DLC-type heat exchanger tubes mitigating fouling

The use of DLC-type coatings for mitigating fouling in shell and tube heat exchangers has substantial potential as DLC is highly resistant to abrasion and known for easy cleaning and minimum fouling. The use in this field was hindered by the lack of effective production procedures. Research at University of Applied Sciences Upper Austria, Wels, Austria (FH OOE) focuses on industrial application of DLC with heat exchangers, using PACVD-reactor technology of RUBIG Group, Austria.
There are two production routes in question: G-route gap-coating for long tu bes and C-route cavity coating for shorter single-tube pieces. The G-route gap-coating process for long tubes has an inner coating applied via a slit of approximately 2 mm. As the coating is fine and evenly distributed, so-called engineered DLC-type surfaces can be produced. The challenge concerns the longitudinal welding of the slit using low-heat technology, such as a laser, in compliance with the required form tolerances.
The alternative C-route cavity coating process for shorter, single-tube pieces that use orbital welding to obtain lengths at industrial scales was also investigated. This raute provides straight tubes that are ready to be used for industrial trials. The resulting product can fully replace standard tu bes in many challenging applications, providing more than a 97% coated and easy-cleaning surface with resulting heat transfer benefits.