobraze products are not accepted in the marketplace.
---------
adTherm:
The issue of the 'style' of furnace - Convection vs Radiation - will play more of a part in the initial costing of a furnace. The choice will depend on the types of product the fabricator chooses to manufacture.
--------
>>finman:
>>Another one for the sharp intake of breath is, Our furnace line cost
>>a £1000 ($1500) the second you hit the "Go" button and needed 3 hours
>>to heat up from it's idling temp.
>>Its an expensive game to get into but the rewards, if you can keep
>>feeding the furnace, are incredible.
adTherm:
You obviously have a large furnace to feed. A smaller, batch-type, or semi-continuous-type furnace is more flexible in terms of load-scheduling. The main cost is then to keep the furnace hot - with the part heat-up load only coming when you actually braze parts. These furnaces are designed to 'feed & braze' as required.
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
>>A question, if I may. What makes a cuprobraze furnace so special that one
>>needs to pay half a million dollars for one?
>>finman:
>>I have no idea, although I paid £400k ($550-600K) for a Nocolock furnace
>>>for brazing aluminium rads.
adTherm:
To braze either Copper-Brass (CuproBraze), or Aluminium (Nocolok), a CAB-type inert atmosphere furnace is required.
In order to maintain a low Oxygen value, & so prevent oxidation during the brazing process, very pure Nitrogen has to be 'stuffed' into the furnace at various points. The oxidation can occur both during the 'heat up phase' where the product temperature is raised from ambient, to brazing temperature, & during the 'brazing phase'.
For Aluminium (Nocolok), oxidation during the 'heat up phase' is not really a major consideration. Before the brazing temp is reached, the flux melts & prepares the surfaces for melt-alloy flow - removes material oxides & wets the material surfaces to enhance melt-alloy flow. After brazing, the flux solidifies & provides a protective layer against oxidation.
For Copper-Brass (CuproBraze), oxidation during the 'heat up phase' is a real problem. If too much oxygen is present with simultaneous application of heat, then a black oxide is formed. This leaves the fins looking dirty. Prior to reaching brazing temp, the binders in the 'paste' essentially form a 'fluxing gas' & partially shield the joint during brazing. If too much oxygen is present during the brazing process, then the powder oxidises & will not melt - it becomes inactive.
The net effect of the above-mentioned oxidation sensitivities is that Nocolok products can be brazed with an oxygen content of >50 ppm, in the brazing atmosphere, whereas CuproBraze needs to be kept closer to 20 ppm, otherwise major problems can occur.
To achieve these low oxygen values, experience has shown that CuproBraze now requires far more Nitrogen than an equivalent Nocolok furnace, for the same throughput. (We did not expect this at the beginning of the project.)
Thus, the ongoing running costs of a CuproBraze Furnace will be higher than for Nocolok - in terms of Nitrogen consumption.
-------------------
>>finman:
>>I guess costs start to escalate when you look at the conveyor types of
>>furnace and the sealing systems to hold in the nitrogen. also, the
>>recirc fans in our furnace seemed an extortionate price when we had
>>to buy replacements.
adTherm:
Cuprobraze lends itself to using simpler furnaces than Nocolok, since Nocolok temperatures have to be very accurately controlled as brazing temperature is approached. CuproBraze is less sensitive due to the larger gap between melting temp of braze powder (589-600'C) & brass melting temp (~980'C) - whereas for Nocolok the cladding melts at 577'C, & base aluminium at ~ 660'C... a much narrower 'brazing window'.
In this case, CuproBraze can use 'muffle-less furnaces' hence reducing manufacturing costs somewhat. But, most manufacturers have opted for 'Nocolok-style' furnaces, just in case they have to switch back to Nocolok Production if their Cuprobraze products are not accepted in the marketplace.
---------
adTherm:
The issue of the 'style' of furnace - Convection vs Radiation - will play more of a part in the initial costing of a furnace. The choice will depend on the types of product the fabricator chooses to manufacture.
--------
>>finman:
>>Another one for the sharp intake of breath is, Our furnace line cost
>>a £1000 ($1500) the second you hit the "Go" button and needed 3 hours
>>to heat up from it's idling temp.
>>Its an expensive game to get into but the rewards, if you can keep
>>feeding the furnace, are incredible.
adTherm:
You obviously have a large furnace to feed. A smaller, batch-type, or semi-continuous-type furnace is more flexible in terms of load-scheduling. The main cost is then to keep the furnace hot - with the part heat-up load only coming when you actually braze parts. These furnaces are designed to 'feed & braze' as required.
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
Hi Des, nice to hear from you again.
In the early days of starting our Brazing plant we could assemble for a week and braze the whole lot during 1 day! Our assemblers were not slow but the furnace, once upto operating temp was hungry.
Our Furnace included Thermal degrease, Airblast cooling section Fluxing, Pre-heat/nitrogen purge, The Furnace, Controlled quench and final airblast cooling section all in a single line. Excellent piece of kit if you had the work for it.
Load scheduling was not a major problem but we had to be mindful that we started on the heavier components first always followed by lighter and lighter components
In the early days of starting our Brazing plant we could assemble for a week and braze the whole lot during 1 day! Our assemblers were not slow but the furnace, once upto operating temp was hungry.
Our Furnace included Thermal degrease, Airblast cooling section Fluxing, Pre-heat/nitrogen purge, The Furnace, Controlled quench and final airblast cooling section all in a single line. Excellent piece of kit if you had the work for it.
Load scheduling was not a major problem but we had to be mindful that we started on the heavier components first always followed by lighter and lighter components
Hi again 'finman'... equally good to hear from you again... 
Your furnace sounds like the classic case of a system oversized for large-scale production volumes. These huge beasts cost so much money just to heat up... frightening...
Companies have been developing more flexible furnace systems eg. Seco-Warwick's 'Active Only' furnace which takes parts as they are fed in - large/small up to you... the control system takes care of the load variations...
Your work-around by loading heavy components first allowed the furnace to settle in on these large, heavy loads - incrementally backing off to smaller, lighter loads helps to maintain furnace stability...
(I have been working on a 4-zone radiation furnace simulator - with very interesting results... explains a lot of things about the system dynamics).
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
Your furnace sounds like the classic case of a system oversized for large-scale production volumes. These huge beasts cost so much money just to heat up... frightening...
Companies have been developing more flexible furnace systems eg. Seco-Warwick's 'Active Only' furnace which takes parts as they are fed in - large/small up to you... the control system takes care of the load variations...
Your work-around by loading heavy components first allowed the furnace to settle in on these large, heavy loads - incrementally backing off to smaller, lighter loads helps to maintain furnace stability...
(I have been working on a 4-zone radiation furnace simulator - with very interesting results... explains a lot of things about the system dynamics).
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
The largest Core that we brazed as a one piece unit was 1.8 x 1.4 x 0.150 metres.
Most of our work was for Off-road and Static applications all big cores.
Furnace line worked well whilst controlled by lucid types, not so well under the Production dept.
Most of our work was for Off-road and Static applications all big cores.
Furnace line worked well whilst controlled by lucid types, not so well under the Production dept.
Now THOSE are really nice, large cores...
These Furnaces are very sensitive systems (a definite feminine side exists) & have to be pampered by very smart Technologists - especially for large cores.
Once the Production Dept get hold of the Furnace, then things always start to drift... I wonder why?
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
These Furnaces are very sensitive systems (a definite feminine side exists) & have to be pampered by very smart Technologists - especially for large cores.
Once the Production Dept get hold of the Furnace, then things always start to drift... I wonder why?
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
This is very interesting. I am actually challenged to make a small brazing furnace using recycled materials ala junkyard wars. This need not be a conveyorized system, but I intend it to be used for rapid cycle batch baking.
Apart from not having the proverbial few hundred thousand clams in my pocket, I am curious whether a different brazing compound/alloy can be employed to create a similar output.
Is there any other way to "cuprobraze" cores without the need for an atmosphere controlled furnace?
Apart from not having the proverbial few hundred thousand clams in my pocket, I am curious whether a different brazing compound/alloy can be employed to create a similar output.
Is there any other way to "cuprobraze" cores without the need for an atmosphere controlled furnace?
>>TNT2bluz:
>>Is there any other way to "cuprobraze" cores without the need for an atmosphere controlled furnace?
adTherm:
Not a chance, I'm afraid... Without a modified atmosphere & low Oxygen, you will never braze... you will have a dirty, oxidised core + oxidised brazing powder. :-(
In terms of other alloys - none really can be used at temps low enough to prevent the black oxide formation I mentioned in my previous post - without atmosphere control.
You can make a small batch furnace - but it must be 'back-filled' with Nitrogen.
I performed some previous trials using an addition of Hydrogen, & hydrogen/nitrogen mixtures - good stuff... but you need the correct binder pack. Current CuproBraze Technology does not support that option - unfortunately.
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
>>Is there any other way to "cuprobraze" cores without the need for an atmosphere controlled furnace?
adTherm:
Not a chance, I'm afraid... Without a modified atmosphere & low Oxygen, you will never braze... you will have a dirty, oxidised core + oxidised brazing powder. :-(
In terms of other alloys - none really can be used at temps low enough to prevent the black oxide formation I mentioned in my previous post - without atmosphere control.
You can make a small batch furnace - but it must be 'back-filled' with Nitrogen.
I performed some previous trials using an addition of Hydrogen, & hydrogen/nitrogen mixtures - good stuff... but you need the correct binder pack. Current CuproBraze Technology does not support that option - unfortunately.
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
I know of a small company in the UK that uses "Home made" furnaces to Braze Aluminium cores, So I see no reason why you shouldn't replecate this concept, I believe their furnaces cost around £25k! although this is a rumoured figure, I've seen them and they definitely produce nice looking cores.
I'm wondering why you wouldn't wish to use CAB to braze, if you're genuinely going to build your own furnace why not go with a tried and trusted concept? that way you will have something to go on.
Mr Adtherm may be able to offer something different??????
I'm wondering why you wouldn't wish to use CAB to braze, if you're genuinely going to build your own furnace why not go with a tried and trusted concept? that way you will have something to go on.
Mr Adtherm may be able to offer something different??????
>>finman:
>>Mr Adtherm may be able to offer something different??????
adTherm:
If you only want to do a few prototypes, then there are simple 'Development Boxes' - if you are seriously looking into a small 'batch type furnace', then I would be more than happy to advise you - it is definitely possible... just email me... we can talk 'off-forum'
The trick lies in the oxygen control. Ironically, Aluminium has turned out to be less sensitive than CuproBraze in what oxidation it can tolerate - we can use a few tricks
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
>>Mr Adtherm may be able to offer something different??????
adTherm:
If you only want to do a few prototypes, then there are simple 'Development Boxes' - if you are seriously looking into a small 'batch type furnace', then I would be more than happy to advise you - it is definitely possible... just email me... we can talk 'off-forum'
The trick lies in the oxygen control. Ironically, Aluminium has turned out to be less sensitive than CuproBraze in what oxidation it can tolerate - we can use a few tricks
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
>>TNT2bluz:
>>How about having a decontamination bath post baking?
You won't be able to remove the black oxide that way - it will be ghastly. You have to see it to believe it. As a test, put your radiator through a friend's furnace without the Nitrogen turned on - you will be shocked...
In addition, your radiator WON'T be brazed... the powder oxidises & does not melt... it just falls off...
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
>>How about having a decontamination bath post baking?
You won't be able to remove the black oxide that way - it will be ghastly. You have to see it to believe it. As a test, put your radiator through a friend's furnace without the Nitrogen turned on - you will be shocked...
In addition, your radiator WON'T be brazed... the powder oxidises & does not melt... it just falls off...
Regards,
Des Aubery...
(adTherm Technology - - info@adtherm.com)
Hmm...this is indeed challenging.
I wonder why a friendlier brazing alloy wasn't made. I've been corresponding with some people who say that they may be able to develop a brazing compound that does not require fluxing nor an atmosphere controlled furnace. Lost their email when my system crashed.
You got mail adTherm.
I wonder why a friendlier brazing alloy wasn't made. I've been corresponding with some people who say that they may be able to develop a brazing compound that does not require fluxing nor an atmosphere controlled furnace. Lost their email when my system crashed.
You got mail adTherm.
Believe it or not, some companies do "Flame Brazing" of aluminium, No CAB!!!!
Messrs Adtherm & TNT2bluz, I would appreciate being kept "In the Loop" if you do not have a problem with this.
I'll drop my e-mail over to Adtherm, you never know I may be able to assist!.
Messrs Adtherm & TNT2bluz, I would appreciate being kept "In the Loop" if you do not have a problem with this.
I'll drop my e-mail over to Adtherm, you never know I may be able to assist!.
I've seen people do what we call "hand baking" using a wide dispersal torch flame over the core. They also add solder material in between. This is very cumbersome and is an additional layer of lead that I'm not too happy with.
We actually are a notch above that by converting a bakery used for making salted breakfast buns oven into a furnace.
We actually are a notch above that by converting a bakery used for making salted breakfast buns oven into a furnace.
Our workforce used to refer to our furnace line as the Pizza oven so nothing changes.
Beware that the materials used in the oven are capable of the higher temps used for brazing, (the recirc fans on our furnace where made from inconel!)
When doing trial runs at another company we used Nitrogen supplied in a road tanker that was equiped with a small regenerator, I must admit to being sceptical when I saw the set up but it all worked fine for the trial period.
Beware that the materials used in the oven are capable of the higher temps used for brazing, (the recirc fans on our furnace where made from inconel!)
When doing trial runs at another company we used Nitrogen supplied in a road tanker that was equiped with a small regenerator, I must admit to being sceptical when I saw the set up but it all worked fine for the trial period.
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