Impact of distributor design variables on heat transfer characteristics in falling film evaporators using water

Falling film evaporators have been widely utilized due to their high heat-transfer efficiency and low refrigerant charge. However, there is limited research on the impact of distributor design variables on the heat transfer coefficient (HTC) in falling film evaporators. This study investigates the effects of these variables–hole diameter, hole pitch, and distributor height–on the heat transfer characteristics of water in falling film evaporators using three-dimensional simulations. Hole diameter had the most significant influence on HTC, with a sensitivity of 63.1 %, followed by hole pitch at 46.3 %, and distributor height at 0.9 %. Smaller hole diameters enhanced the HTC, but for diameters greater than 2 mm, the effects of hole diameter and pitch on the axial HTC became negligible. The HTC increased with hole pitch up to the dry-out owing to the jet impingement. The influence of distributor height on HTC was minor, particularly at a hole diameter of 1 mm. The optimal design for the highest average HTC at a film Reynolds number of 200 was determined to be a hole diameter of 1 mm, a hole pitch of 37.5 mm, and a distributor height of 30 mm, resulting in a 50 % improvement in performance compared to the least effective design.