Flow pattern and cleaning performance of a stationary liquid jet operating at conditions relevant for industrial tank cleaning

Cleaning of processing tanks by impinging liquid jets is common practice in the food and biotechnology sectors. However, satisfactory prediction of the cleaning performance of such jets has so far only been achieved in small scale experiments. In the present work, cleaning with a horizontal water jet was studied using a 191113 tank and settings applicable to industrial operations; nozzle internal diameters, d(N), of 2-5.5 mm, cleaning distances, L, of 80-2490 mm, and flow rates, Q, of 0.05-3.0 m(3) h(-1). Experimental data and model predictions of the behaviour of the jet when striking an unsoiled surface showed reasonable agreement for a nozzle with d(N) = 2 mm at small cleaning distances (L 80 and 200 mm). At greater dN and cleaning distances there was poorer agreement, which was attributed to jet break-up and splatter. Similar observations were made when cleaning a surface soiled with white petroleum jelly. The evolution of the cleaned area was predicted reasonably well for experiments with d(N) = 2 mm, L =80 mm, and soil layer thicknesses of 0.25-1.49 mm. For longer cleaning distances and larger d(N) only the initial stages of cleaning could be modelled, because jet break-up introduced complexities and momentum losses not accounted for in the mathematical models. The effects of jet break-up can partly be accommodated, in practice, by correcting the jet flow rate for these momentum losses. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.