To solve the problem that plastic heat exchange tubes presented a low thermal conductivity

the surface hydrophilic(PVDF/SPES) and surface hydrophobic(PVDF) hollow fiber heat exchange tubes with dense/non-dense layer composite structure were prepared by controlling the content of sulfonated poly(ether sulfone)(SPES) in the casting solution during the course of non-solvent induced phase separation(NIPS). The outside surface contact angle of PVDF/SPES and PVDF tubes were 49.8° and 78.1°

respectively. The non-dense layer was filled with water to improve the thermal conductivity of heat exchange tubes. Single surface hydrophobic and hydrophilic heat exchange tube were weaved together to prepare tubular plastic heat exchanger. Thus

a hydrophilic/hydrophobic combination surface for steam condensation from outside surfaces of two tubes was built in the shell of heat exchanger. On this basis

the strengthening effect of steam condensation heat transfer on the combination surface was studied. The results showed that compared with the hydrophobic surface of dense PVDF heat exchange tubes prepared by melt-spinning method

the total steam condensation heat transfer coefficient on hydrophilic

hydrophobic and hydrophilic/hydrophobic combination surface prepared by NIPS method were improved by 46.6%

56.5%

and 99.7%

respectively. Therefore

the hydrophilic/hydrophobic combination surface could strength obviously steam condensation heat transfer in comparison with single hydrophilic and hydrophobic surface.