检索结果-南通市图书馆

Study on wood drying Properties under Vacuum-floating Pressure

在线全文

学校读者我要写书评

暂无评论

Chinese Forestry Science and Technology 2004年第4期3卷 65-71页

作者： ZHANGBiguang YISonghn CHANGJianmin LIXianjun MaterialScienceandTechnologySchoolofBeijingForestryUniversity Beijing100083P.R.China

Using Masson pine as specimens, when drying mediums are overheated steam and hot-air respectively, preheating characteristics of wood under vacuum-floating pressure drying are discussed by measurement of internal temperature field and variation of moisture content during period of preheating. The relationship between drying medium conditions and drying rate of wood reveals that, firstly, compared with process of air-drying, time needed to be preheated under vacuum-floating decreased dramatically, meanwhile,the magnitude of condensation on the surface is relatively larger. Secondly, drying rate of wood under vacuum-floating pressure increases coupled with temperature of medium, reduction of absolute pressure,and raise of fluctuation rate of pressure. The sequence of factors contribution to drying rate is listed as following: temperature of medium (t) > fluctuation rate of pressure (f)> absolute pressure (p).

关键词： wood drying vacuum-floating pressure preheating characteristics

Numerical Modelling of drying Induced Cracks in wood Discs Using the Extended Finite Element Method

在线全文

学校读者我要写书评

暂无评论

Journal of Renewable Materials 2023年第1期11卷 93-102页

作者： Zongying Fu Yongdong Zhou Tingguo Yan Yun Lu Research Institute of wood Industry Chinese Academy of ForestryKey Lab of Wood Science and Technology of Status Forestry and Grassland AdministrationBeijing100091China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin150001China

drying crack is a common phenomenon occurring during moisture discharge from wood,reducing efficient wood *** crack is primarily caused by drying stress,and the reasonable methods for determining drying stress are *** this study,the initiation and propagation of cracks during wood discs drying were simulated using the extended finite element method(XFEM).The distribution of drying stress and displacement was analyzed at different crack conditions based on the simulation *** study aimed to solve the problem of the limitation of drying stress testing methods and provide a new idea for the study of wood drying *** numerical simulation results are found in good agreement with the experimental results,thus corroborating the feasibility of XFEM in modeling drying crack of wood *** stress concentration was observed at the crack tip region,while a minor stress was presented in the region of crack passing through,indicating that the crack formation process was also a process of releasing drying ***,more energy was required to form double cracks in comparison with the single crack mode.

关键词： wood drying queensland peppermint drying cracks numerical simulation experimental validation XFEM

Study on drying Characteristic of Chinese Fir and Poplar Plantation wood

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Forestry Science and Technology 2004年第4期3卷 72-75页

作者： ZHOUYongdong LIXiaoling ResearchInstituteofwoodIndustry ChineseAcademyofForestryBeijing100091PR.China

The drying characteristic was studied for plantation wood of Chinese fir and poplar, which are typical plantation wood of southern and northern part of China, respectively. Through 100-degree-method the drying characteristic and basic drying condition were gotten, then drying schedule was developed for practical drying, the results showed that the drying schedule is suitable for Chinese fir and poplar plantation lumber, but shrinkage is large. The recommendation was made that enough dead weight is needed to decrease shrinkage in drying process. The drying quality of the two species of lumber is good in conventional drying method.

关键词： plantation lumber wood drying drying schedule defects shrinkage deformation warp

drying Characteristics of wood under Vacuum-superheated Steam

在线全文

学校读者我要写书评

暂无评论

Forestry Studies in China 2004年第2期6卷 41-45页

作者： YiSonglin ZhangBiguang ChangJianmin DuChaogang CollegeofMaterialSciencesandTechnology BeijingForestryUniversityBeijing100083P.R.China

This paper presents comparison and analysis of thermal-dynamic characteristics of air-drying and superheated steam drying under vacuum. The result reveals that for both convective heat transfer coefficient and resistance of mass transfer on the surface, superheated steam drying under vacuum is superior to air-drying under the same condition. With Masson pine as specimen, we found that the inversion temperature really exists through comparable experiments of air-drying and superheated steam drying under vacuum. When temperature is above inversion point of temperature, drying speed is faster than that of air-drying; however, if temperature is below the point, the result is opposite. The inversion temperature of experiment ranges from 80 to 85 ℃.

关键词： wood drying vacuum superheated steam inversion temperature

External Heat Transfer in Moist Air and Superheated Steam for Softwood drying

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2004年第6期12卷 762-766页

作者： PANGShusheng woodTechnologyResearchCentre DepartmentofChemicalandProcessEngineeringUniversityofCanterburyChristchurchNewZealand

In kiln drying of softwood timber, external heat and moisture mass transfercoefficients are important in defining boundary temperature and moisture content at the woodsurface. In addition, superheated steam drying of wood is a promising technology but this has notbeen widely accepted commercially, partially due to the lack of understanding of the dryingphenomena occurred during drying. In this work, experimental investigation was performed to quantifythe heat transfer between wood surface and surrounding moist air or superheated steam. In theexperiment, saturated radiata pine sapwood samples were dried using dry-bulb/wet-bulb temperaturesof 60℃/50℃, 90℃/60℃, 120℃/70℃, 140℃/90℃, 160℃/90℃, 140℃/100℃ and 160℃/100℃. The lasttwo schedules were for superheated steam drying as the wet-bulb temperature was set at 100℃. Thecirculation velocity over the board surface was controlled at 4.2m·s^(-1). Two additional runs(90℃/60℃) using air velocities of 2.4 m·s^(-1) and 4.8 m·s^(-1) were performed to check theeffect of the circulation velocity. During drying, sample weight and temperatures at wood surfaceand different depths were continuously measured. Prom these measurements, changes in woodtemperature and moisture content were calculated and external heat-transfer coefficient wasdetermined for both the moist air and the superheated steam drying.

关键词： wood drying external heat transfer coefficient moist air moisture content softwood timber superheated steam

What is going up in smoke?——A study of emissions in the wood industry

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2003年第2期14卷 162-166,187页

作者： Dilian He Nicholson Faculty of Forestry and Agriculture University of MelbourneCreswick

The requirements that a business needs to consider when building a wood panels manufacturing plant are much the same as they have been for decades, but today there is also the need for multiple environmental studies and permits. These are costly and time consuming additional expenses that often are the longest lead-time items on any project. Most industrialized countries have legislation in place to limit and control the negative impact that emission of pollutants may have on the environment. This paper discusses what is actually happening inside wood drying plants, and the prerequisite conditions for genesis of pyrolytic products relative to the operational parameters, such as choice of input raw materials, driers design and operational regime, choice of fuels for the heat generation and how these factors influence production of stack emission. The characterization of emission condensate by analytical methods is described, and survey of emission control system in use worldwide is described, and means of investigating what may be the optimum design for the control of emission is discussed. Alternate uses of utilizing the condensate, other than burning, are presented for consideration.

关键词： wood drying Pollution Emission analysis Emission control Alternate usage

Physical Properties and Heat Transfer of Tectona grandis L.f. wood

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Science and Engineering(B) 2012年第12期1卷 1303-1310页

作者： Joao Vicente de Figueiredo Latorraca Gilmar Correia Silva Luiz Guilherme Souza Lima Department of Forest Products Forest Institute Federal Rural University of Rio de Janeiro BrazilSeropedica 23890-000 Department of Plant Science and Zootechny State University of Southwest BahiaBrazil Vit6ria da Conquista 45083-900

Tectona grandis L.f. （teak） is native to the Indian subcontinent and southeast Asia, and today is grown in almost every tropical region, for the physical and mechanical properties of its wood. Also, important qualitative aspects render it one of the most expensive wood species in the world. This work presents a study about the physical properties and heat transfer of T. grandis wood from plantations in ***, Mato Grosso, Brazil. Six trees planted at three different intervals were used--two from each planting density--selected at random and with good phytosanitary characteristics, as well as having representative diameters and heights. The following properties were determined： basic and apparent densities, volume contraction, heat transfer and fiber saturation point. The basic and apparent mean general density of the samples was 0.48 g/cm3 and 0.55 g/cm3, respectively. The mean volume contraction of the teak wood was 8.57%. With decreased levels of wood humidity, loss of volume and planting effects were not significant at 5% probability. Mean heat transfer was 7.3 h/cm and the wood fiber saturation point was 17.25%, below the range found in literature, and there was no influence of the planting density on this property. According to the results, it was concluded that planting density significantly influenced the base density of the wood; the same effect does not occur for the other physical properties, and with respect to heat transfer, the wood was considered difficult to dry.

关键词： wood material science wood behavior wood drying Tectona grand& teak.

Corrective Interventions to End-Splitting and Surface Cracking in Kenya Grown Eucalyptus grandis Poles

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Forestry 2022年第3期12卷 380-392页

作者： George Muthike Godfrey Ali Nellie Oduor Paul Munene Joseph Githiomi Kenya Forestry Research Institute Nairobi Kenya Kenya wood Preservers Association Homa Bay Kenya Kenya Bureau of Standards Nairobi Kenya

This study determined the effect of three pole pre-drying handling techniques, on end-splitting and surface checking in Eucalyptus grandis poles from highland and low land areas in Kenya. A total of 144 Eucalyptus grandis trees were sampled from two sites;Kericho, representing the wet highlands and Londiani representing the drier lowlands regions of Kenya. Pole samples from both sites were subjected to the three pre-drying handling techniques for the first 30 days after felling and allowed to dry to the required moisture level under observations. The number of end splits and surface checks on each sample pole were counted and the length of the worst ones was measured in millimeters after every 15 days until all the poles reached 25% MC. The sap wood and heart wood ratios were determined from selected samples. Results showed that on the overall, poles from high land areas had the highest sapwood proportions and similarly had the highest number and the longest end splitting and surface checks. On the other hand, pre-drying techniques that allowed felled trees to dry slowly with their foliage intact for the first 30 days of felling produced the best quality poles, with fewer and shallower end splits and surface checks. The study recommended that felling and leaving poles to dry slowly with foliage intact be considered in reducing losses incurred as a result of wood stresses during drying of poles.

关键词： Eucalyptus grandis wood Cracking wood Stresses wood drying