Both coolers and heaters made of steel tubes or non-ferrous metals are commonly used in industrial power systems, and also chemical or petrochemical processes. Due to systematically increasing water deficits and disadvantages pertaining to its use in cooling systems (corrosion, mineral compound deposits inside tubes), air is now used in order to cool down external expanded tube surfaces in heat exchangers. A relatively low coefficient of heat penetration from tubes into air imposes a necessity to use considerably expanded external surfaces of these tubes. This expansion can be obtained by winding tape onto tube or by shaping high external finning using cold rolling process in three or four roller system. Tubes with fins using slant rolling method show a number of advantages in comparison to tape winding process. Those advantages include:

- increased thermal efficiency resulting from integral joint between fins and tube wall,
- strong pressure of finned section to base tube guarantees minimal thermal resistance for heat flow through the surface of bimetallic joint,
- elimination of electrochemical corrosion since moist air is prevented from accessing the bimetallic joint zone,
- high degree of external surface expansion resulting from increased height of fins and small spaces between them (small fin pitch),
- high mechanical strength of fins which results from extensive cold forming.

The above mentioned features represent sufficient reasons to use rolled finned tubes widely and effectively in the design of compact and efficient air heaters. Cemal established its own design and implementation department able to support a scope of heat transfer calculations pertaining to heat exchange and custom design of heat exchangers based on finned tubing solutions.

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