This paper presents an in-depth study of the thermal performance of a gas-to-liquid "webbed tube" polymer heat exchanger. The heat exchanger was fabricated from a thermally enhanced polymer composite, consisting of a Nylon 12 matrix filled with carbon fibers. A laboratory-scale prototype heat exchanger was built using injection molding and tested on a cross-flow air-to-water heat exchange apparatus. The thermal performance of this laboratory webbed-tube polymer composite heat exchanger is studied in depth through an extended set of experiments, application of existing empirical correlations, and detailed computational fluid dynamic (CFD) simulations. The laboratory webbed-tube heat exchanger prototype provided a maximum UA value of 1.8 W/K and a volume-specific heat transfer coefficient of 14 kW/m(3) K. The experimental results, in conjunction with numerical simulations, were used to determine an "effective" thermal conductivity of 1.8 W/m K for the injection-molded Nylon-carbon composite material in the webbed-tube heat exchanger configuration. (C) 2016 Elsevier Ltd. All rights reserved.