HEAT TRANSFER MODELING IN DOWN FLOWING LAMINAR FILMS WITH THE DEVELOPED WAVY STRUCTURE WITH CO-CURRENT STEAM FLOW

Abstract

The result of heat transfer modeling in down flowing viscous laminar films with the developed wavy structure at the regime of evaporation from film interface at free falling and with co-current steam flow, a heat transfer model, which takes into account a cyclic process of temperature field relaxation with the periodic mixing of film by big waves, has been presented. A mathematical heat transfer model in laminar saturate liquid film with the developed wavy structure on its surface has been developed. The model takes into consideration cyclic relaxation of transient temperature field which happens right after the passage of a powerful big wave. The developed mathematical model describes the time history of the two dimensional temperature fields as a function of the Peclet number and the core characteristic of the wavy motion (the length of big waves). Based upon the proposed model a set of correlations has been obtained. These ones are proposed as a means for the generalization of heat transfer experimental data, obtained within the experimental studies of liquid films, heated to the saturation temperatures and evaporation from the interface. A generalized equation has been derived, which can be used for the calculations of Heat Transfer Coefficients (HTC) to the saturated sugar solutions liquid films. This equation contains wavy characteristics of down flowing films and are valid within the range of parameters characteristic of sugar industry evaporators, namely: concentrations – 0…70 % dry matter; liquid mass flow rate density–0.01×10^-3…0.6×10^-3 m²/sec, the Peclet number range – 400…25000.