Simulation Study on Indoor Air Distribution and Indoor Humidity Distribution of Three Ventilation Patterns Using Computational Fluid Dynamics
Abstract
:1. Introduction
2. Methods
- We ignored the influence of the gravity field on air and water vapor.
- Both air and water vapor were considered incompressible fluids with a constant density.
- We assumed that when steam evaporates from the water surface, only latent heat exchange is performed—sensible heat exchange was not considered.
- The heat release of the phase transition process when water vapor condenses on the wall was ignored.
- The moisture absorption capacity of the wall was not considered during the condensation on the wall.
3. Post-Processing and Analysis of Simulation Results
3.1. Velocity Field Analysis (Air Flow Analysis)
3.2. Humidity Analysis
3.3. Mean Age of Air Analysis
4. Conclusions
- The model realistically simulated the effect of ventilation on condensation distribution. The ventilation method used affects the distribution of condensation on wall surfaces, so the wall condensation can be effectively controlled by properly arranging the position of the outlets.
- For buildings affected by moisture sources, ventilation with a lower supply and upper back mode is better than other methods. The Case 3 ventilation configuration provided better air flow in the room and a better air replacement rate, which prevented condensation from occurring inside the room.
- It can be inferred that when a wall of the ventilated room has insulation installed, ensuring the material has good heat insulation and moisture resistance properties can also reduce the occurrence of condensation.
- The conclusions of this paper are based on small rooms, and it remains to be seen whether similar conclusions can be drawn for other buildings, for example, with split-level air conditioning in tall spaces.
- For a split-type air-conditioned room, airflow organization distribution—the installation position of the air conditioner, indoor equipment placement and indoor personnel distribution—will affect velocity and temperature fields.
- For office buildings, which are now mostly controlled by central air conditioning, the VRV (Variable Refrigerant Volume) plus fresh-air-conditioning system and primary-return air-conditioning system are also worth discussing with regard to the distribution of indoor temperature and humidity, as well as indoor air quality.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Boundary | Parameter Setting |
---|---|
Air supply | Air volume: 216 /h; temperature: 29 °C; relative humidity (RH): 40% |
Air outlet | Outflow |
Wall | Dehumidification, overall heat transfer coefficient 1.86 W/m2 K. Outdoor temperature: 5 °C |
Initial environment | Temperature: 22 °C, RH: 60% |
Humidifier | Capacity: 300 mL/h, air 0.008 g/s, water 0.05 g/s |
Ceiling and Floor | Insulation |
Case Number | Outlet Arrangement | Ventilation Volume (m3/h) | Air Supply Parameter | Humidity (g/s) | |
---|---|---|---|---|---|
Temperature °C | Humidity % | ||||
1 | Upper supply and mode | 216 | 29 | 40 | 0.05 |
2 | Upper supply and lower back mode | 216 | 29 | 40 | 0.05 |
3 | Lower supply and upper back mode | 216 | 29 | 40 | 0.05 |
4 | Lower supply and upper back mode | 216 | 29 | 60 | 0.08 |
Turbulence Model | Variables | Pressure | Temp | Momentum | Velocity | Water Vapor | Body Force |
---|---|---|---|---|---|---|---|
Standard K-epsilon equation | Discretization Schemes | Second-order upwind | Second-order upwind | Second-order upwind | Second-order upwind | Second-order upwind | Second-order upwind |
Convergence criterion | Relaxation factor | 0.7 | 1.0 | 0.3 | 1.0 | 0.1 | 0.1 |
Flow 0.001 Energy 0.0000001 | Solver schemes | Pressure AMG | Temp AMP | Momentum AMP | Kinetic energy | Kinetic energy dissipation rating | Water vapor |
Circulation type | V | Flex | Flex | Flex | Flex | Flex |
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Zhang, F.; Ryu, Y. Simulation Study on Indoor Air Distribution and Indoor Humidity Distribution of Three Ventilation Patterns Using Computational Fluid Dynamics. Sustainability 2021, 13, 3630. https://doi.org/10.3390/su13073630
Zhang F, Ryu Y. Simulation Study on Indoor Air Distribution and Indoor Humidity Distribution of Three Ventilation Patterns Using Computational Fluid Dynamics. Sustainability. 2021; 13(7):3630. https://doi.org/10.3390/su13073630
Chicago/Turabian StyleZhang, Fangyuan, and Yuji Ryu. 2021. "Simulation Study on Indoor Air Distribution and Indoor Humidity Distribution of Three Ventilation Patterns Using Computational Fluid Dynamics" Sustainability 13, no. 7: 3630. https://doi.org/10.3390/su13073630