Which type of superheater uses direct radiation from the furnace?

The radiant superheater is specifically designed to utilize direct radiation from the furnace to heat the steam. In this configuration, the superheater is positioned within the furnace area where it can absorb the intense heat generated by the burning fuel. This direct exposure to radiant heat allows for more efficient heating of the steam since it capitalizes on the high temperature present in the furnace.

Radiant superheaters are typically employed in applications where high steam temperatures are required, as they can achieve efficient heat transfer and enhance the overall energy efficiency of the system. The design maximizes the use of radiant heat, which is a fundamental aspect of its operation, distinguishing it from other types of superheaters that rely more on convection methods for heat transfer.

In contrast, convection superheaters utilize heated gases from combustion for steam heating, while combination superheaters incorporate both radiant and convection heating. An economizer type, on the other hand, primarily preheats feedwater and does not function as a superheater. The unique operational characteristics of the radiant superheater make it the correct choice for this question.