Experimental investigations of heat transfer characteristics and performance enhancement of shell and helical coil water coolers using external radial fins and different shells diameters were conducted. The study aims to enhance the water coolers performance in a trial to improve coil compactness. Two helical coils; one with a plain tube and the other with external radial fins, were tested in four shells of different tube diameters. Refrigerant passing inside the helical coils was used to cool water that enclose/passes in the space between the helical coil and the shell. Tests were conducted under mixed convection heat transfer regimes. Results showed performance and compactness enhancement with the insertion of external radial fins and increasing the shell diameter to helical coil diameter ratio. For nonfinned and finned coils, Nusselt number increased with increasing Reynolds number, Grashof number, and shell diameter. Correlations were predicted to give the Nusselt number in terms of Reynolds number, Grashof number, and shell diameters for finned and nonfinned helical coils. Correlations predictions were compared with present and previous experimental results and good agreements were obtained. C⃝

In the present study, the thermal performance and pressure drop characteristics of wet air-conditioning cooling coils are investigated under the hot arid climate of Cairo. The effect of fin patterns, fin pitch, and air velocity on the heat transfer performance of direct expansion cooling coils is presented. Five test specimens of cooling coils are tested involving flat, corrugated, and louvered fins. In addition, different fin pitches are considered for louvered-fin cooling coils. Reynolds number for the air side ranged from 65 to 1200, corresponding to face velocity of 0.43-6.65 m/s. Four methods of performance criteria are presented to interpret how different fin geometries of cooling coils could affect the overall performance of the air-conditioning unit. At a certain value of pressure drop of 50 Pa, the air heat transfer coefficient for louvered fins is higher than that of corrugated and flat fin cooling coils by 29.4% and 47%, respectively. The energy efficiency ratio for louvered fins is higher than that of corrugated and flat fin cooling coils by 9% and 17.4%. The air-conditioning system having a cooling coil with lower fin pitch and enhanced fin surfaces is more energy cost effective.

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