2. (5 pts.) Hot air at P = 2 atm pressure and 500K with a mass flow rate m = 12 kg/s flows across a circular finned-tube heat exchanger of the type shown in the following figures. The core dimensions of the heat exchanger are given in the figure. Calculate a) The average heat transfer coefficient on the air side, ha b) The friction factor, f The physical properties of hot air at 500K and 2 atm are: P-2 atm T-500 K m-12 kg/s P. 2 x 0.7048=1.41 kg/m³ 0.6 m C -1.0295 KJ/(kg. °C) Pr. = 0.68 0.8 m H.=2.671 x 10-5 kg/(m·s) Heat transfer and friction factor for low across circular finned-tube matrix. (From Kays and London.) - 0.070 0.060 0.050 0.040 0.030 0.020 B Tube OD Fin pitch Fin thickness Fin area/total area 0.862 て H.121 in 0.645 in) 1.35 i 0.1149 in -1.638 cm- 3.425/cm, -0.0254 cm D=0.5477 cm =0.5477-10 0.443 J-Amin A 8-0.010 in 0.5 m 0.010 To scale for "A" 0.008 0.006 0.005 0.004 1.0 20 3.0 4.0 6.0 8.0 10.0 Spacing 1.232 in B 1.848 in 0.645.n=0.0164m ReX 10-1 a) ha = 17 Hydraulic diameter D Minimum free-flow area/frontal area, Heat transfer area/total volume Quater -0.5477 0.443 -323.8 1.1674 cm 0.628 215.6 m²/m³ Х Q=MCAT Q=12(1.0295) (500k-o) =G177 V= 0.134 m*