Consider the following
1. Increasing evaporation rate using convection heat transfer from hot gases.
2.Increasing evaporation rate using radiation.
3.Protecting the refractory walls of the furnace.
4. Increasing water circulation rate.
The main in high pressure boiler furnaces would include
(a) 2 and 3 (b) 1 and 3
(c) 1and 2 (d) 1,2,3 and 4