Determination of the heat transfer coefficient of a rotary film evaporator with a heating film-forming element

A model of a rotary film evaporator with a film-forming element with a reflective heated surface has been developed. This will allow stabilizing the hydraulic movement of the cut wave flow due to the reflective surface of the geometric shape for the forced direction of the cut raw material to the heating surface. Autonomous heating of the reflective surface additionally provides a temperature effect in the conditions of movement of particles of raw materials after cutting. The analysis of the experimental and theoretical parameters of heat transfer made it possible to substantiate the criterion equation for determining the heat transfer coefficient of an evaporator with the proposed film-forming element and a reflective heated surface for calculating the coefficient from the working surface to the raw material. The resulting equation takes into account the influence of the vertical component of the motion of the raw material film, centrifugal movement during the rotation of the film-forming element, mixing of the boiling film of the raw material with steam bubbles, and the geometric characteristics of the film-forming blade on the hydrodynamic flow of the raw material. The calculation of the rotary-film evaporator was carried out using the criterion equation and the obtained useful heat exchange surface – 0.75 m2. The specific metal consumption in a rotary film evaporator with a film-forming element having a reflective surface is 57 kg/m2, compared to the vacuum evaporator traditionally used in canning industries (410 kg/m2), which is 7.1 times less. The duration of the temperature effect on the raw material is also reduced: a rotary film evaporator – 200 s and 3600 s in a traditional apparatus. The data obtained will be useful for the design of rotary-film devices of different geometric parameters using articulated blades with a reflective plate.

Study of heat transfer during steam condensation in the tubes of diesel radiator cores

The article contains an assumption about the practicability of using the processes of boiling and condensation of the coolant in the cooling system of a locomotive diesel in order to reduce the energy consumption of fans of the refrigerating chamber. The possibility of using of standard radiator cores of a diesel locomotive with flat tubes as steam condensers is considered. The results of the criterion equation of heat transfer from steam to a flat tube during condensation, obtained by the mathematical model of this process, are estimated. The assessment was carried out by comparison with experimental data. The influence of the initial steam velocity, the corresponding tube diameter, the working length of the tube, the physical properties of steam and condensate is considered. The comparison of the influence of these factors on heat transfer in round and flat tubes of a locomotive radiator core is carried out. The processed results of physical and numerical experiments for both circular and flat tubes are shown in the graphs and regression equations. The advantage of flat tubes over round ones in terms of heat transfer intensity during steam condensation, which can reach 24%, for a standard radiator core of a diesel locomotive was found.

EMPIRICAL DEPENDENCE OF THE HYDRAULIC RESISTANCE OF THE WA-TER LAYER OF THE REGULAR PACKING ON THE RESISTANCE COEFFI-CIENT AND IRRIGATION DENSITY

A criterion equation for the coefficient of hydraulic resistance of a layer of regular packing was ob-tained, and a dependence was obtained that connects the hydraulic resistance of a dry and irrigated packing.

Criteria Dependences to Calculate the Process of Extracting Humic Acids from Peat and Vermicompost in a Rotary Pulse Apparatus

The regularities of the process of extraction of humic acids (HA) from peat and vermicompost in a rotary pulse apparatus (RPA) have been investigated. It was found that to calculate the mass transfer coefficient, it is necessary to determine the specific power and the values of the Prandtl diffusion criterion; with an increase in the time (number of cycles) of suspension treatment in the RPA, the calculated values of the Prandtl criterion increase and the mass transfer coefficient decreases; the mass transfer coefficient increases with an increase in the specific power consumed for the extraction of HA from peat and vermicompost in the RPA. On the basis of experimental studies, the coefficients in the criterion equation for the process of HA extraction from peat and vermicompost in RPA have been determined.

Elaboration of a criterion heat transfer equation of electrostatic fields influence in kerosene medium at free convection and deposit formation

The paper focuses on the problem of deposit formation in engines and power plants operating on liquid hydrocarbon fuels and coolers, and analyzes hydrocarbon deposit formation on heated fuel-delivery metal at increased temperature. First, an experimental setup was created to study the effect of electrostatic fields on the heat transfer intensification in liquid aviation kerosene TS-1 and the process of deposit formation on a heated working plate. Then, the effect of electric wind on thermal processes was visualized using the Tepler optical setup and the influence of electrostatic fields on the processes of heat transfer of deposit formation in the kerosene medium when using coaxial needles as electrodes was studied. Finally, findings of the research were generalized and a new criterion equation with a created dimensionless similarity number of electric convection and deposit formation simplex was introduced.

Derivation of the Criterion Heat Transfer Equation for the Bakery Oven Heat Generator by Numerical Three-Dimensional Modeling

Рассмотрены вопросы передачи тепла в хлебопекарной печи от теплогенератора к вторичному холодному теплоносителю – воздуху, особенностью которого является высокая влажность. Передача тепла от теплогенератора к вторичному теплоносителю – сложный процесс. Несмотря на то, что по этой тематике написано много работ и проведено множество исследований, вопрос остаётся до сих пор не полностью изученным. Критериального уравнения, с помощью которого можно было бы определить числа Нуссельта для условий теплоотдачи к влажному теплоносителю, проходящему через шахматный пучок теплообменника, в источниках не представлено. С помощью трёхмерного численного моделирования воспроизведена виртуальная работа теплогенератора, в результате по полученным данным было выведено новое критериальное уравнение и получены коэффициенты теплоотдачи (α), позволяющие в конструктивном методе расчёта теплообменных аппаратов определить площадь теплоотдачи для условий влагосодержания в теплоносителе в интервале d = 0,1…0,6 кг влаги на 1 кг воздуха (в хлебопекарной печи другие условия влагосодержания не используются). Предлагаемое уравнение существенно повышает точность расчёта площади теплоотдачи самого теплогенератора, поскольку учитывает влияние влажности на процесс теплоотдачи. The issues of heat transfer in the bakery oven from the heat generator to the secondary cold heat-conducting medium, the peculiarity of which is high humidity are considered. Heat transfer from the heat generator to the secondary heat-conducting medium is a complex process. Despite the fact that many works have been written on this topic and many researches have been carried out, the question remains still not completely understood. The sources do not provide a criterion equation by which the Nusselt numbers can be determined for the heat transfer conditions to the humid coolant passing through the staggered bundle of the heat exchanger. Using three-dimensional numerical modeling the virtual operation of the heat generator was reproduced, as a result according to the obtained data a new criterion equation was derived and heat transfer coefficients (α) were obtained allowing in the constructive method of calculating heat exchangers to determine the heat transfer area for moisture content conditions in the heat carrier in the range d = 0.1...0.6 kg of moisture per 1 kg of air (other moisture content conditions are not used in the bakery oven). The proposed equation significantly increases the accuracy of calculating the heat dissipation area of ​ ​ the heat generator itself since it takes into account the influence of humidity on the heat transfer process.

A New Unified Solution for Circular Opening considering Different Strength Criteria and the Postpeak Elastic Strain Form

The strength criterion is an extremely important basis for evaluating the stability of surrounding rock and optimizing the support pressure design. In this paper, nine different strength criteria are summarized and simplified based on the reasonable assumption. Then, a new unified criterion equation is established, which includes all strength theories proposed by this paper. Meanwhile, a new unified closed-form solution for circular opening based on the newly proposed unified criterion equation is deduced with the infinite and finite external boundary combining with the nonassociative flow rule under plane strain conditions. In the plastic zone, four different elastic strain assumptions are applied to solving the plastic zone deformation considering the effect of rock mass damage. The solution’s validity is also verified by comparison with the traditional solution. Finally, the influences of strength criteria, dilation coefficient, elastic strain form of plastic zone, and rock mass damage on the mechanical response of surrounding rock are discussed in detail. The research result shows that TR and VM criteria give the largest plastic zone radius, followed by IDP, MC, and MDP criteria, and seem to underestimate the self-strength of rock mass; The CDP criterion gives the smallest plastic zone radius and may overestimate the self-strength of rock mass; UST0.5, GSMP, GMC, and GLD criteria that reasonably consider the effect of internal principal stresses give an intermediate range and can be strongly recommended for evaluating the mechanics and deformation behavior of surrounding rock; as the dilation coefficient gradually increases, the dimensionless surface displacement presents the nonlinear increase characteristics; the deformation of plastic zone and the ground response curve, which are closely related to the strength criteria, are also greatly influenced by the elastic strain assumption in the plastic zone and rock mass damage degree. The assumption that the elastic strain satisfies Hook’s law (Case 3) may be more reasonable compared with the continuous elastic strain (Case 1) and thick-walled cylinders (Case 2) assumptions; in addition, the Young’s modulus power function damage model seems to give more reasonable solution for the deformation of plastic zone and is suggested to be a preferred method for solving plastic displacement. The research results can provide very important theoretical bases for evaluating the tunnel stability and support design reliability of different lithology rock masses in underground engineering.

The Suggested Reciprocal Relationship between Maximum, Minimum and Optimum Usable Frequency Parameters Over Iraqi Zone

In this work, the relationship between the ionospheric parameters (Maximum Usable Frequency (MUF), Lowest Usable Frequency (LUF) and Optimum working Frequency (OWF)) has been studied for the ionosphere layer over the Iraqi zone. The capital Baghdad (44.42oE, 33.32oN) has been selected to represent the transmitter station and many other cities that spread over Iraqi region have represented as receiver stations. The REC533 communication model considered as one of the modern radio broadcasting version of ITU has been used to calculate the LUF parameter, while the MUF and OWF ionospheric parameters have been generated using ASAPS international communication model which represents one of the most advanced and accurate HF sky wave propagation models. The study has been conducted for the annual and seasonal time periods of the years (2009 and 2014) of the solar cycle 24. The results of the seasonal and annual tests have indicated that the interrelationship between the MUF and OWF with LUF was a fourth order polynomial equation, while the reciprocal relationship between the MUF and OWF was a simple relationship that could be represented by a linear regression equation. The reciprocal relationships between MUF, LUF and OWF parameters (present values) have shown a good fitting with the data generated using the international models (predicted values) and theoretical values calculated from the criterion equation.

The study of heat transfer coefficient while flow unsaturated liquid through the tube at pressure below critical

This work studies the temperature regime of the wall while up and down moving of the unsaturated liquid in the vertical tube at pressure below critical and influence of free convection on the heat transfer. The boundary of influence free convection on heat transfer is determined and summarized as a criterion equation.