There are two main types of condenser coils used for air cooled chillers.
What differentiates air cooled from water cooled is the condenser style.
This is for good reason though.
A lot changes in design and support equipment required between the two.
Using air cooled “air over” coils “heat exchangers” the differences between different modes is fairly minimal.
The first coil is a tube and fin.
There is a rack of copper tubes held together via endplates.
These tubes have aluminum fins slid onto them.
These are typically arranged in large slab coils running the length of the chiller.
They are the same coils used in RTU and splits but much larger.
A single circuit may have 1 to 4 slabs to meet its needs.
The second coil is a micro channel.
These are called micro channels because instead of copper tubes there are thin strips of aluminum tubing.
The tubes may be 1/8in “3mm” roughly in thickness but 1-2in “2-5cm” deep.
The thin channel in each tube will be split further by little dividers creating 1/32in “1mm” square channels through the length of the tube.
There will be many of these tubes throughout the coil with thin aluminum fins between them for surface area.
Instead of large slab coils these will typically stretch the width of the chiller in a V pattern with another coil.
These two coil V sets will repeat down the length of the chiller.
With this arrangement a circuit could have many coils dedicated to it.
Micro channels are more efficient at heat transfer than a tube/fin.
MC have been far less durable and reliable than tube/fin.
This is why the industry has not gone 100% MC.
We did learn a lesson by trying to make the copper tubes too thin for better heat transfer.
This led to a rash of unreliable tube/fin due to leaks.
One way we struck a balance was using smaller copper tubes but more of them. This helped balance thinner walls, more surface contact, and durability.
The design and build quality of MC compared to the beginning has significantly improved.
Customer confidence in the coils has also improved with time leading to manufacturers being able to design more MC based chillers again.
Keep in mind the market acceptance of a technology and its reputation has just as much to do with what gets designed and sold as it’s true benefit to the industry.
I want to include that tube/fin can be made with different materials and both types of coils could have special coatings.
This is decided based on corrosive environment factors. Being close to the ocean as an example.
MTT
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