A cold fluid at 17 C (p = 4.18 J / g C) flowing through the countercurrent shell in a concentric tube exchanger is used to phase change a fluid that is fed as saturated steam at 120 C and 12.9 kg / min (Dv = 2,203 J / g). If the length of the inner tube is 129 m, with an outer diameter of 2.5 cm, and the heat transfer coefficient Uo = 388.88 W / m2 R, obtain the outlet temperature and the mass flow of the cold fluid using the -NTU method.