Paper is being dried with recirculating air in a two-stage drying system operating at 1 atm. The air enters the first dryer at 180"F, where the air is adiabatically saturated with moisture. The air is then reheated in a heat exchanger to 174°F before entering the second dryer, where the air is adiabatically humidified to 80% relative humidity. The air is then cooled to 60°F in a second heat exchanger, causing some of the moisture to be condensed. This is followed by a third heater to heat the air to 1 80°F before it returns to the first dryer.
(a) Draw a process-flow diagram of the system and enter all of the given data.
(b) Determine the lb H2O evaporated in each dryer per lb of dry air being circulated.
(c) Determine the lb H2O condensed in the second heat exchanger per lb of dry air circulated.