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Today, people spend almost 90% of their lives indoors. Heating, ventilation, and air conditioning systems determine the temperature within the building. They must be designed to accommodate the comfort of the occupants and other elements within the structure like computer systems and servers.
The air within the building must be circulated well using the HVAC systems. Poorly ventilated rooms with reduced air circulation rates can also lead to physiological stresses, discomfort, and even Sick Building Syndrome (SBS), where occupants experience acute health and comfort effects due to their time spent within the building. In addition, bad indoor temperatures can also affect mental well-being and affect the overall performance and quality of life within the building.
Other elements like computer systems and server units produce a lot of heat that must be countered with good HVAC systems to balance the temperature conditions of the building to benefit the occupants.
This article explores the role of CFD in thermal comfort.
The International Standard EN ISO 7730 defines thermal comfort as “the condition of mind which expresses satisfaction with the thermal environment.” Thus, the person neither feels too hot or cold and can function productively with a healthy mind and body.
Thermal comfort is essential for office spaces, restaurants, public facilities like airports, stations, theatres, libraries, classrooms, malls, shopping spaces, and other conditioned occupied spaces.
This thermal comfort is affected by factors like the following:
The ratio between the current amount of vapor in the air and the maximum amount of water or vapor that air can hold at that temperature is expressed as a percentage to calculate Thermal Comfort.
The contact velocity of air measured in m/s
The contact temperature of the air is measured using the dry-bulb temperature (DBT).
This is generally expressed as mean radiant temperature (MRT). This is an average of the temperature of the surfaces surrounding a person or any intense mono-directional radiation like solar radiation. It is simply referred to as the temperature surrounding a person.
A person’s metabolic rate affects the heat generated. For example, a relatively still person is cooler than one who is moving more than the former.
Clothing insulation prevents a person from exchanging his body heat with the surrounding air and surfaces.
To get this right, engineers, architects, and building planners use sophisticated tools like CFD Analysis and other techniques and methods to identify optimal temperature ranges that must be maintained within the building.
These values are obtained after considering various factors, including the occupants’ mindset about the optimal temperature conditions and their preferences, surrounding conditions, and nuances of the environment, size of the building, placing of the windows, number of people, various electronics, etc.
Thermal Comfort is more of a personal experience and differs from person to person. Therefore, this cannot be quantified and expressed as simple degrees. But, reasonable comfort can be created when a minimum of 80% of indoor occupants are feeling comfortable with the thermal environment.
One of the most effective ways to find thermal comfort is using the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD).
A large group of people is assessed using a sensational scale to predict the mean value of the thermal sensation votes. Then, using CFD, values like air velocity, temperature, humidity, etc., can be determined. Finally, the PMV is calculated based on those values using the PMV formula for specific conditions defined by ISO 3370.
From the PMV value, a quantifiable value of the number of dissatisfied people can be obtained.
PPD = 100 – 0.95 x exp (-0.03353 x PMV4 – 0.22179 x PMV2)
CFD Analysis can simulate optimal thermal conditions and enable engineers, architects, and designers to come up with the best thermal solutions for the building.
Inlet and outlet vanes sizes and positions can be estimated using CFD Analysis to optimize and minimize costs and energy.
CFD Analysis software developed by Mechartes can also be used for preliminary virtual testing of ventilation systems like fans, windows, or the building design itself to visualize airflow and predict performance.
Using CFD, airflow dynamics, distribution, and direction can be simulated to help evaluate HVAC systems. These analysis solutions can help remove stale air and infusion of fresh air, the heat produced by insulation in walls, electronic devices, and windows/doors exposed to the outdoor environment.
Multiple factors can influence thermal Comfort, and if not done right, it can significantly distress the occupants. It may also lead to other hazards about heat accumulation, including damage to electronic devices, not to mention its effect on the health and mental well-being of the occupants.
When it comes to thermal comfort, care and precision are needed to develop the best solution. CFD Analysis by Simulation Experts can help you examine the existing conditions and determine the best-suited solutions for your building.
Using Mechartes, engineering consultants who can perform various preliminary virtual simulations can easily estimate the right solution for your building.
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