The crisis of heat transfer of the first kind with milk evaporation: the problem and solutions

The problem of research and elimination of the crisis of heat exchange of the first kind for multicomponent heterogeneous food mixtures by the example of milk has been considered. The aim of this work is to create rational regimes of evaporating milk without the possibility of the crisis of heat exchange of the first kind. The experiments have been planned according to the method of combinational squares. The missing thermophysical characteristics (TPC) of the food mixture studied have been determined by the dynamic C-calorimeter method. The study of this type of the heat exchange crisis has been carried out in two stages using the modeling of evaporation process with observance of geometric, hydraulic and thermal similarity. Statistical processing of the results of experiments for determining the thermophysical characteristics of milk using the nonlinear regression method has been carried out using DataFit v 9.1.32; the results of determining the first critical heat flux density have been processed in two stages: in the first stage - using StatGraphics Plus 5.0.1, the second - DataFit v 9.1.32. The result of the work performed has been presented in the form of the mathematical models of basic milk TPCs and the empirical coefficient A for the equation of the first critical heat flux density of multicomponent heterogeneous food mixtures; as well as the range of heating density of the steam generating pipe, which causes the crisis of heat exchange of the first kind, recommendations for its elimination and maintenance of rational industrial regimes of milk evaporation. The adequacy of the mathematical models obtained has been determined by Fisher's criterion and the coefficient of determination. The limits of the application of the dependence on the determination of the first critical density of the heat flux for inhomogeneous multicomponent mixtures under conditions of natural convection at atmospheric pressure have been extended, it allows to take the next step towards creating a universal equation for its determination and forecasting the occurrence of a crisis.