Перегляд за Автор "Ryabchuk, Alexander"

Зараз показуємо 1 - 3 з 3

Heat transfer in the evaporation channels of film evaporators
(2013) Ryabchuk, Alexander; Petrenko, Valentin
There is an urgent need in the reliable correlation allowing calculation of heat transfer coefficients to highly concentrated films boiling at vacuum, which refers to the operational regimes of vacuum pans of multistage evaporators in the sugar industry. According to the stated objective, a rigorous study into thermo - and hydrodynamic parameters of film flows has been carried out. For this purpose a special experimental rig aimed at the modeling of two - phase flows with independent phases’ flow rates formation has been developed and erected. Experimentation enveloped the regimes of evaporation free interphase surface as well as boiling at forced convection in down falling liquid films of sugar solutions within a wide range of concentrations at atmospheric pressure and vacuum. The solution mass concentration range d within 0…72%. Analysis of the obtained data has proven, firstly, that the resultant of correlation may be based on the idea of the inter – phase turbulence suppression. Secondly, experimental data showed that the simple criteria of the onset of the nuclear boiling in – films could be formed with the limiting condition of the steam phase appearing: which is overheating of the heat transfer surface with the given roughness of it. The resultant equation which can be used for the calculations of heat transfer coefficients to the saturated gravitational falling films in pipes is derived. This equation can be used equally within the regime of evaporation from the interphase as well as within the regime of nucleate boiling at forced convection.
Modeling of heat transfer in down flowing annular vapor-liquid flows
(2022) Petrenko, Valentin; Pryadko, Nikolai; Ryabchuk, Alexander; Boyko, Volodymyr
Water retention capacity of sugar beet pulp dried by various methods
(2015) Ivashchenko, Natalia; Shutyuk, Vitaliy; Bondar, Vladimir; Ryabchuk, Alexander
Dried sugar beet pulp should become one of the main ingredients of cattle forage in Ukraine, and so production of such pulp is a very important task, given the necessity of processing by-products of the sugar industry in the absence of large cattle-breeding complexes. Materials and methods. Fresh sugar beet pulp has been used as a food product in a form of an extracted chopped straw of 50 micrometers to 1 mm, with the moisture content of 76 to 80 %. Researches with application of the convection drying method have been conducted in the DNG-9035A drying cabinet. The water retention capacity was determined as a ratio of the amount of water retained by the fibres and remaining in the test tube after centrifuging, and the corresponding amount of dry substances (accuracy ±1 g of water/g of dry substances). Based on the conducted experiment analysis, it has been determined that the pulp dried by the low-temperature method mostly swells in the first 15 to 20 minutes. Within this time period, soaking up to the recovery coefficient β = 0,84…0,89 takes place. The maximum value of the recovery coefficient amounts to 0,93 per 30 minutes for the pulp dried with hot air at the temperature of 100 °С. As a result of conducted experiments, we have determined that the granulated pulp dried under such method swells within the first 20 minutes, whereas the pulp shreds swell within the first 80 minutes. Within this time period, soaking up to β = 0,69 takes place. The maximum value of the granulated pulp recovery coefficient amounts to 0,76 per 35 minutes. However, afterwards, due to mechanical damages in the process of granulation, the product loses its shape completely, and turns into a liquid powder concentrate. The maximum value of the pulp shreds recovery coefficient amounts to 0,78 per 105 minutes. An excessive heat strain per each unit of the material causes considerable destruction of the capillary porous pulp structure, and formation of a crust on the surface, therefore moisture penetration into the material is complicated, and so the liquid interacts with the solid material structure quite slowly. Moisture does not penetrate into destructed cells, and fills open capillaries and pores of the material only. More destructed structure of the pulp facilitates renewal of initial properties as a result of moisture absorption. However, the ability to absorb moisture after drying is one of the necessary conditions determining the quality of final product.