Water at 15C is to be heated to 65C by passing it over a bundle of 4-m-long, I-cm-diameter resistance heater rods maintained at 90C. Water approaches the heater rod bundle in normal direction at a mean velocity of 0.8 m/s. The rods are arranged in-line with longitudinal and transverse pitches of SL = 4 cm and ST = 3 cm. Determine the number of tube rows NLin the flow direction needed to achieve the indicated temperature rise. Water 15C =4 cm 0.8 m/s SL D=1 cm T, = 90C Sr = 3 cm FIGURE P7-85