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How to Confirm the Performance of Car park Ventilation System by Using CFD..?

Developing a ventilation system and confirming the air quality and ensuring the efficient removal of high contaminant concentrations in a Car Park is one the main tasks that any Engineering Design Office have to conduct.

Qatar Design Consortium (QDC) had carried out to design the new DPS School in Qatar. With almost 7,700 sqm car park, a main mission was to verify the performance of the mechanical ventilation system in case of fire, as it a mandatory requirement for Qatar Civil Defense Department (QCDD) for the any Car Park Ventilation System by Jet Fans.

NabtakerEngineering Carried it Out To Get QCDD Approval

NabtakerEngineering had been retained by QDC to conduct a CFD Simulation for the car park. It has a success percentage with 100% to take the approval form the 1st revision.

The Objective

The objective of this project was to check and confirm the performance of Mechanical Ventilation System; if the smoke produced by fire is evacuated within 30 mins by using CFD analysis as per QCDD Requirements. The acceptance results must be met with Qatar Civil Defence Department within 20 mins.

2 Scenarios are Required

  • First Scenario; in case the fire is happened in the LEFT SIDE of the car park, fans in the left side will be acted as exhaust points.
  • Second Scenario; in case the fire is happened in the RIGHT SIDE, fans in the right side will be acted as exhaust points.

Modeling Approach

  • Fire Dynamic Simulator Tool (FDS) is used to carry out CFD simulation.
  • Large Eddy Simulation (LES) turbulence model is used.
  • Mass and Species Transport model is used to model the smoke propagation.
  • Discrete Ordinates Model to model radiation.
  • Combustion and radiation are introduced into the governing equations via the source
  • Terms in the energy transport equation.

Fire Design:

Fire Details

(2m X 5m) Fire Block burns at 4 MW. The time necessary to reach a 4 MW is set to be as fast with respect to NFPA 204.

Fire Location

The fire location is proposed to be the onerous as per QCDD Requirements. The proposed fire location will be in the center of the car park as it will be onerous to exhaust fans in both scenarios.

Fire Scenario

In both simulation scenarios process is designed to act as per the following:

  • Time = 0 Sec (0 mins): The smoke is generated by 4 MW and Fresh air from Fresh Air Fans is introduced into the car park. Main Exhaust Fans will operate at high speed and will provide an air change rate of 10 ACH.
  • Time = 120 Sec (2 mins): With time delay of 120 Seconds all jet fans will be run at high speed.
  • Time = 1800 Sec (30 mins): The computation is stopped after physical 30 minutes of simulation time.

10 Days to Get Results ONLY..!

After 10 days, two separate simulations had been conducted. It was noticed that jet fans play an important role in driving and orienting the smoke to the exhaust louvers. They also reduce the ability to find a considered dead zone. Moreover, the visibility was 10 meters in the same mentioned area, which give a clear sign that it will be a safe path for occupants to be evacuated through it and for fire brigade to get access at any time to the car park. All. The visibility was also above the tenability criteria at 1.8 m in upstream area within 20 mins.

#CFD #Qatar #Carpark #ventilation #QCDD

Thermal Comfort Investigation in Qatar University’s Auditorium

In 2018 Qatar University requested NabtakerEngineering to help them tackle a problem with thermal comfort 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 Standards by using (CFD) computational fluid dynamics.

The Approach

As 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

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.

#CFD #NabtakerEngineering #ASHRAE55

When We Started NabtrakerEngineering..!

Starting a new thing and change something you used to do is not an easy decision. But also the idea that you have your own business and control your life from A to Z was something really attractive.

When I decided to start my business I thought couple of times about what will happen. Usually, people will tell you beautiful stories and all the happiness that succeed people have. But nobody will tell you about falls, long nights and disappointments.

NabtakerEnginnering is not my first project, but it is my first real business project. I’m a Mechanical Engineer, I spent more than ten years as an employee for two companies. During that I got improved and promoted to be a Construction Manager with a good paid salary.

By end of 2017 I got an a notice of termination due to company down sizing. I was not surprised, cause I got a clue about that six months before. Which is really helped me to start planing to move. Unfortunately or fortunately, they took the advantage and end the contract.!!

In anyway, I had at least an idea and a plan for what I must do. I speed up my efforts to move on, and at the same time I was applying for jobs here and there in the same field. Again, unfortunately or fortunately I did not get an attractive job offer, what forced me to continue in the way to have my own business.

I read a lot about startups and the difficulties you will face, strategies and tactics you should do. But let me tell you something, all that was totally different of what I’ve actually faced.

In your way to build a company and almost at every single stage, there will be all kind of blocks in your way that will let you think to stop and go away. But what will let you stick in, is a kind of ability that you have been built through the trip. It is built from the accumulative efforts through days and nights you spent. Basically, persistence is the secret. It is like a fuel. If you don’t have it you will not reach at all.

I liked “The Founder” the movie that talks about the biography of the creation of the McDonald’s fast food chain. “Ray Kroc” was not the actual founder, but he was the man that introduced McDonald’s to the whole world. He inspired me a lot when he mentioned a special quote says: ” Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent”.

But always keep in your mind, persistence will not come from watching movies or reading and collecting quotes. It comes from experience.

I’m still in the beginning, I can not say I really succeed or failed. But I will try to keep you always up to date. Meanwhile, I will do my best to be persistent and patient as much as I can.

#NabtakerEnginnering #CFD