Flow Distribution and Pressure Drop in Steady Airflow Through a Selective Laser Sintered Human Tracheobronchial Airway Model

2003 ◽  
Author(s):  
Kah-Hoe Tan ◽  
Ramkumar N. Parthasarathy ◽  
M. Cengiz Altan ◽  
David L. Johnson ◽  
R. E. Clinkenbeard
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Flow Rates ◽  
Physiological Flow ◽  
Static Pressure Difference ◽  
The Mean ◽  
The Relationship ◽  
Airway Model

The flow distribution and pressure drop of steady airflow in the human central airways were studied experimentally using an anatomically correct, selective laser sintered (SLS) human tracheobronchial airway model. Measurements were made for tracheal flow rates ranging from 0.1 to 2.67 liters per second, which correspond to normal physiological flow ranges. The mean air velocities at the exit orifices of the airway model were detected by means of a pitot static tube connected to a pressure transducer. The flow rates, the average velocities, and the Reynolds numbers in each branch of the airway model were then computed. In addition, the static pressure difference between the trachea and the airway exits was measured. The experimental measurements were used to determine the relationship between pressure drop and flow rate. The ratio of inlet to total exit area of the model was identified as a significant factor that influenced the pressure drop. The results obtained in the present study will be particularly useful for validating computational studies.

Study of Liquid Injection on Pressure Drop of Refrigerant Mixtures Inside Enhanced Surface Tubing

2005 ◽  
Author(s):  
S. M. Sami ◽  
J. Comeau
Keyword(s):  
Pressure Drop ◽  
Positive Impact ◽  
Reynolds Numbers ◽  
Two Phase ◽  
Flow Rates ◽  
Refrigerant Mixtures ◽  
Liquid Injection ◽  
Mass Flow Rates ◽  
Flow Pressure ◽  
Enhanced Surface

Two phase flow pressure drop characteristics observed under liquid injection during boiling of refrigerant mixtures R-404A, R407C and R507 as well as R-410A are presented in this paper. Experiments showed that liquid injection tends to decrease the pressure drop during boiling which will have positive impact in increasing the boiling heat transfer rate, heat flux and system efficiency. However, condensation data demonstrated that liquid injection increases the pressure drop. In addition, the data also reveals that the refrigerant under investigation exhibit the same behaviour at higher Reynolds numbers or mass flow rates.

Pressure drop and power dissipation in oscillatory wavy-walled-tube flows

1988 ◽  
Vol 187 ◽  
pp. 573-588 ◽  
Author(s):  
M. E. Ralph
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Power Dissipation ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Frequency Parameter ◽  
Mean Power ◽  
Pressure Drops ◽  
The Mean

Pressure drops occurring in oscillatory viscous flows in wavy-walled tubes have been studied experimentally, for Reynolds numbers up to 1500 and Strouhal numbers in the range 0.005 to 0.02, and by numerical solution of the Navier-Stokes equations, for Reynolds numbers up to 200 and Strouhal numbers between 0.005 and 0.1. Agreement was good for values of the mean modulus of the pressure drop at lower Strouhal numbers and for values of the mean power dissipation at all Strouhal numbers.Numerical solutions have shown that the pressure drop may vary non-sinusoidally, even though the imposed variation in flow rate is sinusoidal. This cannot be explained by the nonlinearity of the steady pressure drop-flow rate relationship, and arises because the velocity field is not quasi-steady. In particular energy may be stored in strong vortices formed during the acceleration phase of the flow cycle, and partially returned to the main flow later. The peak pressure drops in such flows, which are associated with the formation of these vortices, can be almost twice as large as values predicted by adding the appropriate quasi-steady and unsteady inertial contributions. This finding is important in the wider context of unsteady conduit flow.The dependences of the mean modulus of the pressure drop and the mean power dissipation on the Strouhal number and frequency parameter were investigated in detail numerically for two geometries. It was not possible to reduce either dependence to a function of a single parameter. The ‘equivalent’ straight-walled tube for power dissipation was found to have a smaller bore than that for pressure drop, leading to smaller ‘phase angles’ than might have been expected at large values of the frequency parameter. This is because as the pressure drop becomes increasingly dominated by unsteady inertia, there remain relatively large recirculations in which energy is dissipated.

scholarly journals Numerical Simulation of the Performance Characteristics of the Hybrid Closed Circuit Cooling Tower

2008 ◽  
Vol 13 (1) ◽  
pp. 89-101 ◽  
Author(s):  
M. M. A. Sarker ◽  
E. Kim ◽  
G. C. Moon ◽  
J. I. Yoon
Keyword(s):  
Pressure Drop ◽  
Experimental Measurement ◽  
Cooling Tower ◽  
Cfd Simulation ◽  
Air Flow ◽  
Flow Distribution ◽  
Cooling Capacity ◽  
Performance Characteristics ◽  
Closed Circuit ◽  
Flow Rates

The performance characteristics of the Hybrid Closed Circuit Cooling Tower (HCCCT) have been investigated applying computational fluid dynamics (CFD). Widely reported CFD techniques are applied to simulate the air-water two phase flow inside the HCCCT. The pressure drop and the cooling capacity were investigated from several perspectives. Three different transverse pitches were tested and found that a pitch of 45 mm had lower pressure drop. The CFD simulation indicated that when air is supplied from the side wall of the HCCCT, the pressure drop can be over predicted and the cooling capacity can be under predicted mainly due to the non-uniform air flow distribution across the coil bank. The cooling capacity in wet mode have been calculated with respect to wet-bulb temperature (WBT) and cooling water to air mass flow rates for different spray water volume flow rates and the results were compared to the experimental measurement and found to conform well for the air supply from the bottom end. The differences of the cooling capacity and pressure drop in between the CFD simulation and experimental measurement in hybrid mode were less than 5 % and 7 % respectively for the uniform air flow distribution.

scholarly journals Heat Transfer Enhancement by Perforated and Louvred Fin Heat Exchangers

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 400
Author(s):  
Miftah Altwieb ◽  
Rakesh Mishra ◽  
Aliyu M. Aliyu ◽  
Krzysztof J. Kubiak
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
Flow Rates ◽  
Pressure Drops ◽  
Fin Design

Multi-tube multi-fin heat exchangers are extensively used in various industries. In the current work, detailed experimental investigations were carried out to establish the flow/heat transfer characteristics in three distinct heat exchanger geometries. A novel perforated plain fin design was developed, and its performance was evaluated against standard plain and louvred fins designs. Experimental setups were designed, and the tests were carefully carried out which enabled quantification of the heat transfer and pressure drop characteristics. In the experiments the average velocity of air was varied in the range of 0.7 m/s to 4 m/s corresponding to Reynolds numbers of 600 to 2650. The water side flow rates in the tubes were kept at 0.12, 0.18, 0.24, 0.3, and 0.36 m3/h corresponding to Reynolds numbers between 6000 and 30,000. It was found that the louvred fins produced the highest heat transfer rate due to the availability of higher surface area, but it also produced the highest pressure drops. Conversely, while the new perforated design produced a slightly higher pressure drop than the plain fin design, it gave a higher value of heat transfer rate than the plain fin especially at the lower liquid flow rates. Specifically, the louvred fin gave consistently high pressure drops, up to 3 to 4 times more than the plain and perforated models at 4 m/s air flow, however, the heat transfer enhancement was only about 11% and 13% over the perforated and plain fin models, respectively. The mean heat transfer rate and pressure drops were used to calculate the Colburn and Fanning friction factors. Two novel semiempirical relationships were derived for the heat exchanger’s Fanning and Colburn factors as functions of the non-dimensional fin surface area and the Reynolds number. It was demonstrated that the Colburn and Fanning factors were predicted by the new correlations to within ±15% of the experiments.

Flow and Pressure Measurement in a Selective Laser Sintered Human Tracheobronchial Airway Model Under Cyclic Flow Conditions

Volume 1 ◽  
2004 ◽  
Author(s):  
O. Pulat ◽  
R. N. Parthasarathy
Keyword(s):  
Flow Distribution ◽  
Volumetric Flow Rate ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Flow Rates ◽  
Periodic Flows ◽  
Cyclic Flow ◽  
Human Male ◽  
The Right ◽  
Airway Model

A selectively laser sintered human tracheobronchial airway model was used to study periodic flows at different frequencies corresponding to inhalation and exhalation. The model was fabricated from a 3-d point could based on the Visible Human Male Project. The objective was to document the volumetric flow rate and pressure drop under periodic flow conditions and compare these values with those obtained in steady flow. The flow was cycled via a Programmable Logic computer (PLC) at a specified breathing frequency of 12 breaths per minute. The tracheal flows rate studied were 30, 50, and 120 liters per minute. The results indicated that significant differences existed between flow measurements made under steady conditions and periodic conditions; these differences became significant at high flow rates. The flow distribution in the right and left side of the airway model was asymmetric. The results also indicated the existence of both turbulent and laminar flow regimes at all tracheal flow rates.

Experimental Study on Discharge Coefficients of Windward Window in Buildings with Wind-Driven Cross Ventilation

2014 ◽  
Vol 1008-1009 ◽  
pp. 1061-1067
Author(s):  
Qiao Ning Wang ◽  
Yan Ling Guan ◽  
Qi Hai Liao
Keyword(s):  
Flow Rate ◽  
Natural Ventilation ◽  
Discharge Coefficient ◽  
Static Pressure ◽  
Flow Rates ◽  
Discharge Coefficients ◽  
Window Opening ◽  
Static Pressure Difference ◽  
Window Area ◽  
The Impact

Focus on the prediction of flow rates in buildings under natural ventilation, the investigation conducted a series of model rooms with cross ventilation. The impact of window-wall ratios, windows configurations as well as corresponding flow rates was investigated. The object of this investigation is to analyze characteristics of windward window opening discharge coefficient by measuring static pressure difference and the flow rate through windows. The conclusion are as follows: For large openings, the discharge coefficient of windward window opening increases as the window-wall ratio grows up; With windward window-wall ratio of 44.4% and 11.1%, the discharge coefficient of windward openings is almost irrelevant to flow rate and less affected by leeward window area; However, with windward window-wall ratio of 2.78%, the discharge coefficient increases slightly as flow rate rises, and the larger the area of leeward opening is, the smaller the discharge coefficient of windward opening becomes.

scholarly journals Performance Analysis of a Multiple Micro-Jet Impingements Cooling Model

2016 ◽  
Vol 15 (2) ◽  
pp. 58
Author(s):  
A. Husain ◽  
N.A. Al-Azri ◽  
A. Samad ◽  
K.Y. Kim
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Temperature Rise ◽  
Reynolds Numbers ◽  
Coefficient Of Performance ◽  
Maximum Temperature ◽  
Temperature Uniformity ◽  
Pumping Power ◽  
Flow Rates ◽  
Maximum Temperature Rise

The present study investigates the thermal performance of a multiple micro-jet impingements model for electronics cooling. The fluid flow and heat transport characteristics were investigated for steady incompressible laminar flow by solving three-dimensional (3D) Navier-Stokes equations. Several parallel and staggered micro-jet configurations (ie. inline 2 Å~ 2, 3 Å~ 3 and 4 Å~ 4 jets, and staggered five-jet and 13-jet arrays with the jet diameter to the channel height ratios from 0.25–0.5) were analyzed at various flow rates for the maximum temperature rise, pressure drop, heat-transfer coefficient, thermal resistance, and pumping power characteristics. The parametric investigation was carried out based on the number of jets and the jet diameters at various mass flow rates and jet Reynolds numbers. Temperature uniformity and coefficient of performance were evaluated to find out the trade-off among the various designs investigated in the present study. The maximum temperature rise and the pressure drop decreased with an increase in the number of jets except in the case of staggered five-jet array. A higher temperature uniformity was observed at higher flow rates with a decrease in the coefficient of performance. The performance parameters, such as thermal resistance and pumping power, showed a conflicting nature with respect to design variables (viz. jet diameter to stand-off ratio and interjet spacing or number of jets) at various Reynolds numbers within the laminar regime. 

Experimental and numerical investigation of pressure drop coefficient and static pressure difference in a tangential inlet cyclone separator

2012 ◽  
Vol 66 (11) ◽  
Author(s):  
Fuat Kaya ◽  
Irfan Karagoz
Keyword(s):  
Pressure Drop ◽  
Pressure Difference ◽  
Static Pressure ◽  
Numerical Technique ◽  
Pipe Length ◽  
Inlet Velocity ◽  
Viscous Forces ◽  
Static Pressure Difference ◽  
High Reynolds ◽  
Experimental Data Analysis

AbstractThe aim of this study was to investigate the pressure drop coefficient and the static pressure difference related to the natural vortex length and to evaluate the results for gas-particle applications. CFD simulations were carried out using a numerical technique which had been verified previously. Results obtained from the numerical simulations were compared with the experimental data. Analysis of the results showed that the pressure drop coefficient decreases with the increasing inlet velocity, becoming almost constant above a certain value of the inlet velocity. The reason is that the effect of viscous forces decreases at high Reynolds numbers. The pressure drop coefficient also decreases with the increasing exit pipe diameter and decreasing exit pipe length.

scholarly journals Influence of Hydrophobic Fin Configuration in Thermal System in Relation to Electronic Device Cooling Applications

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1631
Author(s):  
Shahzada Zaman Shuja ◽  
Bekir Sami Yilbas ◽  
Hussain Al-Qahtani
Keyword(s):  
Nusselt Number ◽  
Pressure Drop ◽  
Electronic Device ◽  
Cooling System ◽  
Flow Analysis ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Solution Domain ◽  
Uniform Flow Distribution ◽  
Temperature Parameter

In this study, heat and flow analysis of the cooling system incorporating fins with hydrophilic and hydrophobic wetting surfaces has been considered in relation to electronic cooling applications. Temperature and velocity fields in the solution domain are simulated for various fin numbers and sizes. A temperature parameter is introduced to assess the thermal performance of the system. Fin count is introduced to formulate the number of fins in the solution domain. The Nusselt number and pressure drop between the inlet and exit ports due to different fin configurations of the cooling system for various fin counts are presented. It is found that the temperature parameter attains high values for large sizes and small fin counts, which is more pronounced for low Reynolds numbers. Increasing number of fins results in almost uniform flow distribution among the fin, which is more pronounced for the hydrophobic fin configuration. The Nusselt number attains larger values for the hydrophilic fin configuration than that corresponding to the hydrophobic fin, and it attains a peak value for certain arrangement of fin count, which differs with the Reynolds number. The pressure drop between the inlet and exit ports reduces for hydrophobic fin; hence the slip velocity introduced for hydrophobic fin improves the pressure drop by 6% to 16% depending on the fin counts in the cooling system.

Measurements of the Turbulence Structure Downstream of a Tube Bundle at High Reynolds Numbers

1994 ◽  
Vol 116 (4) ◽  
pp. 848-855 ◽  
Author(s):  
U. Karnik
Keyword(s):  
Natural Gas ◽  
Static Pressure ◽  
Tube Bundle ◽  
Reynolds Numbers ◽  
Turbulence Structure ◽  
Mean Velocity ◽  
Diameter Pipe ◽  
The Mean ◽  
High Reynolds ◽  
Hot Film

Mean and turbulent velocity profiles are measured in natural gas at a static pressure of approximately 5200 kPa and a Reynolds number of around 7 × 106. These measurements are obtained by conventional hot film anemometry suitably modified for use in a natural gas environment. Measurements are taken in a 102.26 mm nominal diameter pipe following a development length of around 76D. The mean velocity profile and the turbulence intensities at this location are typical for a fully developed pipe flow. Further, measurements downstream of a 19 tube bundle flow conditioner are also presented. The tube bundle is traversed downstream of a 90 degree, long radius (r = 1.5D) elbow and the measurements are taken at 19D downstream of the elbow exit. Measurements include those of the axial mean and turbulent velocities and the integral length scales. It is found that the decay of turbulence is slower and the magnitude of the length scale is smaller in comparison to measurements at lower Reynolds numbers. Orifice meter comparisons, performed in a 19D test section (meter run), confirm earlier findings that turbulence is one of the factors that affects orifice meter accuracy.

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