共查询到18条相似文献,搜索用时 125 毫秒
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双行程红外辐射振动流化种子干燥的传热传质研究 总被引:2,自引:0,他引:2
在深入研究单行程红外辐射振动流化种子干燥的基础上,本文开拓出双行程振动流化干燥,其特点是在干燥过程中种子与供热热风均经两次行程,干燥装置总高度不变,其干燥行程增加20%.通过非稳态干燥动力学实验研究表明,增加内行程种子总脱水率增加87%,总干燥周期为单行程的1/1.8,料温为其0.82(47℃/57℃)倍.由于增加内筒使恒速段延长并提高了梅这段的干燥速率,整个干燥过程适应种子的生理生化特性,因而可保持种子的活力。文中根据干燥速率方程分别实验研究了辐射、对流与导热在强化种子传热传质过程中的各自贡献.这些研究为我国的‘种子工程’尤其是品种繁多、特性各异干燥难度较高的蔬菜种子干燥提供了理论依据与技术基础。 相似文献
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蔬菜种子的干燥动力学及其活性 总被引:8,自引:1,他引:7
本文研究了初含水率、干燥周期、料层厚度相同时,不同供热方式(热风、热风与辐射、热风与辐射并加湿)的白菜种子在固定床的干燥动力学及其活性,与传统的只热风供热相比,当干球温度相同时辐射加热风干燥的种子终含水率比低13.8%、发芽率比高0.3%,而辐射加热风并加湿干燥其终含水率比低5.8%,发芽率比高0.8%。为确保种子活力,建立了褚-杨白菜种子临界温度Tcv方程,并已验证其正确性.该方程为蔬菜种子干燥提供了理论基础并有重要的工程意义。 相似文献
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原流化床干燥实验装置没有布置气体分布板,使得床层内存在很大的死角,难以形成较佳的床内流场分布,导致学生做实验时所测得的临界含水率增大,干燥速率变小,干燥速度曲线恒速干燥阶段无法确定,鉴于此,采用双层直流式锥形孔气体分布板改进了原流化床干燥实验装置。经FLUNET数值模拟分析发现,经改进后,热空气在颗粒床层内分布的均匀性显著提高,其扩散范围明显扩大,流速更加趋于稳定,则进出口的速度差显著地降低了,减小为原实验装置的0.072倍,从而使热空气更均匀地干燥床层内的固体颗粒变色硅胶,可减小实验误差,提高实验结果的准确率。 相似文献
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对于种子干燥方面的研究,大多是针对其宏观传热传质即干燥动力学方面。本文采用热成象技术对单颗蚕豆种子的传热过程进行了研究,用实验求解导热方程反问题的方法计算出不同含水率下单颗种子的导热系数,对种子在非稳态下内部温度场进行了测试与分析.研究结果表明,在含水率小于 20%时,其导热系数随着含水率的增加而增大,当含水率大于 25%时则表现出较强的非均质性和非稳态性。对单颗蚕豆种子内部温度场测定而得到的种子热剖面温度分布表明,种子内部存在温度梯度其热扩散具有均匀性,同时反映出种皮传热热阻的存在。这些结果对于深入研究种子内部的传热传质机理,具有重要的实际意义。 相似文献
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加热方式对真空冷冻干燥热质传递机理的影响 总被引:5,自引:0,他引:5
1引言真空冷冻干燥(简称真空冻干)是多孔介质在低温低压下相变界面移动的耦合传热传质过程,其数学模型带有典型的非线性,难于精确求解[‘,2]。从应用上而言,真空冻干具有设备投资高,能耗大,干燥时间长的缺点。能量的供应即加热方式、升华水汽的流动条件、物料的输运性质是影响真空冻干性能的主要因素间。本文以牛肉的真空冷冻干燥过程为例,建立过程的非稳态数学模型,利用数值求解的结果,结合实验分析,研究了通过千层的辐射加热和通过冻结层的导热加热条件下真空冻干过程中传热传质的机理,分析了加热方式对缩短干燥时间的影响… 相似文献
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Compact multiframe blind deconvolution 总被引:1,自引:0,他引:1
We describe a multiframe blind deconvolution (MFBD) algorithm that uses spectral ratios (the ratio of the Fourier spectra of two data frames) to model the inherent temporal signatures encoded by the observed images. In addition, by focusing on the separation of the object spectrum and system transfer functions only at spatial frequencies where the measured signal is above the noise level, we significantly reduce the number of unknowns to be determined. This "compact" MFBD yields high-quality restorations in a much shorter time than is achieved with MFBD algorithms that do not model the temporal signatures; it may also provide higher-fidelity solutions. 相似文献
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蔬菜种子干燥中种皮的效应与优化传热传质机理 总被引:4,自引:1,他引:3
1前言含水率大的种子在贮存过程中极易发生劣变,使发芽力与发芽势降低山。种子干燥是一个复杂的传热传质过程,而且还涉及到生命力保存的问题。虽然种子的形态存有差异,但是种子的基本结构都是一致的。一般都由胚、胚乳和种皮三部分组成。种皮对种子具有保护与协调的功能,其透气性与透水性决定了种皮是种子与周围环境进行质量与能量交换的必经之路。为此本文综合种子的生物生理特性研究了蔬菜种子干燥中种皮的作用,并结合种皮的生物学功能探讨了优化传热传质的机理。2种皮对干燥的影响实验装置见文献[2],采用在线测量的方法可连续检… 相似文献
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Abstract This article presents a mathematical model approach to studying the drying phenomena of solid particle in a pneumatic (flash) dryer. The analysis is focused on the pneumatic momentum, mass, and heat balance of the solid particle when it moves inside the reactor. A fixed bed fluidization model was used to calculate the forces balance on the single solid particle. By solving mass and heat balance occurred in the particle, the water/liquid removal efficiency can be calculated. To validate the model calculations, we conducted a set of experiments and compared the simulation with the experimental data. High-moisture, natural concrete sand, the additional material for portland cement, was used and dried along a vertical cylindrical tube with length of 2 m and diameter of 6.68 cm. The drying gas was supplied by a high-capacity air blower which was connected to the burner to produce 120 m3/h of drying gas with maximum temperature of 800°C. 相似文献
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F.C. Lai 《Journal of Electrostatics》2010,68(1):101-104
The performance of an electrohydrodynamically enhanced drying system has been evaluated with its prototype. This scale-up system is the first implementation of such drying technology. It utilizes two convey belts to form a continuous operating system. The prototype uses wire electrodes which are charged at high voltages with positive polarity. The test runs use wet construction sands as sample. The results show that the prototype produces drying enhancement consistent with results previously reported and thus it confirms that the technology can be successfully scaled up. The performance of the prototype can be further enhanced by fine tuning the operating parameters. 相似文献
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Demet Kaya Aktaş Gülşen Akin Evingur Önder Pekcan 《Journal of Macromolecular Science: Physics》2013,52(3):581-590
The steady‐state fluorescence (SSF) technique was employed for studying the drying of polyacrylamide (PAAm) hydrogels. Disc‐shaped hydrogels were prepared by free‐radical crosslinking copolymerization of acrylamide (AAm) with N,N′‐methylene bisacrylamide (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine (P) was introduced as a fluorescence probe and the intensity of pyranine was monitored during in situ drying at various temperatures. It was observed that the fluorescence intensity of pyranine increased during the drying process. A supporting, gravimetrical experiment was also performed. A phenomenological equation was introduced to determine the desorption coefficient, D, of water molecules from the drying hydrogels at various temperatures. The desorption activation energy, ΔE d, values were measured for the drying processes and found to be 91.08 and 36.82 kJ mol–1 by fluorescence and gravimetrical methods, respectively. This difference most probably originates from the origin of the techniques; the fluorescence technique measures the parameters at a molecular level, whereas the gravimetrical technique measures a parameter in the bulk. 相似文献