An experimental investigation of cross flow heat transfer and fluid flow of air over a longitudinally finned flat tubes bank

Abstract

ABSTRACT This paper experimentally investigates the effect of transverse pitch on the heat transfer and fluid flow performance of the longitudinally finned flat tubes (LFFT) bank with staggered configurations. The studied Reynolds number (Re) was based on the hydraulic diameter of the flattened tube with a range of 223 ≤ Re ≤ 1114 . The tubes surfaces were maintained at constant temperature. Three dimensionless transverse pitches ( S T ˆ ) of LFFT were investigated, i.e. 3.0, 4.0, and 5.0, for dimensionless longitudinal pitch ( S L ˆ ) = 4.0, dimensionless upstream fin length ( L u ) ˆ = 0.8, dimensionless downstream fin length L d ˆ = 0.8, and dimensionless fin angle ( θ ˆ ) = 0.52, i.e. θ = 30°. The results showed that increasing S T ˆ from 3 to 5 slightly increased Nu at low Re, i.e. by 1.2% at Re = 223, At higher Re, i.e. 1114, Nu decreased by 20.8% for the same S T ˆ increase. Be decreased with increasing S T ˆ up to 60.7% at Re = 223. The thermal-hydraulic performance increased up to 153% at Re = 223.