scholarly journals An attempt to measure cycloidal rotor fan in a rectangular duct

2021 ◽  
Vol 345 ◽  
pp. 00029
Author(s):  
Tomasz Staśko ◽  
Mirosław Majkut ◽  
Sławomir Dykas ◽  
Krystian Smołka
Keyword(s):  
Air Conditioning ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Velocity Fields ◽  
Laser Doppler ◽  
Marine Propeller ◽  
Rectangular Duct ◽  
Direct Control ◽  
Flow Rates

A fan with cycloidal rotor (CRF) becomes a popular idea in wide application such as aviation, HVAC (heat, ventilation and air conditioning) or marine propeller systems. This is due to advantages such as direct control of the flow direction, larger flow rates than in a conventional machines without cycloidal control. In the presented article, velocity fields of CRF placed in a rectangular channel was measured, using Laser Doppler Anemomentry (LDA) method and thermoanemometric probe (TA).

scholarly journals Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

2001 ◽  
Vol 7 (3) ◽  
pp. 173-181
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen
Keyword(s):  
Flow Rate ◽  
Turbulence Intensity ◽  
Laser Doppler Velocimetry ◽  
Reverse Flow ◽  
Flow Region ◽  
Design Flow ◽  
Laser Doppler ◽  
Centrifugal Fan ◽  
Doppler Velocimetry ◽  
Flow Rates

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Enhanced Heat Transfer in a Flat Rectangular Duct With Streamwise-Periodic Disturbances at One Principal Wall

1983 ◽  
Vol 105 (4) ◽  
pp. 851-861 ◽  
Author(s):  
E. M. Sparrow ◽  
W. Q. Tao
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Rectangular Duct ◽  
Transfer Coefficients ◽  
Local Maxima ◽  
Periodic Disturbances ◽  
Pressure Distributions ◽  
Friction Factors

Experiments were performed in a flat rectangular duct to determine the heat transfer and pressure drop response to periodic, rod-type disturbance elements situated adjacent to one principal wall and oriented transverse to the flow direction. In a portion of the experiments, heat transfer occurred only at the rodded wall, while in the remainder, heat was transferred at both principal walls of the duct. Highly detailed axial distributions of the local heat transfer coefficient were obtained. These distributions revealed the rapid establishment of a periodic (i.e., cyclic) fully developed regime as well as recurring local maxima and minima. Cycle-average, fully developed heat transfer coefficients were evaluated and were found to be much larger than those for a smooth-walled duct. Linear pressure distributions were measured between periodically positioned stations in the fully developed region, and the corresponding friction factors were several times greater than the smooth-duct values. The heat transfer and friction data were very well correlated using parameters that take account of the effective surface roughness associated with the disturbance rods.

A Pulsed Wire Probe for the Measurement of Velocity and Flow Direction in Slowly Moving Air

1984 ◽  
Vol 106 (1) ◽  
pp. 72-78 ◽  
Author(s):  
D. E. Olson ◽  
K. H. Parker ◽  
B. Snyder
Keyword(s):  
Heat Transfer ◽  
Theoretical Model ◽  
Spatial Resolution ◽  
Flow Direction ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Transport Time ◽  
Wire Probe ◽  
Circular Pipes ◽  
Measured Flow

This report describes the theory and operation of a pulsed-probe anemometer designed to measure steady three-dimensional velocity fields typical of pulmonary tracheo-bronchial airflows. Local velocities are determined by measuring the transport time and orientation of a thermal pulse initiated at an upstream wire and sensed at a downstream wire. The transport time is a reproducible function of velocity and the probe wire spacing, as verified by a theoretical model of convective heat transfer. When calibrated the anemometer yields measurements of velocity accurate to ±5 percent and resolves flow direction to within 1 deg at airspeeds ≥10 cm/s. Spatial resolution is ±0.5 mm. Measured flow patterns typical of curved circular pipes are included as examples of its application.

scholarly journals Numerical Analysis of Unsteady Laminar Flow past a Pentagonal Obstacle

2021 ◽  
Vol 10 (2) ◽  
pp. 968-974
Keyword(s):  
Laminar Flow ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Time Frame ◽  
Two Dimensional ◽  
Fluid Inertia ◽  
Time Step ◽  
The Face ◽  
Computational Fluid Dynamics Cfd ◽  
Current Article

The current article dispenses the numerical investigation of a two dimensional unsteady laminar flow of incompressible fluid passing a regular pentagonal obstacle in an open rectangular channel. The centre of attention of this work is the comparison of drag coefficients estimated for two distinct cases based on the orientation of face and corner of an obstacle against the flow direction. The numerical results shows that the corner – oriented obstacle bring about 42% larger value of drag coefficient at Re = 500 than face – oriented obstacle. The substantial growth in the expanse of vortex behind obstacle (presented as a function of fluid inertia 25 < Re < 500) is analyzed through the contours and streamline patterns of velocity field. The two eddies in the downstream become entirely unsymmetrical at Re = 500 for both the cases, whereas; the flow separation phenomena occurs a bit earlier in the face – oriented case at Re = 250. Two dimensional Pressure – Based – Segregated solver is employed to model the governing equations written in velocity and pressure fields. The numerical simulations of unsteady flow are presented for 50 seconds time frame with time step 0.01 by using one of the best available commercial based Computational Fluid Dynamics (CFD) software, ANSYS 15.0.

Viscomagnetic Heat Flux Experiments as a Test of Gas Kinetic Theory in the Burnett Regime

1978 ◽  
Vol 33 (7) ◽  
pp. 749-760 ◽  
Author(s):  
G. E. J. Eggermont ◽  
P. W. Hermans ◽  
L. J. F. Hermans ◽  
H. F. P. Knaap ◽  
J. J. M. Beenakker
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Heat Flux ◽  
External Magnetic Field ◽  
Room Temperature ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Gas Kinetic Theory ◽  
The Magnetic Field ◽  
Good Agreement

In a rarefied polyatomic gas streaming through a rectangular channel, an external magnetic field produces a heat flux perpendicular to the flow direction. Experiments on this “viscom agnetic heat flux” have been performed for CO, N2, CH4 and HD at room temperature, with different orientations of the magnetic field. Such measurements enable one to separate the boundary layer contribution from the purely bulk contribution by means of the theory recently developed by Vestner. Very good agreement is found between the experimentally determined bulk contribution and the theoretical Burnett value for CO, N2 and CH4 , yet the behavior of HD is found to be anomalous.

scholarly journals Non-equilibrium model for solute transport in differently designed biofilters targeting agricultural drainage water

2017 ◽  
Vol 76 (6) ◽  
pp. 1324-1331 ◽  
Author(s):  
Lorenzo Pugliese ◽  
Jacob Bruun ◽  
Charlotte Kjaergaard ◽  
Carl Christian Hoffmann ◽  
Guenter Langergraber
Keyword(s):  
Flow Direction ◽  
Tracer Tests ◽  
Drainage Water ◽  
Degree Of Saturation ◽  
Model Parameters ◽  
Liquid Phase Mass Transfer ◽  
Flow Rates ◽  
Hydraulic Design ◽  
Longitudinal Dispersivity ◽  
Transport Behaviour

Biogeochemical processes in subsurface flow constructed wetlands are influenced by flow direction, degree of saturation and influent loading position. This study presents a simulation tool, which aims to predict the performance of the unit and improve the design. The model was developed using the HYDRUS program, calibrated and verified on previously measured bromide (Br−) pulse tracer tests. Three different hydraulic designs (Horizontal (HF), Vertical upward (VF-up), Vertical downward (VF-down) and two different flow rates: Low (L), and High (H)) were investigated. The model simulated well the Br− transport behaviour and the results underline the importance of the hydraulic design. Calibrated model parameters (longitudinal dispersivity, immobile liquid phase, mass transfer coefficient) showed a common trend for all the designs, for increasing flow rates within the investigated range. The VF-down performed best, i.e. had the highest hydraulic retention time.

Experimental Thermal Behavior of Electronic Chips in a Channel During Pump-On Transient Period

Volume 4 ◽  
2004 ◽  
Author(s):  
H. Bhowmik ◽  
K. W. Tou ◽  
C. P. Tso
Keyword(s):  
Rectangular Channel ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Heat Sources ◽  
Empirical Correlations ◽  
Heat Transfer Characteristics ◽  
Flux Flow ◽  
Flow Rates ◽  
Discrete Heat Sources ◽  
Transient Period

Experiments are performed to study the heat transfer characteristics during the pump-on transient period from an array of 4 × 1 flush mounted discrete heat sources in a vertical rectangular channel using water as the working fluid. The experimental data covers the flow regime with Reynolds number based on heat source length ranging from 1050 to 2625. The applied uniform heat fluxes to the chips are 1, 3, 5 and 7 W/cm2. The effects of heat flux, flow rates and chip numbers are investigated and empirical correlations are developed for investigated and empirical correlations are developed for individual chips as well as for overall data in the transient regime. The transient correlation recommended is Nul/(Pel)1/3 = 3.5(Fo)1/4.

Heat Transfer in a Rotating Two-Pass Rectangular Channel Featuring Reduced Cross-Sectional Area After Tip Turn (Aspect Ratio = 4:1 to 2:1) With Profiled 60 deg Angled Ribs

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Andrew F Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Secondary Flows ◽  
Transfer Coefficients ◽  
First Passage ◽  
Cross Sectional ◽  
Internal Surfaces

The present study features a two-pass rectangular channel with an aspect ratio (AR) = 4:1 in the first pass and an AR = 2:1 in the second pass after a 180-deg tip turn. In addition to the smooth-wall case, ribs with a profiled cross section are placed at 60 deg to the flow direction on both the leading and trailing surfaces in both passages (P/e = 10, e/Dh ∼ 0.11, parallel and in-line). Regionally averaged heat transfer measurement method was used to obtain the heat transfer coefficients on all internal surfaces. The Reynolds number (Re) ranges from 10,000 to 70,000 in the first passage, and the rotational speed ranges from 0 to 400 rpm. Under pressurized condition (570 kPa), the highest rotation number achieved was Ro = 0.39 in the first passage and 0.16 in the second passage. The results showed that the turn-induced secondary flows are reduced in an accelerating flow. The effects of rotation on heat transfer are generally weakened in the ribbed case than the smooth case. Significant heat transfer reduction (∼30%) on the tip wall was seen in both the smooth and ribbed cases under rotating condition. Overall pressure penalty was reduced for the ribbed case under rotation. Reynolds number effect was found noticeable in the current study. The heat transfer and pressure drop characteristics are sensitive to the geometrical design of the channel and should be taken into account in the design process.

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