What is the purpose of using multiple inlet manifolds in a economizer?

In a boiler, a cylindrical pressure vessel that connects many tubes with identical functions arranged in parallel is called a header or manway. In the system, it primarily serves to collect, mix, and redistribute the working fluid. The heating surfaces of boilers, such as the water wall, economizer, superheater, and reheater, require a large number of manifolds. Junction boxes are mostly made of seamless steel tubes with a larger diameter and the same material as the heating surface. The working fluid is introduced into the header through some pipes, which serves to collect the fluid ； The working fluids mix with each other within the header, achieving uniformity in quality and temperature and eliminating or reducing the thermal gradients that occur in the heated sections ahead ； The working fluid is led out through pipes from the header, serving to redistribute it.