A long thin-walled double-pipe heat exchanger with tube and shell diameters of 1.0 cm and 2.5 cm, respectively, is used to condense refrigerant 134a at 20C by water. The refrigerant flows through the tube, with a convection heat transfer coefficient of
hᵢ = 5000 W/m² °C. Water flows through the shell at a rate of 0.3 kg/s. Determine the overall heat transfer coefficient of this heat exchanger.