Air is heated in a duct as it flows over resistance wires. Consider a 20 kW electric heating system. Air enters the heating section at 100 kPa and 15oC with a volume flow rate of 140 m3/min. If heat is lost from air in the duct to the surroundings at a rate of 150 W, determine
(a) The exit temperature of air.
(b) The energetic efficiency. Use the PG model for air and neglect the power consumed by the fan.
(c) Draw an energy flow diagram for the system.