Experimental studies of boiling heat transfer of food solutions
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Дата
2017
Назва журналу
Номер ISSN
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Видавець
Анотація
Vacuum evaporation is widely used in the food technologies. The equipment for this process is
well known and methods of calculation and design of vacuum evaporators are described in literature as well. However, in some cases the accuracy of existing methods is not enough. The problem of designing the new, more efficient apparatuses that work in regimes, which are not usual, needs to clarify some dependencies. It concerns the problem of boiling heat transfer coefficient determination for such solutes as food products because of the high or sometimes extremely high viscosity of many food staffs is. To take into account properties of products many authors use the Prandtl number. However, determination of these properties exact values is not always possible especially it concerns the viscosity of Non-Newtonian fluids, which are the most of food staff. For experimental verification of heat transfer coefficient values, an apple juice was chosen. At first, the theoretical
value was obtained with Tolubinskiy dependency using. The vapor bulbs grows rate and surface tension coefficient were solved as for water. The dependencies between the heat transfer coefficient and heat flux for apple juice with concentration from 15 to 50 Brix were obtained as result. There are several different equations to calculate the properties of apple juice depending on temperature and concentration and several resulting dependencies that differ from each other were obtained. The comparison with the experimental data that was obtained by authors made possible to choose the right equations for apple juice viscosity determination when the heat transfer calculation error did not exceed 20% that is standard error for used dependency and for many others. To reduce this error on the base of obtained experimental data the correction coefficient was calculated. Therefore, the equation to calculate the heat transfer coefficient for boiling apple juice where maximum error
did not exceed 5% was obtained. The experimental research was conducted under atmospheric pressure. To obtain the value of heat transfer coefficient in vacuum condition the Tolubinskiy dependency can be used or addition experiments should be conducted. It depends of required accuracy level.
Опис
Zykov A. V. Experimental studies of boiling heat transfer of food solutions / A. V. Zykov, D. N. Reznichenko, I. V. Bezbah // Інноваційні енерготехнології - 2017: зб. пр. VI Міжнар. наук.-практ. конф., Одеса, 4-8 верес. 2017 р. / Одес. нац. акад. харч. технологій. - Одеса, 2017. – P. 238–243: fig. – Ref.: 11 tit.
Ключові слова
boiling, heat exchange, evaporation, concentration, vacuum