At what rate must heat be supplied to 15.0 kg\'s of air, if the temperature is i

Question

At what rate must heat be supplied to 15.0 kg's of air, if the temperature is increased from 50.0'C to 150°C? a) Calculate the rate that heat must be supplied by integrating the heat capacity formula for air Number 1534.965 k W b) Calculate the rate that heat must be supplied using the specific enthalpy table of gases located in your text by following the steps below. What is the specific enthalpy of air at 50.0?, if the reference state is pret the specific enthalpy table of gases in your text for this calculation. 1 atm, and Tre-25d? Use Incorrect. Confirm in the specific enthalpy table for gases in the back of your text book that for air, the specific enthalpy at 25 C is 0 kJ/mol and that at 100°C is 2.19 kJ/mol. Use linear interpolation to find the specific enthalpy at 500C. Number 19.3744 kJ/ mol What is the specific enthalpy of air at 150 C if the reference state is prof-1 atm, and Tref-25? Use the specific enthalpy table of gases in your text for this calculation. Number 426.763 k.J/ mol Scroll down for more questions Calculate the rate that heat must be supplied to 15.0 kg/s or air. -O Previous Give Up & View Solution # Try Again O Next Exit-

Explanation / Answer

Using Linear interpolation,

No.X(°C) Y (kJ/mol)

1. 25 0

2. 50 y

3. 100 2.19

(X3-X2)/(X2-X1) = (Y3-Y2)/(Y2-Y1)

Y2 is unknow, put the values of the known variables we get

Specifc enthalpy of air at 50°C = 0.73 kJ/mol

Using Linear extrapolation,

Y(x) = Y1 + ((X-X1)*(Y2-Y1)/(X2-X1))

No. X(°C) Y (kJ/mol)

1. 50 0.73

2. 100 2.19

3. 150 y

Y(150) = 0.73 + ((150-50)*(2.19-0.73)/(100-50))

Specific enthalpy at 150°C is 3.65 kJ/mol

c) Heat Supplied

mass flowrate of air = 15 kg/s

T1 = 50°C

T2 = 150°C

Specific heat at 50°C = 1.006 kJ/kg K

Specific heat at 150°C = 1.015 kJ/kg K

Average Specific heat = 1.0105 kJ/kg K

Heat = m Cp (T2-T1)

Heat = 1515.75 kW

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