Draft Cooling Tower Analysis Using SOLIDWORKS Flow Simulation (Tracer study)

Introduction:

Objectives

• To evaluate the dispersion behaviour of carbon monoxide (CO) released as a tracer gas.
• To visualize CO distribution using iso surface plots of mass fraction.
• To understand CO dispersion characteristics in airflow using the tracer study method

What is a Tracer Study in the HVAC Module?
The HVAC module includes tools to simulate airflow and pollutant dispersion in HVAC and ventilation systems. A tracer study involves injecting CO as a passive gas tracer to track its concentration and movement in the airflow, helping engineers visualize pollutant spread and identify critical zones within ventilation structures.

Cooling Tower Model & Simulation Setup

Boundary Conditions:

• Inlet air enters the at bottom in cooling tower at a velocity of 2.5 m/s. and formula driven wind velocity in Z direction. Due to the buoyancy driven natural draft considered air velocity is generally considered in cooling tower is 2.5 m/s.
• CO is injected at the base as a tracer gas with a mass flow rate of 0.5 kg/s, using the predefined tracer option available in the HVAC module’s Engineering Database in SOLIDWORKS Flow Simulation.
• Ambient conditions are set to 1 atm pressure and 25°C temperature
• It is common in engineering practice to describe the wind profile with a power-law in non-complex terrain up to a height of about 10 m above ground level. The velocity has been defined in a z direction with a variable wind speed based on the height of the structure.



• V(h) is the wind speed at height h
• Vr is the known wind speed at a reference height hr
• Here the power-law exponent p is considered as 0.25 for noncomplex terrain which is an empirically derived coefficient that varies dependent upon the stability of the atmosphere from about 0.1 to about 0.6.

The larger the power-law exponent the larger the vertical gradient in the wind speed.

• Gravity is enabled to simulate buoyancy-driven natural draft flow within the tower.
• Simulation Type: Steady-state airflow with tracer study using HVAC module.

Results:
Velocity contour plot:

Iso plots of CO dispersion:
These Iso Plots (Iso surfaces) visualizes a various mass fraction of CO. They demonstrate the dispersion of the CO tracer in the cooling tower as it moves though the tower.

Plot 1 Shows Highest Concentration Zones Near the CO injection at the tower base.

Plot 4 shows the Air velocity distribution influence which governs the transport and dilution of CO tracer gas.

These Iso plots (Iso Surfaces) show concentration thresholds reveal how far and wide CO spreads inside the tower structure.

How the HVAC Module Facilitates Tracer Study
Tracer Gas Definition: A CO tracer gas, at is injected at the base of the tower. This utilizes a predefined tracer option found in the HVAC module’s Engineering Database within SOLIDWORKS Flow Simulation.

The SOLDIDWORKS Flow simulation HVAC module provides visualization features such as cut plots and Iso plots (Iso surface) contours for detailed analysis of CO dispersion to interpret the results.

Practical Applications

• Using HVAC module’s tracer study capabilities for Identifying zones with potential hazardous CO buildup inside structure for safety assessments in industrial environments.

Conclusion
Using the Tracer study in SOLIDWORKS Flow Simulation HVAC module to conduct tracer studies provides engineers with a powerful and accessible way to analyse CO dispersion in draft cooling towers. By leveraging tracer gas features combined with gravity effects, it delivers valuable insights into pollutant transport and ventilation design optimization.

Reference
1. Guo, Dong-Peng, et al. “Wind Tunnel Experiment for Predicting a Visible Plume Region from a Nuclear Power Plant Cooling Tower.” Journal of Applied Meteorology and Climatology, vol. 53, no. 2, 2014, pp. 538-549, https://journals.ametsoc.org/view/journals/apme/53/2/jamc-d-13-0153.1.xml

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