Heat exchanger for heating of fuel cell combustion air

A heat exchanger (110) for a solid-oxide fuel cell assembly comprising a plurality of parallel tubes (112) for conveying fuel cell stack exhaust gas from a first manifold means (132a) to a second manifold means (132b), whereby the tubes (112) are highly corrugated to increase the wall area and decrease the wall thickness. The tubes (112) are disposed in a jacket (150) through which is passed incoming air to be heated. The tubes (112) may be linear between two manifolds, or they may be curved such that the first and second manifold functions are accommodated within a single component.