Flexible assembly of once-through evaporation for horizontal heat recovery steam generator

A steam generator, comprising:

• an inlet manifold;
• a discharge manifold;
• a heating gas duct;
• and
• a once-through heating area disposed in the heating-gas duct through which a heating gas flow is conducted, said once-through heating area being formed from a plurality of single-row header-and-tube assemblies, each of said plurality of single-row header-and-tube assemblies including a plurality of steam generator tubes connected in parallel for a through flow of a flow medium therethrough, each of said plurality of single-row header-and-tube assemblies further including an inlet header connected to said inlet manifold and a discharge header connected to said discharge manifold, each of said inlet headers being connected to said inlet manifold via a respective one of a plurality of first link pipes, each of said discharge headers being connected to said discharge manifold via a respective one of a plurality of second link pipes, and each of said steam generator tubes of each of said single-row header-and-tube assemblies having an inside diameter that is less than an inside diameter of any of said plurality of first link pipes and of any of said plurality of second link pipes.