Vapor Pressure Curves
Comparing vapor pressure correlations for water by sweeping temperature through Antoine, Kirchhoff, and Wagner blocks wired into a PathSim simulation.
The IK-CAPE standard defines several temperature-dependent correlations for vapor pressure. Here we compare three of them:
- Antoine: MATHINLINE0ENDMATH
- Kirchhoff: MATHINLINE1ENDMATH
- Wagner: MATHINLINE2ENDMATH
Each correlation is a Function block with a single temperature input and a single pressure output.
Define the correlation blocks with literature coefficients for water. All use natural logarithm, temperature in Kelvin, and return pressure in Pascals.
Set up a simulation that sweeps temperature from 300 K to 500 K. A Source block generates a linear temperature ramp, which is connected to all three correlations in parallel. A Scope records the three pressure outputs.
18:18:27 - INFO - LOGGING (log: True) 18:18:27 - INFO - BLOCKS (total: 5, dynamic: 0, static: 5, eventful: 0) 18:18:27 - INFO - GRAPH (nodes: 5, edges: 6, alg. depth: 2, loop depth: 0, runtime: 0.064ms) 18:18:27 - INFO - STARTING -> TRANSIENT (Duration: 200.00s) 18:18:27 - INFO - -------------------- 1% | 0.0s<0.0s | 4810.1 it/s 18:18:27 - INFO - ####---------------- 20% | 0.0s<0.0s | 23952.9 it/s 18:18:27 - INFO - ########------------ 40% | 0.0s<0.0s | 23462.4 it/s 18:18:27 - INFO - ############-------- 60% | 0.0s<0.0s | 21625.3 it/s 18:18:27 - INFO - ################---- 80% | 0.0s<0.0s | 22151.7 it/s 18:18:27 - INFO - #################### 100% | 0.0s<--:-- | 23786.6 it/s 18:18:27 - INFO - FINISHED -> TRANSIENT (total steps: 200, successful: 200, runtime: 14.11 ms)
All three correlations agree well in their common validity range. The Wagner equation is typically preferred for high-accuracy work since it is constrained to reach the critical point.