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为探索出不同真空微波干燥条件对胡萝卜恒速干燥速度和临界含水量的影响,选取微波功率Q、负载量M、切片厚度δ等因素,范围分别在300~500W、80~140g、4~8mm,以临界含水量和恒速干燥速度为目标在0·08MPa真空条件下进行实验。实验结果表明:随着微波功率从300W增加到500W时,恒速干燥速度提高了87·5%;随着负载量从80g增加到140g时,恒速干燥速度降低了50%;随着切片厚度从4mm增加到8mm时,恒速干燥速度提高了81·3%。临界含水量仅与负载量显著相关,随着负载量从80g增加到140g时,临界水分含量从5·4kg/kg降低到2·2kg/kg。根据实验数据,采用线性回归的方法,得到恒速干燥速度U及临界含水量Xc的数学模型为:U=45·558+0·346Q-1·431M+17·636δ;Xc=14·962-0·080M-0·400δ。 相似文献
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This paper describes an experimental investigation of the drying behaviour and conditions of pumpkin slices via a convective cyclone‐type dryer. Drying experiments were conducted at air inlet temperatures of 60, 70 and 80 °C and air velocities of 1 and 1.5 m s?1. Samples of 200 g of cylindrical pumpkin slices (thickness 5 mm × diameter 35 mm) were arranged in a single layer on each of two trays. The least squares method was applied to derive the drying curve equation of samples. During the experiments the following parameters were measured: weight loss, temperature, relative moisture and velocity. From these parameters, dimensionless mass loss, moisture content, mass shrinkage and drying rate of samples were calculated and are discussed in detail. Additionally, the transport of water during dehydration was described by the diffusion mechanism, and Fick's equation was used for evaluation of the experimental data. The linear sections of drying curves were analysed by linear regression to obtain the moisture diffusivities. It was found that pumpkin slices would dry perfectly within 340–720 min under these drying conditions. The convective cyclone dryer could also be used to dry other products. Thus it is expected that this new dryer will help farmers and producers to reduce the cost of drying. Copyright © 2003 Society of Chemical Industry 相似文献
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对方便米线在多层带式干燥设备干燥过程的研究 总被引:1,自引:0,他引:1
以应用于方便米线生产实际的某型号多层带式干燥设备为研究对象,在生产现场对干燥设备的温度、湿度及方便米线干燥过程水分含量变化进行测试,考察方便米线的实际干燥条件和干燥过程及其可能对方便米线产品质量的影响。结果表明:干燥设备内温度、湿度变化较大并存在一些局部的高温低湿和低温高湿区域,造成米线水分在总体逐步降低的趋势下有较大的波动,这不仅不利于干燥的有效进行,而且当其波动幅度超过一定限度还有可能引起米线产品产生裂纹并断裂。 相似文献
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目的:考察不同水分烟丝在薄板干燥工序中对同一规格不同批次颗粒赋香卷烟中试样品致香物质组成及含量的影响。方法:采用静态顶空—气相色谱质谱(HS-GC/MS)联用法,对中国市售两个不同批次(A、B)颗粒赋香卷烟(品牌H)样品在不同水分影响下的致香成分进行分析测定。结果:① 当烟丝水分为15%时,A批次样品鉴定出38个化合物,B批次样品鉴定出37个化合物;② 当烟丝水分为15%时,致香成分的数量和含量最多,12%时次之;③ 赋香卷烟感官评吸分数与挥发性成分相对含量检测结果一致。结论:在卷烟薄板干燥工序过程中烟丝水分设定为15%,有助于提升颗粒赋香卷烟香气品质,同时降低杂气和刺激性。 相似文献
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目的:实现南极磷虾旋转闪蒸干燥过程的控制。方法:对南极磷虾在120~180℃范围内进行干燥试验,选取常用的6种干燥模型对试验数据进行拟合,进一步采用回归分析建立干燥模型常数项与温度的方程,得到干燥模型表达式并进行验证。根据Fick第二定律方程计算得到南极磷虾干燥水分扩散系数。结果:干燥温度对干燥热效率和干燥速率的影响显著,干燥温度为130~180℃的南极磷虾干燥曲线均为降速干燥阶段。Page模型适合用来描述和预测南极磷虾旋转闪蒸干燥过程,回归分析得到模型常数项方程为k=exp(-27.532 1+0.301 8T-8.538 2×10-4T2)、n=14.010 6-0.157 67T+4.750 9×10-4T2。随着温度的升高,南极磷虾有效水分扩散系数从2.539 35×10-7 m2/s升高到13.889 64×10-7 m2/s。结论:采用旋转闪蒸干燥方式可以有效保护南极磷虾中的热敏性成分不被破坏,提高产... 相似文献
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Gravimetric absorption test system (GATS) is used to measure the absorption capacity, absorption rate and drying rate of knit hoses, prepared from different fibres. The fibres studied are cotton, polyester and variety of modified polyesters. The study has shown that desorption or drying rate is at least two orders of magnitude lower than absorption rate. This finding implies that drying is the limiting process in moisture management. Further experiments on knit fabrics made from polyester and cotton, show that the drying rates are independent of fibre type in the constant-rate period, while the drying rates in the falling-rate period are dependent on fibre type. Subsequently, it is shown on the polyester fabric that drying rate in the falling-rate period depends on water concentration. Based on this understanding, an approach for enhancing drying rate in the falling-rate period is defined. The approach is demonstrated on knit hoses prepared from cotton and polyester yarns in alternating stripe form. The drying rate in the falling-rate period is found to be higher in the polyester-cotton stripe knit hose. A hypothesis for the observed enhancement in drying rate by wicking is put forth in terms of the internal movement of water from polyester to cotton portion. Experimentally, it is shown that 16% improvement in drying time is achieved in the case of the polyester–cotton stripe samples. Further, indications of internal water movement from polyester to cotton portion have been obtained by tracking the surface temperatures of the knit hoses during drying by infrared (IR) thermography. 相似文献
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目的 研究南美白对虾中短波红外干燥(medium-short-wave infrared drying, MSWID)特性及其干燥模型拟合。方法 在不同温度下(50、60、70℃)对南美白对虾进行干燥试验,并以热风干燥(hot air drying, HAD)为对比。采用8种常用干燥模型对试验数据进行非线性回归拟合,确定最佳干燥模型,并对干燥模型进行验证。并进一步分析不同温度下南美白对虾有效水分扩散系数和干燥活化能。结果 南美白对虾MSWID过程中,干燥温度对干燥过程影响显著,提高干燥温度可提高干燥速率,加快干燥进程。比较模型评价指标发现,Two-term exponential模型可以很好的拟合南美白对虾干燥数据,模型预测值和试验值误差仅为2.09%,可较准确的预测干燥过程中南美白对虾的水分变化规律。二阶多项式回归方程可预测水分比随干燥温度和时间的变化。随着干燥温度的升高,MSWID和热风干燥的有效水分扩散系数分别从2.3721×10-9 m2/s、2.3027×10-9 m2/s升高到3.402... 相似文献
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红薯叶粉热泵-热风联合干燥工艺优化 总被引:5,自引:0,他引:5
为保证红薯叶粉品质,降低加工能耗,采用热泵-热风联合干燥技术对红薯叶进行处理,在单因素试验基础上运用Box-Behnken Design优化试验,研究热泵干燥温度、热风干燥温度和转换点含水率对单位能耗、叶绿素含量、色泽L*值和吸湿性的影响,通过加权综合评分法推导多项式回归模型,进而优化联合干燥工艺参数。经响应面优化的干燥参数为:热泵干燥温度52℃、热风干燥温度73℃、转换点含水率58%,该工艺下单位能耗3 621. 36 k J/g、叶绿素含量6. 42 mg/g、色泽L*值46. 21、吸湿性7. 19%,综合评分值与预测值拟合度高达99. 632 5%,为红薯叶综合利用奠定了理论基础。 相似文献
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Tadao Inazu Ken-ichi Iwasaki & Takeshi Furuta 《International Journal of Food Science & Technology》2005,40(6):621-630
The distribution of stress during drying of fresh Japanese noodle (udon) was investigated by mathematically modelling the changes in shrinkage and other mechanical properties, this allowed crack formation to be predicted. It was observed that the shrinkage coefficients were nearly the same in all three directions with changing moisture content, and the degree of shrinkage was independent of the temperature. The Young's modulus, yield stress and fracture stress could be expressed as exponential functions of moisture content. Changes in stress distribution during drying were calculated by coupling the moisture transfer equation with the constitutive equation using a finite element method. The calculated stress distribution indicated that a rapid drying rate causes extensive internal tensile stress in udon. The scheme used in the present study was found to effectively represent the potential for crack formation along the central axis, this was shown to be consistent with the actual cracking pattern. 相似文献
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本研究将收获的高水分稻谷分别放置于自制的就仓干燥模拟仓内,研究通风量分别为80、92、104m3/h条件下处于仓内底部、中部、表层的稻谷水分迁移规律。应用8种常用干燥模型对实验数据进行非线性回归拟合分析,确定最适干燥模型,并对模型进行了验证。结果表明:稻谷各层水分比随着通风干燥时间的延长而呈下降趋势,其中最底层稻谷水分比最小,底层稻谷在前期(2 d内)水分迅速下降,后期下降速度逐渐平缓,而上层稻谷水分比依次增大,降水速率较下层相对较慢;稻谷有效水分扩散系数在0.092~0.43×10-3 m2/d,其中80 m3/h通风条件下,粮堆各层水分有效扩散系数均小于其他两种通风条件;而相同通风条件下,稻谷粮层距粮面60~90 cm范围内,扩散系数相对其他层较大。通过对比模型得到的预测值与实测值,确定Wang et al.模型为通风条件下稻谷各粮层水分扩散系数的预测模型。 相似文献
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In this study, drying behavior of viscose yarn bobbins was investigated experimentally to specify the optimum drying conditions and a drying model was proposed for simulation of drying. The experiments were conducted in a pressurized hot-air bobbin dryer, which was designed and manufactured based on the dryers used in the textile industry. Drying process was performed for various drying parameters: bobbin diameter, drying temperature, drying pressure, and volumetric flow rate of drying air. The results show that total drying time is strongly dependent on drying pressure, drying temperature, and volumetric flow rate and increase at these parameters shortens the drying time considerably. The results also show that the minimum energy consumption is for lower values of drying temperature and drying pressure and modest and higher values of volumetric flow rate. Simulation results show that the most appropriate model in describing the drying curves of viscose yarn bobbins is the stretched exponential model. 相似文献