An investigation into some physical aspects of the wort boiling process, relating to the circulation of wort through an internal boiler, which affects the temperature distribution in the wort copper and the evenness of heating of the whole batch of wort, is described. A transparent model of a section of a wort copper, containing an aerated glycerol solution which was circulated by a magnetic pump through an overhead pipe circuit designed to imitate the way the boiling wort gushes out at the top of the tubular boiler and is deflected back onto the surface of the main body of wort, was constructed and the effects of changes in the angle at which the returned jet hit the surface (corresponding to the use in real wort coppers of different shapes and sizes of "spreaders" to deflect the wort back downwards) on the flow patterns (monitored by video camera using fluorescent tracer particles suspended in the medium) and the mixing behaviour (quantified by measuring the time taken for sodium thiosulphate added to the solution to remove the colour produced by the presence of starch and iodine in the solution, as the complete loss of colour showed that the added reagent was homogeneously distributed through the vessel) were observed. The results are illustrated by photographs and drawings, showing that the angle of impact and the position of the impact zone (relative to the dimension of the model which corresponds to the radius of an actual wort copper) do indeed have significant effects on patterns of flow and mixing. The best results were achieved using an angle which caused the returning jet to land about midway between the points corresponding to the centre and the wall of the copper.
Keywords : flow model simulation physics wort boiling