Effect of corrugation frequencies on natural convective heat transfer and flow characteristics in a square enclosure of vee-corrugated vertical walls

1993 ◽  
Vol 17 (8) ◽  
pp. 697-708 ◽  
Author(s):  
Mohammad Ali ◽  
S. R. Husain
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Characteristics ◽  
Square Enclosure ◽  
Vertical Walls

Numerical Study of Convective Heat Transfer of Multiple Internal Isolated Blocks in an Enclosure

Solar Energy ◽  
2005 ◽  
Author(s):  
Xutao Zhang ◽  
Jianing Zhao ◽  
Fusheng Gao ◽  
Jun Gao ◽  
Songling Wang
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Convective Heat Transfer ◽  
Forced Convection ◽  
Convective Heat ◽  
Numerical Study ◽  
Thermal Design ◽  
Square Enclosure ◽  
Forced Convective Heat Transfer ◽  
Low Reynolds

The treatment of Convective Heat Transfer Coefficients (CHTCs) in an enclosure has a significant impact on the thermal design of electronic appliance, especially the CHTCs in an enclosure with internal isolated blocks. The CHTCs of the isolated blocks for pure natural convection are usually used, while it may not be applicable to any practice. Combined convective heat transfer, even forced convective heat transfer, is sometime more applicable in reality. In our present work, first of all, validation of the turbulence model for CFD simulation of natural convective flows in a square enclosure is performed. The values of CHTCs for vertical walls obtained by using a low Reynolds k-ε model agree well with the existed correlations. The simulation also indicates that the distance from the first grid to the wall has a significant impact on the CHTCs. Using this low Reynolds k-ε model, computer simulations of natural and forced convective heat transfer within a square enclosure containing ten isolated blocks are performed. For both the natural and forced convection, the dimensionless Nusselt numbers are derived by the obtained results. For the case of mixed convection, the CHTCs are established by blending those for natural and forced convection using the Churchill-Usagi approach, which is a general expression combines the asymptotic solutions of independent CHTCs into the mixed convection by using a Churchill-Usagi blending coefficient.

Numerical Study of Turbulent Flow and Convective Heat Transfer Characteristics in Helical Rectangular Ducts

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Yunfei Xing ◽  
Fengquan Zhong ◽  
Xinyu Zhang
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Direction ◽  
Outer Wall ◽  
Centrifugal Effect

Three-dimensional turbulent forced convective heat transfer and its flow characteristics in helical rectangular ducts are simulated using SST k–ω turbulence model. The velocity field and temperature field at different axial locations along the axial direction are analyzed for different inlet Reynolds numbers, different curvatures, and torsions. The causes of heat transfer differences between the inner and outer wall of the helical rectangular ducts are discussed as well as the differences between helical and straight duct. A secondary flow is generated due to the centrifugal effect between the inner and outer walls. For the present study, the flow and thermal field become periodic after the first turn. It is found that Reynolds number can enhance the overall heat transfer. Instead, torsion and curvature change the overall heat transfer slightly. But the aspect ratio of the rectangular cross section can significantly affect heat transfer coefficient.

scholarly journals The Natural Convective Heat Transfer in a Partially Divided Enclosure: A Study on the Influence of the Source Position

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Francesco Corvaro ◽  
Massimo Paroncini
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Dynamic Behaviour ◽  
Velocity Fields ◽  
Source Position ◽  
Square Enclosure ◽  
Nusselt Numbers ◽  
First Case ◽  
Rayleigh Numbers

The aim of this paper is to analyse the natural convective heat transfer generated by a source with a height of located in two different positions inside a square enclosure of side . In the first case, is 0.5 of while in the second case it is 0.4. The comparison is based both on the evaluation of the local and average Nusselt numbers at different Rayleigh numbers and on the study of the velocity fields at the same Rayleigh numbers in the two different configurations. The experimental analysis was carried out through a holographic interferometry, to study the heat transfer, and through a 2D-PIV system, to analyse the dynamic behaviour of the phenomenon. Finally, for = 0.5 we compared the experimental results with those obtained through the volume finite software Fluent 6.3.26. In the analysis, it is possible to see that the position of the source influences both the average Nusselt numbers on the hot surfaces and the development of a small bubble on the upper surface.

Experimental Evaluation of the Convective Heat Transfer Coefficients in a Nanofluid-Cooled Milli Channels Heat Sink

2007 ◽  
Author(s):  
Guillermo E. Valencia ◽  
Miguel A. Ramos ◽  
Antonio J. Bula
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Characteristics ◽  
Constant Heat Flux ◽  
Heat Transfer Process ◽  
Transfer Coefficients ◽  
Flux Boundary Condition ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

The convective heat transfer process and flow characteristics of aluminum oxide (Al2O3)/water nanofluid flowing through milli channels with a hydraulic diameters of 2 mm, with a constant heat flux boundary condition, was investigated. Using experimental equipment, the effect of some factors like volume fractions, Reynolds number and Peclet number are evaluated. Furthermore, an experimental model for Nusselt number is presented in order to show the enhancement of the convective heat transfer compared with a single-phase model in milli channel. Suggestions and direction for future developments for the use of nanofluids in milli channels are also presented.

An Experimental and Numerical Analysis of Natural Convective Heat Transfer in a Square Cavity With Five Discrete Heat Sources

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Giorgia Nardini ◽  
Massimo Paroncini ◽  
Raffaella Vitali
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Cavity Wall ◽  
Heat Sources ◽  
Square Cavity ◽  
Bottom Cavity ◽  
Vertical Walls ◽  
Rayleigh Numbers ◽  
Vertical Cavity

This paper provides an experimental and numerical investigation of natural convection in a square cavity. The square cavity is full of air (Pr = 0.71) and contains four heat sources of height hW, positioned symmetrically on the vertical walls of the cavity with a fifth heat source of height hB, located in the center of the bottom cavity wall. Two configurations are analyzed for Rayleigh numbers ranging from 1.00 × 104 to 1.00 × 105: configuration 1 has four cold sources located on the vertical cavity wall and configuration 2 has two hot and two cold sources located on the vertical cavity walls. An analysis of the holographic interferograms, numerical isotherms, streamlines, and velocity maps obtained demonstrates an increased development of natural convective heat transfer in configuration 1.

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