In current study, the thermal and hydraulic performance of a novel bare tube heat exchanger prototype, manufactured by using stainless steel tubing with outer diameter of 0.8 mm, is experimentally investigated under dry and wet conditions. The inlet air dry bulb temperature is 26.7°C; the inlet air relative humidities are 35% (dry), 50% (wet) and 70% (wet) respectively; the inlet air frontal velocity are 3, 6 and 9 m/s respectively. The inlet water temperature is 12°C and the water mass flow rates are 20, 35 and 50 g/s respectively. The effects of inlet air humidity, air flow rate, water flow rate and orientation (vertical and horizontal) of heat exchanger were discussed. The test results show that the total heat transfer capacity increases as inlet air humidity increases, the air flow rate increases and water flow rate increases. The change of latent heat is affected by inlet air humidity, water flow rate and heat exchanger geometry. Airside pressure drop increases as air flow rate increases and inlet air humidity increases. Water flow rate increase has negligible influence when the surface is total wet or total dry and leads to pressure drop increase when surface is partical wet. Power law correlations of Chilton-Colburn heat transfer factor j, mass transfer factor jm and friction factor f were developed for Reynolds number range of 200~600. Maximum deviations are ±15%, ±10% and ±10%, respectively.