The aluminum foil for air conditioner is mainly divided into two types: plain aluminum foil and hydrophilic aluminium foil due to their different performance. Plain aluminum foil refers to the rolled and annealed aluminum foil without any surface treatment, and is mainly used for low-grade split air conditioner outdoor units and window-type air conditioner.
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In recent years, with the improving requirements for energy-saving, environmental protection and corrosion and bacteria resistance, the plain aluminum foil gradually can’t satisfy the need. That’s why more and more air conditioner manufacturers choose hydrophilic aluminum foil.
The surface of the hydrophilic foil has a strong hydrophilicity. The water droplets condensed on the radiator are easy to spread and flow down, avoiding affecting the ventilation effect of the radiator, so that the heat exchange efficiency is increased by 5%.
In addition, the hydrophilic coated foil is of strong corrosion resistance, great bacteria resistance and no odor, which is mainly used for high-end air conditioners. Hydrophilic aluminum foil is to do hydrophilic treatment for the aluminum foil, which is coated with an anti-corrosion coating and a hydrophilic coating and is dried in a drying furnace.
Because the surface is coated with a hydrophilic layer, the condensed water will quickly spread on the hydrophilic aluminum foil and will not condense into water beads, accelerating the cooling and heating speed and effectively avoiding the noise of air flow caused by the obstruction of the condensed water.
The main advantages of hydrophilic aluminum fin stock:
1. Excellent hydrophilicity and corrosion resistance.
2. Good formability and no abrasion to the mold.
3. Extremely strong resistance to stamping oil, solvent and heat.
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4. The air flow resistance is small, and the heat exchange rate can generally be increased by 10%-15%.
Condensation management is essential to ensuring the efficient function of heat exchangers and critical for the correct operation of evaporators.
Hydrophilic topcoats, surfaces tending not to adsorb water or be wetted by water, are effective in environments of excessive condensation, as they enable water to flow easily off the heat exchanger surface by virtue of lowered surface tension, thereby enhancing heat transfer performance in wet and frost conditions. At the same time, hydrophilic coatings protect heat exchangers from the corrosive effect of water and exhibit fine performance in providing protection in salty environments.
So far, hydrophilic topcoats were primarily available for traditional finned-pack coils. Observing growing interest in heat pumps based on microchannel heat exchangers, especially reversible models where MCHE coils are also engaged as evaporators, Kaltra proposed new coating chemistry and method of applying hydrophilic topcoats suitable for this type of coils.
A coating is considered hydrophilic in case the contact angle of a water droplet’s edge with a surface is less than 90 degrees. This refers to the angle that a droplet of water makes at the point of contact with the surface – a lower angle represents better coating performance. Field tests conducted on Kaltra’s microchannel heat exchangers treated with a hydrophilic agent have shown that a contact angle is fewer than 30 degrees with high critical surface tension.
Based on laboratory tests and validation exercises, we recommend hydrophilic treatment for coils exposed to wet and/or frost conditions, particularly evaporators, including those used in air-source heat pump applications, and for dehumidifying coils.
Laboratory experiments also have shown increased evaporation heat transfer rates of hydrophilic-treated coils, specifically at high Reynolds numbers, in the range of 25-55%.
In sum, the use of a hydrophilic polymer:
The chemical agent used for Kaltra’s hydrophilic coating has been designed by Nihon Parkerizing, a Japanese-based surface treatment industry leader.
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