The polymer hollow fiber heat exchangers have been of great interesting because of their low investment, lightweight and corrosion resistant features in comparison with metal heat exchangers. This paper is focused on heat transfer process with and without phase change by experimental investigations of poly(vinylidene fluoride) (PVDF) hollow fiber heat exchangers. The maximum overall heat transfer coefficient (OHTC) in the experiments reached up to 612 W/(m(2).K) for liquid-liquid system, 883 W/(m(2).K) for condensation system and 1168 W/(m(2).K) for condensation/evaporation system. The phase change remarkably improved the heat transfer performance. With respect to experimental results, a new correlation was developed to predict the condensation heat transfer coefficients. Furthermore, the thermal efficiency of the vertical tube evaporator achieved up to 92%. The comparison of the present hollow fiber heat exchanger with other desalination technologies suggested that the superior performances of high efficient, compact, anti-corrosion and anti-fouling made this technology more prospect in desalination field.