An Experimental Study of Liquid-Phase Heat Transfer in Multiport Minichannel Tubes

Heat transfer has been evaluated experimentally on the tube side of three different minichannel tubes, so-called multiport extruded (MPE) tubes, with different cross-section geometry. The objective was to find out which correlations, models, and relations should be used when predicting the performance of complete heat exchangers consisting of such tubes. The geometry of the tube channels or ducts was rectangular with different aspect ratios and one of the tubes was equipped with surface enlargements inside the channels. Evaluations were performed with four different secondary refrigerant liquids: water, propylene glycol, Hycool 20, and Temper-20. The laminar flow regime was the main focus of the investigations. Despite the shape of the minichannels, best agreement was found with a model presented by Gnielinski for laminar flow, developing temperature profile, and fully developed velocity profile in circular tubes with the constant wall temperature boundary condition.