Fluid Flow Pressure Drop Research Articles

Thermal performance evaluation of a microchannel with different porous media insert configurations

PurposeThis paper aims to numerically investigate the thermal performance evaluation of a microchannel with different porous media insert configurations.Design/methodology/approachHeat transfer and pressure drop of fluid flow through a three-dimensional (3D) microchannel with different partially and filled porous media insert configurations are investigated numerically. The number of divisions and positions of porous material inside the microchannel for 12 different arrangements are considered. A control volume method is used for single-phase laminar flow with the Darcy–Forchheimer model used for the porous media. The geometry of the problem consists of a microchannel with a rectangular cross-section of 0.4 mm × 0.2 mm and length 20 mm, with a stainless steel porous material insert with a porosity coefficient of ε = 0.32 and a Darcy number of Da = 2.7 × 10−4.FindingsNumerical results show that when the transverse arrangement is used, as the number of partitions increases, the thermal performance is improved and the heat transfer increases up to 300% compared to that of the plain microchannel. Comparing the obtained results from the microchannels with transverse and longitudinal configurations, at low Reynolds numbers, the transverse arrangement of porous blocks and at high Reynold numbers, the longitudinal arrangement present the best thermal performance which is virtually four times higher compared to the obtained Nu numbers from the plain microchannel. The results show that as the volume of porous material is constant in the cases with various transverse porous blocks, the pressure drop is not changed in these cases. Also, the highest thermal performance ratio is when the porous material is placed along the walls in a longitudinal direction.Originality/valueTo the best knowledge of the authors, in the previous research, the effect of the arrangement and location of the porous medium in the transverse and longitudinal direction in the microchannel and their effect in different states on the behavior of flow and heat transfer has not been numerically investigated. In this study, the porous media configuration and its placement in a 3D microchannel were numerically studied. The effect of porous material layout and configurations in different longitudinal and transverse directions on the pressure drop, heat transfer and thermal performance in the 3D microchannel is investigated numerically.

Quantifying the partial penetration skin factor for evaluating the completion efficiency of vertical oil wells

An oil well's productivity is generally considered the standard measure of the well's performance. However, productivity depends on several factors, including fluid characteristics, formation damage, the reservoir's formation, and the kind of completion the well undergoes. How a partial completion can affect a well's performance will be investigated in detail in this study, as nearly every vertical well is only partially completed as a result of gas cap or water coning issues. Partially penetrated wells typically experience a larger pressure drop of fluid flow caused by restricted regions, thus increasing the skin factor. A major challenge for engineers when developing completion designs or optimizing skin factor variables is devising and testing suitable partial penetration skin and comparing completion options. Several researchers have studied and calculated a partial penetration skin factor, but some of their results tend to be inaccurate and cause excessive errors. The present work proposes experimental work and a numerical simulation model for accurate estimation of the pseudo-skin factor for partially penetrated wells. The work developed a simple correlation for predicting the partial penetration skin factor for perforated vertical wells. The work also compared the results from available models that are widely accepted by the industry as a basis for gauging the accuracy of the new correlation in estimating the skin factor. Compared to other approaches, the novel correlation performs well by providing estimates for the partial penetration skin factor that are relatively close to those obtained by the tested models. This work's main contribution is the presentation of a novel correlation that simplifies the estimation of the partial penetration skin factor in partially completed vertical wells.

Study of The Heat Loss Effect in Geothermal Steam Production Well

Well casing and cement temperature can change during geothermal production operation. The change of temperature occurs because of the heat transfer from the geothermal fluid to the formation. The heat transfer occurs because of the temperature difference in geothermal fluid and formation. The heat of fluid moves to the casing, cement, and formation through convection and conduction. This research aims to develop the heat transfer model in the steam production well, predict the steam heat loss and its effect on every 100 m well increment, and predict the well casing and cement temperature distribution and their effect on every well segment. The heat transfer model is an analytical calculation model developed to be the base of the calculation of heat loss and a temperature drop of well casing and cement. This model was developed for the calculation of heat loss in steam production well. The model was compared with a simulator to test the suitability. The fluid flow pressure drop and well lithology were considered in this model. The heat loss was very low during the steam production. The heat loss could be higher, along with the formation temperature drop. The material thermal conductivity and the well segment’s layer thickness could affect the steam heat transfer in the production well.

Combined effects of a microchannel with porous media and transverse vortex generators (TVG) on convective heat transfer performance

The three-dimensional heat transfer and pressure drop of fluid flow within a microchannel with transverse vortex generator and porous medium are numerically investigated. A total of 14 cases with various designs of vortex generator, semi-porous, and completely porous material were studied in detail. Further, the performance is compared between microchannel with different heights and the number of transverse vortex generators, as well as a semi-porous microchannel with a vortex generator. The finite volume method is used to solve the governing equations based on the three-dimensional volume averaging method for single-phase laminar flow. The Darcy-Forchheimer model is applied to solve the flow in a porous medium. The computational domain includes a stainless steel rectangular microchannel with a vortex generator and/or the insertion of porous media. The numerical results indicate that the convective heat transfer coefficient increases with increasing height and the number of transverse vortex generators. Compared to the empty microchannel, the heat transfer coefficient is 12 times higher with a completely filled porous media and 2.6 times higher with eight vortex generators with 12.5% of the channel height. While pursuing a high heat transfer coefficient, the pressure drop of the fluid flow often also increases. Therefore, a thermal performance ratio is defined to normalize the change of heat transfer coefficient and pressure drop. The final combined results show that the microchannel with vortex generator and with top-and-bottom inserted porous media has the highest thermal performance ratio at low and high Reynolds number, respectively. Lastly, detail cross-sectional and down-the-channel flow streamlines and temperature distributions are shown to identify the fundamental mechanism of heat transfer. The findings of this study provide a comprehensive insight into designing an effective microchannel with optimal convective heat transfer and reasonable pressure drop.

A proposal for a correlation to calculate pressure drop in reticulated porous media with the help of numerical investigation of pressure drop in ideal & randomized reticulated structures

This paper presents a numerical investigation to estimate pressure drop in fluid flow through reticulated ideal and randomized porous structures. The 3D open-cell foam geometries are constructed using an in-house code along with the use of visualization tool kit (VTK) libraries. In this study, the ideal and randomized Kelvin structures with different porosities and pore densities are generated. These structures have been used to perform direct pore level simulations (DPLS) with the aid of a commercial CFD software. The simulation results are used to acquire the pressure drop across the structures. The pressure drop variation with respect to pore density, porosity, specific surface area, and randomization are analyzed and a pressure drop correlation for reticulated structures with new values of viscous and inertial coefficients is proposed. The validity of the proposed correlation is compared against the experimental and numerical data of the real structures that are available in the literature.

Experimental investigation on the packed bed of rodlike particles

Rodlike particles have been usually found in industrial applications, such as the straw and needle catalyst in energy and chemical engineering. Compared to spherical particles, rodlike particles exhibit different behaviour in the packing structure due to their rotational movement. In this work, we have experimentally explored the packing structure and its friction factor for fluid flow. The porosity of packing structure generated by two packing methods is measured for four kinds of rodlike particles. The experimental results show that the porosity of bed of rodlike particles in the poured packing is not a monotonic function of the aspect ratio of particles. This is due to the competition between the “self-fitting” effect and excluded effect. The porosity of bed of rodlike particles is more sensitive to the packing method than that of spherical particles. To describe the pressure drop of fluid flow through the packing structure, the Ergun equation is further modified by introducing the modified Reynolds number and Galileo number. By combing the experimental data for packed bed generated by the fluidised packing method, and other experimental work in current literature, a new empirical equation is proposed to predict the friction factor of the packing structure of rodlike particles, in which the effects of the particle orientation and particle shape are both considered by the equivalent sphericity. These experimental results would be of interest from applied standpoints as well as revealing fundamental effects of the aspect ratio of rodlike particles on the packing structure.

Influence of particle morphology on pressure gradients of single-phase air flow in the mono-size non-spherical particle beds

Adequate equivalent diameters for non-spherical particles in predicting the pressure drop of fluid flow through particle beds were pursued. A series of experiments to measure the pressure drop of single-phase air flow through particle beds were performed using three kinds of spherical particles (2, 3.5 and 5 mm diameter) and four kinds of cylindrical particles. The experimental data were utilized for evaluating previous models and for proposing a new model, a modified Wu et al. (2008) model with an alternative Ergun constant for the viscous energy loss term.The proposed model agreed well with the pressure drop of single-phase flow through spherical particle beds within 10% in average. The experimental data for cylindrical particle beds also agreed well with the proposed model within 16% in average by applying the equivalent diameter proposed by Li and Ma (2011) as a characteristic size of non-spherical particles.

Novel methods of oil fouling inhibition on surface of plate heat exchanger in simulated oilfield geothermal water

Crude oil fouling on heat transfer surface (HTS) is a very troublesome problem for the utilization of oilfield geothermal water in which slight crude oil exists. The deposition of crude oil on HTS will decrease heat transfer efficiency, increase the pressure drop of fluid flow, and even block flow channel. In this study, surface hydrophilization via anodization, flow velocity enhancement and chemical addition three measures were adopted to solve the problem of crude oil soiling via weakening the adhesion force between crude oil and HTS as well as intensifying the interaction between water and crude oil. Contact angle measurement and microscopic morphology study were conducted on the highly-hydrophilic surface fabricated via anodization. Oil-soiling experiments accompanied with three mentioned techniques were carried out in plate heat exchanger (PHE) apparatus, and obvious oil-fouling inhibition effects were presented. The effect was reflected by the decrease of fouling thermal resistance. For 110°C simulated oilfield geothermal water, which contained approximate 1vol.% crude oil soiling, with 0.24m/s flow velocity, the fouling induction period extended to 500min from 0min when surface hydrophilization was applied through anodization. In anodized PHE with titanium plates, the value of fouling thermal resistance decreased by about 77.8% when the flow velocity of 110°C hot fluid without chemical additive increased from 0.24m/s to 0.72m/s, and the value could be reduced by around 62.5% after the addition of 0.29g/L chemical additive LIUXU-10 mainly composed of sodium dodecyl sulfonate (SDS), when the flow velocity of 110°C hot fluid was 0.12m/s. Compared with PHE with titanium plates (Ti-PHE) at 0.24m/s hot fluid flow velocity, the fouling thermal resistance decreased by approximate 93.3% when the Ti-PHE was anodized to be highly hydrophilic, the hot fluid flow velocity increased to 0.6m/s and 0.87g/L chemical additive was added.

Numerical study on the pressure drop of fluid flow in rough microchannels via the lattice Boltzmann method

Purpose – The purpose of this paper is to provide a quantitative assessment on the effect of wall roughness on the pressure drop of fluid flow in microchannels. Design/methodology/approach – The wall roughness is generated by the method of random midpoint displacement (RMD) and the lattice Boltzmann BGK model is applied. The influences of Reynolds number, relative roughness and the Hurst exponent of roughness profile on the Poiseuille number are investigated. Findings – Unlike the smooth channel flow, Reynolds number, relative roughness and the Hurst exponent of roughness profiles play critical roles on the Poiseuille number Po in rough microchannels. Modeling results indicate that, in rough microchannels, the rough surface configuration intensifies the flow-surface interactions and the wall conditions turn to dominate the flow characteristics. The perturbance of the local flows near the channel wall and the formation of recirculation regions are two main features of the flow-surface interactions. Research limitations/implications – The fluid flow in parallel planes with surface roughness is considered in the current study. In other words, only two-dimensional fluid flow is investigated. Practical implications – The LBM is a very useful tool to investigate the microscale flows. Originality/value – A new method (RMD) is applied to generate the wall roughness in parallel plane and LBM is conducted to investigate the pressure drop characteristics in rough microchannels.

New models to predict the viscosity of extra-heavy oil in Colombian fields

Viscosity is one of the fundamental properties of fluids in calculating the pressure drop of fluid flow through pipes or porous media. It is also highly relevant in interpreting production tests, hydrocarbon transport and the analysis of problems that may arise in the well. This paper introduces an adjustment to the De Ghetto viscosity model in order to accurately predict the viscosity of undersaturated extra-heavy oil. The adjustment of the De Ghetto model for undersaturated extra-heavy oil has been developed using a database of PVT analysis of extra-heavy oil to assess the accuracy of the models published in literature. Subsequently, by using statistical analysis and regression techniques, the models with the best approximation to the values of the PVT reports were adjusted, thus resulting in two models with absolute average error rates of 4.69 and 2.42%. These rates are valid for oils with API gravities ranging from 6.5 to 9.5, in order to accurately predict the viscosity of undersaturated extra-heavy oils.

Design of solar collector networks for industrial applications

The design and selection of banks of solar energy collectors for thermal applications requires that a thermal and a hydraulic objective be met. On the thermal side, the working fluid must provide the heat load to the process at the specified temperature and on the hydraulic side the fluid must flow through the system experiencing a pressure drop that is within the specified limits. In the case of solar collectors, the working fluid used to transfer heat to the process either in an open circuit or in a closed circuit is water. A solar collector can be viewed as a particular type of heat exchanger and the set of solar collectors needed for a particular application, as a network of heat exchangers. In this work, the overall arrangement of solar collectors which form the total collector surface area is referred to as the network of solar collectors (NSC). An NSC is used in large scale heating applications in buildings or in production processes. Such a network of collectors can exhibit arrangements that go from series, parallel or any combination of these. Contrary to domestic applications where water flows through the exchanger in natural convection, in large scale applications the flow of water is forced through the use of a pumping system. This paper introduces the tools for the design and selection of the most appropriate network arrangement for a given application as a function of the specified pressure drop for fluid flow, the required temperature and heat duty. A thermo-hydraulic model for solar collector networks is presented and its solution is graphically displayed with the length of the exchanger plotted against the number of arrays in parallel. The thermal and the hydraulic models are solved separately so that two solution spaces are represented in the same plot. The thermal space represents the thermal length required to meet the specified heat load as a function of the number of parallel arrays. The hydraulic space, on the other hand, represents the hydraulic length that meets the specified pressure drop as a function of the number of parallel arrays. The point where the two spaces meet determines the network structure that fulfils the required heat duty with an acceptable pressure drop.

Development of heat sink device by using topology optimization

Small scale fluid flow systems have been studied for various applications, such as chemical reagent dosages and cooling devices of compact electronic components. This work proposes to present the complete cycle development of an optimized heat sink designed by using Topology Optimization Method (TOM) for best performance, including minimization of pressure drop in fluid flow and maximization of heat dissipation effects, aiming small scale applications. The TOM is applied to a domain, to obtain an optimized channel topology, according to a given multi-objective function that combines pressure drop minimization and heat transfer maximization. Stokes flow hypothesis is adopted. Moreover, both conduction and forced convection effects are included in the steady-state heat transfer model. The topology optimization procedure combines the Finite Element Method (to carry out the physical analysis) with Sequential Linear Programming (as the optimization algorithm). Two-dimensional topology optimization results of channel layouts obtained for a heat sink design are presented as example to illustrate the design methodology. 3D computational simulations and prototype manufacturing have been carried out to validate the proposed design methodology.

Effect of particle diameter of porous media on flow and heat transfer in a mixing tee

Numerical simulations have been carried out to investigate flow and heat transfer in a mixing tee filled with periodic sintered copper spheres. Three particle diameter cases of 28mm, 14mm and 7mm with the array of 4×4, 8×8 and 16×16 at the same porosity of 0.3 have been calculated using large-eddy simulations and the Smagorinsky–Lilly sub-grid scale model. With the particle diameter decreasing, the mixture scale of hot and cold fluid tends to decrease in the mixing tee; the pressure drop of fluid flow through porous media increases. When the particle diameter ratios are 4:2:1 and the specific surface ratios are 1:2:4, the pressure drop ratios are 1:2:4; the thermal mixing in porous media is weakened because the temperature fluctuation decreases and the stratification of hot and cold fluids is observed.

A Semi-empirical Correlation for Pressure Drop in Packed Beds of Spherical Particles

The effect of a confining wall on the pressure drop of fluid flow through packed beds of spherical particles with small bed-to-particle diameter ratios was investigated to develop an improved pressure drop correlation. The dependency of pressure loss on both wall friction and increased porosity near the wall was accounted for by using a theoretical approach. A semi-empirical model was created based upon the capillary-orifice model, which included a wall correction factor for the inertial pressure loss. In this model, packed beds were treated as a bundle of capillary tubes whose orifice diameter in the core region was different from that of the wall region. Using this model, a new pressure drop correlation was obtained, based on the Ergun equation and applicable for a wide range of Reynolds numbers (10−2–103). The proposed correlation was compared with previous correlations, as well as with experimental data. This correlation showed close agreement with the experimental data for both low- and high-Reynolds number regimes and for a wide range of bed-to-particle diameter ratios. The ratio of the pressure drop in finite packing to that in homogeneous packing was then calculated. This ratio clearly shows how the wall effect depends on the Reynolds number and the bed-to-particle diameter ratio.

Laminar flow in channels with porous walls, revisited

An analytical solution for the pressure drop in fluid flow in a rectangular slit and cylindrical tube with porous walls is presented for the case of constant wall permeability. It is shown that model predictions for the particular case of constant wall velocity for rectangular slit with permeable walls agrees very well with Berman’s solution [J. Appl. Phys. 24 (1953) 1232]. The derivation presented in this work leads to analytical expressions for pressure drop as a function of wall permeability, channel dimension, axial position and fluid properties. These analytical expressions for constant wall permeability could be used to benchmark numerical routines for fluid flow modeling past semi-permeable membranes and for quick engineering estimates for pressure drop in cross-flow membrane modules.

Fluid flow pressure drop through an annular bed of spheres with wall effects

A model has been developed to predict the pressure drop for flow through an annular packed bed of spheres at random distribution. Ergun's equation, with a corrected flow velocity, is used. To consider the wall effect in the flow distribution, the annular section was divided into three regions: the external and internal wall regions, and an intermediate one, called transition. To find an average flow velocity, to be used in Ergun's equation, a different treatment has been applied to the wall regions, with respect to the transition region. That was necessary due to the presence of a further wetted area and the distortion on the porosity distribution. Model prediction showed good agreement with experimental data. Experiments were carried out for fully developed turbulent flow of air, at steady state condition, through an annular bed with a radius ratio of 1.369 and a bed to particle diameter ratio of 8.258.

Effects on internal structure on throughput of mixer-settler extraction column.

Maximum throughputs were measured for a mixer-settler extraction column of 100 mm diameter, and the effects of agitation speed and the internal structure on throughput were examined. To elucidate these effects on the throughput, the pressure differences at various points in the column were also measured. The throughput increased linearly with the agitation speed and the value for the 100 mm column was 2.3 times as large as that for the 60 mm column. Large effects of the downspout diameter and the distance between the impeller and the riser on the throughput were observed. It was confirmed that the throughput could be determined from the balance among the pressure drop of fluid flow, the suction pressure induced by the lifter-turbine impeller, and the buoyant force. The pressure drop of fluid flow was given by the sum of the pressure drops through the downspout and across the drop coalescer, and the former was dominant. The suction pressure induced by the impeller was correlated with the tip velocity of the impeller. It was predicted by the calculation method derived here that a large throughput could be realized by use of large downspout pipes, and the throughput increased with the column diameter for the column of similar figures, but the increase was comparatively small for the agitation speed corresponding to a given average drop diameter. The throughput was also expected to increase with the increase in the interfacial tension, while the effect of the density difference between the dispersed and the continuous phases on the throughput might be comparatively small.