scholarly journals Effects of Fluid Viscoelasticity in Non-Isothermal Flows

10.5772/21299 ◽  
2011 ◽  
Author(s):  
Tirivanhu Chinyoka
Keyword(s):  
Isothermal Flows

scholarly journals A Simple Construction of a Thermodynamically Consistent Mathematical Model for Non-Isothermal Flows of Dilute Compressible Polymeric Fluids

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 133
Author(s):  
Mark Dostalík ◽  
Josef Málek ◽  
Vít Průša ◽  
Endre Süli
Keyword(s):  
Finite Amplitude ◽  
Homogeneous State ◽  
Cauchy Stress ◽  
Polymeric Fluids ◽  
Classical Models ◽  
Explicit Formulae ◽  
Isothermal Flows ◽  
Elementary Manner ◽  
Production Mechanisms ◽  
Thermodynamic Basis

We revisit some classical models for dilute polymeric fluids, and we show that thermodynamically consistent models for non-isothermal flows of these fluids can be derived in a very elementary manner. Our approach is based on the identification of energy storage mechanisms and entropy production mechanisms in the fluid of interest, which, in turn, leads to explicit formulae for the Cauchy stress tensor and for all of the fluxes involved. Having identified these mechanisms and derived the governing equations, we document the potential use of the thermodynamic basis of the model in a rudimentary stability analysis. In particular, we focus on finite amplitude (nonlinear) stability of a stationary spatially homogeneous state in a thermodynamically isolated system.

Isothermal Flows in Water

1977 ◽  
Vol 11 (2) ◽  
pp. 59-61
Author(s):  
Melam P. Ranga Rao ◽  
Niranjan K. Purohit
Keyword(s):  
Isothermal Flows

Three-Dimensional Molecular Dynamic Study on Accommodation Coefficients in Rough Nanochannels

2009 ◽  
Author(s):  
Jun Sun ◽  
Zhixin Li
Keyword(s):  
Molecular Dynamic ◽  
Three Dimensional ◽  
Dynamic Study ◽  
Wall Effects ◽  
Argon Gas ◽  
Statistical Algorithm ◽  
Lattice Arrangement ◽  
Accommodation Coefficients ◽  
Isothermal Flows ◽  
Wall Interactions

To understand the wall effects in nanochannels, the accommodation coefficients for argon gas in platinum walls were calculated according to a proper statistical algorithm in three-dimensional MD method in isothermal flows and thermal conductions. In smooth channels, the wall lattice arrangement may induce atomic roughness on the surface so that the accommodation coefficients were different for different lattice configurations. While in nanochannels with hemispherical nanoscale rough cells, the roughness increased the possibility of multiple gas-wall interactions. The NMAC in rough channels was less than unity and decreased with larger roughness. Meanwhile, the TMAC in the isothermal flows and the EAC in the thermal conductions in rough channels were larger than those in smooth channels, and they both increased with larger roughness.

Study on the Minimum Drag Coefficient Phenomenon of Supercritical Pressure Water in the Pseudocritical Region

2012 ◽  
Author(s):  
Xianliang Lei ◽  
Huixiong Li ◽  
Shuiqing Yu ◽  
Yifan Zhang ◽  
Tingkuan Chen
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Drag Coefficient ◽  
Supercritical Pressure ◽  
Pressure Drops ◽  
Minimum Drag ◽  
Wide Range ◽  
Pressure Water ◽  
Isothermal Flows ◽  
Supercritical Pressure Water

With the development of supercritical (and even ultra-supercritical) pressure boilers (SCBs) with high capacities, and at the same time, with the consideration of supercritical pressure water-cooled reactors (SCWRs) as one of the six most promising reactor concepts accepted in the Generation IV International Forum (GIF), flow and heat transfer of supercritical water becomes more and more important for both the design and operation safety of the related facilities. Thermo-hydraulic characteristics are among the issues, which are of special significance for the SCBs and SCWRs. It has been found that at supercritical pressures, the hydraulic resistance of water exhibits special characteristics in regions near its pseudo-critical point, which is hereafter called the minimum drag coefficient phenomenon. Experimental investigation was carried out in the present study to investigate further the characteristics of drag coefficient of supercritical pressure water under different conditions. The total pressure drop characteristic of water flowing in smooth tube and internally ribbed tube under the supercritical pressures was measured in experiments with a wide range of operational parameters, such as the system pressures ranging from 23 to 28 MPa, the average heat fluxes varied from 100 kW/m2 to 500kW/m2, and the mass fluxes of water in a range of 600 ∼ 1050 kg/m2s. The experimental data were compared with prediction results calculated by existing common correlations for single phase pressure drops, and large discrepancies were observed between the experimental data and the prediction results. Furthermore, the pressure drops characteristics of supercritical pressure water in cases with different tube arrangement and test conditions were compared with each other, such as that in horizontal tubes and vertical tubes, and that in isothermal flows and in non-isothermal flows. Additionally, this phenomenon observed in the present studies was also analyzed by using computational fluid dynamics technology, and the mechanism of pressure drop variation was reasonably explained. It was found that the deviation appeared between the previously proposed drag coefficient correlations and the present experimental data was mainly owning to ignoring the variation of an existence of the minimum drag coefficient in the pseudo critical region in previous studies, and based on the data obtained in this study, a new correlation for drag coefficient for supercritical pressure water was presented.

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