Peak Pressure Drop Research Articles

Heat transfer enhancement in pressurized solar cavity receivers with densely packed metallic wire mesh

Pressurized solar receivers are promising candidates as heat sources for integration with high-efficiency closed-loop air and supercritical carbon-dioxide based Brayton cycles. This paper focuses on the heat transfer enhancement of such a solar receiver using inline stacked wire mesh fibers in the heat transfer fluid flow path. The study involves modelling, characterization, and performance evaluation of a cavity-receiver with densely packed wire meshes. A new experimentally validated hybrid numerical approach is presented for modelling the inline stacked wire mesh layers. Initially, a direct numerical simulation at the pore scale on a representative elementary volume (REV) of the wire mesh geometry is performed for determining the hydrodynamic and thermal characteristics of the medium. Subsequently, these hydrodynamic and thermal properties are used to define a volume-averaged macroscopic porous medium. Experiments are performed using a rectangular channel stacked with stainless steel wire meshes, heated using a plate heater, and pressurized air supplied using a reciprocating compressor. Both numerical and experimental studies are performed for a Reynolds number range of 28 to 213 resulting in a Nusselt number range of 7.2 to 213. The porous medium model predictions for pressure gradient are within 17 %, while predictions for outlet air temperature are within 5 % of the experimentally obtained values. The study predicts a maximum heat transfer enhancement of five times in a channel stacked with wire meshes compared to the case of a clear channel, but incurring a peak pressure drop of only about 1.1 kPa.

Evolution of cardiac tissue and flow mechanics in developing Japanese Medaka.

The effects of pressure drop across cardiac valve cushion regions and endocardial wall strain in the early developmental stages of a teleost species heart are poorly understood. In the presented work, we utilize microscale particle image velocimetry (μPIV) flow measurements of developing medaka hearts from 3 to 14 dpf (n = 5 at each dpf) to quantify the pressure field and endocardial wall strain. Peak pressure drop at the atrioventricular canal (ΔPAVC) and outflow tract (ΔPOFT) show a steady increase with fish age progression. Pressure drops when non-dimensionalized with blood viscosity and heart rate at each dpf are comparable with measurements in zebrafish hearts. Retrograde flows captured at these regions display a negative pressure drop. A novel metric, Endocardial Work (EW), is introduced by analyzing the ΔPAVC-strain curves, which is a non-invasive measure of work required for ventricle filling. EW is a metric that can differentiate between the linear heart stage (< 100 Pa-%), cardiac looped chamber stage (< 300 Pa-%), and the fully formed chamber stage (> 300 Pa-%).

Numerical study on heat dissipation of double layer enhanced liquid cooling plate for lithium battery module

The thermal management system's architecture is crucial for lithium batteries' efficiency and financial viability, predominantly influencing their security and longevity. We conceptualized a double-layer enhanced LCP, meticulously crafted to augment the heat dissipation capabilities of the battery assembly. This novel design targets the reduction of peak temperatures and pressure drops, fostering an even internal temperature profile. Comprehensively evaluate the performance of different settings of the coolant cooling system, and the monitoring points are strategically set in horizontal and vertical directions. Analyzing the data, it becomes evident that the system's vertical orientation significantly affects the battery module's peak temperature and temperature variation. Furthermore, extensive investigations were conducted on the impact of layout, coolant flow rate, and inlet temperature on thermal dissipation. Our findings indicate that the double-layer enhanced liquid cooling plates outperform conventional designs. There is a substantial 2.41 % decrease in the peak battery module temperature and an 80.6 % reduction in voltage decline. Operating at a flow rate of 10 g per second and an entry temperature of 25 °C, our liquid cooling system demonstrates superior cooling efficiency with minimal power consumption. It proficiently restrains the maximum battery module temperature below 30.43 °C and restricts temperature variance to merely 3.48 °C. The suggested approach in this research contributes to improved thermal equilibrium, diminishes temperature disparities and pressure concerns, thereby fostering the technological advancement of electric vehicle's liquid cooling systems.

Effect of different degrees of adenoid hypertrophy on pediatric upper airway aerodynamics: a computational fluid dynamics study.

To improve the diagnostic accuracy of adenoid hypertrophy (AH) in children and prevent further complications in time, it is important to study and quantify the effects of different degrees of AH on pediatric upper airway (UA) aerodynamics. In this study, based on computed tomography (CT) scans of a child with AH, UA models with different degrees of obstruction (adenoidal-nasopharyngeal (AN) ratio of 0.9, 0.8, 0.7, and 0.6) and no obstruction (AN ratio of 0.5) were constructed through virtual surgery to quantitatively analyze the aerodynamic characteristics of UA with different degrees of obstruction in terms of the peak velocity, pressure drop (△P), and maximum wall shear stress (WSS). We found that two obvious whirlpools are formed in the anterior upper part of the pediatric nasal cavity and in the oropharynx, which is caused by the sudden increase in the nasal cross-section area, resulting in local flow separation and counterflow. In addition, when the AN ratio was ≥ 0.7, the airflow velocity peaked at the protruding area in the nasopharynx, with an increase 1.1-2.7 times greater than that in the nasal valve area; the △P in the nasopharynx was significantly increased, with an increase 1.1-6.8 times greater than that in the nasal cavity; and the maximum WSS of the posterior wall of the nasopharynx was 1.1-4.4 times larger than that of the nasal cavity. The results showed that the size of the adenoid plays an important role in the patency of the pediatric UA.

Aortic Stenosis: Haemodynamic Benchmark and Metric Reliability Study

Aortic stenosis is a condition which is fatal if left untreated. Novel quantitative imaging techniques which better characterise transvalvular pressure drops are being developed but require refinement and validation. A customisable and cost-effective workbench valve phantom circuit capable of replicating valve mechanics and pathology was created. The reproducibility and relationship of differing haemodynamic metrics were assessed from ground truth pressure data alongside imaging compatibility. The phantom met the requirements to capture ground truth pressure data alongside ultrasound and magnetic resonance image compatibility. The reproducibility was successfully tested. The robustness of three different pressure drop metrics was assessed: whilst the peak and net pressure drops provide a robust assessment of the stenotic burden in our phantom, the peak-to-peak pressure drop is a metric that is confounded by non-valvular factors such as wave reflection. The peak-to-peak pressure drop is a metric that should be reconsidered in clinical practice.Graphical abstractThe left panel shows manufacture of low cost, functional valves. The central section demonstrates circuit layout, representative MRI and US images alongside gross valve morphologies. The right panel shows the different pressure drop metrics that were assessed for reproducibility

Non-invasive cardiovascular magnetic resonance assessment of pressure recovery distance after aortic valve stenosis

BackgroundDecisions in the management of aortic stenosis are based on the peak pressure drop, captured by Doppler echocardiography, whereas gold standard catheterization measurements assess the net pressure drop but are limited by associated risks. The relationship between these two measurements, peak and net pressure drop, is dictated by the pressure recovery along the ascending aorta which is mainly caused by turbulence energy dissipation. Currently, pressure recovery is considered to occur within the first 40–50 mm distally from the aortic valve, albeit there is inconsistency across interventionist centers on where/how to position the catheter to capture the net pressure drop. MethodsWe developed a non-invasive method to assess the pressure recovery distance based on blood flow momentum via 4D Flow cardiovascular magnetic resonance (CMR). Multi-center acquisitions included physical flow phantoms with different stenotic valve configurations to validate this method, first against reference measurements and then against turbulent energy dissipation (respectively n = 8 and n = 28 acquisitions) and to investigate the relationship between peak and net pressure drops. Finally, we explored the potential errors of cardiac catheterisation pressure recordings as a result of neglecting the pressure recovery distance in a clinical bicuspid aortic valve (BAV) cohort of n = 32 patients. ResultsIn-vitro assessment of pressure recovery distance based on flow momentum achieved an average error of 1.8 ± 8.4 mm when compared to reference pressure sensors in the first phantom workbench. The momentum pressure recovery distance and the turbulent energy dissipation distance showed no statistical difference (mean difference of 2.8 ± 5.4 mm, R2 = 0.93) in the second phantom workbench. A linear correlation was observed between peak and net pressure drops, however, with strong dependences on the valvular morphology. Finally, in the BAV cohort the pressure recovery distance was 78.8 ± 34.3 mm from vena contracta, which is significantly longer than currently accepted in clinical practise (40–50 mm), and 37.5% of patients displayed a pressure recovery distance beyond the end of the ascending aorta. ConclusionThe non-invasive assessment of the distance to pressure recovery is possible by tracking momentum via 4D Flow CMR. Recovery is not always complete at the ascending aorta, and catheterised recordings will overestimate the net pressure drop in those situations. There is a need to re-evaluate the methods that characterise the haemodynamic burden caused by aortic stenosis as currently clinically accepted pressure recovery distance is an underestimation.

Investigation of Asphaltene Deposition in Horizontal Flow Above and Below the Heavy-Phase Glass Transition

Asphaltene deposition is a longstanding flow assurance issue and has been much investigated at near-ambient temperatures where asphaltenes typically precipitate as glassy particles. However, there are few data available at higher temperatures where an asphaltene-rich phase may come out of solution as liquid droplets. An apparatus was designed and commissioned to investigate deposition mechanisms over a range of temperatures in horizontal laminar flow using a test fluid of bitumen diluted with n-heptane. The pressure drop through a 1.75 mm I.D. capillary tube was monitored for indications of deposition during the flow period, and the tube was removed at the end of each experiment to measure the mass and location of the deposit. Asphaltene deposition was assessed considering the following variables: capillary tube lengths from 3 to 30 cm, n-heptane contents in the feed from 65 to 90 wt %, fluid flow rates of 2 and 4 cm3/min, and temperatures of 50, 90, and 130 °C. In the glassy particle regime (50 and 90 °C), a highly porous localized deposit formed near the inlet of the capillary tube. Cycles of deposition and erosion were observed during the flow period. However, in the liquid droplet regime (130 °C), periodically unstable stratified flow was observed. The heavy-phase holdup at the peak pressure drop was ∼88% of the capillary tube volume. The n-heptane content of the heavy phase was consistent with equilibrium heavy-phase compositions reported in the literature. The results suggest that some assumptions made in the models developed for asphaltene particle deposition may not apply in high-temperature applications where the asphaltene-rich phase separates as liquid droplets.

Dynamic simulation of aortic valve stenosis using a lumped parameter cardiovascular system model with flow regime dependent valve pressure loss characteristics.

Valvular heart diseases are growing concern in impoverished parts of the world, such as Southern-Africa, claiming more than 31 % of total deaths related to cardiovascular diseases. The ability to model the effects of regurgitant and obstructive lesions on the valve body can assist clinicians in preparing personalised treatments. In the present work, a multi-compartment lumped parameter model of the human cardiovascular system is developed, with a newly proposed valve modelling approach which accounts for geometry and flow regime dependent pressure drops along with the valve cusp motion. The model is applied to study various degrees of aortic stenosis using typical human cardiovascular parameters. The predicted transvalvular pressure drops for the different modelling approaches are compared to typical measured mean and peak gradients found in literature for severely stenosed aortic valves. The comparison between the predicted and measured values show that the previously published valve models under predicts expected severely stenosed peak and mean transvalvular pressure drops by approximately 47% and 25% respectively, whereas the newly proposed model under predicts the peak pressure drop by 25% and over predicts mean pressure drop by 7%.

Analysis of slamming loads on a catamaran section with a centre-bow appended by spray rail

ABSTRACT Wave-piercing catamarans have center-bow to diminish slamming pressure and acceleration in sea waves. Bow section modification of marine craft towards low slamming loads is an on-going research topic. This study suggests insertion of a flat-bar, called spray rail, to center-bow to reduce both slamming pressure and acceleration. A section which is called J1-section from previous research is adopted for further modification. Modification is made via appending the spray rail to its center-bow, and the new section is called J1-section with spray rail. Evaluation of the slamming pressure and acceleration of both sections are experimentally accomplished using the water entry test facilities of Amirkabir Laboratory of Hydrodynamics. J1-section with spray rail in comparison with J1-section has shown peak acceleration and pressure drop of about 60% and 70%, respectively. This study suggests that the insertion of appendages to the catamaran sections is a superior solution for the slamming impact load reduction.

Assessment of pressure drop in conical spouted beds of biomass by artificial neural networks and comparison with empirical correlations

Pressure drop is an essential parameter in the operation of conical spouted beds (CSB) and depends on its geometric factors and materials used. Irregular materials, like biomass, are complex to treat and, unlike other gas–solid contact methods, CSB turn out to be a suitable technology for their treatment. Artificial neural networks were used in this study for the prediction of operating and peak pressure drops, and their performance has been compared with that of empirical correlations reported in the literature. Accordingly, a multi-layer perceptron network with backward propagation was used due to its ability to model non-linear multivariate systems. The fitting of the experimental data of both operating and peak pressure drop was significantly better than those reported in the literature, specifically in the case of the peak pressure drop, with R2 being 0.92. Therefore, artificial neural networks have been proven suitable for the prediction of pressure drop in CSB.

Estimation of the minimum spouting velocity and pressure drop in open-sided draft tube spouted beds using genetic programming

Explicit dimensionless models are proposed for estimating the minimum spouting velocity, operating pressure drop and peak pressure drop in open-sided draft tubes spouted bed using the genetic programming (GP). The models are developed based on 664 experimental data for minimum spouting velocity, 660 for peak pressure drop and 652 for operating pressure drop. The parameters of significant influence are considered as GP input variables, and reliable semi-empirical correlations have been obtained. The models predict the hydrodynamic parameters analyzed with average absolute relative errors of 12.90%, 15.99% and 10.92% for the minimum spouting velocity, peak pressure drop and operating pressure drop, respectively. A comparison of literature correlations with the present ones shows that the latter lead to considerably lower errors from the experimental data. The prediction capability of the new models was evaluated in a range of operating and geometric conditions and a close agreement with the experimental data was observed.

Smart computing approach for design and scale-up of conical spouted beds with open-sided draft tubes

Open-sided draft tubes provide an optimal gas distribution through a cross flow pattern between the spout and the annulus in conical spouted beds. The design, optimization, control, and scale-up of the spouted beds require precise information on operating and peak pressure drops. In this study, a multi-layer perceptron (MLP) neural network was employed for accurate prediction of these hydrodynamic characteristics. A relatively huge number of experiments were accomplished and the most influential dimensionless groups were extracted using the Buckingham-pi theorem. Then, the dimensionless groups were used for developing the MLP model for simultaneous estimation of operating and peak pressure drops. The iterative constructive technique confirmed that 4-14-2 is the best structure for the MLP model in terms of absolute average relative deviation (AARD%), mean square error (MSE), and regression coefficient (R2). The developed MLP approach has an excellent capacity to predict the transformed operating (MSE=0.00039, AARD%=1.30, and R2=0.76099) and peak (MSE=0.22933, AARD%=11.88, and R2=0.89867) pressure drops.

Raman Spectroscopy Diagnostics of the Local Time Profile of an Ultrasound Beam in Water

It has been demonstrated for the first time that pulsed laser Raman spectroscopy can be used for diagnostics of a local acoustic pressure profile with a peak pressure drop of 50 MPa and a carrier frequency of 2.0 MHz in the focus of an ultrasound beam propagating in water. A 527-nm 10-ns laser pulse has been focused into the waist of the ultrasound beam at an angle of 90°. Backscattered photons have been recorded in a gated spectrum analyzer. It has been found that the Raman spectra at the times corresponding to the maximum and minimum acoustic pressures are significantly different. This feature has been used for point-to-point reconstruction of the acoustic pressure profile; for this purpose, the delay between the ultrasound and laser pulses is consequently increased with a step of 50 ns. It has been shown that, within the measurement error, the resulting changes in the position of the center of the stretching OH vibration band of water molecules in the Raman spectrum reproduce the acoustic pressure profile directly measured using a PVDF hydrophone at the laser sensing point. The results obtained can be used to develop a new method for remote diagnostics of the time profile of acoustic pressure and monitoring the local dynamic of the compression-tension processes in water up to critical pressures corresponding to the cavitation rupture, when the use of the hydrophone can lead to its damage.

Hydrodynamic Characterization of a Shallow Rectangular Spouted Bed Using Bed Pressure Signals and Image Processing Methods

To support the design of spouted bed reactors, experiments are performed in a rectangular spouted bed to measure the peak pressure drop (ΔPmax) and the internal and external spouting velocities (Uis and Ues). Four particle types spanning under Geldart D and B are used. Uis and Ues are measured from bed pressure drop and expansion ratio profiles, respectively, with the Ues/Uis ratio of each particle type obtained. Correlations predicting the ΔPmax of Geldart D and B particles are developed by reviewing published correlations and investigating the nozzle effect. Good prediction is achieved with a slope of 0.997 and an adjusted R2 of 0.998 in a 95% confidence interval. Ues is predicted through correlations developed by adding effects of dp/Di and H0 in the Mathur–Gishler equation. The calculated Ues agrees well with the experimental data, achieving a slope of 0.998 and an adjusted R2 of 0.998 in a 95% confidence interval.

Estimation of valvular resistance of segmented aortic valves using computational fluid dynamics

Aortic valve stenosis is associated with an elevated left ventricular pressure and transaortic pressure drop. Clinicians routinely use Doppler ultrasound to quantify aortic valve stenosis severity by estimating this pressure drop from blood velocity. However, this method approximates the peak pressure drop, and is unable to quantify the partial pressure recovery distal to the valve. As pressure drops are flow dependent, it remains difficult to assess the true significance of a stenosis for low-flow low-gradient patients. Recent advances in segmentation techniques enable patient-specific Computational Fluid Dynamics (CFD) simulations of flow through the aortic valve. In this work a simulation framework is presented and used to analyze data of 18 patients. The ventricle and valve are reconstructed from 4D Computed Tomography imaging data. Ventricular motion is extracted from the medical images and used to model ventricular contraction and corresponding blood flow through the valve. Simplifications of the framework are assessed by introducing two simplified CFD models: a truncated time-dependent and a steady-state model. Model simplifications are justified for cases where the simulated pressure drop is above 10 mmHg. Furthermore, we propose a valve resistance index to quantify stenosis severity from simulation results. This index is compared to established metrics for clinical decision making, i.e. blood velocity and valve area. It is found that velocity measurements alone do not adequately reflect stenosis severity. This work demonstrates that combining 4D imaging data and CFD has the potential to provide a physiologically relevant diagnostic metric to quantify aortic valve stenosis severity.

Paraboloid-Based Spouted Bed Drying of Paddy: Aerodynamics, Temperature Distribution, and Moisture Degradation

Aerodynamics, temperature variations in the annulus, and the moisture reduction of paddy in a paraboloid-based spouted bed (PBSB) dryer without draft tube and with solid and porous draft tubes were investigated. Draft tube caused a rapid decrease in the peak pressure drop and minimum spouting velocity when compared with PBSB without a draft tube. Pressure drops with draft tubes were 17 to 30% of the values for the PBSB without a draft tube. Temperature distribution along the bed height in the annular region during drying of paddy was also investigated. Heat-up in the spouted bed without draft tube was more rapid. The experiments were conducted for 70, 90, and 110 °C inlet air temperatures. The required length of drying time to dry the paddy with an initial moisture content of 0.35 db to a moisture content below 0.15 db could be reduced by 50–60% using a temperature of 110 °C instead of 70 °C. No constant rate period was observed. Drying took place in the falling rate period. Drying time decreased in the case of porous draft tube rather than the solid one. The highest drying rates were achieved by spouted bed without draft tube. Drying rates were in the range of 0.62–0.1, 0.51–0.06, and 0.37–0.06 (db.min−1) for the spouted bed without draft tube, with porous, and solid draft tubes, respectively.

Experimental study of flow boiling of FC-72 in fractal-like flow channels

In this study, symmetrical and dichotomous fractal flow channel designs with various configurations in terms of the number of channels being split into smaller channels, were investigated experimentally for their flow boiling heat transfer performance with FC-72 as the working fluid. A multi-channel parallel channel design depicted as Parallel was used as a benchmark. The channels were fabricated by Selective Laser Melting (SLM). Three mass fluxes were studied, viz., 600, 900 and 1200 kg/m2⋅s. The peak heat transfer coefficient and pressure drop were investigated. High-speed visualization studies were also employed to examine the two-phase behaviors in the channels. The fractal flow channels were found to perform comparably with the Parallel channel at low mass fluxes but achieved higher heat transfer coefficients at higher mass fluxes, with the design n = 2, i.e., channel splitting into smaller channels twice, being the highest. The pressure drops of the fractal flow channel designs are higher than the Parallel channel due to their longer channel lengths, and the flow impacting multiple bifurcations at an angle, with n = 4, i.e., channel splitting into smaller channels four times, experiencing the highest pressure drop for all mass fluxes. Visualization studies show that fractal flow channels cause an early annular flow, enhancing heat transfer. Flow reversals in the Parallel channel were observed especially at higher mass fluxes, which suggest no enhancement in the heat transfer coefficient. The fractal flow channels, however, do not experience any flow reversal which could be attributed to the acceleration of the two-phase flow after each bifurcation, which in turn increases the inertia force to overcome the force from vapor expansion. The visualization studies also suggest that increasing the complexity does not result in better flow boiling heat transfer performance. This is due to the multiple flow separations which resulted in no two-phase heat transfer interaction and thus, under-utilization of the entire channel surface area for heat transfer. A comparison with a general correlation for flow boiling gives mean absolute errors of 31.6% and 35.3% for the fractal flow channels and Parallel, respectively.

Experimental Investigations On The Momentum Pressure Drop During Flow Boiling Of R134a

The article presents experimental investigations of the pressure drop during two-phase flow. Experiments were performed for both adiabatic and heated flow of R134a. Obtained flow patterns were compared with the literature. Obtained data is used to validate momentum pressure drop predictions, a set of graphs showing comparisons, for a representative set of experimental conditions, of the two-phase frictional pressure gradients for the adiabatic and diabatic flow. The model proposed in the article allows to predict both values and peak pressure drop with very good accuracy. Verification of the momentum pressure drop predictions for two-phase adiabatic flow showed that all correlations have good agreement with experimental data.

Tornado-induced wind loads on a low-rise building: Influence of swirl ratio, translation speed and building parameters

Significant parameters that influence tornado-induced wind loads on low-rise buildings are yet to be fully explored. In the current study, the influence of tornado parameters such as swirl ratio and translation speed and building’s spatial parameters such as its distance from the tornado mean path and its orientation with respect to the tornado’s translation direction on tornado-induced wind loads are investigated. A low-rise gable roof building with a roof angle of 35 degrees and a square plan area is chosen for this study. Laboratory simulated tornadoes with two swirl ratios with different ground-surface pressure characteristics, and three translation speeds were used. The 1:200-scaled building model that was used for this study was located on both sides of the simulated tornado’s mean path at several locations up to the distance of several tornado-core radii. At locations where maximum loadings occurred, orientation of the building was changed to explore its effect on peak loads. Results show significantly larger peak load coefficients for the tornado with lower swirl ratio which were comparable to its peak ground surface pressure drop. Peak roof uplift on the building located at the tornado’s mean path is smaller by 6–19% for the lower-swirl tornado case and up to 16% for the higher-swirl tornado case, compared to the other locations, for the three translation speeds investigated. For simulated tornado with lower swirl ratio, measurements showed that peak roof uplift increases with increase in translation speed when building is located on tornado mean path, whereas peak roof uplift decreases with increase in translation speed at locations other than tornado mean path. For tornado with higher swirl ratio, increase in translation speed does not change the maximum peak uplift load. Building experiences maximum horizontal and uplift loads at building orientation angle of −45° and 0° for lower swirl tornado case and −45° and −30° for higher swirl tornado case, respectively, with respect to the translation direction of the tornado.

Study of Pressure Drop in the 2D Spouted Bed with Conical Base of Binary Particle Mixtures: Effects of Particle Size and Density

In this study, the pressure drop for the binary mixtures of particles differing in size and density in a pseudo-2D spouted bed was experimentally studied. A binary mixture of solid particles including sand, Gypsum, and polyurethane was used in the experimental setup. Effects of static bed height, cone angle, particles diameter, and a particles weight fraction on the bed pressure drop were evaluated. The relationship between the peak pressure drops of the binary mixtures to the minimum spouting velocity was discussed. The trend of variation of pressure drop versus superficial gas velocities for binary particle mixtures in the spouted beds was found to be similar with that for the single sized particle system. The particles that sink to the bed bottom are called jetsam, whereas those gathered at the upper section of the bed are called flotsam. At the same air velocity for jetsam and flotsam rich systems, the maximum pressure drop in the jetsam rich system was larger than the flotsam one. The measured values of minimum spouting velocity were compared with some empirical correlations for single sized particles in spouted beds.