Biomedical scaffold fabrication has seen advancements in mimicking the native extracellular matrix through intricate three-dimensional(3D)structures conducive to tissue regeneration.Coiled fibrous scaffolds have emerg...Biomedical scaffold fabrication has seen advancements in mimicking the native extracellular matrix through intricate three-dimensional(3D)structures conducive to tissue regeneration.Coiled fibrous scaffolds have emerged as promising substrates owing to their ability to provide unique topographical cues.In this study,coiled poly(ε-caprolactone)(PCL)fibrous bundles were fabricated using an alginate-based composite system,and processed with 3D printing.The unique structure was obtained through the die-swell phenomenon related to the release of residual stresses from the printed strut,thereby transforming aligned PCL fibers into coiled structures.The effects of printing parameters,such as pneumatic pressure and nozzle moving speed,on fiber morphology were investigated to ensure a consistent formation of coiled PCL fibers.The resulting coiled PCL fibrous scaffold demonstrated higher activation of mechanotransduction signaling as well as upregulation of osteogenic-related genes in human adipose stem cells(hASCs),supporting its potential in bone tissue engineering.展开更多
Helically coiled tube-in-tube(HCTT)heat exchangers are widely applied to the process technology because of their compactness and higher heat transfer efficiency.HCTT heat exchangers play an important role in liquified...Helically coiled tube-in-tube(HCTT)heat exchangers are widely applied to the process technology because of their compactness and higher heat transfer efficiency.HCTT heat exchangers play an important role in liquified natural gas(LNG)use and cold energy recovery.The heat transfer characteristics,pressure distribution,and degree of vaporization of LNG in HCTT heat exchangers are numerically investigated.By comparing the simulation results of the computational model with existing experimental results,the effectiveness of the computational model is verified.The numerical simulation results show the vapor volume fraction of the HCTT heat exchanger is related to the inlet Reynolds number,inner tube diameters,and helix diameter.The vapor volume fraction increases rapidly from the fourth to the seventh equal division points of the helix tube length.On condition that the inlet Reynolds number is greater than 33500,the pressure drop rate gradually increases.When the magnitude of the vapor volume fraction is below 0.2,the heat transfer coefficient increase rate is greater than that when the vapor volume fraction is above 0.2.The heat exchange efficiency of HCTT heat exchangers increases with the decrease of the ratio of helix diameter to inner tube diameter.展开更多
Twisted and coiled polymer actuator(TCPA)is a type of artificial muscle that can be driven by heating due to its structure.A key issue with TCPA performance is the low driven frequency due to slow heat transfer in hea...Twisted and coiled polymer actuator(TCPA)is a type of artificial muscle that can be driven by heating due to its structure.A key issue with TCPA performance is the low driven frequency due to slow heat transfer in heating and cooling cycles,especially during cooling.We developed a numerical model of coating heating and nitrogen gas cooling that can effectively improve the driven forces and frequencies of the TCPA.Results indicate that natural cooling and electric fan cooling modes used in many experiments cannot restore the TCPA to its initial configuration when driven frequencies are high.Nitrogen gas cooling,at high driven frequencies,can fully restore the TCPA to its initial configuration,which is crucial for maintaining artificial muscle flexibility.In addition,as driven frequency increases,the corresponding driven force decreases.Systematic parametric studies were carried out to provide inspirations for optimizing TCPA design.The integrative computational study presented here provides a fundamental mechanistic understanding of the driven response in TCPA and sheds light on the rational design of TCPA through changing cooling modes.展开更多
As compact and efficient heat exchange equipment,helically coiled tube-in-tube heat exchangers(HCTT heat exchangers)are widely used in many industrial processes.However,the thermal-hydraulic research of liquefied natu...As compact and efficient heat exchange equipment,helically coiled tube-in-tube heat exchangers(HCTT heat exchangers)are widely used in many industrial processes.However,the thermal-hydraulic research of liquefied natural gas(LNG)as the working fluid inHCTT heat exchangers is rarely reported.In this paper,the characteristics of HCTT heat exchangers,in which LNG flows in the inner tube and ethylene glycol-water solution flows in the outer tube,are studied by numerical simulations.The influences of heat transfer characteristics and pressure drops of the HCTT heat transfers are studied by changing the initial flow velocity,the helical middle diameter,and the helical pitch.The results indicate that different initial flow velocities in the inner tube and the outer tube of the HCTT heat exchanger have little influence on the secondary flow of the fluid in the helical tubes,and the overall flow characteristics tend to be stable.The smaller helical middle diameter of the HCTT heat exchanger leads to the shorter fluid flow length,the smaller resistance along the tubes and the increase of initial pressure under the condition of constant inlet velocity,which promotes the occurrence of secondary flow.The axial flow of fluid promotes the destruction of heat transfer boundary layer and gains strength of the turbulence and heat transfer efficiency.With the increase of the helical pitch of the HCTT heat exchanger,the turbulent intensity and the heat transfer efficiency are also increased.Moreover,the improvement of the flow state of the HCTT exchanger in a longer helical pitch also enhances the heat exchange efficiency.展开更多
Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of th...Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of the geometric and system parameters on heat transfer characteristics in helically coiled tubes are investigated by collecting large amounts of experimental data and analyzing the heat transfer mechanisms. The existing correlations are divided into two categories,and they are calculated with the experimental data.The Dn factor is introduced to take into account the effect of a complex geometrical structure on flow boiling heat transfer.A new correlation is developed for predicting the flow boiling heat transfer coefficients in the helically coiled tubes,which is validated by the experimental data of R134a flow boiling heat transfer in them;and the average relative error and root mean square error of the new correlation are calculated.The results show that the new correlation agrees well with the experimental data,indicating that the new correlation can be used for predicting flow boiling heat transfer characteristics in the helically coiled tubes.展开更多
A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the ba...A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the basic motion law of the shear ram,combined its structural and operating parameters comprehensively,a model for solving the stress on the cutting edge was established corresponding to three stages(i.e.,shear point contact,cutting and penetrating the drill pipe)according to the wedge stress theory.Then,based on the novel shear ram,the numerical simulation and indoor shear experiment were carried out on CT90 coiled tubing to understand the variation laws of ram stress and shear point stress in the shearing process.And the following research results were obtained.First,when the shear point doesn't contact with the CT90 coiled tubing,the stress at the V-shaped angular center of the ram is the largest,and that at the shear point is extremely small.Second,when the shear point just touches the CT90 coiled tubing,the phenomenon of stress concentration occurs in the vicinity of the shear point of the ram cutting edge.Third,when the shear point cuts into the CT90 coiled tubing,the stress on the shear point and on both wedge edges is the largest,reaching the strength limit of the ram(1050MPa).Fourth,when the shear point enters the annulus after penetrating the CT90 coiled tubing,the ram stress on both sides of the junction between the cutting edge chamfer and the vertical plane is the largest.Fifth,After the CT90 coiled tubing is cut,crack damage occurs in the vicinity of the shear point of the ram cutting edge.In conclusion,the research results can better reflect the stress state of the ram cutting edge and its interaction with the drill pipe in the shearing process,and can provide an important reference for the design,manufacturing and the correct field application of shear rams.展开更多
Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angl...Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angle reached 12n. As the varying radius of curvature became a dominant flow parameter, three-dimensional flow analysis was performed to this flow together with different Reynolds numbers while constant wall heat flux condition was set in thermal field. From the analysis, centrifugal force due to curvature effect is found to have significant role in behavior of pressure drop and heat transfer. The centrifugal force enhances pressure drop and heat transfer to have generally higher values in the spiral coiled tube than those in the straight tube. Even then, friction factor and Nusselt number are found to follow the proportionality with square root of the Dean number. Individual effect of flow parameters of Reynolds number and curvature ratio was investigated and effect of Reynolds number is found to be stronger than that of curvature effect.展开更多
This paper presents the heat transfer characteristics of A1203-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentra ti...This paper presents the heat transfer characteristics of A1203-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentra tion of A1203-water nanofluids. The results showed considerable enhancement of convective heat transfer using the nanofluids. The empirical correlations developed for Nusselt number in terms of Reynolds number, Prandtl number, viscosity ratio and volume concentration fit with the experimental data within ±10%. The heat transfer characteris tics were also simulated using computational fluid dynamics using FLUENT software with the standard ke model and multiple reference frame were adopted. The computational fluid dynamics （CFD） predicted Nusselt number agrees well with the experimental value and the discrepancy is found to be less than ＋8%.展开更多
Complex working condition of coiled tube （CT） steel demands high strength and low ratio of yield strength （YS） to tensile strength （TS）. Reasonable microstructure control is a key problem of CT steel. Controlled...Complex working condition of coiled tube （CT） steel demands high strength and low ratio of yield strength （YS） to tensile strength （TS）. Reasonable microstructure control is a key problem of CT steel. Controlled rolling and controlled cooling experiments were carded out by two kinds of tested steels with different chemical compositions to develop the non-quenched and tempered CT80 steel. Mechanical properties of the tested steels at different processes are all in good agreement with the properties requirement of CT80. Increasing of Mo and Nb contents improves transformation of acicular ferrite and martensite-austenite （M-A） islands. 4 vol% of fine M/A islands increase TS and decreases ratio of YS/ TS, Cooling rate increasing also improves acicular ferrite transformation and enhances TS, but has little effect on ratio of YS/TS. To meet the requirement of high strength and low ratio of YS/TS, optimized complex microstructure of the CT80 steel is composed of acicular ferrite, about 30 vol% of bainite and 4 vol% of M-A islands.展开更多
To improve the rate of penetration(ROP) in drilling deep and hard formations, this paper proposes a new drilling method called coiled tubing partial underbalanced drilling(CT-PUBD). As a preliminary investigation into...To improve the rate of penetration(ROP) in drilling deep and hard formations, this paper proposes a new drilling method called coiled tubing partial underbalanced drilling(CT-PUBD). As a preliminary investigation into the new drilling method, this paper presents predictions of hole cleaning efficiency, drilling speed, cuttings migration and pressure loss in the drilling process with CT-PUBD. Based on numerical simulation and full-scale experimental studies, we conclude that using CT-PUBD, an underbalanced drilling condition can be achieved near the bit while maintaining wellbore safety at the same time. This condition can be achieved using a cuttings discharge device, a rotary packer and a backflow controller.According to the numerical simulations performed in this study, CT-PUBD can achieve high efficiency of hole cleaning.Along the cuttings migration process, the fluid velocities can reach the maximum values in the backflow holes. A full-scale laboratory experimental system was used to test the hydraulic characteristics and obtain the drilling performance of the new technology. The result shows that CT-PUBD significantly improves the ROP compared to the conventional drilling method.展开更多
Simulations were performed to examine the effects of a coiled tube after a T-junction on the mixing and flow characteristics. A coiled tube was found to have two effects: inducing a radial flow and flattening the axia...Simulations were performed to examine the effects of a coiled tube after a T-junction on the mixing and flow characteristics. A coiled tube was found to have two effects: inducing a radial flow and flattening the axial velocity distribution, which enhances and weakens the mixing, respectively. In the straight tube section connecting the Tjunction and coiled tube, the latter may dominate and cause the mixing to deteriorate. An experiment was performed with the Villermaux/Dushman method to verify the simulation results. Based on a mixing performance simulation with various fluid and geometric structure parameters, a dimensionless correlation was obtained that can be used to determine the mixing intensity along the coiled tube with a deviation of less than 1.5%.These results provide guidance for designing a coiled tube or optimizing the operating conditions to meet the mixing requirements of specific chemical processes.展开更多
A new method is presented to describe and analyze the spatial compliance ofcoiled springs using screw theory. After an abbreviated description for the deformation of a beamelement using screw theory, the spatial compl...A new method is presented to describe and analyze the spatial compliance ofcoiled springs using screw theory. After an abbreviated description for the deformation of a beamelement using screw theory, the spatial compliance density for a beam element is derived based onthe fundamental material theory and reasonable assumptions, and the spatial compliance of the beamwith finite length is obtained by integral. The spatial compliance of coiled springs is furtheranalyzed using the spatial compliance density of the beam element. By calculating theeigencompliance and Ball's principle screws for the whole compliance of system, the complianceproperties varying with the basic physical parameters of the system are illustrated in detail. Thebasic ideas can be used for the design and application of the coiled springs and the other compliantmechanisms with spatial compliant beam element.展开更多
Coiled polymer artificial muscles with both large tensile stroke and giant force generation are needed for practical applications in robotics,soft exosuits,and prosthesis.However,most polymer yarn artificial muscles c...Coiled polymer artificial muscles with both large tensile stroke and giant force generation are needed for practical applications in robotics,soft exosuits,and prosthesis.However,most polymer yarn artificial muscles cannot generate a large force or stress.Here,we report an inexpensive Twisted and Coiled Polymer artificial muscle(TCP)that performs both large isobaric and isometric contractions.This TCP can generate a tensile stroke of 20.1%and a specific work capacity of up to 1.3 kJ kg^(−1) during temperature changes from 20 to 180℃.Moreover,the nylon yarn artificial muscle produced a reversible output stress of 28.4 MPa,which is 100 times larger than human skeletal muscle.A robot arm and a simple gripper were made to demonstrate the isobaric actuation and isometric actuation of our TCP muscle,repectivley.Thus,the polymer artificial muscles with dual-mode actuation show potential applications in the field of robotics,grippers,and exoskeletons and so on.展开更多
There are many problems associated with coiled tubing drilling operations, such as great circulation pressure loss inside pipe, difficulties in weight on bit(WOB) transferring, and high probability of differential sti...There are many problems associated with coiled tubing drilling operations, such as great circulation pressure loss inside pipe, difficulties in weight on bit(WOB) transferring, and high probability of differential sticking. Aiming at these problems, solids-free brine drilling fluid system was developed on the basis of formulation optimization with brine base fluid experiment, which was evaluated and applied to field drilling. Based on the optimization of flow pattern regulator, salt-resisting filtrate reducer, high performance lubricant and bit cleaner, the basic formula of the solids-free brine drilling fluid system was formed: brine +(0.1%-0.2%) Na OH +(0.2%-0.4%) HT-XC +(2.0%-3.0%) YLJ-1 +(0.5%-2.0%) SDNR +(1.0%-2.5%) FT-1 A +(1.0%-5.0%) SD-505 + compound salt density regulator. Lab evaluation showed that the fluid had satisfactory temperature resistance(up to 150 ℃), excellent cuttings tolerance(up to 25%), and strong inhibition(92.7% cuttings recovery); Moreover, its lubrication performance was similar to that of all oil-based drilling fluid. The wellbore could be fairly cleaned at annular up-flow velocity of more than 0.8 m/s if the ratio of yield point to plastic viscosity was kept above 0.5. This fluid system has been applied in the drilling of three coiled tubing sidetracking wells in the Liaohe Oilfield, during which the system was stable and easy to adjust, resulting in excellent cuttings transportation, high ROP, regular hole size, and no down hole accidents. In summary, the solids-free brine drilling fluid system can meet the technical requirements of coiled tubing drilling.展开更多
To solve the problems in the quality control and improvement of coiled tubing steel strips production, such as scattered and inefficient production data, difficult performance fluctuation factor analysis, complex mult...To solve the problems in the quality control and improvement of coiled tubing steel strips production, such as scattered and inefficient production data, difficult performance fluctuation factor analysis, complex multivariate statistical analysis, and low accuracy and difficulty in mechanical property prediction, an industrial data analysis platform for coiled tubing steel strips production has been preliminarily developed.As the premise and foundation of analysis, industrial data collection, storage, and utilization are realized by using multiple big data technologies.With Django as the agile development framework, data visualization and comprehensive analyses are achieved.The platform has functions including overview survey, stability analysis, comprehensive analysis(such as exploratory data analysis, correlation analysis, and multivariate statistics),precise steel strength prediction, and skin-passing process recommendation.The platform is helpful for production overviewing and prompt responding, laying a foundation for an in-depth understanding of product characteristics and improving product performance stability.展开更多
The coiled tubing plugging has become the main means of plugging in gas Wells in Xinjiang. These Wells are deep and have high pressure, which can easily affect the fatigue life of the operating coiled tubing. In order...The coiled tubing plugging has become the main means of plugging in gas Wells in Xinjiang. These Wells are deep and have high pressure, which can easily affect the fatigue life of the operating coiled tubing. In order to improve the life of coiled tubing in high-pressure gas Wells, this paper studies the plugging conditions of coiled tubing in high-pressure ultra-deep Wells. Firstly, the cross section deformation of coiled tubing under high internal pressure is analyzed. Secondly, the factors influencing the fatigue life of coiled tubing and the influence of surface damage on the fatigue life of coiled tubing were studied. Finally, the mechanism of furrow damage caused by coiled tubing and the main measures to reduce furrow damage are analyzed. The following suggestions are made to improve the life of coiled tubing: select the right material and the right size coiled tubing;Use appropriate measures to prevent premature coiled tubing failure and reduce operating costs.展开更多
The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet sub...The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet subcooling from 4.7 to 15.0℃, heat flux from 0.11 to 8.9 kW/m2 and mass flux from 218. 2 to 443. 7 kg/（ m2 · s ）. The heat flux, superheat and temperature undershoot at the ONB are analyzed in vertical helically-coiled tubes. Also, the effects of mass flux, system pressure, inlet subcooling and geometric parameters on the ONB are studied. The results demonstrate that the inception heat flux and superheat increase with increasing mass flux and inlet subcooling, but decrease with increasing system pressure and helix diameter. The pitch of the helical coil has a slight effect on the wall superheat and heat flux at the ONB. The correlation of heat flux at the ONB of subcooled flow boiling in helical coil is developed based on the experimental data, and it shows a good agreement with the experimental data.展开更多
In the present study,the effect of injecting air bubble size on the thermal performance of a vertical counter-current shell and coiled tube heat exchanger is experimentally investigated.The experiments were accomplish...In the present study,the effect of injecting air bubble size on the thermal performance of a vertical counter-current shell and coiled tube heat exchanger is experimentally investigated.The experiments were accomplished in a cylindrical shape heat exchanger with a 50 cm height and 15 cm outer diameter.Copper coil with 3.939 m equivalent length and 0.6 cm outer diameter was used to carry the hot fluid(water).Four different cold fluid(shell side)flow rates(Q_(s)=2;4;6 and 8 LPM)Þunder laminar flow conditions(316≤Re≤1223),constant hot(coil side)flow rate fluid rates(Q_(h)=1 LPM),four different injected air flow rates(Q_(a)=0:5;1;1:5 and 2 LPM),invariant temperature difference(ΔT=20°C),and constant bubble’s number(1400)were tested.To demonstrate the effect of bubble size,a sparger with orifice diameters of 0.1,0.8,and 1.5 mm was manufactured and used in the study.The overall heat transfer coefficient(U),NTU,effectiveness,and pressure loss were invested.The experimental results clearly showed that the heat exchanger’s thermal efficiency significantly improved with increasing the shell side flow rate and the injected air flow rate.The maximum improvement in U,NTU,and effectiveness was 153%,153%,and 68%,respectively.The thermal performance of the heat exchanger was shown to be improved with increasing the bubble size.Although the latter finding agrees with recent CFD published results,more studies need to be confirmed.展开更多
To assess clinicopathologic correlations of a novel placental lesion featuring a distinct ring-like periarterial edema of stem villi (PASE). A retrospective case-control statistical comparison (Yates χ2 or analysis o...To assess clinicopathologic correlations of a novel placental lesion featuring a distinct ring-like periarterial edema of stem villi (PASE). A retrospective case-control statistical comparison (Yates χ2 or analysis of variance) of 30 clinical and 41 placental features of 100 consecutive placentas with PASE and 100 gestational age-matched cases without PASE, extracted from 2403 placentas from high-risk pregnancies signed out by the author since year 2006. The PASE was seen in 4.2% of placentas, average gestational age 35.9 weeks (range, 24 - 42 weeks). Frequencies of stem obliterative endarteritis and hypercoiled umbilical cord (coiling index > 0.3) were 23% vs 5% (p = 0.005), and 20% vs 9% (p = 0.04) in the study group and comparative group, respectively. There were no statistically significant differences (p > 0.05) between the groups in clinical or other placental variables. The PASE may be linked to chronically abnormal blood flow in umbilical cord arteries and their stem branches and may be a histological placental sign of non-obliterative umbilical cord compromise.展开更多
基金supported by the‘Korea National Institute of Health’research project(2022ER130502)a grant from by SMC-SKKU Future Convergence Academic Research Program,2024supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(RS-2024-00336758)。
文摘Biomedical scaffold fabrication has seen advancements in mimicking the native extracellular matrix through intricate three-dimensional(3D)structures conducive to tissue regeneration.Coiled fibrous scaffolds have emerged as promising substrates owing to their ability to provide unique topographical cues.In this study,coiled poly(ε-caprolactone)(PCL)fibrous bundles were fabricated using an alginate-based composite system,and processed with 3D printing.The unique structure was obtained through the die-swell phenomenon related to the release of residual stresses from the printed strut,thereby transforming aligned PCL fibers into coiled structures.The effects of printing parameters,such as pneumatic pressure and nozzle moving speed,on fiber morphology were investigated to ensure a consistent formation of coiled PCL fibers.The resulting coiled PCL fibrous scaffold demonstrated higher activation of mechanotransduction signaling as well as upregulation of osteogenic-related genes in human adipose stem cells(hASCs),supporting its potential in bone tissue engineering.
基金supported by Innovative Team Introduction Projects for New Universities in Jinan City(No.2021GXRC075).
文摘Helically coiled tube-in-tube(HCTT)heat exchangers are widely applied to the process technology because of their compactness and higher heat transfer efficiency.HCTT heat exchangers play an important role in liquified natural gas(LNG)use and cold energy recovery.The heat transfer characteristics,pressure distribution,and degree of vaporization of LNG in HCTT heat exchangers are numerically investigated.By comparing the simulation results of the computational model with existing experimental results,the effectiveness of the computational model is verified.The numerical simulation results show the vapor volume fraction of the HCTT heat exchanger is related to the inlet Reynolds number,inner tube diameters,and helix diameter.The vapor volume fraction increases rapidly from the fourth to the seventh equal division points of the helix tube length.On condition that the inlet Reynolds number is greater than 33500,the pressure drop rate gradually increases.When the magnitude of the vapor volume fraction is below 0.2,the heat transfer coefficient increase rate is greater than that when the vapor volume fraction is above 0.2.The heat exchange efficiency of HCTT heat exchangers increases with the decrease of the ratio of helix diameter to inner tube diameter.
基金Natural Science Foundation of China,11925204,Jizeng Wangthe Fundamental Research Funds for the Central Universities,lzujbky-2024-jdzx02,Zhiwen Gao。
文摘Twisted and coiled polymer actuator(TCPA)is a type of artificial muscle that can be driven by heating due to its structure.A key issue with TCPA performance is the low driven frequency due to slow heat transfer in heating and cooling cycles,especially during cooling.We developed a numerical model of coating heating and nitrogen gas cooling that can effectively improve the driven forces and frequencies of the TCPA.Results indicate that natural cooling and electric fan cooling modes used in many experiments cannot restore the TCPA to its initial configuration when driven frequencies are high.Nitrogen gas cooling,at high driven frequencies,can fully restore the TCPA to its initial configuration,which is crucial for maintaining artificial muscle flexibility.In addition,as driven frequency increases,the corresponding driven force decreases.Systematic parametric studies were carried out to provide inspirations for optimizing TCPA design.The integrative computational study presented here provides a fundamental mechanistic understanding of the driven response in TCPA and sheds light on the rational design of TCPA through changing cooling modes.
基金supported by Innovative Team Introduction Projects for New Universities in Jinan City(No.2021GXRC075).
文摘As compact and efficient heat exchange equipment,helically coiled tube-in-tube heat exchangers(HCTT heat exchangers)are widely used in many industrial processes.However,the thermal-hydraulic research of liquefied natural gas(LNG)as the working fluid inHCTT heat exchangers is rarely reported.In this paper,the characteristics of HCTT heat exchangers,in which LNG flows in the inner tube and ethylene glycol-water solution flows in the outer tube,are studied by numerical simulations.The influences of heat transfer characteristics and pressure drops of the HCTT heat transfers are studied by changing the initial flow velocity,the helical middle diameter,and the helical pitch.The results indicate that different initial flow velocities in the inner tube and the outer tube of the HCTT heat exchanger have little influence on the secondary flow of the fluid in the helical tubes,and the overall flow characteristics tend to be stable.The smaller helical middle diameter of the HCTT heat exchanger leads to the shorter fluid flow length,the smaller resistance along the tubes and the increase of initial pressure under the condition of constant inlet velocity,which promotes the occurrence of secondary flow.The axial flow of fluid promotes the destruction of heat transfer boundary layer and gains strength of the turbulence and heat transfer efficiency.With the increase of the helical pitch of the HCTT heat exchanger,the turbulent intensity and the heat transfer efficiency are also increased.Moreover,the improvement of the flow state of the HCTT exchanger in a longer helical pitch also enhances the heat exchange efficiency.
基金The National Natural Science Foundation of China(No.50776055,51076084)
文摘Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of the geometric and system parameters on heat transfer characteristics in helically coiled tubes are investigated by collecting large amounts of experimental data and analyzing the heat transfer mechanisms. The existing correlations are divided into two categories,and they are calculated with the experimental data.The Dn factor is introduced to take into account the effect of a complex geometrical structure on flow boiling heat transfer.A new correlation is developed for predicting the flow boiling heat transfer coefficients in the helically coiled tubes,which is validated by the experimental data of R134a flow boiling heat transfer in them;and the average relative error and root mean square error of the new correlation are calculated.The results show that the new correlation agrees well with the experimental data,indicating that the new correlation can be used for predicting flow boiling heat transfer characteristics in the helically coiled tubes.
基金supported by the National Major Special Project of Oil and Gas(No.2016ZX05042003-001,2016ZX05066004-002)the Scientific and Technological Research Guidance Project(No.MTKJ2016-279)by the China National Coal Association,and the Jiangsu Provincial Postdoctoral Scientific and Technological Funding Program(No.1601053C).
文摘A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the basic motion law of the shear ram,combined its structural and operating parameters comprehensively,a model for solving the stress on the cutting edge was established corresponding to three stages(i.e.,shear point contact,cutting and penetrating the drill pipe)according to the wedge stress theory.Then,based on the novel shear ram,the numerical simulation and indoor shear experiment were carried out on CT90 coiled tubing to understand the variation laws of ram stress and shear point stress in the shearing process.And the following research results were obtained.First,when the shear point doesn't contact with the CT90 coiled tubing,the stress at the V-shaped angular center of the ram is the largest,and that at the shear point is extremely small.Second,when the shear point just touches the CT90 coiled tubing,the phenomenon of stress concentration occurs in the vicinity of the shear point of the ram cutting edge.Third,when the shear point cuts into the CT90 coiled tubing,the stress on the shear point and on both wedge edges is the largest,reaching the strength limit of the ram(1050MPa).Fourth,when the shear point enters the annulus after penetrating the CT90 coiled tubing,the ram stress on both sides of the junction between the cutting edge chamfer and the vertical plane is the largest.Fifth,After the CT90 coiled tubing is cut,crack damage occurs in the vicinity of the shear point of the ram cutting edge.In conclusion,the research results can better reflect the stress state of the ram cutting edge and its interaction with the drill pipe in the shearing process,and can provide an important reference for the design,manufacturing and the correct field application of shear rams.
基金supported by the Second Stage of Brain Korea 21 Projects,Korea
文摘Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angle reached 12n. As the varying radius of curvature became a dominant flow parameter, three-dimensional flow analysis was performed to this flow together with different Reynolds numbers while constant wall heat flux condition was set in thermal field. From the analysis, centrifugal force due to curvature effect is found to have significant role in behavior of pressure drop and heat transfer. The centrifugal force enhances pressure drop and heat transfer to have generally higher values in the spiral coiled tube than those in the straight tube. Even then, friction factor and Nusselt number are found to follow the proportionality with square root of the Dean number. Individual effect of flow parameters of Reynolds number and curvature ratio was investigated and effect of Reynolds number is found to be stronger than that of curvature effect.
文摘This paper presents the heat transfer characteristics of A1203-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentra tion of A1203-water nanofluids. The results showed considerable enhancement of convective heat transfer using the nanofluids. The empirical correlations developed for Nusselt number in terms of Reynolds number, Prandtl number, viscosity ratio and volume concentration fit with the experimental data within ±10%. The heat transfer characteris tics were also simulated using computational fluid dynamics using FLUENT software with the standard ke model and multiple reference frame were adopted. The computational fluid dynamics （CFD） predicted Nusselt number agrees well with the experimental value and the discrepancy is found to be less than ＋8%.
基金supported by the Beijing Higher Education Young Elite Teacher Project (No. YETP0355)the Fundamental Research Funds for the Central Universities of China (No. FRF-TP-12-046A)
文摘Complex working condition of coiled tube （CT） steel demands high strength and low ratio of yield strength （YS） to tensile strength （TS）. Reasonable microstructure control is a key problem of CT steel. Controlled rolling and controlled cooling experiments were carded out by two kinds of tested steels with different chemical compositions to develop the non-quenched and tempered CT80 steel. Mechanical properties of the tested steels at different processes are all in good agreement with the properties requirement of CT80. Increasing of Mo and Nb contents improves transformation of acicular ferrite and martensite-austenite （M-A） islands. 4 vol% of fine M/A islands increase TS and decreases ratio of YS/ TS, Cooling rate increasing also improves acicular ferrite transformation and enhances TS, but has little effect on ratio of YS/TS. To meet the requirement of high strength and low ratio of YS/TS, optimized complex microstructure of the CT80 steel is composed of acicular ferrite, about 30 vol% of bainite and 4 vol% of M-A islands.
基金the National Natural Science Foundation of China (Grant No. 51474232)the National Science and Technology Major Project (Grant No. 2016ZX05022)
文摘To improve the rate of penetration(ROP) in drilling deep and hard formations, this paper proposes a new drilling method called coiled tubing partial underbalanced drilling(CT-PUBD). As a preliminary investigation into the new drilling method, this paper presents predictions of hole cleaning efficiency, drilling speed, cuttings migration and pressure loss in the drilling process with CT-PUBD. Based on numerical simulation and full-scale experimental studies, we conclude that using CT-PUBD, an underbalanced drilling condition can be achieved near the bit while maintaining wellbore safety at the same time. This condition can be achieved using a cuttings discharge device, a rotary packer and a backflow controller.According to the numerical simulations performed in this study, CT-PUBD can achieve high efficiency of hole cleaning.Along the cuttings migration process, the fluid velocities can reach the maximum values in the backflow holes. A full-scale laboratory experimental system was used to test the hydraulic characteristics and obtain the drilling performance of the new technology. The result shows that CT-PUBD significantly improves the ROP compared to the conventional drilling method.
基金Supported by the National Natural Science Foundation of China(21422603,U166212)the National Science and Technology Support Program of China(2011BAC06B01)
文摘Simulations were performed to examine the effects of a coiled tube after a T-junction on the mixing and flow characteristics. A coiled tube was found to have two effects: inducing a radial flow and flattening the axial velocity distribution, which enhances and weakens the mixing, respectively. In the straight tube section connecting the Tjunction and coiled tube, the latter may dominate and cause the mixing to deteriorate. An experiment was performed with the Villermaux/Dushman method to verify the simulation results. Based on a mixing performance simulation with various fluid and geometric structure parameters, a dimensionless correlation was obtained that can be used to determine the mixing intensity along the coiled tube with a deviation of less than 1.5%.These results provide guidance for designing a coiled tube or optimizing the operating conditions to meet the mixing requirements of specific chemical processes.
基金This project is supported by National Natural Science Foundation of China(No.50075009) and SRF for ROCS, SEM.
文摘A new method is presented to describe and analyze the spatial compliance ofcoiled springs using screw theory. After an abbreviated description for the deformation of a beamelement using screw theory, the spatial compliance density for a beam element is derived based onthe fundamental material theory and reasonable assumptions, and the spatial compliance of the beamwith finite length is obtained by integral. The spatial compliance of coiled springs is furtheranalyzed using the spatial compliance density of the beam element. By calculating theeigencompliance and Ball's principle screws for the whole compliance of system, the complianceproperties varying with the basic physical parameters of the system are illustrated in detail. Thebasic ideas can be used for the design and application of the coiled springs and the other compliantmechanisms with spatial compliant beam element.
基金Financial support from the program of the National Natural Science Foundation of China (Grant no.52105057,51905222)Natural Science Foundation of Jiangsu Province (Grant no.BK20200916)+3 种基金China Postdoctoral Science Foundation (no.2021M691307,no.2022T150274)Jiangsu Postdoctoral Research Foundation (no.2021K543C)Key Research Project of Zhejiang LabSenior Talent Foundation of Jiangsu University (Grant no.5501110013)are acknowledged.
文摘Coiled polymer artificial muscles with both large tensile stroke and giant force generation are needed for practical applications in robotics,soft exosuits,and prosthesis.However,most polymer yarn artificial muscles cannot generate a large force or stress.Here,we report an inexpensive Twisted and Coiled Polymer artificial muscle(TCP)that performs both large isobaric and isometric contractions.This TCP can generate a tensile stroke of 20.1%and a specific work capacity of up to 1.3 kJ kg^(−1) during temperature changes from 20 to 180℃.Moreover,the nylon yarn artificial muscle produced a reversible output stress of 28.4 MPa,which is 100 times larger than human skeletal muscle.A robot arm and a simple gripper were made to demonstrate the isobaric actuation and isometric actuation of our TCP muscle,repectivley.Thus,the polymer artificial muscles with dual-mode actuation show potential applications in the field of robotics,grippers,and exoskeletons and so on.
基金Supported by the China National Science and Technology Major Project(2016ZX05020-004)
文摘There are many problems associated with coiled tubing drilling operations, such as great circulation pressure loss inside pipe, difficulties in weight on bit(WOB) transferring, and high probability of differential sticking. Aiming at these problems, solids-free brine drilling fluid system was developed on the basis of formulation optimization with brine base fluid experiment, which was evaluated and applied to field drilling. Based on the optimization of flow pattern regulator, salt-resisting filtrate reducer, high performance lubricant and bit cleaner, the basic formula of the solids-free brine drilling fluid system was formed: brine +(0.1%-0.2%) Na OH +(0.2%-0.4%) HT-XC +(2.0%-3.0%) YLJ-1 +(0.5%-2.0%) SDNR +(1.0%-2.5%) FT-1 A +(1.0%-5.0%) SD-505 + compound salt density regulator. Lab evaluation showed that the fluid had satisfactory temperature resistance(up to 150 ℃), excellent cuttings tolerance(up to 25%), and strong inhibition(92.7% cuttings recovery); Moreover, its lubrication performance was similar to that of all oil-based drilling fluid. The wellbore could be fairly cleaned at annular up-flow velocity of more than 0.8 m/s if the ratio of yield point to plastic viscosity was kept above 0.5. This fluid system has been applied in the drilling of three coiled tubing sidetracking wells in the Liaohe Oilfield, during which the system was stable and easy to adjust, resulting in excellent cuttings transportation, high ROP, regular hole size, and no down hole accidents. In summary, the solids-free brine drilling fluid system can meet the technical requirements of coiled tubing drilling.
文摘To solve the problems in the quality control and improvement of coiled tubing steel strips production, such as scattered and inefficient production data, difficult performance fluctuation factor analysis, complex multivariate statistical analysis, and low accuracy and difficulty in mechanical property prediction, an industrial data analysis platform for coiled tubing steel strips production has been preliminarily developed.As the premise and foundation of analysis, industrial data collection, storage, and utilization are realized by using multiple big data technologies.With Django as the agile development framework, data visualization and comprehensive analyses are achieved.The platform has functions including overview survey, stability analysis, comprehensive analysis(such as exploratory data analysis, correlation analysis, and multivariate statistics),precise steel strength prediction, and skin-passing process recommendation.The platform is helpful for production overviewing and prompt responding, laying a foundation for an in-depth understanding of product characteristics and improving product performance stability.
文摘The coiled tubing plugging has become the main means of plugging in gas Wells in Xinjiang. These Wells are deep and have high pressure, which can easily affect the fatigue life of the operating coiled tubing. In order to improve the life of coiled tubing in high-pressure gas Wells, this paper studies the plugging conditions of coiled tubing in high-pressure ultra-deep Wells. Firstly, the cross section deformation of coiled tubing under high internal pressure is analyzed. Secondly, the factors influencing the fatigue life of coiled tubing and the influence of surface damage on the fatigue life of coiled tubing were studied. Finally, the mechanism of furrow damage caused by coiled tubing and the main measures to reduce furrow damage are analyzed. The following suggestions are made to improve the life of coiled tubing: select the right material and the right size coiled tubing;Use appropriate measures to prevent premature coiled tubing failure and reduce operating costs.
基金The National Natural Science Foundation of China(No.50776055,51076084)the Natural Science Foundation of Shandong Province(No.ZR2016YL005)
文摘The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet subcooling from 4.7 to 15.0℃, heat flux from 0.11 to 8.9 kW/m2 and mass flux from 218. 2 to 443. 7 kg/（ m2 · s ）. The heat flux, superheat and temperature undershoot at the ONB are analyzed in vertical helically-coiled tubes. Also, the effects of mass flux, system pressure, inlet subcooling and geometric parameters on the ONB are studied. The results demonstrate that the inception heat flux and superheat increase with increasing mass flux and inlet subcooling, but decrease with increasing system pressure and helix diameter. The pitch of the helical coil has a slight effect on the wall superheat and heat flux at the ONB. The correlation of heat flux at the ONB of subcooled flow boiling in helical coil is developed based on the experimental data, and it shows a good agreement with the experimental data.
文摘In the present study,the effect of injecting air bubble size on the thermal performance of a vertical counter-current shell and coiled tube heat exchanger is experimentally investigated.The experiments were accomplished in a cylindrical shape heat exchanger with a 50 cm height and 15 cm outer diameter.Copper coil with 3.939 m equivalent length and 0.6 cm outer diameter was used to carry the hot fluid(water).Four different cold fluid(shell side)flow rates(Q_(s)=2;4;6 and 8 LPM)Þunder laminar flow conditions(316≤Re≤1223),constant hot(coil side)flow rate fluid rates(Q_(h)=1 LPM),four different injected air flow rates(Q_(a)=0:5;1;1:5 and 2 LPM),invariant temperature difference(ΔT=20°C),and constant bubble’s number(1400)were tested.To demonstrate the effect of bubble size,a sparger with orifice diameters of 0.1,0.8,and 1.5 mm was manufactured and used in the study.The overall heat transfer coefficient(U),NTU,effectiveness,and pressure loss were invested.The experimental results clearly showed that the heat exchanger’s thermal efficiency significantly improved with increasing the shell side flow rate and the injected air flow rate.The maximum improvement in U,NTU,and effectiveness was 153%,153%,and 68%,respectively.The thermal performance of the heat exchanger was shown to be improved with increasing the bubble size.Although the latter finding agrees with recent CFD published results,more studies need to be confirmed.
文摘To assess clinicopathologic correlations of a novel placental lesion featuring a distinct ring-like periarterial edema of stem villi (PASE). A retrospective case-control statistical comparison (Yates χ2 or analysis of variance) of 30 clinical and 41 placental features of 100 consecutive placentas with PASE and 100 gestational age-matched cases without PASE, extracted from 2403 placentas from high-risk pregnancies signed out by the author since year 2006. The PASE was seen in 4.2% of placentas, average gestational age 35.9 weeks (range, 24 - 42 weeks). Frequencies of stem obliterative endarteritis and hypercoiled umbilical cord (coiling index > 0.3) were 23% vs 5% (p = 0.005), and 20% vs 9% (p = 0.04) in the study group and comparative group, respectively. There were no statistically significant differences (p > 0.05) between the groups in clinical or other placental variables. The PASE may be linked to chronically abnormal blood flow in umbilical cord arteries and their stem branches and may be a histological placental sign of non-obliterative umbilical cord compromise.
