A module for constructing therefrom a heat exchanger is provided. The module includes two manifolds and a plurality of parallely arranged mats spanning between the manifolds. Each mat includes a plurality of heat exchange tubes arranged so as to define a plane, the heat exchange tubes being in fluid communication with the manifolds and spanning therebetween. Each of the manifolds includes selectively sealable end openings formed in facing ends thereof and defining a longitudinal flow path substantially perpendicular to the tubes and parallel with the planes defined thereby. Each of the manifolds further includes selectively sealable side openings on facing sides thereof and each defining a lateral flow path substantially perpendicular to the longitudinal flow path and to the planes defined by the tubes.
