The exhaust gas from a diesel-powered electric generation plant will be used to generate steam in a shell-and-tube heat exchanger with one shell and one tube pass. The steel tubes have a thermal conductivity of 40 W/(m*K), an inner diameter of 50 mm, and a wall thickness of 4 mm. The exhaust gas will flow through the tubes. There are 70 tubes. The total mass flow rate of the gas is 2 kg/s. The exhaust gas will enter the heat exchanger at 400 oC and must leave at 215 oC.
Saturated water at 10 bar will be supplied to the shell side of the heat exchanger.
For steady-state operation, determine
a) the effectiveness and NTU values of the heat exchanger
b) the overall heat transfer coefficient
c) the tube length
The specific heat and density of exhaust gas are 1051 J/(kg K) and 0.588 kg/m3, respectively. Assume that the properties of the exhaust gas can be approximated as those of atmospheric air.
The convection heat transfer coefficient on the tube side is 62 W/(m^2*K). The convection heat transfer coefficient on the shell side is 10,000 W/(m^2*K).
The shell side fouling factor is negligible. The gas (tube) side fouling factor is 0.0015 (m^2*K)/W. Assume negligible heat losses from the heat exchanger to the surroundings.