With the recent boom in the consumer electronics industry, clean rooms are gaining traction as spaces for manufacturing and assembly of these products. Moreover, the pharmaceutical industry has also employed clean room techniques to keep medicines and surgical instruments free from contaminants.
Essentially, a clean room is an artificial environment created by eliminating particulate matter normally present in air viz. micro airborne organisms, dust, water vapour etc.
Being used for scientific applications, a clean room has a controlled level of tainting that is indicated by the quantity of particles per cubic meter at a predetermined molecule measure.
To give further perspective, we may consider that atmospheric air in a regular urban condition contains 35,000,000 particles per cubic meter in the size range 0.5 μm and bigger in measurement, while an ISO 1 clean room permits no particles in that size range and contains just 12 particles per cubic meter of 0.3 μm and smaller. 
The current project involves the aerodynamic analysis of the ventilation process in clean rooms. For better understanding, a comparison is drawn between 3 different clean room configurations.
In addition, ventilation design of multiple clean room configurations are studied to evaluate the spread of contaminant. This is modeled via the Passive Scalar Transport method.
A simulation of the airflow helps us track the particles present in the air as well as the temperature variation across the room.
Taken as the base geometry, the three configurations stem from the cuboid shown below:
The CAD models of the 3 configurations are created and imported onto the Simscale platform.
In the project, they are termed and defined as follows:
Design 1: Central inlets with outlets along the floor
Design 2: Distributed inlets with outlets along the floor
Design 3: Distributed inlets with raised floor outlets
Hex-dominant parametric meshing (only CFD) with 8 computing cores is used for all the three designs under study.
The meshes are generated are shown below. As you may notice, several mesh refinements are run onto the three designs by grouping them into Topological Entity Sets.
Design 1 - Meshed
Design 2 - Meshed
Design 3 - Meshed
Post-meshing, the simulation for each case is set up individually. An steady-state analysis type of Passive Scalar Transport is selected with a Laminar turbulence model. The solver, SIMPLE (Semi-Implicit Method for Pressure Linked Equations) is used as it takes shorter computational time.
Results and Conclusions
After running the three simulation runs, we draw a comparison between the results.
In the image above, we can observe the areas of recirculation for the three designs across the shorter cross section of the room. As the inlets in the Design 1 are centrally located, it provides a large area for recirculation in the corner region of the room.
Design 2 has distributed inlets but the outlets are placed along the floor. This reduces the recirculation upto a certain extent. Although, it is still occurring in the side and middle regions.
Among all the designs under study, Design 3 has the least amount of recirculation due to distributed inlets as well as raised floor outlets.
The following image displays the airflow along the longer cross section of the room. The conclusions shown in the image confirm our choice of Design 3 being the best option; minimizing areas of recirculation.