Polymeric hollow fiber heat exchangers (PHFHEs) consist of hundreds of polymeric hollow fibers with an outer diameter of circa 1 mm. Even though polymers do not have outstanding thermal conductivity, PHFHEs are effective heat exchangers due to the tremendously low thickness of the fiber wall (approximately 0.1 mm). PHFHEs are heat exchangers with large packing density, i.e. they have a large heat transfer area concerning their volume. Their main advantages are 1) low weight, 2) easy machining and shaping, 3) extraordinary chemical and corrosion resistance, and 4) being more environmentally friendly than commonly used metal materials. Concretely, extruded polymer products around five times less CO₂ than extruded aluminum. Presented polyamide PHFHE with 800 fibers with a length of 170 mm and an outer diameter of 1 mm was measured in an aerodynamic tunnel as a cross-flow heat exchanger. Hot water flowed inside the fibers with an inlet temperature of 50° C with a varying flow rate between 20 and 150 l·h⁻¹. The ventilator inside the tunnel induced the airflow with various velocities (2, 4, and 6 m·s⁻¹). The thermal performance and air pressure drop were evaluated based on experiments. Results were further compared with the conventional aluminium heat exchanger of similar size. In all cases, the thermal performance of the plastic alternative was at least 5% higher. Concretely, it varied between 340 and 1000 W. The highest value corresponds to the flow rate of 150 l·h⁻¹ and air velocity of 6 m·s⁻¹.