Numerical investigation of fin geometry on the air-side heat transfer and pressure drop characteristics of heat exchangers using in-line rectangular microchannels

The objectives of this research is to investigate the effect of different fin geometries on the performances of a microchannel heat exchanger, using CFD simulations. The fin profiles include straight fins, triangular fins, wavy fins and offset fins. For each fin geometry, air-side heat transfer and pressure drop correlations were developed and defined in terms of Colburn j-factor and Fanning f-factor. The microchannels are square 2.00 mm x 2.00 mm and placed in-line by 4.50 mm longitudinal tube pitch. The transverse tube pitch and the fin pitch were varied from 9.00 mm to 19.00 mm and 2.50 mm to 10.00 mm respectively, to investigate their influences on the heat exchanger performances. Furthermore, the complete thermal and hydraulic fully developed flow was covered using one CFD simulation, allowing to extract heat transfer and pressure drop characteristics for any number of channels. The results show that the offset fins present the best performances, in term of volume goodness factor, compared to all geometries. Using offset fins offers better heat transfer capability at a lower volume, which is beneficial in the need of reducing charge for refrigeration systems.