Optimizing the Return Vent Height for Improved Performance in Stratified Air Distribution Systems
Abstract
:1. Introduction
2. Research Setting and Methodology
2.1. The Theoretical Analysis
2.2. Study Object (Modeled Room)
2.3. The Numerical Model
2.3.1. The Governing Equations
2.3.2. Boundary Conditions
2.4. Ventilation Performance Indices
2.5. Optimization Algorithm: Entropy-Based TOPSIS
3. Validation of Numerical Model and Grid Independence Testing
3.1. Numerical Model Validation
3.2. Grid Independence Testing
4. Results and Discussion
4.1. Optimizing H with Fixed Ts
4.1.1. Temperature Fields
4.1.2. Thermal Comfort Comparison
4.1.3. Comparison of IAQ Performance
4.1.4. The Optimal H
4.2. Optimization Subject to Thermoneutrality Requirement
4.2.1. Achieving Thermoneutrality via Adjusting Ts
4.2.2. Optimal H Given the Requirement That |PMV| Is Less Than 0.5
4.3. Limitations
5. Conclusions
- (a)
- A theoretical analysis demonstrated that the amount of energy saved when using a lower vent is smaller than the cost of the vertical temperature gradient for all STRAD systems.
- (b)
- When Ts is 18 °C, the PMV is under −0.5 in most cases except when the H is 0.3 m; that is, the studied enclosure (an office room) is overcooled. The TOPSIS method suggested 1.5–2.3 m as the optimal range.
- (c)
- When Ts is adjusted to achieve a thermal neutral environment, the suggested optimal H is 2.3 m. In this case, the benefits on the MAA and ΔT0.1–1.1 are so large that the costs in terms of the Qcoil value, concentration of CO2, and DR can be ignored.
- (d)
- The optimal case under thermoneutral conditions is preferable with respect to the IAQ, reduced energy consumption, and thermal comfort, compared with those of the optimal H ranging from 1.5 m to 2.3 m at a Ts of 18 °C with a fixed supply temperature. A near-ceiling H is suggested.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Wall Height [m] | Temperature [°C] |
---|---|
0.08 | 22.4 |
0.73 | 23.4 |
1.39 | 24.0 |
2.04 | 24.5 |
2.68 | 24.4 |
Line | 1 | 2 | 3 |
---|---|---|---|
GCIc,m * [%] | 0.1 | 0.7 | 0.2 |
GCIm,f [%] | 0.1 | 0.2 | 0.2 |
H [m] | 0.3 | 0.8 | 1.1 | 1.3 | 1.5 | 2.3 |
---|---|---|---|---|---|---|
Similarity | 0.1758 | 0.4806 | 0.7499 | 0.8065 | 0.8221 | 0.8242 |
Ranking | 6 | 5 | 4 | 3 | 2 | 1 |
H [m] | 0.3 | 0.8 | 1.1 | 1.3 | 1.5 | 2.3 |
---|---|---|---|---|---|---|
Similarity | 0.0028 | 0.5055 | 0.7889 | 0.8837 | 0.9328 | 0.9972 |
Ranking | 6 | 5 | 4 | 3 | 2 | 1 |
Optimal Cases | Average MAA [s] | Qcoil [W] | Average CO2 [ppm] | ΔT0.1–1.1 [°C] | DR [%] | PPD [%] |
---|---|---|---|---|---|---|
Ts = 18 °C, H = 1.5 m | 86.7 | 1264.5 | 863.1 | 0.54 | 9.5 | 72.7 |
Ts = 18 °C, H = 2.3 m | 79.5 | 1393.7 | 949.5 | 0.30 | 10.3 | 78.8 |
|PMV| < 0.5, H = 2.3 m | 81.4 | 1139.9 | 943.2 | 0.30 | 6.2 | 5.2 |
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Qiao, D.; Wu, S.; Zhang, N.; Qin, C. Optimizing the Return Vent Height for Improved Performance in Stratified Air Distribution Systems. Buildings 2024, 14, 1008. https://doi.org/10.3390/buildings14041008
Qiao D, Wu S, Zhang N, Qin C. Optimizing the Return Vent Height for Improved Performance in Stratified Air Distribution Systems. Buildings. 2024; 14(4):1008. https://doi.org/10.3390/buildings14041008
Chicago/Turabian StyleQiao, Danping, Shihai Wu, Nan Zhang, and Chao Qin. 2024. "Optimizing the Return Vent Height for Improved Performance in Stratified Air Distribution Systems" Buildings 14, no. 4: 1008. https://doi.org/10.3390/buildings14041008
APA StyleQiao, D., Wu, S., Zhang, N., & Qin, C. (2024). Optimizing the Return Vent Height for Improved Performance in Stratified Air Distribution Systems. Buildings, 14(4), 1008. https://doi.org/10.3390/buildings14041008