The article is a research work in the field of processes and apparatuses of biotechnological productions, aimed at a comprehensive study of the processes of transfer of momentum, thermal energy and mass in nutrient media of yeast and brewing industries. The ultimatum of research is to establish the relationship between the transfer coefficients in the relevant physical processes, namely, the coefficients of kinematic viscosity, thermal diffusivity, and molecular diffusion. The rationale for the need to conduct complex experimental studies of one of the most important dynamic characteristics of matter – the density distribution of the matter mass in its volume – is presented. The objects of research were aqueous solutions of beet molasses and beer wort concentrate, mass concentration of soluble solids (DM) being 77.7 and 81% DM respectively. Six aqueous solutions of beet molasses were made with the concentration of DM of 16.2, 32.5, 40.2, 51.9, 60.2, and 69.9% DM. For seven aqueous solutions of beer wort concentrate used in the experiment the concentration of DM was 10.2, 20.6, 30.1, 40.3, 50.1, 59.6, and 72.4% DM. The range of temperature variation was 293K–363K for aqueous solutions of molasses and 283K–353K for aqueous solutions of beer wort concentrate. Measurements of the density of all research objects were carried out using an Excellence D4 Mettler Toledo density meter, the concentration of soluble solids in aqueous solutions was measured using a PTR46 refractometer manufactured by Index Instruments Ltd. As a result of the studies carried out, graphical and mathematical dependences of the density of all studied objects on the SW concentration and temperature were obtained. Comparison of the numerical values for the density of molasses aqueous solutions and beer wort concentrate, with comparable values of the content of solids in them and temperatures, showed a complete match. This made it possible to identify aqueous solutions of molasses and beer wort concentrate, despite the fact that both of these products are produced from different feed stocks: molasses is a waste product of sugar production, and beer wort is a semi-finished product in the process of obtaining beer products from grain raw materials. The only original parameter differentiating one type of analysis from another is mass concentration of soluble solids. As the parameter corresponds to technological properties more than physical ones, we had to determine the values of density over a wide range of solids’ concentrations and temperatures, which are widely used both for hydraulic and for thermal calculations.
The article is a continuation of the research in the field of comprehensive study of the properties characterizing the processes of momentum, thermal energy, and mass transfer in liquid nutrient media of biotechnological production. Experimental studies of the rheological properties for liquid nutrient media have been conducted. Beet molasses with an initial concentration of dry substances (DS) of 77.7 wt.% and concentrated malt extract of beer wort with an initial concentration of DS 81 wt.% were selected as objects of research. The temperature variation range was 10 to 70℃. The viscosity of the mentioned objects was measured with a HÖPPLER® KF 3.2 ball viscometer and also for highly viscous solutions on a Rheotest RN 4.1 viscometer, as a result of which the graphical dependences on temperature and DS concentration, as well as the gradient of shear rate were obtained. It has been established that the viscosity of these two nutrient media (beet molasses and beer wort), different in the method of obtaining the composition, has not only a similar pattern of change in the dynamic viscosity coefficient depending on temperature and content of soluble solids, but also a comparable numerical range of values. The boundaries of variation for the shear rate gradient, in which the studied objects behave as non-Newtonian fluids, from 1 to 100s-1, have been determined. The results obtained are of interest both from the point of view of fundamental science about the development of the theory of the liquid state of matter and applied, in terms of engineering calculations and the design of biotechnological equipment.
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