Study of the Influence of Sugar Solution Concentration on the Intensity of Heat Exchange, Using the Regular Heat Mode Method
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Abstract
In power industry branch of national economy , forecasting of the heat exchange intensity is of great importance, since it enables to calculate and select equipment, especially when information on the thermophysical properties of liquid media is partially unknown.
The work examines the system "environment (water in an annular volume) — thin cylindrical metal wall — investigated liquid medium (sugar solution)". Heat exchange during heating and cooling of a sugar solution with a mass concentration of dry substances of 20 % and 70 % under conditions of forced convection is studied.
It was established that in the studied liquid medium (sugar solution) signs of a regular thermal mode occur (RTM), namely: the rate of cooling (heating) of the sugar solution m = const; coefficient of heat transfer from the medium (water) to the thin-walled metal cylinder α1 ≈ const; coefficient of uneven temperature distribution is const.
In the literature, the existence of a regular thermal mode is known only for the solid bodies and systems of solid bodies. In the previous works of the authors, signs of a regular thermal mode in the "liquid-solid" system were investigated.
The calculation-experimental method is used to determine the heat transfer coefficient between the internal thin-walled vessel and the medium under the study. For the prediction of the heat exchange, the regular thermal mode method was applied .
The research is carried out on an experimental stand, which is a component of the experimental-calculation method under conditions of forced convection. The ratio of the diameters of the stirrer and the inner vessel d/D = 0.6. The range of adjustment of the frequency of revolutions of the stirrer is 26...150 rpm. Measurement of temperatures in the working volumes during the experimental study is carried out using vertically installed thermocouples in ten points.
Using signs of the existence of a regular thermal mode , the analysis of the influence of sugar solution concentration on the intensity of heat exchange is carried out.
