Average Heat Transfer Coefficient in Rectangular Ducts with Baffle Blockages

An experimental investigation was conducted to study the average and the fully-developed heat (mass) transfer coefficients in a rectangular smooth duct and a duct with repeated-baffle blockages. The focus of attention in this work is the conventional correlation Nu / Nufd ۱ + C / ( X / D ) for the average heat transfer coefficient. It was shown that for relatively short ducts, the coefficient C is not constant but, in general, it depends on the length of the duct. The experiments were carried out via a mass transfer technique and the analogy between heat and mass transfer was employed to predict the heat transfer coefficients. The flow Reynolds number ranged from ۳۰۰۰ to ۵۰,۰۰۰ with the height of the baffles equal to h/H = ۰, ۰.۱۲۵, ۰.۲۵ and ۰.۵۰.