An improved apparatus providing for uniformity of web thickness. In one aspect, the apparatus includes a plurality of gap-controlling, thermal energy sources (44), and in heat-exchange communication with the thermal energy sources, an assembly (70) for compensating for temperature variation proximate to the thermal energy sources and across the apparatus width. The thermal compensating assembly includes a heat exchange jacket (72), and in combination therewith, a heat-exchanging, working fluid that undergoes a phase change in performing its heat exchange function.
In another aspect of the invention, the apparatus includes an element (100) disposed along an exit slot-forming lip (18'), that reduces localized thermal gradients along the lip. This element functions as a heat sink and a heat source proximate to the lip gap, and likewise includes a heat-exchanging, working fluid that undergoes a phase change.