12.57 At steady state, a device

for heating and humidifying air

has 250 ft3/min of air at 40°F, 1

atm, and 80% relative humidity

entering at one location, 1000

ft3/min of air at 60°F, 1 atm,

and 80% relative humidity

entering at another location,

and liquid water injected at

55°F. A single moist air stream

exits at 85°F, 1 atm, and 35%

relative humidity. Using data

from the psychrometric chart,

Fig. A-9E, determine

a. the rate of heat transfer to

the device, in Btu/min.

b. the rate at which liquid

water is injected, in lb/min.

Neglect kinetic and potential

energy effects.