In a crossflow heat exchanger with in-line tubes, air flows across a bundle of tubes at 5? and is heated to 32?. The inlet velocity of air is 15 m/s. Dimensions of tubes are: d0 = 25 mm and Xt =Xl = 50 mm. There are 20 rows in the flow direction and 20 columns counted in the heat exchanger. The air mass flow rate is 0.5 kg/s. Air properties may be evaluated at 20? and 1 atm. Calculate the frictional pressure drop and the pumping power.