Copper Tube and Aluminium Tube In Air Conditioning System...
|At least in air conditioning systems throughout the world. Copper tube and aluminium tube come with attractive properties that manufacturers could not resist to use those, over, and over, to separate refrigerant from the atmosphere.|
This page will expand more on the brief description of air conditioner tubes.
Copper and aluminium, compared:
Let us look on the general characteristics of copper and aluminium as tubes in air conditioning applications,
|Thermal conductivity, k W/m K||401||237|
|Specific heat capacity, cp kJ/kg K||0.386||0.982|
|Radiant heat emissivity, ε||0.05||0.04|
|Young’s modulus, GPascals||130||70|
|Approximate price, USD/lb||2.00||1.08|
|Bending||Using tube bender||Using tube bender|
|Jointing||Tube expanding combined with soldering (for operating temperatures below 450 oC), tube expanding combined with brazing (for operating temperatures above 450 oC), threaded connection||Welding, threaded connection, hose clamp|
Copper tube, as opposed to aluminium tube in an air conditioner:
- copper tube is preferred than aluminium tube as its thermal conductivity is higher. Hence, temperature difference between the refrigerant and air will be low, and,
- copper’s specific heat is lower than aluminium’s specific heat. This means that copper is easier to heat up, or cool down whenever the system is switching between on and off mode. This makes copper tube more attractive than aluminium tube in air conditioning application
But there are a few more items to look into, before selecting the tube material to be used.
Those are, the hardness, rigidity, and the oxidising or corrosion resistance.
Copper tube wins in all arena specified in the previous paragraph. It is relatively difficult to oxidise, has good strength and rigidity. The higher strength means that you have to put in more force for tube bending, compared to aluminium.
Better still, copper can be repaired easily using soldering (brazing is used for higher temperature applications – not for air conditioners). Aluminium, on the other hand, is very difficult to repair as the welding process is delicate and sensitive. This is why aluminium tube failures will result in tube replacement.
Aluminium tube is widely used in car air conditioning system, as car air conditioning system is located in a secure “housing”, which is inside the hood. It is cheaper, and lighter compared to copper. The possibility of water ingress and physical contact inside hood is quite low. Hence physical damage and possibility for oxidisation is low.
Copper tube is very widely used in larger sized static air conditioner, as it is easier to maintain (from oxidisation), and stronger. Larger sized air conditioners, especially central systems will have exposed condensing units and long set of tube. Long term maintenance will be an issue if aluminium is used.
Having said that, copper tube and aluminium tube is selected and used according to space availability, and cost benefit analysis of the installation, and maintenance.
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