What special design feature may be found in the tubes of a supercritical boiler?

Rifled tubing is a special design feature that can be found in the tubes of a supercritical boiler. This design incorporates helical grooves or ribs along the interior surfaces of the tubes. The primary purpose of rifling is to enhance the heat transfer characteristics of the tubing. In supercritical boilers, where water is heated above its critical temperature, the risk of overheating is significant due to the extreme conditions the tubes are exposed to.

By introducing rifling to the tubing, the flow of water and steam is disrupted in a controlled manner, which improves turbulence. This turbulence boosts the overall heat transfer efficiency and minimizes the potential for hot spots that could lead to overheating or material degradation. Consequently, this design feature is crucial in ensuring safe and efficient operation in supercritical boiler systems, where maintaining precise thermal dynamics is essential for performance and reliability.