Evaluation of Vipertex Enhanced Heat Transfer Tubes under Fouling Conditions

摘要

Heat transfer enhancement is important in the development of high performance thermalrnsystems. Fouling of a surface occurs when settlement or growth of unwanted materialrncontaminates the surface to the point that the surface can no longer be used. Depositsrnare the result of a series of complex reactions that cause deposits to form on the surface.rnEconomic and technical problems associated with fouling in process systems are knownrnand documented. Parameters that influence fouling include: surface geometry, surfacerntemperature, surface material/finish, fluid dynamics, flow velocity and fluid properties.rnFor many conditions, fouling can be reduced but not necessarily eliminated.rnVipertex? enhanced surfaces are flow optimized process surfaces that increase heatrntransfer through a combination of factors that include: increasing fluid turbulence,rnsecondary flow development, disruption of the thermal boundary layer and increasingrnthe heat transfer surface area. In addition to heat transfer enhancement, the fouling raternof Vipertubes? was much less than the rate of smooth tubes; additionally the totalrnamount of fouling over a given time period was also less. This reduction in the rate ofrnfouling is the result of secondary flow patterns that forms as a result of the patentedrnVipertex surface design. These secondary flows circulate near the tube surface andrnclean it, preventing the buildup of materials.rnSeveral Vipertubes were studied here, with flow rate and temperature data beingrnmonitored for the duration of the study. The tubes are exposed to untreated lake waterrnfor various time periods. Transient observations and heat transfer measurements of thernsurfaces were obtained. Fouling results presented include instantaneous and totalrnfouling amounts.rnThese observations support the conclusion that when compared to smooth tubes,rnVipertubes provide superior thermal performance, providing heat transfer increases ofrnmore than 100 %. At the same time the surface of the Vipertubes also minimize therndetrimental effects of fouling thus providing additional service time for Vipertexrndesigns. Vipertex surfaces enhance heat transfer, minimize operating costs and recoverrnmore energy. These enhanced surfaces provide an opportunity to advance the design ofrnmany heat transfer products.