Pressure Drop Measurements in Microchannel Heat Exchanger

Single-phase pressure drops inside a microchannel heat exchanger were tested systematically. Local pressure drop coefficients were determined from the experimental data and compared with published correlations. Results confirmed the Moody Chart to be applicable for the submillimeter channel flows used in heat exchangers explored. Based on nonintrusive testing followed by destructive evaluation, two types of manufacturing defects were quantified: variation of microchannel port diameters; and port blockage by brazing flux. A pressure drop model for the whole heat exchanger was developed, and predicted the pressure and mass flow rate distribution inside the heat exchanger. It can also be used as a design tool to optimize microchannel tube dimensions and heat exchanger circuiting. Most importantly, simple nitrogen flow tests can now be used to control the quality of the brazing process by detecting the presence of blocked or deformed ports in the finished product