Winter Is Coming - A sneak peek into the upcoming app for Occupant Thermal Comfort

Wednesday, January 30, 2019 | Comments

Are you a Game of Thrones (GOT) fan? No. Oops... Looks like you need to watch GOT. Anyway, I will dare to say, WINTER IS COMING, and we need to protect the north, we need to prepare to fight against the white walkers. This is the mythical story. Believe me, based on my experience, I feel the same when I enter an air conditioning environment. Unfortunately, one day I got the seat in the theater probably controlled by the white walker. I forgot to take my dragon glass (my winter jacket) and felt too cold. At that time, I thought wouldn't it be nice if John Snow builds a product to fight the white walker. I mean, wouldn't it be nice if we have a product which can help to identify the comfort conditions, evaluate different configurations and suggest the one where no one will have a feel of too cold or too hot - a state known as thermal comfort.

We need an innovative, quick, easy and affordable solution. simulationHub team braced themselves for a lengthy war period. We’ve been heads down working on the same for last six month. We have been developing the project “DRAGON GLASS”. Today we give you a teaser sneak peek at what the project is and how it's going to change the world of designing, evaluating and selecting the HVAC system. This blog will highlight some of the nice features that are in the midst of developing.

But before we dive into the app, let’s brush up on the fundamentals of thermal comfort.

WWW’s of Thermal Comfort

What is Thermal Comfort?

Thermal comfort is an important aspect in representing human satisfaction, which is defined as “the condition of mind which expresses satisfaction with the thermal environment” – ASHRAE. It means that a person feels neither too cold nor too warm.

Why is Thermal Comfort important?

Thermal comfort is important for health and well-being as well as productivity. A lack of thermal comfort causes stress among building occupants. When the environment is too warm, occupants can feel tired; when too cold, they will be restless and distracted.

Where Thermal Comfort plays an important role?

About 90% life of an average individual is spent in the indoor environment. A major portion (40%) of the world’s energy is consumed in buildings. Indoor thermal comfort accounts for 30 to 40% of that energy. Thermal comfort is critical inside office spaces, restaurants, public buildings including airport, station, movie hall, library, classroom, etc.. Therefore, well-designed building ventilation systems must be installed to optimize the use of energy while providing satisfaction to the building occupants, without fail.

What factors contribute to Occupant Thermal Comfort?

Thermal comfort has to do with more than the temperature. Yes, you read it right. Remember the ‘feels like’ temperature data in the weather forecasts.

Feels like temperature data in weather forecast

Feels like temperature data in weather forecast

The environment factors contributing to the thermal comfort includes air temperature, humidity, movement of air, thermal radiation. The personal factors include physical activity and clothing. The occupant physical activity represents the metabolic rate or body heat production level and the clothing represents the insulation.

Environment factors contributing in thermal comfort

Environment factors contributing in thermal comfort

Adding to the complication, thermal comfort can also be a matter of gender, age, health, and perception.

Evaluating Thermal Comfort

Occupant thermal comfort is difficult to analyze because it is as much psychological as it is physiological. ‘Comfort’ is a state of mind or a personal feeling - not a quantifiable metric. Thanks to Prof. Fanger for providing us with the parameters to evaluate occupant comfort - Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD). PMV scale represents the internal energy balance.

Predicted mean vote thermal comfort criteria

Predicted mean vote thermal comfort criteria

Other comfort indices include but not limited to Draft Rating (DR), Effective Draft Temperature (EDT), Air Diffusion Performance Index (ADPI). For more details please read our previous blog : Role of CFD in evaluating occupant thermal comfort.

About the App

Enough said on the fundamentals of thermal comfort, let’s take a sneak peek into the app. Project ‘Dragon Glass’ is an upcoming app from the simulationHub team that assess the occupant thermal comfort in the indoor conditioned environment, using CFD.

Office space thermal comfort design

Office space thermal comfort design

The app provides a web browser-based graphical interface that allows the architects/designers/air-conditioning engineers to

  • Step-1: Select the conditioned spaces of interest
  • Step-2: Load different design configurations - air distribution and ventilation systems
  • Step-3: Set different scenarios - occupant density and weather conditions
  • Step-4: Run multiple CFD simulations on the cloud, for combinations of designs & scenarios
  • Step-5: View comfort indices like PMV, PPD, etc.. to assess occupant thermal comfort
simulationHub's upcoming thermal comfort app

simulationHub's upcoming thermal comfort app

‘Dragon Glass’ application aids HVAC engineers in identifying the possible areas of hot or cold zones at an early stage and helps in improving the design configuration of the air distribution and ventilation systems to achieve the necessary occupant thermal comfort.

Occupant thermal comfort analysis summary view

Occupant thermal comfort analysis summary view

Design Configuration

Design configurations are air distribution and ventilation systems with an arrangement of supply and return air outlets, to produce a specific condition of air within the required space or building. The variation includes different types, number, location of the supply diffusers and return grills.

HVAC thermal comfort supply and return configuration

HVAC thermal comfort supply and return configuration

Scenarios

The tonnage requirement of an HVAC system is normally calculated to provide comfort conditions, for the design heat load - the heat load that exists for the maximum time period in a year. Although the primary interest is to predict the thermal comfort conditions for these design load conditions, it is equally important to check the validity of the HVAC system in both extreme and partial heat loads. This will help us identify if the occupant thermal comfort is being compromised under different heat load conditions or scenarios.

Project ‘Dragon Glass’ allows users to set multiple scenarios by varying the occupant density in the space (Internal load) and outside weather conditions (external load).

Occupant Density

The occupants are the heat sources modeled in the form of manikins in seated/standing positions. A heat flux values as suggested by ASHRAE 55 standards is applied on the surfaces of the mankins. Three levels of occupant density are provided for the user - Full (100%) | Half (50%) | Rare (20%). The user can vary the number of occupancies (manikins) by varying this density.

Occupant density in thermal comfort analysis

Occupant density in thermal comfort analysis

Weather Conditions

The external heat load on the building is applied on the external wall (walls that are in direct exposure to atmosphere) based on the outside weather conditions i.e., wind speed and air temperature. The heat transfer coefficient is calculated accordingly and applied on the external wall surfaces, by the algorithm.

Weather conditions effect on thermal comfort analysis

Weather conditions effect on thermal comfort analysis

CFD Simulations

Once the design configurations and the scenarios are set the user can select the combinations of cases for CFD simulations. Users would love the way the app lists all the combinations of design configurations, scenarios and spaces in one place - Sankey chart. This means you get to view all the possible combinations at one glance, while still being able to easily read through and choose what cases to be submitted for CFD simulations. Just to give you the idea of its scale, here’s a picture of Sankey chart for a sample case, worth examining.

Design configuration and scenarios for thermal comfort analysis

Design configuration and scenarios for thermal comfort analysis

CFD Results

Instead of taking days, weeks, or months the project ‘Dragon Glass’ delivers the results available in minutes. Unlike traditional CFD software that delivers velocity and temperature contour plots, the state of the art post-processing API provides the PMV, PPD, EDT, and DR% data in addition to the velocity and temperature plots.

Thermal comfort cfd analysis results

Thermal comfort cfd analysis results

This lets the user quickly focus on the relevant information, compare different results and identify thermal discomfort (too cold or too hot) zones. Even better, we provide an auto-generated PDF report that summarizes the complete study.

Thermal comfort cfd analysis report

Thermal comfort cfd analysis report

Glimpses of the app

Here is a short video provide the glimpse of the app assessing thermal comfort inside our office space in Pune, India.

Video demonstration of simulationHub's upcoming thermal comfort app

So What’s the Big Deal

Focus on Design : HVAC design engineer or architects don't require specialized CFD knowledge/expertise for using the app in their day-to-day operation. Scalability is another highlight of the app.

Scalability : Remember the sample case we discussed in the Sankey chart with 210 CFD simulations. As the CFD simulations are performed on cloud, you can run multiple simulations i.e., different diffuser positions, occupancy, thermal loads, and weather conditions/seasons, without compromising the speed of output. Depending on the number of simulations, the app manages to scale up or down the cloud capacity to support the fluctuating workloads. This level of scalability and quick results reduces the design time and encourages the design engineer to try new innovative design ideas.

Business Growth : Sales team can access their work (flow animations, comfort plots, hot and cold spots) anywhere via smartphones and tablets — visiting customers in their homes or offices, working in the field or at a plant, etc. This level of agility can give industries using the app, a real advantage over competitors.

Other advantages or benefits include no software installations, no software license or upgrades, no hardware limitations...

Sound interesting? Get connected to us we are interested to collaborate with HVAC equipment manufactures and consultants.

Stay Tuned!!!

And there you have it! I hope you enjoyed this sneak peek of the project ‘Dragon Glass’. We hope you will take it for a spin and share your thoughts in the comments section. It helps drive our understanding and decisions. Please don’t just take our word for it, soon you will be able to try it for yourself.

Rewriting the end of GOT!! We are bringing the app soon to secure the North!!

About Author

Blog Author - Praveen Kumar

Praveen Kumar

Praveen is working as a Technical Manager in the simulationHub department in CCTech. He has more than a 10 years of experience in applying Computational Fluid Dynamics (CFD) as a tool to provide design solutions for various domains like Aerospace, Automobile, Turbomachinery, Process, and Thermal & Fluid equipment design. Praveen holds a Bachelor's degree in Mechanical Engineering and a P.G. Diploma in Advanced Computational Fluid Dynamics (DACFD).

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