Decrease In Pressure Drop Research Articles

Effect of chamfer geometry on the pressure drop of perforated plates with thin orifices

Perforated plates with thin orifices is one of the options under considerations to be used in the debris filtering bottom end pieces for the next generation of fuel assemblies for the Brazilian nuclear plants. The increase in pressure drop can be drastically reduced by optimizing the chamfer geometries. This paper describes the development and validation of a procedure devised to use Computational Fluid Dynamics (CFD) to accurately estimate the pressure drop of water flow through perforated plates with chamfered thin orifices. The procedure comprises a scaled down calculation domain, grid configuration and a set of numerical solution parameters. The validation was performed against experiments with a set of plates with different chamfer geometric features like position (inlet, outlet and both sides), angles and sizes. Three turbulence models were evaluated with the standard k–ɛ giving the best result. For the range of parameters evaluated here the pressure drop decrease of a two sided chamfer plate can be estimated as a sum of both inlet and outlet chamfers individually. In both cases the pressure drop decreases rapidly for small chamfers and more slowly for larger chamfers. In the flat regions the chamfer angle has little influence at the inlet and is more important at outlet

Effect of Unconsumed Mixed Small Coke on Permeability in Lower Part of Blast Furnace

Utilization of small coke in the blast furnace was carried out to improve the permeability in the lower part of the blast furnace. However, at high small coke rates, it was thought that some small coke continues to exist in the lower part of the blast furnace because the small coke charging rate is larger than the gasification reaction rate of the small coke. Therefore, the effect of the small coke rate on permeability in the lower part of the blast furnace was investigated. At high small coke rates, residual small coke with a reduced particle size counted to exist in the lower part of the blast furnace after the coke gasification reaction, and the average particle diameter of the coke and the void fraction of the coke packed bed in the lower part of the blast furnace decreased. It was estimated that the increase in the pressure drop of the coke packed bed in the lower part of the blast furnace was larger than the decrease in pressure drop in the cohesive zone, and as a result, the pressure drop in the lower part of the blast furnace increased.

0516 貫流式波力タービンに関する数値的試作

Cross flow turbines for the Oscillating water column were simulated by LES analysis. The equations are discretized by Finite volume method for space and Fractional step method for time. In this study, blade number is 24 and chord length is 15% of diameter. Shapes of duct are point symmetry. Important parameters of ducts are curvature and position of tongue. The following are results of analysis. Gentle curvature of tongue decrease pressure drop and improve turbine efficiency. Maximum efficiency in steady flow was 72%. Starting torque performances were very good in every case.

A CFD pressure drop model for microfibrous entrapped catalyst filters using micro-scale imaging

A micro-scale pressure drop model for microfibrous entrapped catalysts (MFEC) is constructed based on experimental scanning electron microscope (SEM) images using computational fluid dynamics (CFD). This model investigates the separate contributions of fibers, entrapped particles, particle shape factors and the compressibility of MFEC to the total pressure drop in a high air velocity condition. A theoretical calculation is conducted to determine the flow type within the MFEC. Top view and side view SEM images of MFEC are taken to reproduce their 3D geometric structure, which significantly improves the accuracy of the model compared with other simplified models. Volume loading of fibers and entrapped particles, as well as media compressibility, are found to be major contributors to pressure drop. In an effort to reduce pressure drop, two types of leading-edge/trailing-edge filter fairings are also studied. Triangle fairings added to the leading edge and trailing edge of MFEC decrease pressure drop, especially at higher face velocities.

Effect of turbulence intensity on the pressure drop and heat transfer in a staggered tube bundle heat exchanger

This paper investigates experimentally the correlation and the effect of the turbulence intensity on the pressure drop and the heat transfer mechanism of a heat exchanger with elliptic tubes in a staggered arrangement. The heat exchanger studied in this work is an air–water cross flow heat exchanger with air being the external fluid and water the internal one. The heat exchanger consists of 144 elliptic tubes placed in a staggered arrangement. The experiments were carried out for two setups. The first setup was referring to isothermal conditions for which only air was used, flowing around the tubes. The second setup was referring to non-isothermal conditions with air as the external fluid and water as the internal working fluid, flowing inside the tubes. The Reynolds number for the external air for the isothermal experiments ranged between 3100 and 5200 based on the maximum velocity between the elliptic tubes. The turbulence intensity values varied between 0.9% and 3%. For the non-isothermal measurements the Reynolds number took values from 3100 to 7700 and the turbulent intensity ranged from 0.9% to 3%. The measurements showed that the increase of turbulent intensity led to a decrease in the total pressure drop of the external flow of the heat exchanger together with an enhancement of the heat transfer mechanism.

Analyses on Effect of Helix Angle on the Continuous Helical Baffles Heat Exchanger

A numerical simulation for heat exchanger with continuous helical baffles was carried out. The study focuses on the effects of helix angle on heat transfer characteristics. The results show that both the shell-side heat transfer coefficient and pressure drop decrease with the increase of the helix angle at certain mass flow rate. The latter decreases more quickly than the former. The tangential velocity distribution on shell-side cross section is more uniform with continuous helical baffles than with segmental baffles. The axial velocity at certain radial position decreases as the helix angle increases in the inner region near the central dummy tube, whereas it increases as the helix angle increases in the outer region near the shell. The heat exchange quantity distribution in tubes at different radial positions is more uniform at larger helix angel.

Effects of entrance convergence angle and fiber content on the rheological properties of Pithecellobium clypearia fiber/high-density polyethylene composites

The entrance converging flow method was used to investigate the influences of entrance convergence angle and fiber content on the rheological behavior of Pithecellobium clypearia fiber (PCF)/high-density polyethylene (HDPE) composites. Shear and extensional rheological parameters were also measured. It is found that the extensional action exerted on the materials reaches a maximum at a die angle of 120° at certain plunger rates. Wall slippage occurs easily for PCF/HDPE composites with higher fiber content with a die entry angle of 120°, causing a substantial decrease in the entrance pressure drop of the orifice die. Both shear and extensional non-Newtonian indices of HDPE and PCF/HDPE composites were less than 1, consistent with shear- and tension-thinning rheological behavior. Within the fiber content range used in this study, the shear viscosity increased slightly with fiber content, while the extensional viscosity decreased initially and then increased with increasing fiber content.

Theoretical Studies on the Application of Pulsating Heat Pipe in Vapour Compression Refrigeration System

This paper proposes a simplified theoretical model of Pulsating Heat Pipe (PHP) employed in a vapour compression refrigeration system. The model developed is mainly based on well known physical equations and partially based on empirical correlation. The present theoretical investigation of PHP is focused to explore its suitability as a heat exchanger in the condenser of vapour compression refrigeration system. A parametric analysis is carried out to design the vapour compression refrigeration system with PHP as the condenser. The performance of the system is evaluated for different PHP diameters, working fluids, evaporator and condenser temperatures and evaporator and condenser lengths. The effect of super heating and sub cooling the refrigerant are also studied. The results showed an increase in performance of the system at higher evaporator and lower condenser temperatures. The best results are obtained with R-12 as the working fluid. Also there is an increase in the COP of the system due to decrease in pressure drop in the condenser.

Effect of Adsorbent Diameter on the Performance of Adsorption Refrigeration

Adsorbents are important components in adsorption refrigeration. The diameter of an adsorbent can affect the heat and mass transfer of an adsorber. The effect of particle diameter on effective thermal conductivity was investigated. The heat transfer coefficient of the refrigerant and the void rate of the adsorbent layer can also affect the effective thermal conductivity of adsorbents. The performance of mass transfer in the adsorber is better when pressure drop decreases. Pressure drop decreases with increasing permeability. The permeability of the adsorbent layer can be improved with increasing adsorbent diameter. The effect of adsorbent diameter on refrigeration output power was experimentally studied. Output power initially increases and then decreases with increasing diameter under different cycle time conditions. Output power increases with decreasing cycle time under similar diameters.

Flow fluctuation behaviors of single-phase forced circulation under rolling conditions

Marine reactors are received increasing attention recently in the field of ocean engineering. The effect of platform motion on the coolant flow of an offshore nuclear power plants is very complicated, which is required further analysis. In this paper, effects of rolling motion on single-phase flow fluctuation with different loops were investigated experimentally. And a mathematical model was also developed to study the mechanism of the influence of rolling motion on flow fluctuation with different pressure head, rolling parameters and layouts of flow loops. For the closed loop, the flow rate was adjusted by two ways, i.e. regulating the pump rotation speed and changing the state of regulating valve. While for the opened loop, the pressure head was always supplied by elevated water tank. The Reynolds number ranged from 300 to 8000, and ranges of the rolling period and amplitude were 8–20s and 10–30°, respectively. The results show that increase of the loop resistance and pressure head results in smaller flow fluctuation amplitudes. Effects of rolling motion on single-phase flow fluctuation weaken as the oscillatory pressure drop decreases or the pressure head increases. If the pressure head is high enough, the effect of rolling motion on flow fluctuation could be neglected. Rolling motions influence the flow fluctuation behaviors in different ways for the opened loop and the closed loop, due to the inequable oscillatory pressure drop. The flow fluctuation model shows a good agreement with the experiments and the analyzing method is expected to other oscillating flow system.

An approach to evaluate Venturi-device effects on gas wells production

Abstract This paper presents a theoretical analysis of the effect produced by Venturi devices in gas wells. The first part of our methodology consists of performing steady-state simulations to fit experimental and theoretical pressure profiles. These simulations were carried out in Aspen Plus® to reproduce gas production in wells. The results in our case study have indicated that the flow pattern corresponds to a mist type. Then CFD simulations have been used to reproduce the gas–liquid flow through a Venturi device based on ANSYS CFX®. It has been observed that the Venturi increases the gas volume fraction and easy formation of smaller bubbles, which tend to flow in the center of the well. CFD simulations were carried out assuming an Eulerian–Eulerian approach for the bubbles dispersion through the Venturi device. The RNG k–e model and the homogeneous MUSIG model are used to include the turbulence effect and to represent the bubbles population balance, respectively. Thus the numerical evidence indicates that Venturi-devices promote a flow pattern where the pressure drop decreases and hence it can increase the gas production in certain types of gas wells.

Nanocomposite Electrospun Nanofiber Membranes for Environmental Remediation.

Rapid worldwide industrialization and population growth is going to lead to an extensive environmental pollution. Therefore, so many people are currently suffering from the water shortage induced by the respective pollution, as well as poor air quality and a huge fund is wasted in the world each year due to the relevant problems. Environmental remediation necessitates implementation of novel materials and technologies, which are cost and energy efficient. Nanomaterials, with their unique chemical and physical properties, are an optimum solution. Accordingly, there is a strong motivation in seeking nano-based approaches for alleviation of environmental problems in an energy efficient, thereby, inexpensive manner. Thanks to a high porosity and surface area presenting an extraordinary permeability (thereby an energy efficiency) and selectivity, respectively, nanofibrous membranes are a desirable candidate. Their functionality and applicability is even promoted when adopting a nanocomposite strategy. In this case, specific nanofillers, such as metal oxides, carbon nanotubes, precious metals, and smart biological agents, are incorporated either during electrospinning or in the post-processing. Moreover, to meet operational requirements, e.g., to enhance mechanical stability, decrease of pressure drop, etc., nanofibrous membranes are backed by a microfibrous non-woven forming a hybrid membrane. The novel generation of nanocomposite/hybrid nanofibrous membranes can perform extraordinarily well in environmental remediation and control. This reality justifies authoring of this review paper.

Effect of Hydrogen Addition on Reduction Behavior of Ore Layer Mixed with Coke

Low RAR (reducing agent rate) operation of the blast furnace is one of effective techniques for reducing CO2 emissions. Coke mixed charging is a well-known and available measure to achieve low RAR operation by improving permeability and reducibility. Utilization of hydrogenous reducing agents is also an efficient measure. A reduction test under load was performed to investigate the effect of coke mixing with hydrogen addition on reduction behavior of the ore. Simultaneous use of coke mixing and hydrogen addition accelerated the reduction rate through the carbon gasification rate, and it was also decreased pressure drop. The effect of coke mixing and hydrogen addition on blast furnace operation was examined using a two-dimensional mathematical simulation model. In case of the ore layer mixed with coke, hydrogen addition in the reduction gas increased the hydrogen reduction ratio and decreased the direct reduction ratio. As a result, RAR decreased and permeability improved.

STUDY ON SOFTENING AND DROPPING PROPERTIES OF METALIZED BURDEN INSIDE BLAST FURNACE

The inferences of burden metallization rate on softening-melting dropping properties were investigated through softening-melting dropping test of three kinds of metalized burden pressure drop. The results indicated that the softeningmelting temperature interval of pre-reduction mixed burden is bigger than primeval mixed burden, the melting interval narrow with the rise of metallization rate of ferric burden as well as dropping temperature interval. The average pressure drop, maximum pressure drop and softening-melting dropping properties eigenvalue decrease with the rise of metallization rate of ferric burden. Besides, the dropping temperature of burden reduces with the rise of carbon content of molten iron. The combination high metalized burden and higher carbon content of molten iron is benefit to decreasing thickness of cohesive zone and improve permeability of cohesive zone

Impact of gravity on the bubble‐to‐pulse transition in packed beds

A model based on two‐phase volume‐averaged equations of motion is proposed to examine the gravity dependence of the bubble‐to‐pulse transition in gas‐liquid cocurrent down‐flow through packed beds. As input, the model uses experimental correlations for the frictional pressure drop under both normal gravity conditions and in the limit of vanishing gravity, as well as correlations for the liquid‐gas interfacial area per unit volume of bed in normal gravity. In accordance with experimental observations, the model shows that, for a given liquid flow, the transition to the pulse regime occurs at lower gas‐flow rates as the gravity level or the Bond number is decreased. Predicted transition boundaries agree reasonably well with observations under both reduced and normal gravity. The model also predicts a decrease in frictional pressure drop and an increase in total liquid holdup with decreasing gravity levels. © 2013 American Institute of Chemical Engineers AIChE J 60: 778–793, 2014

Cuttings Transport with Gas in the Highly-Deviated Horizontal Wells

Gas drilling has been widely used due to its advantages of protecting and finding oil and gas reservoir, reducing lost circulation and pipe sticking, extending the bit life, and improving rate of penetration (ROP). Cuttings transport in highly-deviated and horizontal segment is considered as an important part of the design of hydraulic parameters. In this case, poor cuttings transport will lead to stuck pipe, higher drag and torque, slower ROP, bad cementing quality, and other problems. In this study, a two-layer steady model was developed to depict cuttings transport behavior, and the sensitivity analyses were conducted. The simulations show the ratio of bed area and annular area and pressure drop decrease with the increase of pipe eccentricity or inclination, and increase with the increasing gas density or gas viscosity. But the inclination, gas density and viscosity have a minor effect on cuttings transport.

EFFECTS OF HYDROPHOBICITY-INDUCING ROUGHNESS ON MICRO-FLOWS

The effect of three-dimensional roughness on pressure-driven flow of water through a microchannel is examined using a finite volume numerical model. In the case of roughness created by the presence of microposts on the channel walls, the pressure drop is found to increase as a function of the height of the microposts. However, in the case where the space between the microposts is free of shear (for example, when air or vapor is trapped between the micro-roughness elements), the pressure drop decreases. This is a model of superhydrophobic surfaces, such as the lotus leaf surface. It is found that there is a critical configuration of the microchannel that can lead to drag reduction even when microposts are present.

Analytical Study to Estimate Re-entry Horizontal Well Productivity of Amara oil Field

Amara is situated south east of the city of Missan. The structure of Amara field is approximately about 9 Km long and 5 km width. This field is produced from three producing reservoirs Khasib, Mishrif and Nahr Umar. Most of the wells in this field that are producing from the main pay zone (Nahr Omar) suffer from sand production problem that was led to completely shut-in the wells due to accumulated sands in the wellbore. 
 The objective of this study is to investigate re-entry horizontal wells as a solution that may lead to minimize the well problems especially that is concern with sand problem, keeping into consideration the increasing wells productivity. 
 The production of horizontal wells can dramatically be improved by providing a greater contact of reservoir to the wellbore. Horizontal wells may also offer other advantages such as decreasing pressure drop, fluid velocities around the wellbore, minimizing water and gas coning as well as accelerated production. This may be extended to include the elimination of sand production problem from unconsolidated sand formations. Additionally, the design of horizontal wells must also includes the sand screens and/or gravel pack completion. 
 Due to limited geological and reservoir data of Amara oil field, advance analytical software was used to analyze the production history for two vertical wells AM/2 and AM/3. These wells are completely shut-in due to sand accumulation in the wellbore. The analytical solution converts the vertical well geometry into horizontal well model using same reservoir and fluid characteristics to estimate horizontal wells productivity increment for different pressure drawdowns and stimulation process. 
 The results showed that well AM/3 has greater response for production increment against the applied reservoir pressure drawdowns and stimulation activity than (well AM/2). This conclusion may led to select (well AM/3) to be much superior than (well AM/2) for eliminating sand control production.

Multi-objective optimization design of condenser in an organic Rankine cycle for low grade waste heat recovery using evolutionary algorithm

The optimum design of a condenser is significant in an organic Rankine cycle to achieve higher waste heat utilization efficiency. Based on the mathematical model of a condenser using plate heat exchanger (PHE), some key geometric parameters on the total heat transfer surface area and pressure drop of the condenser are examined. In order to obtain geometric parameters of a plate heat exchanger, a multi-objective optimization of the condenser in organic Rankine cycle is conducted to achieve the optimal geometry design. The total heat transfer surface area and pressure drop are selected as two objective functions to minimize both total heat transfer surface area and pressure drop under the constant heat transfer rate and LMTD conditions. The plate width, plate length and plant distance are selected as the decision variables. Non-dominated sorting generic algorithm-II (NSGA-II) which is an effective multi-objective optimization method is employed to solve this multi-objective optimization design of PHE. The results show that an increase in channel distance or plate width increases the total heat transfer surface area and decreases pressure drop in the condenser. It is noted that the plate length of PHE has a positive effect on the optimization design of PHE. By multi-objective optimization design of the PHE, a Pareto optimal point curve is obtained, which shows that a decrease in total heat transfer surface area of a condenser can increase the pressure drop through the condenser.

Experiment of complex flow in full size horizontal wells with perforated completion

Abstract A full size perforated casing of 139.7 mm in external diameter was adopted to simulate the horizontal wellbore. The influences of perforation parameters and injection rate on the pressure drop in horizontal wells were investigated by experiments. The results show that: (1) With the increase of perforation density, perforation diameter and perforation phase, both the frictional pressure drop and the total pressure drop increase and the mixture pressure drop decreases. (2) When the mainstream Reynolds number at the perforated casing exit remains constant, with the increase of injection rate, the total pressure drop and mixing pressure drop increase. When the injection rate is less than the critical injection rate (0.05%–0.10% under the study conditions), the mixing pressure drop is less than 0. When the injection rate is greater than the critical injection rate, the mixing pressure drop is greater than 0. The acceleration pressure drop can be neglected when the injection rate is less than 0.10%, otherwise the acceleration pressure drop rises significantly with the increase of injection rate. (3) With the increase of injection rate, the proportion of frictional pressure drop to total pressure drop decreases while that of acceleration pressure drop to total pressure drop increases. When the injection rate is less than 1.00%, the proportion of mixing pressure drop to total pressure drop tends to rise with the increase of injection rate. When the injection rate is greater than 1.00%, the proportion of mixing pressure drop to total pressure drop almost remains unchanged.