During open-heart surgery, a patient’s blood is cooled down to 25 °C from 37 °C using a concentric tube counter-flow heat exchanger. Water enters the heat exchanger at 4 °C and leaves at 18 °C. Blood flow rate during the surgery is 5 L/minute.

Use the following fluid properties:

Fluid Density (kg/m3) Specific heat (J/kg-K) Blood 1050 3740 Water 1000 4200

Effectiveness of the heat exchanger is _________ (round off to 2 decimal places).