In 2018 Qatar University requested NabtakerEngineering to help them tackle a problem with HVAC thermal comfort as per ASHRAE 55 in one their main Auditoriums. The issue had been raised during summer and when it is fully occupied with 239 people. Investigation for thermal comfort was required to study and fix the problem.
The Goal
NabtakerEngineering planned to investigate the the existing HVAC performance and comply it with Thermal Comfort ASHRAE 55 (PMV/PPD/EDT) Standard by using (CFD) computational fluid dynamics.
The Approach
As a first step, the exiting data (Air Flow, Supply Temperature…etc) had been collected to make sure they meet and comply with design criteria. Then, two different simulations to be conducted. The first one; to simulate the existing situation, and the second one and as per the results of the first simulation, to modify the Return Diffusers Locations (Free Suction) and investigate the HVAC System Performance accordingly.
Limitations
- No Changing in amount of air
- No Changing in cooling load
- No Changing in architectural view (except air outlets locations)
Code To be Used
- SimScale Platform will be used to carry out CFD simulation.
- K-Omega SST turbulence model was be applied.
- Time dependency is steady state as per ASHRAE 55.
Preprocessing
NabtakerEngineering had extended the inlets and outlets to avoid backflow and to help in convergence. The a hex-dominant parametric mesh was selected with multiple types of refinements, resulting in meshes of around 18 million elements.
Results
After conducting two simulation processes and comparing them to each other, it was clear that the results had been modified in some areas and others are not. When the location of Return Diffusers had been changed away from Supply Diffusers, there was some modification. Regarding to the thermal comfort Indices (PDD, PMV and EDT), there were some modifications but in some level of the Auditorium there were not.
Recommendation
Our main recommendation to Qatar University Facility Management Team, was to double check the design criteria and the cooling load for the same. Then, another simulation may be conducted to modify the HVAC Performance in the certain levels of the Auditorium that require that.