Flow Characteristics and Local Heat Transfer Rates for a Heated Circular Cylinder in a Crossflow of Air

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.

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Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct

Journal of Heat Transfer ◽

10.1115/1.3614343 ◽

1967 ◽

Vol 89 (2) ◽

pp. 163-167 ◽

Cited By ~ 27

Author(s):

E. G. Filetti ◽

W. M. Kays

Keyword(s):

Heat Transfer ◽

Local Heat Transfer ◽

Reynolds Numbers ◽

Local Heat ◽

Duct Flow ◽

Double Step ◽

Maximum Heat ◽

Transfer Rates ◽

Maximum Heat Transfer ◽

Flow Cross

Experimental data are presented for local heat transfer rates near the entrance to a flat duct in which there is an abrupt symmetrical enlargement in flow cross section. Two enlargement area ratios are considered, and Reynolds numbers, based on duct hydraulic diameter, varied from 70,000 to 205,000. It is found that such a flow is characterized by a long stall on one side and a short stall on the other. Maximum heat transfer occurs in both cases at the point of reattachment, followed by a decay toward the values for fully developed duct flow. Empirical equations are given for the Nusselt number at the reattachment point, correlated as functions of duct Reynolds number and enlargement ratio.

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Three-Dimensional Natural Convection From Vertical Heated Plates With Adjoining Cool Surfaces

Journal of Heat Transfer ◽

10.1115/1.2911235 ◽

1992 ◽

Vol 114 (1) ◽

pp. 115-120 ◽

Cited By ~ 6

Author(s):

B. W. Webb ◽

T. L. Bergman

Keyword(s):

Heat Transfer ◽

Natural Convection ◽

Control Volume ◽

Three Dimensional ◽

Local Heat Transfer ◽

Local Heat ◽

Uniform Heat Flux ◽

Infrared Thermal Imaging ◽

Transfer Rates ◽

Thermal Boundary Conditions

Natural convection in an enclosure with a uniform heat flux on two vertical surfaces and constant temperature at the adjoining walls has been investigated both experimentally and theoretically. The thermal boundary conditions and enclosure geometry render the buoyancy-induced flow and heat transfer inherently three dimensional. The experimental measurements include temperature distributions of the isoflux walls obtained using an infrared thermal imaging technique, while the three-dimensional equations governing conservation of mass, momentum, and energy were solved using a control volume-based finite difference scheme. Measurements and predictions are in good agreement and the model predictions reveal strongly three-dimensional flow in the enclosure, as well as high local heat transfer rates at the edges of the isoflux wall. Predicted average heat transfer rates were correlated over a range of the relevant dimensionless parameters.

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Numerical heat transfer analysis of micro-scale jet-impingement cooling in a high-pressure turbine vane

10.32920/ryerson.14651841.v1 ◽

2021 ◽

Author(s):

Karan Anand

Keyword(s):

Heat Transfer ◽

Three Dimensional ◽

Jet Impingement ◽

Local Heat Transfer ◽

Local Heat ◽

Heat Transfer Analysis ◽

Transfer Rates ◽

Numerical Heat Transfer ◽

Turbine Vane ◽

Single Jet

This research provides a computational analysis of heat transfer due to micro jet-impingement inside a gas turbine vane. A preliminary-parametric analysis of axisymmetric single jet was reported to better understand micro jet-impingement. In general, it was seen that as the Reynolds number increased the Nusselt number values increased. The jet to target spacing had a considerably lower impact on the heat transfer rates. Around 30% improvement was seen by reducing the diameter to half while changing the shape to an ellipse saw 20.8% improvement in Nusselt value. The numerical investigation was then followed by studying the heat transfer characteristics in a three-dimensional, actual-shaped turbine vane. Effects of jet inclination showed enhanced mixing and secondary heat transfer peaks. The effect of reducing the diameter of the jets to 0.125 mm yielded 55% heat transfer improvements compared to 0.51 mm; the tapering effect also enhanced the local heat transfer values as local velocities at jet exit increased.

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Local Heat Transfer and Flow Characteristics in Two-Pass Channels with an Inclined Divider Wall.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.68.1523 ◽

2002 ◽

Vol 68 (669) ◽

pp. 1523-1530

Author(s):

Masafumi HIROTA ◽

Hiroshi NAKAYAMA ◽

Lei CAI ◽

Hideomi FUJITA ◽

Tatsuhito KATOH ◽

...

Keyword(s):

Heat Transfer ◽

Flow Characteristics ◽

Local Heat Transfer ◽

Local Heat

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Local heat transfer of a circular cylinder in transverse motion in a fluidized bed

Journal of Engineering Physics ◽

10.1007/bf00829100 ◽

1967 ◽

Vol 12 (2) ◽

pp. 91-94

Author(s):

B. V. Berg ◽

A. P. Baskakov

Keyword(s):

Heat Transfer ◽

Circular Cylinder ◽

Fluidized Bed ◽

Local Heat Transfer ◽

Local Heat ◽

Transverse Motion

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Numerical Prediction of Flow and Heat Transfer Past a Circular Tube With Annular Fins

Heat Transfer, Volume 1 ◽

10.1115/imece2003-42872 ◽

2003 ◽

Author(s):

D. Chakraborty ◽

G. Biswas ◽

P. K. Panigrahi

Keyword(s):

Heat Transfer ◽

Circular Tube ◽

Flow Characteristics ◽

Cross Flow ◽

Local Heat Transfer ◽

Local Heat ◽

Stagnation Line ◽

Flow And Heat Transfer ◽

Annular Fin ◽

Annular Fins

A numerical investigation was carried out to study the flow and heat transfer behavior of a vertical circular tube, which is situated between two annular fins in cross-flow. The flow structure of the limiting streamlines on the surface of the circular tube and the annular fins was analysed. A finite volume method was employed to solve the Navier-Stokes and energy equations. The numerical results pertaining to heat transfer and flow characteristics were compared with the available experimental results. The following salient features were observed in this configuration. A horseshoe vortex system was formed at the junction of the stagnation line of the circular tube and the annular fin. The separation took place at the rear of the tube. The influence of the horseshoe vortices on local heat transfer was substantial. The ratio of the axial gap between two annular fins (L) to the radial protrusion length of the annular fin (LR) was identified as an important parameter. The flow and heat transfer results were presented for different L/LR ratios for a Reynolds number of 1000.

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