PERFORMANCE ENHANCEMENT OF ENHANCED HERRINGBONE WAVY-FIN ROUND TUBE INCLINED HEAT EXCHANGERS WITH AND WITHOUT HYDROPHILIC COATING USING EVAPORATIVE SPRAY AND DELUGE COOLING

摘要

An experimental study has been conducted to evaluate the performance of two herringbone wavy-fin round tube compact heat exchangers working as coolers, with frontal areas of approximately 0.24 m~2 each in both dry and wet conditions. Heat exchanger capacity and air-side pressure drop were measured with the heat exchanger angle set at 20° from vertical. Deluge water cooling was achieved by incorporating a water distributor on top of the heat exchanger from which wetting water overflows as thin film over the top leading edge of the heat exchanger fins. A hollow cone nozzle was used for spray cooling. Water was used as a refrigerant, and enters the heat exchanger tubes at 43°C temperature. Ambient air, deluge and spray cooling water were maintained at 28°C temperature, and frontal air velocity was varied from 1.5 m/s to 3.0 m/s. Capacity was significantly enhanced for all heat exchangers using both deluge and spray cooling. However, the air-side pressure drop penalty ratio was much higher for deluge cooling. Furthermore, heat exchanger with hydrophilic coated fins achieved higher capacity enhancement ratios. This study contributes 8 dry cases and 48 wet cases experimental data points of wavy-fin heat exchanger performance. Future studies would aim at obtaining higher capacity enhancement ratios for spray cooling while maintaining air-side pressure drop penalty ratio of 1.0.