CFD-based correlation development for air side performance of small diameter tube-fin heat exchangers with wavy fins.

A great deal of effort is spent on the design and optimization of air-to-refrigerant heat exchangers in HVAC&R applications. One path towards improving their performance is the transition to smaller hydraulic diameter flow channels. In particular, tube diameters below 5mm need to be investigated. The in-tube refrigerant flow characteristics are well understood for small diameter tubes and accurate heat transfer and pressure drop correlations are available in the literature. On the air side, however, most of what is available in the literature has none, or very limited applicability to small tube diameter heat exchangers. In these situations numerical methods such as CFD are commonly employed in the performance evaluation of tube and fin surfaces. This work presents new CFD-based correlations for finned tube heat exchangers with tube diameter ranging from 2mm to 5mm. The methodology implemented in this work consists of analyzing air-side heat transfer and pressure drop characteristics by using Parallel Parameterized CFD (PPCFD. The post-processed data is reduced into correlations that can be easily implemented in various heat exchanger analyses tools. The j and f factors correlations fit, 64% and 66% of the source data respectively, within an error of 20%. As new experimental data becomes available, the correlations will be validated and updated. In the meanwhile, researchers and engineers can use these correlations for evaluating the performance of small tube diameter heat exchangers.