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Automation API

Overview

The Wet Cooling Tower can be fully controlled headlessly via the DWSIM Automation API, enabling batch simulations, parametric studies, and automated testing without the DWSIM GUI.

Setup (Python with pythonnet)

import clr
import sys
import os

# Path to DWSIM installation
dwsim_path = r'C:\Users\<username>\AppData\Local\DWSIM'
sys.path.append(dwsim_path)

# Load DWSIM assemblies
clr.AddReference(os.path.join(dwsim_path, 'DWSIM.Automation.dll'))
clr.AddReference(os.path.join(dwsim_path, 'DWSIM.Interfaces.dll'))

from DWSIM.Automation import Automation3

Requirements

  • Python 3.8+ with pythonnet 3.0+: pip install pythonnet
  • A saved DWSIM flowsheet (.dwxmz) with the Cooling Tower already placed

Loading and Running a Flowsheet

# Create automation instance
auto = Automation3()

# Load flowsheet
sim = auto.LoadFlowsheet(r'path\to\CoolingTower.dwxmz')

# Find objects by tag
ct = None
inlet = None
for name, obj in sim.SimulationObjects.items():
    tag = obj.GraphicObject.Tag
    if tag == 'CT-1':
        ct = obj
    elif tag == '1':
        inlet = obj

# Set inlet stream properties
inlet.SetPropertyValue('PROP_MS_0', 313.15)   # Temperature (K)
inlet.SetPropertyValue('PROP_MS_1', 101325.0)  # Pressure (Pa)
inlet.SetPropertyValue('PROP_MS_2', 1.0)       # Mass flow (kg/s)

# Set cooling tower parameters
ct.SetPropertyValue('Calculation Method', 1)        # 1 = Merkel
ct.SetPropertyValue('Calculation Mode', 1)           # 1 = Design
ct.SetPropertyValue('Air Dry-Bulb Temperature', 298.15)
ct.SetPropertyValue('Air Wet-Bulb Temperature', 293.15)
ct.SetPropertyValue('Atmospheric Pressure', 101325.0)
ct.SetPropertyValue('L/G Ratio', 1.0)
ct.SetPropertyValue('Desired Outlet Temperature', 303.15)
ct.SetPropertyValue('Air Pressure Drop', 200.0)
ct.SetPropertyValue('Fan Efficiency', 0.75)

# Run calculation
auto.CalculateFlowsheet2(sim)

# Read results
kavl = float(ct.GetPropertyValue('Calculated KaV/L'))
tw_out = float(ct.GetPropertyValue('Water Outlet Temperature'))
q_rejected = float(ct.GetPropertyValue('Heat Rejected'))

print(f'KaV/L = {kavl:.4f}')
print(f'Tw,out = {tw_out - 273.15:.2f} C')
print(f'Q = {q_rejected/1000:.2f} kW')

Property Names for Get/Set

Inlet Stream (Material Stream)

Property Code Units
Temperature PROP_MS_0 K
Pressure PROP_MS_1 Pa
Mass Flow PROP_MS_2 kg/s

Cooling Tower Properties

Use the exact property names from the Parameters Reference.

ct.SetPropertyValue('Calculation Method', 1)          # 0=Poppe, 1=Merkel
ct.SetPropertyValue('Calculation Mode', 1)             # 0=Rating, 1=Design
ct.SetPropertyValue('Air Dry-Bulb Temperature', 298.15)
ct.SetPropertyValue('Air Wet-Bulb Temperature', 293.15)
ct.SetPropertyValue('Atmospheric Pressure', 101325.0)
ct.SetPropertyValue('L/G Ratio', 1.2)
ct.SetPropertyValue('KaV/L (Merkel Number)', 1.5)
ct.SetPropertyValue('Desired Outlet Temperature', 303.15)

kavl = float(ct.GetPropertyValue('Calculated KaV/L'))
tw_out = float(ct.GetPropertyValue('Water Outlet Temperature'))
q = float(ct.GetPropertyValue('Heat Rejected'))
evap = float(ct.GetPropertyValue('Evaporation Rate'))
t_air_out = float(ct.GetPropertyValue('Air Outlet Temperature'))
w_out = float(ct.GetPropertyValue('Air Outlet Humidity Ratio'))

Parametric Study Example

import numpy as np

results = []
for lg in np.arange(0.5, 2.5, 0.1):
    sim = auto.LoadFlowsheet(r'path\to\CoolingTower.dwxmz')
    # ... find ct and inlet objects ...
    ct.SetPropertyValue('L/G Ratio', lg)
    ct.SetPropertyValue('Calculation Mode', 1)       # Design
    ct.SetPropertyValue('Desired Outlet Temperature', 303.15)
    auto.CalculateFlowsheet2(sim)
    kavl = float(ct.GetPropertyValue('Calculated KaV/L'))
    results.append((lg, kavl))
    print(f'L/G = {lg:.1f} -> KaV/L = {kavl:.4f}')

Batch Efficiency

For large parametric studies, reload the flowsheet for each case to ensure a clean state. The DWSIM Automation API is fast enough for hundreds of cases in minutes.