Experimental Study of Double Pipe Helical Coil Heat Exchangers in the Laminar to Transitional Flow Regime

This study experimentally investigates various heat transfer characteristics, pressure drop, friction factor, Nusselt number, and Dean Number in a double-pipe helical coil heat exchanger. The study examines the hot water mass flow rates ranging from 0.02 to 0.12 kg/s and the cold-water mass flow rates ranging from 0.055 to 0.15 kg/s. The cold-water inlet temperature was maintained at 29°C, while the hot water inlet temperature varied between 65-75°C. Based on the hydraulic diameter of the annular space between the two tubes, the Reynolds number ranged from 1000-6000. All required parameters, such as the inlet and outlet temperatures of the inner coil and annulus fluids and the flow rate of fluids, were measured using appropriate instruments. Seventy-two test runs were conducted, from which the heat transfer coefficients of the inner coil side and annulus side were calculated. The calculated heat transfer coefficients of the inner coil were compared with available correlations from the literature, and a reasonable agreement was found.