Trend Of Pressure Drop Research Articles

Identifying the influence of inlet velocity changes to pressure drop and collecting efficiency in Stairmand and Lapple type cyclone separators

The object of this research is to compare the performance of Stairmand and Lapple type cyclone separators. The main problem to be solved in this research is determining which Stairmand or Lapple type cyclone separator is more suitable for integration into the pyrolysis system. The comparison is based on key performance indicators: pressure drop and collecting efficiency. The research findings indicate that both Stairmand and Lapple cyclone separators exhibit similar trends in pressure drop and collecting efficiency. As inlet velocity increases, the pressure drop also increases for both types. However, the collecting efficiency initially rises but then declines when inlet velocities exceed 13 m/s. The Lapple variant achieved a peak collecting efficiency of 98.94 % and pressure drop 16.26 mbar at an inlet velocity of 13 m/s, whereas the Stairmand design reached 97.33 % and pressure drop 12.16 mbar at 13 m/s inlet velocity. The Lapple type cyclone separator outperformed the Stairmand type in terms of both of pressure drop and collecting efficiency. This superiority is attributed to the specific design features and characteristics of the Lapple type. The superior performance of the Lapple type cyclone separator can be explained by its unique design elements that contribute to improved particulate matter separation and pressure drop. These elements may include differences in cylinder height and particulate matter outlet diameter. Based on the findings of this research, the Lapple type cyclone separator is recommended for integration into pyrolysis systems. However, it is important to consider the specific operating conditions of the pyrolysis process, such as temperature, the particulate matter size distribution, flow rate, and desired separation efficiency

Research on the Flow Characteristics in the Gap of a Variable-Speed Pump-Turbine in Pump Mode

A variable-speed pump-turbine is the core component of a hydraulic storage and energy generation station. When the pump-turbine operates at a constant speed, its response to the power grid frequency is poor. In order to improve the hydraulic efficiency of the pumped storage unit, variable-speed units are used. However, there has been no numerical study on the effect of the rotational flow characteristics within the gap of a variable-speed pump-turbine. This paper calculates the flow characteristics within the gap of a variable-speed pump-turbine under three typical pump modes (maximum head minimum flow condition, minimum head maximum flow condition, and maximum speed condition). The research results indicate that the rotational speed significantly affects the pressure distribution, velocity distribution, and turbulent kinetic energy distribution within the crown and band gaps. The higher the speed, the larger the area of the high-pressure region before the runner inlet compared to other operating conditions, and similarly, the low-pressure area after the runner outlet is also larger than in other operating conditions. The change in speed mainly affects the internal flow field of the crown gap, with the most noticeable changes occurring in the pressure and flow velocity at the inlet and outlet of the crown gap. There is a clear trend of pressure drop and velocity increase within the gap as the speed increases. However, with the increase in speed, the pressure distribution and flow velocity within the band gap remain almost the same. In addition to speed changes, it is observed that the pressure within the gap and the flow velocity within the passages are also related to the head, especially in the condition of maximum head, where this relationship becomes more noticeable.

On the Accuracy of Turbulence Model Simulations of the Exhaust Manifold

This study investigating the accuracy of turbulence model simulations of the exhaust manifold using computational fluid dynamics (CFD) carries significant implications. By modeling and analyzing the flow of emissions, we aim to identify areas of high stress and pressure, minimize the pressure drop, and maximize the flow of exhaust gases. This not only enhances engine performance, reduces emissions, and improves the durability of the manifold but also provides a unique opportunity to predict and analyze the flow and performance of the exhaust manifold, both quantitatively and qualitatively. This paper aims to provide a detailed comparison of five turbulence models that are commonly used in CFD to offer valuable insights into their accuracy and reliability in predicting the flow characteristics of exhaust gases. The results show that the k-kl-ω model showed the highest maximum velocity and the most comprehensive temperature range, efficiently capturing the transitional flow effects. The K-ω STD and SST transition models displayed significantly higher turbulent kinetic energy (TKE) values, indicating their enhanced effectiveness in modeling complex turbulent and transitional flows. Conversely, the Reynolds stress and RNG k-epsilon models displayed lower TKE values, suggesting more subdued turbulence predictions. Despite this, all models exhibited similar pressure drop trends, with a noticeable increase near the midpoint of the manifold. These quantitative findings provide valuable insights into the suitability of different turbulence models for optimizing exhaust manifold design.

High heat flux dissipation of membrane-venting heat sink with thin film boiling

Microchannel flow boiling exhibits outstanding heat transfer capabilities, rendering it a promising technology for cooling high heat flux devices. Nonetheless, rapid vapor generation in the channels increases pressure drop and leads to local dryness, restricting the performance of microchannel heat sinks. In this study, we designed a membrane-venting heat sink that has a hydrophobic porous membrane above a thin liquid film for venting vapor. The phase change of this heat sink comprises not only thin film flow boiling in the horizontal direction but also thin film boiling and thin film evaporation in the vertical direction, thereby mitigating the detrimental effects of flow boiling. Experiments indicate that utilizing a membrane with 1.0 µm pore size for venting can enable the effective heat flux of the heat sink to achieve 287.8 W/cm², with a transmembrane heat flux of 152.7 W/cm². Furthermore, the surging trend of pressure drop with heat flux was significantly slowed down, and the maximum effective heat flux increased by 553 % compared to the configuration without vent. This study demonstrates that adding and enhancing the vertical heat and mass transfer channels via hydrophobic porous membranes is a potent method for considerably improving flow boiling.

Behavior analysis of PEMFC with geometric configuration variation during multiple-step loading reduction process

Load shedding could be a solution to water accumulation alleviation during the operation of proton exchange membrane fuel cell (PEMFC) engines. In this paper, multiple-step loading reduction strategies based on two laboratory-scale (25 cm2) single PEMFCs (assembled with triple-serpentine and single-serpentine flow field plates on the both electrodes and thus named after cell TS and cell SS respectively) are experimentally discussed and evaluated. The real-time pressure evolution and HFR are recorded, compared and analyzed to characterize water transfer phenomenon among the components. The investigation results suggest that: 1. From the perspective of output voltage and power after load reduction, the number of reduction step has little effect on the output performance; 2. Cell TS exhibits better homogeneous trend of pressure drop although with less water removal quantity comparing with that of cell SS, which is resulted from multi-channel configuration; 3. The cathode pressure drop of cell SS decreases obviously throughout the experiment, indicating the convinced water removal capability of single-serpentine configuration; 4. Constant increase of HFR reflects membrane dehydration when the loading reduces. This paper demonstrates the possibility of removing accumulated liquid water by reducing the load of PEMFCs.

Experimental study on the effect of loading and regeneration for an optimized management of the DPF

Limits imposed by worldwide emission regulations on particulate emission from diesel engine exhaust resulted in the employment of filters to cut down pollutants to acceptable values after they are produced into the cylinders. The management of the entire system engine + aftertreatment demonstrated to play a fundamental role in order to ensure compliance with the increasingly stringent emission limits.This paper is devoted to investigate in detail the role of the engine operative conditions on the filter behavior during the loading phase and to analyze how the regeneration strategy affects the filter efficiency and its pressure drop during the subsequent loading phase. These aspects retain a relevant role in the light of the new limits for particle emission from the tailpipe related not only to the number of particles but also to the cut point for PN measurement, which will be lowered from the current 23 nm–10 nm (PN10).Testing was performed on a Euro6 engine; the results highlight that the specific engine operation deeply affects the filter loading process, with differences in the pressure drop trend (both in the shape and in the values) and in the DPF efficiency. The filter efficiency, once the regeneration event is completed, depends on the regeneration strategy: when the clean filter condition is restored, a slow increase of filtration efficiency is observed; when the regeneration event does not restore the clean filter status, the subsequent loading process is characterized by better filtration properties. The obtained findings represent additional useful information to account for in the procedure devoted to define the optimal strategy to manage the engine: the regeneration events should be planned not only by considering the pressure drop across the filter but accounting also for the filtration performance once the regeneration is completed, thus to define the optimal strategy to manage the engine + aftertreatment able to comply with the new stringent limits on tailpipe particles and to reduce fuel consumption and oil dilution.

Effect of contraction on the convective boiling heat transfer of microchannel heat sinks

The present study examines the effect of contraction before straight fin microchannels in the cold plate by using refrigerant R-134a as a working fluid. The experiments compared two test sections with the same geometry and dimension, but one has contraction before the microchannels (CBM), and another one has no contraction before the microchannels (NCBM); the mass flux ranges from 25 to 425 kg/m2⋅s while the heat flux spans from 60 to 300 kW/m2. The inlet flow conditions can be either a fully liquid inlet or with vapor qualities (from 0.1 to 0.45). Improved flow distribution is found with the introduction of the contraction. Based on the mass flux and irrespective of the inlet conditions, the test results indicated that the performance of the CBM shows a superior heat transfer coefficient (HTC) by about 3 ∼ 30 % than that of NCBM. Nonetheless, the pressure drop of CBM is lower than NCBM when the inlet is fully liquid. Conversely, the trend of pressure drop is reversed with a vapor-quality inlet. For the fully liquid inlet, the CBM contains a much lower pressure drop by 22 % compared to NCBM at a low mass flux of 36.2 kg/m2⋅s. However, the reduced pressure drop has narrowed to 3 % at a mass flux of 402.8 kg/m2⋅s. Flow visualizations were performed, and it was found that the CBM is free from flow reversal, and the fluctuations in temperature or pressure drop are much less pronounced. By contrast, the NCBM design shows flow reversal and sluggish bubble phenomena.

Impact of Fine Solids on Hydrotreating of Bitumen-Derived Gas Oil

Bitumen-derived gas oils that enter hydrotreaters contain fine solids such as minerals, heavy metals, and coke. The deposition of these fines will eventually restrict the flow and result in pressure buildup across the hydrotreater, which eventually necessitate the premature shutting down of the reactor system. To determine if certain types of fine particles had a greater detriment to the hydrotreating process, a series of experiments were performed by accelerated fine deposition in a trickle bed catalytic reactor under industrial conditions using bitumen-derived light gas oil. Kaolinite, montmorillonite, pyrite, and petroleum coke fines had no significant impact on the catalyst activity and catalyst deactivation toward hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodearomatization. Unlike the above fines, iron(III)oxide was found to convert into FeS under hydrotreating conditions, which provided a promoting effect for HDN and HDS reactions. When comparing the trends in pressure drop across the catalyst bed, there was a delayed period during the initial fine deposition where no change in pressure drop was observed, followed by an exponential increase in pressure due to the decrease in bed porosity. The difference found between these fines was the length of this delayed period, with iron(III)oxide and petroleum coke having the longest periods of no pressure growth. From inductively coupled plasma, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis of the fresh and spent catalysts, it was determined that the deposition of all fines occurred within the packing material in the preheating zone, with only petroleum coke and iron(III)oxide fines being found on the surface of the catalysts.

Аналіз розвитку технологій задувки доменних печей в 20-21 століттях

The article discusses the trends and classification of blast furnace blowers over the past 100 years. The development of blower technology is divided into 3 periods: The 1st period lasted until the end of the 30s of the XX century, characterized by a lack of scientific knowledge, mysticism and based on previous experience; the 2nd period - until the early 70s, when the "traditional" blower technology was mastered with one problem - difficulties with opening the first releases and simultaneous overheating of the top; the 3rd period continues today, it includes the development of new methods for intensifying heat transfer during blowing and scientific generalization of blower techniques. The main tasks of blowdown are to bring the blast furnace back to normal operation in a short time, in compliance with safety rules, without significant costs, and to preserve the blast furnace and auxiliary equipment for long-term productive operation. These tasks are closely linked to the design features of blast furnaces, including the cooling system, lining type and furnace size, which have steadily increased from less than 500 m3 to 5,600 m3. The complexity of understanding the processes of heating the charge column during the blowing period with the formation of a gas flow and a cohesion zone in it is the reason for numerous discussions about rational blowing methods: methods for calculating and placing layers of the blast furnace charge, the use of various hot blast additives (nitrogen, natural, blast furnace or coke oven gas, oxygen, steam, etc.), the rate of increase in hot blast flow and its temperature, the trend of pressure drop along the height of the charge column. The use of wood in the blast charge, the installation of constrictor rings in air tuyeres or the closure of a part of the tuyeres for blowing are discussed. Recommendations for blast furnace blowers are given. A comparison of "traditional" blowing with "progressive" blowing and blowing with nitrogen developed at the Iron and Steel Institute National Academy of Sciences of Ukraine are presented.

Experimental Investigation of Low-Concentrated Nanocomposite Polymer Gels for Water Shutoff Treatment Under Reservoir Conditions

Summary Excessive water production is one of the main challenges in mature oil fields. Applying polymer gels has proven to be an effective chemical treatment to this problem. Because of some limitations in application of polymer gels in oil reservoirs with harsh conditions, using nanoparticles (NPs) in gel structure has been proposed recently to improve the performance of such systems. However, while main body of the previous studies has only focused on improvement of bulk properties of polymer gels in presence of NPs, there is a serious lack of data on their performance in porous media. In this study, we have conducted a comprehensive investigation on application of two new nanocomposite polymer gels through bulk-gel static tests and dynamic core displacement tests. Fe2O3 and NiO NPs at low concentrations (<100 mg·L−1) in AN125VLM/chromium acetate polymer gel system were used. The results of bulk bottle tests at 82℃ demonstrated that the nanocomposite gel systems have the same gelation time and gel strength as the NPs-free gel. Swelling ratio measurements were also performed in a high-salinity formation water (268 949 mg·L−1), and accordingly, while NiO NPs deteriorated the swelling behavior of the gel system, Fe2O3 NPs showed a positive impact. The results of the strain-sweep test demonstrated relatively similar linear viscoelastic region and thus the same gel strength for all gel samples. In addition, the results of the thermogravimetric analysis (TGA) revealed that Fe2O3 NPs had a minor positive impact on thermal resistance of the polymer gel system. Finally, high pressure-high temperature coreflooding experiments were carried out on three sandstone reservoir core samples. Although the NPs-free gel showed a desirable level of disproportionate permeability reduction, the injection of Fe2O3 nanocomposite gel showed unsatisfactory results and caused rock permeability degradation. The pressure drop trend and deposition of polymer gel particles at the upstream injection side confirmed the aggregation and plugging effect of NPs during injection. Our findings demonstrate the critical aspect of dynamic core displacement testing of nanocomposite gels before their use for field applications.

Applications of Artificial Intelligence for Analysis of Two-Phase Flow in PEM Fuel Cell Flow Fields

Many electrochemical devices rely upon flow-field channels to transport reactants and byproducts to and from critical electrode sites. Often, this results in multiphase flow, which, if not managed properly, can reduce system performance and lifespan. In the case of PEM fuel cells, two-phase flow occurs when liquid water forms as a byproduct of the cathode oxygen reduction reaction. Over the past two-decades much effort has been invested to understand the nature of this stochastic transport phenomena and how to optimize flow-field design to mitigate its effects. This work probes the use of artificial intelligence to guide our understanding of complex relationships between liquid phase behavior and pressure drop in these reactant channels [1]. Using a supervised decision tree (DT) machine learning algorithm, the liquid distributions in ex-situ experimental reactant channels are correlated to the induced pressure drop for a range of air flow rates; this process is diagrammed in Fig. 1. Liquid phase data collection is accomplished by capturing 2D images via a CCD camera of liquid water distributions in a transparent flow channel simulating PEM fuel cell conditions. In this setup, liquid water is injected through the bottom of the GDL in the same manner that water must travel from the catalyst layer through the GDL to reach the channel an operating cell. Pressure transducers measure pressure drop along the length of the channel and are synchronized with the image collection. The images are processed for noise reduction and feature extraction and then used with pressure data to train a regression DT. The models produced using the DT show the potential to improve predictions over earlier methods that relied solely upon liquid area [2]. Overall, the DT models predicted pressure drop using liquid distributions with 88.9% to 98.54% accuracy and were able to capture complex behavior such as pressure changes due to the breakup of liquid slugs. In general, the methods may be valuable for attaining deeper understanding of the impact variables such as geometry, hydrophobicity, and system operating conditions have on two-phase flow pressure drop trends. Additionally, these models may serve as a validation tool for numerical efforts aimed at flow-field design. A reliable model that can accurately predict the liquid-gas two-phase flow pressure drop may be used to estimate the amount and potentially the distribution of the water content within the flow channel by inputting the pressure drop measured during the operation of the cell.Figure 1: Overview of the regression DT training and testing processes.[1] Santamaria AD, Mortazavi M, Chauhan V, Benner J. Two-Phase Flow Characterization in PEM Fuel Cells Using Machine Learning. In Meeting s 2019 May 1 (No. 30, pp. 1538-1538). The Electrochemical Society.[2] Hussaini IS, Wang CY. Visualization and quantification of cathode channel flooding in PEM fuel cells. Journal of Power Sources. 2009 Feb 15;187(2):444-51. Figure 1

Flow boiling and convective condensation of hydrocarbons: A state-of-the-art literature review

This study consists of a broad and critical literature review concerning in-tube convective boiling and condensation of hydrocarbons and their mixtures. A summary of observed experimental behaviors observed in literature for heat transfer coefficient, pressure drop, flow pattern and void fraction is presented. In general, it was found that hydrocarbons and HFCs presents similar heat transfer and pressure drop trends. An assessment of the accuracy of prediction methods for the heat transfer coefficient and pressure drop is also performed by comparing them with data gathered from literature. Reasonable agreement between the data and prediction methods was obtained only for convective condensation heat transfer coefficient of pure hydrocarbons inside microchannels and hydrocarbons mixtures inside conventional-sized and microchannels with the Silver-Bell and Ghally correction. No experimental study was found concerning flow boiling heat transfer coefficient and/or pressure drop of hydrocarbons mixtures inside microchannels. It is worth to highlight that a restricted number of data sources (independent laboratories) was found, highlighting the importance of further studies.

New insights on boiling carbon dioxide flow in mini- and micro-channels for optimal silicon detector cooling

Whilst the thermal management needs of future silicon detectors are increasing, the required mass and volume minimization of all detector ancillaries gets more demanding. This requires highly effective active cooling in very small channels. In the context of the AIDA-2020 project, a new test stand has been developed to characterize, with unprecedented level of accuracy, boiling flows of CO2 in mini- and micro-channels with hydraulic diameter ranging from 2 down to 0.1 mm. The heat transfer coefficient and pressure drop behaviour in stainless steel tubular evaporators for saturation temperatures from ＋20 to −25 °C, mass fluxes from 1200 to 100 kg m−2 s−1 and heat fluxes from 0.5 to 3.5 W/cm2 are discussed for one diameter. In addition, high speed camera observations of CO2 flow patterns recorded on micro-structured silicon cold plates are used to help with the interpretation of the heat transfer coefficient and pressure drop trends reported.

Fluidization characteristics of fine cohesive particles assisted by vertical vibration in a fluidized bed reactor

This research has examined fluidization and product characteristics through hydrogen reduction for nickel oxide (NiO) of contained in the Geldart group C assisted by vertical vibration in a fluidized bed reactor. It has confirmed that as vibration frequency and reaction temperature increase, the pressure drop trend becomes stable and minimum fluidization velocity reduces. As the gas–solid reaction increased with the increase in reaction temperature, oxygen contained in NiO was removed with a fast reaction time and therefore, the mass loss drastically decreased. When reaction temperature increased, the reacted fraction quickly increased because of the short reaction time. In the case of fluidization that was not under vibration, SEM and TEM analysis of the products showed agglomeration and chemical bonding. However, with a vibration, no agglomeration occurred, and a porous surface appeared. For fluidization under vibration, energy-dispersive X-ray spectroscopy and mapping analysis of products showed that the oxygen content and distribution decreased, and a small amount of oxygen remained surrounding the product surface. Agglomeration occurred again at higher values, with a superficial gas velocity of 0.45 m/s and vibration frequency of 60 Hz. It has also confirmed that the vertical vibration relieves the forces between fine cohesive particles to eliminate agglomeration and give them an active fluidization state.

Flow and heat transfer characteristics of microchannel flow boiling enhancement with channel configurations

The heat dissipation problem encountered in the process of the development of new electronic equipment and mechanical components towards miniaturization has become the bottleneck of continuous progress in the field of mechanical and electronic control engineering, and the flow boiling heat transfer technology in microchannel may provide the effective cooling guarantee for this purpose. Given the reasonable operating temperature ranges of devices and the diversity of coolant evaporation temperature and pressure choices, refrigerants have become an important option, especially for zeotropic mixtures, which can not only modulate the properties of pure components, but also present the unique phase change heat transfer characteristics with great application prospects. In the present study, the flow boiling heat transfer research of R134a/R245fa zeotropic mixtures as well as their pure compartments in parallel multi-microchannel with continuous and segmented channel configurations were experimentally studied. Each microchannel test section consisted of seven parallel channel passages with the same total length of 110 mm. The cross-sectional area of each channel passage was 2 mm × 1mm (width×height) with the slab width of 0.5 mm. What difference from continuous microchannel was that 10 mm-long interconnected area was arranged every 30 mm along the channel length in segmented one. The experiments were carried out at the same inlet saturation temperature of 26 °C under the conditions comprising the heat flux range of 20− 350 kW/m2 and mass flux range of 300− 400 kg/(m2 s), respectively. In order to obtain more accurate data matching relationship, the analysis of heat transfer performance focused on the region near the outlet of the test sections. It’s worth noting that the multi-microchannel should be treated as fin effects during the heat transfer data reduction. The ribbed slabs could be considered as the rectangular straight fins either for continuous or segmented multi-microchannel. The results showed that compared with continuous microchannel, the heat transfer performance was slightly enhanced for pure components while slightly suppressed for zeotropic mixtures in segmented microchannel at lower effective heat flux. With the increase of effective heat flux, the heat transfer suppression effect of zeotropic mixtures was gradually weakened. The interconnected area was helpful to delay the occurrence of the transfer deterioration and improve the flow boiling CHF regardless of pure or zeotropic refrigerants. Besides, the flow boiling pressure drop in segmented microchannel was obviously reduced for zeotropic mixtures and their pure components. The smaller the liquid-vapor density ratio of test refrigerants, the higher the reduction of pressure drop with the help of interconnected area. For zeotropic mixtures, the flow boiling pressure drop was smaller at lower effective heat flux and the increasing trend of pressure drop on heat flow is slower.

Filtration Performance Characteristics of Sticky Aerosol Using Calcium Hydroxide

This study examined the performance of removing aerosol upon a flow rate variable by agglomerating sticky aerosol with calcium hydroxide and removing cohesive aerosol through an experimental apparatus, simulating an actual painting booth. As a result of examining the performance of the filter by fixing the paint spray quantity, the calcium hydroxide input and the filtration area under variable flow rates of 5, 10, and 15 Nm3/min, we confirmed that the filter performance has long average aerosol removing intervals at the 5 Nm3/min flow rate. At the 5 Nm3/min flow rate, there is a low residual pressure drop trend and high fractional collection efficiency, and a high level of total collection efficiency is maintained at 99.42%. When the flow rate is less than 5 Nm3/min, the aerosol settling and experimentation was impossible. With this research, the optimal conditions for the use of sticky aerosol have been examined.

Waterflooding oil-saturated core samples - Analytical solutions for steady-state capillary end effects and correction of residual saturation

Capillary end effects can play an important role when interpreting or designing a core flood experiment. The outlet of the core is characterized by a zero capillary pressure which can trap wetting phase in a region near the outlet of the core, potentially leading to a wrongful estimation of parameters such as residual saturation and relative permeability. We consider the steady state obtained in a core flooding experiment: one fluid (assumed water) is continuously injected and produced, while a second fluid (assumed oil), displaced during a transient production phase, is completely immobilized during the considered steady state due to entrapment. An analytical model is derived giving an explicit formulation of the saturation and pressure distributions, the average saturation and the pressure drop at this steady state. The model is general enough to consider different wetting states as given macroscopically by a capillary pressure curve that can vanish at a selected saturation and function shapes and magnitudes that can be adjusted. To our knowledge previous works have been limited to implicit relations between the mentioned parameters and also been restricted to strongly wetted media, which underlines one part of the novelty in this work. A second novel result from this work is that it is possible to derive meaningful capillary numbers that incorporate saturation function parameters. The model predicts a position LE (measured from the outlet) where the end effects become negligible. At the critical value 1 of our dimensionless number N (which also includes saturation function parameters) the end effects exactly reach the inlet position. The model shows different behavior according to whether N>1 (strong advective forces) or if N<1 (strong capillary forces). In the first case, both scaled pressure drop (relative to the pressure drop without end effects) and average saturation change proportionally to the inverse of N (and accordingly, the inverse of injection rate). In this regime the curves can be scaled uniquely and we can specify physically meaningful capillary numbers incorporating all saturation function parameters. The pressure drop and average saturation behave differently with the saturation function parameters and thus scale with different dimensionless numbers. For N<1 the average saturation and pressure drop do not scale easily according to one capillary number, but the model can easily and intuitively explain variations in the behavior resulting from changes in these parameters. We show that it is possible, based on a simple three-rate water flooding test to estimate the water relative permeability curve and the negative capillary pressure curve. A third novel result is that we for the first time provide a theoretical derivation of the intercept method proposed by Gupta and Maloney (2016) from the fundamental equations of multi-phase flow in porous media and extend the amount of information that is obtained from this procedure. The pressure drop trends considered in unscaled variables is equivalent to their model, stating that at high rates the pressure drop will be linear with rate. Unlike the pressure drop, the saturation will however vary linearly with the inverse of rate. The slopes provide further information about the saturation curve parameters.

Experimental investigation on minichannel parallel flow condenser performance with R22, R410A and R407C

A performance evaluation of minichannel parallel flow (MCPF) condenser in residential/commercial refrigeration system has been carried out in calorimeter room with wind tunnel in this paper. The heat rejection and pressure drop characteristics for heat exchangers were compared using R22, R410A and R407C as working fluids. The experimental results showed that heat rejection of MCPF condenser with R410A was higher than that of R22 and R407C by 15.6~26.3% and 12.3~22.7% under full and partial load conditions, respectively. The refrigerant side pressure drop trend of R410A in MCPF condenser was smaller than that of R22 and R407C under the same mass flow rate.

Effect of sub-cooling on performance of a multi-jet two phase cooler with multi-scale porous surfaces

An experimental investigation of the heat transfer and fluid flow characteristics of a jet impingement phase change cooler with smooth pin fin and porous coated pin fin target surfaces is presented. In the investigation, a 5 × 5 jet array with orifice diameter of 0.75 mm was used in combination with HFE-7100 as the coolant. Three different types of porous coated pin fin target surfaces, fabricated with varying particle sizes ranging between 10 μm and 177 μm, were tested. The experimental results show that, when compared to a smooth pin fin surface, the porous coated pin fin surfaces significantly increase the achievable heat transfer coefficient with an enhancement of 79% at a heat flux value of 50 W/cm2 for a 75–100 μm particle size surface. The two-phase heat transfer performance was further enhanced 1.8× by reducing the inlet sub-cooling from 10 K to 5.5 K. Additionally, the addition of a porous coating to the pin fin target surface has a relatively small impact on the cooler pressure drop, which was measured as 1.17 kPa for the 75–100 μm particle size surface compared to 1.0 kPa for the smooth pin-fin surface at 10 K sub-cooling. At a reduced sub-cooling of 5.5 K, the pressure drop obtained with the 75–100 μm particle size surface is approximately 3× higher than the pressure drop at 10 K sub-cooling. This study also reports unique trends in pressure drop that are observed with increasing power density, where a sharp decrease in the pressure drop of the cooler is measured with increase in the heat flux.

Analysis of fluid-dynamic guidelines in diesel particulate filter sizing for fuel consumption reduction in post-turbo and pre-turbo placement

Wall-flow particulate filters are in the present days a standard aftertreatment system widely used in diesel engines to reduce particle emissions and meet emission regulations. This paper deals with the analysis of the macro- and meso-geometry definition of the DPF monoliths from a fluid-dynamic modelling approach. Focus is driven to the analysis of the influence on pressure drop and hence on engine fuel economy.The influence of the DPF volume on the engine performance is analysed with a gas dynamic software including both post-turbo and pre-turbo placement under clean and soot loading conditions. A swept in cell density is also considered for different thermal integrity factors. This approach allows analysing the trends in pressure drop and cell unit geometric parameters defining the monolith thermal and mechanical performance. A discussion considering constant specific filtration area and constant filtration area is performed providing a comprehensive understanding of the DPF and engine response as volume and cellular geometry are changed. Results are leading to rigorously justify known but usually empirical guidelines for DPF design in post-turbo applications. A discussion on the potential for monolith volume reduction in pre-turbo applications with respect to the post-turbo baseline is addressed. This is based on the very low sensitivity of fuel consumption and pressure drop both to volume reduction and soot and ash loading with pre-turbo DPF configuration.