Heat and mass transfer of a cooling coil in mixed convection mode: a computational analysis

This study numerically investigated heat and mass transfer from a cooling coil in a mixed convection regime, which is particularly relevant to dehumidification processes in HVAC systems. The research utilized the ANSYS Fluent solver to analyze a 2D laminar flow model. The primary focus was on the dimensionless Richardson number (Ri), which quantifies the relative importance of buoyancy forces to inertial forces. The findings show that as Ri increases, the flow regime transitions from being dominated by forced convection to being dominated by natural convection, leading to a significant decrease in both the average Nusselt number (Nu) and the average Sherwood number (Sh). This confirms a strong analogy between heat and mass transfer in this system. The results reveals that while Nu for a spacing of S = 0.08 m is approximately 7.4, the corresponding Sh is approximately 10.5 at a low Richardson number (Ri), demonstrating that the mass transfer rate is quantitatively higher than the heat transfer rate under these conditions. The study also revealed that while tube spacing had a notable impact on heat and mass transfer, the effect of the outlet opening size was found to be minor. Overall, the results provide valuable insights into optimizing dehumidification performance by controlling the balance between fan-driven and buoyancy-driven flow.