Chapter 8C

8C. The enthalpy and entropy of a two-phase stream by the SRK EOS Back to Main

This page is used to determine the enthalpy and entropy of a two-phase stream by SRK Equation of State Method.

1 Gas

3 Liquid

Q 2 Liquid

Suppose one has a process in which vaporization or condensation is occurring. One simply looks up the enthalpy (h) at each of the points shown in order to complete the balance. For this case, Q = m1h1 + m2h2 - m3h3. The enthalpy of gas is higher than that of liquid to account for latent heat.

The enthalpy at Points (2) and (3) could be found from a liquid enthalpy correlation such as Table 8.1. The vapor enthalpy at Point (1) would be found from a gas enthalpy correlation at the pressure of the process.

In solving a vaporization and condensation problem (or any problem involving multiple streams) remember that mass in equals mass out and energy in equals energy out, if there is no mass accumulation in the system in question. For our system above

m1 + m2 = m3 m1h1 + m2 h2 = m3 h3 + Q

Once the mass balance has been completed and values of "h" found the heat load "Q" can be calculated.

Where: m = mass

h = enthalpy

Q = heat transfer

Discuss temperature and pressure.

To carry out the entropy and enthalpy calculation the Temperature, Pressure, and Mole % of each component in the mixture must be entered into the appropriate entry space. To do so use the mouse to click the courser in the entry space and input the data.

Once Temperature, Pressure and mole % of each component in the mixture has been entered, select Run to execute the solution.

To convert unit values of data, please refer to “Set Auto Convert and Unit Conversion” in the main page.

Entropy is a thermodynamic property associated with the number of different, equivalent energy states or spatial arrangements in which a system may be found. Spontaneity is associated with an increase in the randomness or disorder of a system. The disorder is expressed by this thermodynamic quantity, given the symbol S. The more disordered a system, the larger its entropy.

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