Steam generation

A heat exchanger assembly, comprising:

• heat exchanger pipework which comprises a plurality of elongate tube elements which extend in spaced relation;
• and
• a plurality of fins which extend in spaced relation, wherein the fins each comprise a sheet element which includes a plurality of apertures through which extend respective ones of the tube elements, and a plurality of fin coupling elements which are located within respective ones of the fin apertures to interface the tube elements to the sheet elements, wherein the fin coupling elements are fabricated separately of the sheet elements and each comprise a flange which extends through the respective fin aperture, and the fin coupling elements located within the fin apertures of one sheet element are separate of the fin coupling elements located within the fin apertures of other sheet elements, and wherein the fin apertures each include a first locator, and the fin coupling elements each include a second locator, which is configured to locate with the first locator in a respective one of the fin apertures, thereby locating the rotational position of the respective fin coupling element.