ANALYTICAL METHOD FOR DETERMINING THE THICKNESS OF DEPOSITS ON THE INTERNAL SURFACES OF HEAT EXCHANGERS

2019 ◽  
Vol 9 (1) ◽  
pp. 20-24
Author(s):  
Olga Yu. KURGANOVA ◽  
Igor V. KUDINOV ◽  
Ruslan M. KLEBLEEV ◽  
Ekaterina V. STEFANYUK ◽  
Tatiana E. GAVRILOVA

Using the exact analytical solution of the stationary thermal conductivity problem for a two layer flat wall under inhomogeneous boundary conditions of the first and third kind, an analytical method for thickness determination of the sediment layer on the inner surface of the pipeline wall by the temperature known from the experiment on its outer surface is developed. The thickness of the deposits is found from the solution of the inverse problem by substituting the experimental value of the temperature of the outer surface of the wall into the formula of an accurate analytical solution. According to the results of theoretical studies, the thickness of the deposits was equal to 1.3 cm. Due to the large diameter of the pipeline (0.6 m) and the insignificant thickness of the two layer wall (0.016 m), it was assumed to be flat. The thickness of the deposits according to experimental studies was equal to 1.1 cm. Therefore, the discrepancy between the results of theoretical and experimental studies is 15.3%. The sequence of obtaining a solution to a similar problem for a cylindrical wall is also presented.

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1442
Author(s):  
Zhimeng Liang ◽  
Chunyi Cui ◽  
Kun Meng ◽  
Yu Xin ◽  
Huafu Pei ◽  
...  

Based on the Rayleigh–Love rod model and Novak’s plane-strain theory, an analytical method for the longitudinal vibration of a large-diameter pipe pile in radially heterogeneous soil is proposed. Firstly, the governing equations of the pile-soil system are established by taking both the construction disturbance effect and transverse inertia effect into account. Secondly, the analytical solution of longitudinal dynamic impedance at the pile top can be achieved by using Laplace transform and complex stiffness transfer techniques. Thirdly, the present analytical solution for dynamic impedance can also be performed in contrast with the existing solution to examine the correctness of the analytical method in this work. Further, the effect of pile Poisson’s ratio, pile diameter ratio as well as soil disturbed degree on the dynamic impedance are investigated. The results demonstrate that the Rayleigh–Love rod is appropriate for simulating the vibration of a large-diameter pipe pile in heterogeneous soils.


2021 ◽  
Vol 4 (4) ◽  
pp. 36-43
Author(s):  
Vyacheslav Ogarkov ◽  
Aleksei Aksenov ◽  
Sergei Malyukov ◽  
Aleksandr Knyazev ◽  
Nikolai Borodin

The problem of pure bending of an elastic curved beam with a given moment M is considered. It is proved that the values of stresses and strains found in this paper depend on the value of the Poisson's ratio μ. An exact analytical solution to this problem is obtained with the determination of unambiguous expressions for stresses and deformations.


2020 ◽  
Vol 3 (3) ◽  
pp. 81-93
Author(s):  
Vyacheslav Ogarkov ◽  
Aleksei Aksenov ◽  
Sergei Malyukov

The actual scientific and technical problem of polar-symmetric deformation of an elastic cylinder under conditions of temperature and humidity influences is considered. An exact analytical solution to this problem is obtained with the determination of unambiguous expressions for stresses, deformations and radial displacement. The obtained solution allows solving this problem for an incompressible material with μ = 1/2 as a special case.


2020 ◽  
pp. 123-128
Author(s):  
A. S. Bryukhova ◽  

The paper presents the results of experimental studies on the determination of corrosion products on the surface of reinforced concrete structures. Methods for creating samples with artificial electrocorrosion under conditions close to real operation are discussed. The results of testing samples with different degrees of corrosion using laser-spark emission spectrometry (LIBS) devices are presented. The test is carried out on two different devices, a LIBS setup and a portable American-made laser analyzer LIBZ-300pe


Author(s):  
S.V. Ilyanov ◽  
◽  
N.A. Kuzmin ◽  
G.V. Borisov ◽  
◽  
...  

At the moment, there is a large number of dissertations and scientific works covering the issues of traction-speed and fuel-economic characteristics of vehicles, the results of which are presented in the form of: regression models, approximating dependencies, mathematical models based on multivariate analysis, including a number of additional coefficients. In this connection, the use of the results of these works in practice is limited, since it requires high qualifications of the МTЕ personnel and the use of special software and hardware. At the same time, at the department “Automobile transport” NSTU named after R. E. Alekseev developed a probabilistic-analytical method for predicting fuel consumption by road trains, considering the high-speed mode of movement, which shows a high convergence of results with actual average speeds only for uniform movement of buses with a constant average speed, which is not applicable to the assessment of fuel consumption of city buses. Based on the hypothesis put forward on the applicability of the Weibull-Gnedenko distribution for calculating the average speeds of city buses and the normal distribution for calculating accelerations during movement, the tasks of this study are formulated, expressed in the development of mathematical models reflecting the dependences of speeds and accelerations during bus movement in urban operating conditions, for planning their fuel consumption. To solve the set tasks, the following experimental studies were carried out: determination of the average coefficient of total road resistance; the actual distribution of speeds and accelerations when driving city buses; determination of the average actual value of fuel consumption when the bus is moving and when idle at stopping points. Based on the results of processing experimental studies, the possibility of using the Weibull-Gnedenko law to describe the actual speeds in urban conditions and the normal law to describe accelerations when driving city buses was confirmed, which allows planning fuel consumption using the analytical apparatus of the theory of probability and mathematical statistics and using the developed methodology in practice of motor transport enterprises. Based on experimental studies and theoretical studies in this area, an analytical method for planning fuel consumption for city buses, considering the speed of their movement, has been developed, which allows planning fuel consumption without additional experiments. Carrying out such studies for other types of motor vehicles and assessing unaccounted for indicators of road, transport and natural-climatic operating conditions will create a generalized analytical method for planning fuel consumption by vehicles in various operating conditions.


Author(s):  
E. Pereyra ◽  
R. Arismendi ◽  
L. Gomez ◽  
R. Mohan ◽  
O. Shoham ◽  
...  

Determination of gas entrainment in slug flow is crucial for the prediction of slug flow characteristics and separator performance. A summary of all available correlations and mechanistic models for the prediction of slug liquid holdup is presented. Additionally, an experimental data base for slug liquid holdup has been collected from available literature. The data base shows a gap for large diameter pipes, high pressure systems and high viscosity liquids. A comparison between the predictions of available models and correlations against the data base is presented, identifying the range of applicability of the different methods. The correlations have been tuned with the new data showing an improved performance. Also, the uncertainties of the correlations parameters are evaluated and presented. Based on this study, a recommendation for the best method for predicting the slug liquid holdup is provided.


Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.


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