Numerical Study of Droplet Evaporation in a High-Temperature Stream

1983 ◽  
Vol 105 (2) ◽  
pp. 389-397 ◽  
Author(s):  
M. Renksizbulut ◽  
M. C. Yuen
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Number Range ◽  
Transfer Rates ◽  
Pressure Drag ◽  
Continuity Equations ◽  
Stream Density ◽  
Solid Spheres

Numerical solutions for high-temperature air flowing past water and methanol droplets and solid spheres, and superheated steam flowing past water droplets were obtained in the Reynolds number range of 10 to 100. The coupled momentum, energy, and specie continuity equations of variable thermophysical properties were solved using finite difference techniques. The numerical results of heat transfer and total drag agree well with existing experimental data. Mass transfer decreases friction drag significantly but at the same time increases pressure drag by almost an equal amount. The net effect is that the standard drag curve for solid spheres can be used for evaporating droplets provided the density is the free stream density and the viscosity of the vapor mixture is evaluated at an appropriate reference temperature and concentration. Both the mass efflux and variable properties decrease heat transfer rates to the droplets.

Experimental Study of Droplet Evaporation in a High-Temperature Air Stream

1983 ◽  
Vol 105 (2) ◽  
pp. 384-388 ◽  
Author(s):  
M. Renksizbulut ◽  
M. C. Yuen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Liquid Droplets ◽  
Transfer Number ◽  
Number Range ◽  
Transfer Rates ◽  
Hot Air ◽  
Air Stream ◽  
Stream Density ◽  
Freely Suspended

Heat transfer rates to simulated and freely suspended liquid droplets were measured in an atmospheric hot air tunnel. The experiments were limited to water, methanol, and heptane droplets in a Reynolds number range of 25 to 2000, and a mass transfer number range of 0.07 to 2.79. The present experimental data together with data by others can best be correlated by Nuf(1+Bf).7 = 2 + 0.57 ReM1/2 Prf1/3, where properties are evaluated at film conditions except for the density in the Reynolds number which is the free-stream density. Thus the data shows that at higher temperatures, evaporation reduces heat transfer rates directly by a factor of (1 + Bf).7. Indirectly, evaporation affects heat transfer rates through the changes in both the composition and temperature of the surrounding gaseous medium.

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

2021 ◽  
pp. 095440622110272
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Litan Kumar Saha ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

A Numerical and Experimental Investigation of Turbulent Heat Transport Downstream From an Abrupt Pipe Expansion

1983 ◽  
Vol 105 (4) ◽  
pp. 862-869 ◽  
Author(s):  
R. S. Amano ◽  
M. K. Jensen ◽  
P. Goel
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Expansion

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105. The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

Computational Fluid Dynamics Evaluation of Heat Transfer Correlations for Sodium Flows in a Heat Exchanger

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Seok-Ki Choi ◽  
Seong-O Kim ◽  
Hoon-Ki Choi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulence Model ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Cross Flow ◽  
Turbulence Models ◽  
Parallel Flow ◽  
Sst Model ◽  
Heat Transfer Correlations

A numerical study for the evaluation of heat transfer correlations for sodium flows in a heat exchanger of a fast breeder nuclear reactor is performed. Three different types of flows such as parallel flow, cross flow, and two inclined flows are considered. Calculations are performed for these three typical flows in a heat exchanger changing turbulence models. The tested turbulence models are the shear stress transport (SST) model and the SSG-Reynolds stress turbulence model by Speziale, Sarkar, and Gaski (1991, “Modelling the Pressure-Strain Correlation of Turbulence: An Invariant Dynamical System Approach,” J. Fluid Mech., 227, pp. 245–272). The computational model for parallel flow is a flow past tubes inside a circular cylinder and those for the cross flow and inclined flows are flows past the perpendicular and inclined tube banks enclosed by a rectangular duct. The computational results show that the SST model produces the most reliable results that can distinguish the best heat transfer correlation from other correlations for the three different flows. It was also shown that the SSG-RSTM high-Reynolds number turbulence model does not deal with the low-Prandtl number effect properly when the Peclet number is small. According to the present calculations for a parallel flow, all the old correlations do not match with the present numerical solutions and a new correlation is proposed. The correlations by Dwyer (1966, “Recent Developments in Liquid-Metal Heat Transfer,” At. Energy Rev., 4, pp. 3–92) for a cross flow and its modified correlation that takes into account of flow inclination for inclined flows work best and are accurate enough to be used for the design of the heat exchanger.

scholarly journals A numerical study of free convective heat transfer in a double-glazed window with a between-pane Venetian blind

2021 ◽  
Author(s):  
Tony Avedissian
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Numerical Study ◽  
Thermal Conductivity Ratio ◽  
Number Range ◽  
Free Convective Heat Transfer ◽  
Venetian Blind

The free convective heat transfer in a double-glazed window with a between-pane Venetian blind has been studied numerically. The model geometry consists of a two-dimensional vertical cavity with a set of internal slats, centred between the glazings. Approximately 700 computational fluid dynamic solutions were conducted, including a grid sensitivity study. A wide set of geometrical and thermo-physical conditions was considered. Blind width to cavity width ratios of 0.5, 0.65, 0.8, and 0.9 were studied, along with three slat angles, 0º (fully open, +/- 45º (partially open), and 75º (closed). The blind to fluid thermal conductivity ratio was set to 15 and 4600. Cavity aspects of 20, 40, and 60, were examined over a Rayleigh number range of 10 to 10⁵, with the Prandtl number equal to 0.71. The resulting convective heat transfer data are presented in terms of average Nusselt numbers. Depending on the specific window/blind geometry, the solutions indicate that the blind can either reduce or enhance the convective heat transfer rate across the glazings. The present study does not consider radiation effects in the numerical solution. Therefore, a post-processing algorithm is presented that incorporates the convective and radiative influences, in order to determine the overall heat transfer rate across the window/blind system.

scholarly journals Cumulative Impact of Micropolar Fluid and Porosity on MHD Channel Flow: A Numerical Study

Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 93
Author(s):  
Kottakkaran Sooppy Nisar ◽  
Aftab Ahmed Faridi ◽  
Sohail Ahmad ◽  
Nargis Khan ◽  
Kashif Ali ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Chemical Reaction ◽  
Micropolar Fluid ◽  
Numerical Study ◽  
Nonlinear Differential Equations ◽  
X Rays ◽  
Cumulative Impact ◽  
Transfer Rates ◽  
Mass And Heat Transfer ◽  
The Impact

The mass and heat transfer magnetohydrodynamic (MHD) flows have a substantial use in heat exchangers, electromagnetic casting, X-rays, the cooling of nuclear reactors, mass transportation, magnetic drug treatment, energy systems, fiber coating, etc. The present work numerically explores the mass and heat transportation flow of MHD micropolar fluid with the consideration of a chemical reaction. The flow is taken between the walls of a permeable channel. The quasi-linearization technique is utilized to solve the complex dynamical coupled and nonlinear differential equations. The consequences of the preeminent parameters are portrayed via graphs and tables. A tabular and graphical comparison evidently reveals a correlation of our results with the existing ones. A strong deceleration is found in the concentration due to the effect of a chemical reaction. Furthermore, the impact of the magnetic field force is to devaluate the mass and heat transfer rates not only at the lower but at the upper channel walls, likewise.

Study of Flow and Convective Heat Transfer in a Simulated Scaled Up Low Emission Annular Combustor

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Sunil Patil ◽  
Teddy Sedalor ◽  
Danesh Tafti ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Number ◽  
Maximum Heat ◽  
Number Range ◽  
Maximum Heat Transfer ◽  
Annular Combustor

Modern dry low emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental–numerical study of swirling flow inside a DLE annular combustor model is used to determine the distribution of heat transfer on the liner walls. Three different Reynolds numbers are investigated in the range of 210,000–840,000 with a characteristic swirl number of 0.98. The maximum heat transfer coefficient enhancement ratio decreased from 6 to 3.6 as the flow Reynolds number increased from 210,000 to 840,000. This is attributed to a reduction in the normalized turbulent kinetic energy in the impinging shear layer, which is strongly dependent on the swirl number that remains constant at 0.98 for the Reynolds number range investigated. The location of peak heat transfer did not change with the increase in Reynolds number since the flow structures in the combustors did not change with Reynolds number. Results also showed that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. A modified swirl number accounting for the step expansion ratio is defined to facilitate comparison between the heat transfer characteristics in the annular combustor with previous work in a can combustor. A higher modified swirl number in the annular combustor resulted in higher heat transfer augmentation and a slower decay with Reynolds number.

FREE CONVECTION FROM A WINDOW GLAZING WITH A VENETIAN BLIND: NUMERICAL MODEL DEVELOPMENT

1999 ◽  
Vol 23 (1B) ◽  
pp. 159-172 ◽  
Author(s):  
J. Phillips ◽  
D. Naylor ◽  
S.J. Harrison ◽  
P.H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Radiation Heat Transfer ◽  
Model Development ◽  
Plate Spacing ◽  
Venetian Blinds ◽  
The Difference ◽  
Visualization Experiments ◽  
Conjugate Conduction

The present numerical study examines the influence of horizontal louvres (Venetian blinds) on the convective heat transfer from a vertical isothermal surface. A steady, laminar, two dimensional, conjugate conduction/convection solution to this problem has been obtained using the finite element method. Detailed comparisons are made with temperature field and local Nusselt number data obtained using a Mach-Zehnder Interferometer. Also, numerically predicted stream function contours are compared to streamlines obtained from flow visualization experiments. All results are obtained for Pr = 0.7, as the intended application of this study is for air. Results show that as the blind tip-to-plate spacing decreases, the difference between numerical solutions and experimental results increase. This suggests that radiation heat transfer may be a significant factor at smaller blind spacings.

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