Premixed edge-flame oscillations in a rectangular channel with side-wall mass injection

2002 ◽  
Vol 6 (4) ◽  
pp. 607-623 ◽  
Author(s):  
Yanning Liu ◽  
Mark Short
Keyword(s):  
Rectangular Channel ◽  
Side Wall ◽  
Mass Injection ◽  
Wall Mass

Buoyancy Effects in the Entrance Region of an Inclined Multirectangular-Channel Solar Collector

1983 ◽  
Vol 105 (2) ◽  
pp. 157-162 ◽  
Author(s):  
S. M. Morcos ◽  
M. M. M. Abou-Ellail
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Solar Collector ◽  
Flux Distribution ◽  
Rectangular Channel ◽  
Numerical Procedure ◽  
Side Wall ◽  
Entrance Region ◽  
Heat Flux Distribution ◽  
Constant Property

A numerical procedure is presented for the entrance region of an inclined multirectangular-channel solar collector with significant buoyancy effects. The upper wall heat flux is taken to be uniform, while the lower wall is assumed to be insulated. The heat flux distribution on the side wall of the rectangular channel is obtained by coupling a heat-conduction numerical procedure in the metallic region surrounding the channel to the main numerical procedure which solves the hydrodynamic and energy equations of the flow inside the channel. Numerical results are presented for water flowing in a multirectangular-channel solar collector with an aspect ratio AR = 4 inclined at an angle α = 30 deg to the horizontal. The resulting variable heat flux distribution on the side wall enhances the intensity of the secondary flow. The effects of the nonuniform heat flux distribution and the spacing between the rectangular channels on the variation of Nusselt number in the entrance region are presented for different values of Rayleigh number. At a value of Ra = 5 × 105, Nusselt number is more than 300 percent above the constant property prediction.

DNS of Expansion Ratio Effects on Three-Dimensional Unsteady Separated Flow and Heat Transfer Around a Downward Step

2005 ◽  
Author(s):  
Aya Kito ◽  
Kazuaki Sugawara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Side Wall ◽  
Separated Flow ◽  
Flow Region ◽  
Expansion Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Channel Expansion

The direct numerical simulation methodology was employed to analyze the unsteady features of a three-dimensional separated flow and heat transfer around a downward step in a rectangular channel, and to clarify systematically the channel expansion ratio effects upon them. Numerical calculations were carried out using the finite difference method. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The channel expansion ratio ER is 1.5, 2.0 and 3.0 under a step aspect ratio of 36.0. It is found that the flow is steady upto Re = 500 but becomes sensibly unsteady at Re = 700 for all the three expansion ratios. In the case of ER = 2.0, the separated shear layer is most unstable. In the case of ER = 1.5, the longitudinal vortices formed near the side walls of channel are strongest. Nusselt number reaches its maximum in the reattachment flow region and also in the neighborhood of the side wall, and their locations depend greatly upon ER and Re.

Heat Transfer in a Two-Inlet Rotating Pin-Fin Roughened Rectangular Channel With Side-Wall Fluid Extraction

2018 ◽  
Author(s):  
Yanan Chen ◽  
Jie Wen ◽  
Guoqiang Xu ◽  
Zhiliang Du ◽  
Yunqing Dai
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rectangular Channel ◽  
Side Wall ◽  
Flow Rate Ratio ◽  
Cooling Channel ◽  
Inlet Channel ◽  
Pin Fin

The heat transfer characteristics in a rotating pin-fin roughened rectangular channel with an aspect ratio of 4:1 is investigated, simulating a rotor blade trailing edge. The copper plate regional average method is used to determine the heat transfer coefficient. A second inlet is added at the inner top corner of the traditional one-inlet cooling channel to improve heat transfer in the high radius region. Coolant from these two inlets mixes in the middle of the channel, and then exits through eight sidewall slots. The channel is assembled in a rotating facility, and the symmetrical plane of the rectangular channel is orientated at an angle of 135° with respect to the rotation plane. The mass flow rate of the bottom inlet is kept at a constant (Re1 = 20,000), whereas the inlet mass flow rate ratio (MR, second inlet mass flow rate/bottom inlet mass flow rate) changes from 0 to around 0.55. Results show that the second inlet improves the heat transfer in the proximity of the second inlet extensively, but the overall averaged heat transfer is decreased a bit compared to the one inlet channel. Moreover, with the local MR, the heat transfer data at different locations converge into the same trend, indicating that the local MR should be a good parameter in describing the flow in this pin-fin cooling channel. In the rotating one-inlet channel (MR = 0), a critical Ro phenomenon is observed. After the critical point, rotation stops decreasing heat transfer and starts to elevate it. A lower critical Ro is observed at higher radius location but the corresponding local Ro is a constant at around 1.0. In rotating two-inlet channel, the overall heat transfer enhancement caused by rotation is almost in the same level with different MR, indicating that high MR cases (MR > 0.2) is not recommended because the coolant from the second inlet is not efficiently used.

Assessment of CHF Enhancement Mechanisms in a Curved, Rectangular Channel Subjected to Concave Heating

1999 ◽  
Vol 121 (2) ◽  
pp. 394-404 ◽  
Author(s):  
J. C. Sturgis ◽  
I. Mudawar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Cross Sections ◽  
Rectangular Channel ◽  
Side Wall ◽  
Gravitational Acceleration ◽  
Centripetal Acceleration ◽  
Concave Wall ◽  
Buoyancy Forces ◽  
Flow Curvature

An experimental study was undertaken to examine the enhancement in critical heat flux (CHF) provided by streamwise curvature. Curved and straight rectangular flow channels were fabricated with identical 5.0 × 2.5 mm cross sections and heated lengths of 101.6 mm in which the heat was applied to only one wall—the concave wall (32.3 mm radius) in the curved channel and a side wall in the straight. Tests were conducted using FC-72 liquid with mean inlet velocity and outlet subcooling of 0.25 to 10 m s−1 and 3 to 29°C, respectively. Centripetal acceleration for curved flow reached 315 times earth’s gravitational acceleration. Critical heat flux was enhanced due to flow curvature at all conditions but the enhancement decreased with increasing subcooling. For near-saturated conditions, the enhancement was approximately 60 percent while for highly subcooled flow it was only 20 percent. The causes for the enhancement were identified as (1) increased pressure on the liquid-vapor interface at wetting fronts, (2) buoyancy forces and (3) increased subcooling at the concave wall. Flow visualization tests were conducted in transparent channels to explore the role of buoyancy forces in enhancing the critical heat flux. These forces were observed to remove vapor from the concave wall and distribute it throughout the cross section. Vapor removal was only effective at near-saturated conditions, yielding the observed substantial enhancement in CHF relative to the straight channel.

scholarly journals CO2-Driven diffusiophoresis and water cleaning: similarity solutions for predicting the exclusion zone in a channel flow

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Suin Shim ◽  
Mrudhula Baskaran ◽  
Ethan H. Thai ◽  
Howard A. Stone
Keyword(s):  
Shear Rate ◽  
Flow Structure ◽  
Channel Flow ◽  
Rectangular Channel ◽  
Side Wall ◽  
Similarity Solutions ◽  
Wall Shear Rate ◽  
Exclusion Zone ◽  
Similarity Transform ◽  
Water Cleaning

We study diffusiophoretic exclusion zone (EZ) formation in rectangular channel flow, driven by CO2 dissolution from one side wall. By using a similarity transform and considering the flow structure, we obtain the relation between EZ and the wall shear rate.

scholarly journals Method of determining the optimal coordinate domain in the measurement of water flows turbulence using lad-56 in rectangular channels

Vestnik MGSU ◽  
2016 ◽  
pp. 106-115
Author(s):  
Georgiy Valentinovich Volgin ◽  
Dmitriy Viktorovich Kulikov
Keyword(s):  
Experimental Data ◽  
Laser Doppler Anemometry ◽  
Rectangular Channel ◽  
Side Wall ◽  
Measuring System ◽  
Testing Time ◽  
Water Flows ◽  
Rectangular Channels ◽  
Turbulent Characteristics ◽  
Spatial Coordinates

One of the modern methods of the experimental investigation of water flows turbulence is the method of Laser Doppler Anemometry. At the present time a measuring system “LAD-056” (Russia) is operating in the laboratory of the Department of Hydraulics of MGSU. The authors conducted an analysis of the requirements to experimental data when calculating turbulent characteristics of water flows. The article shows the necessity of checking the database of ripple continuity over time and the required representation of the number of points in the implementation. The results of experiments are presented showing the importance of fixing the length of the implementation and testing time. The authors offered a method of determining the optimal spatial coordinates for the measurement to minimize the time of filling the base of experimental data. According to the methods of defining optimal coordinate domain when measuring turbulent water flows with the use of “LAD-056” in a rectangular channel with glass walls in was established that it is required to conduct measurements within the range from 0 to 120 mm from the closest side wall. In case of greater deepening it is required to use illuminators reducing deflections of laser beams.

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