新型太阳能干燥装置在枸杞烘干中的应用

本文简要地介绍一种新型太阳能枸杞干燥装置结构形式。通过太阳能热利用原理计算推导出在太阳能集热器上的辐射强度,根据经验公式算出所需的集热器有效面积,通过实测得出每千斤枸杞所配置最佳面积。     

Computerised control system for an experimental solar lumber dryer

The microcomputer based control system employed in an experimental highly efficient solar kiln and the advantages of using this approach in solar wood drying are discussed. The control system consisting mainly of a personal computer and a data acquisition unit, performs a number of measuring and control functions. The monitored drying variables are wood M.C., collector's temperature, kiln's temperature, and R.H. The M.C. is monitored by recording the weight of the 3.2 m³ timber stack, resting on a weighbridge. The direct and continuous monitoring of timber moisture and equilibrium moisture employed by the control system, makes it possible to run the solar drying process to a target value formed from these two measured drying variables (drying gradient). The developed control system is compared with a semiautomatic system controlling the same solar klin.     

试验型太阳能锯材干燥窑的计算机控制系统

本文讨论试验型高效太阳能干燥窑采用微机控制系统和探讨利用太阳能干燥的优点.控制系统主要包括个人计算机和一个数据采集装置,执行大量的测量和控制功能.监测的干燥变量有木材含水率、收集器温度、干燥窑温度和相对湿度.记录放在地磅上3.2m3的木材堆垛的重量以监测含水率.木材湿度和平衡温度的连续监测采用控制系统,使它在太阳能干燥运转过程中达到两个测量干燥变量(干燥梯度)的目标值.开发该控制系统与相似的太阳能干燥窑的半自动系统控制相比较.     

Quality of cocoa beans dried using a direct solar dryer at different loadings

In this study fermented cocoa beans were dried in a direct solar dryer at three levels of loading (20, 30 and 60 kg). Surface mouldiness was found to be heavy in the 60 kg treatment, with beans appearing blackish. All the dried beans were reasonably acceptable in terms of vinegary odour and weak in alcohol odour. Weak odour was also detected for the faecal, rancid and cheesy odours. The 60 kg treatment was rated strong for wet sock odour due to poor drying condition. A significant difference (P < 0.05) was found between the 60 kg treatment and the lower loading treatments for pH and titratable acidity. A cut test showed that the lower loading treatments resulted in a higher percentage of brown beans. The 20 kg treatment showed the highest cut test score, which is significantly different (P < 0.05) from the 60 kg treatment. Fermentation index also showed a tendency for lower loading treatments to have a higher index. No significant difference (P > 0.05) was found among the treatments in terms of cocoa, astringency, bitterness and sourness flavour notes. However, better flavour was observed for beans from the 20 kg treatment. No mouldy off flavour was found in any of the dried beans. Overall quality assessment showed that the 20 kg treatment was able to produce reasonably good‐quality beans as compared to other loadings and therefore is recommended for the direct solar dryer. Copyright © 2006 Society of Chemical Industry     

无核紫葡萄太阳能干燥技术的研究

采用一种空气集热器-温室型太阳能干燥装置,在新疆石河子市的气候条件下验证了无核紫葡萄太阳能干燥的可行性,从2007年8月到10月间,进行了一系列的试验.试验表明:与自然晾晒相比,太阳能干燥周期缩短为原来1/3的时间,干燥质量也有大幅度的提高.     

Effectiveness of the solar biomass hybrid dryer for drying and disinfestation of maize

The Solar Biomass Hybrid Dryer (SBHD) is a new technology developed in Ghana for grain drying and utilizes biomass (agro-residues, timber scraps, etc.) along with solar drying, and is especially useful for drying during rainy periods of the year when solar drying cannot be relied on. This study assessed the effectiveness of a 5.0-MT SBHD comprising a solar tent and a furnace for thermal drying and disinfestation of maize. Mortalities of adults of Sitophilus zeamais (Motschulsky), Tribolium castaneum (Herbst) and Cryptolestes ferrugineus Stephens were assessed. Additionally, mortalities of immatures of these three species were assessed. Internal and cage temperatures (°C) in the SBHD, sun drying (SD) and laboratory (control) were monitored, as were moisture content (MC) and thermally (stress) damaged kernels (TDK) (%). During the 7-h experiment, mean internal temperatures in the SBHD, SD and laboratory were 52.3 ± 1.0 °C, 41.4 ± 0.8 °C and 30.3 ± 0.2 °C, respectively. Similarly, temperatures in cages in the SBHD (49.5 ± 1.0 °C) were higher than those for cages in the laboratory (29.9 ± 0.2 °C) and SD (38.2 ± 0.6 °C). Reduction in the moisture content of maize dried using SBHD, SD and under laboratory conditions were 7.7, 5.2 and 2.9%, respectively. This corresponded to grain MC reduction rates of 1.1%, 0.74% and 0.4% per hour. There was 100% mortality of S. zeamais and C. ferrugineus adults achieved in only the SBHD; some immatures of all three species survived in all three treatments. However, survival of immatures was highest in the laboratory, followed by SD and lowest in the SBHD for all three species. Percent TDK was higher in the SBHD (6.7 ± 0.9) than SD (3.3 ± 0.3) and laboratory (2.7 ± 0.3). These data show that the SBHD is effective for both drying and disinfestation of grain.     

Drying of red pepper slices in a solar greenhouse dryer and under open sun: Experimental and mathematical investigations

The present work is mainly focused on the study of the solar drying of red pepper grown in the North of Tunisia. A new mixed mode solar greenhouse dryer (SGD) with forced convection was used in the drying experiments. To further understand the characteristics of the SGD, an open sun drying experiment was conducted under the same climatic condition. The results show that the constant rate period is absent from the experimental drying curves. The experimental drying curves show only the falling rate period. Thus, the drying time which was three days in the open sun decreased to two days in the SGD. The drying data were fitted to eight different mathematical models. The fit quality of the proposed models was evaluated by using the coefficient determination (R²), reduced chi-square (χ²) and root means square error (RMSE). Among the models, Modified Henderson and Pabis model for the forced solar drying and the open sun drying was found to best explain the thin-layer drying behaviour of pepper slices. The instantaneous thermal efficiency of the solar collector varied between 30% and 80%, at a mass flow rate of 0.047 kg/s. The overall energy efficiency of the solar dryer was 34%. Finally an economic evaluation was calculated using the criterion of payback period which was found very small 1.02 years compared to the life of the dryer (SGD) 20 years.     

新型微波真空干燥机设计

设计了一种集微波干燥与真空干燥于一体的新型装置,将波导和波源冷却装置融为一体,有效地解决了微波分布不均和微波源受热易损坏两大难题。物料室是微波室和真空室的交集,可以使物料既能受到微波辐射,又能处于真空环境中。分层设计的物料盘一方面可以方便拆卸,另一方面可以充分地利用物料室的空间。模块化的冷阱设计,使冷阱可以根据干燥的需求自由的装卸,可以有效地提高冷阱的利用效率。该微波真空干燥设备设计巧妙,安全可靠,可以满足高品质物料的干燥加工。     

Freeze-drying in a fluidized-bed atmospheric dryer and in a vacuum dryer: Evaluation of external transfer coefficients

The factors which influence freeze-drying are classified as either internal or external. Internal factors derive from the properties of the material undergoing drying, while external factors relate to the physical conditions under which drying occurs. This paper looks at the external factors and compares them for two different freeze-drying methods: a vacuum dryer and an atmospheric fluidized-bed dryer containing an adsorbent.First, the ratio between the external heat and mass transfer coefficients, h/K, was evaluated: this ratio for the fluidized-bed dryer was constant at 398·8 kcal torr kg⁻¹ °C⁻¹ but varied for the vacuum dryer within the range 9·5 to 16·2 kcal torr kg⁻¹ °C⁻¹. The individual heat and mass transfer coefficients were calculated. The mass transfer coefficient, K, for the vacuum dryer was 1·0 kg h⁻¹ m⁻² torr⁻¹; for the atmospheric fluidized-bed dryer, K varied slightly with temperature, being 0·7, 0·8 and 1·0 kg h⁻¹ m⁻² torr⁻¹, at fluidized-bed temperatures of 0, −10 and −20°C, respectively. At these temperatures, the heat transfer coefficients for the fluidized-bed dryer were 287, 321 and 402 kcal h⁻¹ m⁻² °C⁻¹, respectively. For the vacuum dryer h was 9·5–16·2 kcal h⁻¹ m⁻² °C⁻¹. Thus, K values were comparable in the two drying systems but h in the fluidized-bed dryer was some 20–40 times greater than in the vacuum dryer.The study helped to elucidate the mechanisms involved during ice sublimation and contributed towards developing a means by which freeze-drying patterns could be predicted. The results were helpful in providing guidelines during the development of the novel atmospheric fluidized-bed technique.