1. Heat transfer characteristics in air-conditioned rooms using mixing air-distribution system under mixed convection conditions
- Author
-
Al-Sanea, Sami A., Zedan, M.F., and Al-Harbi, M.B.
- Subjects
- *
HEAT transfer , *AIR conditioning , *HEAT convection , *COMPUTATIONAL fluid dynamics , *TEMPERATURE distribution , *TURBULENCE , *THERMAL analysis , *NUSSELT number - Abstract
Abstract: The present paper deals with CFD study of flow and thermal characteristics in air-conditioned rooms under turbulent mixed convection conditions. Air enters room from a sidewall slot flush with isothermal ceiling and leaves through a slot in opposite wall flush with floor. Velocity and temperature distributions are determined by a CFD model that has been previously validated by comparison with experimental data. Rigorous dimensional analysis shows that performance of the air-distribution system depends on: supply Reynolds number Re d , Grashof number Gr d (or Archimedes number Ar d ), room aspect ratio L/H, dimensionless heights of supply and return ports (d/H and t/H), where H is room height. For a room with fixed geometry, the effects of Re d and Gr d (or Ar d ) are investigated systematically by varying one parameter at a time. Results show that ceiling average Nusselt number (Nu d,av) increases with Re d and decreases with Gr d (or Ar d ). For a given Gr d , the heat removal index (HRI) increases with Re d up to Re d ≈ 9000, then stays practically constant thereafter. For a given Re d , HRI decreases with increasing Gr d (or Ar d ). A criterion for distinction between forced and mixed convection situations is developed, resulting in a critical Archimedes number of 0.11. Results further indicate that Ar d alone, irrespective of the particular values of Re d and Gr d , determines to a reasonable extent Nu d,av and HRI when Ar d is above its critical value. Streamlines and temperature contours are found to be consistent with other results and helped explain them. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF