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Simplified Numerical Study of Evaporation Processes Inside Vertical Tubes
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作者 Pawe Ocoń Marzena Nowak Stanisaw Lopata 《Journal of Thermal Science》 SCIE EI CAS CSCD 2014年第2期177-186,共10页
The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wal... The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wall) are determined.Therefore its performance and efficiency is high.The analytical formulas,which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length,are used in this model.The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains. 展开更多
关键词 Numerical modeling heat transfer EVAPORATION vertical tubes Finite Element Method
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An Improved Heat Transfer Correlation for Supercritical Aviation Kerosene Flowing Upward and Downward in Vertical Tubes 被引量:5
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作者 LI Yong CHEN Youqian +2 位作者 ZHANG Yingchun SUN Feng XIE Gongnan 《Journal of Thermal Science》 SCIE EI CAS CSCD 2020年第1期131-143,共13页
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 ... 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. 展开更多
关键词 CORRELATION supercritical n-decane prediction accuracy heat flux vertical tube
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Experimental Study on Condensation Heat Transfer Characteristics of R410A in Short Vertical Tubes 被引量:2
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作者 XU Wenyun JIA Li TAN Zetao 《Journal of Thermal Science》 SCIE EI CAS CSCD 2015年第3期260-268,共9页
An experimental study on condensation heat transfer of R410 A in short vertical tubes(8.02 mm ID and 10.7mm ID) was presented. Experiments were performed in eight short copper tubes length varied from 300 mm to 600 mm... An experimental study on condensation heat transfer of R410 A in short vertical tubes(8.02 mm ID and 10.7mm ID) was presented. Experiments were performed in eight short copper tubes length varied from 300 mm to 600 mm at mass fluxes range of 58–246 kg m-2s-1 and saturation temperature of 38℃. Effects of mass flux, tube length on condensation heat transfer coefficient were investigated. The distribution of temperature, thickness of condensate film and local condensation heat transfer coefficient along the tube were also analyzed.. It is indicated that the entrance effect played an important role in condensation heat transfer of vertical tube, and the influence of entrance effect on average condensation heat transfer coefficients will weaken with the length of tube in the experimental condensation. The experimental results were compared with four well known correlations available in literatures, and the Chen correlation shows good agreement with the experimental data but with ±40% deviation. A new modified condensation heat transfer correlation with 12.7% mean deviation was developed to predict the condensation heat transfer coefficients in short vertical tube based on the experimental data. 展开更多
关键词 CONDENSATION Heat transfer characteristic R410A Short vertical tube Entrance effect
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Emitter discharge characteristics of vertical tube irrigation affected by various factors
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作者 WANG Cheng BAI Dan +1 位作者 LI Yibo BAI Xueli 《排灌机械工程学报》 CSCD 北大核心 2023年第1期102-108,共7页
To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil w... To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil water content, and tube diameter on the emitter discharge of the vertical tube were studied. The results show that quantitative relationship between the time and cumulative infiltration and emitter discharge of the vertical tube is obtained, and R 2 is more than 0.98. Emitter discharge exhibits a positive and negative correlation with the pressure head and soil water content, respectively. Tube dia- meter has a nonsignificant effect on the emitter discharge. Changes of the soil water content around the emitter water outlet are the main causes of emitter discharge variations. In the experiments, the range of vertical tube emitter discharge is 0.056-1.102 L/h. The emitter of vertical tube irrigation automatically adjusts the soil water content and maintains the root zone soil water content within an appropriate range, which achieves continuous irrigation, and further achieves the effect of water-saving. 展开更多
关键词 vertical tube irrigation emitter discharge pressure head initial soil water content
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Passive heat transfer enhancement of laminar mixed convection flow in a vertical dimpled tube 被引量:3
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作者 M.TOOFANI SHAHRAKI A.LAVAJOO A.BEHZADMEHR 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第11期3477-3490,共14页
Heat transfer enhancement in vertical tubes plays an important role on the thermal performance of many heat exchangers and thermal devices.In this work,laminar mixed convection of airflow in a vertical dimpled tube wa... Heat transfer enhancement in vertical tubes plays an important role on the thermal performance of many heat exchangers and thermal devices.In this work,laminar mixed convection of airflow in a vertical dimpled tube was numerically investigated.Three-dimensional elliptical governing equations were solved using the finite-volume technique.For a given dimpled pitch,the effects of three different dimple heights(h/D=0.013,0.027,0.037) have been studied at different Richardson numbers(0.1,1.0 and 1.5).The generated vortex in the vicinity of the dimple destructs the thermal boundary layer and enhances the heat transfer.Therefore,lower wall temperature is seen where the dimples are located.Fluid flow velocity at the near-wall region significantly increases because of buoyancy forces with the increase of Richardson numbers.Such an acceleration at the near-wall region makes the dimples more effective at higher Richardson number.Using a dimpled tube enhances the heat transfer coefficient.However,the pressure drop is not important.For instance,in the case of Ri=1.5 and h/D=0.037,20% gains in the heat transfer enhancement only costs2.5% in the pressure loss.In general,it is recommended using a dimpled tube where the effects of buoyancy forces are important. 展开更多
关键词 dimpled tube laminar mixed convection vertical tube heat transfer enhancement
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Wall-Liquid Mass Transfer for Taylor Bubbles Rising Through Liquid in a Vertical Tube 被引量:1
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作者 贠军贤 沈自求 明平文 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2002年第4期404-410,共7页
Wall-liquid mass transfer for Taylor bubbles rising through liquid column in vertical tubes is an important and fundamental topic in industrial processes.In this work,the characteristics of wall-liquid mass transfer f... Wall-liquid mass transfer for Taylor bubbles rising through liquid column in vertical tubes is an important and fundamental topic in industrial processes.In this work,the characteristics of wall-liquid mass transfer for this special case of slug flow were studied experimentally by limiting diffusion current technique (LDCT). Based on the experimental results and the analysis of hydrodynamic mechanisms,it was proposed that four different zones exist,i.e.the laminar falling film zone,the turbulent falling film zone,the wake region and the remaining liquid slug zone.The corresponding correlations for all these zones were developed. 展开更多
关键词 gas-liquid slug flow Taylor bubble mass transfer vertical tube
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Experimental study of heat transfer of ultra-supercritical pressure water in vertical upward internally ribbed tube 被引量:2
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作者 王为术 Chen Tingkuan +2 位作者 Luo Yushan  Gu Hongfang Yin Fei 《High Technology Letters》 EI CAS 2007年第1期17-22,共6页
Under ultra-supercritical pressure, the heat transfer characteristics of water in vertical upward 4- head internally ribbed tubes with a diameter of 28.65mm and thickness of 8mm were experimentally studied. The experi... Under ultra-supercritical pressure, the heat transfer characteristics of water in vertical upward 4- head internally ribbed tubes with a diameter of 28.65mm and thickness of 8mm were experimentally studied. The experiments were performed at P = 25- 34MPa, G = 450- 1800kg/(m^2·s) and q = 200 600kW/m^2. The results show that the pressure has only a moderate effect on the heat transfer of uhra-supercritical water when the water temperature is below the pseudocritical point. Sharp rise of the wall temperature near the pesudocritical region occurs earlier at a higher pressure. Increasing the mass velocity improves the heat transfer with a much stronger effect below the pesudocritical point than that above the pesudocritical point. For given pressure and mass velocity, the inner wall heat flux also shows a significant effect on the inner wall temperature, with a higher inner wall heat flux leading to a higher inner wall temperature. Increasing of inner wall heat flux leads to an early occurrence of sharp rise of the wall temperature. Correlations of heat transfer coefficients are also presented for vertical upward internally ribbed tubes. 展开更多
关键词 heat transfer supercritieal ultra-supereritieal vertical upward internally fibbed tube
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Boiling Heat Transfer Enhancement in a Vertical Annulus by Introduction of Air in Liquid Flow
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作者 王军 苗君 +1 位作者 刘芸 沈自求 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2004年第5期633-638,共6页
In this paper, boiling heat transfer in a vertical annulus with inner side heated with and without air introduction is experimentally studied. Results show that boiling heat transfer is significantly enhanced by the i... In this paper, boiling heat transfer in a vertical annulus with inner side heated with and without air introduction is experimentally studied. Results show that boiling heat transfer is significantly enhanced by the introduction of air. When air is introduced into the liquid with a temperature below boiling point, the enhancement of heat transfer is also detected. It is concluded from the study that the heat transfer enhanced by introduction of inert gas is due to the liquid vaporization at the gas-liquid interface near the wall, which removes a large amount of latent heat and lowers the interfacial temperature considerably. Thus the gas-liquid interface acts as a 'heat sink'and the heat transfer is augmented significantly. 展开更多
关键词 boiling heat transfer vertical annulus tube air introduction interfacialvaporization heat sink
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Flow and Heat Transfer Instability of Supercritical Carbon Dioxide in a Vertical Heated Tube
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作者 WANG Zhibin LIANG Xingguang +1 位作者 CHEN Ying LUO Xianglong 《Journal of Thermal Science》 SCIE EI CAS CSCD 2023年第4期1477-1486,共10页
Supercritical carbon dioxide(S-CO_(2))is one of the most promising working fluids in energy conversion systems.However,the instability of the flow and heat transfer has caused great harm to the security of energy conv... Supercritical carbon dioxide(S-CO_(2))is one of the most promising working fluids in energy conversion systems.However,the instability of the flow and heat transfer has caused great harm to the security of energy conversion systems.In this work,a transient model based on the Finite Volume Method is set up to investigate the flow and heat transfer instability of CO_(2) changing from a subcritical state to a supercritical state in a vertical heated circular tube.The instability occurs when the wall heat flux is higher than a critical value,which makes the density and mass flow rate variations large enough.A large variation of the density triggers self-sustained oscillations in the flow.The critical heat flux heightens with the higher inlet pressure and pressure drop,larger tube diameter,and lower inlet temperature,but it reduces with the lengthening of the tube.To reflect the density-variation degree for the corresponding heat flux,a dimensionless number N_(tpc)=qπDL/Mβ_(pc)(p)/C_(p,pc)(p)(trans-pseudocritical number)is introduced.The critical trans-pseudocritical number Ntpc,c first goes up and down with the increase of the inlet pressure and the reduction of the inlet temperature.The rise of the mass flow rate,the shortening of the tube length,and the enlargement of the tube diameter all induce the temperature difference along the radial direction to become large.These tendencies make the critical Ntpc,c small.Consequently,the stability boundary N_(tpc,c)=48.47(N_(psc))^(1.048)(Δp∗)^(0.359)(D/L)^(−0.026)(G∗)^(−0.335)(ρ∗)^(2.666) is obtained to distinguish the regions of the flow and heat transfer stability and instability. 展开更多
关键词 supercritical carbon dioxide flow instability vertical heated tube heat transfer and flow
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Frictional resistance of supercritical pressure RP-3 flowing in a vertically downward tube at constant heat fluxes 被引量:1
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作者 Yinlong LIU Guoqiang XU +3 位作者 Yanchen FU Jie WEN Geng GONG Lulu LYU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第9期117-128,共12页
Based on the demands of compact heat exchangers and micro cooling channels applied for aviation thermal protection, the flow resistance characteristics of aviation kerosene RP-3 were experimentally studied in a vertic... Based on the demands of compact heat exchangers and micro cooling channels applied for aviation thermal protection, the flow resistance characteristics of aviation kerosene RP-3 were experimentally studied in a vertically downward circular miniature tube with an inner diameter of 1.86 mm at supercritical pressures and constant heat fluxes. A long and short tube method was used to accurately calculate the frictional pressure drop, and experimental conditions are supercritical pressures of 4 MPa, mass flow rates of 2–4 g/s(i.e., mass fluxes of 736–1472 kg/(m^(2)·s)), heat fluxes of 100–500 kW/m^(2), and inlet temperatures of 373–673 K. Results show that the sharp variations of thermophysical properties, especially density, have significant influences on frictional resistances.Generally, the frictional pressure drop and the friction factor increase with increasing inlet temperatures, and this trend speeds up in the relatively high-temperature region. However, the friction factor has a sudden decline when the fuel outlet temperature exceeds the pseudo-critical temperature.The frictional pressure drop and the friction factor basically remain unchanged with increasing heat flux when the inlet temperature is relatively low, but increase quickly when the inlet temperature is relatively high. Besides, a larger mass flux yields a higher pressure drop but does not necessarily yield a higher friction factor. Finally, an empirical friction factor correlation is proposed and shows better predictive performance than those of previous models. 展开更多
关键词 Aviation kerosene RP-3 Constant heat flux Empirical correlation Friction factor Supercritical pressure vertical tube
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Gas Absorption by Wavy Falling Liquid Film Formed on Inner Surface of Vertical lubes
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作者 Akio Miyara Tomoki Yamamoto +1 位作者 Toru Iemura Takashi Shimada 《Journal of Thermal Science》 SCIE EI CAS CSCD 2003年第1期57-61,共5页
An experimental study on gas absorption into falling liquid film formed on inner surface of vertical tubes has been carried out in order to clarify fundamental characteristics of the gas absorption and enhancement by ... An experimental study on gas absorption into falling liquid film formed on inner surface of vertical tubes has been carried out in order to clarify fundamental characteristics of the gas absorption and enhancement by surface waves. The water supplied into the test tubes is periodically disturbed by fluctuating a silicon tube before the test section with a speaker and the wavy films absorb the oxygen filled in the tubes. Imposing the periodic disturbance enhances the gas absorption and the enhancement has a maximum at around 20-30 Hz, where the gas absorption is 20-30% higher. Mass transfer coefficients obtained with five tubes agree well with those obtained with single tube. Two-dimensional numerical simulations have also been conducted for gas absorption by wavy film and the enhancement mechanism of the gas absorption is discussed. 展开更多
关键词 falling liquid film gas absorption surface wave vertical tube mass transfer enhancement.
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