The structure and characteristics of high-performance lightweight aggregates produced by high-carbon gasification slag were investigated by X-ray diffraction,scanning electron microscopy,thermogravimetry/differential ...The structure and characteristics of high-performance lightweight aggregates produced by high-carbon gasification slag were investigated by X-ray diffraction,scanning electron microscopy,thermogravimetry/differential thermogravimetr,differential scanning calorimetry-Fourier transform infrared,and mercury intrusion porosimetry,respectively.The experimental results show that the ceramsite undergoes two weightless stages in the calcining process.With the increase in the calcining temperature,a large number of pores are formed inside the ceramsite,its structure becomes denser,but the calcining temperature band of the ceramsite becomes narrow.The crystalline phase of the ceramsite changes at different calcining temperatures and the mineral phase changes from the earlieralbite,quartz,oligoclase,hematite,etc,to a silica-aluminum-rich glass phase.The 1130℃ is a more suitable calcining temperature,and the cylinder compressive strength of ceramics is 11.59 MPa,the packing density,apparent density,porosity,and water absorption are 939.11 kg/m^(3),1643.75 kg/m^(3),28.11%,and 10.35%,respectively,which can meet the standards for high-strength lightweight aggregates.展开更多
Pumping ventilation(PV),a special single-sided ventilation(SSV),has been certified as an effective strategy to improve the air exchange rate of SSV.However,most studies targeted on the single space,and few studies hav...Pumping ventilation(PV),a special single-sided ventilation(SSV),has been certified as an effective strategy to improve the air exchange rate of SSV.However,most studies targeted on the single space,and few studies have been focused on the effect of internal partitioning on PV.This paper aims to evaluate the ventilation performance of PV influenced by different configurations of internal partitioning.Computational fluid dynamics(CFD)simulation was used to predict the flow fields and ventilation rates.The width(w/H),height(h/H)and location(d/H)are the three main internal partition parameters considered in this study.The simulation results showed that the total,mean and fluctuating ventilation rates all decrease with wider internal partitions.The normalized total ventilation rate decreases by 7.6%when w/H is increased from 50%to 75%.However,the reduction rate is only 0.23%between w/H=0 and 25%,and only 0.61%between w/H=25%and 50%.The ventilation rate is hardly reduced by increasing the partition width when w/H<50%,whereas greatly reduced by wider partition for w/H>50%.Increasing the partition height will reduce the mean ventilation rate but promote the fluctuating and total ventilation rate in some cases.An increase of total ventilation rate by 1.4%is observed from h/H=50%to 75%.The ventilation rate is larger when the internal partition is attached to the leeward or windward wall.The total,mean and fluctuating ventilation rates for d/H=50%are relatively higher than d/H=0 by 1.5%,3.1%and 0.8%,respectively.Hence the internal partition should be mounted attached to the windward wall so as to obtain the greatest pumping ventilation rate.The periodicity of pumping flow oscillation and pumping frequency are independent of the partition configurations.The peak power of pumping flow is the lowest for the widest internal partition and is negatively affected by the partition height,but it generally has a positive correlation with the distance between the partition and leeward wall.Present research will help to understand pumping ventilation mechanism in real buildings with internal partitioning and provide theoretical basis for developing unsteady natural ventilation technology in low-carbon buildings.展开更多
Photovoltaic(PV)windows have received more and more attention in recent years since their active energy-saving advantages.Considering the surface covered with solar cell modules,the indoor daylight environment of PV w...Photovoltaic(PV)windows have received more and more attention in recent years since their active energy-saving advantages.Considering the surface covered with solar cell modules,the indoor daylight environment of PV windows is obviously different with clear glass windows.However,despite many scholars have studied the indoor daylight environment of PV windows,there few investigations study it from the perspective of human subjective visual perception.In this paper,the indoor daylight environment and human visual comfort of building with Cadmium Telluride Photovoltaic(CdTe-PV)window were investigated.Firstly,the parameters of indoor daylight environment and subjective questionnaires in rooms with CdTe-PV window and clear glass window were analyzed respectively.On the basis of this,combined with indoor working surface illuminance and results of subjective questionnaires,the daylight illuminance threshold of human visual comfort was investigated by the method of Mean Bias Degree(MBD).Finally,an evaluation model for indoor daylight environment of buildings with CdTe-PV window was developed by Fuzzy Comprehensive Evaluation Method.The results showed that the working surface illuminance of CdTe-PV window was lower than that of clear glass room,the CCT of different windows room had a minor gap and the CdTe-PV window room was closer to the recommended range that was 3300-5000K.As for CRI,both the CdTe-PV window room and the clear glass room could meet the visual comfort requirements of office staff.Furthermore,it was found that the requirement of human visual comfort was met when indoor working surface illuminance varies between 500-2200lx in the room with CdTe-PV window.At last,according to the comprehensive evaluation model proposed in this paper,it was found that the indoor daylight environment of buildings with CdTe-PV window was excellent in the present experiment.展开更多
In order to research the sulfate attack resistance of shotcrete, the sulfate attack of shotcrete in the presence and absence of steel fiber was experimentally studied by using dry-wet cycle method. Meanwhile, compared...In order to research the sulfate attack resistance of shotcrete, the sulfate attack of shotcrete in the presence and absence of steel fiber was experimentally studied by using dry-wet cycle method. Meanwhile, compared with ordinary concrete by the same mixture, the difference of sulfate attack resistance of shotcrete was studied. The experimental results showed that, with dry-wet cycles increasing, the changes of loss rate of relative dynamic elastic modulus and mass loss rate of specimens included three stages: initial descent stage, stable stage, and rapid descent stage, respectively. However, the changes of mechanical properties first increased and then decreased. Furthermore, the corrosion products of shotcrete after sulfate attack were observed by using the method of XRD, thermal analysis, and SEM, respectively, and the failure mode of shotcrete turned from ettringite destruction to ettringite-gypsum comprehensive failure. Meanwhile, the contents of ettringite and gypsum increased with increasing dry-wet cycle. Simultaneously, the stratified powders drilled from shotcrete under 150's dry-wet cycle were analyzed for the mineral phase composition and thermal analysis. With the drywet cycle increasing, the content of ettringite first increased and then decreased and tended to stable. However, the determination of gypsum decreased gradually and even to 0 when the depth was more than 12 mm.展开更多
Alkali-activated slag concrete (AASC) is a new green building material. The amount of CO_(2) produced by AASC is 1/5th of that produced by ordinary Portland cement concrete (OPCC). In addition, AASC promotes the reuse...Alkali-activated slag concrete (AASC) is a new green building material. The amount of CO_(2) produced by AASC is 1/5th of that produced by ordinary Portland cement concrete (OPCC). In addition, AASC promotes the reuse of slag and other wastes and saves resources. Furthermore, the scope of use of slag has been expanded. The progress of the research on the hydration characteristics, microstructure, interfacial transition zone, and pore structure of AASC based on the relevant literatures was analyzed and summarized in this study. The influences of the slag composition, the type and dosage of the alkali activator, and the curing conditions on the hydration characteristics and the microstructure of the AASC were discussed. Relatively few research results on the microstructure of AASC are available, and the relevant conclusions are not completely consistent. Moreover, there are many constraints on the development of AASC (e.g., complex composition of raw materials of slag, large shrinkage deformation, and low fluidity). Therefore, further research is required.展开更多
Under the global crisis of energy shortage and environmental pollution,the climate responsive strategies used in vernacular buildings have attracted much attention for their potential to reduce energy consumption and ...Under the global crisis of energy shortage and environmental pollution,the climate responsive strategies used in vernacular buildings have attracted much attention for their potential to reduce energy consumption and carbon emissions.However,the relationships between these traditional climatic strategies were not precisely perceived,which may cause the inapplicability of these strategies for contemporary rural houses.In this paper,taking the Turpan vernacular buildings in arid region of China,the climate responsive strategies of buildings in the most significant periods such as the Gaochang period(before 1318),the Khanate and Republican period(1318–1949),the Modern period(1949–2010),and the Contemporary period(2011–present)were summarized.In addition,two different types of climatic strategies organizations,namely multilayer spaces and integrated building envelopes,were identified based on the temperature difference measurement and comparative analysis.The assessment of thermal performance of the organizations was conducted by the methodology of software simulation.Furthermore,the applicability of the organizations in rural areas was discussed,and a new combined organization was proposed.Consequently,this study can contribute to provide the main approaches for climatically responsive rural houses.展开更多
The available modelling data shortage issue makes it difficult to guarantee the performance of data-driven building energy prediction(BEP)models for both the newly built buildings and existing information-poor buildin...The available modelling data shortage issue makes it difficult to guarantee the performance of data-driven building energy prediction(BEP)models for both the newly built buildings and existing information-poor buildings.Both knowledge transfer learning(KTL)and data incremental learning(DIL)can address the data shortage issue of such buildings.For new building scenarios with continuous data accumulation,the performance of BEP models has not been fully investigated considering the data accumulation dynamics.DIL,which can learn dynamic features from accumulated data adapting to the developing trend of new building time-series data and extend BEP model's knowledge,has been rarely studied.Previous studies have shown that the performance of KTL models trained with fixed data can be further improved in scenarios with dynamically changing data.Hence,this study proposes an improved transfer learning cross-BEP strategy continuously updated using the coarse data incremental(CDI)manner.The hybrid KTL-DIL strategy(LSTM-DANN-CDI)uses domain adversarial neural network(DANN)for KLT and long short-term memory(LSTM)as the Baseline BEP model.Performance evaluation is conducted to systematically qualify the effectiveness and applicability of KTL and improved KTL-DIL.Real-world data from six-type 36 buildings of six types are adopted to evaluate the performance of KTL and KTL-DIL in data-driven BEP tasks considering factors like the model increment time interval,the available target and source building data volumes.Compared with LSTM,results indicate that KTL(LSTM-DANN)and the proposed KTL-DIL(LSTM-DANN-CDI)can significantly improve the BEP performance for new buildings with limited data.Compared with the pure KTL strategy LSTM-DANN,the improved KTL-DIL strategy LSTM-DANN-CDI has better prediction performance with an average performance improvement ratio of 60%.展开更多
In the context of racing to carbon neutrality,the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element,which also provides an opportunity for thermal insulation s...In the context of racing to carbon neutrality,the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element,which also provides an opportunity for thermal insulation solutions to transform from high to zero-carbon attributes.Based on the re-examination of the heat transfer process of conventional pipe-embedded radiant(CPR)walls,the modular pipe-embedded radiant(MPR)wall integrated with thermal diffusive materials is proposed to enhance the heat transfer capacity of CPR walls in the direction parallel to the wall surface,thereby forming a more stable and continuous invisible thermal barrier layer inside the opaque envelopes.A comprehensive thermal and energy-saving analysis study regarding the influence mechanism of several key factors of MPR walls,e.g.,the inclination angle of the filler cavity(θ-value),geometry size of the filler cavity(a:b-value)and thermal conductivity of the filler(λf-value),is conducted based on a validated numerical model.Results show that the dynamic thermal behaviors of MPR walls can be significantly improved due to that the radial thermal resistance in the filler cavity of MPR walls can be reduced by 50%,while the maximum extra exterior surface heat loss caused by the optimization measures is only 2.1%.Besides,a better technical effect can be achieved by setting the major axis of the filler cavity towards the room side,where the interior surface heat load/total injected heat first decreases/increases and then increases/decreases with the increase of theθ-value.In particular,the MPR wall withθL=60°can obtain the best performance when other conditions remain the same.Moreover,the performance indicators of MPR walls can be further improved with the increase of the cavity size(a:b-value),while showing a trend of rapid improvement in theλf-value range of 2–5λC and slow improvement increase in theλf-value range of 5–12λC.In addition,the improvement effect brought by optimizing theθ-value is more obvious as the a:b-value orλf-value increases.展开更多
Building thermal climatic zoning is a key issue in building energy efficiency.Heating degree days(HDD) and cooling degree days(CDD) are often employed as indexes to represent the heating and cooling energy demand in c...Building thermal climatic zoning is a key issue in building energy efficiency.Heating degree days(HDD) and cooling degree days(CDD) are often employed as indexes to represent the heating and cooling energy demand in climatic zoning.However,only using degree days may oversimplify the climatic zoning in regions with complex climatic conditions.In the present study,the application of degree days to current building thermal climatic zoning in China was assessed based on performance simulations.To investigate the key indexes for thermal climatic zoning,the climate characteristics of typical cities were analyzed and the relationships between the climate indexes and heating/cooling demand were obtained.The results reveal that the annual cumulative heating load had a linear correlation with HDD 18 only in regions with small differences in altitude.Therefore,HDD is unsuitable for representing the heating demand in regions with large differences in altitude.A comprehensive index(winter climatic severity index) should be employed instead of HDD,or complementary indexes(daily global solar radiation or altitude) could be used to further divide climate zones.In the current official climatic zoning,the base temperature of 26℃ for CDD is excessively high.The appropriate base temperature range is 18℃ to 22℃.This study provides a reference for selecting indexes to improve thermal climatic zoning in regions with similar climates.展开更多
The energy consumption of a teaching building can be effectively reduced by timetable optimization.However,in most studies that explore methods to reduce building energy consumption by course timetable optimization,se...The energy consumption of a teaching building can be effectively reduced by timetable optimization.However,in most studies that explore methods to reduce building energy consumption by course timetable optimization,self-study activities are not considered.In this study,an MATLAB-EnergyPlus joint simulation model was constructed based on the Building Controls Virtual Test Bed platform to reduce building energy consumption by optimizing the course schedule and opening strategy of self-study rooms in a holistic way.The following results were obtained by taking a university in Xi’an as an example:(1)The energy saving percentages obtained by timetabling optimization during the heating season examination week,heating season non-examination week,cooling season examination week,and cooling season non-examination week are 35%,29.4%,13.4%,and 13.4%,respectively.(2)Regarding the temporal arrangement,most courses are scheduled in the morning during the cooling season and afternoon during the heating season.Regarding the spatial arrangement,most courses are arranged in the central section of the middle floors of the building.(3)During the heating season,the additional building energy consumption incurred by the opening of self-study rooms decreases when duty heating temperature increases.展开更多
Window opening behavior significantly impacts indoor air quality,thermal comfort,and energy consumption.A field measurement was carried out in three typical rooms(a standard office,a meeting room and a smoking office)...Window opening behavior significantly impacts indoor air quality,thermal comfort,and energy consumption.A field measurement was carried out in three typical rooms(a standard office,a meeting room and a smoking office)within an office building.The window state and the physical environment were continuously recorded during the measured periods.Three typical window opening behaviors were found in the measured samples,namely,active,moderate,and passive.The common logistic regression coefficient indicated that solar radiation exhibited the greatest effect on window opening behavior in the smoking office and standard office.Typically,window opening behavior in the meeting room was the most strongly correlated with time of the day,mainly because of the meeting schedule for occupants in the meeting room.This study discussed the dividing principles involved in setting the dummy variable interval level(discretizing continuous variables and dividing them into different intervals),and proposed a method to determine the optimal interval level of each variable.The improved model led to the increase in the prediction accuracy rate of the window being opened by 2.0%and 3.3%according to the comparison with the original model based on dummy variables and the common model based on continuous variables,respectively.This study can provide a reference value for simulating energy consumption in office buildings in the future.展开更多
At present,thermal conductivity is usually taken as a constant value in the calculation of building energy con-sumption and load.However,in the actual use of building materials,they are exposed to the environment with...At present,thermal conductivity is usually taken as a constant value in the calculation of building energy con-sumption and load.However,in the actual use of building materials,they are exposed to the environment with continuously changing temperature and relative humidity.The thermal conductivity of materials will inevitably change with temperature and humidity,leading to deviations in the estimation of energy consumption in the building.Therefore,in this study,variations in the thermal conductivity of eight common building insulation materials(glass wool,rock wool,silica aerogel blanket,expanded polystyrene,extruded polystyrene,phenolic foam,foam ceramic and foam glass)with temperature(in the range of 20-60°C)and relative humidity(in the range of 0-100%)were studied by experimental methods.The results show that the thermal conductivity of these common building insulation materials increased approximately linearly with increasing temperature with maxi-mum growth rates from 3.9 to 22.7%in the examined temperature range.Due to the structural characteristics of materials,the increasing thermal conductivity of different materials varies depending on the relative humidity.The maximum growth rates of thermal conductivity with humidity ranged from 8.2 to 186.7%.In addition,the principles of selection of building insulation materials in different humidity regions were given.The research re-sults of this paper aim to provide basic data for the accurate value of thermal conductivity of building insulation materials and for the calculation of energy consumption.展开更多
Studies on building carbon emissions focus mainly on the materialization phase of life cycle, as carbon emissions in this stage is intensive and high. This paper proposes a simplified model to calculate embodied carbo...Studies on building carbon emissions focus mainly on the materialization phase of life cycle, as carbon emissions in this stage is intensive and high. This paper proposes a simplified model to calculate embodied carbon emissions in building design stage by conducting a process-based inventory analysis of carbon emissions from materials used in 129 residential buildings, 41 office buildings, and 21 commercial buildings during materialization phase. The results indicate that average carbon emissions per unit area from building materials used in residential buildings, office buildings, and commercial buildings are 514.66 kgCO2 e/m2, 533.69 kg CO2 e/m2 and 494.19 kgCO2 e/m2, respectively. Besides, ten kinds of building materials(namely, steel, commercial concrete, wall building materials, mortar, copper core cables, architectural ceramics, PVC pipes, thermal insulation materials, doors and windows, and water paint) constitute 99% of total carbon emissions in all three types of buildings. These materials are major carbon emissions sources in materialization phase. Thus, embodied carbon emissions can be significantly reduced by limiting the amount of these materials in architectural design as well as by using environmental friendly materials.展开更多
Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete ...Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity.展开更多
China’s Tibet autonomous region has abundant solar energy resources,cold winters,and cool summers.These are ideal conditions for the application of passive solar heating methods.However,differences in climatic condit...China’s Tibet autonomous region has abundant solar energy resources,cold winters,and cool summers.These are ideal conditions for the application of passive solar heating methods.However,differences in climatic conditions and building types can significantly affect passive solar technology’s feasibility,which makes it challenging to promote passive solar buildings in Tibet.In this study,the suitability zone for passive solar technology is categorized based on the sub-zoning indicators for Tibet.By modeling between direct gain windows,Trombe walls,and attached sunspaces,the effect of indoor thermal environments and the capacity for heating load reduction is compared for different passive solar technologies.The climate-difference impact analysis shows that the I-B-1 zone is better suited for passive solar technology than other climate zones.More specifically,this zone has an average energy-saving rate difference of up to 28.61%compared to the II-A-1 zone.The analysis of the impact of building type differences indicates that residential buildings have higher Trombe wall-to-wall ratio limits and more significant potential for energy savings than office buildings.The study also clarifies the implications of Tibet’s climate conditions and building type differences on the effectiveness of passive solar technology.Moreover,it recommends appropriate passive solar technology adoption methods for every climate zone.This study can be used as a reference and engineering guide to improving the indoor thermal environment of Tibetan buildings,tailored to the highly variable local conditions.展开更多
An incorrect Figure 7 was published in the original article.The data for Scenarios A1-A12 were accidentally deleted during typesetting.This erratum provides the correct Figure 7.
Phase change material(PCM)applied to roofs can weak external heat entering the room to reduce air-conditioning energy consumption.In this study,three forms of macro-encapsulated PCM roofs with different PCMs(RT27,RT31...Phase change material(PCM)applied to roofs can weak external heat entering the room to reduce air-conditioning energy consumption.In this study,three forms of macro-encapsulated PCM roofs with different PCMs(RT27,RT31,RT35HC,PT37)are proposed.The effects of PCM thickness,the encapsulation forms,and different PCMs on the thermal performance of the roof are discussed in Moroccan semi-arid and Mediterranean climates.The results show that as the PCM thickness increases,the peak temperature attenuation of the roof inner surface decreases.In two climates,the pure PCM layer among the three encapsulation forms(i.e.pure PCM layer,PCM in aluminum tubes,PCM in triangular aluminum)is the easiest to appear the phenomenon of insufficient heat storage and release,while the reduction of the peak inner surface temperature and time lag is the most satisfying.For the PCM in the aluminum tube,phase change time is the shortest and the latent heat utilization ratio is the highest,while thermal regulation performance is the least satisfying.The PCM in triangular aluminum can improve the latent heat utilization ratio significantly,and its thermal regulation performance is in the middle.In semi-arid climate,the time lag increases with phase change temperature increasing.The time lag could reach up to 6 h with 37℃phase transition temperature.In Mediterranean climate,the longest time lag with RT31 is 5 h,while the lowest peak inner surface temperature appears with RT27.The obtained conclusions could provide guidance for the application of PCM roofs in these two climates.展开更多
In industrial buildings,the presence of overhead cranes severely affects roof exhaust ventilation systems when capturing and discharging fumes,resulting in severe deterioration of the indoor plant environment.In this ...In industrial buildings,the presence of overhead cranes severely affects roof exhaust ventilation systems when capturing and discharging fumes,resulting in severe deterioration of the indoor plant environment.In this study,an overhead crane-based ventilation auxiliary device,called overhead crane fume-collecting hood(CFCH),is proposed to guide pollutants blocked by the overhead crane back to the roof exhaust hood.The airflow characteristics and pollutant distribution under the three modes of no overhead crane,overhead crane,and overhead crane+CFCH were compared using numerical simulations.Subsequently,the effects of the CFCH length(a),width(b),and height(h)on the pollutant capture performance were determined through orthogonal experiments and computational fluid dynamics.Finally,the pollutant capture efficiency(PCE)of the optimal CFCH was investigated considering different exhaust airflow rates.The results showed that the pollutants captured by the CFCH can be classified into directly and secondary captured pollutants,with the directly captured pollutants dominating.In addition,with the introduction of different sizes of CFCH around the overhead crane girders,the PCE significantly improved by 49.9%–74.6%.The length,width,and height of the CFCH on the PCE were statistically significant,and the priority of the three factors was as follows:h>b>a.The PCE decreased with increasing a,initially increased and then decreased with increasing b,and increased with h.Subsequently,when the optimal CFCH was used,the excessive exhaust air rate had no evident PCE improvement.This provides a new concept for the control of pollutants in industrial buildings and provides a theoretical basis for the design of CFCHs.展开更多
Northwest China has abundant solar energy resources and a large demand for winter heating.Using solar energy for centralized heating is a clean and effective way to solve local heating problems.While present studies u...Northwest China has abundant solar energy resources and a large demand for winter heating.Using solar energy for centralized heating is a clean and effective way to solve local heating problems.While present studies usually decoupled solar heating stations and the heating network in the optimization design of centralized solar heating systems,this study developed a joint multi-objective optimization model for the equipment capacity and the diameters of the heating network pipes of a centralized solar district heating system,using minimum total life cycle cost and CO_(2)emission of the system as the optimization objectives.Three typical cities in northwest China with different solar resource conditions(Lhasa,Xining,and Xi'an)were selected as cases for analysis.According to the results,the solar heating system designed using the method proposed in this study presents lower economic cost and higher environmental protection in comparison to separately optimizing the design of the solar heating station and the heating network.Furthermore,the solar fraction of the optimal systems are 90%,70%,and 31%for Lhasa,Xining,and Xi'an,and the minimum water supply temperatures are 55℃,50℃,and 65℃for an optimal economy and 55℃,45℃,and 45℃for optimal environmental protection,respectively.It was also established that the solar collector price has a greater impact on the equipment capacity of the solar heating station than the gas boiler price.展开更多
Heating the whole space,which is currently used in northern China,leads to high energy consumption and substantial pollution.A transition to local heating has the potential to help address this problem.In this paper,t...Heating the whole space,which is currently used in northern China,leads to high energy consumption and substantial pollution.A transition to local heating has the potential to help address this problem.In this paper,the effects of radiator-related parameters(position,power,and size)and room-related parameters(aspect ratio and height)on local heating were studied.Two evaluation indices,the effective coefficient of operative temperature(OTEC)and the effective coefficient of local heating(LHEC),were proposed.In addition,the heat source-control core-area(HSCCA)was proposed,and the effect range of heat sources in the space was evaluated by the attenuation of operative temperature.The findings demonstrated that the radiator position has a greater influence on local heating than size.When the position of the radiator was changed from"close to the inner wall"to"close to the outer wall",the LHEC(the interior one-quarter of room is a local heating zone)was found to decrease by 73%.The size of the radiator,which is close to the inner wall,doubled or quadrupled,and the LHEC increased by 9%and 18%.Moreover,rooms with a larger aspect ratio or small room height were found to be the most optimal for local heating applications.The area of the HSCCA decreased as the position of the radiator approached the outer wall.The findings of this study can be used as a design reference for the radiator when the heating mode changes from"full-space heating"to"local heating".展开更多
基金Funded by the National Natural Science Foundation of China (Z20180222)the Independent Research and Development project of State Key Laboratory of Green Building in Western China (LSZZ202021)+1 种基金the Natural Science Foundation of Shaanxi Provincial Department of Education (20JY041)the Qingyuan Science and Technology Plan Project (No.2020KJJH040)。
文摘The structure and characteristics of high-performance lightweight aggregates produced by high-carbon gasification slag were investigated by X-ray diffraction,scanning electron microscopy,thermogravimetry/differential thermogravimetr,differential scanning calorimetry-Fourier transform infrared,and mercury intrusion porosimetry,respectively.The experimental results show that the ceramsite undergoes two weightless stages in the calcining process.With the increase in the calcining temperature,a large number of pores are formed inside the ceramsite,its structure becomes denser,but the calcining temperature band of the ceramsite becomes narrow.The crystalline phase of the ceramsite changes at different calcining temperatures and the mineral phase changes from the earlieralbite,quartz,oligoclase,hematite,etc,to a silica-aluminum-rich glass phase.The 1130℃ is a more suitable calcining temperature,and the cylinder compressive strength of ceramics is 11.59 MPa,the packing density,apparent density,porosity,and water absorption are 939.11 kg/m^(3),1643.75 kg/m^(3),28.11%,and 10.35%,respectively,which can meet the standards for high-strength lightweight aggregates.
基金Authors would gratefully acknowledge the financial supports of the Natural Science Foundation of the Anhui Higher Education Institutions of China(2022AH050307)the Opening Fund of State Key Laboratory of Green Building in Western China(LSKF202312)+3 种基金the National Key Research and Development Program of the Ministry of Science and Technology of China(No.2022YFC3801601-02,Wuhan University)the Science Foundation(Meteorology)Innovation Development Joint Fund Key Project of Hubei Province(No.2023M15,Wuhan University)the Foreign Aid Project for High-Level Cooperation and Exchange Activities of the Ministry of Science and Technology(No.202213,Wuhan University)the Natural Science Foundation of China(No.51778504,No.U1867221,Wuhan University).
文摘Pumping ventilation(PV),a special single-sided ventilation(SSV),has been certified as an effective strategy to improve the air exchange rate of SSV.However,most studies targeted on the single space,and few studies have been focused on the effect of internal partitioning on PV.This paper aims to evaluate the ventilation performance of PV influenced by different configurations of internal partitioning.Computational fluid dynamics(CFD)simulation was used to predict the flow fields and ventilation rates.The width(w/H),height(h/H)and location(d/H)are the three main internal partition parameters considered in this study.The simulation results showed that the total,mean and fluctuating ventilation rates all decrease with wider internal partitions.The normalized total ventilation rate decreases by 7.6%when w/H is increased from 50%to 75%.However,the reduction rate is only 0.23%between w/H=0 and 25%,and only 0.61%between w/H=25%and 50%.The ventilation rate is hardly reduced by increasing the partition width when w/H<50%,whereas greatly reduced by wider partition for w/H>50%.Increasing the partition height will reduce the mean ventilation rate but promote the fluctuating and total ventilation rate in some cases.An increase of total ventilation rate by 1.4%is observed from h/H=50%to 75%.The ventilation rate is larger when the internal partition is attached to the leeward or windward wall.The total,mean and fluctuating ventilation rates for d/H=50%are relatively higher than d/H=0 by 1.5%,3.1%and 0.8%,respectively.Hence the internal partition should be mounted attached to the windward wall so as to obtain the greatest pumping ventilation rate.The periodicity of pumping flow oscillation and pumping frequency are independent of the partition configurations.The peak power of pumping flow is the lowest for the widest internal partition and is negatively affected by the partition height,but it generally has a positive correlation with the distance between the partition and leeward wall.Present research will help to understand pumping ventilation mechanism in real buildings with internal partitioning and provide theoretical basis for developing unsteady natural ventilation technology in low-carbon buildings.
基金supported by the Independent Research and Development project of State Key Laboratory of Green Building in Western China(No.LSKF202011)the Local Funding Project for Scientific and Technological Development Guided by the Central Government(No.YDZJSX2021A022)+1 种基金the National Key Research and Development Program of China(No.2018YFD1100701-05)and the College Students’Innovative Entrepreneurial Training Plan Program of Shanxi Province(NO.20210088).
文摘Photovoltaic(PV)windows have received more and more attention in recent years since their active energy-saving advantages.Considering the surface covered with solar cell modules,the indoor daylight environment of PV windows is obviously different with clear glass windows.However,despite many scholars have studied the indoor daylight environment of PV windows,there few investigations study it from the perspective of human subjective visual perception.In this paper,the indoor daylight environment and human visual comfort of building with Cadmium Telluride Photovoltaic(CdTe-PV)window were investigated.Firstly,the parameters of indoor daylight environment and subjective questionnaires in rooms with CdTe-PV window and clear glass window were analyzed respectively.On the basis of this,combined with indoor working surface illuminance and results of subjective questionnaires,the daylight illuminance threshold of human visual comfort was investigated by the method of Mean Bias Degree(MBD).Finally,an evaluation model for indoor daylight environment of buildings with CdTe-PV window was developed by Fuzzy Comprehensive Evaluation Method.The results showed that the working surface illuminance of CdTe-PV window was lower than that of clear glass room,the CCT of different windows room had a minor gap and the CdTe-PV window room was closer to the recommended range that was 3300-5000K.As for CRI,both the CdTe-PV window room and the clear glass room could meet the visual comfort requirements of office staff.Furthermore,it was found that the requirement of human visual comfort was met when indoor working surface illuminance varies between 500-2200lx in the room with CdTe-PV window.At last,according to the comprehensive evaluation model proposed in this paper,it was found that the indoor daylight environment of buildings with CdTe-PV window was excellent in the present experiment.
基金Funded by the National Natural Science Foundation of China(No.51278403)the Program for Changjiang Scholars and Innovative Research Team in University(IRT 13089)the Doctor Innovation Foundation of Xi’an University of Architecture and Technology
文摘In order to research the sulfate attack resistance of shotcrete, the sulfate attack of shotcrete in the presence and absence of steel fiber was experimentally studied by using dry-wet cycle method. Meanwhile, compared with ordinary concrete by the same mixture, the difference of sulfate attack resistance of shotcrete was studied. The experimental results showed that, with dry-wet cycles increasing, the changes of loss rate of relative dynamic elastic modulus and mass loss rate of specimens included three stages: initial descent stage, stable stage, and rapid descent stage, respectively. However, the changes of mechanical properties first increased and then decreased. Furthermore, the corrosion products of shotcrete after sulfate attack were observed by using the method of XRD, thermal analysis, and SEM, respectively, and the failure mode of shotcrete turned from ettringite destruction to ettringite-gypsum comprehensive failure. Meanwhile, the contents of ettringite and gypsum increased with increasing dry-wet cycle. Simultaneously, the stratified powders drilled from shotcrete under 150's dry-wet cycle were analyzed for the mineral phase composition and thermal analysis. With the drywet cycle increasing, the content of ettringite first increased and then decreased and tended to stable. However, the determination of gypsum decreased gradually and even to 0 when the depth was more than 12 mm.
基金would like to acknowledge the National Natural Science Foundation of China(51590914 and 51608432)Natural Science Foundation of Shaanxi Province(2019JQ-481).
文摘Alkali-activated slag concrete (AASC) is a new green building material. The amount of CO_(2) produced by AASC is 1/5th of that produced by ordinary Portland cement concrete (OPCC). In addition, AASC promotes the reuse of slag and other wastes and saves resources. Furthermore, the scope of use of slag has been expanded. The progress of the research on the hydration characteristics, microstructure, interfacial transition zone, and pore structure of AASC based on the relevant literatures was analyzed and summarized in this study. The influences of the slag composition, the type and dosage of the alkali activator, and the curing conditions on the hydration characteristics and the microstructure of the AASC were discussed. Relatively few research results on the microstructure of AASC are available, and the relevant conclusions are not completely consistent. Moreover, there are many constraints on the development of AASC (e.g., complex composition of raw materials of slag, large shrinkage deformation, and low fluidity). Therefore, further research is required.
基金This work was supported by the General Program of National Natural Science Foundation of China(Grant No.52178026)the Young Scholars Program of National Natural Science Foundation of China(Grant No.51408479)the Program for scientific research of Shaanxi Provincial Education Department(Grant No.20JS080).
文摘Under the global crisis of energy shortage and environmental pollution,the climate responsive strategies used in vernacular buildings have attracted much attention for their potential to reduce energy consumption and carbon emissions.However,the relationships between these traditional climatic strategies were not precisely perceived,which may cause the inapplicability of these strategies for contemporary rural houses.In this paper,taking the Turpan vernacular buildings in arid region of China,the climate responsive strategies of buildings in the most significant periods such as the Gaochang period(before 1318),the Khanate and Republican period(1318–1949),the Modern period(1949–2010),and the Contemporary period(2011–present)were summarized.In addition,two different types of climatic strategies organizations,namely multilayer spaces and integrated building envelopes,were identified based on the temperature difference measurement and comparative analysis.The assessment of thermal performance of the organizations was conducted by the methodology of software simulation.Furthermore,the applicability of the organizations in rural areas was discussed,and a new combined organization was proposed.Consequently,this study can contribute to provide the main approaches for climatically responsive rural houses.
基金jointly supported by the Opening Fund of Key Laboratory of Low-grade Energy Utilization Technologies and Systems of Ministry of Education of China(Chongqing University)(LLEUTS-202305)the Opening Fund of State Key Laboratory of Green Building in Western China(LSKF202316)+4 种基金the open Foundation of Anhui Province Key Laboratory of Intelligent Building and Building Energy-saving(IBES2022KF11)“The 14th Five-Year Plan”Hubei Provincial advantaged characteristic disciplines(groups)project of Wuhan University of Science and Technology(2023D0504,2023D0501)the National Natural Science Foundation of China(51906181)the 2021 Construction Technology Plan Project of Hubei Province(2021-83)the Science and Technology Project of Guizhou Province:Integrated Support of Guizhou[2023]General 393.
文摘The available modelling data shortage issue makes it difficult to guarantee the performance of data-driven building energy prediction(BEP)models for both the newly built buildings and existing information-poor buildings.Both knowledge transfer learning(KTL)and data incremental learning(DIL)can address the data shortage issue of such buildings.For new building scenarios with continuous data accumulation,the performance of BEP models has not been fully investigated considering the data accumulation dynamics.DIL,which can learn dynamic features from accumulated data adapting to the developing trend of new building time-series data and extend BEP model's knowledge,has been rarely studied.Previous studies have shown that the performance of KTL models trained with fixed data can be further improved in scenarios with dynamically changing data.Hence,this study proposes an improved transfer learning cross-BEP strategy continuously updated using the coarse data incremental(CDI)manner.The hybrid KTL-DIL strategy(LSTM-DANN-CDI)uses domain adversarial neural network(DANN)for KLT and long short-term memory(LSTM)as the Baseline BEP model.Performance evaluation is conducted to systematically qualify the effectiveness and applicability of KTL and improved KTL-DIL.Real-world data from six-type 36 buildings of six types are adopted to evaluate the performance of KTL and KTL-DIL in data-driven BEP tasks considering factors like the model increment time interval,the available target and source building data volumes.Compared with LSTM,results indicate that KTL(LSTM-DANN)and the proposed KTL-DIL(LSTM-DANN-CDI)can significantly improve the BEP performance for new buildings with limited data.Compared with the pure KTL strategy LSTM-DANN,the improved KTL-DIL strategy LSTM-DANN-CDI has better prediction performance with an average performance improvement ratio of 60%.
基金the National Natural Science Foundation of China(No.52208103)the Youth Fund of Anhui Natural Science Foundation(No.2208085QE163 and No.2108085QE241)+2 种基金the Anhui Province University Outstanding Scientific Research and Innovation Team(No.2022AH010021)the Opening Fund of State Key Laboratory of Green Building in Western China(No.LSKF202303)the Housing and Urban-Rural Construction Science and Technology Program of Anhui Province(No.2022-YF062).
文摘In the context of racing to carbon neutrality,the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element,which also provides an opportunity for thermal insulation solutions to transform from high to zero-carbon attributes.Based on the re-examination of the heat transfer process of conventional pipe-embedded radiant(CPR)walls,the modular pipe-embedded radiant(MPR)wall integrated with thermal diffusive materials is proposed to enhance the heat transfer capacity of CPR walls in the direction parallel to the wall surface,thereby forming a more stable and continuous invisible thermal barrier layer inside the opaque envelopes.A comprehensive thermal and energy-saving analysis study regarding the influence mechanism of several key factors of MPR walls,e.g.,the inclination angle of the filler cavity(θ-value),geometry size of the filler cavity(a:b-value)and thermal conductivity of the filler(λf-value),is conducted based on a validated numerical model.Results show that the dynamic thermal behaviors of MPR walls can be significantly improved due to that the radial thermal resistance in the filler cavity of MPR walls can be reduced by 50%,while the maximum extra exterior surface heat loss caused by the optimization measures is only 2.1%.Besides,a better technical effect can be achieved by setting the major axis of the filler cavity towards the room side,where the interior surface heat load/total injected heat first decreases/increases and then increases/decreases with the increase of theθ-value.In particular,the MPR wall withθL=60°can obtain the best performance when other conditions remain the same.Moreover,the performance indicators of MPR walls can be further improved with the increase of the cavity size(a:b-value),while showing a trend of rapid improvement in theλf-value range of 2–5λC and slow improvement increase in theλf-value range of 5–12λC.In addition,the improvement effect brought by optimizing theθ-value is more obvious as the a:b-value orλf-value increases.
基金financial supports for this work provided by National Natural Science Foundation of China (No.51838011,52078407)。
文摘Building thermal climatic zoning is a key issue in building energy efficiency.Heating degree days(HDD) and cooling degree days(CDD) are often employed as indexes to represent the heating and cooling energy demand in climatic zoning.However,only using degree days may oversimplify the climatic zoning in regions with complex climatic conditions.In the present study,the application of degree days to current building thermal climatic zoning in China was assessed based on performance simulations.To investigate the key indexes for thermal climatic zoning,the climate characteristics of typical cities were analyzed and the relationships between the climate indexes and heating/cooling demand were obtained.The results reveal that the annual cumulative heating load had a linear correlation with HDD 18 only in regions with small differences in altitude.Therefore,HDD is unsuitable for representing the heating demand in regions with large differences in altitude.A comprehensive index(winter climatic severity index) should be employed instead of HDD,or complementary indexes(daily global solar radiation or altitude) could be used to further divide climate zones.In the current official climatic zoning,the base temperature of 26℃ for CDD is excessively high.The appropriate base temperature range is 18℃ to 22℃.This study provides a reference for selecting indexes to improve thermal climatic zoning in regions with similar climates.
基金supported by the National Natural Science Foundation of China (52008328)National Key Research and Development Project (2018YFD1100202)+1 种基金the Science and Technology Department of Shaanxi Province (2020SF-393,2018ZDCXL-SF-03-04)the State Key Laboratory of Green Building in Western China (LSZZ202009).
文摘The energy consumption of a teaching building can be effectively reduced by timetable optimization.However,in most studies that explore methods to reduce building energy consumption by course timetable optimization,self-study activities are not considered.In this study,an MATLAB-EnergyPlus joint simulation model was constructed based on the Building Controls Virtual Test Bed platform to reduce building energy consumption by optimizing the course schedule and opening strategy of self-study rooms in a holistic way.The following results were obtained by taking a university in Xi’an as an example:(1)The energy saving percentages obtained by timetabling optimization during the heating season examination week,heating season non-examination week,cooling season examination week,and cooling season non-examination week are 35%,29.4%,13.4%,and 13.4%,respectively.(2)Regarding the temporal arrangement,most courses are scheduled in the morning during the cooling season and afternoon during the heating season.Regarding the spatial arrangement,most courses are arranged in the central section of the middle floors of the building.(3)During the heating season,the additional building energy consumption incurred by the opening of self-study rooms decreases when duty heating temperature increases.
基金The work was supported by the Natural Science Basic Research Program of Shaanxi Province of China(2023-JC-YB-473)the Opening Fund of State Key Laboratory of Green Building in Western China(LSKF202314).The authors would like to express their gratitude to MogoEdit(http://en.mogoedit.com/)for the professional linguistic services provided.
文摘Window opening behavior significantly impacts indoor air quality,thermal comfort,and energy consumption.A field measurement was carried out in three typical rooms(a standard office,a meeting room and a smoking office)within an office building.The window state and the physical environment were continuously recorded during the measured periods.Three typical window opening behaviors were found in the measured samples,namely,active,moderate,and passive.The common logistic regression coefficient indicated that solar radiation exhibited the greatest effect on window opening behavior in the smoking office and standard office.Typically,window opening behavior in the meeting room was the most strongly correlated with time of the day,mainly because of the meeting schedule for occupants in the meeting room.This study discussed the dividing principles involved in setting the dummy variable interval level(discretizing continuous variables and dividing them into different intervals),and proposed a method to determine the optimal interval level of each variable.The improved model led to the increase in the prediction accuracy rate of the window being opened by 2.0%and 3.3%according to the comparison with the original model based on dummy variables and the common model based on continuous variables,respectively.This study can provide a reference value for simulating energy consumption in office buildings in the future.
基金This work was supported by the National Natural Science Foundation of China(No.51878534,No.51878532 and U20A20311)State Key Laboratory of Green Building in Western China.
文摘At present,thermal conductivity is usually taken as a constant value in the calculation of building energy con-sumption and load.However,in the actual use of building materials,they are exposed to the environment with continuously changing temperature and relative humidity.The thermal conductivity of materials will inevitably change with temperature and humidity,leading to deviations in the estimation of energy consumption in the building.Therefore,in this study,variations in the thermal conductivity of eight common building insulation materials(glass wool,rock wool,silica aerogel blanket,expanded polystyrene,extruded polystyrene,phenolic foam,foam ceramic and foam glass)with temperature(in the range of 20-60°C)and relative humidity(in the range of 0-100%)were studied by experimental methods.The results show that the thermal conductivity of these common building insulation materials increased approximately linearly with increasing temperature with maxi-mum growth rates from 3.9 to 22.7%in the examined temperature range.Due to the structural characteristics of materials,the increasing thermal conductivity of different materials varies depending on the relative humidity.The maximum growth rates of thermal conductivity with humidity ranged from 8.2 to 186.7%.In addition,the principles of selection of building insulation materials in different humidity regions were given.The research re-sults of this paper aim to provide basic data for the accurate value of thermal conductivity of building insulation materials and for the calculation of energy consumption.
基金supported by the China Postdoctoral Science Foundation (Grant No. 2017M613086)Key Theoretical and Practical Research Fund of Shaanxi Social Sciences(Grant No. 2018Z040)+2 种基金Shaanxi Ministry of Construction-Technology Development Plan (2016-RZ54)Project of Science and Technology Plan of Ministry of Housing Urban-Rural Construction (UDC2017032312)“the 13th Five-Year” National Science and Technology Major Project of China (No. 2018YFC0704500)
文摘Studies on building carbon emissions focus mainly on the materialization phase of life cycle, as carbon emissions in this stage is intensive and high. This paper proposes a simplified model to calculate embodied carbon emissions in building design stage by conducting a process-based inventory analysis of carbon emissions from materials used in 129 residential buildings, 41 office buildings, and 21 commercial buildings during materialization phase. The results indicate that average carbon emissions per unit area from building materials used in residential buildings, office buildings, and commercial buildings are 514.66 kgCO2 e/m2, 533.69 kg CO2 e/m2 and 494.19 kgCO2 e/m2, respectively. Besides, ten kinds of building materials(namely, steel, commercial concrete, wall building materials, mortar, copper core cables, architectural ceramics, PVC pipes, thermal insulation materials, doors and windows, and water paint) constitute 99% of total carbon emissions in all three types of buildings. These materials are major carbon emissions sources in materialization phase. Thus, embodied carbon emissions can be significantly reduced by limiting the amount of these materials in architectural design as well as by using environmental friendly materials.
基金Funded by the National Natural Science Foundation of China (Nos.51590914 and 52078415)the Science and Technology Program of Shaanxi Province (Nos.2019KW-047, 20JY034, and SGSNXA00XGJS20015 60)the China Scholarship Council (No.202008610268)。
文摘Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity.
基金supported by the National Key Research and Development Project(No.2019YFE0104900)Joint Fund for Regional Innovation and Development of National Natural Science Foundation of China(No.U20A20311)the National Natural Science Foundation of China(No.52008329).
文摘China’s Tibet autonomous region has abundant solar energy resources,cold winters,and cool summers.These are ideal conditions for the application of passive solar heating methods.However,differences in climatic conditions and building types can significantly affect passive solar technology’s feasibility,which makes it challenging to promote passive solar buildings in Tibet.In this study,the suitability zone for passive solar technology is categorized based on the sub-zoning indicators for Tibet.By modeling between direct gain windows,Trombe walls,and attached sunspaces,the effect of indoor thermal environments and the capacity for heating load reduction is compared for different passive solar technologies.The climate-difference impact analysis shows that the I-B-1 zone is better suited for passive solar technology than other climate zones.More specifically,this zone has an average energy-saving rate difference of up to 28.61%compared to the II-A-1 zone.The analysis of the impact of building type differences indicates that residential buildings have higher Trombe wall-to-wall ratio limits and more significant potential for energy savings than office buildings.The study also clarifies the implications of Tibet’s climate conditions and building type differences on the effectiveness of passive solar technology.Moreover,it recommends appropriate passive solar technology adoption methods for every climate zone.This study can be used as a reference and engineering guide to improving the indoor thermal environment of Tibetan buildings,tailored to the highly variable local conditions.
文摘An incorrect Figure 7 was published in the original article.The data for Scenarios A1-A12 were accidentally deleted during typesetting.This erratum provides the correct Figure 7.
基金This study was supported by a grant from National Key R&D Program of China(No.2020YFE0200300)The authors gratefully acknowledge financial support from China Scholarship Council.
文摘Phase change material(PCM)applied to roofs can weak external heat entering the room to reduce air-conditioning energy consumption.In this study,three forms of macro-encapsulated PCM roofs with different PCMs(RT27,RT31,RT35HC,PT37)are proposed.The effects of PCM thickness,the encapsulation forms,and different PCMs on the thermal performance of the roof are discussed in Moroccan semi-arid and Mediterranean climates.The results show that as the PCM thickness increases,the peak temperature attenuation of the roof inner surface decreases.In two climates,the pure PCM layer among the three encapsulation forms(i.e.pure PCM layer,PCM in aluminum tubes,PCM in triangular aluminum)is the easiest to appear the phenomenon of insufficient heat storage and release,while the reduction of the peak inner surface temperature and time lag is the most satisfying.For the PCM in the aluminum tube,phase change time is the shortest and the latent heat utilization ratio is the highest,while thermal regulation performance is the least satisfying.The PCM in triangular aluminum can improve the latent heat utilization ratio significantly,and its thermal regulation performance is in the middle.In semi-arid climate,the time lag increases with phase change temperature increasing.The time lag could reach up to 6 h with 37℃phase transition temperature.In Mediterranean climate,the longest time lag with RT31 is 5 h,while the lowest peak inner surface temperature appears with RT27.The obtained conclusions could provide guidance for the application of PCM roofs in these two climates.
基金sponsored by the National Science Foundation of China(No.51908446,No.52278128).
文摘In industrial buildings,the presence of overhead cranes severely affects roof exhaust ventilation systems when capturing and discharging fumes,resulting in severe deterioration of the indoor plant environment.In this study,an overhead crane-based ventilation auxiliary device,called overhead crane fume-collecting hood(CFCH),is proposed to guide pollutants blocked by the overhead crane back to the roof exhaust hood.The airflow characteristics and pollutant distribution under the three modes of no overhead crane,overhead crane,and overhead crane+CFCH were compared using numerical simulations.Subsequently,the effects of the CFCH length(a),width(b),and height(h)on the pollutant capture performance were determined through orthogonal experiments and computational fluid dynamics.Finally,the pollutant capture efficiency(PCE)of the optimal CFCH was investigated considering different exhaust airflow rates.The results showed that the pollutants captured by the CFCH can be classified into directly and secondary captured pollutants,with the directly captured pollutants dominating.In addition,with the introduction of different sizes of CFCH around the overhead crane girders,the PCE significantly improved by 49.9%–74.6%.The length,width,and height of the CFCH on the PCE were statistically significant,and the priority of the three factors was as follows:h>b>a.The PCE decreased with increasing a,initially increased and then decreased with increasing b,and increased with h.Subsequently,when the optimal CFCH was used,the excessive exhaust air rate had no evident PCE improvement.This provides a new concept for the control of pollutants in industrial buildings and provides a theoretical basis for the design of CFCHs.
基金This research was supported by the National Natural Science Foundation of China(52008328)National Key Research and Development Project(2018YFD1100202)+1 种基金the Science and Technology Department of Shaanxi Province(2020SF-393,2018ZDCXL-SF-03-04)the State Key Laboratory of Green Building in Western China(LSZZ202009).
文摘Northwest China has abundant solar energy resources and a large demand for winter heating.Using solar energy for centralized heating is a clean and effective way to solve local heating problems.While present studies usually decoupled solar heating stations and the heating network in the optimization design of centralized solar heating systems,this study developed a joint multi-objective optimization model for the equipment capacity and the diameters of the heating network pipes of a centralized solar district heating system,using minimum total life cycle cost and CO_(2)emission of the system as the optimization objectives.Three typical cities in northwest China with different solar resource conditions(Lhasa,Xining,and Xi'an)were selected as cases for analysis.According to the results,the solar heating system designed using the method proposed in this study presents lower economic cost and higher environmental protection in comparison to separately optimizing the design of the solar heating station and the heating network.Furthermore,the solar fraction of the optimal systems are 90%,70%,and 31%for Lhasa,Xining,and Xi'an,and the minimum water supply temperatures are 55℃,50℃,and 65℃for an optimal economy and 55℃,45℃,and 45℃for optimal environmental protection,respectively.It was also established that the solar collector price has a greater impact on the equipment capacity of the solar heating station than the gas boiler price.
基金The research was supported by the National Natural Science Foundation of China(No.52078408)the Science Foundation for Outstanding Youth of Shaanxi Province(2020JC-43).
文摘Heating the whole space,which is currently used in northern China,leads to high energy consumption and substantial pollution.A transition to local heating has the potential to help address this problem.In this paper,the effects of radiator-related parameters(position,power,and size)and room-related parameters(aspect ratio and height)on local heating were studied.Two evaluation indices,the effective coefficient of operative temperature(OTEC)and the effective coefficient of local heating(LHEC),were proposed.In addition,the heat source-control core-area(HSCCA)was proposed,and the effect range of heat sources in the space was evaluated by the attenuation of operative temperature.The findings demonstrated that the radiator position has a greater influence on local heating than size.When the position of the radiator was changed from"close to the inner wall"to"close to the outer wall",the LHEC(the interior one-quarter of room is a local heating zone)was found to decrease by 73%.The size of the radiator,which is close to the inner wall,doubled or quadrupled,and the LHEC increased by 9%and 18%.Moreover,rooms with a larger aspect ratio or small room height were found to be the most optimal for local heating applications.The area of the HSCCA decreased as the position of the radiator approached the outer wall.The findings of this study can be used as a design reference for the radiator when the heating mode changes from"full-space heating"to"local heating".
