The Equilibrium Moisture Content of Five Lesser Utilized Species of Ghana Contrasted with Three European Species

Equilibrium moisture contents (EMC) of wood species are very necessary in the utilization of these in service. This study investigated the EMC of five lesser utilized species of Ghana and compared it with that of three European species. Sixteen randomly sampled specimens of each of the eight species (heartwood and sapwood) with dimensions 3 cm × 3 cm × 3 cm were exposed at various relative humidity conditions of 30%, 45%, 60%, 75% and 90% in a temperature and humidity-controlled climate chamber at a temperature of 25°C in accordance to German standard DIN 52182. The species are Albies alba, Fagus sylvatica and Picea abies which are European species and Amphimas pterocarpoides, Antiaris toxicaria, Canarium schweinfurthii, Celtis zenkeri and Cola gigantea are wood species from Ghana. Internal wood temperature and humidity were measured with datalogger. Samples were considered to have reached equilibrium at any given humidity when the daily weight changes were less than 0.1 mg according to German standard DIN 52183. After the last measurements of the weight changes, the samples were dried at 103°C until there was a constant weight. The five tropical hardwoods had low sorption values recorded and high sorption values for the European species and this could be attributed to differences in the microstructure of these woods.

Basic density, extractive content and moisture sorption properties of Pinus pinaster wood infected with the pinewood nematode, Bursaphelenchus xylophilus

The pinewood nematode（PWN）, Bursaphelenchus xylophilus, has become one of the most severe threats to pine forest worldwide. Nematodes, migrating through resin canals and feeding on the living cells, induce rapid metabolic changes in ray parenchyma cells, create cavitation areas, decrease xylem water content and oleoresin exudation, and cause necrosis of parenchyma and cambial cells. This study focused on the impact of PWN infection on technological parameters of wood and evaluated the impact of anatomic and biochemical incidences of tree defense reactions on basic density, extractive content and moisture sorption properties of Pinus pinaster wood.Samples of infected and uninfected wood were studied.The presence of nematodes reduced wood basic density by2 % and decreased the total content of extractives in infected wood as compared with uninfected（5.98 and8.90 % of dry wood mass, respectively）. Extractives in infected trees had inverse distribution along the trunk as compared with uninfected trees. The adsorption isotherms for infected and uninfected wood had similar positioning.We recorded differences（some statistically significant） in the equilibrium moisture content of infected and uninfected wood under varying environmental conditions. Despite the verified differences in wood basic density, extractive content and moisture sorption properties, the overall conclusion is that the PWN had a slight impact on these characteristics of wood.

Moisture sorption and thermodynamic properties of Camellia oleifera seeds as influenced by oil content

Moisture sorption isotherms and thermodynamic properties of Camellia oleifera seeds as influenced by oil content were investigated.Moisture desorption and adsorption isotherms of Camellia oleifera seeds,kernels and shells from three varieties were determined using constant temperature and humidity chamber method at different temperatures(10°C,25°C,and 40°C)with water activity ranging from 0.20 to 0.90.Six selected mathematic models were employed to fit the experimental data.The Peleg model gave the best results for both seeds and kernels and Langmuir model was the best for shells.The difference of equilibrium moisture contents at the same water activities during desorption and adsorption indicated the occurrence of hysteresis of adsorption processes and the equilibrium moisture contents tended to decrease with the increasing oil content and temperature.The binding energy and average capacity per unit mass decreased with increasing temperature and oil content.The relationships between water activity and the logarithm of sorption activity showed the capillary porous body characteristics of the seeds.

Moisture sorption characteristics of full fat and defatted pistachio kernel flour

The sorption isotherms of full-fat(FPKF),partially defatted(PDPKF),and totally defatted(TDPKF)pistachio kernel flour were performed in the range of water activity(aw)from 0.113 to 0.859 at 15℃,25℃and 35℃,and the applicability of six mathematical models(Smith,Oswin,Henderson,GAB,Halsey and BET)in data prediction was evaluated.Sorption isotherms were typeⅡ,according to Brunauer’s classification.Equilibrium moisture content(EMC)increased with an increase in aw at constant temperatures.The sorption isotherms of all three flour samples exhibited hysteresis.Significant differences were found among equilibrium data of FPKF,PDPKF and TDPKF samples.TDPKF showed higher hygroscopic characteristics than PDPKF,and PDPKF showed higher hygroscopic characteristics than FPKF at any temperature and aw studied.It was found that the Smith model was the most satisfactory one for representation of the sorption data of full fat sample,but for defatted samples,Halsey was the best model.The average monolayer moisture content(MMC)calculated by GAB model were 2.443-3.781 g/100 g(d.b.),3.585-4.886 g/100 g(d.b.)and 5.093-6.918 g/100 g(d.b.)for FPKF,PDPKF and TDPKF,respectively.The isosteric sorption heat(Qst)calculated by means of Clausius-Clapeyron equation decreased with increasing moisture content.The Qst values were 44.76-74.67 kJ/mol,44.75-99.44 kJ/mol and 44.80-133.28 kJ/mol for FPKF,PDPKF and TDPKF,respectively,in the range of moisture content of 2%to 41%(d.b.)at 25℃.

Experimental study of the isothermal sorption properties of late Qing and 1980s grey bricks in Wujiang, Suzhou, China

Grey brick is a key material in Chinese traditional architecture. The isothermal sorption curve of grey bricks is one of the basic moisture characteristics for studying the heat transfer of brick building enclosure structures and is also a fundamental parameter of research into the degradation mechanisms of Chinese traditional architecture. In this study, we measure the isothermal sorption curves of Wujiang （Suzhou, China） bricks from the 1980s and the late Qing period, by applying constant relative humidity controlled by saturated salt-water solutions under isothermal conditions. We then present their fitting formulas for humidity bound ranges of 5-92%. The results indicate that samples of the same-area traditional Suzhou grey bricks from different time periods show relatively large differences in their isothermal sorption properties, with the isothermal sorption property values of the late Qing grey bricks about three times those of the 1980s grey bricks.