Abstract: The V-type heat exchanger is commonly employed in duct-type air conditioners, although the non-uniform distribution of airflow velocity in the low duct would result in limited heat transfer capacity. Based on the match between the fin width distribution and the airflow velocity distribution, a C-type heat exchanger with non-uniform fin width was developed for the non-uniform airflow. The heat transfer characteristics of C-type and V-type fins were compared, and capacity was predicted and validated via simulations and tests. The effects of air temperature, condensing temperature, air volume, and air velocity distribution on the heat transfer were investigated. Results show that theoretical heat transfer capacity is maximized when the fin width distribution is proportionate to the power of airflow velocity distribution. The heat transfer area of the C-type fin matches with the airflow velocity better than the V-type fin. The local heat transfer capacity of the C-type fin is greater in most zones, hence the total capacity is greater. The heat transfer increase of the C-type heat exchanger over the V-type is more than 10% across a wide range of working conditions.

Key words: Duct-type air conditioner, Non-uniform airflow, C-type fin, Heat transfer