Heat exchanger in a modular construction

A heat exchanger, comprising:

• an external shell;
• and
• a plurality of heat exchanger modules disposed within the external shell, wherein
• said plurality of heat exchanger modules includes:
• at least one preheater module,
• at least one evaporator module, and
• at least one superheater module,
• each of the plurality of heat exchanger modules includes:
• an entry manifold extending through the external shell, the entry manifold at least partly supported by the external shell,
• an exit manifold extending through the external shell, the exit manifold at least partly supported by the external shell, and
• meandering pipes through which a heat-absorbing medium flows from the entry manifold to the exit manifold,
• when the plurality of heat exchanger modules includes a plurality of evaporator modules, the plurality of evaporator modules are connected in parallel via a steam-collecting drum situated outside the external shell,
• the entry manifold of each of the plurality of heat exchanger modules is offset from a center axis of the external shell
• in a plane transverse to the center axis of the external shell, and
• in an offset direction different from an offset direction of a corresponding heat exchanger module exit manifold,
• a longitudinal axis of the external shell is aligned with a first direction,
• each of the plurality of heat exchanger modules has a number of pipe layers, each of the number of pipe layers including an equal number of pipes, each of the number of pipe layers having a plurality of distinct connections to the corresponding entry manifold, centerlines of the equal number of pipes in each of the number of pipe layers being aligned in the first direction, centerlines of corresponding pipes in adjacent pipe layers being aligned in a second direction that is perpendicular to the first direction, and
• the corresponding pipes in adjacent pipe layers have opposing parallel flow directions of the heat absorbing medium along a third direction, the third direction being perpendicular to the first direction and the second direction.