One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, the...One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions.展开更多
Since stack effect that occurs in high-rise buildings has an effect on the indoor environment of the buildings, energy loss and smoke control in case of a fire, there is a need to conduct research on this. For an anal...Since stack effect that occurs in high-rise buildings has an effect on the indoor environment of the buildings, energy loss and smoke control in case of a fire, there is a need to conduct research on this. For an analysis of the stack effect, analysis methods on the leakage flow through gap of interior door shall be formulated. Until now, studies related to the gap leakage flow in buildings have mainly analyzed flow field and pressure in the buildings one-dimensionally using pressure difference-leakage flowrate relations of Orifice Equation and a network numerical analysis algorithm that as- sumes each compartment in the buildings as a single point. In this study, the Momentum Loss Model which enables pressure drop to be proportional to the flow velocity through the gap of door in computational domain of 3-dimensional numerical analysis was proposed to reflect the gap flow phenomenon effectively in 3-dimensional numerical analysis. Using the proposed model, 3-dimensional numerical analysis of the stack effect on the stairs in buildings was performed, and the effects of separation door and lobby between stair and accommodation on the stack effect were investigated.展开更多
基金the financial support of the National Natural Science Foundation of China (No. 41121061)the National Basic Research Program (973) of China (Nos. 2012CB026101 and 2011CB013505)+1 种基金the Western Project Program of the Chinese Academy of Sciences (No. KZCX2-XB3-19)the Open Fund of State Key Laboratory of Frozen Soil Engineering (No. SKLFSE201209)
文摘One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions.
文摘Since stack effect that occurs in high-rise buildings has an effect on the indoor environment of the buildings, energy loss and smoke control in case of a fire, there is a need to conduct research on this. For an analysis of the stack effect, analysis methods on the leakage flow through gap of interior door shall be formulated. Until now, studies related to the gap leakage flow in buildings have mainly analyzed flow field and pressure in the buildings one-dimensionally using pressure difference-leakage flowrate relations of Orifice Equation and a network numerical analysis algorithm that as- sumes each compartment in the buildings as a single point. In this study, the Momentum Loss Model which enables pressure drop to be proportional to the flow velocity through the gap of door in computational domain of 3-dimensional numerical analysis was proposed to reflect the gap flow phenomenon effectively in 3-dimensional numerical analysis. Using the proposed model, 3-dimensional numerical analysis of the stack effect on the stairs in buildings was performed, and the effects of separation door and lobby between stair and accommodation on the stack effect were investigated.
