Abstract
A validated CFD model is employed to predict the airflow behavior in an impinging jet ventilation (IJV) room with cool, isothermal or warm jets. By using the numerical results, the influences of jet discharge height, supply grille shape and room height on the jet flow behavior as well as the draught discomfort are analyzed for IJV operating in heating scenarios. The results indicate that the warm supply jet of IJV rises upward to the ceiling after spreading along the floor for a certain distance due to thermal buoyancy, resulting in a limited dispersion area, while the cool and isothermal jets of IJV always spread along the whole floor. When IJV is used for space heating, the lower the jet discharge height, the farther the supply air spreads along the floor, and the supply grille shape and room height almost have no effect on the air dispersion area. The results also show that the energy-efficient advantage of IJV in its heating mode compared to the mixing ventilation (MV) system is more remarkable in higher rooms. Moreover, there is a risk of draught discomfort in IJV heating rooms and it is recommended to wear socks to avoid this discomfort.
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Abbreviations
- C µ :
-
empirical constant specified in the turbulence model
- C p :
-
specific heat capacity of air (kJ/(kg·K))
- d h :
-
hydraulic diameter of the jet discharged section
- g i :
-
the ith component of the gravitational acceleration
- h :
-
jet discharge height (m)
- H :
-
room height (m)
- l :
-
length scale (m)
- k :
-
turbulent kinetic energy (J/kg)
- k in :
-
turbulent kinetic energy at the inlet (J/kg)
- \(\bar p\) :
-
mean pressure (Pa)
- PD:
-
percentage dissatisfied (%)
- Pr t :
-
turbulent Prandtl number (dimensionless)
- Re dh :
-
Reynolds number at the inlet (dimensionless)
- S :
-
area of the supply grille (m2)
- T :
-
air temperature (°C)
- \(\bar T\) :
-
mean temperature (°C)
- T cl :
-
mean skin temperature (°C)
- T e :
-
exhaust temperature (°C)
- T r :
-
reference air temperature (°C)
- T s :
-
supply temperature (°C)
- T u :
-
turbulence intensity (dimensionless)
- ΔT :
-
temperature difference between the jet and indoor air (°C)
- u :
-
air velocity (m/s)
- \(\bar u\) :
-
mean air velocity (m/s)
- u′ :
-
fluctuating component of air velocity (m/s)
- U s :
-
supply velocity of the jet (m/s)
- V :
-
dimensionless air velocity
- z :
-
vertical location (m)
- Z :
-
dimensionless vertical location
- β :
-
thermal expansion coefficient of air (K−1)
- δ ij :
-
Kronecker delta
- ε in :
-
turbulent dissipation rate at the inlet (m2/s3)
- λ:
-
air thermal conductivity (W/(m·K))
- ρ :
-
air density (kg/m3)
- ρr :
-
reference air density related to Tr (kg/m3)
- ν :
-
kinematic viscosity of air (m2/s)
- ν t :
-
turbulent eddy viscosity (m2/s)
- θ :
-
dimensionless air temperature
- i and j :
-
three dimensions in the Cartesian coordinate system
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (No. 51278094 and No. 51478098), the Innovation Foundation of Shanghai Education Commission (No. 13ZZ054) and the Natural Science Foundation of Jiangsu Province, China (No. BK20161336).
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Yang, X., Ye, X., Zuo, B. et al. Analysis of the factors influencing the airflow behavior in an impinging jet ventilation room. Build. Simul. 14, 749–762 (2021). https://doi.org/10.1007/s12273-020-0690-6
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DOI: https://doi.org/10.1007/s12273-020-0690-6