scholarly journals Development of Optimization Sensitivity Equation by Multiple Linear Regression and Correlation Analysis

2019 ◽  
Vol 4 (12) ◽  
pp. 108-111
Author(s):  
Shadrack Mathew Uzoma
Keyword(s):  
Pressure Drop ◽  
Operating Efficiency ◽  
Gas Pipelines ◽  
Sensitivity Equation ◽  
Pressure Drops ◽  
Frictional Pressure Drop ◽  
Optimal Flow ◽  
Flow Capacity ◽  
The Stability ◽  
Increased Pressure

Gas pipeline pressure-flow problem are affected by varieties of factors notably frictional pressure drop and other pressure drops components. These problems inevitably result in the reduction of the operating efficiency of gas pipelines by virtue of reduction in the line throughput and increased pressure drop along the line. It has been established that increased pressure drop will ultimately lead to increased pump power as well as higher cost of design, construction and operations of gas pipelines. These prevailing factors prompts the need to ascertain the stability and reliability of the optimal flow results. The develop sensitivity model prediction was hinged around ∆L/L (%) being zero. It invariably confirmed that the results of optimal flow capacity are more sensitive to changes in upstream and downstream pressures. It was least sensitive to pressure gradients. The governing conditions being that changes in pipe diameter, ∆D/D (%) and flow capacity, ∆Q/Q (%) were in the order of 5%.

Dimensionless Analysis of Pressure Drop and Heat Transfer on HTGR Coupled With Closed Brayton Cycle

2010 ◽  
Author(s):  
Zhenjia Yu ◽  
Xiaoyong Yang ◽  
Xiaoli Yu ◽  
Jie Wang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Compression Ratio ◽  
High Efficiency ◽  
Great Influence ◽  
Brayton Cycle ◽  
Local Pressure ◽  
Reynolds Analogy ◽  
Pressure Drops ◽  
Frictional Pressure Drop

High temperature gas-cooled reactor with direct helium turbine cycle is based on the closed Brayton cycle. Its outstanding feature is the high efficiency of power generation. Pervious researches showed that recuperator was the key component to promote the cycle’s efficiency. And pressure drops in components were unavoidable in actual projects and had significant influence on cycle efficiency. A dimensionless model was proposed to analyze cycle’s features of HTGR coupled with gas turbine. The parameters’ effect on cycle’s efficiency was analyzed, with full consideration of the frictional and local pressure drops respectively. Under the restriction of materials and state-of-art of technologies, it showed that the cycle’s efficiency depended on compression ratio, recuperator’s effectiveness and pressure drops of components. However the pressure drop ratios of different components were inherently connected due to the closed cycle. Furthermore pressure drops inside the recuperator were also the function of effectiveness of the heat transfer based on the Reynolds analogy. Therefore cycle’s efficiency just depended on recuperator’s effectiveness with fixed compression ratio. So there existed optimal recuperator’s effectiveness and maximum cycle’s efficiency, which varied with the pressure ratio and other parameters as temperature ratio. The calculation also indicated that the pressure drop in pipes was close to that in heat exchangers. That was, the local pressure drop and frictional pressure drop should be considered respectively, and the local pressure drop made quite large reduction of cycle’s efficiency. The result also showed that local pressure drop had great influence on parameters such as optimal compression ratio and recuperator’s effectiveness.

Flow Characteristics and Frictional Pressure Drops of Gas-Liquid Two-Phase Flow in Mini-Micro Pipes and at Vena Contract and Expansion

2007 ◽  
Author(s):  
Hiroyasu Ohtake ◽  
Hideyasu Ohtaki ◽  
Yasuo Koizumi
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Liquid Velocity ◽  
Flow Patterns ◽  
Experimental Results ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop

The frictional pressure drops and two-phase flow patterns of gas-liquid two-phase flow in mini-micro pipes and at vena contract and expansion were investigated experimentally. Test liquid was water; test gas was argon. The diameter of the test mini-pipe was 0.5, 0.25 and 0.12 mm, respectively. The pressure drop data and the flow pattern were collected over 2.1 < Ug < 92.5 m/s for the superficial gas velocity and 0.03 < Ul < 10 m/s for the superficial liquid velocity. The experimental results show that the flow patterns were slug, churn, ring and annular flows; pure bubbly flow pattern was not observed in a range of the present experimental conditions. The two-phase friction multiplier data for D > 0.5 mm showed to be in good agreement with the conventional correlations. On the other hand, the two-phase friction multiplier data for D < 0.25 mm differed from the calculated values by the conventional correlations. Then, thickness of liquid film around a gas plug and size of gas core were estimated and the effect of frictional pressure drop on channel size was discussed through Knudsen Number of gas and instability on liquid-gas interface. The coefficients of sudden enlargement and sudden contraction in mini-pipes for the gas-water two-phase flow were modified from the present experimental results.

Two-Phase Pressure Drop of CO2 in Mini Tubes and Microchannels

2003 ◽  
Author(s):  
R. Yun ◽  
Y. Kim
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Large Diameter ◽  
Two Phase ◽  
Heating Method ◽  
Pressure Drops ◽  
Direct Heating ◽  
Frictional Pressure Drop ◽  
Phase Pressure

Two-phase pressure drops of CO2 are investigated in mini tubes with inner diameters of 2.0 and 0.98 mm and in microchannels with hydraulic diameters from 1.08 to 1.54 mm. For the mini tubes, the tests were conducted with a variation of mass flux from 500 to 3570 kg/m2s, heat flux from 7 to 48 kW/m2, while maintaining saturation temperatures at 0°C, 5°C and 10°C. For the microchannels, mass flux was varied from 100 to 400 kg/m2s, and heat flux was altered from 5 to 20 kW/m2. A direct heating method was used to provide heat into the refrigerants. The pressure drop of CO2 in mini tubes shows very similar trends with that in large diameter tubes. Although the microchannel has a small hydraulic diameter, two-phase effects on frictional pressure drop are significant. The Chisholm parameter of the Lockhart and Martinelli correlation is modified by considering diameter effects on the two-phase frictional multiplier.

scholarly journals Pressure Drops in C02 Supercritical Boilers : 2nd Report Dynamic Characteristics of Frictional Pressure Drop

1979 ◽  
Vol 22 (167) ◽  
pp. 733-739
Author(s):  
Tadashi SAKAGUCHI ◽  
Koji AKAGAWA ◽  
Mamoru OZAWA ◽  
Takafumi ORIGANE
Keyword(s):  
Pressure Drop ◽  
Dynamic Characteristics ◽  
Pressure Drops ◽  
Frictional Pressure Drop

Experimental Investigation of Flow Boiling Pressure Drop of R134A in a Microscale Horizontal Smooth Tube

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Cristiano Bigonha Tibiriçá ◽  
Jaqueline Diniz da Silva ◽  
Gherhardt Ribatski
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Boiling ◽  
Smooth Tube ◽  
Working Fluid ◽  
Prediction Methods ◽  
Internal Diameter ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop

This paper presents new experimental flow boiling pressure drop results in a microscale tube. The experimental data were obtained under diabatic conditions in a horizontal smooth tube with an internal diameter of 2.32 mm. Experiments were performed with R134a as working fluid, mass velocities ranging from 100 kg/m2 s to 600 kg/m2 s, heat flux ranging from 10 kW/m2 to 55 kW/m2, saturation temperatures of 31°C, and exit vapor qualities from 0.20 to 0.99. Flow pattern characterization was also performed from images obtained by high-speed filming. Pressure drop gradients up to 48 kPa/m were measured. These data were carefully analyzed and compared against 13 two-phase frictional pressure drop prediction methods, including both macro- and microscale methods. Comparisons against these methods based on the data segregated according to flow patterns were also performed. Overall, the method by Cioncolini et al. (2009, “Unified Macro-to-Microscale Method to Predict Two-Phase Frictional Pressure Drops of Annular Flows,” Int. J. Multiphase Flow, 35, pp. 1138–1148) provided quite accurate predictions of the present database.

Pressure Drop of Horizontal Air–Water Slug Flow in Different Configurations of Corrugated Pipes

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Ana Luiza B. Santana ◽  
Moisés A. Marcelino Neto ◽  
Rigoberto E. M. Morales
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Industrial Application ◽  
Slug Flow ◽  
Phase Flow ◽  
Dynamic Changes ◽  
Two Phase ◽  
Pressure Drops ◽  
Flow Pressure ◽  
Increased Pressure

Abstract Corrugated pipes (CP) have regularly shaped and spaced cavities on their internal walls that can induce dynamic changes in the flow, such as increased pressure drops. Offshore petroleum production pipelines are an example of an industrial application of CPs, known as flexible lines. Slug flow is the most challenging flow pattern in those lines due to its complex hydrodynamics. A number of previous studies proposed correlations to predict the two-phase flow pressure drops in smooth pipes (SPs). However, limited researches have evaluated the pressure drops associated with liquid–gas slug flow in CPs. In this work, experiments to analyze the pressure drops in horizontal air–water slug flow under different configurations of CPs were carried out. The tests were performed in three different CP internal diameters (IDs) (26, 40, and 50 mm) with different cavity widths (1.2, 1.6, and 2.0 mm). The effects of the internal diameters and the cavity widths on the pressure drops associated with slug flow were analyzed. Results demonstrated that the pressure drops increase with increasing cavity widths. The experimental data were fitted and a pressure drop correlation using the concept of multiplier factor was proposed. Comparisons between predictions and the experimental data proved to be within ±10% accuracy.

Pressure Drop in Circular Two-Phase Pipe Flow As Influenced by the Angle of Inclination

2019 ◽  
Author(s):  
Bethany Worl ◽  
Samuel Nielson ◽  
Xiuling Wang
Keyword(s):  
Pressure Drop ◽  
Two Phase ◽  
Ansys Fluent ◽  
Pressure Drops ◽  
Horizontal Pipes ◽  
Frictional Pressure Drop ◽  
Flow Through ◽  
Two Phases ◽  
Theoretical Pressure ◽  
Experience Difficulty

Abstract A variety of models exist to describe the frictional pressure drop for two-phase flow in a pipe. These models all are based on assumptions and simplifications of the flow regime and can experience difficulty when modeling flow through non-horizontal pipes due to the buoyant effects as the bubbles grow in size. Using computational fluid dynamics, it is possible to model the interaction between the two phases and determine an expected pressure drop. In order to evaluate the effect of the inclination angle of a channel, a parametric study will be conducted using ANSYS Fluent; these predicted pressure drops will then be compared to those found in literature for validation and then to other theoretical pressure drop calculations. Through this study, the benefits of both the theoretical framework and the numerical simulation will be identified.

scholarly journals Entropy Generation for Negative Frictional Pressure Drop in Vertical Slug and Churn Flows

Entropy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 156
Author(s):  
Lei Liu ◽  
Dongxu Liu ◽  
Na Huang
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Energy Loss ◽  
Entropy Generation ◽  
Mechanical Energy ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Pressure Drops ◽  
Frictional Pressure Drop ◽  
Mechanical Energy Loss

It is widely accepted that the frictional pressure drop is impossible to be negative for pipe flow. However, the negative frictional pressure drops were observed for some cases of two-phase slug and churn flows in pipes, challenging the general sense of thermodynamic irreversibility. In order to solve this puzzling problem, theoretical investigations were performed for the entropy generation in slug and churn flows. It is found that the frictional pressure drop along with a buoyancy-like term contributes to the entropy generation due to mechanical energy loss for steady, incompressible slug and churn flows in vertical and inclined pipes. Experiments were conducted in a vertical pipe with diameter as 0.04 m for slug and churn flows. Most of the experimental data obtained for frictional pressure drop are negative at high gas–liquid ratios from 100 to 10,000. Entropy generation rates were calculated from experimental data. The results show that the buoyancy-like term is positive and responsible for a major part of entropy generation rate while the frictional pressure drop is responsible for a little part of entropy generation rate, because of which the overall entropy generation due to mechanical energy loss is still positive even if the frictional pressure drop is negative in vertical slug and churn flows. It is clear that the negative frictional pressure drops observed in slug and churn flows are not against the thermodynamics irreversibility.

scholarly journals Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel

2017 ◽  
Vol 38 (3) ◽  
pp. 101-118 ◽  
Author(s):  
Tomasz Muszyński ◽  
Rafał Andrzejczyk ◽  
Carlos A. Dorao
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Saturation Temperature ◽  
High Speed Camera ◽  
Two Phase ◽  
Pressure Drops ◽  
Adiabatic Flow ◽  
Frictional Pressure Drop ◽  
Mixture Preparation ◽  
Diameter Channel

AbstractThe article presents detailed two-phase adiabatic pressure drops data for refrigerant R134a. Study cases have been set for a mass flux varying from 200 to 400 kg/m2s, at the saturation temperature of 19.4 °C. Obtained experimental data was compared with the available correlations from the literature for the frictional pressure drop during adiabatic flow. Influence of mixture preparation on pressure drop was investigated, for varying inlet subcooling temperature in the heated section. The flow patterns have also been obtained by means of a high-speed camera placed in the visualization section and compared with literature observations.

Experimental Investigation of Flow Boiling Pressure Drop of R134a in a Micro-Scale Horizontal Smooth Tube

2010 ◽  
Author(s):  
Cristiano Bigonha Tibiric¸a´ ◽  
Gherhardt Ribatski
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Boiling ◽  
Smooth Tube ◽  
Working Fluid ◽  
Internal Diameter ◽  
Two Phase ◽  
Pressure Drops ◽  
Micro Scale ◽  
Frictional Pressure Drop

This paper presents new experimental flow boiling pressure drop results in a microscale tube. The experimental data were obtained under diabatic conditions in a horizontal smooth tube with internal diameter of 2.3 mm. Experiments were performed with R134a as working fluid, mass velocities ranging from 100 to 600 kg/m2s, heat flux ranging from 10 to 55 kW/m2, saturation temperatures of 31 °C, and exit vapor qualities from 0.20 to 0.99. Flow pattern characterization was also performed from images obtained by high-speed filming. Pressure drops up to 48 kPa/m were measured. These data were carefully analyzed and compared against 13 two-phase frictional pressure drop prediction methods, including both macro- and micro-scale methods. Comparisons against these methods based on the data segregated according to flow patterns were also performed. Overall, the method by Cioncolini et al. [1] provided quite accurate predictions of the present database.

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