This study developed a 3D numerical model of a ventilation setup inside a Fiberglass Reinforced Plastic (FRP) boat-manufacturing plant, and simulated the flow inside this plant. The study also investigated two alternate ventilation systems, and compared the results with those for the existing ventilation system. Ventilation systems are installed in FRP boat-manufacturing plants to remove harmful contaminants, mainly styrene, emitted during manufacture of boats. Adopting a suitable ventilation system is an inexpensive way of reducing styrene exposure to workers and, hence, is investigated for an existing manufacturing plant.
First, a 2D study of a typical ventilation system is carried out, with the goal to understand the general flow pattern inside the plant. Steady-state results established that styrene accumulates near the ground because it is denser than air, suggesting that a ventilation system should include a ground-level exhaust to remove much of the styrene. A subsequent 3D model of an actual ventilation setup in a manufacturing plant is developed based on data obtained from the National Institute for Occupational Safety and Health (NIOSH). Results from an unsteady simulation showed, again, that styrene, being heavier than air, stayed close to the floor. The average velocity in the working area of the boat was determined to be 0.65 m/s, suggesting little ventilation in the area. Also, after evaporation from the boat surface, styrene was being not forced towards the exhaust vents located downstream. Based on these results, two alternate ventilation systems are investigated. The first one involves ground-level exhausts near the working area to remove much of styrene. The second system involves inlet air blowers placed closer to ground, i.e., at 0.91 meters from the floor, as compared to 3.96 meters in the original system, to push styrene accumulating near the floor, towards the exhaust vents located downstream. Results predict that the first alternate ventilation system reduces styrene concentration by 57% at the breathing level of the workers. However, the ventilation in the working area improves only slightly, with an average velocity of 0.7 m/s. Also, styrene is still not forced to flow towards the exhaust vents as before. Meanwhile, in the second alternate ventilation system, styrene concentration at the breathing level of the workers increases by 1.7%. The air blowers are effective in directing most of the styrene downstream, but this flow is inhibited on its path, due to the formation of a strong re-circulation region near the working area. This causes greater mixing of styrene and air, thus increasing the prevailing styrene concentration. The average velocity in the working area is nearly 0.5 m/s, indicating that the air blowers should be brought closer to the boat to ventilate this region more effectively. The ventilation effectiveness defined as the ratio of styrene concentration at the exhaust vents to the styrene concentration at select indoor points, is compared for all three ventilation systems. It is found to be highest for first alternate ventilation system with an average value of 28.79, as compared to 10.01 and 10.8 for the other two ventilation systems, respectively.
Based on these results, two additional alternate ventilation systems are suggested that can possibly reduce styrene concentrations inside the domain, and provide fresh air near the working area of the boat.