HEAT EXCHANGER TUBE
Coolant tubes (14) for heat exchangers are formed with projections (30) extending into the tube cross section to interfere with the fluid flow (28) and to ensure mixing of the coolant as it passes through the tubes. To achieve the necessary degree of mixing without causing the flow to become turbulent and thus to prevent unnecessary back pressure, the area of the tube wall occupied by projections (30) is less than 7.5% of the total area of the tube wall.