100% relative humidity. Assume a pressure of 1.0 atm (a) Find the rate of extrac
ID: 2996646 • Letter: 1
Question
100% relative humidity. Assume a pressure of 1.0 atm (a) Find the rate of extraction of condensate m Q. 4-24 kg/min cond (b) Find heat extraction rate from the air 0 2) (10% each) 0.50 kg/s of steam at 200oC and 800 kPa enters an open feedwater heater operating at steady state. A separate stream of liquid water enters at 800 kPa and 30oC. At the exit the mixture is saturated liquid at 800 kPa. a Find the enthalpy of the 30C liquid h kJ/kg (t 0.05 kJ/kg) b) Find the mass flow rate at the exit in kg/s. m exit kg/s C+ 0.01 k 3) (10% each) 0.02 kmols of gaseous H2(g), is air at 25°C in an experimental motor. Assume complete combustion and that the exhaust is at 1.0 bar. Find the following: a) Air fuel ratio on a mass basis AF b) The dew point of the exhaust Tp C 0.5 °C) 4) (10% each) Consider a gaseous mixture that is 70% N2 and 30% Co2 by volume Assuming an iden 1Explanation / Answer
3)
H2 + 1/2*(O2+3.76*N2) = H2O + 1.88 N2
Moles of H2 = 0.02 kmols
Since the combustion is completed
Moles of O2 = 0.01 kmoles
Moles of Air = 0.0476 kmoles
Mass of air = 0.0476*28.9*1000 = 1375.64
AF Ratio = Mass of air/100 = 13.76
The exhaust Pressure is 1 bar. The exhaust gas is H2O
Dew point temperature is the saturation temperature at the exhaust pressure
Therefore
The saturation temp at P = 1 bar is
Tsat = 99.62 C
Tdp = 99.62 C
4)
P*V = n*RT
P R and T are constant
V = n*K (Where K = R*T/P)
n = mass/Molecular Wt = m/MW
V = (m/MW)*K -----(1)
Let V be the total volume
Volume of N2 = 0.7*V
Volume of CO2 = 0.3*V
From 1
Mass of N2 = 0.7*V*28/K = 19.6*(V/K)
Mass of CO2 = 0.4*V*44/K = 17.6*(V/K)
Mass fraction of N2 = Mass of N2/(Mass of N2 + Mass of CO2) = 19.6/(19.6 + 17.6)
Mass fraction of N2 = 52.69 %
Mass fraction of CO2 = 47.31 %
R of N2 = 8.314/28 = 0.297 kJ/kg-K
R of CO2 = 8.314/44 = 0.189 kJ/kg-K
Rmix = (mN2*RN2 + mCO2*RCO2)/(mN2 + mCO2)
Rmix = (52.69*0.297 + 47.31*0.189)/100
Rmix = 0.246 kJ/kg-K
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