scholarly journals Numerical Simulation Study on Flow Laws and Heat Transfer of Gas Hydrate in the Spiral Flow Pipeline with Long Twisted Band

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 489
Author(s):  
Yongchao Rao ◽  
Lijun Li ◽  
Shuli Wang ◽  
Shuhua Zhao ◽  
Shidong Zhou
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Gas Hydrate ◽  
Pipe Wall ◽  
Heat Transfer Characteristics ◽  
Natural Gas Hydrate ◽  
Spiral Flow ◽  
Transfer Characteristics ◽  
Straight Flow

The natural gas hydrate plugging problems in the mixed pipeline are becoming more and more serious. The hydrate plugging has gradually become an important problem to ensure the safety of pipeline operation. The deposition and heat transfer characteristics of natural gas hydrate particles in the spiral flow pipeline have been studied. The DPM model (discrete phase model) was used to simulate the motion of solid particles, which was used to simulate the complex spiral flow characteristics of hydrate in the pipeline with a long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the spiral flow pipeline were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics, and particle settling characteristics in the pipeline were investigated. The numerical results showed that compared with the straight flow without a long twisted band, two obvious eddies are formed in the flow field with a long twisted band, and the velocities are maximum at the center of the vortices. Along the direction of the pipeline, the two vortices move toward the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the wall. With the same Reynolds number, the twisted rate was greater, the spiral strength was weaker, the tangential velocity was smaller, and the pressure drop was smaller. Therefore, the pressure loss can be reduced as much as possible with effect of the spiral flow. In a straight light flow, the Nusselt number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusselt number gradually decreased toward the pipe wall at the maximum, and at the near wall, the attenuation gradient of the Nu number was large. For spiral flow, the curve presented by the Nusselt number was a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nusselt number becomes larger. Therefore, the spiral flow can make the temperature distribution more even and prevent the large temperature difference, resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same condition, the spiral flow carried hydrate particles at a distance about 3–4 times farther than that of the straight flow.

scholarly journals Numerical Simulation of Spiral Flow and Heat Transfer in Hydrate Pipeline With Long Twisted Band

2020 ◽  
Author(s):  
Yongchao Rao ◽  
Lijun Li ◽  
Shuli Wang ◽  
Shuhua Zhao ◽  
Shidong Zhou
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Field ◽  
Pipe Wall ◽  
Large Temperature ◽  
Heat Transfer Characteristics ◽  
Spiral Flow ◽  
Light Pipe ◽  
Transfer Characteristics ◽  
Straight Flow

Abstract The DPM model (discrete phase model) considering the motion of solid particles was used to simulate the complex spiral flow characteristics of hydrate in the pipe spinning up with long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the pipe spiral flow were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics and particle settling characteristics of the flow field in the pipeline were investigated. The numerical results show that, compared with the straight flow of light pipe without twisted band, two obvious eddies are formed in the flow field under the spinning action of twisted band, and the velocities are maximum at the center of the eddies. Along the direction of the pipe, the two vortices move towards the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the pipe wall. With the same Reynolds number, the greater the twist ratio, the weaker the spiral strength, the smaller the tangential velocity of the spiral flow, and the smaller the pressure drop of the pipe. Therefore, the pressure loss can be reduced as much as possible while ensuring the spinning effect of the spiral flow. In a straight light pipe flow, the Nusser number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusser number gradually decreases towards the pipe wall at the maximum, and at the near wall, the attenuation gradient of Nu is large. For spiral flow, the curve presented by Nusserr number shows a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nussel number becomes larger and larger. Therefore, the spiral flow can make the temperature distribution in the flow field in the pipeline more even, and prevent the large temperature difference resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same working condition, the spiral flow carries hydrate particles at a distance about 3-4 times that of the straight flow.

Heat Transfer and Flow Structure in a Latticework Duct With Different Sidewalls

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Wei Du ◽  
Lei Luo ◽  
Songtao Wang ◽  
Jian Liu ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Flow Structure ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Pressure Side ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Abstract Heat transfer characteristics in a latticework duct with various sidewalls are numerically investigated. The crossing angle is 90 deg and the number of subchannels is eleven on both the pressure side and suction side for each latticework duct. The thickness of the ribs is 8 mm and the distance between adjacent ribs is 24 mm. The investigation is conducted for various Reynolds numbers (11,000 to 55,000) and six different sidewalls. Flow structure, pressure drop, and heat transfer characteristics are analyzed. Results revealed that the sidewall has significant effects on heat transfer and flow structure. The triangle-shaped sidewall provides the highest Nusselt number accompanied by the highest friction factor. The sidewall with a slot shows the lowest friction factor and Nusselt number. An increased slot width decreased the Nusselt number and friction factor simultaneously.

Pressure Drop and Heat Transfer Characteristics for Partially-Confined Heat Sinks in Ducted Flow

2006 ◽  
Author(s):  
H. T. Chen ◽  
T. Y. Wu ◽  
P. L. Chen ◽  
S. F. Chang ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Heat Sinks ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Effective Friction

The pressure drop and heat transfer characteristics for partially-confined heat sinks with different fin types, including plain-plate fin, pin-fin array and strip-fin array, in ducted flow are investigated. The main focus of the experimental results is on pressure drop and heat transfer characteristics of generalized heat sink in ducted flow with considering the flow top- and side-bypass effects. The parameters controlled in the study are the heating load (Qt), inlet flow velocity (Ui), the ratio of heat sink height to duct height (Hs/Hc), and the ratio of heat sink width to duct width (Ws/Wc). The ranges of parameters studied are Ui=2~12m/s, Qt=10~30W, Ws/Wc = 0.6~1, and Hs/Hc = 0.5~1. In the present study, an effective friction factor related to the overall pressure drop is defined; and a new experimental correlation for the effective friction factor for generalized heat sinks in ducted flow with top- and side-bypass effects is presented. A satisfactory agreement between the experimental data and the theoretical predictions is achieved with the maximum and average deviations of 17.2% and 9.6%, respectively. As for convective heat transfer performance, the average Nusselt number is not significantly affected by Grashof number; while, it increases significantly with increasing Reynolds number. Furthermore, the thermal performance increases with increasing top or side confinement ratio (Hs/Hc or Ws/Wc). The best thermal performance occurred at the fully-confined condition, i.e., Hs/Hc=1, Ws/Wc = 1. Based on all the experimental data for three types of partially-confined heat sinks, a generalized correlation of average Nusselt number for partially-confined heat sinks in ducted flow in terms of Re, Hs/Hc and Ws/Wc is presented. The maximum and average deviations of the results obtained by the experimental data from the theoretical prediction are 12.4% and 7.5%, respectively.

scholarly journals Uncertainties Analysis on the Prediction of Flow and Heat Transfer of Liquid Sodium with CFD Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhanwei Liu ◽  
Xinyu Li ◽  
Tenglong Cong ◽  
Rui Zhang ◽  
Lingyun Zheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Liquid Sodium ◽  
Heat Transfer Characteristics ◽  
Backward Facing Step ◽  
Heating Wall ◽  
Transfer Characteristics ◽  
Cfd Models ◽  
Flow And Heat Transfer

The prediction of flow and heat transfer characteristics of liquid sodium with CFD technology is of significant importance for the design and safety analysis of sodium-cooled fast reactor. The accuracies and uncertainties of the CFD models should be evaluated to improve the confidence of the numerical results. In this work, the uncertainties from the turbulent model, boundary conditions, and physical properties for the flow and heat transfer of liquid sodium were evaluated against the experimental data. The results of uncertainty quantization show that the maximum uncertainties of the Nusselt number and friction coefficient occurred in the transition zone from the inlet to the fully developed region in the circular tube, while they occurred near the reattachment point in the backward-facing step. Furthermore, in backward-facing step flow, the maximum uncertainty of temperature migrated from the heating wall to the geometric center of the channel, while the maximum uncertainty of velocity occurred near the vortex zone. The results of sensitivity analysis illustrate that the Nusselt number was negatively correlated with the thermal conductivity and turbulent Prandtl number, while the friction coefficient was positively correlated with the density and Von Karman constant. This work can be a reference to evaluate the accuracy of the standard k-ε model in predicting the flow and heat transfer characteristics of liquid sodium.

Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

2021 ◽  
pp. 095440622110272
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Litan Kumar Saha ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

Heat Transfer Characteristics of the Phase Change Material Microcapsule Slurry in Solid Phase State

2011 ◽  
Vol 71-78 ◽  
pp. 1187-1190
Author(s):  
Yan Lai Zhang ◽  
Zhong Hao Rao ◽  
Shuang Feng Wang ◽  
Hong Zhang ◽  
Li Jun Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Phase State ◽  
Solid Phase ◽  
Heat Transfer Characteristics ◽  
Rectangular Enclosure ◽  
Transfer Characteristics ◽  
Change Material

This experiment is performed to investigate heat transfer characteristics with the PCM microcapsule slurry in a solid phase state at a horizontal rectangular enclosure heating from below and cooling from top. Some important parameters are taken into account such as the mass concentration of the PCM, the temperature difference between heating plate and cooling plate, Nusselt number Nu, Rayleigh number Ra and the aspect ratio (width/height) of the horizontal rectangular enclosure. Experiment is done under the thermal steady condition in the PCM microcapsule slurry. Heat transfer coefficient is measured under various temperature differences in PCM mass concentrations of 10% and 20%. And relationship with Nusselt number Nu and Rayleigh number Ra is summarized to various heights H or the aspect ratio (width/height) Ar of enclosure.

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