Heat Capacities: Example Problems
Try to solve these problems before watching the solutions in the screencasts.
Example Problem 1
A mixture of 70.% benzene and 30.% toluene at 150°C and a flow rate of 540 mol/h is fed to a furnace. What is the outlet temperature if 22 MJ/h are added to the mixture? The heat capacity coefficients, which can be used from 273 to 1500 K are in the table.
| Molecule | \(A\) | \(B x 10^2\) | \(C x 10^5\) | \(D x 10^9\) |
| Benzene | -36.193 | 48.444 | -31.548 | 77.753 |
| Toluene | -34.364 | 88.887 | -34.435 | 80.335 |
\(C_P = A + BT + CT^2 +DT^3\)
where \(C_P\) is in J/mol K and \(T\) is in kelvin.
Example Problem 2
An ammonia stream with a flow rate of 100 mol/min is heated from 375 to 750 K. How much heat must be added per min to this stream? Use the temperature-dependent heat capacity
CP,i = Ai + BiT + CiT2 ,
which is applicable from 300 to 1500 K. The constants are below.
| A | B | C |
| 23.619 | 3.75E-02 | 1.38E-06 |