Mixed Convective Conditions on Natural Convection of MHD Blasius and Sakiadis Flows with Variable Properties and Nonlinear Chemical Reaction

An unsteady two-dimensional boundary layer slip flow of a viscous incompressible fluid moving plate in a quiescent fluid (Sakiadis flow) and the flow-induced over a stationary flat plate by a uniform free stream (Blasius flow) are investigated simultaneously, from a numerical point of view. The variable thermal conductivity, viscosity ratio parameter, and nonlinear chemical reaction are used in the governing equations. Similarity equations of the governing transport equations are converted into an ordinary differential equation. The transformed equations are solved numerically using the Runge-Kutta method via the shooting technique. Sample results for the dimensionless velocity, temperature, and concentration distributions are studied through graphically. Moreover, friction factor, heat, and mass transfer rates have been discussed in detail. The chemical reaction parameter decelerates the friction factor and heat transfer rates for the Sakiadis and Blasius flow cases and enhances in mass transfer rate in both cases. The rate of mass transfer is higher in Blasius flow compared with Sakiadis flow. The present results of the heat transfer rate are compared with the published results are found to be in good agreement.

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Non-similar solutions for mixed convection along a wedge embedded in a porous medium saturated by a non-Newtonian nanofluid

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-07-2012-0169 ◽

2014 ◽

Vol 24 (7) ◽

pp. 1471-1486 ◽

Cited By ~ 31

Author(s):

Ali J. Chamkha ◽

M. Rashad ◽

Rama Subba Reddy Gorla

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Friction Factor ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Surface Heat ◽

Content Type ◽

Transfer Rates ◽

Surface Heat Transfer

Purpose – The purpose of this paper is to present a boundary layer analysis for the mixed convection past a vertical wedge in a porous medium saturated with a power law type non-Newtonian nanofluid. Numerical results for friction factor, surface heat transfer rate and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, Lewis number Le and the power law exponent n. The dependency of the friction factor, surface heat transfer rate (Nusselt number) and mass transfer rate on these parameters has been discussed. Design/methodology/approach – This general non-linear problem cannot be solved in closed form and, therefore, a numerical solution is necessary to describe the physics of the problem. An implicit, tri-diagonal finite-difference method has proven to be adequate and sufficiently accurate for the solution of this kind of problems. Therefore, it is adopted in the present study. Variable step sizes were used. The convergence criterion employed in this study is based on the difference between the current and the previous iterations. When this difference reached 10−5 for all the points in the η directions, the solution was assumed to be converged, and the iteration process was terminated. Findings – The results indicate that as the buoyancy ratio parameter (Nr) and thermophoresis parameter (Nt) increase, the friction factor increases whereas the heat transfer rate (Nusselt number) and mass transfer rate (Sherwood number) decrease. As the Brownian motion parameter (Nb) increases, the friction factor and surface mass transfer rates increase whereas the surface heat transfer rate decreases. As Le increases, mass transfer rates increase. As the power law exponent n increases, the heat and mass transfer rates increase. Research limitations/implications – The analysis is valid for natural convection dominated regime. The combined forced and natural convection dominated regimes will be reported in a future work. Practical implications – The approach used is useful in optimizing the porous media heat transfer problems in geothermal energy recovery, crude oil extraction, ground water pollution, thermal energy storage and flow through filtering media. Originality/value – The results of the study may be of some interest to the researchers of the field of porous media heat transfer. Porous foam and microchannel heat sinks used for electronic cooling are optimized utilizing the porous medium. The utilization of nanofluids for cooling of microchannel heat sinks requires understanding of fundamentals of nanofluid convection in porous media.

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Dual solutions for unsteady flow of Powell-Eyring fluid past an inclined stretching sheet

Journal of Naval Architecture and Marine Engineering ◽

10.3329/jname.v13i1.25338 ◽

2016 ◽

Vol 13 (1) ◽

pp. 89-99 ◽

Cited By ~ 20

Author(s):

P. M. Krishna ◽

N. Sandeep ◽

J. V. R. Reddy ◽

V. Sugunamma

Keyword(s):

Mass Transfer ◽

Unsteady Flow ◽

Friction Factor ◽

Heat And Mass Transfer ◽

Chemical Reaction ◽

Transfer Rate ◽

Stretching Sheet ◽

Mass Transfer Rate ◽

Dual Solutions ◽

Source Sink

This paper deals with the heat and mass transfer in unsteady flow of Powell-Eyring fluid past an inclined stretching sheet in the presence of radiation, non-uniform heat source/sink and chemical reaction with suction/injection effects. The governing equations are reduced into system of ordinary differential equations using similarity transformation and solved numerically using Runge-Kutta based shooting technique. Results display the influence of governing parameters on the flow, heat and mass transfer, friction factor, local Nusselt and Sherwood numbers. Comparisons are made with the existed studies. Present results have an excellent agreement with the existed studies. Results indicate that an increase in the chemical reaction parameter depreciates the friction factor, heat transfer rate and enhances the mass transfer rate. Dual solutions exist only for certain range of suction/injection parameters.

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Natural Convective Boundary-Layer Flow Over a Vertical Cylinder Embedded in a Porous Medium Saturated With a Nanofluid

Journal of Nanotechnology in Engineering and Medicine ◽

10.1115/1.4007886 ◽

2012 ◽

Vol 3 (3) ◽

Cited By ~ 6

Author(s):

Rama Subba Reddy Gorla ◽

Waqar Khan

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Mass Transfer ◽

Porous Medium ◽

Friction Factor ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Vertical Cylinder ◽

Surface Heat

In this paper, a boundary layer analysis is presented for the natural convection past a vertical cylinder in a porous medium saturated with a nanofluid. Numerical results for friction factor, surface heat transfer rate, and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, and Lewis number Le. The dependency of the friction factor, surface heat transfer rate (Nusselt number), and mass transfer rate on these parameters has been discussed. The results indicate that as Nr, Nb, and Nt increase, the friction factor and heat transfer rate (Nusselt number) decrease. The mass transfer rate (Sherwood number) increases with Le, Nb, and Nt.

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Local Mass and Heat Transfer on a Turbine Blade Tip

International Journal of Rotating Machinery ◽

10.1155/s1023621x03000083 ◽

2003 ◽

Vol 9 (2) ◽

pp. 81-95 ◽

Cited By ~ 10

Author(s):

P. Jin ◽

R. J. Goldstein

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Turbine Blade ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Tip Clearance ◽

Transfer Rates ◽

Average Mass ◽

Blade Tip ◽

Mass And Heat Transfer

Local mass and heat transfer measurements on a simulated high-pressure turbine blade-tip surface are conducted in a linear cascade with a nonmoving tip endwall, using a naphthalene sublimation technique. The effects of tip clearance (0.86–6.90% of chord) are investigated at various exit Reynolds numbers (4–7 ×105) and turbulence intensities (0.2 and 12.0%).The mass transfer on the tip surface is significant along its pressure edge at the smallest tip clearance. At the two largest tip clearances, the separation bubble on the tip surface can cover the whole width of the tip on the second half of the tip surface. The average mass-transfer rate is highest at a tip clearance of 1.72% of chord. The average mass-transfer rate on the tip surface is four and six times as high as on the suction and the pressure surface, respectively. A high mainstream turbulence level of 12.0% reduces average mass-transfer rates on the tip surface, while the higher mainstream Reynolds number generates higher local and average mass-transfer rates on the tip surface.

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Minimum Orbital Period of Cataclysmic Variables

International Astronomical Union Colloquium ◽

10.1017/s0252921100076545 ◽

1979 ◽

Vol 53 ◽

pp. 504-504

Author(s):

B. Paczynski ◽

W. Krzeminski

Keyword(s):

Mass Transfer ◽

Angular Momentum ◽

Orbital Period ◽

Time Scale ◽

Transfer Rate ◽

Main Sequence ◽

Mass Transfer Rate ◽

Cataclysmic Variables ◽

Transfer Rates ◽

Angular Momentum Loss

The shortest known orbital period of a cataclysmic binary with a hydrogen dwarf secondary filling its Roche lobe is about 80 minutes. Theoretically the shortest possible orbital period for such a system is less than 60 minutes. We tried to explain why the periods shorter than 80 minutes are not observed. We estimated the time scale of angular momentum loss of a cataclysmic binary and the resulting mass transfer rate. The minimum orbital period for a given Ṁ is obtained during the transition of the secondary from the Main Sequence onto the Degenerate Dwarf Sequence. Pmin ∝ Ṁ½ Therefore, only those systems can reach low P for which Ṁ is small. This explains why among the shortest period cataclysmic variables there are no novae: presumably their mass transfer rates are too large. It also indicates that “polars” (AM Her-type stars) and SU UMa-type stars should have low Ṁ.

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SWSex Stars, Old Novae, and the Evolution of Cataclysmic Variables

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2015.02.0188 ◽

2015 ◽

Vol 2 (1) ◽

pp. 188-191 ◽

Cited By ~ 2

Author(s):

L. Schmidtobreick ◽

C. Tappert

Keyword(s):

Mass Transfer ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Cataclysmic Variables ◽

High Mass ◽

Period Range ◽

Transfer Rates ◽

Low Mass ◽

Orbital Periods ◽

Nova Outburst

The population of cataclysmic variables with orbital periods right above the period gap are dominated by systems with extremely high mass transfer rates, the so-called SW Sextantis stars. On the other hand, some old novae in this period range which are expected to show high mass transfer rate instead show photometric and/or spectroscopic resemblance to low mass transfer systems like dwarf novae. We discuss them as candidates for so-called hibernating systems, CVs that changed their mass transfer behaviour due to a previously experienced nova outburst. This paper is designed to provide input for further research and discussion as the results as such are still very preliminary.

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THE EFFECT OF DIFFERENT AMBIENT TEMPERATURE TO SOLAR COOLING PERFORMANCE

Jurnal Teknologi ◽

10.11113/jt.v78.8575 ◽

2016 ◽

Vol 78 (5-5) ◽

Cited By ~ 1

Author(s):

Dewanto Harjunowibowo ◽

Dina Nur Adilah ◽

Dwi Teguh Rahardjo ◽

Danar S. Wijayanto ◽

Fredy Surahmanto ◽

...

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Ambient Temperature ◽

Heat And Mass Transfer ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Adsorption Process ◽

Mass Transfer Rate ◽

Cooling Performance ◽

Solar Cooling

The density of adsorbent bed significantly contributed to solar cooling performance (COP). The density determines how well the heat and mass transfer are. Besides that, the COP is also determined by ambient temperature. This research aims to investigate the affect of temperature of a connecting pipe, as a representative of different ambient temperature against a solar cooling machine performance. The experiment will show in what condition a solar cooling is going to have a better cooling result. The data used in this case was taken experimentally and conducted using a solar cooling machine equipped with temperature measurement units such as thermocouple logger. For cold ambient temperature, in adsorption process, refrigerant vapour flows to the generator through the connecting pipe cooled by water and kept steady. The results show that the COP, heat and mass transfer of adsorbent bed of the system in the adsorption process on a warm condition are better than in a cold environment. In the warm condition the COP system is 0.24, the heat transfer rate is 0.06 °C/minute, and the mass transfer rate is 1.09 ml/minute. Whereas, in the cold condition the COP system is 0.23, the heat transfer rate is 0.05 °C/minute, and the mass transfer rate is 1.04 ml/minute.

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Large-scale energetic coherent structures and their effects on wall mass transfer rate behind orifice in round pipe

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.761 ◽

2021 ◽

Vol 927 ◽

Author(s):

F. Shan ◽

S.Y. Qin ◽

Y. Xiao ◽

A. Watanabe ◽

M. Kano ◽

...

Keyword(s):

Mass Transfer ◽

Flow Field ◽

Coherent Structures ◽

Transfer Rate ◽

Large Scale ◽

Mass Transfer Rate ◽

Low Frequency ◽

Stochastic Estimation ◽

Transfer Rates ◽

Wall Mass

This paper first uses a low-speed stereoscopic particle image velocimetry (SPIV) system to measure the convergent statistical quantities of the flow field and then simultaneously measure the time-resolved flow field and the wall mass transfer rate by a high-speed SPIV system and an electrochemical system, respectively. We measure the flow field and wall mass transfer rate under upstream pipe Reynolds numbers between 25 000 and 55 000 at three specific locations behind the orifice plate. Moreover, we apply proper orthogonal decomposition (POD), stochastic estimation and spectral analysis to study the properties of the flow field and the wall mass transfer rate. More importantly, we investigate the large-scale coherent structures’ effects on the wall mass transfer rate. The collapse of the wall mass transfer rates’ spectra by the corresponding time scales at the three specific positions of orifice flow suggest that the physics of low-frequency wall mass transfer rates are probably the same, although the flow fields away from the wall are quite different. Furthermore, the spectra of the velocity reconstructed by the most energetic eigenmodes agree well with the wall mass transfer rate in the low-frequency region, suggesting that the first several energetic eigenmodes capture the flow dynamics relevant to the low-frequency variation of the wall mass transfer. Stochastic estimation results of the velocity field associated with large wall mass transfer rate at all three specific locations further reveal that the most energetic coherent structures are correlated with the wall mass transfer rate.

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Flow and Mass Transfer Performance in Short Pin-Fin Channels with Different Fin Shapes

International Journal of Rotating Machinery ◽

10.1155/s1023621x98000104 ◽

1998 ◽

Vol 4 (2) ◽

pp. 113-128 ◽

Cited By ~ 6

Author(s):

R. J. Goldstein ◽

S. B. Chen

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Reynolds Number ◽

Flow Velocity ◽

Pressure Loss ◽

Transfer Rate ◽

Mass Transfer Rate ◽

Flow Characteristics ◽

Pin Fin ◽

Pin Fin Arrays

The mass transfer (analogous to heat transfer) and pressure loss characteristics of staggered short pin-fin arrays are investigated experimentally in the range of Reynolds number 3000 to 18,000 based on fin diameter and mean approach-flow velocity. Three different shapes of fins with aspect ratio of 2 are examined: one uniform-diameter circular fin (UDCF) and two stepped-diameter circular fins (SDCF1 and SDCF2). Flow visualization using oil-lampblack reveals complex flow characteristics associated with the repeated production of horseshoe vortices and fin wakes, and the interactions among these. The SDCF1 and SDCF2 arrays show flow characteristics different from the UDCF array due to downflow from the steps. For all arrays tested, the near-endwall flow varies row by row in the initial rows until it reaches a stable pattern after the third row. The row-averaged Sherwood numbers obtained from the naphthalene sublimation experiment also show a row-by-row variation pattern similar to the flow results. While the SDCF2 array has the highest mass transfer rate, the SDCF1 array has the smallest pressure loss at the same approach-flow velocity. The fin surfaces have higher array-averaged Sherwood number than the endwall and the ratio between these changes with fin shape and Reynolds number. The performance of the pin-fin arrays is analyzed under two different constraints: the mass[heat transfer rate at fixed pumping power, and the mass/heat transfer area and pressure loss to fulfill fixed heat load at a fixed mass flow rate. In both cases, the SDCF2 array shows the best performance.

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