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Contrasting compositions of PM_(2.5)in Northern Thailand during La Nina(2017)and El Nino(2019)years

Journal of Environmental Sciences 2024年第1期135卷 585-599页

作者： Pavidarin Kraisitnitikul Duangduean Thepnuan Sarana Chansuebsri Nuttipon Yabueng Wan Wiriya supattarachai saksakulkrai Zongbo Shi Somporn Chantara Environmental Science Research Center Faculty of ScienceChiang Mai UniversityChiang Mai50200Thailand Department of Chemistry Faculty of Science and TechnologyChiang Mai Rajabhat UniversityChiang Mai50300Thailand Chemistry Department Faculty of ScienceChiang Mai UniversityChiang Mai50200Thailand School of Geography Earth and Environmental SciencesUniversity of BirminghamBirminghamB152TTUK

There have been a very limited number of systematic studies on PM_(2.5)compositions and their source contribution in Southeast Asia.This study aims to explore the characteristics of PM_(2.5)composition collected in Chiang Mai(Thailand)during La Nina and El Nino years and to apportion their sources during smoke haze and non-haze periods.The average PM_(2.5)concentration of smoke haze episode in 2019(El Nino)was much higher than in 2017(La Nina).The ratios of organic carbon(OC)to elemental carbon(EC),as well as K(biomass burning(BB)tracer)to PM_(2.5),were higher during smoke haze episodes in 2019 than in 2017 indicating a significant influence from BB.The ratios of secondary organic carbon(SOC)levels to primary organic carbon(POC)levels during smoke haze episodes were higher than those in non-haze period,which indicated greater SOC contributions or more photo-oxidation of precursors in haze episodes with high ambient temperatures.However,the ratios of soil markers(Ca and Mg)during non-haze period were high implying that soil source contributed more to PM_(2.5)concentrations when there less BB occurred.The positive Matrix Factorization(PMF)model revealed that the source of BB,characterized by high K fractions,was the largest contributor during smoke haze episodes accounting for 50%(2017)and 79%(2019).Climate conditions influence meteorological patterns,particularly during incidences of extreme weather such as droughts,which affect the scale and frequency of open burning and thus air pollution levels.

关键词： Climate Air pollution Metals Carbon Biomass burning Source identification

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内带分散的V型翅片的热交换方管的强化传热（英文）

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Chinese Journal of Chemical Engineering 2015年第3期23卷 490-498页

作者： Watcharin Noothong supattarachai Suwannapan Chinaruk Thianpong Pongjet Promvonge Department of Mechanical Engineering Faculty of EngineeringKing Mongkut's Institute of Technology Ladkrabang

The article presents an experimental and numerical study on thermal performance enhancement in a constant heatfluxed square-duct inserted diagonally with 45° discrete V-finned tapes(DFT).The experiments were carried out by varying the airflow rate through the tested square duct with DFT inserts for Reynolds number from 4000 to 25000.The effect of the DFT with V-tip pointing upstream at various relative fin heights and pitches on heat transfer and pressure drop characteristics was experimentally investigated.Both the heat transfer and pressure drop were presented in terms of Nusselt number and friction factor respectively.Several V-finned tape characteristics were introduced such as fin- to duct-height ratio or blockage ratio(R_B=e/H = 0.075,0.1,0.15 and 0.2),fin pitch to duct height ratio(R_P= P/H=0.5,1.0,1.5 and 2.0) and fin attack angle,α = 45°.The experimental results reveal that the heat transfer and friction factor values with DFT inserts increase with the increment of R_B but the decrease of R_P.The inserted square-duct at R_B = 0.2 and R_P = 0.5 provides the highest heat transfer and friction factor while the one with R_B= 0.1 and R_P= 1.5 yields the highest thermal performance.Also,a numerical simulation was conducted to investigate the flow structure and heat transfer mechanism inside the tested duct with DFT inserts.

关键词：强化传热离散换热器插入管摩擦系数数值模拟压降特性翅片间距

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