An exhaust pipe of 75 mm outside diameter is cool by surrounding it by an annular space containing water. The exhaust ga

[answerhappygod]

An exhaust pipe of 75 mm outside diameter is cool by surrounding
it by an annular space
containing water. The exhaust gas enters the exhaust pipe at 3500 C
and the water enters from the
mains at 10°C. The heat transfer coefficients for the gases and
water are 0.3 and 1.5 kW / m2 K,
and the pipe thickness may be taken to be negligible. The gases are
cool to 100 °C and the mean
specific heat capacity at constant pressure is 1.13 kJ/ kg K. The
gas flow rate is 200kg/hr and the
water flow rate is 1400 kg/ h. The specific heat capacity of water
is 4.19 kJ/kg K. calculate:
(i) The required pipe length for parallel-flow;
(ii) The required pipe length for counter-flow.