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Wet solids pass through a continuous dryer. Hot dry air
Chapter 8, Problem 8.73(choose chapter or problem)
Wet solids pass through a continuous dryer. Hot dry air enters the dryer at a rate of 400 kg/min and picks up the water that evaporates from the solids. Humid air leaves the dryer at 50C containing 2.44 wt% water vapor and passes through a condenser in which it is cooled to lOe. The pressure is constant at 1 atm throughout the system. (a) At what rate (kg/min) is water evaporating in the dryer? (b) Use the psychrometric chart to estimate the wet-bulb temperature, relative humidity, dew point. and specific enthalpy of the air leaving the dryer. (c) Use the psychrometric chart to estimate the absolute humidity and specific enthalpy of the air leaving the condenser. (d) Use the results of parts (b) and (c) to calculate the rate of condensation of water (kg/min) and the rate at which heat must be transferred from the condenser (kW). (e) If the dryer operates adiabatically, what can you conclude about the temperature of the entering air? Briefly explain your reasoning. What additional information would you need to calculate this temperature?
Questions & Answers
QUESTION:
Wet solids pass through a continuous dryer. Hot dry air enters the dryer at a rate of 400 kg/min and picks up the water that evaporates from the solids. Humid air leaves the dryer at 50C containing 2.44 wt% water vapor and passes through a condenser in which it is cooled to lOe. The pressure is constant at 1 atm throughout the system. (a) At what rate (kg/min) is water evaporating in the dryer? (b) Use the psychrometric chart to estimate the wet-bulb temperature, relative humidity, dew point. and specific enthalpy of the air leaving the dryer. (c) Use the psychrometric chart to estimate the absolute humidity and specific enthalpy of the air leaving the condenser. (d) Use the results of parts (b) and (c) to calculate the rate of condensation of water (kg/min) and the rate at which heat must be transferred from the condenser (kW). (e) If the dryer operates adiabatically, what can you conclude about the temperature of the entering air? Briefly explain your reasoning. What additional information would you need to calculate this temperature?
ANSWER:Step 1 of 5
The rate at which hot air is entering the dryer
The percentage composition of humid air
Thus the rate of evaporation of water can be calculated as follows:
So 10 kg water evaporates per minute.