s_firestone
Well-known member
This is just a quick informational post about finned cooling products for reference. Particularly what not to buy. I'm basing this on a condenser I just bought that I'm not happy with the construction of. I intend to single out why, and how it should have been done.
Aluminum is used in a lot of cooling products, it is strong(but soft), light, conducts heat well above average, and radiates heat well in air. It requires some special treatment when welding.
Copper is also used in cooling products, it is not quite as strong, much heavier, conducts heat extremely well, but radiates slightly less in air than aluminum. It is easy to weld to.
It is not uncommon for cooling products to use both aluminum and copper. Particularly with water, oil, condensing and evaporator units. Or any application with extreme psi requirements. Some of this has to do with cost. Copper is not cheap. Copper is always considered the superior heat conducting metal. It is noteworthy to mention that electrical conductivity and thermal conductivity are inter-related.
I bought a condenser, typical Ebay item. Upon arrival it looked good inside the packaging. Upon closer inspection it differs from our flat tune based sequential flow unit. The tubing is circular, dual parallel tube made of copper. This in and of itself is good. The fins are aluminum.
Here is the problem and something you should watch out for.
In the particular condenser I bought. The fins are not welded to the copper but rather pressed. This lowers the efficiency due to the boundary layer of metals acting as n insulator. It's tough to get a perfect thermal junction using any dry metal surface no matter how perfect he mating surface is.
Manufacturers have known this for years. Whenever finned coolers of any type are used, the preferable method is for the fins to be brazed to the tubes. This is usually performed in a vacuum furnace. The fins essentially get soldered to the tubes. Not only does this eliminate the inefficient metal to metal boundary but also seals from corrosion and the increases the strength because the fins are affixed.
In this case it was not until I examined closely that I noticed.
What we essentially have is, a more efficient double row tubing design for a condenser(Preferable for newer refrigerants such as R-134A), but a less efficient (and notably cheaper) heat transfer method, due to pressed fins.
This was partially hidden by paint. In the end, the cooling efficiency may well even out. But the probability is high that the cooling efficiency will drop over time because the thin aluminum will expand and contract at a rate different than the copper tubing it surrounds.
So when looking for cooling products. Look for "vacuum brazed" fins. You may also transfer these principles over to intercoolers, oil coolers, radiators, transmission coolers, etc.
Usually when a particular metal is selected, it is done so based upon trade-offs. Cost vs. Performance. Operating tolerances. Reaction in particular environments. Most of the time a part is either going to cost a fair amount, or shortcuts will be taken. In the end it is you that pays the price for either.
Most companies can be measured by their products. But the internet, parts brokering, parts sourcing, etc. has complicated and made this problem worse. Good companies end up selling bad parts and bad companies end up selling good parts. The questionable companies are insulated from this because you are buying the parts from the 3rd or 4th source in the chain.
For reference, copper tubing with copper fins, will out-cool aluminum tubing with aluminum fins by attrition. Copper has a much higher thermal transfer density. It can spread more heat faster across a given surface area. Cooling is all about surface area. The more surface area, the more cooling potential. This can be stated in watts, calories, or BTU.
I would even go as far as saying its entirely possible that a copper intercooler would out-cool an aluminum one. Or possibly a hybrid copper bar between aluminum fins. It would spread the heat farther across the cooler.
Past that point heat-pipes with fins would be way more efficient than that with far less internal surface area and pressure drop.
Aluminum is used in a lot of cooling products, it is strong(but soft), light, conducts heat well above average, and radiates heat well in air. It requires some special treatment when welding.
Copper is also used in cooling products, it is not quite as strong, much heavier, conducts heat extremely well, but radiates slightly less in air than aluminum. It is easy to weld to.
It is not uncommon for cooling products to use both aluminum and copper. Particularly with water, oil, condensing and evaporator units. Or any application with extreme psi requirements. Some of this has to do with cost. Copper is not cheap. Copper is always considered the superior heat conducting metal. It is noteworthy to mention that electrical conductivity and thermal conductivity are inter-related.
I bought a condenser, typical Ebay item. Upon arrival it looked good inside the packaging. Upon closer inspection it differs from our flat tune based sequential flow unit. The tubing is circular, dual parallel tube made of copper. This in and of itself is good. The fins are aluminum.
Here is the problem and something you should watch out for.
In the particular condenser I bought. The fins are not welded to the copper but rather pressed. This lowers the efficiency due to the boundary layer of metals acting as n insulator. It's tough to get a perfect thermal junction using any dry metal surface no matter how perfect he mating surface is.
Manufacturers have known this for years. Whenever finned coolers of any type are used, the preferable method is for the fins to be brazed to the tubes. This is usually performed in a vacuum furnace. The fins essentially get soldered to the tubes. Not only does this eliminate the inefficient metal to metal boundary but also seals from corrosion and the increases the strength because the fins are affixed.
In this case it was not until I examined closely that I noticed.
What we essentially have is, a more efficient double row tubing design for a condenser(Preferable for newer refrigerants such as R-134A), but a less efficient (and notably cheaper) heat transfer method, due to pressed fins.
This was partially hidden by paint. In the end, the cooling efficiency may well even out. But the probability is high that the cooling efficiency will drop over time because the thin aluminum will expand and contract at a rate different than the copper tubing it surrounds.
So when looking for cooling products. Look for "vacuum brazed" fins. You may also transfer these principles over to intercoolers, oil coolers, radiators, transmission coolers, etc.
Usually when a particular metal is selected, it is done so based upon trade-offs. Cost vs. Performance. Operating tolerances. Reaction in particular environments. Most of the time a part is either going to cost a fair amount, or shortcuts will be taken. In the end it is you that pays the price for either.
Most companies can be measured by their products. But the internet, parts brokering, parts sourcing, etc. has complicated and made this problem worse. Good companies end up selling bad parts and bad companies end up selling good parts. The questionable companies are insulated from this because you are buying the parts from the 3rd or 4th source in the chain.
For reference, copper tubing with copper fins, will out-cool aluminum tubing with aluminum fins by attrition. Copper has a much higher thermal transfer density. It can spread more heat faster across a given surface area. Cooling is all about surface area. The more surface area, the more cooling potential. This can be stated in watts, calories, or BTU.
I would even go as far as saying its entirely possible that a copper intercooler would out-cool an aluminum one. Or possibly a hybrid copper bar between aluminum fins. It would spread the heat farther across the cooler.
Past that point heat-pipes with fins would be way more efficient than that with far less internal surface area and pressure drop.
