Analysis of flow structures and near wall behavior of fluid flow and local heat transfer in heat exchangers with inclined flat tubes

Abstract

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.

Compact flat tube heat exchangers with inclined refrigerant tubes and plane fins are studied at Reynolds numbers based on the hydraulic diameter of Redh=3900 and Redh=2500. The fluid field is measured parallel to the fins and the wall distance is varied. The fluid movement and particularly the change of fluid movement close to the fin are examined. A steady two dimensional CFD simulation is developed to provide an efficient model for geometric optimization. The model is validated by experimental flow measurements. This paper also compares the local heat transfer distribu-tion on the fin with near wall PIV measurements and seeks relations between certain flow structures and enhanced heat transfer. Shadowing effects prevent the examination of instan-taneous velocity fields in the named geometries. The gappy proper orthogonal decomposition (Gappy POD) is tested for the reconstruction of instantaneous velocity data in shadowed region.