Heat exchanger having a contoured insert and method of assembling the same

A method of manufacturing a tube including an insert for a heat exchanger, the method comprising:

• feeding a sheet of heat conducting material toward a first roller and a second roller, the sheet including a length, a first side, and a second side;
• roll-forming a first row of dimples in the sheet with the first roller such that the first row of dimples extends into the first side of the sheet;
• roll-forming a second row of dimples in the sheet with the second roller such that the second row of dimples extends into the second side of the sheet;
• folding the sheet to form a fold having a peak, a first leg and a second leg, the peak extending in a direction generally parallel to the length of the sheet and the peak being between the first row of dimples and the second row of dimples such that the first row of dimples are on the first leg and the second row of dimples are on the second leg of the fold;
• and
• after folding the sheet of material, surrounding the sheet of material with the tube having a length such that the fold extends in a direction substantially parallel to the length of the tube such that the sheet forms the insert of the tube.