Pressure Gradient Variations During Reflux Condensation in a Closed Thermosyphon

2009 ◽  
Author(s):  
Siamak Moaveninejad ◽  
Mohammad Mahdi Heyhat
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Integral Method ◽  
Species Conservation ◽  
Mass Conservation ◽  
Continuous Model ◽  
Mass Energy ◽  
Vapor Interface ◽  
Front Model ◽  
Thermodynamic Equilibrium Condition

The heat and mass transfer in the condenser region of a variable conductance thermosyphon, consisting of two components (R11 + R113) has been studied and special attention has been devoted to pressure drop during reflux condensation. The mass, energy, and species conservation equations in conjunction with the overall mass conservation and continuity of momentum at liquid-vapor interface constraints and the thermodynamic equilibrium condition have been solved numerically by use of the integral method. In contrast to the flat-front model which assumes a sharp interface between the active and shut-off portions in a variable conductance thermosyphon, in this paper a continuous model has been used. In this model a continuous variation of physical properties with condensation of both components along condenser is assumed. The results of the present study have been compared with available numerical and experimental results of other investigators and pressure gradient profiles have been achieved. A calculation of the frictional, accelerational and gravitational components of the pressure drop shows that the gravitational component has the greatest magnitude due to the relatively high density of the vapor.

Steady Two-Dimensional Heat and Mass Transfer in the Vapor-Gas Region of a Gas-Loaded Heat Pipe

1973 ◽  
Vol 95 (3) ◽  
pp. 377-382 ◽  
Author(s):  
A. R. Rohani ◽  
C. L. Tien
Keyword(s):  
Mass Transfer ◽  
Heat Pipe ◽  
Heat And Mass Transfer ◽  
Species Conservation ◽  
Heat Pipes ◽  
Mass Conservation ◽  
Gas Diffusion ◽  
Two Dimensional ◽  
Axial Conduction ◽  
Thermodynamic Equilibrium Condition

A numerical analysis is made of the steady two-dimensional heat and mass transfer in the vapor-gas region of a gas-loaded heat pipe. Consideration is given to a cylindrical heat pipe with typical evaporator, condenser, and noncondensible-gas sections and with negligible axial conduction through the wall and the liquid-wick matrix. The elliptical mass, momentum, energy, and species conservation equations have been solved in conjunction with the overall energy and mass conservation constraints and the thermodynamic equilibrium condition for three heat pipe cases with different working fluids and diameters. The results show that in certain gas-loaded heat pipes, such as liquid-metal heat pipes, vapor-gas diffusion and two-dimensionality must be considered in the analysis. Extension of the present numerical framework to more general cases such as including the axial wall conduction is indicated.

Study on the Flow Characteristics of Shengli Oilfield Super Heavy Oil

2017 ◽  
Vol 10 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Wang Shou-long ◽  
Li Ai-fen ◽  
Peng Rui-gang ◽  
Yu Miao ◽  
Fu Shuai-shi
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Heavy Oil ◽  
Flow Characteristics ◽  
Fluid Viscosity ◽  
Linear Flow ◽  
Start Up ◽  
Non Linear ◽  
Core Permeability ◽  
Velocity Pressure

Objective:The rheological properties of oil severely affect the determination of percolation theory, development program, production technology and oil-gathering and transferring process, especially for super heavy oil reservoirs. This paper illustrated the basic seepage morphology of super heavy oil in micro pores based on its rheological characteristics.Methods:The non-linear flow law and start-up pressure gradient of super heavy oil under irreducible water saturation at different temperatures were performed with different permeable sand packs. Meanwhile, the empirical formulas between start-up pressure gradient, the parameters describing the velocity-pressure drop curve and the ratio of gas permeability of a core to fluid viscosity were established.Results:The results demonstrate that temperature and core permeability have significant effect on the non-linear flow characteristics of super heavy oil. The relationship between start-up pressure gradient of oil, the parameters representing the velocity-pressure drop curve and the ratio of core permeability to fluid viscosity could be described as a power function.Conclusion:Above all, the quantitative description of the seepage law of super heavy oil reservoir was proposed in this paper, and finally the empirical diagram for determining the minimum and maximum start-up pressure of heavy oil with different viscosity in different permeable formations was obtained.

scholarly journals A Mass- and Energy-Conserving Numerical Model for a Fractional Gross–Pitaevskii System in Multiple Dimensions

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1765
Author(s):  
Adán J. Serna-Reyes ◽  
Jorge E. Macías-Díaz
Keyword(s):  
Initial Conditions ◽  
Type System ◽  
Continuous System ◽  
Mass Conservation ◽  
Continuous Model ◽  
Manuscript Studies ◽  
Multiple Dimensions ◽  
Negative Constant ◽  
Energy Conserving ◽  
Finite Difference Discretization

This manuscript studies a double fractional extended p-dimensional coupled Gross–Pitaevskii-type system. This system consists of two parabolic partial differential equations with equal interaction constants, coupling terms, and spatial derivatives of the Riesz type. Associated with the mathematical model, there are energy and non-negative mass functions which are conserved throughout time. Motivated by this fact, we propose a finite-difference discretization of the double fractional Gross–Pitaevskii system which inherits the energy and mass conservation properties. As the continuous model, the mass is a non-negative constant and the solutions are bounded under suitable numerical parameter assumptions. We prove rigorously the existence of solutions for any set of initial conditions. As in the continuous system, the discretization has a discrete Hamiltonian associated. The method is implicit, multi-consistent, stable and quadratically convergent. Finally, we implemented the scheme computationally to confirm the validity of the mass and energy conservation properties, obtaining satisfactory results.

Venting and Other Building Practices as Practical Means of Reducing Damage from Tornado Low Pressures

1958 ◽  
Vol 39 (1) ◽  
pp. 14-20 ◽  
Author(s):  
George W. Reynolds
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Maximum Pressure ◽  
Pressure Reduction ◽  
Safe Level ◽  
Air Space ◽  
Run Up ◽  
Low Pressures ◽  
Tornado Forces

Estimates of the pressure reduction in the tornado vortex run up to one-half an atmosphere. The greatest officially reported pressure drop associated with tornadoes has been 0.65 inch (mercury). There is an unofficially reported drop of around five inches. No one can say what the maximum pressure gradient in a tornado is. It is believed that a venting area of one square foot per 1000 cubic feet of air space should be enough to reduce the pressure gradient that most buildings will experience in tornadoes to a safe level. It is also believed that anchorage of the building to the foundation, anchorage of the roof to the building, and better connections at corners will make a house strong enough to resist most tornado forces successfully.

scholarly journals Drag Reduction with Biopolymer-Synthetic Polymer Mixtures in Oil-Water Flows: Effect of Synergy

2020 ◽  
Vol 24 (6) ◽  
pp. 1-10
Author(s):  
Lawrence Chukwuka Edomwonyi-Otu ◽  
Muhammed Muhammed Gimba ◽  
Nurudeen Yusuf
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Pressure Gradient ◽  
Drag Reduction ◽  
Water Flow ◽  
Transport Systems ◽  
Test Fluid ◽  
Polymer Mixture ◽  
Water Flows ◽  
Oil Water

The search for lower cost materials that reduce pressure drop in fluid transport systems in oil and gas industries to conserve pumping energy is of paramount importance. Polymers are known to reduce pressure drop in pipeline oil-water flows in a process referred to as drag reduction (DR). The effect of partially hydrolysed polyacrylamide, polyethylene oxide, Aloe Vera mucilage and their mixtures as drag reducing polymers (DRPs) on pressure gradient (pressure drop; Δp) in pipeline oil-water flows were studied. The experiment was carried out in flow rig with 0.02-m diameter straight unplasticised polyvinylchloride (uPVC) pipe, two centrifugal pumps, control valves and two storage tanks. Tap water (ρ = 997 kg/m3 and µ = 0.89 cP) and diesel (ρ = 832 kg/m3 and µ = 1.66 cP) were used as the test fluid at ambient condition. The polymer mixture total concentration (MTC) of 30 and 400 ppm at different mixing proportion, mixture Reynolds number (Remix) and oil input volume were investigated. The results show increase in pressure gradient with increase in oil input volume in both single-phase water flow and oil-water flow before adding drag reducing polymers (DRPs). However, Δp decreased after adding DRPs with increase in Reynolds number (Re) or Remix and decrease in the oil-phase Re, and vice versa. The results further showed higher reduction in pressure drop by the polymer mixture than in each of the polymer used at the same conditions. The rigidness of the biopolymer was improved by adding synthetic polymers which resulted to increase in DR efficiency.

scholarly journals A Study of Pressure Gradient in Multiphase Flow in Vertical Pipes

2019 ◽  
Vol 4 (1) ◽  
pp. 54-59
Author(s):  
David Nwobisi Wordu ◽  
Felix J. K. Ideriah ◽  
Barinyima Nkoi
Keyword(s):  
Pressure Drop ◽  
Multiphase Flow ◽  
Pressure Gradient ◽  
Performance Optimization ◽  
Field Data ◽  
Oil And Gas ◽  
Liquid Velocity ◽  
Petroleum Industry ◽  
Well Performance ◽  
Flowing Fluid

The study of multiphase flow in vertical pipes is aimed at effective and accurate design of tubing, surface facilities and well performance optimization for the production of oil and gas in the petroleum industry by developing a better approach for predicting pressure gradient. In this study, field data was analyzed using mathematical model, multiphase flow correlations, statistical model, and computer programming to predict accurately the flow regime, liquid holdup and pressure drop gradient which are important in the optimization of well. A Computer programme was used to prediction pressure drop gradient. Four dimensionless parameters liquid velocity number (Nlv), gas velocity number (Ngv), pipe diameter number (Nd), liquid viscosity number (Nl), were chosen because they represent an integration of the two dominant components that influence pressure drop in pipes. These dominant component are flow channel/media and the flowing fluid. The model was found to give a fit of 100% to the selected data points. Hagedorn & Brown, Griffith &Wallis correlations and model were compared with field data and the overall pressure gradient for a total depth of 10000ft was predicted. The predicted pressure gradient measured was found to be 0.320778psi/ft, Graffith& Wallis gave 0.382649Psi/ft, Hagedorn & Brown gave 0.382649Psi/ft; whereas generated model gave 0.271514Psi/ft. These results indicate that the model equation generated is better and leads to a reasonably accurate prediction of pressure drop gradient according to measured pressure gradient.

scholarly journals Finite Volume approximation of a two-phase two fluxes degenerate Cahn-Hilliard model

2021 ◽  
Author(s):  
Clément Cancès ◽  
Flore Nabet
Keyword(s):  
Finite Volume ◽  
Mass Conservation ◽  
Continuous Model ◽  
Finite Volume Scheme ◽  
Two Phase ◽  
Existence Of A Solution ◽  
Entropy Dissipation ◽  
Continuous Problems ◽  
Volume Approximation ◽  
Compactness Arguments

We study a time implicit Finite Volume scheme for degenerate Cahn-Hilliard model proposed in [W. E and P. Palffy-Muhoray. Phys. Rev. E , 55:R3844–R3846, 1997] and studied mathematically by the authors in [C. Canc\`es, D. Matthes, and F. Nabet. Arch. Ration. Mech. Anal. , 233(2):837-866, 2019]. The scheme is shown to preserve the key properties of the continuous model, namely mass conservation, positivity of the concentrations, the decay of the energy and the control of the entropy dissipation rate. This allows to establish the existence of a solution to the nonlinear algebraic system corresponding to the scheme. Further, we show thanks to compactness arguments that the approximate solution converges towards a weak solution of the continuous problems as the discretization parameters tend to 0. Numerical results illustrate the behavior of the numerical model.

scholarly journals Hagen number versus Bejan number

2013 ◽  
Vol 17 (4) ◽  
pp. 1245-1250 ◽  
Author(s):  
Mohamed Awad
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Poiseuille Flow ◽  
Physical Meaning ◽  
Characteristic Length ◽  
Bejan Number ◽  
Reynolds Analogy ◽  
Dimensionless Pressure ◽  
Flow Length

This study presents Hagen number vs. Bejan number. Although their physical meaning is not the same because the former represents the dimensionless pressure gradient while the latter represents the dimensionless pressure drop, it will be shown that Hagen number coincides with Bejan number in cases where the characteristic length (l) is equal to the flow length (L). Also, a new expression of Bejan number in the Hagen-Poiseuille flow will be introduced. At the end, extending the Hagen number to a general form will be presented. For the case of Reynolds analogy (Pr = Sc = 1), all these three definitions of Hagen number will be the same.

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