In this work, we present numerical modelling of coupled heat and mass transfer within porous materials. Our study focuses on cinder block bricks generally used in building construction. The material is assumed to be p...In this work, we present numerical modelling of coupled heat and mass transfer within porous materials. Our study focuses on cinder block bricks generally used in building construction. The material is assumed to be placed in air. Moisture content and temperature have been chosen as the main transfer drivers and the equations governing these transfer drivers are based on the Luikov model. These equations are solved by an implicit finite difference scheme. A Fortran code associated with the Thomas algorithm was used to solve the equations. The results show that heat and mass transfer depend on the temperature of the air in contact with the material. As this air temperature rises, the temperature within the material increases, and more rapidly at the material surface. Also, thermal conductivity plays a very important role in the thermal conduction of building materials and influences heat and mass transfer in these materials. Materials with higher thermal conductivity diffuse more heat.展开更多
To investigate the impact of building heat transfer on roof snow loads,roof snow loads and snow load thermal coefficients from 61 Chinese sites over a period of 50 years are simulated based on basic meteorological dat...To investigate the impact of building heat transfer on roof snow loads,roof snow loads and snow load thermal coefficients from 61 Chinese sites over a period of 50 years are simulated based on basic meteorological data such as temperature,humidity,wind speed,and precipitation,and a multi-layer snowmelt model considering the building heat transfer.Firstly,the accuracy of the multi-layer snowmelt model is validated using the data of observed ground snow load and roof snow melting tests.The relationship between meteorological conditions,snow cover characteristics,and thermal coefficients of snow loads in three representative sites is then studied.Furthermore,the characteristics of thermal coefficients in each zone are analyzed by combining them with the statistical results of meteorological data from 1960 to 2010,and the equations of thermal coefficients in different zones on indoor temperatures and roof heat transfer coefficients are fitted separately.Finally,the equations in this paper are compared with the thermal coefficients in the main snow load codes.The results indicate that the snowmelt model using basic meteorological data can effectively provide samples of roof snow loads.In the cold zone where the snow cover lasts for a long time and does not melt easily,the thermal coefficients of the snow loads on the heating buildings are lower than those in the warm zone due to the long-term influence of the heat from inside the buildings.Thermal coefficients are negatively correlated with indoor temperatures and roof heat transfer coefficients.When the indoor temperature is too low or the roof insulation is good,the roof snow load may exceed the ground snow load.The thermal coefficients for heated buildings in the main snow load codes are more conservative than those calculated in this paper,and the thermal coefficients for buildings with lower indoor temperatures tend to be smaller.展开更多
BT(Build and Transfer)模式作为一种新型的有利于吸引民间资本和国外资本的投融资模式,在我国日益受到重视。由于BT模式运作的复杂性,项目发起人必须加强投资控制,对回购基价实施有效管理。研究选择影响回购基价的因素之一即工期延误,...BT(Build and Transfer)模式作为一种新型的有利于吸引民间资本和国外资本的投融资模式,在我国日益受到重视。由于BT模式运作的复杂性,项目发起人必须加强投资控制,对回购基价实施有效管理。研究选择影响回购基价的因素之一即工期延误,探讨其对回购基价的影响机理;通过算例计算可原谅的工期延误引起的项目回购基价增加值,验证其影响的机理及因素;最后提出可原谅工期延误造成回购基价增加的防范措施。研究结果表明:项目回购基价增加的根源在于工期延长而造成的建设期资金成本的增加,增加额的影响因素包括可原谅工期延误事件发生的时点、造成总工期延误的时间、已投入工程的资金数额、约定的融资费用计算规则。防范工期延误造成的回购基价增加,关键在于理清工期延误的责任归属;BT合同条款的限定、工程建设过程中对工期延误事件的及时分析、处理和计算是控制项目回购基价的有效途径。展开更多
文摘In this work, we present numerical modelling of coupled heat and mass transfer within porous materials. Our study focuses on cinder block bricks generally used in building construction. The material is assumed to be placed in air. Moisture content and temperature have been chosen as the main transfer drivers and the equations governing these transfer drivers are based on the Luikov model. These equations are solved by an implicit finite difference scheme. A Fortran code associated with the Thomas algorithm was used to solve the equations. The results show that heat and mass transfer depend on the temperature of the air in contact with the material. As this air temperature rises, the temperature within the material increases, and more rapidly at the material surface. Also, thermal conductivity plays a very important role in the thermal conduction of building materials and influences heat and mass transfer in these materials. Materials with higher thermal conductivity diffuse more heat.
基金the National Natural Science Foundation of China(52078380)。
文摘To investigate the impact of building heat transfer on roof snow loads,roof snow loads and snow load thermal coefficients from 61 Chinese sites over a period of 50 years are simulated based on basic meteorological data such as temperature,humidity,wind speed,and precipitation,and a multi-layer snowmelt model considering the building heat transfer.Firstly,the accuracy of the multi-layer snowmelt model is validated using the data of observed ground snow load and roof snow melting tests.The relationship between meteorological conditions,snow cover characteristics,and thermal coefficients of snow loads in three representative sites is then studied.Furthermore,the characteristics of thermal coefficients in each zone are analyzed by combining them with the statistical results of meteorological data from 1960 to 2010,and the equations of thermal coefficients in different zones on indoor temperatures and roof heat transfer coefficients are fitted separately.Finally,the equations in this paper are compared with the thermal coefficients in the main snow load codes.The results indicate that the snowmelt model using basic meteorological data can effectively provide samples of roof snow loads.In the cold zone where the snow cover lasts for a long time and does not melt easily,the thermal coefficients of the snow loads on the heating buildings are lower than those in the warm zone due to the long-term influence of the heat from inside the buildings.Thermal coefficients are negatively correlated with indoor temperatures and roof heat transfer coefficients.When the indoor temperature is too low or the roof insulation is good,the roof snow load may exceed the ground snow load.The thermal coefficients for heated buildings in the main snow load codes are more conservative than those calculated in this paper,and the thermal coefficients for buildings with lower indoor temperatures tend to be smaller.
文摘BT(Build and Transfer)模式作为一种新型的有利于吸引民间资本和国外资本的投融资模式,在我国日益受到重视。由于BT模式运作的复杂性,项目发起人必须加强投资控制,对回购基价实施有效管理。研究选择影响回购基价的因素之一即工期延误,探讨其对回购基价的影响机理;通过算例计算可原谅的工期延误引起的项目回购基价增加值,验证其影响的机理及因素;最后提出可原谅工期延误造成回购基价增加的防范措施。研究结果表明:项目回购基价增加的根源在于工期延长而造成的建设期资金成本的增加,增加额的影响因素包括可原谅工期延误事件发生的时点、造成总工期延误的时间、已投入工程的资金数额、约定的融资费用计算规则。防范工期延误造成的回购基价增加,关键在于理清工期延误的责任归属;BT合同条款的限定、工程建设过程中对工期延误事件的及时分析、处理和计算是控制项目回购基价的有效途径。
