Thermal performance of a cross-flow plate heat exchanger with rectangular finned channels

Abstract

The paper presents the construction and principle of operation of a cross-flow plate-fin heat exchanger. The two main types of matrix used in the recuperative device (for flat channels and with rectangular fins) are characterized in detail. The mathematical equations of the balances for the course of the heat and mass transfer process inside the flat channels and with the rectangular fins of the cross-flow heat exchanger were formulated. An original mathematical model of heat and mass transfer processes for a recuperative device was developed. A computer program was written using the Pascal programming environment. The program was used to conduct preliminary numerical simulations under the assumption of an 18-minute operation of the heat recovery unit. The nature of heat and mass transfer processes under condensation conditions is revealed. Three main areas of active heat and mass transfer (‘dry’, ‘wet’, and ‘frost’) and the limits of their formation have been identified. As the device was operated for a longer period of time, an increase in the area designated as the ‘frost’ zone was observed, from 11.9% to 15.6%. This was accompanied by a reduction in the area designated as the ‘wet’ zone, which decreased from 38.4% to 35.3%. The significant effect of frost layers on the airflow velocity inside the heat exchanger matrix was confirmed. The results demonstrated that the presence of a ‘wet’ area or a combined ‘wet’ and ‘dry’ area did not significantly impact the distribution of return airflow velocities.