Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of mul...Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.展开更多
Thermal mass is currently evaluated with ＂admittance＂ which is the ability of the element to exchange heat with the environment and is based on specific heat capacity, thermal conductivity and density. The aim of th...Thermal mass is currently evaluated with ＂admittance＂ which is the ability of the element to exchange heat with the environment and is based on specific heat capacity, thermal conductivity and density. The aim of this study is to evaluate the effect of thermal properties namely, density, specific heat capacity and thermal conductivity on thermal mass. The objective of the study is to carry out laboratory experiments by measuring such thermal properties of concrete mixes with various percentages of GGBS （ground granulated blast furnace slag）, PFA （pulverized fuel ash）, and SF （silica fume） and RCA （recycled coarse aggregates）. The results obtained from these tests would contribute to the evaluation of how such thermal properties influence the thermal admittance and hence the thermal mass performance of sustainable concrete elements in a building system.展开更多
The day/night （diurnal） changes in temperature and solar radiation pose challenges for maintaining human thermal comfort in buildings. Passive and energy-conserving buildings seek to manage the available thermal ene...The day/night （diurnal） changes in temperature and solar radiation pose challenges for maintaining human thermal comfort in buildings. Passive and energy-conserving buildings seek to manage the available thermal energy by lowering peaks and dampening the fluctuations in order to maintain conditions for human comfort. Appropriate use of thermal mass moderates the internal temperatures by averaging diurnal extremes. Thermal mass is one of the powerful tools which architects and designers can use to control temperature. It can be used to optimize the performance of energy-conserving buildings that rely primarily on mechanical heating and cooling strategies. Massive building envelopes-such as masonry, concrete, earth, and insulating concrete forms （ICFs） can be utilized as one of the simplest ways of reducing building heating and cooling loads. This article analyses the role and effectiveness of thermal mass as a strategy for providing indoor thermal comfort for passive solar and energy conserving buildings.展开更多
Building air conditioning systems(ACs)can contribute to the stable operation of power grids by participating in peak load shaving programs,but the participants need a fast and accurate zone temperature prediction mode...Building air conditioning systems(ACs)can contribute to the stable operation of power grids by participating in peak load shaving programs,but the participants need a fast and accurate zone temperature prediction model,e.g.,the detailed room thermal-resistance(RC)model,to improve peak shaving effect and avoid obvious thermal discomfort.However,when applying the detailed room RC model to multi-zone buildings,conventional studies mostly consider the heat transfer among neighboring rooms,which contributes little to the prediction accuracy improvement,but leads to complicated model structure and heavy computation.Thus,a distributed RC model is developed for multi-zone buildings in this study.Compared to conventional models,the proposed model considers the total heat transfer between the building and the air,and ignores the heat transfer among indoor air in neighboring rooms through internal walls with heavy thermal mass,thereby having comparable temperature prediction accuracy,simpler structure,and stronger robustness.Based on the model,the effectiveness of passive pre-cooling strategies in reducing the air conditioning loads during peak periods is investigated.Results indicate that the thermal insulation performance of opaque building envelope is quite important to the flexibility enhancement of air conditioning loads.With an uninsulated building envelope,passive pre-cooling is useless for the peak load shaving.In comparison,well insulated opaque building envelope enables the building thermal mass to be utilized through passive pre-cooling,which leads to the air conditioning loads during peak periods being further reduced by about 12%.展开更多
This paper describes an experimental investigation of the thermal performance of four Australian domestic walling systems(cavity brick,insulated cavity brick,insulated brick veneer and insulated reverse brick veneer)h...This paper describes an experimental investigation of the thermal performance of four Australian domestic walling systems(cavity brick,insulated cavity brick,insulated brick veneer and insulated reverse brick veneer)having various combinations of thermal insulation and of thermal mass location within the wall.This experimental analysis extends further the previous studies of the benefits of thermal mass on the overall thermal performance of building enclosures(Gregory et al.2008,Luo at al.2008,Alashaary et al.2009).The comparison is based on the time required to maintain thermal comfort for free-floating internal conditions.The results clearly show that internal comfort levels are influenced by both the thermal resistance of the walls as well as the extent and location of the thermal mass,with neither parameter being the sole predictor.The best thermal performance is therefore obtained by an appropriate combination of thermal mass and resistance,rather than focussing on the overall wall thermal resistance(R-value)alone.A new approach of density temperature plots for comparison of temperature variation is also used in the assessment of module thermal performance.展开更多
Embodied energy is a measure of the energy used in producing,transporting and assembling the materials for a building.Operational energy is the energy used to moderate the indoor environment to make it functional or c...Embodied energy is a measure of the energy used in producing,transporting and assembling the materials for a building.Operational energy is the energy used to moderate the indoor environment to make it functional or comfortable-primarily,to heat or cool the building.For many building geometries,the walls make the most significant contribution to the embodied energy of the building,and they are also the path of greatest heat loss or gain through the fabric,as they often have a greater surface area than the roof or floor.Adding insulation reduces the heat flow through the wall,reducing the energy used during operation,but this adds to the embodied energy.The operational energy is not only a function of the wall buildup,but also depends on the climate,occupancy pattern,and heating strategy,making an optimisation for minimum overall energy use non-trivial.This study presents a comparison of typical wall construction types and heating strategies in a temperate maritime climate.The transient energy ratio method is a means to abstract the heat flow through the walls(operational energy for heating),allowing assessment of the influence of walls in isolation(i.e.in a general sense,without being restricted to particular building geometries).Three retrofit scenarios for a solid wall are considered.At very low U-values,overall energy use can increase as the embodied energy can exceed the operational energy;current best practice walls coupled with low building lifetimes mean that this point may be reached in the near future.Substantial uncertainty is present in existing embodied energy data,and given its contribution to total energy use,this is a topic of urgent concern.展开更多
The conservation equations for heat conduction are established based on the concept of thermal mass.We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass.The...The conservation equations for heat conduction are established based on the concept of thermal mass.We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass.The general law introduces a damped thermal wave equation.It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected,which indicates that the CV model only considers the temporal inertia of heat flux.Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory.For larger thermal perturbation,however,the physically impossible phenomenon pre-dicted by CV model,i.e.the negative temperature induced by the thermal wave superposition,is eliminated by the general heat conduction law,which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable.展开更多
Global change has become a hot spot in Quaternary geology, and high\|precision, high\|sensitivity dating is also an urgent problem which needs to be solved. This paper presents some achievements in U\|series dating of...Global change has become a hot spot in Quaternary geology, and high\|precision, high\|sensitivity dating is also an urgent problem which needs to be solved. This paper presents some achievements in U\|series dating of marine corals by thermal ionization mass spectrometry (TIMS) and its application to the study of paleo\|environments. Recently, coral samples were determined for their ages on a MAT\|262 mass spectrometer and satisfactory results have been obtained.展开更多
The objective of present work is to study the thermo diffusion effect on an unsteady simultaneous convective heat and mass transfer flow of an incompressible, electrically conducting, heat generating/absorbing fluid a...The objective of present work is to study the thermo diffusion effect on an unsteady simultaneous convective heat and mass transfer flow of an incompressible, electrically conducting, heat generating/absorbing fluid along a semi-infinite moving porous plate embedded in a porous medium with the presence of pressure gradient, thermal radiation field and chemical reaction. It is assumed that the permeable plate is embedded in a uniform porous medium and moves with a constant velocity in the flow direction in the presence of a transverse magnetic field. It is also assumed that the free stream consists of a mean velocity, temperature and concentration over which are super imposed an exponentially varying with time. The equations of continuity, momentum, energy and diffusion, which govern the flow field, are solved by using a regular perturbation method. The behavior of the velocity, temperature, concentration, Skin-friction, rate of heat transfer and rate of mass transfer has been discussed for variations in the physical parameters. An increase in both Pr and R results a decrease in thermal boundary layer thickness. However, concentration decreases as Kr, Sc increase but it increases with an increase in both So and δ.展开更多
The finite element software,MIDAS is used to predict the distribution of temperatures and,analyzes the cracking control methods within a hydrating mass concrete.The temperature control of mass concrete has great signi...The finite element software,MIDAS is used to predict the distribution of temperatures and,analyzes the cracking control methods within a hydrating mass concrete.The temperature control of mass concrete has great significance in assuring the project quality.Adiabatic or semi adiabatic temperature measurement is mostly used for measuring and controlling the temperature fluctuation during construction.The temperature distribution produced by the finite element thermal analysis of the model is used to quantify the maximum allowable internal temperature difference before crack initiation on concrete.This study analyzes the data from one high-rise structure project in Shanghai are used to verify the finite element model developed.Results suggest that reliance on a limiting maximum temperature differential to control cracking in massive concrete applications should be supplemented with a requirement for analysis showing the calculated spatial temperature and stress response to the predicted temperature distribution within the concrete,to ensure that the induced tensile stresses will not exceed the tensile strength of the concrete and so minimize the risk of having thermal cracks at early age.展开更多
Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers (ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea (...Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers (ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea (NYS) is conducted to study temperature variation in the bottom thermal front zone of the NYS Cold Water Mass (NYSCWM) during the summer of 2009. In the flood-ebb tidal cycles, the bottom temperature decreases (increases) during flood (ebb) tides, which are dominated by the tidal-current induced horizontal advection. The ebb tide-induced temperature increase is larger than the flood tide-induced tempera- ture decrease due to seasonal warming. In the spring-neap tidal cycles, the temperature and the vertical temperature structure show notable fortnightly variation from 16 July to 25 August. The bottom temperature increases from neap to spring tides and decreases from spring to neap. The Richardson number demonstrates strengthened vertical mixing during spring tides but enhanced stratifica- tion during neap tides. The spring-neap variation in vertical shear caused by tidal current is the dominant factor that induces the fort- nightly variation in vertical mixing and thus bottom temperature.展开更多
On the basis of the analysis of field thermogeochemical data along abnormal zones of a thermal stream in the Bukhara-Khiva, oil-and-gas region of the Turan (Tegermen, Chagakul, Shimoly Alat, Beshtepa) was succeeded to...On the basis of the analysis of field thermogeochemical data along abnormal zones of a thermal stream in the Bukhara-Khiva, oil-and-gas region of the Turan (Tegermen, Chagakul, Shimoly Alat, Beshtepa) was succeeded to obtain important data on a deep structure of sites. Data of gas-chemical and geothermal observations show about confinedness of abnormal concentration of methane to zones of the increased values of the temperature field the measured values of temperatures (Tegermen Square and others). On geoelectric section mines 2-D of inversion of the MT-field depth of 4000 m are lower, among very high-resistance the chemogenic and carbonate deposits of the Paleozoic is traced the subvertical carrying-out abnormal zone. This zone is identified as the channel of a deep heat and mass transfer with which hydrocarbon (HC) deposits are connected. It is shown that electro-investigation when using a geophysical complex can and has to become “advancing” at exploration by oil and gas.展开更多
文摘Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.
文摘Thermal mass is currently evaluated with ＂admittance＂ which is the ability of the element to exchange heat with the environment and is based on specific heat capacity, thermal conductivity and density. The aim of this study is to evaluate the effect of thermal properties namely, density, specific heat capacity and thermal conductivity on thermal mass. The objective of the study is to carry out laboratory experiments by measuring such thermal properties of concrete mixes with various percentages of GGBS （ground granulated blast furnace slag）, PFA （pulverized fuel ash）, and SF （silica fume） and RCA （recycled coarse aggregates）. The results obtained from these tests would contribute to the evaluation of how such thermal properties influence the thermal admittance and hence the thermal mass performance of sustainable concrete elements in a building system.
文摘The day/night （diurnal） changes in temperature and solar radiation pose challenges for maintaining human thermal comfort in buildings. Passive and energy-conserving buildings seek to manage the available thermal energy by lowering peaks and dampening the fluctuations in order to maintain conditions for human comfort. Appropriate use of thermal mass moderates the internal temperatures by averaging diurnal extremes. Thermal mass is one of the powerful tools which architects and designers can use to control temperature. It can be used to optimize the performance of energy-conserving buildings that rely primarily on mechanical heating and cooling strategies. Massive building envelopes-such as masonry, concrete, earth, and insulating concrete forms （ICFs） can be utilized as one of the simplest ways of reducing building heating and cooling loads. This article analyses the role and effectiveness of thermal mass as a strategy for providing indoor thermal comfort for passive solar and energy conserving buildings.
基金supported by the National Natural Science Foundation of China(Grant No.52078096)the Natural Science Foundation Joint Fund of Liaoning Province(Grant No.2023-MSBA-023)+1 种基金2023 Dalian University of Technology-Cardiff University Cooperation and Exchange Foundation Project,2023 International Exchange Foundation Project of“Co-Creation of Excellence Program”from Dalian University of Technology(Grant No.DUTIO-ZG-202307)the Key Project of DUT for International Students Studying and Researching in China:Innovation and Practice of Talent Cultivation Model in the Field of Smart Buildings for the“Belt and Road"Initiative(Grant No.1103-82120001).
文摘Building air conditioning systems(ACs)can contribute to the stable operation of power grids by participating in peak load shaving programs,but the participants need a fast and accurate zone temperature prediction model,e.g.,the detailed room thermal-resistance(RC)model,to improve peak shaving effect and avoid obvious thermal discomfort.However,when applying the detailed room RC model to multi-zone buildings,conventional studies mostly consider the heat transfer among neighboring rooms,which contributes little to the prediction accuracy improvement,but leads to complicated model structure and heavy computation.Thus,a distributed RC model is developed for multi-zone buildings in this study.Compared to conventional models,the proposed model considers the total heat transfer between the building and the air,and ignores the heat transfer among indoor air in neighboring rooms through internal walls with heavy thermal mass,thereby having comparable temperature prediction accuracy,simpler structure,and stronger robustness.Based on the model,the effectiveness of passive pre-cooling strategies in reducing the air conditioning loads during peak periods is investigated.Results indicate that the thermal insulation performance of opaque building envelope is quite important to the flexibility enhancement of air conditioning loads.With an uninsulated building envelope,passive pre-cooling is useless for the peak load shaving.In comparison,well insulated opaque building envelope enables the building thermal mass to be utilized through passive pre-cooling,which leads to the air conditioning loads during peak periods being further reduced by about 12%.
基金supported by the Australian Research Council(LP 120100064)。
文摘This paper describes an experimental investigation of the thermal performance of four Australian domestic walling systems(cavity brick,insulated cavity brick,insulated brick veneer and insulated reverse brick veneer)having various combinations of thermal insulation and of thermal mass location within the wall.This experimental analysis extends further the previous studies of the benefits of thermal mass on the overall thermal performance of building enclosures(Gregory et al.2008,Luo at al.2008,Alashaary et al.2009).The comparison is based on the time required to maintain thermal comfort for free-floating internal conditions.The results clearly show that internal comfort levels are influenced by both the thermal resistance of the walls as well as the extent and location of the thermal mass,with neither parameter being the sole predictor.The best thermal performance is therefore obtained by an appropriate combination of thermal mass and resistance,rather than focussing on the overall wall thermal resistance(R-value)alone.A new approach of density temperature plots for comparison of temperature variation is also used in the assessment of module thermal performance.
文摘Embodied energy is a measure of the energy used in producing,transporting and assembling the materials for a building.Operational energy is the energy used to moderate the indoor environment to make it functional or comfortable-primarily,to heat or cool the building.For many building geometries,the walls make the most significant contribution to the embodied energy of the building,and they are also the path of greatest heat loss or gain through the fabric,as they often have a greater surface area than the roof or floor.Adding insulation reduces the heat flow through the wall,reducing the energy used during operation,but this adds to the embodied energy.The operational energy is not only a function of the wall buildup,but also depends on the climate,occupancy pattern,and heating strategy,making an optimisation for minimum overall energy use non-trivial.This study presents a comparison of typical wall construction types and heating strategies in a temperate maritime climate.The transient energy ratio method is a means to abstract the heat flow through the walls(operational energy for heating),allowing assessment of the influence of walls in isolation(i.e.in a general sense,without being restricted to particular building geometries).Three retrofit scenarios for a solid wall are considered.At very low U-values,overall energy use can increase as the embodied energy can exceed the operational energy;current best practice walls coupled with low building lifetimes mean that this point may be reached in the near future.Substantial uncertainty is present in existing embodied energy data,and given its contribution to total energy use,this is a topic of urgent concern.
基金Supported by the National Natural Science Foundation of China(Grant No.50606018)
文摘The conservation equations for heat conduction are established based on the concept of thermal mass.We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass.The general law introduces a damped thermal wave equation.It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected,which indicates that the CV model only considers the temporal inertia of heat flux.Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory.For larger thermal perturbation,however,the physically impossible phenomenon pre-dicted by CV model,i.e.the negative temperature induced by the thermal wave superposition,is eliminated by the general heat conduction law,which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable.
文摘Global change has become a hot spot in Quaternary geology, and high\|precision, high\|sensitivity dating is also an urgent problem which needs to be solved. This paper presents some achievements in U\|series dating of marine corals by thermal ionization mass spectrometry (TIMS) and its application to the study of paleo\|environments. Recently, coral samples were determined for their ages on a MAT\|262 mass spectrometer and satisfactory results have been obtained.
文摘The objective of present work is to study the thermo diffusion effect on an unsteady simultaneous convective heat and mass transfer flow of an incompressible, electrically conducting, heat generating/absorbing fluid along a semi-infinite moving porous plate embedded in a porous medium with the presence of pressure gradient, thermal radiation field and chemical reaction. It is assumed that the permeable plate is embedded in a uniform porous medium and moves with a constant velocity in the flow direction in the presence of a transverse magnetic field. It is also assumed that the free stream consists of a mean velocity, temperature and concentration over which are super imposed an exponentially varying with time. The equations of continuity, momentum, energy and diffusion, which govern the flow field, are solved by using a regular perturbation method. The behavior of the velocity, temperature, concentration, Skin-friction, rate of heat transfer and rate of mass transfer has been discussed for variations in the physical parameters. An increase in both Pr and R results a decrease in thermal boundary layer thickness. However, concentration decreases as Kr, Sc increase but it increases with an increase in both So and δ.
文摘The finite element software,MIDAS is used to predict the distribution of temperatures and,analyzes the cracking control methods within a hydrating mass concrete.The temperature control of mass concrete has great significance in assuring the project quality.Adiabatic or semi adiabatic temperature measurement is mostly used for measuring and controlling the temperature fluctuation during construction.The temperature distribution produced by the finite element thermal analysis of the model is used to quantify the maximum allowable internal temperature difference before crack initiation on concrete.This study analyzes the data from one high-rise structure project in Shanghai are used to verify the finite element model developed.Results suggest that reliance on a limiting maximum temperature differential to control cracking in massive concrete applications should be supplemented with a requirement for analysis showing the calculated spatial temperature and stress response to the predicted temperature distribution within the concrete,to ensure that the induced tensile stresses will not exceed the tensile strength of the concrete and so minimize the risk of having thermal cracks at early age.
基金supported by the National Natural Science Foundation of China (Nos. U1706215, 41506012, 41430963 and 41606005)
文摘Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers (ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea (NYS) is conducted to study temperature variation in the bottom thermal front zone of the NYS Cold Water Mass (NYSCWM) during the summer of 2009. In the flood-ebb tidal cycles, the bottom temperature decreases (increases) during flood (ebb) tides, which are dominated by the tidal-current induced horizontal advection. The ebb tide-induced temperature increase is larger than the flood tide-induced tempera- ture decrease due to seasonal warming. In the spring-neap tidal cycles, the temperature and the vertical temperature structure show notable fortnightly variation from 16 July to 25 August. The bottom temperature increases from neap to spring tides and decreases from spring to neap. The Richardson number demonstrates strengthened vertical mixing during spring tides but enhanced stratifica- tion during neap tides. The spring-neap variation in vertical shear caused by tidal current is the dominant factor that induces the fort- nightly variation in vertical mixing and thus bottom temperature.
文摘On the basis of the analysis of field thermogeochemical data along abnormal zones of a thermal stream in the Bukhara-Khiva, oil-and-gas region of the Turan (Tegermen, Chagakul, Shimoly Alat, Beshtepa) was succeeded to obtain important data on a deep structure of sites. Data of gas-chemical and geothermal observations show about confinedness of abnormal concentration of methane to zones of the increased values of the temperature field the measured values of temperatures (Tegermen Square and others). On geoelectric section mines 2-D of inversion of the MT-field depth of 4000 m are lower, among very high-resistance the chemogenic and carbonate deposits of the Paleozoic is traced the subvertical carrying-out abnormal zone. This zone is identified as the channel of a deep heat and mass transfer with which hydrocarbon (HC) deposits are connected. It is shown that electro-investigation when using a geophysical complex can and has to become “advancing” at exploration by oil and gas.
