scholarly journals Matrix method to solve the inverse problem of heat transfer in heat exchangers

Vestnik IGEU ◽  
2021 ◽  
pp. 62-69
Author(s):  
V.P. Zhukov ◽  
A.Ye. Barochkin ◽  
M.S. Bobrova ◽  
A.N. Belyakov ◽  
S.I. Shuvalov
Keyword(s):  
Heat Transfer ◽  
Inverse Problem ◽  
Heat Exchange ◽  
Inverse Problems ◽  
Energy Saving ◽  
Heat Exchangers ◽  
Matrix Method ◽  
Heat Exchange Equipment ◽  
Design Calculations ◽  
Heat Carriers

Along with verification calculations of known designs of heat exchangers, in design engineering and when we develop new technologies, design calculations are necessary to solve the inverse problems of choosing the optimal designs and operating modes of equipment. Previously, the formulation and solution of inverse problems of classification and unsteady heat conduction have been considered, while the inverse problems of heat transfer in the design of heat exchange equipment are poorly presented in the literature. The development of methods to solve inverse problems in the design of heat exchange equipment is an urgent task of power industry. Matrix models of heat transfer based on mass and energy balance equations are used to formulate and solve inverse problems of heat exchange systems. Methods of mathematical programming are applied to solve inverse and optimization problems. For design calculations, a matrix method to solve inverse problems for choosing the design of devices and parameters of heat carriers that ensure the effective operation of the system is proposed. The inverse problem is formulated for the case of the sliding boundary of the beginning of the phase transition with the countercurrent type of movement of heat carriers. The obtained results can be used in power energy, chemical and food industries to improve the efficiency of designing resource-and energy-saving technologies. The solutions obtained can be implemented when developing measures to improve resource and energy saving technologies.

scholarly journals Matrix method to solve inverse problem of heat transfer in heat exchangers with phase transition in heat carriers

Vestnik IGEU ◽  
2021 ◽  
pp. 68-75
Author(s):  
A.E. Barochkin
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Inverse Problem ◽  
Heat Exchangers ◽  
Power Plants ◽  
Thermal Power ◽  
Energy Performance ◽  
Steam Boiler ◽  
Resource Saving ◽  
Heat Carriers

The transition to environmentally friendly and resource-saving energy, efficient use of natural resources and energy performance are the key priorities of the state energy policy of the Russian Federation. Maximum use of heat combustion of fuel and simultaneously production of condensate water of the combustion products of natural gas is one of the directions of energy saving policy. Despite many scientific papers on the issues of utilization of flue gas heat, condensation heat exchangers are not used in most gas boiler houses, energy power providers and thermal power plants in this country. And there are several reasons to explain this fact due to the lack of universal methods to calculate and design condensation-type heat exchangers. Thus, the development of new methods to simulate multithreaded heat exchangers considering the phase transition in heat carriers is an urgent task of power engineering and industry sectors. Matrix models of heat transfer based on mass and energy balance equations are applied to solve the inverse problem of heat transfer in heat exchangers, considering the phase transition in heat carriers. A method to calculate and select the designs of multi-threaded heat exchangers, considering the phase transition in heat carriers, has been developed. The author suggests a numerical solution to choose the design of a contact economizer of a heat power plant steam boiler used for heat recovery of flue gases to illustrate the effectiveness of the proposed method. The proposed method to solve the inverse problem of heat transfer provides the possibility to identify simultaneously the most acceptable values of the parameters of heat carriers and design characteristics of heat exchangers for various purposes.

scholarly journals Use of new similarities Bl and Blturb. to optimize the calculation and selection of heat exchange equipment for working with nanofluid coolants

2021 ◽  
Vol 23 (96) ◽  
pp. 46-53
Author(s):  
Y. Bilonoga ◽  
V. Stybel ◽  
O. Maksysko ◽  
U. Drachuk
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Exchangers ◽  
Seed Oil ◽  
Surface Forces ◽  
Express Method ◽  
Pumpkin Seed ◽  
Heat Exchange Equipment ◽  
Pumpkin Seed Oil ◽  
Selection Of

The problem of correct, exact calculation and selection of the optimal heat exchange equipment at use in it of nanoliquid heat carriers was investigated in the work. Classical numerical equations, which are widely used in the calculation and selection of heat exchangers with nanofluids, especially at temperatures above 50 °C, give an error of (15–20) % or more. This leads to the fact that the selected heat exchange equipment may not work efficiently with excessive consumption of thermal energy. A new approach to heat transfer processes is considered, taking into account the theory of J. Businesque, which gives an idea of turbulent viscosity and thermal conductivity, as well as comparing the resistance of the coolant flow to the nanoparticle with surface forces and considering turbulent fluid as Newtonian. It is shown that the consideration of the behavior of a nanoparticle in a turbulent liquid coolant without taking into account surface forces is inaccurate and erroneous. The physical content of the previously obtained new numbers of similarity Bl and Blturb is considered and the possibility of their effective application in the new numerical equation obtained by us for the calculation of heat exchangers using nanofluid coolants is shown. The existing express method of estimating the efficiency of nanorluids use in heat exchangers on the basis of classical numerical equations is analyzed and a new express method on the basis of a new numerical equation and new numbers of similarity Bl and Blturb is proposed. The proposed express calculation method shows that a mixture of H2O + EG (60:40) improves the heat transfer properties of water by + 12.86 %, and a mixture of (H2O + EG (60:40) + 1.5 % TiO2) and (milk) + 0.5 % pumpkin seed oil) – by +16.75 %, which corresponds to the experiments and our calculations, and the known express method based on classical numerical equations shows a deterioration of – 4.5 % and, accordingly, by – 1.2 %. An example of calculating the optimal shell-and-tube heat exchanger according to the new algorithm when heating milk with hot water with the addition of mixtures (H2O + EG (60:40) + 1.5 % TiO2) and accordingly (milk + 0.5 % pumpkin seed oil) fully confirms the correctness of the new express –method.

scholarly journals Application of porous materials in heat exchangers of heat supply system

2020 ◽  
Vol 22 (3) ◽  
pp. 3-13
Author(s):  
N. V. Rydalina ◽  
B. G. Aksenov ◽  
O. A. Stepanov ◽  
E. O. Antonova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Porous Materials ◽  
Heat Exchangers ◽  
Porous Metals ◽  
Porous Aluminum ◽  
Heat Exchange Equipment

Heat exchange capacity increase is one of the main concerns in the process of manufacturing modern heat exchange equipment. Constructing heat exchangers with porous metals is an advanced technique of heat exchange increase. A construction of heat exchangers with porous aluminum is described in this paper. The first heat transfer agent (hot water) flows through thin copper tubes installed within the porous aluminum. The second heat transfer agent (freon) flows through the pores of aluminum. Laboratory facility was created to study such a heat exchanger. Series of experiments were carried out. The purpose of the research presented here is to create a mathematical model of heat exchangers with porous metals, to perform analytical calculation of the heat exchangers and to confirm the results with the experimental data. In this case, one can`t use the standard methods of heat exchangers calculation because the pores inner surface area is indeterminate. The developed mathematical model is based on the equation describing the process of cooling the porous plate. A special mathematical technique is used to take into account the effect of tubes with water. The model is approximate but its solution is analytic. It is convenient. One can differentiate it or integrate it, which is very important. Comparison of calculated and experimental data is performed. Divergence of results is within the limits of experimental error. If freon volatilizes inside the heat exchanger, the heat of phase transition has to be taken into account alongside with heat capacity. The structure of the mathematical model makes it possible. The results presented in this paper prove the practicability of using porous materials in heat exchange equipment.

scholarly journals POLYMERS AND PLASTIC USE FOR THE HEAT-EXCHANGE EQUIPMENT (REVIEW)

2020 ◽  
pp. 59-71
Author(s):  
I.O. Mikulionok
Keyword(s):  
Heat Exchange ◽  
Heat Exchangers ◽  
Polymeric Materials ◽  
Strength Properties ◽  
Polymers And Plastics ◽  
Heat Exchange Equipment ◽  
Coefficient Of Heat Conductivity ◽  
Exchange Apparatus ◽  
Polymer Type

The possibility of use of the heat-exchangers in whole or in part manufactured with use of polymers and plastics is considered. Despite obvious, at first sight, inexpediency of use of polymeric materials in the heat-exchange equipment (low coefficient of heat conductivity, and also low, in comparison with metals, the strength properties of the majority of the most widespread polymers), «polymeric» heat-exchangers find application in various areas of the industry more and more surely. Classification of heat-exchange apparatuses which constructive elements are executed with use of polymeric materials is proposed. The following signs are the basis for classification: polymer type, a type of polymer meric material, type of the heat-exchange apparatus (a form of heat-exchange elements), reliance on polymeric materials in apparatuses, motion freedom of polymeric heat-exchange elements, level of assembly of a design, and also diameter of tubular elements. Critical analysis the most characteristic designs developed by domestic and foreign designers and inventors is carried out. Ref. 21, Fig. 13.

scholarly journals TAKING INTO ACCOUNT DEPENDENCE OF VISCOSITY COEFFICIENT ON TEMPERATURE DURING VAPOR CONDENSATION ON A VERTICAL WALL

2020 ◽  
Vol 63 (5) ◽  
pp. 94-101
Author(s):  
Aleksandr I. Moshinskiy ◽  
Pavel G. Ganin ◽  
Alla V. Markova ◽  
Larisa N. Rubtsova ◽  
Vladislav V. Sorokin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchange ◽  
Transfer Coefficient ◽  
Dynamic Viscosity ◽  
Viscosity Coefficient ◽  
Vapor Condensation ◽  
Condensation Temperature ◽  
Heat Exchange Equipment ◽  
The Heat Transfer Coefficient

In the present study, the problem of vapor condensation on a flat vertical surface is investigated in the case of an arbitrary dependence of the dynamic viscosity coefficient on temperature according to a fairly general law. At a constant value of this coefficient and other characteristics of a condensing liquid (heat conductivity coefficient, density) this task was considered by Nusselt in a constant gravitational field. The results obtained by Nusselt formed the basis (with certain modifications) for the computational practice of heat exchange equipment of chemical technology in the presence of steam condensation of any heat carrier. Formation of a condensate film occurs due to heat transfer through the liquid film, vapor condensation at the outer edge of the film and the flow of liquid along the surface. The article generalizes the Nusselt theory for the heat transfer coefficient under the indicated conditions, and as a result, convenient calculation formulas for the heat transfer coefficient, which are necessary to describe the operation of heat and mass exchange equipment. Approximate relations are proposed for calculating the dynamic viscosity coefficient, which are useful for calculating film flow on a flat surface. A comparison is made with the previously used ratios in an approximate manner taking into account the dependence of viscosity coefficient on temperature. When in technical applications one wants to determine the average value of two parameters, which are then used to calculate certain characteristics of a process, then, traditionally, the average of these parameters is considered. This article shows that by simplifying the dependence of the effective dynamic viscosity coefficient, more accurate results are obtained by dividing the interval of the width of the current film in the ratio of three to one, where three fourths refer to the wall temperature, and one fourth to the condensation temperature. The analytical dependencies presented in this paper can be used for practical calculations of the heat exchange equipment.

scholarly journals Horizontal earth-air heat exchanger for preheating external air in the mechanical ventilation system

2018 ◽  
Vol 13 (1) ◽  
pp. 71-76
Author(s):  
Vasyl Zhelykh ◽  
Olena Savchenko ◽  
Vadym Matusevych
Keyword(s):  
Heat Transfer ◽  
Mechanical Ventilation ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Exchangers ◽  
Convective Heat Transfer Coefficient ◽  
Ventilation System ◽  
Heat Pipes ◽  
Heat Exchanger Tube ◽  
Exchanger Tube

Abstract To save traditional energy sources in mechanical ventilation systems, it is advisable to use low-energy ground energy for preheating or cooling the outside air. Heat exchange between ground and outside air occurs in ground heat exchangers. Many factors influence the process of heat transfer between air in the heat exchanger and the ground, in particular geological and climatic parameters of the construction site, parameters of the ventilation air in the projected house, physical and geometric parameters of the heat exchanger tube. Part of the parameters when designing a ventilation system with earth-air heat exchangers couldn’t be changed. The one of the factors, the change which directly affects the process of heat transfer between ground and air, is convective heat transfer coefficient from the internal surface of the heat exchanger tube. In this article the designs of a horizontal earthair heat exchanger with heat pipes was proposed. The use of heat pipes in designs of a horizontal heat exchanger allows intensification of the process of heat exchange by turbulence of air flow inside the heat exchanger. Besides this, additionally heat transfer from the ground to the air is carried out at the expense of heat transfer in the heat pipe itself.

scholarly journals NOVEL TRENDS OF DEVELOPMENT AND PERFECTION THE MODERN HEAT EXCHANGERS

2019 ◽  
pp. 54-65
Author(s):  
B.S. Soroka
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Exchange Process ◽  
Combustion Products ◽  
Reynolds Analogy ◽  
Heat Exchange Equipment ◽  
Heat Exchange Process ◽  
Heat Transfer Phenomenon ◽  
Relative Change

Some actual aspects of advancement the problem of improvement the heat exchange equipment are considered in the paper. First of all the actual items related to middle and high temperature recuperators are discussed with proper up-to — date approaches. The classification of flue gases heat recovery appliances has been proposed along with the statement and analysis of the main characteristics of the recovery plants and option the ways of optimization the mentioned characteristics. The problem of Reynolds analogy (similarity of relative change the heat transfer phenomenon and variation the hydraulic resistance) within the channels of different purpose and of various cross-section supplied with and without the obstacles has been analyzed in application to separate cases of flow along the surfaces equipped with the cavities (dimples) or the convex elements. Thermal Performance Factor (TPF) of the heat exchange process is qualitatively like to Reynolds analogy factor and is highly depended upon rate of heat transfer and of friction factor in conditions of the scheme under consideration for flow over the surface or flow within the channel. The various media has been compared used as a working body in the heat exchanger’s channels: gaseous, liquid and the nanofluids, the last appeared in practice since 2000. Analysis has been carried out on effect of using the secondary energy emitters (SEE) arranged inside the tube channels, on resulting heat flux by heat exchange between outward flow of combustion products and the inner air flow. Bibl. 23, Fig. 6.

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