Springer Link: https://link.springer.com/journal/11630/29/1
1. The Impingement Heat Transfer Data of Inclined Jet in Cooling Applications: A Review
PAWAR Shashikant, PATEL Devendra Kumar
Corresponding author: PATEL Devendra Kumar
E-mail: devendra21082@gmail.com
Journal of Thermal Science, 2020, 29(1): 1-12.
https://doi.org/10.1007/s11630-019-1200-y
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1200-y
Keywords: heat and fluid flow, jet impingement, Nusselt number, oblique angle
Abstract: On the impingement heat transfer data, the experimental studies of air and liquid jets impingement to the flat surfaces were collected and critically reviewed. The oblique impingements of both single circular and planar slot jets were considered in particular. The review focused on the surface where the jet impingement cooling technique was utilized. The nozzle exit Reynolds numbers based on the hydraulic diameter varied in the range of 1,500–52,000. The oblique angles relative to the plane surface and the dimensionless jet-to-plate spacing vary in the range of 15°–90° and 2–12 respectively. The review suggested that the magnitude of maximum heat transfer shifted more for air jets compared with the liquid jets. The drop in the inclination angle and the jet-to-plate separation led to the increase in the asymmetry of heat transfer distribution. The displacement of maximum Nusselt number (heat transfer) locations was found to be sensitive to the inclination angle and the smaller jet-to-plate distance. Also, the Nusselt number correlations proposed by various researchers were discussed and compared with the results of the cited references.
2. Reduction Kinetics of Fe-based Oxygen Carriers Using Syngas in a Honeycomb Fixed-Bed Reactor for Chemical-Looping Combustion
LIU Xiangyu, ZHANG Hao, HONG Hui
Corresponding author: HONG Hui
E-mail: honghui@iet.cn
Journal of Thermal Science, 2020, 29(1): 13-24.
https://doi.org/10.1007/s11630-020-1255-9
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1255-9
Keywords: chemical-looping combustion, honeycomb reactor, reaction kinetics
Abstract: Chemical-looping combustion (CLC) is considered to be a vital method for utilizing hydrocarbon fuel with low carbon emissions. A honeycomb fixed-bed reactor is a new kind of reactor for CLC. However, the further application of the reactor is limited by the inadequacy of the kinetic equations for CLC. In this paper, the experimental studies on the kinetic of Fe-based oxygen carriers were carried out by the CLC experiments using syngas which was obtained from one typical type of coal gasification products. The experimental results show that there were two individual stages for the kinetic characteristics during the fuel reaction process. Therefore, the CLC fuel reaction process could be described by a two-stage unreacted-core shrinking model and the reaction rate equations for each of the two phases were provided. In both stages, the dominant resistances were analyzed. The activation energy and the reaction order in both stages were calculated respectively as well. Comparing the experimental results of reaction rate with the calculated results of the obtained rate equations, it could be clearly seen that the reaction kinetics model was appropriate for the CLC in the honeycomb reactor. This work is expected to provide a guideline for the future development and industrial design of the honeycomb CLC reactors from the perspective of kinetics.
3. Material Compatibility of Hexamethyldisiloxane as Organic Rankine Cycle Working Fluids at High Temperatures
DAI Xiaoye, SHI Lin, QIAN Weizhong
Corresponding author: SHI Lin
E-mail: rnxsl@mail.tsinghua.edu.cn
Journal of Thermal Science, 2020, 29(1): 25-31.
https://doi.org/10.1007/s11630-019-1147-z
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1147-z
Keywords: organic Rankine cycle (ORC), material compatibility, high temperatures, hexamethyldisiloxane (MM)
Abstract: The organic Rankine cycle (ORC) is a promising technology for industrial waste heat recovery and renewable energy utilization. High temperature ORCs have attracted particular interest because of their high thermal efficiencies and outputs. The material compatibility of working fluid is a significant limitation for the working fluid selection and system design for high temperature ORCs. This work presents a method for studying the material compatibility of ORC working fluids based on the calculated conditions of the ORCs and matching of components, temperatures, and materials. Hexamethyldisiloxane (MM) was chosen as the test fluid. The experimental results show that 304 stainless steel has better compatibility with MM than copper as the material of evaporators. Fluoric rubber is not a suitable sealing material for high temperature ORCs with MM as the working fluids because of the bad compatibility. Mineral oil has better compatibility with MM than polyol ester (POE) lubricant as the lubricant for the fluid pump.
4. Design and Analysis of a Single-Stage Transonic Centrifugal Turbine for organic Rankine cycle (ORC)
WANG Naian, SUN Xiaojin, HUANG Diangui
Corresponding author: HUANG Diangui
E-mail: dghuang@usst.edu.cn
Journal of Thermal Science, 2020, 29(1): 32-42.
https://doi.org/10.1007/s11630-019-1079-7
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1079-7
Keywords: ORC, transonic centrifugal turbine, design and off-design operating conditions, performance analysis, computational fluid dynamics
Abstract: The recovery of low temperature heat sources is a hot topic in the world. The ORC system can effectively use the low temperature heat source. As its main output device, the performance of the turbine is very important. The single stage transonic turbine has the characteristics of small size and large output power. In this paper, the complete design process of a transonic centrifugal turbine with R245fa in low working temperature condition is introduced. At the design conditions, the shaft power and the wheel efficiency of the centrifugal turbine can reach 1.12 MW and 83.61%, respectively. In addition, a thermodynamic ORC cycle is presented and the off-design conditions of the turbine and its influence on the system are studied in detail. The results obtained in the present work show that the single-stage transonic centrifugal turbine can be regarded as a potential choice to be applied in small scale ORC systems.
5. Experimental Investigations of the Flow Field Structure and Interactions between Sectors of a Double-Swirl Low-Emission Combustor
FAN Xiongjie, XU Gang, LIU Cunxi, WANG Jianchen, LIN Yuzhen, ZHANG Chi
Corresponding author: LIU Cunxi
E-mail: liucunxi@iet.cn
Journal of Thermal Science, 2020, 29(1): 43-51.
https://doi.org/10.1007/s11630-019-1175-8
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1175-8
Keywords: combustor, recirculation zone, Particle Imaging Velocimetry (PIV), pressure drop
Abstract: In this paper, the flow field characteristics of a double-swirl low-emission combustor were analyzed by using Particle Imaging Velocimetry (PIV) technology in an optical three-sector combustor test rig. The interactions between sectors and the flow field structure were explained. The results illustrated that there was a big difference between the flow field structures of the middle sector and the side sector under the same pressure drop, which was mainly induced by the interactions between sectors. The interactions made the swirl intensity of the middle sector weaker than that of the side sector, which made the recirculation zone of the middle sector be smaller than that of the side sector. With the increase of swirler pressure drop, the jet velocity at the exit of the swirler, the jet expansion angle, the width of the recirculation zone and the recirculating speed of the central axis became larger, enhancing the interactions between air streams from middle sector and side sector. The flow velocity in the central plane between sectors was small, especially the radial velocity, mainly because of the loss of the swirl intensity by the interactions between flow field of adjacent sectors. The expansion angle determined the position of the vortex in the primary recirculation zone; the axial and radial position of the vortex move downstream and radial outward with the increase of the jet expansion angle. The results of the mechanism of flow field organization in this study can be used to support the design of new low-emission combustor.
6. Study on the Effects of Dome Fuel Distribution Ratio on Lean Blowout of a Model Combustor
SHEN Xiaoming, YUAN Yixiang, ZENG Detang, XIE Pengfu, TAN Chunqing
Corresponding author: YUAN Yixiang
E-mail: yuanyx@iet.cn
Journal of Thermal Science, 2020, 29(1): 52-57.
https://doi.org/10.1007/s11630-019-1146-0
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1146-0
Keywords: combustor, dome fuel distribution ratio, lean blowout, pressure fluctuation
Abstract: The experimental studies and numerical simulation were conducted on the effects of the dome fuel distribution ratio on the lean blowout of a model combustor. The experimental results indicate that as the key parameter, the dome fuel distribution ratio, increases from 2.06% to 16.67%, the lean blowout equivalence ratio declines obviously at the beginning, and then the decrease slows down, in addition, the amplitude of the pressure fluctuation in the combustor reduces significantly while the dominant frequency keeps basically constant. In order to analyze the experimental results, the numerical simulation is adopted. The temperature and local equivalence ratio distributions are employed to explain the reasonwhy the lean blowout performance improves with the increase of the dome fuel distribution ratio.
7. Influence of Turbulence Schmidt Number on Exit Temperature Distribution of an Annular Gas Turbine Combustor using Flamelet Generated Manifold
WANG Weihao, YANG Songlin, GAO Chuang, HUANG Weiguang
Corresponding author: WANG Weihao, GAO Chuang
E-mail: wangwh@sari.ac.cn, gaoc@sari.ac.cn
Journal of Thermal Science, 2020, 29(1): 58-68.
https://doi.org/10.1007/s11630-019-1248-8
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1248-8
Keywords: gas turbine combustor, flamelet-generated manifold, turbulent Schmidt Number, Reynolds Stress Model, Reynolds analogy
Abstract: The Reynolds analogy concept has been used in almost all turbulent reacting flow RANS (Reynolds-averaged Navier-Stokes) simulations, where the turbulence scalar transfers in flow fields are calculated based on the modeled turbulence momentum transfer. This concept, applied to a lean premixed combustion system, was assessed in this paper in terms of exit temperature distribution. Because of the isotropic assumption involved in this analogy, the prediction in some flow condition, such as jet cross flow mixing, would be inaccurate. In this study, using Flamelet Generated Manifold as reaction model, some of the numerical results, obtained from an annular combustor configuration with the turbulent Schmidt number varying from 0.85 to 0.2, were presented and compared with a benchmark atmospheric test results. It was found that the Schmidt number σt in mean mass fraction f transport equation had significant effect on dilution air mixing process. The mixing between dilution air and reaction products from the primary zone obviously improved as σt decreased on the combustor exit surface. Meanwhile, the sensitivity of σt in three turbulence models including Realizable k-ε, SST (Shear Stress Transport) and RSM (Reynolds Stress Model) has been compared as well. Since the calculation method of eddy viscosity was different within these three models, RSM was proved to be less sensitive than another two models and can guarantee the best prediction of mixing process condition. On the other hand, the results of dilution air mixing were almost independent of Schmidt number Sct in progress variable c transport equation. This study suggested that for accurate prediction of combustor exit temperature distribution in steady state reacting flow simulation, the turbulent Schmidt number in steady state simulation should be modified to cater to dilution air mixing process.
8. Investigations on Emission Characteristics of a Liquid-Fueled Trapped Vortex Combustor
WU Zejun, HE Xiaomin
Corresponding author: WU Zejun, HE Xiaomin
E-mail: wuzejun@cqu.edu.cn, hxm@nuaa.edu.cn
Journal of Thermal Science, 2020, 29(1): 69-80.
https://doi.org/10.1007/s11630-019-1232-3
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1232-3
Keywords: trapped vortex combustor, gas pollutant emissions, atomization, turbulence intensity, residence time
Abstract: The combustion and emission formation process of liquid fuel in the trapped vortex combustor (TVC) are very complicated. A trapped vortex combustor with replaceable bluff-bodies was designed to investigate these processes. The bluff-body widths varied from 0.021 m to 0.036 m. Experimental tests were carried out. Liquid RP-3 aviation kerosene was used in the tests. Emissions were measured under atmospheric pressure. The combustion process was analyzed theoretically in the viewpoints of relative evaporation time, mixing time and reaction time. Numerical simulations were also conducted to help analyze the formation and depletion processes of pollutants in TVC. The results reveal that atomization was a critical factor for formation and depletion processes of pollutants. By controlling mixing speed of burned and unburned gases and thus fuel-air uniformity, turbulence intensity could also affect emission levels. In addition, residence time also affected the emissions by affecting combustion completeness and the time for NOx formation. All these factors were combined in a complicated way to affect combustion process and pollutant emissions.
9. Analysis of Porosity and Preheating Temperature on the Decomposition and Combustion Characteristics within 5 N Ammonium Dinitramide (ADN)-based Monopropellant Thruster
ZHANG Tao, WANG Fengshan, CHEN Jun
Corresponding author: ZHANG Tao, CHEN Jun
E-mail: tzhang903@163.com, ortcj@126.com
Journal of Thermal Science, 2020, 29(1): 81-89.
https://doi.org/10.1007/s11630-020-1257-7
Springer Link: https://link.springer.com/article/10.1007/s11630-020-1257-7
Keywords: porosity, preheating temperature, decomposition and combustion characteristics, ammonium dinitramide, monopropellant
Abstract: In this study, the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5 N ammonium dinitramide (ADN)-based thruster were numerically investigated in terms of the distribution of components, temperature, and pressure. The results indicated that the porosity of the fore-catalytic bed and preheating temperature significantly affected the decomposition and combustion characteristics. The porosity of the fore-catalytic bed was optimized, and the thrust performance was demonstrated to improve with increasing of porosity of the after-catalytic bed and pre-heating temperature. The results were favorable for the investigation of decomposition and combustion characteristics and could also be beneficial to the design and manufacture of different types of ADN-based thrusters.
10. Numerical Study on the Morphology of a Re-Ignited Laminar Partially Premixed Flame with a Co-Axial Pilot Flame
WU Zejun, KANG Yinhu, HE Xiaomin
Corresponding author: WU Zejun, KANG Yinhu
E-mail: wuzejun@cqu.edu.cn, cqukangyh@cqu.edu.cn
Journal of Thermal Science, 2020, 29(1): 90-97.
https://doi.org/10.1007/s11630-019-1249-7
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1249-7
Keywords: re-ignited flame, partially premixed flame, flame morphology, numerical simulation
Abstract: Re-ignited partially premixed flame (PPF) is a quite extensive flame type in real applications, which is directly relevant to the local and global extinction and re-ignition phenomenon. The authors designed a model burner to establish laminar re-ignited PPFs. Numerical simulations were carried out to reveal the morphology of laminar reignited PPF. Based on the distributions of temperature, heat release and radicals, the morphologies of re-ignited flames were explored. W-shaped flames were formed under pilot-lean conditions. Line-shaped and y-shaped flames were formed under pilot-rich conditions. Both w-shaped and y-shaped flames had a triple-flame structure. The re-ignited flames can stand beyond the rich flammability limit. Additionally, OH distributions indicated both pilot flame and re-ignited flame well as it rapidly increased near the flame front. OH concentration did not increase visibly while CH2O concentration mildly increased during the mild re-ignition process in the pre-zone of the re-ignited PPF. According to the results of 0-D simulations using closed homogeneous reactor, both OH and CH2O reduced ignition time significantly. The results of this work are helpful for understanding re-ignited PPF more closely.
11. Combustion Wave Propagation of a Modular Porous Burner with Annular Heat Recirculation
SONG Fuqiang, WEN Zhi, FANG Yuan, WANG Enyu, LIU Xunliang
Corresponding author: LIU Xunliang, WANG Enyu
E-mail: liuxl@me.ustb.edu.cn, wey@hebut.edu.cn
Journal of Thermal Science, 2020, 29(1): 98-107.
https://doi.org/10.1007/s11630-019-1162-0
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1162-0
Keywords: flashback, start-up, modular porous burner, heat recirculation
Abstract: A numerical investigation of the different arrangements of porous media in a combustor with annular heat recirculation is conducted. The effect of annular heat recirculation and porous block arrangement on the characteristics of combustion wave propagation is numerically studied. Results show that power input, heat capacity of porous matrix, arrangement of porous blocks, and annular heat recirculation are major factors that influence the propagation of combustion wave. The overall temperature of ceramic porous burner is higher than that of ceramic-metal type burner due to the lower heat storage capacity of the former, especially for the temperature downstream. The flame temperature is higher upstream and lower downstream with metal foams in the annulus than that without metal foams. The flame temperature of uniformity type burner is more uniform than that of gradually-varied and modular type burners. The flame front moves more slowly with metal foams in the annulus than that without metal foams due to the better preheating effect of metal foams. The flame position moves downstream, and the flame temperature gradually decreases and is eventually extinguished due to the low preheating temperature.
12. Chemical Synthesis Residual Pyrolysis and Combustion: Kinetics and Evolved Gases Investigated by TG-FTIR
FANG Chunqi, JIANG Xuguang, LV Guojun, YAN Jianhua, LIN Xuliang, SONG Huibo, CAO Junjun
Corresponding author: JIANG Xuguang
E-mail: jiangxg@zju.edu.cn
Journal of Thermal Science, 2020, 29(1): 108-114.
https://doi.org/10.1007/s11630-019-1140-6
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1140-6
Keywords: chemical synthesis residual, pyrolysis, combustion, TG-FTIR, evolution
Abstract: Chemical synthetic residual is one of the solid wastes generated from pharmaceutical industry. The pyrolysis and combustion characteristics of chemical synthesis residual were investigated using a thermogravimetricanalyser coupled with Fourier transform infrared spectroscopy (TG-FTIR) in this study. The processes of pyrolysis and combustion can be divided into three stages. The average weight loss rate of pyrolysis process at low temperature was higher than that of combustion. The kinetic parameters of chemical synthesis residual during pyrolysis and combustion were calculated based on the TG results. Acetic acid and 4-aminophenol were the main evolved matter observed in the pyrolysis process. The emission characteristics of combustion at low temperature were similar to that of the pyrolysis, while CO2 was found as the major gaseous product at high temperature. A high temperature about 850°C is needed to make sure the complete combustion of chemical synthesis residual.
13. Sub-Atmospheric Pressure Coupled with Width Effect on Downward Flame Spread over Energy Conservation Material Polyurethane Foam
MA Xin, TU Ran, CHENG Xudong, ZHU Shuguang, SUN Qiang, FANG Tingyong
Corresponding authors: TU Ran, FANG Tingyong
E-mails: turan@hqu.edu.cn, fangty@ustc.edu.cn
Journal of Thermal Science, 2020, 29(1): 115-121.
https://doi.org/10.1007/s11630-019-1077-9
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1077-9
Keywords: rigid polyurethane, low air pressure, building facade, energy conservation, heat transfer
Abstract: Rigid polyurethane (PUR) foam, a sustainable thermosetting building facade porous polymer material, has been widely applied in the construction industry for energy conservation. Additional knowledge of the fire safety performance of PUR foam at different altitudes and sample widths is required. Comparative lab-scale experiments were conducted in the Lhasa plateau (66.5 kPa) and the Hefei plain (99.8 kPa) in China. Flame propagation characteristics (average flame spread rate and flame height) were measured at different widths and atmospheric pressures of the test locations. Experimental results show that the dependence of dimensionless flame heights on sample width shows negative power law relationships with index of ?w/5.4 to ?w/5.8. Both flame height and flame spread rate were lower under low ambient pressure conditions as and. Flame spread rate decreased with increasing sample width in the convection regime before a critical width of 4 cm – 8 cm, after which the flame spread rate increased in the radiation regime. Results of this study contribute to the science of combustion, fire safety and energy conservation, and provide a basis for fire safety protocols for historical heritage buildings in the Lhasa plateau.
14.Design and Thermal Analysis of the Large Fire Door for AP1000 Nuclear Reactor
ZHANG Shanwen, LI Chong, MIAO Hong, ZHANG Jianfeng, ZHANG Haijun
Corresponding author: ZHANG Jianfeng
E-mail: zhangjf@yzu.edu.cn
Journal of Thermal Science, 2020, 29(1): 122-130.
https://doi.org/10.1007/s11630-019-1138-0
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1138-0
Keywords: large fire door, AP1000, nuclear reactor, design, thermal analysis
Abstract: The large fire door is the key component to ensure the effectiveness of fire zone in AP1000 nuclear reactor. According to the fire design requirements and design criteria, the global structure of the large fire door is designed. Based on the designed structure, the thermal mathematical model of the large fire door is established. Based on the solid heat transfer theory, the multi-layer heat transfer theory and integrated heat transfer theory, the differential equations of heat conduction, initial conditions, and boundary conditions are determined. Thermal analysis for the fire door leaf and the closure is carried out by using the method of numerical simulation. Results show that: considering the thermal load, the whole structure of the large fire door can meet the fire resistance limit of 3 hours and the design is reasonable and feasible. This study provides theory basis for the design of the large fire door.
15. An Improved Heat Transfer Correlation for Supercritical Aviation Kerosene Flowing Upward and Downward in Vertical Tubes
LI Yong, CHEN Youqian, ZHANG Yingchun, SUN Feng, XIE Gongnan
Corresponding author: XIE Gongnan
E-mail: xgn@nwpu.edu.cn
Journal of Thermal Science, 2020, 29(1): 131-143.
https://doi.org/10.1007/s11630-019-1197-2
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1197-2
Keywords: correlation, supercritical n-decane, prediction accuracy, heat flux, vertical tube
Abstract: Correlations are crucial to the design of cooling channels employed in regenerative cooling systems for scramjets. In this paper, correlations for the aviation kerosene flowing upward and downward in vertical tubes are studied and discussed. Four existing correlations are assessed against the available experimental data. To further improve the prediction accuracy of the heat transfer behaviors of the supercritical aviation kerosene, a new dimensionless parameter (Qi) relevant to the heat flux is proposed and introduced into the construction of a new correlation. Verification shows that the new correlation is more accurate than existing correlations.
16. A High Order Control Volume Finite Element Method for Transient Heat Conduction Analysis of Multilayer Functionally Graded Materials with Mixed Grids
LIU Qi, MING Pingjian, ZHAO Haiyang, ZHANG Wenping
Corresponding author: MING Pingjian
E-mail: pingjianming@hrbeu.edu.cn
Journal of Thermal Science, 2020, 29(1): 144-158.
https://doi.org/10.1007/s11630-019-1167-8
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1167-8
Keywords: finite volume method, functionally graded materials, transient heat conduction
Abstract: This paper describes a new two-dimensional (2-D) control volume finite element method (CV-FEM) for transient heat conduction in multilayer functionally graded materials (FGMs). To deal with the mixed-grid problem, 9-node quadrilateral grids and 6-node triangular grids are used. The unknown temperature and material properties are stored at the node. By using quadratic triangular grids and quadratic quadrilateral grids, the present method offers greater geometric flexibility and the potential for higher accuracy than the linear CV-FEM. The properties of the FGMs are described by exponential, quadratic and trigonometric grading functions. Some numerical tests are studied to demonstrate the performance of the developed method. First, the present CV-FEM with mixed high-order girds provides a higher accuracy than the linear CV-FEM based on the same grid size. Second, the material properties defined location is proved to have a significant effect on the accuracy of the numerical results. Third, the present method provides better numerical solutions than the conventional FEM for the FGMs in conjunction with course high-order grids. Finally, the present method is also capable of analysis of transient heat conduction in multilayer FGM.
17. Thermal Conductivity of Low-Density Polyethylene Foams Part II: Deep Investigation using Response Surface Methodology
HASANZADEH Rezgar, AZDAST Taher, DONIAVI Ali
Corresponding author: AZDAST Taher
E-mail: t.azdast@urmia.ac.ir
Journal of Thermal Science, 2020, 29(1): 159-168.
https://doi.org/10.1007/s11630-019-1240-3
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1240-3
Keywords: thermal insulation, polymer, foams, response surface methodology
Abstract: Here, we conducted a deep study on the thermal insulation performance of polymeric foams using response surface methodology (RSM). Cell size, foam density, and cell wall thickness were considered as variable parameters. Analysis of variance (ANOVA) tool was utilized to recognize the effective parameters on the different mechanisms of heat transfer. Regression models were presented to forecast the different mechanisms of heat transfer and their validities were checked using ANOVA tool as well as compared to the thermal conductivity results. Surface plots were used to study the interaction effect of significant parameters. The optimization procedure was performed using RSM. Foam density and cell wall thickness are effective parameters on the solid thermal conductivity whereas cell size and foam density were significant parameters on the thermal radiation. By decreasing foam density, gaseous thermal conductivity and thermal radiation were increased and solid thermal conductivity was reduced. The regression model predicted the overall thermal conductivity with an average error smaller than 3%. The results illuminated that the overall thermal conductivity in the optimum conditions was as small as 29 mW/mK.
18. Heat Transfer Analysis of MHD Power Law Nano Fluid Flow through Annular Sector Duct
AHMED Farhan, IQBAL Mazhar
Corresponding author: AHMED Farhan
E-mail: fahmed_math@yahoo.com
Journal of Thermal Science, 2020, 29(1): 169-181.
https://doi.org/10.1007/s11630-019-1126-4
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1126-4
Keywords: electrically conducting power law nano fluid, Cu nano particles, TiO2 nano particles, shear thickening fluid, shear thinning fluid, heat transfer rate, friction factor
Abstract: Flow and heat transfer analysis of an electrically conducting MHD power law nano fluid is carried out through annular sector duct, under the influence of constant pressure gradient. Two types of nano particles (i.e. Cu and TiO2) are used in power law nano fluid. Strongly implicit procedure, (SIP) is used to simulate the discretized coupled algebraic equations. It has been observed that volume fraction of nano particles, ? and magnetic field parameter, Ha are favourable for the heat transfer rate, however, both resist the fluid flow. Impact of applied uniform transverse magnetic field exceeds in the case of shear thickening fluids (i.e. n>1) by increasing the value of Ha as compared to that in shear thinning fluids (i.e. n<1). Therefore, enhancement in heat transfer rate is comparably more in shear thickening fluid. Furthermore, comparable limiting case study with published result is also carried out in this research paper.
19. Heat Transfer and Thermal Characteristics Effects on Moving Plate Impinging from Cu-Water Nanofluid Jet
DATTA Abanti, KUMAR Sonal, HALDER Pabitra
Corresponding author: DATTA Abanti
E-mail: abanti.datta@gmail.com
Journal of Thermal Science, 2020, 29(1): 182-193.
https://doi.org/10.1007/s11630-019-1107-7
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1107-7
Keywords: Cu-water nanofluid, multiphase, mixture model, moving plate, jet impingement, CFD
Abstract: The present article is focused on modelling of flow and heat transfer behaviour of Cu-water nanofluid in a confined slot jet impingement on hot moving plate. Different parameters such as various moving plate velocities, nanoparticles at various concentrations, variation in turbulent Reynolds number and jet nozzle to plate distance have been considered to study the flow field and convective heat transfer performance of the system. Results of distribution of local and average Nusselt number and skin friction coefficients at the plate surface are shown to elucidate the heat transfer and fluid flow process. Qualitative analysis of both stream function and isotherm contours are carried out to perceive the flow pattern and heat transfer mechanism due to moving plate. The results revealed that average Nusselt number significantly rises with plate velocity in addition with jet inlet Reynolds number. Correlations of the average Nusselt numbers are presented.
20. Study on Temperature Distribution of Perforated Horizontal Wellbore
ZHANG Xingkai, JIANG Ziheng, LIAO Ruiquan, SHI Baocheng, WU Lijuan, LIU Kai, ZHANG Yindi
Corresponding author: LIAO Ruiquan
E-mail: liaoruiquan@263.net
Journal of Thermal Science, 2020, 29(1): 194-205.
https://doi.org/10.1007/s11630-019-1247-9
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1247-9
Keywords: horizontal well simulation experiment, perforation, Joule-Thomson effect, temperature distribution
Abstract: The temperature distribution in the wellbore under different conditions was studied by using a designed horizontal well simulation experimental device. The experimental results showed that the Joule-Thomson effect was significant in perforated wellbore. When the opening mode was the same, the larger the gas flow rate, the lower the temperature in the wellbore. Furthermore, with the increase of liquid volume, the temperature drop effect decreased gradually. The more uniform the perforation distribution, the smaller the temperature change in the wellbore. With the increase of liquid volume, the influence of gas flow rate on temperature distribution decreased. The temperature gradient caused by Joule-Thomson effect decreased with the increase of wellbore holdup. At the same time, the experimental results were compared with the theoretical values. It was found that the error of the model was within 4%, which showed the reliability of predictions of the model.
21. Thermal Performance Prediction in the Air Gap of a Rotor-Stator Configuration: Effects of Numerical Models
DANG Dinh-Dong, PHAM Xuan-Tan, NGUYEN Chi-Cong
Corresponding author: DANG Dinh-Dong
E-mail: dinh-dong.dang.1@ens.etsmtl.ca
Journal of Thermal Science, 2020, 29(1): 206-218.
https://doi.org/10.1007/s11630-019-1096-6
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1096-6
Keywords: hydro-generators, electrical cooling, mixing plane, windage loss, conjugate heat transfer
Abstract: This study is dedicated to a numerical investigation of convective heat transfer on the rotor surfaces of a rotor-stator configuration that is typically found in large hydro-generators. The computational fluid dynamics calculations with two turbulence modelling approaches are used to predict the flow structure and heat transfer in the air gap of the rotor-stator configuration. The steady state mixing plane approach is employed at the interface to couple the rotor and stator components. Results show that the location of mixing plane interface in the air gap plays an important role in the prediction of heat transfer on the pole face. Also, it is indicated that the prediction of temperature distribution on the pole face is greatly affected by the turbulence models used. Furthermore, through a comparison between the pure convective and conjugate heat transfer methodologies, it is shown that the inclusion of solid domain into the numerical model significantly improves the thermal prediction of the solid components of the machine.
22. Numerical Study of the Air Bleeding Caused Non-Uniformity in Axial Compressor
CHEN Shaowen, GONG Yun, LI Weihang, WANG Songtao, WANG Zhongqi
Corresponding author: CHEN Shaowen
E-mail: cswemail@hit.edu.cn
Journal of Thermal Science, 2020, 29(1): 219-231.
https://doi.org/10.1007/s11630-019-1074-z
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1074-z
Keywords: compressor bleeding, multi-passage calculation, non-uniformity, axial compressor
Abstract: Bleeding in the compressor is getting more and more attractive because the increasing demand of bleeding rate as the temperature of the first stage of turbine gets higher and needs more cooling air. Though plenty of work has been done about bleeding, however, most of the work is studied with a single passage or ignoring the real structure of the bleeding system. In the present study, multi-passage calculation was used through ANSYS CFX to consider the finite duct holes in the whole blade row, and the effect of the axial location of bleeding slot on the non-uniformity of the blade passage was investigated, and the non-uniform could maintain a low level when bleeding at the front part of the blade passage and the non-uniformity would become large when moving the bleeding slot much further downstream. Afterward, the air bleeding mass flow rate was studied. It’s found that the non-uniformity of air bleeding mass flow is small when bleeding at a low mass flow rate in each passage and results in relatively uniform flow field in the passage. However, the non-uniformity increases significantly as the bleeding mass flow rate increases. Some flow field details were also given to study how the flow field changes when bleeding non-uniformly.
23. Theoretical and Experimental Studies for the Transient Response of Cavity
HU Jianping, LIU Zhenxia, ZHU Pengfei, LYU Yaguo
Corresponding author: LIU Zhenxia
E-mail: zxliu@nwpu.edu.cn
Journal of Thermal Science, 2020, 29(1): 232-240.
https://doi.org/10.1007/s11630-019-1189-2
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1189-2
Keywords: secondary air system, static cavity, rotating cavity, transient response, experiment
Abstract: During the transient state of aero-engine, cavity has evidently transient characteristics in the secondary air system. To investigate transient characteristics, theoretical and experimental studies were implemented for both static and rotating cavities. First of all, the typical transient response phenomena in secondary air system were investigated based on the basic concepts of the dynamic process. According to the basic theory of gas dynamics, the causes of transient phenomena were analyzed in two aspects, external disturbance, and system physical properties. Several dimensionless parameters were introduced to analyze the transient response characteristics of air system. Second, the experimental results of the static cavity indicated that the actual response time increased with the increase of the inlet pressure. The experimental results of the rotor-stator cavity showed that the low rotational speed on the response process had little effect, and the response time gradually increased when the speed continued to increase. Third, the test results of multiple components suggested that when the valve was opening the inlet pressure of the static cavity increased quickly and then reached a stable value, but the pressure of the static cavity, stable pressure cavity and rotor-stator chamber rose gradually. It was also obtained the actual response time of them was increased. The closer the measuring points were to the disturbance source, the shorter the delay time was.
24. Experimental Optimization of Jet Self-Priming Centrifugal Pump Based on Orthogonal Design and Grey-Correlational Method
CHANG Hao, SHI Weidong, LI Wei, WANG Chuan, ZHOU Ling, LIU Jianrui, YANG Yongfei, RAMESH K. Agarwal
Corresponding author: SHI Weidong, WANG Chuan
E-mail: wdshi2012@126.com, wangchuan@ujs.edu.cn
Journal of Thermal Science, 2020, 29(1): 241-250.
https://doi.org/10.1007/s11630-019-1160-2
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1160-2
Keywords: self-priming centrifugal pump, design, optimization, orthogonal experiment, grey-correlational
Abstract: The novel jet self-priming centrifugal pump, as important modern irrigation equipment, is widely used in large-scale irrigation, mine drainage and so on. In order to improve the profile streamline of blade, the inlet shape of impeller was designed as distorted and the outlet shape as cylindrical, which can not only improve the pump efficiency, but also shorten the self-priming time. Further, the novel jet self-priming system was proposed, by employing the jet nozzle and check valve to improve the velocity of self-priming. Meanwhile, nine different structure jet nozzles were designed based on the orthogonal design method, and the relevant self-priming experiments were performed on I level accuracy test bench in Jiangsu University. According to the grey- correlational analysis, the influence of the nozzle geometry parameters on the self-priming performance was obtained. The relationship between self-priming time and self-priming height was discussed. The test results showed that the hydraulic design of jet self-priming centrifugal pump was reasonable; all indicators met the Chinese national standard; the head reached 21.04 m and efficiency was 72.8% under the design flow condition. What is more, the self-priming performance was obviously improved by adjusting the geometrical parameters of nozzle. When the height of the self-priming process was 5.3 m, the self-priming time reached 62 s, which was much shorter than the national standard. Therefore, this research could provide reference for designing the structure of jet self-priming centrifugal pump.
25. Linear Stability Analysis of Thermocapillary Flow in Rotating Shallow Pools Heated from Inner Wall
TIAN Zu-an, ZENG Zhong, LIU Hao, YIN Linmao, ZHANG Liangqi, QIAO Long
Corresponding author: ZENG Zhong
E-mail: zzeng@cqu.edu.cn
Journal of Thermal Science, 2020, 29(1): 251-259.
https://doi.org/10.1007/s11630-019-1156-y
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1156-y
Keywords: annular pool, thermocapillary flow instability, spectral element method, linear stability analysis
Abstract: Thermocapillary flow of silicon melt (Pr=0.011) in shallow annular pool heated from inner wall was simulated at the dimensionless rotation rate w ranging from 0 to 7000. The effect of pool rotation on the stability of the thermocapillary flow was investigated. The steady axisymmetric basic state was solved by using the spectral element method; the critical stability parameters were determined by linear stability analysis; the mechanism of the flow instability was explored by the analysis of energy balance. A stability diagram, exhibiting the variation of the critical Marangoni number versus the dimensionless rotation rate w was presented. The results reveal that only one Hopf bifurcation point appeared in the intervals of ω<3020 and ω>3965, and the corresponding instability was caused by the shear energy, which was provided by the thermocapillary force and pool rotation, respectively. In addition, the competition between thermocapillary force and pool rotation leads to three Hopf bifurcation points in the range of 3020<ω<3965 with the increase of Marangoni number.
26. Analytical Solution of Thermocapillary Flow in Cylindrical Annuli with Curved Free Surface
LIU Jia, PENG Lan
Corresponding author: LIU Jia
E-mail: liujialj@cqu.edu.cn
Journal of Thermal Science, 2020, 29(1): 260-267.
https://doi.org/10.1007/s11630-019-1120-x
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1120-x
Keywords: thermocapillary flow, analytical solution, interface deformation
Abstract: In this paper we consider thermocapillary flow with interface deformation in cylindrical annuli subjected to lateral temperature gradient. Based on the assumption that Reynolds, Marangoni and capillary numbers are very small, we expanded the governing equations in terms of a small parameter, and the zeroth-order one is the Stokes problem, which can be analytically solved by use of separation of variables formulation. Solutions are obtained for the zeroth-order fluid and thermal fields as well as the first-order interfacial shapes. Streamlines, temperature distributions and interface shapes are presented and the influence of aspect ratios is investigated.
27. Experimental and Numerical Studies on the Diffusion of CO2 from Oil to Water
LI Binfei, ZHANG Qiliang, CAO Aiqing, BAI Hao, XU Jianguo
Corresponding author: LI Binfei
E-mail: libinfei@upc.edu.cn
Journal of Thermal Science, 2020, 29(1): 268-278.
https://doi.org/10.1007/s11630-019-1117-5
Springer Link: https://link.springer.com/article/10.1007/s11630-019-1117-5
Keywords: CO2-oil-water system, CO2 diffusion, mass transfer, pressure decay method, numerical method
Abstract: Injecting CO2 into oil reservoirs can improve the oil recovery, meanwhile achieve CO2 storage. The diffusion of CO2 in oil-water systems has a substantial impact on this process. The interface significantly affects the mass transfer of CO2 between oil and water phase. In this paper, based on the determination of the CO2 diffusion coefficient in oil or water phases, the diffusion processes of CO2 from oil to water were experimentally investigated under different pressures. A numerical method was proposed to calculate the pressure drop and the diffusion coefficient in the process of CO2 diffusion from oil to water. The experimental results indicated that the CO2 diffusion coefficient in oil or water increased rapidly with pressure up to the critical pressure of CO2 and gradually slowed down thereafter. The CO2 diffusion from oil to water was much slower than that in oil or water. The diffusion coefficient of CO2 from oil to water was one magnitude lower than that in the single liquid phase of oil or water, and the effect of pressure was not significant. Based on the diffusion coefficient of CO2 in a single liquid phase and the proposed numerical method, the pressure drop and the numerical diffusion coefficient in the process of CO2 diffusion from oil to water were calculated. The relative errors between the experimental and numerical results were within 9%. Therefore, the numerical method proposed herein can be used to predict the diffusion process of CO2 from oil to water and the diffusion coefficient associated with this process.
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