The precondition should be discussed under the condition that the fuel quantity (heat load) is constant. For drum boilers, due to the increase of excess air coefficient, that is, the increase of air volume, the decrease of furnace temperature, the decrease of radiant heat absorption and evaporation. At the same time, because the drum boiler has a fixed evaporation point, the steam flow behind the drum decreases, but due to the increase of air volume and convection heat absorption, the main steam temperature increases. The main reason for the increase of reheat steam temperature is that the general reheater is convection type, the air volume increases and the convective heat transfer is enhanced. For once-through boiler, because there is no fixed evaporation point, the furnace temperature decreases, the evaporation point moves backward, and the main steam temperature decreases, which has the same influence on reheat steam as drum boiler.

I saw this on Polaris, and I was thinking about it.