A tube assembly for cooling an incoming fluid stream and destroying pollutants contained therein comprises a tube with a catalytic coating on its inner wall and an arrangement for disrupting laminar flow of the fluid stream as it transits the tube, thereby causing turbulence which increases mass transfer between the gas phase and the catalyst-coated inner surfaces. One embodiment comprises an axially inserted turbulator that is segmented by one or more axially directed cuts, each segment rotated by an offset angle with respect to an adjacent segment, and optionally coated with the catalytic coating. Another embodiment comprises sets of opposed dimples, each set separated from its adjacent set by a linear distance and an axial angle. Such tube assemblies may be advantageously employed in aircraft environmental control systems for conditioning cabin air.