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. 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.