Theoretical design and drainage characteristic of a C-type heat exchanger in duct air conditioner

The conventional duct air conditioner typically uses an A-type heat exchanger for indoor units, which has poor drainage behavior under wet conditions. In this research, a C-type heat exchanger is developed for drainage improvement. The innovative design employs a unitary fin and a curved profile instead of the sectional fin and linear profile. Theoretical calculations are conducted, determining that the droplet sliding time on the cycloid is the shortest among the curves. The C-type is then produced and subjected to dynamic dip testing to assess its drainage performance. Results reveal that it achieves steady drainage within 3 s and reduces residual water by 10.9% compared to the A-type. A CFD model is generated to simulate the drainage process, with a calculated deviation of less than 10% for residual water. Finally, the C-type prototype is installed in the duct unit for performance measurement under wet conditions. It exhibits a 7.12% increase in heat transfer capacity and a 12.74% increase in drainage rate under the basic condition. The lower evaporating temperature, higher inlet air temperature, higher relative humidity, and larger air volume flow rate contribute to the more apparent drainage enhancement of the C-type