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Experimental study on combined buoyant-thermocapillary flow along with rising liquid film on the surface

Manuel J. GOMES, Ning MEI

《能源前沿（英文）》 2020年 第14卷 第1期   页码 114-126 doi: 10.1007/s11708-017-0483-5

摘要： Temperature distribution and variation with time has been considered in the analysis of the influences of the initial level of immersion of a horizontal metallic mesh tube in the liquid on combined buoyant and thermo-capillary flow. The combined flow occurs along with the rising liquid film flow on the surface of a horizontal metallic mesh tube. Three different levels of immersion of the metallic mesh tube in the liquid have been tested. Experiments of 60 min in duration have been performed using a heating metallic tube with a diameter of 25 mm and a length of 110 mm, sealed outside with a metallic mesh of 178 mm by 178 mm, and distilled water. These reveal two distinct flow patterns. Thermocouples and infrared thermal imager are utilized to measure the temperature. The level of the liquid free surface relative to the lower edge of the tube is measured as angle . The results show that for a smaller angle, or a low level of immersion, with a relatively low heating power, it is possible to near fully combine the upwards buoyant flow with the rising liquid film flow. In this case, the liquid is heated only in the vicinity of the tube, while the liquid away from the flow region experiences small changes in temperature and the system approaches steady conditions. For larger angles, or higher levels of immersion, a different flow pattern is noticed on the liquid free surface and identified as the thermo-capillary (Marangoni) flow. The rising liquid film is also present. The higher levels of immersion cause a high temperature gradient in the liquid free surface region and promote thermal stratification; therefore the system could not approach steady conditions.

关键词： rising liquid film     combined flow     thermo-capillary flow     buoyant flow     metallic mesh tube     horizontal tube    

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Simulation on refrigerant flow in adiabatic capillary tube

WANG Meixia, LIU Cunfang, ZHOU Qiangtai

《机械工程前沿（英文）》 2008年 第3卷 第3期   页码 332-336 doi: 10.1007/s11465-008-0054-x

摘要： This paper proposes a new mathematical model to calculate flow characteristics of the adiabatic capillary tube, which is aimed at solving problems existing in some earlier models. The Stocker’s model was modified with consideration of various effects due to sub-cooling, area concentration, and rolling diameter. The new model can be used not only for R22, but also for its substitutes such as R410A and R407C. A comparison of simulation results of the modified model with those in literature showed that the errors are within 10%. The flow characteristics are finally analyzed.

关键词： mathematical     diameter     literature     sub-cooling     adiabatic capillary    

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Heat transfer and fluid flow analysis of an artificially roughened solar air heater: a CFD based investigation

Anil Singh YADAV,J. L. BHAGORIA

《能源前沿（英文）》 2014年 第8卷 第2期   页码 201-211 doi: 10.1007/s11708-014-0297-7

摘要： In this paper, the effect of rib (circular sectioned) spacing on average Nusselt number and friction factor in an artificially roughened solar air heater (duct aspect ratio, AR= 5:1) is studied by adopting the computational fluid dynamics (CFD) approach. Numerical solutions are obtained using commercial software ANSYS FLUENT v12.1. The computations based on the finite volume method with the semi-implicit method for pressure-linked equations (SIMPLE) algorithm have been conducted. Circular sectioned transverse ribs are applied at the underside of the top of the duct, i.e., on the absorber plate. The rib-height-to-hydraulic diameter ratio ( ) is 0.042. The rib-pitch-to-rib-height ( ) ratios studied are 7.14, 10.71, 14.29 and 17.86. For each rib spacing simulations are executed at six different relevant Reynolds numbers from 3800 to 18000. The thermo-hydraulic performance parameter for = 10.71 is found to be the best for the investigated range of parameters at a Reynolds number of 15000.

关键词： heat transfer     pressure drop     thermo-hydraulic performance parameter    

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Isogeometric analysis of coupled thermo-elastodynamic problems under cyclic thermal shock

Asghar AMANI DASHLEJEH

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 397-405 doi: 10.1007/s11709-018-0473-7

摘要： The isogeometric analysis (IGA) method was extended for the solution of the coupled thermo-elastodynamic equations. The dimensionless formulation was accepted in discretization of the uncoupled and coupled thermoelasticity equations and the Generalized Newmark method was used in the time integration procedure. First, the performance of the proposed method was verified against a two-dimensional benchmark example subjected to constant thermal shock with available exact analytical solutions. Then a two-dimensional half-space benchmark example under thermal shock was solved. Finally, cyclic thermal shock (CTS) loading was applied on the half-space problem. The results dedicated that IGA can be used as a suitable approach in the analysis of the general thermomechanical problems.

关键词： isogeometric analysis     coupled thermo-elastodynamic     dynamic analysis     generalized newmark     cyclic thermal shock    

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Finite element modeling of thermo-active diaphragm walls

Yi RUI, Mei YIN

《结构与土木工程前沿（英文）》 2020年 第14卷 第3期   页码 646-663 doi: 10.1007/s11709-020-0584-9

摘要： There are two major challenges faced by modern society: energy security, and lowering carbon dioxide gas emissions. Thermo-active diaphragm walls have a large potential to remedy one of these problems, since they are a renewable energy technology that uses underground infrastructure as a heat exchange medium. However, extensive research is required to determine the effects of cyclic heating and cooling on their geotechnical and structural performance. In this paper, a series of detailed finite element analyses are carried out to capture the fully coupled thermo-hydro-mechanical response of the ground and diaphragm wall. It is demonstrated that the thermal operation of the diaphragm wall causes changes in soil temperature, thermal expansion/shrinkage of pore water, and total stress applied on the diaphragm wall. These, in turn, cause displacements of the diaphragm wall and variations of the bending moments. However, these effects on the performance of diaphragm wall are not significant. The thermally induced bending strain is mainly governed by the temperature differential and uneven thermal expansion/shrinkage across the wall.

关键词： thermo-active diaphragm wall     finite element analysis     thermo-hydro-mechanical coupling     ground source heat pump    

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Free vibration analysis of functionally graded porous curved nanobeams on elastic foundation in hygro–thermo–magnetic

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 584-605 doi: 10.1007/s11709-023-0916-7

摘要： Herein, a two-node beam element enriched based on the Lagrange and Hermite interpolation function is proposed to solve the governing equation of a functionally graded porous (FGP) curved nanobeam on an elastic foundation in a hygro–thermo–magnetic environment. The material properties of curved nanobeams change continuously along the thickness via a power-law distribution, and the porosity distributions are described by an uneven porosity distribution. The effects of magnetic fields, temperature, and moisture on the curved nanobeam are assumed to result in axial loads and not affect the mechanical properties of the material. The equilibrium equations of the curved nanobeam are derived using Hamilton’s principle based on various beam theories, including the classical theory, first-order shear deformation theory, and higher-order shear deformation theory, and the nonlocal elasticity theory. The accuracy of the proposed method is verified by comparing the results obtained with those of previous reliable studies. Additionally, the effects of different parameters on the free vibration behavior of the FGP curved nanobeams are investigated comprehensively.

关键词： functionally graded porous material     curved nanobeam     hygro–thermo–magnetic     enriched finite element method    

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Simulation and experimental improvement on a small-scale Stirling thermo-acoustic engine

Mao CHEN,Yonglin JU

《能源前沿（英文）》 2016年 第10卷 第1期   页码 37-45 doi: 10.1007/s11708-015-0390-6

摘要： Compared with the traditional engines, the thermo-acoustic engines are relatively new and can act as the linear compressors for refrigerators. Many institutes have shown great interest in this kind of machine for its absence of moving mechanical part. In this paper, the influence of the dimensions of the main parts of the small-scale Stirling thermo-acoustic engine was numerically simulated using a computer code called DeltaEC. The resonator and the resonator cavity were found to be the most convenient and effective in improving the performance of the engine. Based on the numerical simulation, a small-scale Stirling thermo-acoustic engine were constructed and experimentally investigated. Currently, with a resonator length of only 1 m, the working frequency of the engine was decreased to 90 Hz and the onset temperature difference was decreased to 198.2 K.

关键词： thermo-acoustic Stirling engine     small-scale     simulation     experiment    

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Thermo-elastic extended meshfree method for fracture without crack tip enrichment

A. ASADPOUR

《结构与土木工程前沿（英文）》 2015年 第9卷 第4期   页码 441-447 doi: 10.1007/s11709-015-0319-5

摘要： This is the first manuscript presenting an extended meshfree method for thermo- elastic fracture which does not exploit a crack tip enrichment. The crack is modeled by partition of unity enrichment of the displacement and temperature field. Only a step function is employed that facilitates the implementation. To ensure that crack tip is at the correct position, a Lagrange multiplier field ahead of the crack tip is introduced along a line. The Lagrange multiplier nodal parameters are discretised with the available meshfree functions. Two benchmark examples illustrate the efficiency of the method.

关键词： meshfree method     thermo-elasticity    

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A concept of capillary active, dynamic insulation integrated with heating, cooling and ventilation, air

Mark BOMBERG

《结构与土木工程前沿（英文）》 2010年 第4卷 第4期   页码 431-437 doi: 10.1007/s11709-010-0071-9

摘要： When a historic fa?ade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation, one needs to use interior thermal insulation systems. Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges. Yet they may be successfully used and, in many instances, are recommended as a complement to the exterior insulation. This paper presents one of these cases. It is focused on the most successful applications of capillary active, dynamic interior thermal insulation. This happens when such insulation is integrated with heating, cooling and ventilation, air conditioning (HVAC) system. Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations, we propose a next generation, namely, a bio-fiber thermal insulation. When completing the review, this paper proposes a concept of a joint research project to be undertaken by partners from the US (where improvement of indoor climate in exposed coastal areas is needed), China (indoor climate in non-air conditioned concrete buildings is an issue), and Germany (where the bio-fiber technology has been developed).

关键词： capillary active insulation     integrated heating     cooling and ventilation     air conditioning (HVAC) and building enclosure     dynamic insulation     switchable thermal resistance     variable U-value walls    

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Thermo-mechanical simulation of frost heave in saturated soils

《结构与土木工程前沿（英文）》   页码 1400-1412 doi: 10.1007/s11709-023-0990-x

摘要： Roads are exposed to various degradation mechanisms during their lifetime. The pavement deterioration caused by the surrounding environment is particularly severe in winter when the humidity and subfreezing temperatures prevail. Frost heave-induced damage is one of the winter-related pavement deterioration. It occurs when the porewater in the soil is exposed to freezing temperatures. The study of frost heave requires conducting a multiphysics analysis, considering the thermal, mechanical, and hydraulic fields. This paper presents the use of a coupled thermo-mechanical approach to simulate frost heave in saturated soils. A function predicting porosity evolution is implemented to couple the thermal and mechanical field analyses. This function indirectly considers the effect of the water seepage inside the soil. Different frost heave scenarios with uniform and non-uniform boundary conditions are considered to demonstrate the capabilities of the method. The results of the simulations indicate that the thermo-mechanical model captures various processes involved in the frost heave phenomenon, such as water fusion, porosity variation, cryogenic suction force generation, and soil expansion. The characteristics and consequences of each process are determined and discussed separately. Furthermore, the results show that non-uniform thermal boundaries and presence of a culvert inside the soil result in uneven ground surface deformations.

关键词： frost heave     multiphysics analysis     thermo-mechanical approach     saturated soils    

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An extended thermo-mechanically coupled algorithm for simulation of superelasticity and shape memory

S. HASHEMI,H. AHMADIAN,S. MOHAMMADI

《结构与土木工程前沿（英文）》 2015年 第9卷 第4期   页码 466-477 doi: 10.1007/s11709-015-0300-3

摘要： Thermo-mechanical coupling in shape memory alloys is a very complicated phenomenon. The heat generation/absorption during forward/reverse transformation can lead to temperature-dependent variation of its mechanical behavior in the forms of superelasticity and shape memory effect. However, unlike the usual assumption, slow loading rate cannot guarantee an isothermal process. A two-dimensional thermo-mechanically coupled algorithm is proposed based on the original model of Lagoudas to efficiently model both superelasticity and shape memory effects and the influence of various strain rates, aspect ratios and boundary conditions. To implement the coupled model into a finite element code, a numerical staggered algorithm is employed. A number of simulations are performed to verify the proposed approach with available experimental and numerical data and to assess its efficiency in solving complex SMA problems.

关键词： shape memory alloy     thermo-mechanical coupling     superplasticity     shape memory effect    

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Nano thermo-hydrodynamics method for investigating cell membrane fluidity

YANG Yang, LIU Jing

《能源前沿（英文）》 2008年 第2卷 第2期   页码 121-128 doi: 10.1007/s11708-008-0033-2

摘要： As a barrier to compartmentalize cells, membranes form the interface between a cell and its surroundings. The essential function of a membrane is to maintain a relatively stable environment in the cell, exchange substances selectively and transfer energy and information continually from the outside. It is intriguing that above the phase transition temperature, the membrane lipid molecule will have three modes–lateral diffusion, rotational movement and flip-flop activity. These thermodynamic processes are vital to cell existence, growth, division, differentiation and are also responsible for hundreds of thousands of phenomena in life. Previously, species transport across the membrane was interpreted mainly from a phenomenological view using a lumped system model. Therefore, detailed flow processes occurred in the membrane domain and clues related to life mechanism were not sufficiently tackled. Such important issues can be clarified by modeling nano scale thermal hydrodynamics over the gap space of a cell membrane. Previously observed complex membrane behaviors will be shown in this paper and explained by the thermally induced fluidic convections inside the membrane. A correlation between nano scale hydrodynamics, non-equilibrium thermodynamics and cell membrane activities is set up. The disclosed mechanisms are expected to provide a new viewpoint on the interaction between intracellular and extracellular processes through the membrane.

关键词： responsible     phenomenological     phenomena     modes–lateral diffusion     differentiation    

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Available energy analysis of new tandem double-capillary tube refrigeration system for refrigerator-freezers

HE Maogang, ZHANG Ying, SONG Xinzhou, ZHANG Jiantao

《能源前沿（英文）》 2008年 第2卷 第1期   页码 36-42 doi: 10.1007/s11708-008-0013-6

摘要： A new tandem double-capillary tube refrigeration system for refrigerator-freezers is proposed. A capillary tube was added between the two evaporators in the fresh and frozen food storage chests to raise the evaporation temperature of the refrigerating chamber, and reduce the heat exchange temperature difference and the available energy loss. Peng-Robinson (P-R) equation of state was adopted to calculate the thermodynamic properties of the refrigerants, and the available energy analysis of the vapor compression refrigeration cycle was programmed to calculate the thermodynamic performances of the new and the conventional refrigeration cycle of the refrigerator-freezer. The calculation results show that the available energy efficiency of the conventional refrigeration cycle of the refrigerator-freezer is 21.20% and 20.57%, respectively when the refrigerant is R12 and R134a, while that of the double-capillary tube refrigeration cycle of the refrigerator-freezer is 23.97% and 23.44%, respectively. By comparison, the available energy efficiency of the new refrigeration system increases by 13.07% and 13.95%, respectively.
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Effect of graphene and its derivatives on thermo-mechanical properties of phase change materials and

《能源前沿（英文）》 2022年 第16卷 第2期   页码 150-186 doi: 10.1007/s11708-021-0795-3

摘要： Phase change materials (PCMs) play a leading role in overcoming the growing need of advanced thermal management for the storage and release of thermal energy which is to be used for different solar applications. However, the effectiveness of PCMs is greatly affected by their poor thermal conductivity. Therefore, in the present review the progress made in deploying the graphene (Gr) in PCMs in the last decade for providing the solution to the aforementioned inadequacy is presented and discussed in detail. Gr and its derivatives ((Gr oxide (GO), Gr aerogel (GA) and Gr nanoplatelets (GNPs)) based PCMs can improve the thermal conductivity and shape stability, which may be attributed to the extra ordinary thermo-physical properties of Gr. Moreover, it is expected from this review that the advantages and disadvantages of using Gr nanoparticles provide a deep insight and help the researchers in finding out the exact basic properties and finally the applications of Gr can be enhanced.

关键词： phase change materials (PCMs)     graphene     thermal conductivity     characterization    

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Thermo-economic analysis of a direct supercritical CO electric power generation system using geothermal

《能源前沿（英文）》 2022年 第16卷 第2期   页码 246-262 doi: 10.1007/s11708-021-0749-9

摘要： A comprehensive thermo-economic model combining a geothermal heat mining system and a direct supercritical CO2 turbine expansion electric power generation system was proposed in this paper. Assisted by this integrated model, thermo-economic and optimization analyses for the key design parameters of the whole system including the geothermal well pattern and operational conditions were performed to obtain a minimal levelized cost of electricity (LCOE). Specifically, in geothermal heat extraction simulation, an integrated wellbore-reservoir system model (T2Well/ECO2N) was used to generate a database for creating a fast, predictive, and compatible geothermal heat mining model by employing a response surface methodology. A parametric study was conducted to demonstrate the impact of turbine discharge pressure, injection and production well distance, CO2 injection flowrate, CO2 injection temperature, and monitored production well bottom pressure on LCOE, system thermal efficiency, and capital cost. It was found that for a 100 MWe power plant, a minimal LCOE of $0.177/kWh was achieved for a 20-year steady operation without considering CO2 sequestration credit. In addition, when CO2 sequestration credit is $1.00/t, an LCOE breakeven point compared to a conventional geothermal power plant is achieved and a breakpoint for generating electric power generation at no cost was achieved for a sequestration credit of $2.05/t.

关键词： geothermal heat mining     supercritical CO2     power generation     thermo-economic analysis     optimization    

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标题 作者 时间 类型 操作

Experimental study on combined buoyant-thermocapillary flow along with rising liquid film on the surface

Manuel J. GOMES, Ning MEI

期刊论文

Simulation on refrigerant flow in adiabatic capillary tube

WANG Meixia, LIU Cunfang, ZHOU Qiangtai

期刊论文

Heat transfer and fluid flow analysis of an artificially roughened solar air heater: a CFD based investigation

Anil Singh YADAV,J. L. BHAGORIA

期刊论文

Isogeometric analysis of coupled thermo-elastodynamic problems under cyclic thermal shock

Asghar AMANI DASHLEJEH

期刊论文

Finite element modeling of thermo-active diaphragm walls

Yi RUI, Mei YIN

期刊论文

Free vibration analysis of functionally graded porous curved nanobeams on elastic foundation in hygro–thermo–magnetic

期刊论文

Simulation and experimental improvement on a small-scale Stirling thermo-acoustic engine

Mao CHEN,Yonglin JU

期刊论文

Thermo-elastic extended meshfree method for fracture without crack tip enrichment

A. ASADPOUR

期刊论文

A concept of capillary active, dynamic insulation integrated with heating, cooling and ventilation, air

Mark BOMBERG

期刊论文

Thermo-mechanical simulation of frost heave in saturated soils

期刊论文

An extended thermo-mechanically coupled algorithm for simulation of superelasticity and shape memory

S. HASHEMI,H. AHMADIAN,S. MOHAMMADI

期刊论文

Nano thermo-hydrodynamics method for investigating cell membrane fluidity

YANG Yang, LIU Jing

期刊论文

Available energy analysis of new tandem double-capillary tube refrigeration system for refrigerator-freezers

HE Maogang, ZHANG Ying, SONG Xinzhou, ZHANG Jiantao

期刊论文

Effect of graphene and its derivatives on thermo-mechanical properties of phase change materials and

期刊论文

Thermo-economic analysis of a direct supercritical CO electric power generation system using geothermal

期刊论文