对早期Barmag公司设备及配套装置的改造

1　切片干燥系统的改造BM公司的干燥设备 ,采用传统的蒙特斯自动空气干燥法 ,主要的核心部件为氯化锂转轮 ,在空气湿度大时 ,氯化锂转轮的吸附除湿负荷增大 ,其氯化锂吸附剂长时间处于饱和状态 ,导致转轮除湿能力下降 ,使热风干燥后的切片含水高达 4 0μg/g以上 ,严重时转轮中氯化锂失效而无法再生。为了彻底地解决问题 ,工厂将转轮除湿系统改造为分子筛除湿系统 ,该系统具有大风量、低露点(可达 - 6 0℃ )、低能耗的特点 ,投入使用后 ,切片的含水一直保持在 2 5μg/g以下。2　空调逆风和回风系统的改造原空调系统有两路送风 ,一是用于卷绕…     

鱿鱼热泵-热风联合干燥节能研究

以热泵干燥阶段的温度、分阶段干燥的水分转换点、后期热风干燥阶段的温度为影响因素,以单位能耗除湿值（SMER）和总挥发性盐基氮值（T—VBN）两者的综合指标Y为最终评价指标进行响应面优化分析,得出了联合干燥最佳工艺参数：热泵干燥温度（X1=54．3℃）、水分转换点（X2=32．3％）和热风干燥温度（X3=43．5℃）。在最优工艺条件下比较HPD、HPD＋AD、AD三种干燥方式下的样品品质和耗能,联合干燥得到的鱿鱼干品质高于热风干燥,而且降低了干燥能耗38．67％。     

高温热泵在除湿转轮空调系统中的性能

提出一种新型的除湿转轮与高温热泵联合运行的空调系统,该系统利用热泵的蒸发器对除湿后的热空气进行降温处理,同时将冷凝器释放的热量为除湿转轮提供再生能耗,在系统内部实现冷量和热量的抵消,既降低系统能耗又减少环境污染。为此研制了采用工质R142b的空气源热泵,将机组置于可模拟转轮处理空气和再生空气状态的标准空气焓差室对其性能进行测试。通过改变室外侧环境温度和进入冷凝器的风量研究R142b在空气源热泵机组中的循环性能和排气压力。结果表明：当蒸发器环境温度为（45±0.2）℃时,冷凝器进风温度为（27±0.2）℃时,灌注R142b的空气源热泵可产生79.2℃的热风,满足转轮的再生温度要求,且排气压力在压缩机的正常工作压力范围内。     

热管空气回热器在热泵木材干燥机上的应用

在热泵木材干燥机上热管空气回热器可以利用从热泵蒸发器出来的低温冷空气来预冷进蒸发器前的空气，使得空气在蒸发器中除湿能耗比ＳＰＣ在空气温度为５０℃、相对湿度为８０％时从原来的０．４１ｋＷｈ／ｋｇ水降低为０．３２ｋＷｈ／ｋｇ水，每去除１ｋｇ水比原来节电２４％，木材干燥周期短，不易开裂。     

用BM公司干燥系统的技术改造

针对引进 BM公司干燥系统冷冻降湿设备老化 ,干空气露点高 ,切片可纺性差的生产状况。采用分子筛吸附除湿技术对进风系统进行改造后 ,干燥系统新风露点降到 -5 0℃以下 ,干切片含水率小于5 0μg/g,能耗明显下降 ,生产成本降低     

热泵干燥过程中低温热泵补热的应用分析

针对木材干燥中的不利工况,提高干燥系统的可靠性,根据两级压缩制冷循环原理,提出了低温热泵和干燥热泵的耦合应用方案。使用能量的?损失模型,分别对干燥系统进行热量、干燥介质的质扩散和除湿过程的?损失进行分析。在低温热泵20、22、24、26、28、30℃以及关闭低温热泵的供热情况下分别测试计算了干燥热泵压缩机的排气温度与能耗、热泵性能系数(COP)以及热力完善度,同时测得木材含水率下降1%,系统的干燥用时和能耗。结果表明:相比于关闭低温热泵,开启低温热泵后干燥热泵的排气温度最多减少了16℃,COP皆有所提高。由于主机室温度升高后,系统循环的不可逆程度增加,热力完善度随着供热温度增加逐渐降低。开启低温热泵后干燥热泵的供热量和用时比关闭低温热泵最大分别增加44%,减少46%。     

热泵干燥过程中低温热泵补热的应用分析

针对木材干燥中的不利工况,提高干燥系统的可靠性,根据两级压缩制冷循环原理,提出了低温热泵和干燥热泵的耦合应用方案。使用能量的（火用）损失模型,分别对干燥系统进行热量、干燥介质的质扩散和除湿过程的（火用）损失进行分析。在低温热泵20、22、24、26、28、30℃以及关闭低温热泵的供热情况下分别测试计算了干燥热泵压缩机的排气温度与能耗、热泵性能系数（COP）以及热力完善度,同时测得木材含水率下降1%,系统的干燥用时和能耗。结果表明：相比于关闭低温热泵,开启低温热泵后干燥热泵的排气温度最多减少了16℃,COP皆有所提高。由于主机室温度升高后,系统循环的不可逆程度增加,热力完善度随着供热温度增加逐渐降低。开启低温热泵后干燥热泵的供热量和用时比关闭低温热泵最大分别增加44%,减少46%。     

一种衣物空气低温烘干循环系统的设计及分析

基于机械热泵除湿原理,同时结合洗衣机衣物烘干温度的要求,设计出一种衣物空气低温烘干循环系统。借助EES软件对该系统建立系统模型,通过理论模拟分析研究其热力学性能,并对影响其热力性能的关键操作参量影响进行分析。研究结果表明,在保证冷凝量均为1.02 kg/h的情况下,该设计系统的单位能耗除湿速率（moisture extraction rate,MER）为0.5018 kW?h/kg,较常规电加热热风烘干系统降低了16.5%;COP为0.79,较常规烘干系统提高了16.5%。此外,相比较常规电加热热风烘干系统方案烘干温度90 ℃,该方案设计的滚筒操作温度仅为57.68 ℃,有效地拓展了可烘干衣物的范围。     

逆流填料式溶液除湿器的数值模拟和实验研究

对溶液除湿的除湿器中传热传质进行了热力学分析,根据除湿塔的结构及溶液与空气的流动方式,建立除湿器的热质交换物理和数学模型,模拟计算除湿器入口空气和溶液参数对除湿器出口空气参数的影响,模拟计算中设置入口空气流量0～5kg/s,入口空气温度20～40℃,入口空气含湿量为10～30g/kg,入口溶液温度25～40℃,入口溶液浓度25%～40%,入口溶液流量1～4kg/s,得到各入口参数对出口空气含湿量和温度的影响曲线。结果表明:入口空气含湿量、入口溶液浓度和温度对出口空气含湿量影响显著;入口空气含湿量和流量对出口空气温度影响显著。对模拟结果与实验结果进行了比较,发现两者的变化趋势是相同的,最大误差为13.08%。     

切片干燥分子筛除湿初探

通过对四种空气除湿方法(冷冻除湿、压缩除湿、吸湿剂除湿和吸附剂除湿)的分析比较,着重介绍了日本钟纺公司除湿装置的设备结构、工艺流程与技术特征,并就切片干燥中分子筛的除湿设计作了初步探讨。除湿装置的设计主要分吸附干燥和脱湿再生两个部分:吸附干燥部分的设计主要要确定吸附剂的充填量,用动态吸附量来计算较准确;脱湿再生部分需要通过热平衡计算来确定再生空气的风量和温度。     

Drying Kinetics and Antioxidant Phytochemicals Retention of Salak Fruit under Different Drying and Pretreatment Conditions

Kinetics of hot air drying and heat pump drying were studied by performing various drying trials on salak slices. Isothermal drying trials were conducted in hot air drying and heat pump drying at a temperature range of 40–90°C and 26–37°C, respectively. Intermittent drying trials were carried out in heat pump drying with two different modes: periodic heat air flow supply and step-up air temperature. It was observed that the effects of relative humidity and air velocity on drying rate were significant when moisture content in salak slices was high, whereas the effects of temperature prevailed when the moisture content was low. As such, it was proposed that drying conditions should be manipulated according to the moisture transport mechanisms at different stages of drying in order to optimize the intermittent drying and improve the product quality. Generally, loss of ascorbic acid during drying was attributed to thermal degradation and enzymatic oxidation, whereas the loss of phenolic compounds was mainly due to thermal degradation. Experimental results showed that heat pump drying with low-temperature dehumidified air not only enhanced the drying kinetics but produced a stable final product. Heat pump–dried samples retained a high concentration of ascorbic acid and total phenolic compounds when an appropriate drying mode was selected.     

Kaffir Lime Leaf (Citrus hystric DC.) Drying Using Tray and Heat Pump Dehumidified Drying

Desorption isotherms of mature kaffir lime leaves are determined and a nonlinear regression program was applied to the experimental data to fit with any of the four moisture sorption isotherm models. It was found that the modified Halsey model could fit the best. Tray and heat pump–dehumidified drying of kaffir lime leaves were conducted and it was found that the modified Page model was the most effective one. The drying constant was fitted to drying air temperature using the Arrhenius model. Effective moisture diffusivities were determined using the drying data. Heat pump–dehumidified drying reduced drying time and provided dried kaffir lime leaves with higher amount of citronellal than tray drying.     

The Effects of Predrying Treatments and Different Drying Methods on Phytochemical Compound Retention and Drying Characteristics of Moringa Leaves (Moringa oleifera Lam.)

The most appropriate maturity stage of Moringa oleifera leaves was selected for drying based on phytochemical content, including quercetin and kaempferol. Desorption isotherms were developed and were best fit by the modified Henderson model. Prior to drying, samples were left untreated, blanched in boiling water, and blanched in NaHCO₃/MgO. The leaves were dried by hot air tray drying (TD) and heat pump–dehumidified drying air (HPD) at air temperatures of 40, 50, and 60°C. Alternatively, leaves were subject to microwave drying (MWD) at 150, 450, and 900 W and to freeze drying (FD). The moisture versus time data were fitted to five drying models. In general, a three-parameter model gave the best fit. The drying constant was related to the drying temperature or microwave power using an Arrhenius model. Effective moisture diffusivity (D _eff) increased with higher drying temperature, higher microwave power, or blanching treatments. Structural changes in the leaves after drying and upon rehydration were observed by scanning electron microscopy (SEM). Leaves blanched and dried using HPD at 50°C and fresh and dried using FD showed a partial breakdown of the tissue structure upon rehydration. HPD and blanching reduced the drying time by 8.3% and increased quercetin and kaempferol levels by 42.1 and 51.4%, respectively, compared to TD at 50°C. MWD provided the quickest drying followed by HPD and TD, respectively. HPD drying of M. oleifera after blanching resulted in relatively greater quality compared to TD and MWD.     

Study and comparison of different drying processes for dehydration of raspberries

The aim of the present study was to evaluate and compare different drying methods (microwave, hot air?+?microwave, and osmotic dehydration?+?microwave) in raspberries (cv. Heritage). A portion of raspberries was pretreated with osmotic dehydration (60°Brix sucrose solution at 20°C for 360?min) and another with hot air drying (HAD) (1.5?m/s air speed at 60°C for 300?min). Pretreated raspberries were then dried by microwave and at three different intensities (3.5, 7.5, and 11?W/g). Physicochemical properties (moisture content, water activity, and drying rate) and quality parameters (optical properties, mechanical properties, antioxidant capacity, and rehydration capacity) of dried raspberries were evaluated. Results showed that the microwave drying (MWD) at 7.5?W/g (50?min and final temperature of 79?±?5.1°C) allowed a high yield of dried raspberries. The combined processes were not efficient to accelerate the decrease of moisture content, due to the low drying rate of the pretreatments. In terms of quality, none of the drying processes allowed a high retention of the antioxidant capacity. However, they allowed an appropriate rehydration performance. The combination of HAD with MWD allowed obtaining a good appearance and desirable texture on the dried product. Thus, this last option seems to be the best among the drying methods tested, but additional studies are required to improve the efficiency of the process and the effect on the antioxidant capacity during drying.     

Effect of Different Drying Methods on the Microwave Extraction of Phenolic Components and Antioxidant Activity of Highbush Blueberry Leaves

In the last few decades, researchers have found blueberry leaves to be an interesting source of different phenolic compounds, and drying is an important part of their postharvest and sample preparation processes. In the current study, blueberry leaves were dried using microwave-assisted hot air drying or hot air drying alone at 45, 60, and 75°C to 10–15% wet basis. Corresponding drying characteristics were determined by fitting the moisture ratio obtained in each case with eight theoretical and semitheoretical models for hot air and microwave drying stages. It was observed that best fitting drying models for blueberry leaves depended not only on the nature of the biomaterial but also on the method of drying and the temperature of drying. Phenolic content, monomeric anthocyanin content, and the corresponding antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition activity and ferric reducing ability of plasma (FRAP) activity were evaluated for the leaf extract obtained following microwave extraction of the dried samples obtained using the above-mentioned drying methods and were compared to the corresponding bioactive compositional characteristics of freeze-dried blueberry leaves. It was observed that the freeze-dried sample had the highest content of total phenolics and total monomeric anthocyanins along with high antioxidant activity. Furthermore, extracts obtained from the microwave-dried leaf samples obtained with a drying temperature of 60°C had highest total phenolic content and highest total monomeric anthocyanin content among all other drying methods and the extract had an antioxidant activity similar to the freeze-dried blueberry leaf samples, implying that microwave drying at 60°C is a potential alternative to freeze drying for preservation of the phenolic components and antioxidant activity of dried blueberry leaves.     

COMPARISON OF TIMBER DRYING USING SOLAR ENERGY,ELECTRICAL HEATING AND DEHUMIDIFIER.

ABSTRACT

The performance of three different types of dryers for the hot air drying of sawn-limber planks are compared. These were the electric resistance dryer, solar dryer, and the dehumidifier dryer. Whilst the electric and solar dryers depended only upon hot air for drying, the dehumidifier dryer relied on hot dehumidified air. The results of investigations carried out on timber drying employing these three types of dryers in the Engineering Faculty are compiled and compared here in this paper. The results showed that the electric dryer produced the fastest drying lime and lowest moisture content, followed by dehumidifier drying. The solar dryer achieved a lower moisture content and a faster drying rate compared to natural drying, although the difference in drying times was marginal.     

侧进风盐泥干燥室的流场仿真及结构改进

为解决侧进风盐泥干燥室内干燥不均匀问题,采用数值模拟、实验研究的方法进行结构改进。基于标准k-ε模型和多孔介质模型对干燥室流场进行数值模拟,测量了风速及干燥后盐泥的含水率,根据结果对干燥室结构进行改进。结果表明：原结构干燥室内热风流动的动力来源主要依靠初速度,在干燥室内流动扩散并产生各种扰动,气流不均匀系数较大,干燥后的盐泥含水率较高且不均匀;改进结构后的干燥室内部形成的压力梯度成为热风流动的驱动力,使热风穿过盐泥层向上运动,气流不均匀系数小,干燥后的盐泥含水率低且较为均匀。对比原结构,改进结构后的干燥室内部气流不均匀系数至少下降27.6%,干燥后的盐泥含水率下降4.48%,含水率不均匀系数下降8.4%。     

Effect of Four Drying Methods on the Quality of Osmotically Dehydrated Cranberries

Partially dehydrated cranberries (osmotically dehydrated) were dried to low water contents using one of following four methods: hot air drying; microwave-assisted convective drying; freeze-drying; and vacuum drying. Quality evaluation was performed on all samples, including sensory evaluation (appearance and taste), texture, color, water activity, and rehydration ratio. Hot air drying produced dried cranberries with the best visual appearance while freeze-dried cranberries had the highest rehydration ratio. The other methods presented similar rehydration ratios. There was no significant difference in color measurements and water activity. Few differences in texture were found, except for freeze-dried cranberries, which had a lower toughness compared to the other drying methods including commercially available dried cranberries. Microwave-assisted to hot air drying rate ratios increased as the moisture content decreased.     

DRYING RATE AND TEMPERATURE PROFILE FOR SUPERHEATED STEAM VACUUM DRYING AND MOIST AIR DRYING OF SOFTWOOD LUMBER

Two charges of green radiata pine sapwood lumber were dried, either using superheated steam under vacuum (90°C, 0.2 bar abs.) or conventionally using hot moist air (90/60°C). Due to low density of the drying medium under vacuum, the circulation velocity used was 10 m/s for superheated steam drying and 5.0 m/s for moist air drying, and in both cases, the flow was unidirectional. In drying, stack drying rate and wood temperatures were measured to examine the differences between the superheated steam drying and drying using hot moist air.

The experimental results have shown that the stack edge board in superheated steam drying dried faster than in the hot moist air drying. Once again due to the low density of the steam under vacuum, a prolonged maximum temperature drop across load (TDAL) was observed in the superheated steam drying, however, the whole stack dried slower and the final moisture content distribution was more variable than for conventional hot moist air drying. Wood temperatures in superheated steam drying were lower.