The formation of multi-steady-states of buoyancy ventilation in underground building

Liu, Yanan; Xiao, Yimin; Augenbroe, Godfried; Zhou, Tiecheng; Hu, Yuxiang; Lin, Jun‐You; Huang, Haiyu

doi:10.1016/j.tust.2018.09.008

Cited by 24 publications

(16 citation statements)

References 46 publications

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“…ese criteria can be used to design buoyancy ventilation or natural exhaust ventilation systems in underground buildings. Compared with the two-zone model in , the results of the proposed four-zone model are more consistent with CFD results in (Liu et al 2018). In addition, the results of proposed four-zone model are more specific and more detailed in the unstable equilibrium point interval.…”

supporting

confidence: 68%

“…Recently, there are some reports on the multiplicity of ventilation solutions of underground structures [34,35]. e study of the multiplicity of solutions for the natural ventilation of underground buildings is different from that of overground buildings.…”

Section: Introductionmentioning

confidence: 99%

“…Because the underground buildings are not exposed to the outdoor environment, it is mainly thermal pressure ventilation (or buoyancy ventilation) rather than wind pressure ventilation which exist in the under structure. Liu et al [34] investigated the formation process of multiple steady states in an underground building with two tunnel connecting to the outdoor environment. e heights of two tunnels are same, and one heat source is located in the corner of the buried space.…”

Section: Introductionmentioning

confidence: 99%

“…By solving the equilibrium points and characteristic roots of the second order differential equation, the solution multiplicity can be determined when the strength ratio of two heat sources and height ratio of two tunnels were changed. However, in the literatures [34,35], the underground structure has only two zones. e deeply burred room and tunnel were treated as one zone, which is just a very simple model.…”

Section: Introductionmentioning

confidence: 99%

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A Four-Zone Model and Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Underground Building

Wang

Wei

2020

Complexity

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The solution multiplicity of natural ventilation in buildings is very important to personnel safety and ventilation design. In this paper, a four-zone model of buoyancy ventilation in typical underground building is proposed. The underground structure is divided to four zones, a differential equation is established in each zone, and therefore, there are four differential equations in the underground structure. By solving and analyzing the equilibrium points and characteristic roots of the differential equations, we analyze the stability of three scenarios and obtain the criterions to determine the stability and existence of solutions for two scenarios. According to these criterions, the multiple steady states of buoyancy ventilation in any four-zone underground buildings for different stack height ratios and the strength ratios of the heat sources can be obtained. These criteria can be used to design buoyancy ventilation or natural exhaust ventilation systems in underground buildings. Compared with the two-zone model in (Liu et al. 2020), the results of the proposed four-zone model are more consistent with CFD results in (Liu et al. 2018). In addition, the results of proposed four-zone model are more specific and more detailed in the unstable equilibrium point interval. We find that the unstable equilibrium point interval is divided into two different subintervals corresponding to the saddle point of index 2 and the saddle focal equilibrium point of index 2, respectively. Finally, the phase portraits and vector field diagrams for the two scenarios are given.

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supporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Four-Zone Model and Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Underground Building

Wang

Wei

2020

Complexity

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“…Yee et al paid particular attention to the separation of different nonlinear behaviors and spurious dynamics caused by some numerical uncertainties observed in actual CFD calculations [40]. Liu et al studied the formation process of multiple steady states of the underground building of two tunnels connected with the outdoor environment [41]. e two tunnels are of the same height, and one of the heat sources is located in a corner of the underground space.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Two Vertically Connected Open Cavities with Unequal Heights

Wang

Wei

2020

Complexity

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Solution multiplicity of natural ventilation in buildings is of much importance for personnel safety and ventilation design. In this paper, a new mathematical model of buoyancy pressure ventilation for two vertically connected open cavities is presented. Compared with the previous published papers studying two vertically connected open cavities with equal heights and hot source E2 < 0 in the upper room, we study two vertically connected open cavities with unequal heights and hot source E2 < 0 or E2 > 0 in the upper room. By solving and analyzing the equilibrium points and characteristic roots of the differential equations, we analyze the stability of two systems with upward flow pattern and downward pattern and obtain the criteria to determine the stability and existence of solutions for two scenarios. According to these criteria, the multiple steady states of buoyancy ventilation in two vertically connected open cavities with unequal heights and variable strength of hot sources can be obtained. These criteria can be used to design buoyancy ventilation or natural exhaust ventilation systems in two vertically connected open cavities. Compared with two stable states of buoyancy ventilation existing in two vertically connected open cavities with equal heights in the previously published papers, we find that more stable states and unstable states of buoyancy ventilation exist in two vertically connected open cavities with unequal heights in our paper. Finally, bifurcation diagrams and the phase portraits for the two scenarios are given.

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Dehumidification in an underground utility tunnel: field experiment and modeling

Zhao

Song³

et al. 2021

Archit. Struct. Constr.

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The recent rapid development of underground utility tunnels (UUT) in China reflects the government's resolve to improve the municipal service amid rapid urbanization. Although safety is of primary concern in the design and operation of the UUT, the moisture issue appears to be neglected. In the southern and eastern China, however, condensation in the UUT is noted and is believed to be responsible for the high rate of equipment failure and the deterioration of air quality inside the tunnel. To understand the moisture issue and its implications to the design and construction of the UUT, this study investigates the moisture balance in a section of the UUT in Suzhou city, eastern China. An experimental dehumidification study was carried out in a 200 m long 4.05 m × 2.5 m cable compartment with the objective to identify major sources and their strengths. Two refrigeration dehumidifiers were used to control the relative humidity. The results show that the most significant moisture source was the outdoor air through ventilation (values dependent on the air change rates), followed by the open water evaporation (~ 4.195 kg/hr) inside the tunnel and the leakage from the neighboring unconditioned compartments. The concrete walls had a strong buffering effect, which was a strong source at the beginning of the dehumidification (~ 17.171 kg/hr). A mathematical model was developed that can predict the tunnel humidity fairly well. The results suggested that the dehumidification needs to be included in the design, construction, and operation of the future utility tunnel. This includes reserved spaces for moisture control systems, an operation strategy for dehumidification, covered drainage system, and quality construction and maintenance.

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The formation of multi-steady-states of buoyancy ventilation in underground building

Cited by 24 publications

References 46 publications

A Four-Zone Model and Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Underground Building

A Four-Zone Model and Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Underground Building

Nonlinear Dynamic Analysis of Solution Multiplicity of Buoyancy Ventilation in Two Vertically Connected Open Cavities with Unequal Heights

Dehumidification in an underground utility tunnel: field experiment and modeling

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