A radiant oven for drying newsprint consists of a long duct (L = 20 m) of semicircular cross section. The newsprint moves through the oven on a conveyor belt at a velocity of V = 0.2 m/s. The newsprint has a water content of 0.02 kg/m2 as it enters the oven and is completely dry as it exits. To assure quality, the newsprint must be maintained at room temperature (300 K) during drying. To aid in maintaining this condition, all system components and the air flowing through the oven have a temperature of 300 K. The inner surface of the semicircular duct, which is of emissivity 0.8 and temperature T1, provides the radiant heat required to accomplish the drying. The wet surface of the newsprint can be considered to be black. Air entering the oven has a temperature of 300 K and a relative humidity of 20%.Since the velocity of the air is large, its temperature and relative humidity can be assumed to be constant over the entire duct length. Calculate the required evaporation rate air velocity u?, and temperature T1, that will ensure steady-state conditions for the process.

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Air T= 300 K p-l atm - 0.20 T.- 300 K LT. E = 08 300 K, =1.0 V= 0.2 m/s -0.20 Dry newsprint Wet newsprint W = 1 L= 20 m m