Thermal performance of the chilled water spirally coiled finned tube in cross flow for air conditioning applications

The thermal performance of spirally coiled finned tube in cross flow was investigated experimentally. The effects of curvature ratio, flow direction, fin pitch and flow rate of chilled water and air on thermal characteristics of spirally coiled finned tube have been studied. Six test sections with curvature ratios of 0.027, 0.03, 0.04, tube pitches of 18, 20, 30 mm, and fin pitches of 33, 22, 11 mm were used. The experiments were done using a pilot wind tunnel with air Reynolds number range 35,500-245,000. Innermost and outermost flow directions of chilled water with Reynolds number range 5700-25,300 have been investigated. The innermost flow direction has significant enhancement effect on the Nusselt number compared with outermost flow direction. The decrease of fin pitch enhances the Nusselt number on expense of pressure drop. Decreasing the curvature ratio increases air side Nusselt number on expense of pressure drop. A set of empirical expressions for predicting the friction factor and the Nusselt number for air flow across the spiral coils have been regressed based on the obtained data in the present experiments.