AUGMENTED HEAT-TRANSFER IN TRIANGULAR DUCTS WITH FULL AND PARTIAL RIBBED WALLS

Fully developed heat transfer coefficients and friction factors in triangular ducts with full and partial ribbed walls were experimentally obtained for Reynolds numbers between 10(4)-10(5). The vertex corners of the triangular ducts were 90, 55, and 35 deg. Five rib configurations were tested: full and partial 90-deg transverse ribs, full and partial 45-deg crossed ribs on three-wall, and partial 45-deg crossed ribs on two-wall of the triangular duct. The results show that heat transfer coefficients were higher on the ribbed walls and the 90-deg vertex corner of the triangular duct than on the 55-deg vertex corner, and subsequently higher than those on the 35-deg vertex comer. The heat transfer coefficients and friction factors in triangular ducts with partial ribbed walls (90- or 45-deg ribs) were 10% higher than those with full ribbed walls. The results also show that heat transfer coefficients and friction factors were higher in triangular ducts with 90-deg transverse ribs (full or partial) than those with 45-deg crossed ribs. The semi-empirical friction and heat transfer correlations in ribbed triangular ducts were obtained.