Heat exchangers have been used for a broad range of industrial applications. Due to its good thermal conductivity and mechanical strength, metal has been widely applied for making the heat exchangers. Recently, however, because of their superior characters, including corrosion resistance, cost-effectiveness, light-weight, high ratio of surface-area to volume, dual transport ability, and less fouling ability, polymeric hollow fibers (PHFs) have been used for fabricating heat exchangers for many applications. The purpose of this paper is to present a versatile numerical model, which can be conveniently used for designing PHF heat exchangers (PHFHEs) and reliably used to predict the thermal characteristics of the heat exchangers, including fluid outlet temperatures, external, internal, and overall heat transfer coefficients, and total heat transfer rate as well as the thermal efficiency.