20 2 heat and its kinetic energy As temperature of this substance rises from 20°C to 50°C, the substance Heating Curve 80 40 Temperature (C) 20 0 100 200 300 400 500 600 700 Time (sec) -20 absorbs; remains constant absorbs; increases remains constant; increases releases; increases

Air is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. air enters the heat exchanger at 95 kpa and 20°c at a rate of 0.6 m^3/s. the combustion gases (cp = 1.10 kj/kg°c) enter at 160°c at a rate of 0.95 kg/s and leave at 95°c. determine the rate of heat transfer to the air and its outlet temperature.