Pub Date : 2024-04-10DOI: 10.1134/s1810232824010077
M. R. Leão, G. Lorenzini, T. M. Claudino, C. B. Maia, L. A. O. Rocha, L. A. Isoldi, E. S. D. Estrada, E. D. Dos Santos
Abstract
The present numerical work investigates by means of Constructal Design the influence of the geometry of an inclined passive wall solar chimney on the ventilation performance of an attached room. The main purpose is to maximize the mass flow rate of air in the chimney/attached room. The problem is subjected to two constraints: the chimney and room areas. Three degrees of freedom are investigated: the ratio between the exit and inferior bases widths of the chimney ((W_{e}/W_{g})), the ratio between the width of the chimney inferior basis and the absorber wall height ((W_{g}/H_{a})), and the ratio between the opening that connects chimney and room and the absorber wall height ((H_{i}/H_{a})). It is considered unsteady, incompressible, free convective, turbulent flows in a two-dimensional domain. The finite volume method is used to solve the time-averaged equations of continuity, momentum and conservation of energy. For closure of turbulence, it is employed the (k)-(varepsilon) model. Results showed that the best geometric configuration led to a mass flow rate 5.7 times superior than the worst configuration, showing the importance of solar chimney desing in this problem. Moreover, a strong sensibility of the investigated ratios on the mass flow rate was noticed.
{"title":"Numerical Study and Geometrical Investigation of an Inclined Passive Wall Solar Chimney over the Ventilation Performance of an Attached Room","authors":"M. R. Leão, G. Lorenzini, T. M. Claudino, C. B. Maia, L. A. O. Rocha, L. A. Isoldi, E. S. D. Estrada, E. D. Dos Santos","doi":"10.1134/s1810232824010077","DOIUrl":"https://doi.org/10.1134/s1810232824010077","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The present numerical work investigates by means of Constructal Design the influence of the geometry of an inclined passive wall solar chimney on the ventilation performance of an attached room. The main purpose is to maximize the mass flow rate of air in the chimney/attached room. The problem is subjected to two constraints: the chimney and room areas. Three degrees of freedom are investigated: the ratio between the exit and inferior bases widths of the chimney (<span>(W_{e}/W_{g}))</span>, the ratio between the width of the chimney inferior basis and the absorber wall height (<span>(W_{g}/H_{a}))</span>, and the ratio between the opening that connects chimney and room and the absorber wall height (<span>(H_{i}/H_{a}))</span>. It is considered unsteady, incompressible, free convective, turbulent flows in a two-dimensional domain. The finite volume method is used to solve the time-averaged equations of continuity, momentum and conservation of energy. For closure of turbulence, it is employed the <span>(k)</span>-<span>(varepsilon)</span> model. Results showed that the best geometric configuration led to a mass flow rate 5.7 times superior than the worst configuration, showing the importance of solar chimney desing in this problem. Moreover, a strong sensibility of the investigated ratios on the mass flow rate was noticed.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010065
M. N. Tamanna, M. Ferdows, G. Lorenzini, M. D. Shamshuddin, M. Usman
Abstract
Magnetohydrodynamic boundary layer flow and heat transmission processes with a hybrid nanofluid film over a steady stretched sheet are taken into consideration. The impressions of an angled magnetic field, tangent hyperbolic flow, and viscous dissipation upon the momentum and thermal boundary layer are investigated. The leading equations are PDEs transfigured into nonlinear, ordinary ones that apply a non-dimensional transformation. Spectral relaxation methods are exploited for numerical solutions to non-dimensional governing equations with no-slip boundary conditions. This simulation was constructed with the cooperation of the application MATLAB. Present outcomes are matched with literature in the limiting cases and are an excellent agreement. To analyze the flow behavior, thermal physical characteristics, and the nature of the hybrid nanofluid particles’ transport properties, we look at various kinds of hybrid nanofluid particles with the base fluid ethylene-glycol ((EG)), which are Ferro–Copper, ((Fe_{3}O_{4})–Cu) and Single walled carbon nanotubes–Copper Oxide, (SWCNT{-}CuO). The consequences of emerging parameters such as Magnetic parameter, Prandtl number, Brinkman number, Power law index, Weissenberg number, and Angle of inclination are explored through graphs The local skin friction and Nusselt number are also graphically displayed with respect to the above parameters.
{"title":"Numerical Investigation of Heat Transfer Enhancement on Tangent Hyperbolic Fluid over a Stretching Sheet with an Inclined Magnetic Field Filled with Hybrid Nanofluids","authors":"M. N. Tamanna, M. Ferdows, G. Lorenzini, M. D. Shamshuddin, M. Usman","doi":"10.1134/s1810232824010065","DOIUrl":"https://doi.org/10.1134/s1810232824010065","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Magnetohydrodynamic boundary layer flow and heat transmission processes with a hybrid nanofluid film over a steady stretched sheet are taken into consideration. The impressions of an angled magnetic field, tangent hyperbolic flow, and viscous dissipation upon the momentum and thermal boundary layer are investigated. The leading equations are PDEs transfigured into nonlinear, ordinary ones that apply a non-dimensional transformation. Spectral relaxation methods are exploited for numerical solutions to non-dimensional governing equations with no-slip boundary conditions. This simulation was constructed with the cooperation of the application MATLAB. Present outcomes are matched with literature in the limiting cases and are an excellent agreement. To analyze the flow behavior, thermal physical characteristics, and the nature of the hybrid nanofluid particles’ transport properties, we look at various kinds of hybrid nanofluid particles with the base fluid ethylene-glycol (<span>(EG)</span>), which are Ferro–Copper, (<span>(Fe_{3}O_{4})</span>–Cu) and Single walled carbon nanotubes–Copper Oxide, <span>(SWCNT{-}CuO)</span>. The consequences of emerging parameters such as Magnetic parameter, Prandtl number, Brinkman number, Power law index, Weissenberg number, and Angle of inclination are explored through graphs The local skin friction and Nusselt number are also graphically displayed with respect to the above parameters.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010144
I. I. Gogonin, O. A. Volodin
Abstract
Condensers represent an indispensable part of equipment of any power, chemical-technological, cryogenic, refrigeration and other installations used in industry. Reducing the weight, dimensions and cost of devices is always an urgent task. The process of condensation in real devices is a very complex phenomenon. The intensity of energy transfer from vapor to a solid cooled wall is determined, other things being equal, by three interrelated factors: (i) variable irrigation density and change in film flow hydrodynamics as the irrigation density changes, (ii) variable vapor velocity affecting a condensate film in the varying film and vapor flow regimes, and (iii) effect of the diffusion process on heat transfer during condensation of vapor with non-condensable impurities. The authors consider that they have to describe the issues that are poorly covered in the literature, although these issues are of fundamental importance for understanding the process under study. In this paper, the main factors that determine heat transfer during stationary vapor condensation on horizontal tube bundles are considered. An algorithm for calculating a condenser at film condensation of stationary vapor without non-condensable impurities is proposed. A critical analysis of modern experimental studies on heat transfer during condensation has been carried out.
{"title":"Fundamentals of Hydrodynamics and Heat and Mass Transfer at Film Condensation of Stationary Vapor on Horizontal Tube Bundles: A Brief Review","authors":"I. I. Gogonin, O. A. Volodin","doi":"10.1134/s1810232824010144","DOIUrl":"https://doi.org/10.1134/s1810232824010144","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Condensers represent an indispensable part of equipment of any power, chemical-technological, cryogenic, refrigeration and other installations used in industry. Reducing the weight, dimensions and cost of devices is always an urgent task. The process of condensation in real devices is a very complex phenomenon. The intensity of energy transfer from vapor to a solid cooled wall is determined, other things being equal, by three interrelated factors: (i) variable irrigation density and change in film flow hydrodynamics as the irrigation density changes, (ii) variable vapor velocity affecting a condensate film in the varying film and vapor flow regimes, and (iii) effect of the diffusion process on heat transfer during condensation of vapor with non-condensable impurities. The authors consider that they have to describe the issues that are poorly covered in the literature, although these issues are of fundamental importance for understanding the process under study. In this paper, the main factors that determine heat transfer during stationary vapor condensation on horizontal tube bundles are considered. An algorithm for calculating a condenser at film condensation of stationary vapor without non-condensable impurities is proposed. A critical analysis of modern experimental studies on heat transfer during condensation has been carried out.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010120
D. E. Alnak, K. Karabulut
Abstract
The impinging jet technique is a high-performance cooling technology for microchips which are basic elements of electronic systems and having high heat generation rates in small volumes. In this study, the improvement of heat transfer of the microchips used in all technological products today by air impinging jet has been examined. For this purpose, numerical research has been carried out on the cooling of copper plate surfaces with two different patterns, reverse triangle and reverse semi-circle shaped having 1000 W/m2 constant heat flux in rectangular cross-section ducts with adiabatic surfaces, by one and double air jets with distances of D(_{h}) and 2D(_{h}) between them. Numerical computation has been performed for energy and Navier–Stokes equations as steady and three-dimensional by employing the Ansys-Fluent computer program with the k-(varepsilon) turbulence model. The obtained results have been compared with the numerical and experimental results of the study in the literature and it has been seen that they are compatible with each other. The results have been presented as the mean Nu number and the variation of surface temperature for each of both patterned surfaces in single and double jet channels with different distances. Streamline and temperature contour distributions of the jet flow along the channel for different H/D(_{h}) ratios and jet numbers have been evaluated for both patterned surfaces. In double-jet and 2D(_{h}) distance channels compared to D(_{h}), at H/D(_{h}) = 12 and Re = 11,000, the Nu number increases of 67% and 65.9% have been observed on the first-row reverse triangle and semi-circular patterned surfaces, respectively.
摘要冲击射流技术是一种高性能冷却技术，适用于作为电子系统基本元件的微芯片，这些芯片体积小、发热量高。在这项研究中，我们探讨了如何通过空气冲击射流改善当今所有技术产品中使用的微型芯片的传热。为此，我们对铜板表面的冷却进行了数值研究，铜板表面有两种不同的形状，反三角形和反半圆形，在带有绝热表面的矩形横截面管道中具有 1000 W/m2 的恒定热通量，由一个和两个空气喷流冷却，两个空气喷流之间的距离分别为 D(_{h}) 和 2D(_{h})。通过使用 Ansys-Fluent 计算机程序和 k-(varepsilon) 湍流模型，对能量和纳维-斯托克斯方程进行了稳定的三维数值计算。所得结果与文献中的数值和实验研究结果进行了比较，结果表明两者是一致的。结果表明，在不同距离的单喷射通道和双喷射通道中，每个图案表面的平均 Nu 数和表面温度的变化都是不同的。对于两种图案表面，我们评估了不同H/D（_{h}）比和射流数下射流沿通道的流线和温度等值线分布。与 D(_{h}) 相比，在 H/D(_{h}) = 12 和 Re = 11,000 时，双射流和 2D(_{h}) 距离通道中，第一排反三角和半圆图案表面的 Nu 数分别增加了 67% 和 65.9%。
{"title":"Investigation of Heat Transfer Increment in Electronic System Surfaces by Different Air Jet Impingement Applications","authors":"D. E. Alnak, K. Karabulut","doi":"10.1134/s1810232824010120","DOIUrl":"https://doi.org/10.1134/s1810232824010120","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The impinging jet technique is a high-performance cooling technology for microchips which are basic elements of electronic systems and having high heat generation rates in small volumes. In this study, the improvement of heat transfer of the microchips used in all technological products today by air impinging jet has been examined. For this purpose, numerical research has been carried out on the cooling of copper plate surfaces with two different patterns, reverse triangle and reverse semi-circle shaped having 1000 W/m<sup>2</sup> constant heat flux in rectangular cross-section ducts with adiabatic surfaces, by one and double air jets with distances of D<span>(_{h})</span> and 2D<span>(_{h})</span> between them. Numerical computation has been performed for energy and Navier–Stokes equations as steady and three-dimensional by employing the Ansys-Fluent computer program with the k-<span>(varepsilon)</span> turbulence model. The obtained results have been compared with the numerical and experimental results of the study in the literature and it has been seen that they are compatible with each other. The results have been presented as the mean Nu number and the variation of surface temperature for each of both patterned surfaces in single and double jet channels with different distances. Streamline and temperature contour distributions of the jet flow along the channel for different H/D<span>(_{h})</span> ratios and jet numbers have been evaluated for both patterned surfaces. In double-jet and 2D<span>(_{h})</span> distance channels compared to D<span>(_{h})</span>, at H/D<span>(_{h})</span> = 12 and Re = 11,000, the Nu number increases of 67% and 65.9% have been observed on the first-row reverse triangle and semi-circular patterned surfaces, respectively.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010119
C. Gururaja Rao, K. Aditya
Abstract
The prime findings of a numerical investigation into conduction-convection-radiation heat transfer from an electronic gadget, modeled as a discretely and non-identically heated L-corner, are elucidated. In total, four heaters of different heights are assumed to be embedded in the gadget [three in the left and one in the bottom wall]. The partial differential equations describing temperature variation in the computational domain are deduced by balancing the heat generated with that transported by three possible modes of heat transfer. Air [assumed to be radiatively non-participating] is the medium used for cooling the gadget. Finite difference method is used to enable the governing equations acquire an algebraic form. Consequent equations are solved through the Gauss-Seidel algorithm. Full relaxation is imposed to update the local temperature as it gets iterated, and the iterations are made to halt when the maximum residue goes below 10−8. The effects of all the pertinent independent properties on different prominent results are rigorously probed into. The explicit role enacted by radiation in the work taken up here has been underlined through certain precisely executed results.
摘要 本文阐明了对一个电子小工具的传导-对流-辐射传热进行数值研究的主要结果，该小工具被模拟为一个离散且非相同加热的 L 角。假设在小工具中总共嵌入了四个不同高度的加热器（三个在左壁，一个在底壁）。通过平衡三种可能的热传导模式产生的热量和输送的热量，推导出描述计算域温度变化的偏微分方程。空气（假定不参与辐射）是用于冷却小工具的介质。使用有限差分法使控制方程获得代数形式。相关方程通过高斯-赛德尔算法求解。在迭代过程中，对局部温度进行完全松弛更新，当最大残差低于 10-8 时停止迭代。所有相关的独立属性对不同突出结果的影响都得到了严格探究。通过某些精确执行的结果，强调了辐射在本研究中的明确作用。
{"title":"Interactive Influence of Conduction–Convection–Radiation on Heat Transfer from a Discretely and Non-Identically Heated Electronic Gadget","authors":"C. Gururaja Rao, K. Aditya","doi":"10.1134/s1810232824010119","DOIUrl":"https://doi.org/10.1134/s1810232824010119","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The prime findings of a numerical investigation into conduction-convection-radiation heat transfer from an electronic gadget, modeled as a discretely and non-identically heated L-corner, are elucidated. In total, four heaters of different heights are assumed to be embedded in the gadget [three in the left and one in the bottom wall]. The partial differential equations describing temperature variation in the computational domain are deduced by balancing the heat generated with that transported by three possible modes of heat transfer. Air [assumed to be radiatively non-participating] is the medium used for cooling the gadget. Finite difference method is used to enable the governing equations acquire an algebraic form. Consequent equations are solved through the Gauss-Seidel algorithm. Full relaxation is imposed to update the local temperature as it gets iterated, and the iterations are made to halt when the maximum residue goes below 10<sup>−8</sup>. The effects of all the pertinent independent properties on different prominent results are rigorously probed into. The explicit role enacted by radiation in the work taken up here has been underlined through certain precisely executed results.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s181023282401003x
D. S. Elistratov, S. L. Elistratov, A. A. Chernov
Abstract
In this work, the process of dissociation of methane hydrate obtained under laboratory conditions in the form of a loose shapeless mass and in a pressed granular form, placed on a warm surface and on a surface covered with a thin layer of water, including the initiation of combustion of the gas released during the dissociation process, was experimentally studied. The rate of dissociation, the characteristic time of complete decomposition, and the proportion of water evaporating over a given time were determined for all cases considered. Based on the analysis of the dynamics of temperature ranges, as well as data illustrating the rate of mass loss by the sample, it was assumed that the process of dissociation of granular hydrate, both in the case without combustion and in the case of combustion, is accompanied by the phenomenon of self-preservation, which is not observed for loose hydrate.
{"title":"Experimental Study of the Process of Dissociation of Methane Hydrate Accompanied by Its Combustion","authors":"D. S. Elistratov, S. L. Elistratov, A. A. Chernov","doi":"10.1134/s181023282401003x","DOIUrl":"https://doi.org/10.1134/s181023282401003x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>In this work, the process of dissociation of methane hydrate obtained under laboratory conditions in the form of a loose shapeless mass and in a pressed granular form, placed on a warm surface and on a surface covered with a thin layer of water, including the initiation of combustion of the gas released during the dissociation process, was experimentally studied. The rate of dissociation, the characteristic time of complete decomposition, and the proportion of water evaporating over a given time were determined for all cases considered. Based on the analysis of the dynamics of temperature ranges, as well as data illustrating the rate of mass loss by the sample, it was assumed that the process of dissociation of granular hydrate, both in the case without combustion and in the case of combustion, is accompanied by the phenomenon of self-preservation, which is not observed for loose hydrate.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010089
V. E. Kroshilin
Abstract
An effective model for describing the relative motion of phases is the drift model, which uses simplified momentum equations that do not take into account inertial forces. For this model, in this paper, we study solutions for which various physical flow patterns are realized. The propagation velocity of the volume concentration of phases is analyzed, which has the most obvious physical meaning at zero phase volume velocity. Solutions with piecewise linear distributions are investigated. The evolution of the state in which at the initial moment of time the volume concentration of phase 1 on the left and right is constant and equal to (0.5+Delta) and (0.5-Delta), respectively, and in the transition zone with a width L linearly varies from the values on the left to the values on the right is studied. Two qualitatively different development scenarios are found. A problem is considered with a continuous distribution of phase volume concentrations at the initial moment of time at which a shock wave is formed (the graph is reversed): the propagation velocity of perturbations from the rear particles turns out to be greater than the velocity of propagation of perturbations from the front particles. A transition from a continuous distribution of volume concentrations of phases to a discontinuous distribution is constructed. The transition of the volume concentration profile of the first phase in the vicinity of the shock wave to a continuous distribution is analyzed taking into account diffusion terms proportional to the second derivative with respect to the coordinate. For this case, the volume concentration profile was studied. The main classes of solutions are found.
摘要 描述相位相对运动的一个有效模型是漂移模型，它使用简化的动量方程，不考虑惯性力。对于该模型，本文研究了实现各种物理流动模式的解决方案。本文分析了相体积浓度的传播速度，它在相体积速度为零时具有最明显的物理意义。本文还研究了具有片断线性分布的解。研究了在初始时刻，左侧和右侧相 1 的体积浓度分别恒定等于 (0.5+Delta) 和 (0.5-Delta)，并且在宽度为 L 的过渡区域内从左侧值到右侧值线性变化的状态的演变。发现了两种质的不同的发展情景。在形成冲击波的初始时刻，考虑了相体积浓度连续分布的问题（图形反转）：来自后方粒子的扰动的传播速度大于来自前方粒子的扰动的传播速度。构建了从相的体积浓度连续分布到不连续分布的过渡。考虑到与坐标二阶导数成比例的扩散项，分析了第一相在冲击波附近的体积浓度分布向连续分布的过渡。对这种情况下的体积浓度剖面进行了研究。发现了几类主要的解。
{"title":"Analytical Solutions of the Transport Equation for a Drift Model in an Unsteady Flow with Discontinuous Parameters","authors":"V. E. Kroshilin","doi":"10.1134/s1810232824010089","DOIUrl":"https://doi.org/10.1134/s1810232824010089","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>An effective model for describing the relative motion of phases is the drift model, which uses simplified momentum equations that do not take into account inertial forces. For this model, in this paper, we study solutions for which various physical flow patterns are realized. The propagation velocity of the volume concentration of phases is analyzed, which has the most obvious physical meaning at zero phase volume velocity. Solutions with piecewise linear distributions are investigated. The evolution of the state in which at the initial moment of time the volume concentration of phase 1 on the left and right is constant and equal to <span>(0.5+Delta)</span> and <span>(0.5-Delta)</span>, respectively, and in the transition zone with a width L linearly varies from the values on the left to the values on the right is studied. Two qualitatively different development scenarios are found. A problem is considered with a continuous distribution of phase volume concentrations at the initial moment of time at which a shock wave is formed (the graph is reversed): the propagation velocity of perturbations from the rear particles turns out to be greater than the velocity of propagation of perturbations from the front particles. A transition from a continuous distribution of volume concentrations of phases to a discontinuous distribution is constructed. The transition of the volume concentration profile of the first phase in the vicinity of the shock wave to a continuous distribution is analyzed taking into account diffusion terms proportional to the second derivative with respect to the coordinate. For this case, the volume concentration profile was studied. The main classes of solutions are found.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010028
S. Y. Misyura, M. M. Tokarev, V. S. Morozov, A. D. Grekova, L. G. Gordeeva
Abstract
Adsorption heat pumps are an alternative way of heat and cold generation. Due to the high adsorption capacity and high specific energy storage capacity, the SWS-1L adsorbent can be efficient in adsorption heat pumps. The physicochemical properties of various adsorbents and kinetics of adsorption and desorption of vapors of working fluids based on them have been studied quite well, and methods have been developed to optimize the efficiency of cycles with consideration of a large number of determining parameters: properties of adsorbent, temperature, pressure, and geometric parameters of the adsorbing heat exchanger. However, there is little experimental data on the change with time in the temperature of the free surface of a layer of adsorbent granules. It is important to know how this temperature varies for accurate calculation of the heat transfer parameters. The work shows that at the beginning of heating, the surface temperature of the heat exchanger (metal) without an adsorbent increases to a quasi-stable value within 40–45 s. In the presence of the adsorbent, this time almost doubles and corresponds to 70–75 s. Increase in the thermal fluid flow from 0.65 l/min to 2.7 l/min (4.1 times) leads to a 3.8-fold decrease in the heating time of the heat exchanger with the adsorbent (also approximately 4 times). The characteristic time of thermal inertia (along the thickness of the heat exchanger wall and along the height of the adsorbent layer) without and with the adsorbent is 0.5–1 s and 4–6 s, respectively. The growth of the thermal fluid velocity leads to a significant reduction in the heating time of the heat exchanger and adsorbent and can also reduce the desorption time in a heat pump.
{"title":"Influence of Flow Rate of Thermal Fluid on Duration of Heating of SWS-1L Adsorbent in Heat Exchanger","authors":"S. Y. Misyura, M. M. Tokarev, V. S. Morozov, A. D. Grekova, L. G. Gordeeva","doi":"10.1134/s1810232824010028","DOIUrl":"https://doi.org/10.1134/s1810232824010028","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Adsorption heat pumps are an alternative way of heat and cold generation. Due to the high adsorption capacity and high specific energy storage capacity, the SWS-1L adsorbent can be efficient in adsorption heat pumps. The physicochemical properties of various adsorbents and kinetics of adsorption and desorption of vapors of working fluids based on them have been studied quite well, and methods have been developed to optimize the efficiency of cycles with consideration of a large number of determining parameters: properties of adsorbent, temperature, pressure, and geometric parameters of the adsorbing heat exchanger. However, there is little experimental data on the change with time in the temperature of the free surface of a layer of adsorbent granules. It is important to know how this temperature varies for accurate calculation of the heat transfer parameters. The work shows that at the beginning of heating, the surface temperature of the heat exchanger (metal) without an adsorbent increases to a quasi-stable value within 40–45 s. In the presence of the adsorbent, this time almost doubles and corresponds to 70–75 s. Increase in the thermal fluid flow from 0.65 l/min to 2.7 l/min (4.1 times) leads to a 3.8-fold decrease in the heating time of the heat exchanger with the adsorbent (also approximately 4 times). The characteristic time of thermal inertia (along the thickness of the heat exchanger wall and along the height of the adsorbent layer) without and with the adsorbent is 0.5–1 s and 4–6 s, respectively. The growth of the thermal fluid velocity leads to a significant reduction in the heating time of the heat exchanger and adsorbent and can also reduce the desorption time in a heat pump.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1134/s1810232824010156
A. V. Barsukov, V. V. Terekhov, V. I. Terekhov
Abstract
The development of methods for intensifying heat transfer is a priority task in various technological processes in the energy sector and aerospace engineering. One of the effective ways to enhance heat transfer is to install mutually intersecting ribs on opposite walls of the channels (vortex matrices or latticework). The use of such channels leads to formation of a complex three-dimensional turbulent flow, which contributes to a significant enhancement of heat transfer. Most of available literature publications deal with the study of the integral characteristics of hydraulic losses and the degree of heat transfer enhancement depending on a large number of defining parameters. At that, the local flow structure and heat transfer have not been fully investigated. In particular, this conclusion relates to understanding the mechanism of the flow from subchannels formed by parallel ribs on opposite walls and interaction of these flows with the lateral bounding walls of the latticework. In this work, the main attention is paid to the study of the flow processes without the influence of the side walls of the channel. The results of numerical calculations of separated turbulent flow in a latticework obtained using the RANS and LES methods and the OpenFOAM package are presented here. Calculations were performed for the angles of rib crossing (2beta=60div120) on opposite heat transfer surfaces and the Reynolds number Re = (5,000div15,000), determined from the average flow rate and channel height. Data on the flow structure in a cell of a latticework were obtained. It is shown how the angle of crossing affects the interaction of flows in the lower and upper subchannels. The distribution of local heat transfer on the channel wall and the dependence of the average Nusselt number on the angle of crossing and the Reynolds number were obtained.
摘要 开发强化传热的方法是能源部门和航空航天工程中各种技术流程的优先任务。加强传热的有效方法之一是在通道相对壁上安装相互交叉的肋条（涡流矩阵或格状结构）。使用这种通道可形成复杂的三维湍流，从而显著提高传热效果。现有文献出版物大多涉及水力损失整体特性的研究，以及取决于大量定义参数的传热增强程度。但对局部流动结构和传热还没有进行充分研究。特别是，这一结论涉及到如何理解由相对壁上的平行肋条形成的子通道的流动机制，以及这些流动与格子间横向边界壁的相互作用。在这项工作中，主要关注的是研究不受渠道侧壁影响的流动过程。本文介绍了使用 RANS 和 LES 方法以及 OpenFOAM 软件包对格子中分离湍流进行数值计算的结果。根据平均流速和通道高度确定了相对传热表面的肋条交叉角（2beta=60div120）和雷诺数Re=（5,000div15,000）。获得了格子间内流动结构的数据。显示了交叉角如何影响上下子通道中流动的相互作用。还获得了通道壁上局部传热的分布情况以及平均努塞尔特数对交叉角和雷诺数的依赖关系。
{"title":"Numerical Study of Heat Transfer in a Lattice Matrix with Varying the Crossing Angle","authors":"A. V. Barsukov, V. V. Terekhov, V. I. Terekhov","doi":"10.1134/s1810232824010156","DOIUrl":"https://doi.org/10.1134/s1810232824010156","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The development of methods for intensifying heat transfer is a priority task in various technological processes in the energy sector and aerospace engineering. One of the effective ways to enhance heat transfer is to install mutually intersecting ribs on opposite walls of the channels (vortex matrices or latticework). The use of such channels leads to formation of a complex three-dimensional turbulent flow, which contributes to a significant enhancement of heat transfer. Most of available literature publications deal with the study of the integral characteristics of hydraulic losses and the degree of heat transfer enhancement depending on a large number of defining parameters. At that, the local flow structure and heat transfer have not been fully investigated. In particular, this conclusion relates to understanding the mechanism of the flow from subchannels formed by parallel ribs on opposite walls and interaction of these flows with the lateral bounding walls of the latticework. In this work, the main attention is paid to the study of the flow processes without the influence of the side walls of the channel. The results of numerical calculations of separated turbulent flow in a latticework obtained using the RANS and LES methods and the OpenFOAM package are presented here. Calculations were performed for the angles of rib crossing <span>(2beta=60div120)</span> on opposite heat transfer surfaces and the Reynolds number Re = <span>(5,000div15,000)</span>, determined from the average flow rate and channel height. Data on the flow structure in a cell of a latticework were obtained. It is shown how the angle of crossing affects the interaction of flows in the lower and upper subchannels. The distribution of local heat transfer on the channel wall and the dependence of the average Nusselt number on the angle of crossing and the Reynolds number were obtained.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140569560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-14DOI: 10.1134/s1810232823040069
V. E. Zhukov, N. N. Mezentseva
Abstract
The use of mixtures as refrigerants and heat carriers in various power systems has become widespread. The thermophysical properties of mixtures differ from the properties of their components. This paper presents the results of a study of the intensity of heat transfer to a non-azeotropic alcohol-water mixture with weight concentration of the volatile component of 20% during forced circulation in a heated smooth circular channel, as well as in a channel with spiral intensifiers with a hydrophobic coating. The experiments were carried out on a closed circulation circuit at a pressure in the storage vessel of 0.04–0.055 MPa. The test section was a stainless steel tube with inner diameter of 7.6 mm and wall thickness of 0.2 mm. The heating was provided due to the electric current passed in the tube wall. The spiral intensifiers had winding pitch of 4 mm; the thickness of the PTFE sleeve was 0.9 mm. The experiments were carried out at mass flux rates of 44–46 kg/m2 and 316 kg/m2. The heat flux density varied in the range (1200<q<15200) W/m2. The use of the spiral intensifiers with the hydrophobic coating during circulation of the non-azeotropic alcohol-water mixture (20%) in the circular channel led to the formation of a significant amount of the vapor-gas phase in the flow at channel wall temperatures below the saturation point of this mixture. The heat transfer coefficient in the channel with the intensifiers grew 2–5 times compared with those in a smooth channel.
摘要混合制冷剂作为制冷剂和热载体在各种电力系统中的应用越来越广泛。混合物的热物理性质与其组分的性质不同。本文介绍了挥发性组分质量浓度为20的非共沸醇水混合物的传热强度的研究结果% during forced circulation in a heated smooth circular channel, as well as in a channel with spiral intensifiers with a hydrophobic coating. The experiments were carried out on a closed circulation circuit at a pressure in the storage vessel of 0.04–0.055 MPa. The test section was a stainless steel tube with inner diameter of 7.6 mm and wall thickness of 0.2 mm. The heating was provided due to the electric current passed in the tube wall. The spiral intensifiers had winding pitch of 4 mm; the thickness of the PTFE sleeve was 0.9 mm. The experiments were carried out at mass flux rates of 44–46 kg/m2 and 316 kg/m2. The heat flux density varied in the range (1200<q<15200) W/m2. The use of the spiral intensifiers with the hydrophobic coating during circulation of the non-azeotropic alcohol-water mixture (20%) in the circular channel led to the formation of a significant amount of the vapor-gas phase in the flow at channel wall temperatures below the saturation point of this mixture. The heat transfer coefficient in the channel with the intensifiers grew 2–5 times compared with those in a smooth channel.
{"title":"Heat Transfer in Circular Channel with Spiral Intensifiers during Circulation of Non-Azeotropic Alcohol-Water Mixture","authors":"V. E. Zhukov, N. N. Mezentseva","doi":"10.1134/s1810232823040069","DOIUrl":"https://doi.org/10.1134/s1810232823040069","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The use of mixtures as refrigerants and heat carriers in various power systems has become widespread. The thermophysical properties of mixtures differ from the properties of their components. This paper presents the results of a study of the intensity of heat transfer to a non-azeotropic alcohol-water mixture with weight concentration of the volatile component of 20% during forced circulation in a heated smooth circular channel, as well as in a channel with spiral intensifiers with a hydrophobic coating. The experiments were carried out on a closed circulation circuit at a pressure in the storage vessel of 0.04–0.055 MPa. The test section was a stainless steel tube with inner diameter of 7.6 mm and wall thickness of 0.2 mm. The heating was provided due to the electric current passed in the tube wall. The spiral intensifiers had winding pitch of 4 mm; the thickness of the PTFE sleeve was 0.9 mm. The experiments were carried out at mass flux rates of 44–46 kg/m<sup>2</sup> and 316 kg/m<sup>2</sup>. The heat flux density varied in the range <span>(1200<q<15200)</span> W/m<sup>2</sup>. The use of the spiral intensifiers with the hydrophobic coating during circulation of the non-azeotropic alcohol-water mixture (20%) in the circular channel led to the formation of a significant amount of the vapor-gas phase in the flow at channel wall temperatures below the saturation point of this mixture. The heat transfer coefficient in the channel with the intensifiers grew 2–5 times compared with those in a smooth channel.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138628368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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