Abstract: A heat exchanger is disclosed. The heat exchanger has structural members made of fiber reinforced resin material. These structural members include vertical columns and walls. The walls are bonded to the columns to create rigid joints. The bonded joints have large surface areas. The walls are defined by individual panels that may be bonded together along abutting horizontal box beam sections. The panels have additional box beam sections to strengthen the panels, and connecting webs extending between the box beam sections. Both the box beam sections and connecting webs are bonded to the columns. Mechanical fasteners are used to hold the walls and columns together until the bonding material cures. The heat exchanger is an evaporative heat exchanger with a basin with a sloping floor having a low point. The sloping floor may be made of panels bonded together. The panels are similar in structure to the wall panels, although the box beams may be of different sizes.