Natural convection in an enclosure with discrete roughness elements on a vertical heated wall

Conference · Sat Feb 01 04:00:00 EST 1986

DOI:https://doi.org/10.1016/0017-9310(88)90251-7· OSTI ID:5776155

Shakerin, S; Bohn, M S; Loehrke, R I

Natural convection flow next to a heated wall with single and repeated, two-dimensional, rectangular roughness elements is studied numerically and experimentally. The objective is to determine how these roughness elements influence heat transfer rates from the wall. Each roughness element consists of a thermally conducting, horizontal cylinder of rectangular cross section attached to the heated, isothermal wall of an enclosure. The height of roughness is on the order of the boundary layer thickness. Dye flow visualization in water confirms the numerical prediction that the steady flow over these elements does not separate. Only at high Rayleigh numbers, when the boundary layer below the roughness is unsteady, is local instantaneous flow reversal observed. Although steady flow reversals near the wall are not predicted or observed, nearly stagnant regions are formed, particularly between closely spaced cylinders. The surface heat flux in these stagnant regions is relatively low, so the total heat transfer rate may be nearly the same as for a smooth wall in spite of the increased surface area.

• Research Organization: Colorado State Univ., Fort Collins (USA). Dept. of Mechanical Engineering; Solar Energy Research Inst., Golden, CO (USA)
• DOE Contract Number: AC02-83CH10093
• OSTI ID: 5776155
• Report Number(s): SERI/TP-252-2812; CONF-860805-7; ON: DE86004424
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140901* -- Solar Thermal Utilization-- Space Heating & Cooling
AIR FLOW
BUILDING TECHNOLOGIES
BUILDINGS
CONVECTION
ENERGY TRANSFER
FLOW VISUALIZATION
FLUID FLOW
FLUX
GAS FLOW
HEAT FLUX
HEAT TRANSFER
HEAT TRANSFER RATE
MASS TRANSFER
NATURAL CONVECTION
ROUGHNESS
SURFACE PROPERTIES
TWO-DIMENSIONAL CALCULATIONS
WALL
WALLS