Results of application of the first similarity theorem to modeling of processes of electro-contact heating of liquids on the basis of experimental data

Abstract

In agricultural production, thermal treatment of liquids is widespread: heating of water for animal watering, feed preparation, sanitary and hygienic needs, and pasteurization of liquid media including milk. The most simple in terms of technical realization and energy efficient is electro-contact heating when the heating of liquid is carried out by transferring to it the thermal energy from the heat-exchange surface through which the electric current flows. Electro-contact heating allows relatively simple control of thermal process parameters and identification of rational modes which is of particular interest in the study of fast flowing and not easy to register modes in induction milk pasteurizers of high frequency. The research goal is to evaluate the possibility of using the first similarity theorem to extend the results of experimental studies to the modeling of devices and processes of electric contact heating of a different performance on the heated liquid. The methods of experimental data processing and the theory of similarity are used. The application of the first similarity theorem in determining the similarity criteria for spreading the results of experimental studies on other predicted indicators of technological process and modeling using the equations of the process under study is quite possible. The results of experimental research are as following: power P = 8000 W, transformer output voltage U = 50 V, current through the heat exchanger wall I = 160 A, mass flow rate of water G = 500 kg h, and water outlet temperature T = 31.793°C. Using the first similarity theorem, the experimental results are extended to the mass flow rate of water G = 1000 kg h, power P = 64,960 W, outlet water temperature T = 78.98°C. The first similarity theorem does not specify the ways of establishing similarity and the ways of its realization when building models. The solution of this problem is left to the developer: it is possible to change voltage, current, heat transfer area, productivity, etc.