Modeling of Operating Modes Gas Composite Cylinders

2021 ◽  
pp. 49-59
Author(s):  
Н. Н. Осипова ◽  
Б. М. Гришин
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cylinder Wall ◽  
Operating Modes ◽  
Hydrocarbon Gas ◽  
Gas Consumption ◽  
Approximate Dependence ◽  
The Heat Transfer Coefficient ◽  
Composite Cylinders

Состояние проблемы. Появление на рынке композитных баллонов обеспечивает ряд технологических и эксплуатационных преимуществ по сравнению с металлическими баллонами сжиженного углеводородного газа. В то же время отсутствие в научной литературе обоснованных рекомендаций по определению паропроизводительности баллонов по режимам их эксплуатации ограничивает их широкое внедрение в газовую практику. Результаты. Разработана математическая модель, учитывающая эксплуатацию баллона в режиме периодического газопотребления, рассчитан коэффициент неравномерности газопотребления в течение суток, определены значения коэффициента теплопередачи стенки композитного баллона, получена аппроксимирующая зависимость коэффициента теплопередачи от уровня заполнения баллона газом. Выводы. В результате проведенных исследований установлены критерии, влияющие на паропроизводительность композитных баллонов сжиженного углеводородного газа в различных режимах эксплуатации. Statement of the problem. The emergence of composite cylinders on the market offers a range of technological and operational advantages in comparison with metal cylinders of liquefied hydrocarbon gas. At the same time, the absence of substantiated recommendations for determining the vapor capacity of cylinders by modes of their operation in the scientific literature limits their wide implementation into gas practice. Results. A mathematical model considering the operation of the cylinder in the mode of periodic gas consumption is developed, the coefficient of non-uniformity of gas consumption during the day is calculated, the values of the heat transfer coefficient of the composite cylinder wall are identified, the approximate dependence of the heat transfer coefficient is obtained. Conclusions. As a result of the research, the criteria influencing steam productivity of composite cylinders of the liquefied hydrocarbon gas in various operating modes are found.

scholarly journals MODELING OF OPERATING MODES GAS COMPOSITE CYLINDERS

2021 ◽  
pp. 63-74
Author(s):  
N. N. Osipova ◽  
B. M. Grishin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cylinder Wall ◽  
Operating Modes ◽  
Hydrocarbon Gas ◽  
Gas Consumption ◽  
Approximate Dependence ◽  
The Heat Transfer Coefficient ◽  
Composite Cylinders

Statement of the problem. The emergence of composite cylinders on the market offers a range of technological and operational advantages in comparison with metal cylinders of liquefied hydrocarbon gas. At the same time, the absence of substantiated recommendations for determining the vapor capacity of cylinders by modes of their operation in the scientific literature limits their wide implementation into gas practice. Results. A mathematical model considering the operation of the cylinder in the mode of periodic gas consumption is developed, the coefficient of non-uniformity of gas consumption during the day is calculated, the values of the heat transfer coefficient of the composite cylinder wall are identified, the approximate dependence of the heat transfer coefficient is obtained. Conclusions. As a result of the research, the criteria influencing steam productivity of compositecylinders of the liquefied hydrocarbon gas in various operating modes are found.

scholarly journals AERODYNAMICS AND HEAT EXCHANGE OF SINGLE END TUBE DURING EXTERNAL FLOW

2021 ◽  
Vol 43 (4) ◽  
pp. 25-33
Author(s):  
A.P. Chyrkova ◽  
A.A. Khalatov ◽  
V.S. Oliynik ◽  
O.V. Shikhabutinova
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Urban Areas ◽  
Local Heat Transfer ◽  
Local Heat ◽  
External Flow ◽  
Cylinder Wall ◽  
Area Of Interest ◽  
The Heat Transfer Coefficient

In Ukraine, the safety of modern thermal power plants depends on the reliable operation of the equipment installed on them. Unfortunately, the technical condition of the chimneys is not properly maintained. Of course, the modernization of basic equipment (boilers, switching to another type of fuel) leads to a decrease in the temperature of the exhaust gases. An important aspect to maintain the condition of the chimneys is to maintain the moisture of the exhaust gases. An important feature of the external flow of chimneys are large Reynolds numbers Re = wd/n, which reach 106 and more. In the thermal calculation only the average heat transfer coefficient on the outer surface of the pipe is usually determined, and the features of aerodynamics and local heat transfer due to the conicity of the pipe are not taken into account. The work is devoted to the study of aerodynamics and heat transfer in the air flow of a single conical chimney. The method of computer modeling with numerical integration of equations of motion and energy was used in the research. At the first stage, the single pipe with the uniform flow profile is considered. Further, the influence of the surrounding infrastructure on the aerodynamics and heat transfer of a single conical tube is studied. The single conical vertical pipe with 40 m height, 1.7 m diameter at the base and 0.85 m in the mouth was used for the calculation. The computer model was calculated in the ANSYS2020-R1 program. The model is developed in a homogeneous area with the air environment. In order to obtain reliable results, the study was conducted to obtain the optimal set of the grid parameters for the heat transfer conditions. The grids with parameters that affect the distance of the first node from the cylinder wall (options a, b, c, d) and the rate of increase in the size of the elements as they move away from the area of interest (Growth rate GR) were studied. The type of the cylindrical pipe with constant diameter of 1.7 m has been chosen to analyze the sensitivity and to check the grid. The turbulence model has been choosen as the following: RNG k-ε model which is common for the tasks of this class, the Enhanced Wall Function, the solution algorithm for the connection of the velocity pressure in stable flows Simplex. It is determined that in case if the distance between the first node from the cylinder wall and the area of interest (Growth rate GR) is more than 8 mm, instability and deviation of the obtained data from the values of the average coefficient of more than 20% appears. As a result of the research, the parameter grid area matching to the “2d” option of table 1 has been selected, i.e.: GR = 1.1, h = 8 mm. In the study of aerodynamics and heat transfer, the conical tube is conventionally divided into 22 sections (with 1 m height each). The case of uniform flow velocity in front of the pipe has been considered. As seen, the maximum value of the heat transfer coefficient is in the Zone(21-22). The research shows that oncoming flow velocity of 25 m/s causes the average value of heat transfer coefficient of the conical pipe 62.5 W/m2K, and 61.1 W/m2K according to the known formula . This indicates a small effect of taper on the average heat transfer of the entire pipe. In the calculations, three types of surrounding areas are considered: A - open coasts of seas, lakes and reservoirs, rural areas, including buildings less than 10 m high; B - urban areas, forests and other areas, evenly covered with obstacles higher than 10 m; C - urban areas with dense buildings with buildings higher than 25 m. Thus, the wind speed profiles for different types of terrain are nonlinear. The wind speed profile in front of the pipe (type of terrain) has a significant effect on the heat transfer coefficient. This confirms the need to take into account the type of terrain and the velocity profile in front of the pipe for local heat transfer.

Evaporation of lignin-lean black liquor

TAPPI Journal ◽  
2015 ◽  
Vol 14 (7) ◽  
pp. 441-450
Author(s):  
HENRIK WALLMO, ◽  
ULF ANDERSSON ◽  
MATHIAS GOURDON ◽  
MARTIN WIMBY
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Black Liquor ◽  
Salt Content ◽  
Solubility Limit ◽  
Lignin Removal ◽  
Kraft Black Liquor ◽  
Black Liquors ◽  
The Heat Transfer Coefficient

Many of the pulp mill biorefinery concepts recently presented include removal of lignin from black liquor. In this work, the aim was to study how the change in liquor chemistry affected the evaporation of kraft black liquor when lignin was removed using the LignoBoost process. Lignin was removed from a softwood kraft black liquor and four different black liquors were studied: one reference black liquor (with no lignin extracted); two ligninlean black liquors with a lignin removal rate of 5.5% and 21%, respectively; and one liquor with maximum lignin removal of 60%. Evaporation tests were carried out at the research evaporator in Chalmers University of Technology. Studied parameters were liquor viscosity, boiling point rise, heat transfer coefficient, scaling propensity, changes in liquor chemical composition, and tube incrustation. It was found that the solubility limit for incrustation changed towards lower dry solids for the lignin-lean black liquors due to an increased salt content. The scaling obtained on the tubes was easily cleaned with thin liquor at 105°C. It was also shown that the liquor viscosity decreased exponentially with increased lignin outtake and hence, the heat transfer coefficient increased with increased lignin outtake. Long term tests, operated about 6 percentage dry solids units above the solubility limit for incrustation for all liquors, showed that the heat transfer coefficient increased from 650 W/m2K for the reference liquor to 1500 W/m2K for the liquor with highest lignin separation degree, 60%.

scholarly journals Systematic heat transfer measurements in highly viscous binary fluids

2021 ◽  
Author(s):  
Ann-Christin Fleer ◽  
Markus Richter ◽  
Roland Span
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volatile Component ◽  
Test Tube ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Low Viscosity ◽  
The Heat Transfer Coefficient

AbstractInvestigations of flow boiling in highly viscous fluids show that heat transfer mechanisms in such fluids are different from those in fluids of low viscosity like refrigerants or water. To gain a better understanding, a modified standard apparatus was developed; it was specifically designed for fluids of high viscosity up to 1000 Pa∙s and enables heat transfer measurements with a single horizontal test tube over a wide range of heat fluxes. Here, we present measurements of the heat transfer coefficient at pool boiling conditions in highly viscous binary mixtures of three different polydimethylsiloxanes (PDMS) and n-pentane, which is the volatile component in the mixture. Systematic measurements were carried out to investigate pool boiling in mixtures with a focus on the temperature, the viscosity of the non-volatile component and the fraction of the volatile component on the heat transfer coefficient. Furthermore, copper test tubes with polished and sanded surfaces were used to evaluate the influence of the surface structure on the heat transfer coefficient. The results show that viscosity and composition of the mixture have the strongest effect on the heat transfer coefficient in highly viscous mixtures, whereby the viscosity of the mixture depends on the base viscosity of the used PDMS, on the concentration of n-pentane in the mixture, and on the temperature. For nucleate boiling, the influence of the surface structure of the test tube is less pronounced than observed in boiling experiments with pure fluids of low viscosity, but the relative enhancement of the heat transfer coefficient is still significant. In particular for mixtures with high concentrations of the volatile component and at high pool temperature, heat transfer coefficients increase with heat flux until they reach a maximum. At further increased heat fluxes the heat transfer coefficients decrease again. Observed temperature differences between heating surface and pool are much larger than for boiling fluids with low viscosity. Temperature differences up to 137 K (for a mixture containing 5% n-pentane by mass at a heat flux of 13.6 kW/m2) were measured.

Test and Analysis on the Heat Transfer Coefficient of the Mixed Plate Heat Exchanger

2014 ◽  
Vol 552 ◽  
pp. 55-60
Author(s):  
Zheng Ming Tong ◽  
Peng Hou ◽  
Gui Hua Qin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Mixed Mode ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Fitting Method ◽  
Engineering Significance ◽  
The Heat Transfer Coefficient

In this article, we use BR0.3 type plate heat exchanger for experiment,and the heat transfer coefficient of the mixed plate heat exchanger is explored. Through the test platform of plate heat exchanger, a large number of experiments have been done in different mixed mode but the same passageway,and lots experimental data are obtained. By the linear fitting method and the analysis of the data, the main factors which influence the heat transfer coefficient of mixed plate heat exchanger were carried out,and the formula of heat transfer coefficient which fits at any mixed mode plate heat exchanger is obtained, to solve the problem of engineering calculation.The fact , there is no denying that the result which we get has great engineering significance

Identification of three-dimensional transient temperature fields in thick-walled elements using the inverse method

2018 ◽  
Vol 28 (1) ◽  
pp. 138-150 ◽  
Author(s):  
Magdalena Jaremkiewicz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Inverse Method ◽  
Thermal Stresses ◽  
Computing Time ◽  
Transient Temperature ◽  
Content Type ◽  
Inner Surface ◽  
The Heat Transfer Coefficient

Purpose The purpose of this paper is to propose a method of determining the transient temperature of the inner surface of thick-walled elements. The method can be used to determine thermal stresses in pressure elements. Design/methodology/approach An inverse marching method is proposed to determine the transient temperature of the thick-walled element inner surface with high accuracy. Findings Initially, the inverse method was validated computationally. The comparison between the temperatures obtained from the solution for the direct heat conduction problem and the results obtained by means of the proposed inverse method is very satisfactory. Subsequently, the presented method was validated using experimental data. The results obtained from the inverse calculations also gave good results. Originality/value The advantage of the method is the possibility of determining the heat transfer coefficient at a point on the exposed surface based on the local temperature distribution measured on the insulated outer surface. The heat transfer coefficient determined experimentally can be used to calculate thermal stresses in elements with a complex shape. The proposed method can be used in online computer systems to monitor temperature and thermal stresses in thick-walled pressure components because the computing time is very short.

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