A wellinsulated heat exchanger uses hot air to heat water Th

A well-insulated heat exchanger uses hot air to heat water. The hot air enters at a mass flow rate of 0.5 kg/s and a temperature of 400 degree C and exists at 200 degree C. The water has a mass flow rate of 0.1 kg/s and enters as a saturated liquid at 15 degree C and exits as saturated mixture at the same pressure as the water inlet. Determine the quality of the water outlet. When evaluating integrals assume approximate analysis with averaged properties

Solution

Mass flow rate of hot air= 0.5kg/s, Mass flow rate of air = 0.1kg/s, inlet temperature water 15oC

Air in let temperature= 400 oC, Out let temperature = 200 oC

mCp(t1-t2)air=mCp(t1-t2) water

0.5 X 1.063 kj/kg K x ((400+273 )-(200+273))= 0.1 x 4.192 kj/kg K x ( t1 - (15+273))

t1 out temperature of water vapour = 504.0 K =231 oC

Water will covert to steam, Saturated state.