汽-液-固三相流化床蒸发器浓缩食品液体的实验研究

介绍了三相流化床蒸发器的结构特点，对其传热和防、除垢性能进行了研究；论述了把汽-液-固三相流化床蒸发器应用于食品液体浓缩的可行性。研究结果表明：汽-液-固三相流化床蒸发器具有良好的传热和防、除垢性能，在食品工业中具有一定的应用前景。     

惰性粒子流化床蒸发器浓缩南瓜汁的传热研究

根据惰性粒子流化床蒸发器的结构特点,将其用于浓缩南瓜汁,讨论了惰性粒子在流体中的运动情况及其对循环流化床蒸发器浓缩南瓜汁的传热性能的影响,建立了汽-液-固三相流动沸腾传热准数经验关联式.实验结果表明,该准数经验关联式的计算值与实验值吻合较好.     

三相循环流化床麦草浆黑液蒸发器的研究

研究了新型麦草浆黑液蒸发器——汽液固三相循环流化床蒸发器的强化传热和防、除垢性能。麦草浆黑液是全国造纸行业的主要污染物，采用碱回收处理。蒸发是碱回收关键的一个工段。实验表明，在浓度31％的黑液中加入聚四氟乙烯粒子可提高传热系数20％-40％。新型蒸发器有良好的防垢性能。     

气-液-固三相循环流化床蒸发器浓缩南瓜汁

研究了三相循环流化床蒸发器浓缩南瓜汁的传热性能和防、除垢性能 ,分析了主要操作因素对传热性能的影响 ,建立了传热系数经验关联式 ,并且对南瓜汁蒸发浓缩过程进行了质量评估。研究结果表明 ,三相循环流化床蒸发器具有良好的传热性能和防、除垢性能 ,适宜南瓜汁的浓缩 ,在食品工业具有一定的应用前景。     

三相循环流化床蒸发器浓缩葡萄糖溶液的传热研究

研究了三相循环流化床蒸发器浓缩葡萄糖溶液时的传热性能,分析了一些主要操作因素对传热性能的影响,给出了传热系数与主要操作参数的经验关联式,讨论了三相循环流化床蒸发器的防、除垢性能。     

食品液体(南瓜汁)蒸发浓缩过程动力学研究

本文对蒸发浓缩过程营养损失动力学进行了研究,建立了汽一液一固三相循环流化床蒸发器蒸发浓缩南瓜汁时胡萝卜素损失的动力学模型。实验结果表明:模型预测值与实验值吻合良好,该模型对工业生产有一定的应用价值。     

三相循环流化床麦草浆黑液蒸发器传热模型

对三相循环流化床蒸发器流动沸腾传热机理进行了分析.建立了适用于烧碱法麦草浆黑液系统的三相循环流化床传热模型.验证实验表明:模型计算值和实验数据吻合较好,最大偏差在30%以内.     

固相对双室双管程蒸发器平均传热系数的影响

新型双室双管程蒸发器结合了多室蒸发和双管程蒸发的优点,适用于蒸发粘度随浓度变化较大的物料。通过配制不同比例的水一甘油溶液,并在循环管中加入惰性固体颗粒,对双室双管程蒸发器的传热性能进行了实验研究。结果表明：双室双管程蒸发器内加入惰性固体颗粒,具有良好的传热效果,平均传热系数增大幅度为12％左右,并且加热管的热通量、颗粒粒径、颗粒体积分率都对平均传热系数有一定影响。     

流化床自清洁换热技术在卤水预热器中的应用

介绍了将液固流化床换热技术应用于盐矿卤水预热器中的情况，考察了惰性固体颗粒防止预热器结垢效果。应用结果表明：在一定的固体颗粒浓度和操作流速下，液固流化床能有效防止盐旷卤水预热器结垢。能提高盐矿卤水真空制盐系统的产能，经济效益显著。     

国产降膜蒸发器新进展

降膜蒸发器虽然在 19世纪末即已问世 ,但其迅速发展成多效并配以余热利用装置而被广泛采用则是在 2 0世纪5 0年代。第一台四效蒸发器诞生在1966年 ,乳品行业使用六效和七效始于1976年。降膜蒸发器的主要特点是 :料液在重力和二次蒸汽流的作用下 ,经加热器顶部的液体分布装置均匀地以膜状沿加热管内壁高速向下流动。在流动过程中 ,在真空条件下进行低温膜式蒸发。液膜在有相变条件下 ,传热性能高 ,在较低温差下可得到较高的传热分系数 ;液膜在有汽相流作用下 ,流速极高 ,因而使液膜与传热面接触时间短 ,非常适宜热敏物料的浓缩。降膜蒸发器以…     

矩形肋槽烘缸的导热模型

对矩形肋槽烘缸壁壳内的传热作了分析,考虑肋壁各处传热系数的不同,采用有限差分法建立了导热模型,通过对不同工况的计算,对肋槽尺寸对烘缸传热特性的影响进行了探讨。结果表明,增大肋宽有利于提高传热速率;在肋壁表面上的传热系数较低时,增大肋高可以提高传热速率;传热系数较高时,增大肋高,有可能使肋壁表面上的对流热阻的减小慢于导热热阻的增大,反而降低传热速率;肋效率和外壁面的温度均匀性也呈现出类似的表现。     

多孔纤维织物热湿传递数值模拟的研究进展

热湿传递数值模拟的研究可为多孔纤维织物的制备和热湿性能评估提供理论基础。在阐述了织物热湿传递机制的基础上,从织物热湿传递数值模型、数值模拟计算方法以及织物热湿传递性能测试方法 3个方面,综述了近年来关于织物热湿传递方面的新进展,分析了现有织物传热传湿数值模拟研究中存在的问题,提出在创建织物三维方向上的热湿耦合模型时,要综合考虑织物本身的交织结构特征和纱线的物理性能;在数值分析过程中要充分考虑实际应用条件下织物材料物理性能的变化,进一步优化织物传热传湿数值模型,提高模拟计算的准确度。     

矩形肋槽烘缸内壁面的传热系数

将传热学的理论和实验成果应用于矩形肋槽烘缸内壁面的传热工作中,分析了饱和水蒸气在烘缸内壁的肋顶面及肋侧面的冷凝传热和冷凝水在肋槽底部的对流传热并推导出这3种情况下传热系数的具体计算公式,以期为烘缸向纸张的传热计算提供依据。初步研究表明,宽和短的肋有利于增强肋槽烘缸的传热,内壁面的热阻最小、壁壳的热阻次之、外壁面的热阻最大。     

A method for the calculation of the heat transfer coefficient in potato drying

A method for the determination of the heat transfer coefficient was proposed for the first falling drying period of potato cubes. During this period, heat and mass transfer were considered as coupled phenomena. Temperature calculation inside the sample was performed using the macroscopic heat transfer balance. The heat transfer coefficient was computed by means of parametric identification, using the Gauss–Newton method. The figure obtained for the heat transfer coefficient shows good agreement with other sources.     

MODELLING of the MEDIA-SIDE HEAT TRANSFER IN SCRAPED SURFACE HEAT EXCHANGERS

The heat transfer on the media-side and in the tube wall of scraped surface heat exchangers was investigated when the product was heated with steam or cooled with water. The heat transfer coefficients found experimentally were 15% higher than predicted with the Nusselt theory for steam condensation, and 30% lower than predicted with a traditionally recommended model for cooling with water. New, much better models for the media-side heat transfer were developed. the choice of model for the media-side affects a subsequent modelling of the heat transfer on the product-side. When the product-flow was laminar in the scraped surface heat exchangers, the heat transfer was controlled mainly by the resistance on the product-side; while the resistance on the media-side was very small. Vortical flow decreased the resistance on the product-side considerably and made the choice of material in the tube wall important from a heat transfer point of view.     

Numerical simulation of heat and moisture transfer through bulky PAN nanofiber mats

In this study, the coupled heat and moisture transfer of polyacrylonitril nanofiber mats were investigated by theoretical and experimental methods. A mathematical model was used to describe and predict the coupled heat and moisture transfer of nanofiber mats. Based on the results obtained by scale analysis method, order of magnitude of heat transfer by radiation is negligible for nanofiber mats but heat transfer by convection is important. In this investigation, the coupled heat and moisture transfer including convection heat transfer was solved numerically by finite difference method. Comparison between numerical results and experimental data shows good agreement, which indicates the high accuracy of the numerical results.     

MODELLING of LAMINAR HEAT TRANSFER IN SCRAPED SURFACE HEAT EXCHANGERS

Heat transfer experiments with starch pastes have been performed in pilot plant scraped surface heat exchangers (SSHE). Effects of the following variables were considered in the modelling of the laminar heat transfer: rotational speed; viscosity, flow rate, number of blades, radius ratio and heat transfer direction. The poor radial mixing restricted the heat transfer coefficients. When the radius ratio increased, the heat transfer rate increased. This was probably due to increasing mixing effects from the blades. the flow rate and the heat transfer directions did not affect the heat transfer coefficients. The scatter in the heat transfer coefficients was considerable, due to unstable flow conditions in the SSHEs. However, the scatter was reduced, compared with previous investigations, by the use of a static mixer after the SSHEs, since the radial temperature differences were eliminated. Better design of rotor and blades may improve the performance of SSHEs operating with laminar flow.     

Heat transfer in a tunnel pasteuriser. Part II: Heat transfer coefficients

The effect of heat transfer resistances on the overall heat transfer between water spray and liquid heated in a glass container has been studied. Values for convective and overall heat transfer coefficients were determined. The overall heat transfer coefficient was affected by hot water spray intensity, location of bottle in relation to the spray nozzle axis and the shape of the bottle. The effect of the viscosity of the heated liquid on the overall heat transfer coefficient was very pronounced. Variation in convective and overall heat transfer coefficients with height on the bottle wall was also investigated.It was found that the largest heat transfer resistance occurs in the glass when water is the heated liquid. With liquids of viscosity higher than 1·1 × 10^?3 Pa s the main resistance is in the heated liquid. Resistance to heat transfer from the hot water spray to the bottle wall is around eight times smaller than the resistance of the glass wall. The physical properties of the liquid being heated greatly affect heat transfer under tunnel pasteuriser conditions.     

织物层热湿传递过程仿真研究

对服装织物层基本几何单元内空气层与纱线热湿传递机理模型进行了数值模拟分析 ,建立了空气层与纱线交界处的热湿传递动态过程 ,通过计算机仿真分析了织物内纱线、空气层的温度场和湿度场 ,并探讨了纱线材料特性、织物的组织结构对织物层热湿传递过程的影响规律     

P-RC APMP制浆废水沸腾传热系数的研究

研究了P-RC APMP制浆废水的沸腾传热系数,实验在强制循环蒸发器上进行,考察了热通量、流体流速、流体浓度对P-RC APMP制浆废水沸腾传热系数的影响。结果表明,在一定的热通量下,随着流体流速的增加,P-RC APMP制浆废水沸腾传热系数增加;浓度不同,流速对传热系数的影响不同,浓度越大,流速对传热系数的影响越大。