contact therewith a finned tubular heat exchanger with rectangular plate fins 20 is shown in fig1 3 but the practice of the present invention may be easily extended to other fin geometries and types further the fins in the tubular array need not be planar fins or plate fins as shown in fig1 3 but may be individually attached fins e g a series of circular fins attached at intervals along the length of an individual tube or continuously applied helical fins or any other type of heat exchange fin apparent to one skilled in the art the fins can extend out from a given tube or row of tubes and not be attached to the other rows thereby not providing thermal conduction between the fin and several rows of tubes the present invention advantageously minimizes a temperature differential between a maximum temperature of a fluid in the second flow path i e in any one of the tubes in the array of tubes 3 and a minimum temperature of the fluid in the second flow path by providing tubes in the array of tubes 3 with different predetermined amounts of total heat exchange surface area per unit volume where the predetermined amounts are dependent upon a location distance of a tube to an inlet 12 of the first flow path indicated by arrow a the amount of total heat exchange surface area of a given tube can be identified by the total number and size of plate fins that are connected in a thermally conductive manner to that.