Conjugate natural convection heat transfer in a vertical annulus with internal circumferential fins

A numerical investigation is carried out to study natural convection heat transfer in a vertical annular enclosure with circumferential fins mounted on the inner cylinder. Heat is generated within the inner solid cylinder, while the top, the bottom, and the outer walls are exposed to convection. The results show that, even though the presence of fins does not alter the main features of the flow in the large-scale recirculation zone, it reduces the mean temperature of the inner cylinder by a maximum of 9.6% at low Rayleigh numbers. Also, the number and length of fins have a pronounced effect on the mean temperature. © 1994 Taylor and Francis Group, LLC

Interaction between a buoyancy-driven flow and an array of annular cavities

A numerical study is performed to investigate the interaction between a buoyancy-induced flow and an array of annular cavities. The buoyant flow is generated in a vertical annular enclosure with a centrally-positioned finned inner cylinder. Heat is generated within the inner cylinder, and it is convected through the inter-fin cavities and annular enclosure to the outside environment. The results indicate the presence of a twin recirculating bubble in each cavity. At higher Ra, the main flow enters the cavities and removes the recirculating flow. These observations are more pronounced at higher Pr. For more slender and deeper cavities, the recirculating bubbles closer to the finned wall collapse and split into two bubbles. The presence of cavities create a nearly uniform high-temperature zone adjacent to the finned wall. As the fin length is reduced and the cavities become more shallow, this zone shrinks and the main buoyancy-driven flow maintains a closer thermal communication with the finned wall. © 1994 Indian Academy of Sciences

New correlation for pressure drop in arrays of rectangular blocks in air-cooled electronic units

An experimental work is carried out to investigate the pressure drop and to visualize the flow field in the entrance region of an array of rectangular modules attached to the lower wall of a duct. The modules are positioned in an in-line arrangement to simulate the geometry often encountered in the cooling passages of electronic units. The investigation is performed in both laminar and turbulent regions with Reynolds number ranging from 400 to 15000. The geometric parameters range from H/L = 0.125 to 1.5 and S/L = 0.125 to 0.5, while the value of B/L is fixed at 0.5. The flow visualization revealed a highly separated region on the first module of the array. The pressure drops are correlated for the range of Re, H/L, and S/L employed in this work

A correlation for heat transfer and wake effect in the entrance region of an in-line array of rectangular blocks simulating electronic components

An experimental investigation is carried out to study heat transfer in the entrance region of an array of rectangular heated blocks. The focus of the work is on the entrance heat transfer coefficients and the associated thermal wake effects. The experiments were performed with air as the working fluid. The geometric parameters of the array were varied in the range identified with B/L = 0.5, S/L = 0.128-0.33, and H/L = 0.128-1. The Reynolds number, based on the height above the blocks and the fluid mean velocity in the bypass channel, ranged from 3000 to 15,000. The adiabatic heat transfer coefficients and thermal wake effects are correlated for the entrance region. These correlations are incorporated into a user-friendly FORTRAN program, which can be used by the engineers to predict the working temperatures of the components of circuit boards with similar layout. A typical computer output indicated that the mean deviation between the measured and predicted temperatures is 11.0 percent. © 1995 by ASME

Entrance analysis of turbulent flow in an array of heated rectangular blocks

A numerical study is conducted to investigate the entrance behavior of turbulent flow over arrays of rectangular heated blocks. The problem formulation is three dimensional and the solution domain includes both the developing and fully-developed regions of the array. The blocks are deployed along the lower wall of a parallel-plate duct in an attempt to simulate the cooling passages of electronics equipments. The standard k-ε turbulence model was applied to the developing region of the flow at high Reynolds numbers, while a modified Lam-Bremhorst turbulence model was considered at low-Reynolds numbers. The computations are performed for two conventional thermal boundary conditions, namely constant heat flux and constant wall temperature. Reynolds numbers ranged from 102 to 105, with Prandtl number being equal to 0.7. The array geometry was identified with H/L = 1/8, S/L = 1/8, B/L = 1/2 and the entrance length, I/L = 1/2, 2 and 6. To evaluate the accuracy of the turbulence models, numerical solutions were compared with experiment