Thermal stress relief stiffener

A heat exchanger comprising:

• a header plate comprising a plurality of openings;
• a plurality of tubes, each of the plurality of tubes having an end portion, each of the plurality of tubes being inserted into one of the plurality of openings in the header plate, and each of the plurality of tubes having an inner wall defining a through-hole in the tube;
• and
• a stiffener reinforcing the end portion of at least one of the plurality of tubes, the stiffener including two legs extending from opposing sides of a top plate, the top plate extending along a first plane, each leg including a transition, an angled segment, and a straight segment disposed orthogonal to the top plate, the angled segment extends at an angle greater than zero relative to the straight segment and extends at an angle less than ninety degrees relative to the first plane, a proximal end of the transition being connected to the top plate, a distal end of the transition being connected to the angled segment, and a proximal end of the straight segment being connected to the angled segment, wherein
• each of the transition, the angled segment and the straight segment extends in a first direction away from a plane defined by a top surface of the top plate such that a distal end of the straight segment is furthest from the top plate, and
• an inner surface of the angled segment exerts a force on a first side of an inner wall of the at least one of the plurality of tubes, deforming the stiffener and forcing an outer surface of the straight segment into contact with a second side of the inner wall, the second side being opposite the first side in a cross sectional view.