Low Pressure Loss Research Articles

Effective Ways to Avoid Barite Sag and Technologies to Predict Sag in HPHT and Deviated Wells With a Case Study in One Iranian Reservoir

Barite sag is an oilfield term used to describe significant density variations while circulating bottoms up after a trip, logging run, or other operations that require the mud to remain static for an extended period of time. Sag is caused by static or dynamic settling followed by slumping of the weighted material. Static sag, as the name suggests, is caused when circulation is stopped for an extended period of time and the weighting agents begin to settle under the influence of gravity. The authors present the most effective ways to avoid the occurrence of barite sag in high-pressure high-temperature drilling operations, and in high-angle wells beside a case study in Gachsaran formation in Ahwaz oil field of Iran. The ways involve replacing barite by other weighted materials such as ilmenite or manganese tetraoxide. The lower the Equivalent Circulating Density, the higher the rate of drilling operation as well as the lower pressure losses, especially in mud pumps. In this thesis, a new water-based mud formulation is introduced that uses polyanionic cellulose and xanthan gumas viscosifiers. By using a Brookfield viscometer (DV-II + Pro), viscosities of different muds at ultralow shear rates were measured. According to their rheological properties, a desirable mud formulation was developed.

The Best Common Ways to Manage Barite Sag in HPHT and Deviated Operations With a Case Study in the Iran Oil Industry

Barite sag is an oilfield term used to describe significant density variations while circulating bottoms up after a trip, logging run, or other operation that requires the mud to remain static for an extended period of time. Sag is caused by static or dynamic settling followed by slumping of the weighted material. Static sag, as the name suggests, is caused when circulating is stopped for an extended period of time, and the weighting agents begin to settle under the influence of gravity. Due to slumping, dynamic sag occurs frequently in inclined holes. However, the problem has been exacerbated by the increased frequently of high-angle wells with the associated increase in particle settling rate, which occurs in an inclined fluid column. The settling of solids is enhanced by convective currents created by density differences in the fluid across the annulus cross-section. This effect is frequently referred to as the Boycott effect. The authors present the most effective ways to avoid the occurrence of barite sag in high-pressure high-temperature drilling operations, and in high-angle wells beside a case study in Gachsaran formation in the Ahwaz oil field of Iran. The methods include replacing barite with other weighted materials such as ilmenite or manganese tetraoxide. The lower the Equivalent Circulating Density, the higher the rate of drilling operation as well as the lower pressure losses especially in mud pumps. The authors introduce a new water-based mud formulation that uses attapulgite and xanthan gum as viscosifiers. By using a Brookfield viscometer (DV-II + Pro), viscosities of different muds at ultralow shear rates were measured. According to their rheological properties, a desirable mud formulation was developed.

Non-Newtonian fluid flow in plane channels: Heat transfer enhancement using porous blocks

A numerical investigation is performed for heat transfer enhancement in a parallel-plate channel. Porous blocks are inserted to partially fill the channel, which is crossed by a power-law fluid. The modified Brinkman–Forchheimer extended Darcy model for power-law fluids is used in the porous layer while the Navier–Stokes equation are employed in the clear region of the channel. Results are reported for two cases: (1) a channel with a single porous block and (2) a channel with two porous blocks mounted alternatively at the bottom and top walls of the channel. The combined effects of both the porous blocks and the non-Newtonian fluid properties on the hydrodynamic and thermal characteristics of the flow are analyzed. To this end, computations are performed to highlight the effect of parameters such as the Darcy number, the Reynolds number, and the power-law index. For the case of the single porous block, the heat transfer is enhanced and maximized at low permeability. In the second configuration as well, heat transfer improvement can also be obtained, even if the thermal conductivity ratio is equal to 1. This enhancement is maximized for particular values of the Darcy number that depend on the flow pattern and the power-law index. Concerning the rheological aspect, it is found that pseudo plastic fluids exhibit the highest Nusselt number and the lowest pressure loss. The presence of the porous inserts causes a significant increase in pressure drop, which is found to be more important with dilatant fluids.

Impact of delta winglet vortex generators on the performance of a novel fin-tube surfaces with two rows of tubes in different diameters

To achieve heat transfer enhancement and lower pressure loss penalty, even pressure loss reduction, two novel fin-tube surface with two rows of tubes in different diameters are presented in this paper. Numerical simulation results show that the fin-tube surface with first row tube in smaller size and second row tube in larger size can lead to an increase of heat transfer and decrease of pressure drop in comparison with the traditional fin-tube surface with two rows of tubes in the same size. Based on this understanding, delta winglet pairs are punched out only from the larger fin area around the first transverse row of tubes in smaller size in the novel fin-tube surfaces. Delta winglet pairs used as longitudinal vortex generator are arranged either in “common flow up” or “common flow down” configurations. Numerical simulation results show that delta winglet pairs can bring about a further heat transfer enhancement and pressure drop decrease through the careful arrangement of the location, size and attack angle of delta winglet pairs either in “common flow up” or “common flow down” configurations. The traditional knowledge of heat transfer enhancement with necessary pressure drop increase is challenged by the present conclusion. The present work will be helpful to develop more compact, higher heat transfer efficiency, lower fan power and quieter heat exchanger of refrigeration and air condition system.

Combined evaluation of second order turbulence model and polydispersion model for two-phase boiling flow and application to fuel assembly analysis

High-thermal performance PWR (pressurized water reactor) spacer grids require both low pressure loss, high wall heat transfer coefficient and high critical heat flux (CHF) properties. A further detailed understanding of the main physical phenomena (wall boiling, entrainment of bubbles in the wakes, recondensation) is needed and can be reached by numerical simulation. In the field of fuel assembly analysis or design by means of CFD codes, the overwhelming majority of the studies are carried out using two-equation eddy viscosity models (EVM) as turbulence model, especially the standard K − ɛ model, while the use of Reynolds Stress Transport Models (RSTMs) remains exceptional. In contrast, extensive testing and application over the past three decades have revealed a number of shortcomings and deficiencies in eddy viscosity models. Indeed, the K − ɛ model is totally blind to flow rotation, e.g., in the presence of swirls. This aspect is crucial for the simulation of a hot channel in a fuel assembly. In fact, the mixing vanes of the spacer grids generate swirls in the coolant water, which enhances the heat transfer from the rods to the coolant in the hot channels and thus limits boiling. In this work, all the models are implemented in NEPTUNE_CFD, a three dimensional multi-fluid code developed especially for nuclear reactor applications, in the framework of the NEPTUNE project (EDF, CEA, AREVA-NP, IRSN). In a previous work, we have evaluated computational fluid dynamics results obtained with RSTM against single-phase liquid water tests equipped with a mixing vane and against two-phase boiling cases (DEBORA-tube and ASU-annular channel tests). In the present work, a geometry closer to actual fuel assemblies is considered. It consists of a rectangular test section in which a 2 × 2 rod bundle, equipped with a simple spacer grid with mixing vanes, is inserted. The influence of the turbulence model on target variables supposed to be related to CHF limitation is discussed. Numerical investigations on the optimised angle of mixing vanes are addressed. In addition, the impact of a detailed description of the bubble size distribution on the boiling flow with realistic geometry is addressed. The relative importance of the correct description of this modelling of polydisperse bubble size is due to the dependency of (i) main hydrodynamic forces, like drag, as well as of (ii) inter-phase transfer area with respect to the individual bubble size. The effects of the phenomena of coalescence or break-up and the main influences of mean bubble diameter on the void fraction and fluid velocity in the vicinity of the grids are underlined. The study of this 2 × 2 rod bundle case is a further step towards a physically reliable local CFD modelling of the two-phase boiling flow in real fuel assemblies, including spacers grid structures.

307 ディーゼル微粒子フィルタのセル構造の検討(水・排ガス処理(物理化学処理))

The environmental regulation tends to become strict rapidly, and the further highly performance of DPF is demanded. Generally, the square cell design of DPF is worldwide standard. In recent years, DPFs with some another cell design have been realized by the improvement of processing technology. These DPFs have been developed for higher Ash capacity and lower pressure loss. In this study, we compared two DPFs performances between hexagonal cell and traditional square cell. We measured particle number concentration by EEPS to obtain filtration efficiency on early filtration stage; and we also measured pressure drop during soot loading at engine test bench. Results show that, the soot leakage on early filtration stage reduced rapidly with hexagonal cell. Backpressure during soot loading with hexagonal cell is lower than that of traditional square cell.

Alternative Plugs Flow Liquid Chromatography (APFLC)/EI-MS System Using a T-shaped Flow Path

The vapor condensation method can be used for forming an alternative flow of liquid masses using a single solvent for alternative plugs flow liquid chromatography (APFLC), described in our previous paper. APFLC is more effective when adopting a T-shaped flow path and aqueous-organic solvents with a liquid-to-gas volume ratio (bulk fraction; β) ranging between 0.0006 and 0.004 in an open tubular GC capillary column at below 70°C. High-density plugs flow by a T-shaped flow path leads to extremely high resolution. Alternative plugs flow is formed when the liquid contact angle to the solid phase is above 75°. An aqueous mixture of the usual HPLC solvent can be readily used for APFLC. An EI-mass spectrum is obtained that is comparable with that in the NIST library, except for the DMF mixture medium. Due to low-pressure loss properties in the column, the system does not require a high-pressure liquid pump. Solid hydrocarbon resin with a contact angle to water of between 75° and 79°, such as polystyrene and olefinic polymers, is anticipated to be applicable to APFLC and hydro-membrane gas chromatography (HMGC) by a consideration of their surface tensions.

Numerical simulation on a throttle governing system with hydraulic butterfly valves in a marine environment

Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve. It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.

버터플라이 밸브의 유량측정 불확도에 대한 영향

For testing large-capacity pumps, the accurate flow rate measurement is needed in the test loop. As a measuring method of flow rate, venturi tube is recommended due to its low pressure loss. However, upstream disturbance of loop component such as a valve has an effect upon the accuracy of flow rate measurement. For controlling flow rate in case of high flow rate and large-scale piping system, a butterfly-type valve is generally used due to its compactness. However, a butterfly valve disturbs downstream flow by generating turbulence, cavities, or abrupt pressure change. In this study, the effect of downstream disturbance of butterfly valve on the flow rate measurement using a venturi tube is investigated. Test loop consists of circulation pump, reservoir, butterfly valve, venturi tube, and reference flow meter. The test is conducted with regard to a different valve opening angle of butterfly valve. According to the valve opening angle, the uncertainty of flow rate measurement is investigated.

CFD study on flow distribution uniformity in fuel distributors having multiple structural bifurcations of flow channels

This work studied the issues of uniform flow distribution for general application in fuel cells, fuel processing chemical reactors, and other industrial devices. A novel method for uniform flow distribution was proposed, in which multiple levels of flow channel bifurcations were considered to uniformly distribute a flow into 2 n flow channels at the final stage, after n levels of bifurcation. To study the effect of the flow channel bifurcation structure and dimensions on the flow distribution uniformity, numerical analysis was conducted. Parameters such as the flow channel length and width at each level of bifurcation as well as the curvature of the turning area of flow channels were particularly investigated. Important results concerning the geometrical design of flow distributors for better flow distribution and uniformity are presented. The best structure of a flow distributor was selected based on the criterion of flow distribution uniformity and low pressure loss. Since the studied novel flow distributor distributes a flow into a number of parallel channels in a remarkable uniformity, the flow distribution structure is expected to be widely used in fuel cells, fuel cell systems, and variety of industrial reactors and heat exchangers to significantly improve the performance of these devices. The studied flow regime is limited to laminar flow. A CFD tool FLUENT @ was used for the simulation. The numerical treatment of convection terms in governing equations was based on the QUICK scheme, and the coupled computation solving for pressure and velocity fields was based on the SIMPLE algorithm.

Ｄｅｓｉｇｎ‐ｂｙ‐Ａｎａｌｙｓｉｓと試験による低圧損気水分離器の開発（Ｉ）解析の妥当性確認および低圧損スワラーの設計

The purpose of this study is to develop a steam separator for BWR with low pressure loss by CFD and a scale model test. The swirler is the key component for the separation performance and pressure loss. Therefore, we have focused on the improvement of the swirler and tried to improve the swirler geometry to reduce the swirler pressure loss while maintaining the separation performance. This study consists of two stages. In the first stage, we measure pressure loss and water discharge ratio using the 1/2.22-scale test under BWR operating pressure, and then validate the CFD method by comparison with the scale test results. In the second stage, we improve the swirler geometry by the survey of some geometry factors using CFD. We predict that the inlet and outlet pressure losses of the swirler are dominant in the separator. By improving the geometry at the inlet and outlet of the swirler, we show from the results of CFD and a scale test that the improved swirler can reduce pressure loss by about 50% compared with the conventional swirler.

水素/二酸化炭素混合ガス用平板型触媒燃焼器の検討(熱工学,内燃機関,動力など)

A fuel cell system which uses hydrogen from fuel reforming, needs combustion heat of the residual gas from the fuel cell to support the endothermic reforming reaction and the evaporation of fuel. In the case of methanol reforming fuel cell, the residual gas contains hydrogen together with large concentration of carbon dioxide, which is more than 60 vol.%. New type combustor is needed for the combustion of the residual gas in wide mixture range, under low CO emission and low temperature for low damage of reforming catalysts. Thin plate type catalytic combustor using millimeter-scale protuberances is proposed and the combustion characteristics are examined comparing with conventional combustor. Proposed plate type catalytic combustor provided wide combustible range with residual gas of the reforming fuel cell, low CO emission lower than 50ppm low temperature combustion and low-pressure loss with combustor thickness smaller than 5.5mm The combustible range and combustion efficiency is effectively controlled by the height of protuberances and layout of fuel injection holes.

Study of Sweep and Induced Dihedral Effects in Subsonic Axial Flow Compressor Passages—Part II: Detailed Study of the Effects on Tip Leakage Phenomena

This article presents the detailed study of rotor tip leakage related phenomena in a low speed axial compressor rotor passages for three sweep configurations [Unswept (UNS), Tip Chordline Swept (TCS) and Axially Swept (AXS)]. Fifteen domains are numerically studied with 5 sweep configurations (0°, 20°TCS, 30°TCS, 20°AXS, and 30°AXS) and for 3 tip clearances (0.0%, 0.7% and 2.7% of the blade chord). Results were well validated with experimental data. Observations near the tip reveal that UNS rotor shows high sensitivity than the swept rotors in the blade pressure distribution with change in tip clearance. AXS rotor has high loading capability and less tip clearance effect on blade loading at the near stall mass flow. Downstream shift of the vortex rollup along the chord is observed with increased flow coefficient and increment in the tip gap height. In particular, the effect of flow coefficient is more predominant on this effect. Tip vortex-related flow blockage is less with the swept rotors. Among the rotors, the AXS rotor is found to incur low total pressure losses attributable to tip leakage. Effect of incidence is observed on the flow leakage direction.

Ｄｅｓｉｇｎ‐ｂｙ‐Ａｎａｌｙｓｉｓと試験による低圧損気水分離器の開発（ＩＩ）実規模試験による低圧損気水分離器性能の実証

The purpose of this study is to develop a new BWR steam separator with a lower pressure loss of more than 20% than the current steam separator while maintaining the steam separation performance. Reducing the pressure loss of steam separators is advantageous in that it reduces the required recirculation pump power and hence increases the net electrical power output. In previous studies, a low-pressure-loss steam separator was developed by three-dimensional two-phase flow simulations verified by 1/2.22-scale model experiment. In this study, performance tests for a full-scale steam separator with an improved swirler were conducted under actual reactor operating conditions of 7.17 MPa and 287°C. The obtained results demonstrate that pressure loss decreases by about 25% and the separation performance is similar to that of the current steam separator under rated reactor conditions.

A second order turbulence model based on a Reynolds stress approach for two-phase boiling flow and application to fuel assembly analysis

High-thermal performance PWR (pressurized water reactor) spacer grids require both low-pressure loss and high critical heat flux (CHF) properties. Numerical investigations on the effect of angles and position of mixing vanes and to understand in more details the main physical phenomena (wall boiling, entrainment of bubbles in the wakes, recondensation) are required. In the field of fuel assembly analysis or design by means of CFD codes, the overwhelming majority of the studies are carried out using two-equation Eddy Viscosity Models (EVM), especially the standard K– ɛ model, while the use of Reynolds Stress Transport Models (RSTM) remains exceptional. The simulation of swirling flow generated by the mixing vanes plays an important role for the prediction of the CHF for the fuel assemblies. For this reason, according to Mimouni et al. (2008b, 2009b), rotation effects and RSTM model are more specifically addressed in the paper. Before comparing performance of EVM and RSTM models on fuel assembly geometry, we performed calculations with simpler geometries, the DEBORA case and the ASU-annular channel case. ASU-annular channel case has already been addressed in Mimouni et al. (2008b, 2009b). Then, a geometry closer to actual fuel assemblies is considered. It consists of a rectangular test section in which a 2 × 2 rod bundle equipped with a simple spacer grid with mixing vanes is inserted. The influence of the turbulence model on target variables linked to CHF limitation will be discussed. Moreover, the sensitivity to the mesh refinement will be particularly examined. The study of this case is a further step towards the modelling of the two-phase boiling flow in real-life grids and rod bundles.

A second order turbulence model based on a Reynolds stress approach for two-phase boiling flow. Part 1: Application to the ASU-annular channel case

High-thermal performance PWR (pressurized water reactor) spacer grids require both low pressure loss and high critical heat flux (CHF) properties. Numerical investigations on the effect of angles and position of mixing vanes and to understand in more details the main physical phenomena (wall boiling, entrainment of bubbles in the wakes, recondensation) are required. In the field of fuel assembly analysis or design by means of CFD codes, the overwhelming majority of the studies are carried out using two-equation eddy viscosity models (EVM), especially the standard K– ɛ model, while the use of Reynolds Stress Transport Models (RSTM) remains exceptional. But extensive testing and application over the past three decades have revealed a number of shortcomings and deficiencies in eddy viscosity models. In fact, the K– ɛ model is totally blind to rotation effects and the swirling flows can be regarded as a special case of fluid rotation. This aspect is crucial for the simulation of a hot channel in a fuel assembly. In fact, the mixing vanes of the spacer grids generate a swirl in the coolant water, to enhance the heat transfer from the rods to the coolant in the hot channels and to limit boiling. First, we started to evaluate computational fluid dynamics results against the AGATE-mixing experiment: single-phase liquid water tests, with Laser-Doppler liquid velocity measurements upstream and downstream of mixing blades. The comparison of computed and experimental azimuthal (circular component in a horizontal plane) liquid velocity downstream of a mixing vane for the AGATE-mixing test shows that the rotating flow is qualitatively well reproduced by CFD calculations but azimuthal liquid velocity is underestimated with the K– ɛ model. Before comparing performance of EVM and RSTM models on fuel assembly geometry, we performed calculations with a simpler geometry, the ASU-annular channel case. A wall function model dedicated to boiling flows is also proposed.

Pressure Loss and Heat Transfer Through Heat Sinks Produced by Selective Laser Melting

Heat removal from electronic packages is often assisted with the use of heat sinks whose heat transfer surfaces come in a variety of forms such as cylindrical pins, flat fins, and corrugated sheet. These conventional designs are manufactured by traditional methods such as forging, machining, casting, stamping and bending, or a combination of processes. This article introduces a novel manufacturing technique, selective laser melting (SLM), and demonstrates its ability to fabricate new designs of heat sink that have not previously been considered, primarily due to their geometric complexity. Three novel finned structures have been manufactured and their thermal and fluid flow characteristics have been determined experimentally. The three heat sinks demonstrate selective laser melting's ability to produce fine detail and consist of a staggered elliptical array, an elliptical array where the pins are angled in a direction perpendicular to the flow, and a densely packed diamond array. The novel heat sink designs were compared to a cylindrical pin array manufactured using the SLM process as well as with pin fin data from the literature. The heat sinks produced by the SLM method have been shown to have superior performance to that of the conventional heat sinks. Although the angled elliptical fins transmit similar amounts of heat to the cylindrical pin fins across the range of air flow rates considered, they incur a lower pressure loss. The densely packed diamond array not only transfers 60% more heat than the cylindrical array, but does so with a lower pressure drop across it.

Performance analysis of a novel TiO 2-coated foam-nickel PCO air purifier in HVAC systems

A novel TiO 2-coated foam-nickel photocatalytic oxidation (PCO) air purifier was designed for applying to heating, ventilating and air-conditioning (HVAC) systems. The face velocity of foam nickels was reduced by increasing skillfully windward area so that the problems of quite low removal efficiency and high pressure loss at high flow velocities were solved. A method to evaluate energy consumption of PCO air purifiers was presented for helping the design and the application of PCO air purifiers. The performances of the purifier were analyzed, including resistance, removal efficiency, reaction rate, and energy consumption. The results showed that increasing windward area is an effective method to reduce resistance and improve purification performance. The resistance of the purifier was less than 21 Pa when the flow velocity was less than 2 m/s. An additional driving apparatus will not be needed when the purifier is applied to a HVAC system. The flow velocity with the maximum reaction rate was 0.66 m/s, and it can be adjusted by changing windward area. The energy consumption should be reduced further when the purifier is used in summer in Shanghai. Some improvement measures were given to decrease the energy consumption.

Investigation of Radial Swirler Effect on Flow Pattern inside a Gas Turbine Combustor

A study was conducted to investigate the flow pattern in a gas turbine combustor using numerical and experimental approaches. The main function of a combustor is to burn the air-fuel mixture then to admit the high energy burnt gases, with uniform and limited temperature, to drive the turbine blades. The gas temperature must not exceed a certain allowable temperature to prevent any damage of the blades. Flow pattern within the combustor has a great effect on the self sustaining flame, mixing of fuel and air, combustion intensity and combustor exit temperature uniformity. For this reason, a radial vaned swirler was used in this study to demonstrate its effect on the flow pattern within the combustor. The radial swirler vanes had an aerodynamically curved profile to allow the incoming axial flow to turn gradually and hence to inhibit the flow separation on the suction side of the vane. Therefore, smooth flow turning, higher tangential and radial-velocity components can be generated at the swirler exit with lower pressure loss. Three swirler vane angles 40°, 50° and 60° corresponding to swirl numbers of 0.35, 0.54 and 1.13 were used to evaluate their effect on the combustor aerodynamics. The results show that the swirl number has a direct proportion relationship with the size and shape of the central recirculation zone as well as the corner recirculation. It is concluded that with the use of 40°, 50° and 60° vane angles swirler, the vortex breakdown phenomena occurs at different intensities and sizes.

Thermodynamic analysis of the reverse Joule–Brayton cycle heat pump for domestic heating

The paper presents an analysis of the effects of irreversibility on the performance of a reverse Joule–Brayton cycle heat pump for domestic heating applications. Both the simple and recuperated (regenerative) cycle are considered at a variety of operating conditions corresponding to traditional (radiator) heating systems and low-temperature underfloor heating. For conditions representative of typical central heating in the UK, the simple cycle has a low work ratio and so very high compression and expansion efficiencies and low pressure losses are required to obtain a worthwhile COP. An approximate analysis suggests that these low loss levels would not necessarily be impossible to achieve, but further investigation is required, particularly regarding irreversible heat transfer to and from cylinder walls. In principle, recuperation improves the cycle work ratio, thereby making it less susceptible to losses, but in practice this advantage is compromised when realistic values of recuperator effectiveness are considered.