scholarly journals Intensification Simulation of Heat Transfer Process of Bakery-Confectionery Oven Power Generator by Numerical Method

2020 ◽  
pp. 85-89
Author(s):  
О.Г. Несиоловский ◽  
Р.Д. Адакин ◽  
И.М. Соцкая
Keyword(s):  
Heat Transfer ◽  
Heat Carrier ◽  
Transfer Process ◽  
Combustion Products ◽  
Heat Transfer Process ◽  
Bakery Products ◽  
Pitch Factor ◽  
Power Generator ◽  
Structural Modifications ◽  
Flow Friction

Рассмотрен вопрос интенсификации процесса теплоотдачи хлебопекарного теплообменного аппарата (ТА). ТА хлебопекарной печи имеет дополнительную конструктивную особенность – направляющий кожух. Предложено разместить на нём дефлекторы и направляющие пластины, которые изготовлены из нежаропрочных сталей, поскольку они напрямую не контактируют с продуктами горения, а лишь со вторичным теплоносителем. Дефлекторы – это небольшие пластины, установленные перпендикулярно стенке кожуха. Они позволяют образовывать локальные турбулентные завихрения теплоносителя, приводящие к увеличению теплоотдачи. Пластины направляют холодный теплоноситель на обтекание жаровой трубы камеры сгорания, дополнительно повышая его температуру. В результате численных моделирований установлены оптимальные зазоры между дефлекторами и трубками ТА, а также угол атаки направляющих пластин. Данная методика может быть применена к любым размерам трубок ТА, при соблюдении углов пластин и коэффициента шага между дефлектором и трубкой ТА. Установка на кожухе дефлекторов и пластин, как показывает моделирование, не приводит к существенному увеличению гидравлического сопротивления. Предложенные конструктивные доработки приводят к повышению значений теплоотдачи от 10 до 40%, в зависимости от скорости теплоносителя. Использование дефлекторов и направляющих пластин ведёт к повышению КПД ТА, снижению расхода топлива, более эффективному использованию выработанного тепла для выпечки хлебобулочных изделий. The issue of intensification of heat transfer process of bakery heat exchanger (HE) is considered. The baking oven HE has an additional structural feature – a guiding jacket. It is proposed to place deflectors and guide plates on it which are made of non-high-temperature steels, since they do not directly contact the combustion products, but only with the secondary coolant. Deflectors are small plates installed perpendicular to the wall of the casing. They allow the formation of local turbulent swirls of the coolant, leading to an increase in heat carrier. Plates direct cold heat carrier to flow around flame tube of combustion chamber, additionally increasing its temperature. As a result of numerical simulations, optimal gaps between deflectors and HE tubes are installed, as well as angle of attack of guide plates. This technique can be applied to any size of the HE tubes, in accordance with plate angles and pitch factor between the deflector and the HE tube. Installation of deflectors and plates on the casing, as the simulation shows, does not lead to a significant increase in flow friction. The proposed structural modifications lead to an increase in heat transfer values from 10 to 40%, depending on the coolant speed. The use of deflectors and guide plates leads to an increase in the coefficient of efficiency of HE, a decrease in fuel consumption, and a more efficient use of the generated heat for baking bakery products.

scholarly journals МОДЕЛЮВАННЯ ФАЗОВИХ ПЕРЕХОДІВ «ТВЕРДЕ ТІЛО - РІДИНА» ТЕПЛОАКУМУЛЮЮЧИХ МАТЕРІАЛІВ ПРИ ДОСЛІДЖЕННІ ПРОЦЕСУ ТЕПЛООБМІНУ

2018 ◽  
Vol 82 (1) ◽  
Author(s):  
Тетяна Володимирівна Корінчевська ◽  
Юрій Федорович Снєжкін ◽  
Володимир А. Михайлик
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Carrier ◽  
Transfer Process ◽  
Heat Storage ◽  
Heat Transfer Process ◽  
Storage Material ◽  
Storage Element ◽  
Heating And Cooling ◽  
Heat Storage Material

На сьогодні задача акумулювання теплової енергії є досить актуальною. Перспективним напрямком є використання теплоакумулюючих матеріалів з фазовим переходом. При цьому важливо вибрати матеріал, який зможе забезпечити теплові та експлуатаційні параметри процесу. Як такий матеріал запропоновано використовувати суміш на основі 85 % парафіну та 15 % буровугільного воску, що використовується в ливарному виробництві. В даній роботі розглянуті теоречні та експериментальні дослідження процесу теплообміну при фазових переходах «тверде тіло - рідина», що відбуваються при нагріванні та охолоджені теплоакумулюючого матеріалу. Для вивчення процесу була прийнята модель акумулятора капсульного типу, що складається з теплоакумулюючих елементів, якими є тонкостінні металеві трубчасті контейнери, заповнені матеріалом з фазовим переходом. Експериментально та теоретично процес теплообміну з урахуванням фазового переходу теплоакумулюючого матеріалу було змодельовано на прикладі окремого теплоакумулюючого елемента. В результаті отримано розподіл температури в теплоакумулюючому елементі під час охолодження (від 80 до 22 °С) та нагрівання при контакті зовнішньої стінки металевої капсули з теплоносієм, нагрітим до 80 °С та з теплоносієм, що нагрівається зі швидкістю 0,35, 0,77 і 1,17 К/хв. від 22 до 80 °С. Було підтверджено, що при використанні невеликих об’ємів капсул конвективною складовою в рівнянні теплопровідності можна знехтувати. Співставлення даних результатів з експериментальними показало адекватність результатів розрахунків. Порівняння результатів експериментальних та теоретичних досліджень підтверджують можливість використання принципу ефективної теплоємності для розрахунку теплообміну при фазовому переході та дозволяють досить точно передбачити фактичний час нагрівання та охолодження. Результати розрахунків також підтвердили дані, одержані експериментально – під час нагрівання з високою швидкістю спостерігається висока неоднорідність температурного поля в межах розрізу. Експериментально виявлено, що не має сенсу застосовувати високу швидкість нагрівання. В результаті визначені особливості кінетики нагрівання та охолодження при фазовому переході, що дозволило встановити раціональний режим нагрівання. At present, the problem of heat storage is very relevant. The promising direction is the use of the heat storage materials with phase change. It is important to choose a material that can provide the thermal and operational parameters of the process. As a material, a mixture of 85% wax and 15% brown coal wax was suggested to be used. This mixture is used in foundry work. In this paper, theoretical and experimental studies of the heat transfer process during solid - liquid phase change occurring during heating and cooling of the heat storage material are considered. The model of a heat storage system of capsular type was adopted to study the process. It consists of the heat storage elements – thin-walled metallic tubular containers filled with phase change material. The heat transfer process taking into account phase change of the heat storage material is experimentally and theoretically simulated on the example of a separate heat storage element. As a result, the temperature distribution is obtained in the heat storage element during cooling (from 80 to 22 °C) and heating at contact external wall of metal capsule with heat carrier heated to 80 °C and heat carrier, which heated with a speed of 0.35, 0.77 and 1.17 K/min. from 22 to 80 °C. It was confirmed that the convective component in the heat conduction equation can be neglected at using small volume of capsule. Comparison of theoretical and experimental results showed the adequacy of the results of calculations. Comparison of experimental and theoretical studies confirm the ability to use the principle of effective specific heat to calculate the heat transfer at the phase change and allows one to accurately predict the actual time of heating and cooling. The results of studies also confirmed the data obtained experimentally - high heterogeneity of the temperature field is observed within the cross section during heating with high speed. It is experimentally revealed that it makes no sense to use a high heating rate. As a result, features of the kinetics of heating and cooling have been determined during the phase change. This will make it allowed to determine a rational mode of heating.

Design of the Blast Furnace Wall Structure Made of Efficient Materials. Part 4. Calculation Examples

2020 ◽  
Vol 786 (11) ◽  
pp. 30-34
Author(s):  
A.M. IBRAGIMOV ◽  
◽  
L.Yu. GNEDINA ◽  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Blast Furnace ◽  
Boundary Value Problems ◽  
Transfer Process ◽  
Rational Design ◽  
Boundary Value ◽  
Heat Transfer Process ◽  
Furnace Wall ◽  
Time Interval

This work is part of a series of articles under the general title The structural design of the blast furnace wall from efficient materials [1–3]. In part 1, Problem statement and calculation prerequisites, typical multilayer enclosing structures of a blast furnace are considered. The layers that make up these structures are described. The main attention is paid to the lining layer. The process of iron smelting and temperature conditions in the characteristic layers of the internal environment of the furnace is briefly described. Based on the theory of A.V. Lykov, the initial equations describing the interrelated transfer of heat and mass in a solid are analyzed in relation to the task – an adequate description of the processes for the purpose of further rational design of the multilayer enclosing structure of the blast furnace. A priori the enclosing structure is considered from a mathematical point of view as the unlimited plate. In part 2, Solving boundary value problems of heat transfer, boundary value problems of heat transfer in individual layers of a structure with different boundary conditions are considered, their solutions, which are basic when developing a mathematical model of a non-stationary heat transfer process in a multi-layer enclosing structure, are given. Part 3 presents a mathematical model of the heat transfer process in the enclosing structure and an algorithm for its implementation. The proposed mathematical model makes it possible to solve a large number of problems. Part 4 presents a number of examples of calculating the heat transfer process in a multilayer blast furnace enclosing structure. The results obtained correlate with the results obtained by other authors, this makes it possible to conclude that the new mathematical model is suitable for solving the problem of rational design of the enclosing structure, as well as to simulate situations that occur at any time interval of operation of the blast furnace enclosure.

Numerical Simulation for Microconvection Around Nano-Particle With Brownian Motion in Liquid

2003 ◽  
Author(s):  
B. X. Wang ◽  
H. Li ◽  
X. F. Peng ◽  
L. X. Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Brownian Motion ◽  
Numerical Model ◽  
Temperature Gradient ◽  
Transfer Process ◽  
Heat Transfer Process ◽  
Nano Particles ◽  
Analytic Method ◽  
Nano Particle

The development of a numerical model for analyzing the effect of the nano-particles’ Brownian motion on the heat transfer is described. By using the Maxwell velocity distribution relations to calculate the most possible velocity of fluid molecules at certain temperature gradient location around the nano-particle, the interaction between fluid molecules and one single nano-particle is analyzed and calculated. Based on this, a syntonic system is proposed and the coupled effect that Brownian motion of nano-particles has on fluid molecules is simulated. This is used to formulate a reasonable analytic method, facilitating laboratory study. The results provide the essential features of the heat transfer process, contributed by micro-convection to be considered.

The 3-D Numerical Simulation of Heat Transfer Process of Finned Copper Tube

2011 ◽  
Vol 393-395 ◽  
pp. 412-415
Author(s):  
Jian Hua Zhong ◽  
Li Ming Jiang ◽  
Kai Feng
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Theoretical Calculations ◽  
Structural Parameters ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Finned Tube ◽  
Copper Tube ◽  
Central Air Conditioning ◽  
Fin Thickness

In this article, finned copper tube used in the central air conditioning was acted as the discussed object. According to the combination with actual processing and theoretical calculations, Five finned tube was selected with typical structural parameters, and established their entity model using Pro/E, then the heat transfer process of finned tube was simulated through the ANSYS, the effect of the fin height, fin thickness and other structure parameters to the heat transfer enhancement of finned tube was researched. Meantime the efficiency of the heat transfer under different convection heat transfer coefficient was also studied.

Numerical Study on the Effect of Inner Tube Position on Heat Transfer Process in Self-Recuperative Radiant Tube

2011 ◽  
Vol 228-229 ◽  
pp. 676-680 ◽  
Author(s):  
Ye Tian ◽  
Xun Liang Liu ◽  
Zhi Wen
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Numerical Study ◽  
Flame Temperature ◽  
Three Dimensional ◽  
Mathematic Model ◽  
Heat Transfer Process ◽  
Bulk Temperature ◽  
Radiant Tube ◽  
Peak Value

A three-dimensional mathematic model is developed for a 100kw single-end recuperative radiant tube and the simulation is performed with the CFD software FLUENT. Also it is used to investigate the effect of distance between combustion chamber exit and inner tube on heat transfer process. The results suggest that the peak value of combustion flame temperature drops along with the increasing of distance, which leads to low NOX discharging. Also radiant tube surface bulk temperature decreases, which causes radiant tube heating performance losses.

Study the Heat Transfer Process From Electron-Phonon Nonequilibrium in Thin Gold Film to Glass Substrate Through Transient Thermoreflectance Measurements

2010 ◽  
Author(s):  
Weigang Ma ◽  
Haidong Wang ◽  
Xing Zhang ◽  
Wei Wang
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Borosilicate Glass ◽  
Glass Substrate ◽  
Physical Vapor Deposition ◽  
Gold Film ◽  
Coupling Factor ◽  
Heat Transfer Process ◽  
Thin Gold Film ◽  
Open Question

How the energy transfers during electron-phonon nonequilibrium in thin metal films is still an open question, and how to measure the intrinsic thermal transport properties of the material under the covering layer is another challenge. In this paper, the heat transfer process from electron-phonon nonequilibrium in thin gold film to borosilicate glass substrate has been studied by resorting to different segments of the transient thermoreflectance signal, which is obtained from the rear-pump front-probe transient thermoreflectance technique. The gold film, which has a thickness of 23.1 nm, is deposited on the borosilicate glass substrate using using a physical vapor deposition (PVD) approach. Within the framework of the two-temperature model (TTM), the electron-phonon (e-ph) coupling factors of the gold film, which reflect the strength of heat flow from hot electrons to cold phonons, are derived from the signal taken after the first several picoseconds with different pump fluences, and the measured value is (1.95–2.05)×1016 W m−3 K−1. The electron-phonon coupling factor does not significantly change in response to the pump pulse fluence variation and exhibits little change compared to the bulk gold value 2.4×1016 W m−3 K−1. Furthermore, the thermal conductivity of the glass substrate is obtained through the thermoreflectance signal between 20 to 140 picoseconds and the value is W m−1 K−1.

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