In a 2.5 cm inner diameter (id) tube, water enters at 90 ° c and 6 m / s. the tube is copper and it has a thickness of 0.8 mm and a length of 3m. in the normal direction outside the tube, ambient air circulates at 1 atm and 20 ° c, with h = 7 w /m^2 ° c. calculate the air temperature at tube outlet. what would be the effect of reducing the hot air stream in half ? . kcobre =378.7 w / (mk)

Steel balls 12 mm in diameter are annealed by heating to 1150 k and then slowly cooled to 400 k in an air att 325 k and h -20 w/m2 k. assume the properties of the steel to be k- 40 w/m k,p 7800 kg/m3, and cp 600 j/kg k. a. determine whether lumped system method can be used to analyze this problem and if so why" b. determine the time required for the cooling process. c. determine the total amount of heat lost from each ball to the ambient air