Urban heat environmental quality (UHEQ) is affected by the interacting of weather condition and underlying surface framework of urban area. In the last two decades, many researchers from domestic and overseas have stu...Urban heat environmental quality (UHEQ) is affected by the interacting of weather condition and underlying surface framework of urban area. In the last two decades, many researchers from domestic and overseas have studied many problems at the aspect of urban heat environment such as urban heat islands, urban air temperature and their relation with urban land cover, city population, air pollution etc. In the recent years, Hangzhou, acting as a center city of Zhejiang Province in China, its urbanization quantum and quantity have both changed greatly, in particular, representing as business affairs building, resident real property and all kinds of specialty market having arisen in built-up zone. Based on Landsat TM images data in 1991 and 1999, urban underlying surface temperature value and Normalized Difference Vegetation Index (NDVI) were calculated using image interpreting and supervised classification technique by remote sensing software ERDAS image 8.4. The relation model between urban underlying surface temperature (UUST) and urban air temperature was setup according to the certain correlation pattern. Reference to the relational standard of assessing human comfort and other meteorology data of Hangzhou City in summer, the spatial distribution characteristic and the spatial variation degree of human comfort of heat environmental quality are estimated and mapped on a middle scale, that is, in six districts of Hangzhou City . Then the paper reveals the main characteristic of spatial variation from 1991 to 1999. Lastly, the change mechanism is analyzed and discussed from the viewpoint of city planning, construction and environmental protection.展开更多
This study focuses on numerically investigating thermal behavior within a differentially heated cavity filled with nanofluid with and without obstacles.Numerical comparison with previous studies proves the consistency...This study focuses on numerically investigating thermal behavior within a differentially heated cavity filled with nanofluid with and without obstacles.Numerical comparison with previous studies proves the consistency and efficacy of the lattice Boltzmann method associated with a single relaxation time and its possibility of studying the nanofluid and heat transfer with high accuracy.Key parameters,including nanoparticle type and concentration,Rayleigh number,fluid basis,and obstacle position and dimension,were examined to identify optimal conditions for enhancing heat transfer quality.Principal findings indicated that increasing the Rayleigh number boosts buoyancy forces and alters vortex structure,improving the heat transfer efficiency across all nanofluid configu-rations.Moreover,nanoparticles with higher thermal conductivity,particularly Cu nanoparticles,exhibit slight improvements in heat transfer quality compared to Al2O3 nanoparticles,while higher nanoparticle concentrations generally lead to enhanced heat transfer effectiveness.Water-Cu nanofluids also demonstrate superior heat transfer performance over ethylene glycol-Cu nanofluids.Furthermore,the presence of obstacles at cavity extremities hampers overall heat transfer,whereas those positioned centrally augment heat exchange rates.This research offers valuable insights into optimizing convective heat transfer in nanofluid-filled cavities crucial for various engineering applications.展开更多
To simultaneously improve the quantity and quality of heat recovery in a heat exchanger network(HEN),this study conducts a theory analysis based on the first and second laws of thermodynamics.Under the premise of maxi...To simultaneously improve the quantity and quality of heat recovery in a heat exchanger network(HEN),this study conducts a theory analysis based on the first and second laws of thermodynamics.Under the premise of maximizing the heat recovery quantity of HEN,Ġdiss is used as an evaluation index to optimize the quality of heat recovery.Meanwhile,the total annual cost(TAC)is considered as another optimization objective to ensure the economic feasibility of the HEN.A superstructure-based multi-objective mixed integer non-linear programming approach is put forward to solve the trade-off between minimizingĠdiss and minimizing TAC.This allows for the optimum HEN structure to be obtained.A well-studied example is solved to highlight the benefits of the proposed method.展开更多
基金Under the auspices of the National Natural Science Foundation of China (No.40001008).
文摘Urban heat environmental quality (UHEQ) is affected by the interacting of weather condition and underlying surface framework of urban area. In the last two decades, many researchers from domestic and overseas have studied many problems at the aspect of urban heat environment such as urban heat islands, urban air temperature and their relation with urban land cover, city population, air pollution etc. In the recent years, Hangzhou, acting as a center city of Zhejiang Province in China, its urbanization quantum and quantity have both changed greatly, in particular, representing as business affairs building, resident real property and all kinds of specialty market having arisen in built-up zone. Based on Landsat TM images data in 1991 and 1999, urban underlying surface temperature value and Normalized Difference Vegetation Index (NDVI) were calculated using image interpreting and supervised classification technique by remote sensing software ERDAS image 8.4. The relation model between urban underlying surface temperature (UUST) and urban air temperature was setup according to the certain correlation pattern. Reference to the relational standard of assessing human comfort and other meteorology data of Hangzhou City in summer, the spatial distribution characteristic and the spatial variation degree of human comfort of heat environmental quality are estimated and mapped on a middle scale, that is, in six districts of Hangzhou City . Then the paper reveals the main characteristic of spatial variation from 1991 to 1999. Lastly, the change mechanism is analyzed and discussed from the viewpoint of city planning, construction and environmental protection.
文摘This study focuses on numerically investigating thermal behavior within a differentially heated cavity filled with nanofluid with and without obstacles.Numerical comparison with previous studies proves the consistency and efficacy of the lattice Boltzmann method associated with a single relaxation time and its possibility of studying the nanofluid and heat transfer with high accuracy.Key parameters,including nanoparticle type and concentration,Rayleigh number,fluid basis,and obstacle position and dimension,were examined to identify optimal conditions for enhancing heat transfer quality.Principal findings indicated that increasing the Rayleigh number boosts buoyancy forces and alters vortex structure,improving the heat transfer efficiency across all nanofluid configu-rations.Moreover,nanoparticles with higher thermal conductivity,particularly Cu nanoparticles,exhibit slight improvements in heat transfer quality compared to Al2O3 nanoparticles,while higher nanoparticle concentrations generally lead to enhanced heat transfer effectiveness.Water-Cu nanofluids also demonstrate superior heat transfer performance over ethylene glycol-Cu nanofluids.Furthermore,the presence of obstacles at cavity extremities hampers overall heat transfer,whereas those positioned centrally augment heat exchange rates.This research offers valuable insights into optimizing convective heat transfer in nanofluid-filled cavities crucial for various engineering applications.
基金The authors would like to gratefully acknowledge the financial support provided by the National Key R&D Program of China(2017YFE0116300,2019YFE0122100)the Youth Innovation Promotion Association,CAS(2017353)the DNL Cooperation Fund,CAS(DNL202023).
文摘To simultaneously improve the quantity and quality of heat recovery in a heat exchanger network(HEN),this study conducts a theory analysis based on the first and second laws of thermodynamics.Under the premise of maximizing the heat recovery quantity of HEN,Ġdiss is used as an evaluation index to optimize the quality of heat recovery.Meanwhile,the total annual cost(TAC)is considered as another optimization objective to ensure the economic feasibility of the HEN.A superstructure-based multi-objective mixed integer non-linear programming approach is put forward to solve the trade-off between minimizingĠdiss and minimizing TAC.This allows for the optimum HEN structure to be obtained.A well-studied example is solved to highlight the benefits of the proposed method.
