Effect of the axial scraping velocity on enhanced heat exchangers

• The flow pattern has been obtained by means of PIV in an enhanced heat exchanger.
• The effects of the Reynolds number and the scraping velocity have been analysed.
• The turbulence level of the flow has been related to the scraping velocity.
• A numerical RNG k–ε turbulent model has been validated with the experimental data.

The flow pattern within an enhanced tubular heat exchanger equipped with a reciprocating scraping device is experimentally analysed. The insert device, specially designed to avoid fouling and to enhance heat transfer, has also been used to produce ice slurry. It consists of several circular perforated scraping discs mounted on a coaxial shaft. The whole is moved alternatively along the axial direction by a hydraulic cylinder.The phase-averaged velocity fields of the turbulent flow have been obtained with PIV technique for both scraping semi-cycles. Special attention has been paid to the effect of the non-dimensional scraping velocity and the Reynolds number in the flow field. CFD simulations provide support for the identification of the flow patterns and the parameter assessment extension.The results show how the scraping parameters affect the turbulence level produced in the flow and therefore the desired heat transfer enhancement.