For humid weather which type of coils are preferred copper/copper or copper/aluminum ? and why ? is there any reference ?

Hi sharif,

We had some problems with coils in many petrochemical plants located in Persian/Arab Gulf with high humidity. Please note that there are three different matters in such cases;

1- Humidity: If the environment is only humid, the main problem is galvanic action between Cu&Al. Then you can chose Cu-Cu or Al-Al. Which one is better? it is an engineering trade-off. (Al is lighter with lower conductivity and more difficult maintenance.)

2- Corrosivity due to Cl- or I+ ions syntheses from sea water: In this case you must definitely use Cu, because of much more resistance against mentioned ions.  

3- Corrosivity due to other corrosive particles exhausted from plants to air: In this case you must be aware about type of particles. Sulfide components for example are seriously corrosive for Cu. Then you may prefer to select Al whit corrosion resistance coating.

Unfortunately, I have no specific reference to introduce except my experience. But you can find supportive evidences through technical papers, books or internet :)

Regards

Babak

Of course Copper Copper is better since this is one material so no problem of joining two material and no chance of Galvanic corrosion more over copper is more durable than aluminum and easy to clean and maintain.

humidity affects both copper as well as Aluminium coil. copper have good heat transfer characteristics. it will be better to use copper coils in terms of Efficiency. The problem of corrosion can be minimized by adopting chemical dehumidification

Copper/copper type of coils is the best  than copper/aluminumforseveralreason.

Today, condenser coils are made from copper and copper alloys These heat exchangers are used in air conditioning and refrigeration systems, industrial and central heating and cooling systems, radiators , hot water tank, and under-floor heating systems.

1-Thermal conductivity

Copper has a thermal conductivity of231 Btu/(hr-ft-F). This is higher than all other metals except silver, a precious metal. Copper has a60% better thermal conductivity rating than aluminum and a3,000% better rating than stainless steel

The only material that has similar corrosion resistance to copper is stainless steel. However, the thermal conductivity of stainless steel is1/30th that of copper. Aluminum tubes are not suitable for potable or untreated water applications because it corrodes at pH<7.0 and releases hydrogen gas. 

2-Biofouling resistance  

Copper and copper-nickel alloys have a high natural resistance to biofouling relative to alternative materials. Other metals used in heat exchangers, such as steel, titanium and aluminum, foul readily. Protection against biofouling, particularly in marine structures, can be accomplished over long periods of time with copper metals.

Copper-based heat exchangers can be manufactured with copper tube/aluminum fin, cupro-nickel, or all-copper constructions. Various coatings can be applied to enhance corrosion resistance of the tubes and fins 

3- Antimicrobial properties       

Due to copper’s strong antimicrobial properties copper fins can inhibit bacterial, fungal and viral growths that commonly build up in air conditioning systems. Hence, the surfaces of copper-based heat exchangers are cleaner for longer periods of time than heat exchangers made from other metals.

References

1. 1. ^ Jump up to: a b Antimicrobial properties of copper; http://en.wikipedia.org/wiki/Antimicrobial_properties_of_copper

   2. Jump up ^ Copper alloys in aquaculture: Antifouling properties of copper alloys; http://en.wikipedia.org/wiki/Copper_alloys_in_aquaculture#Corrosion_behavior_of_copper_alloys

   3. Jump up ^ Brass: Germicidal and antimicrobial applications; http://en.wikipedia.org/wiki/Brass#Germicidal_and_antimicrobial_applications

   4. Jump up ^ Antimicrobial copper-alloy touch surfaces; http://en.wikipedia.org/wiki/Antimicrobial_copper_alloy_touch_surfaces

   5. Jump up ^ Schoolscience.co.uk; Resources and news for science education; supported by Research Councils UK; http://resources.schoolscience.co.uk/cda/14-16/chemistry/copch0pg4.html

   6. ^ Jump up to: a b Gaffoglio, Carl J., Copper alloy surface condenser tube application and service considerations; CDA Heat Exchange Seminars; Copper Development Association

       

ghulam mustafa   whatsoever metal is used  it shold be a PMIs  regular sop to use the  hot air  with regular intervals 

Copper is best metal for the humid condition,Copper has many desirable properties for thermally efficient and durable heat exchangers. First and foremost, copper is an excellent conductor of heat. This means that copper's high thermal conductivity allows heat to pass through it quickly. Other desirable properties of copper in heat exchangers include its corrosion resistance, biofoulingresistance, maximum allowable stress and internal pressure, creep rupture strength, fatigue strength, hardness,thermal expansion, specific heat, antimicrobial properties, tensile strength, yield strength, high melting point,alloyability, ease of fabrication, and ease of joining.  For corroision  you shall use black epoxy coating in the evaporator and condensor fins for the corrisons.

as long as you don't mix the two its good ,copper is better in case of conductivity 

As per my knowledge,

Copper/Aluminum type of coil is better than Copper/Copper,

Copper / Aluminum coil mean Coil will be copper material and fins material will be aluminum,

Maximum i have seen copper / aluminum coil,

And humid weather is not more than2 month as per my experience,

If some project near the sea you can install dehumidifier,,,

At one project in hospital we install the dehumidifier in AHU's....