For which one of the following situations would Kendall’s tau be appropriate? a) The Mohs scale rates the hardness of minerals. If one mineral can scratch another, it is judged….

## calculate the time in the dryer in the constant-rate zone and the falling-rate zone.

Drying in a Continuous Tunnel Dryer. A rate of feed of 700 lb_{m} dry solid/h containing a free moisture content of X_{1} = 0.4133 lb H_{2}O/lb dry solid is to be dried to X_{2} = 0.0374 lb H_{2}O/lb dry solid in a continuous-counterflow tunnel dryer. A flow of 13 280 lb_{m} dry air/h enters at 203°F with an H_{2} = 0.0562 lb H_{2}O/lb dry air. The stock enters at the wet bulb temperature of 119°F and remains essentially constant in temperature in the dryer. The saturation humidity at 119°F from the humidity chart is H_{W} = 0.0786 lb H_{2}O/lb dry air. The surface area available for drying is (A/L_{S}) = 0.30 ft^{2} /lbm dry solid.

A small-batch experiment was performed using approximately the same constant-drying conditions, air velocity, and temperature of the solid as in the continuous dryer. The equilibrium critical moisture content was found to be X_{C} = 0.0959 lb H_{2}O/lb dry solid, and the experimental value of k_{y}M_{B} was found as 30.15 lb_{m}air/h · ft^{2}. In the falling-rate period, the drying rate was directly proportional to X.

For the continuous dryer, calculate the time in the dryer in the constant-rate zone and the falling-rate zone.