Non-uniform condensation of refrigerant r134a in mini-channel multiport tubes: Two-phase pressure drop and heat transfer coefficient

© 2015 by Begell House, Inc.This study analyzes the refrigerant R134a non-uniform condensation flowing through a 10-port multiport mini-channel tube. The idea is to show that non-uniform flow yields a lower overall heat transfer coefficient. Experimental data are analyzed to get the influence of non-uniform flow over the global heat transfer coefficient taking into account the differences with the local heat transfer coefficient for each simple port. A mathematical method is presented to calculate a possible non-uniform distribution in multiple ports. This calculation procedure can be extended to any number of ports. Condensation in a single tube is uniform but in a multiport tube the amount of refrigerant going through each port may be not constant. Since the condensation process depends heavily on the vapor quality and mass flow in each port, in parallel flow condensers non-uniform distribution is surely present. In this work, various possible distributions have been evaluated under different operating conditions to assess the resultant change in its flow distribution and thermal performance. Our goal is to numerically determine how the non-uniform distribution of the refrigerant in a multiport mini-channel tube affects the heat transfer coefficient and compare these results with our experimental measurements.