Multi-stream heat exchanger is one of the most important components in CO2 purification process, which is characterized as high efficiency, low consumption and high energy density. This work aims to develop a CFD model for a multi-stream heat exchanger, based on which the impact of the impurities on heat transfer characteristics is studied. Three streams are considered, including two streams flowing in two concentric pipes and one stream flowing perpendicularly to the pipes. Based on the model, this work calculates the pressure drop and the average heat transfer coefficient which is calculated from the average heat transfer coefficient of two interfaces formed from these three fluids. It is found that the average heat transfer coefficient and friction pressure drop have an obvious downward trend with the increase of the volume fraction of impurity gas; under the same volume fraction of impurity gas, both of them increase with the increase of refrigerant velocity.
Keywords Impurity, Heat transfer characteristics, CO2 condensation, Multi-stream heat exchanger