Problem 2 25 Points A Cylinder D 1 Cm L 30 Cm Of A Porous Material Is Being Dried In A Convection Oven Heated 1 (70.34 KiB) Viewed 41 times
Problem 2. (25 points) A cylinder (D = 1 cm, L = 30 cm) of a porous material is being dried in a convection oven. Heated air flows past the cylinder at a velocity of 0.5 m/s. The dry bulb temperature is 100 °C and the wet bulb temperature is 55 °C. The cylinder temperature is also 55 °C. At 100 °C: Pair = 0.946 kg/m³; MW air = 28.97 kg/kgmol; µair = 1.725 x 10¹5 kg/m s; Dwater-air= 0.300 m²/s a) Estimate the rate of drying in the constant rate regime (Rc) based on the mass transport coefficient (kc). (15 points)
Problem 2 continued 0 10 percentage humidity 20 30 40 50 60 70 Temperature (°C) 80 90 adiabatic saturation curve 100 110 120 0.15 0.14 0.13 0.12 0.11 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 10 130 Humidity, H (kg water vapor/kg dry air)
Problem 2 continued b) You measure the drying rate at two points in the falling regime: X kg H₂0 kg dry solid, R (kg H₂0) hm² 0.30 1.7 0.05 0.20 The density of the dry solid cylinder is p= 0.200 g/cm³. The cylinder dimensions are the same as in part a. Assuming that R is linear with X in the falling rate regime, what is the time required to dry the cylinder of material from X₁ = 0.25 to X₂ = 0.10? (10 points)
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