冷藏汽车制冷方式及其特点

冷藏汽车在易腐食品产、贮、运、销中起着重要的作用,文中分析了我国食品冷藏链的现状,介绍了冷藏车的发展概况,阐述了冷藏汽车在食品链中的作用和地位,系统论述了冷藏汽车的各种制冷方式及其特点,介绍了冷藏汽车的技术状况。提出了发展我国冷藏车的建议,对我国冷藏车的设计与运行管理具有一定的参考价值。     

蓄冷罐式冷板冷藏车厢设计及温度场分析

针对机械式冷藏车和传统冷板冷藏车的缺点,设计蓄冷罐式冷板冷藏车厢,以提高蓄冷式冷藏车的蓄冷量,延长冷藏运输时间。通过计算冷藏车厢运载时的冷负荷,确定冷板尺寸及蓄冷罐容积等参数;建立蓄冷罐式冷板冷藏车厢模型,通过模拟得到冷藏车厢内温度场分布。结果表明,车厢底面隔热层厚度为90 mm时,车厢内货物温度可维持在281.15 K以内,车厢底部温度随运输时间增加逐渐升高,10 h时车厢底面货物温度升至283.75 K;当隔热层厚度增加至150 mm时,车厢底部温度随运输时间增加变化较小,10 h时车厢底面货物温度升至282.58 K。     

LNG冷藏车冷量回收的各种方法比较分析

液化天然气(LNG)是一种绿色的汽车燃料,LNG冷藏车是以LNG为动力燃料.存储在111K下的LNG在汽化升温过程中会释放大量的冷量,通过对冷量回收,用于低温冷藏车的冷藏运输,具有节能和环保的双重意义.文中分析了LNG冷藏车的特点,针对传统LNG冷藏车制冷方式的缺点,通过三种改进方案得以解决,并对三种方案的特点进行分析...     

食品冷藏运输过程的LCCP评价

本文基于寿命期气候性能LCCP概念,加入环境温度变化、冷藏运输车型、车速、制冷柜的COP和驱动方式、运输距离等影响因素,提出了科学评价食品冷藏运输过程LCCP的计算方法,并对12种冷藏运输车,在六个城市、不同冷藏温度及不同寿命期限内,使用R404A、R410A、CO₂三种制冷剂的LCCP进行了对比评价。结果表明:环境温度较高的城市,LCCP较大;与CO₂及R410A相比,R404A的LCCP最大;冷藏温度越低,能耗越大,LCCP越大;相比于使用主发动机或电驱动制冷柜的冷藏车,使用辅助发动机驱动的冷藏车的LCCP较大。     

冷藏运输车内气体流场的数值模拟及分析

利用计算流体力学(ANSYS)软件,建立了冷藏运输模拟试验台的物理模型,对冷藏运输车内流场进行了数值模拟研究。主要研究内容包括:(1)不同送风速度对冷藏运输车内流场分布的影响;(2)不同时间内库内流场变化情况。冷藏运输模拟试验台采用前端送风,两侧回风口的送风方式。风机吹出的冷气能够在库体内形成大的回流,从而降低库体温度并且使库体内温度分布的均匀。不同送风速度影响车体内速度场的分布,而当送风速度较大时,库内的温度会在短期内均匀。但是过大的送风速度会风干冷藏车内的食品。     

冷藏集装箱内部温度场的理论与实验研究

冷藏集装箱内部的温度分布是冷藏集装箱设计中关注的要点,因此文中通过建立冷藏集装箱物理模型和数学模型对其温度场进行了数值模拟和实验研究。利用稳态不可压缩N-S时均方程及k-ε模型进行模拟分析,结果表明:冷藏集装箱内部温度场存在明显的不均匀性,箱体前部与后部的温度存在明显的差异,不利于货物的储存。实验实测温度与模拟温度的偏差低于16.4%,说明所建立的模型适用于冷藏集装箱内部温度场的模拟。研究结论对进一步开展冷藏集装箱货物配载以及结构设计研究具有一定的指导与借鉴意义。     

物理冷藏条件与浸泡时间对大豆常温吸水率的影响

使用最常见的冰箱等实验器具,以冷藏温度、冷藏时间与浸泡时间为3个因素,开展L9(33)正交实验,研究冷藏温度、冷藏时间与浸泡时间对常温下大豆吸水率的影响。实验表明:先浸泡、冷藏,再解冻、浸泡,充分发挥了冰晶对大豆内部的破坏作用,人为增大了大豆内部吸水空间,使大豆吸水率进一步提高。     

冷藏集装箱内部流场及送风方式的研究

冷藏集装箱内部流场的均匀性是影响货物储存质量的重要因素之一。文中通过建立CFD三维数学模型,利用FLUENT软件对所建立的模型进行不同参数的模拟分析。分析结果表明:冷藏集装箱内部流场存在明显的不均匀性,箱体前部与后部的温度存在明显的差异,不利于货物的储存。根据以上分析研究,利用均匀送风理论,设计出两种新型送风风道型式,根据对所设计的风道进行计算分析,研究发现:新型冷藏集装箱与原始冷藏集装箱相比温度场和速度场都有明显改进,且在箱体中部的流场涡流现象减小,有利于货物的储存,该研究为冷藏集装箱的优化设计提供了参考依据。     

机械式冷藏车蒸发器结霜特性的研究

机械冷藏车蒸发器结霜会增加传热热阻和减小换热量,必须对结霜过程进行深入了解。建立了一个机械冷藏车蒸发器结霜的数学模型,并计算了结霜量、蒸发器换热量随时间的变化过程。获得了各个入口空气参数对蒸发器结霜厚度和换热量的影响规律。研究发现结霜严重地影响了蒸发器换热性能。     

液化天然气(LNG)冷藏车冷量回收换热器的设计

液化天然气(LNG)用做优质"绿色"汽车燃料的同时,还具有大量的冷能,该冷能可回收用于冷藏车制冷,LNG冷藏车是一种节能环保型汽车。在LNG冷藏车冷量回收系统中,传统的方式是将LNG在换热器中直接气化,并向空气释放冷量,但这种方式中的换热器表面易结霜,对其性能造成很大危害。文中提出了采用热管技术回收LNG冷量并用于冷藏车制冷的方法;设计了新型的热管式LNG冷量回收换热器,该新型换热器具有高效、紧凑等特点。     

冷藏展示柜冷却风道的设计及数值模拟

以冷藏展示柜强制冷却冷凝器的冷却风道为对象,建立了物理数学模型,用SIMPLE方法计算了3种型式冷凝器冷却风道空气流场,通过速度分布图和速度矢量图分析了各型式风道冷凝器和压缩机冷却效果,结合冷藏展示柜的结构和实际应用提出了冷却风道优化的方向,为冷藏展示柜的优化设计提供了参考.     

Heat transfer and fluid flow of benard-cell convection in rectangular container with free surface sensed by infrared thermography

The natural convection flow phenomena that occur inside an enclosed space are very interesting examples of complex fluid systems that may yield to analytical, empirical and numerical solutions, and many reports have looked into this basic problem. In the present study, heat transfer and fluid flow for natural convection in a horizontal rectangular container with a free surface are investigated using infrared thermography. The temperature field was measured and visualized at a gas-liquid (air — silicon oil) interface using infrared thermography. The heat transfer phenomena were also investigated by statistically analyzing the temperature data. The applicability of the infrared thermography to quantitative heat transfer measurement at the gas-liquid interface was evaluated. It is revealed that infrared thermography is effective not only in visualization of a gas-liquid interface but also in heat transfer measurement. A new heat transfer correlation is proposed for the gas-liquid interface of this flow system. The coefficient of heat transfer can be summarized by a specific heat transfer correlation formula regardless of several conditions, including container aspect ratio, fluid viscosity and fluid layer depth.     

Thermomagnetic natural convection of thermo-sensitive magnetic fluids in cubic cavity with heat generating object inside

Experiment and numerical study were conducted to investigate the heat transfer characteristics of a thermo-sensitive magnetic fluid (TSMF) filled in a cubic container with a heat generating square cylinder stick inside and under a uniform magnetic field. The experimental results show that, regardless of the heat generating object sizes, the heat transfer characteristic of the TSMF is enhanced when the magnetic field is applied to the TSMF. However, the heat transfer of the TSMF becomes poor as the size of the inside heat generating object increases because the space where the fluids go through becomes narrower and the flow is obstructed when the heat generating object size becomes bigger. Numerical simulation based on the Lattice Boltzmann method confirmed the experimental findings, and disclosed more flow details of the natural convection of the TSMF inside cavity.     

空气净化器内部结构对其净化效率的影响研究

本文通过理论分析及实验验证,全面分析了影响净化器净化效率的因素,结果发现净化器内部辐射场、流场和浓度场得分布是影响净化器效率的主要因素。净化器内部结构的设计应该充分考虑这些因素的影响,使其净化效率达到最佳。     

Release potential of single-wall carbon nanotubes produced by super-growth method during manufacturing and handling

We investigated the release potential of single-wall carbon nanotubes (CNTs) produced by the super-growth method during their manufacturing and handling processes at a research facility. We generally sampled air at points both outside and inside of protective enclosures such as a glove box and fume hood. Sampling the air outside of the enclosures was intended to evaluate the actual exposure of workers to CNTs, while sampling the air inside the enclosures was performed to quantify the release of CNTs to the air in order to estimate the potential exposure of workers without protection. The results revealed that airborne CNTs were generated when (1) CNTs were separated from the substrates using a spatula and placed in a container in a glove box; (2) an air gun was used to clean the air filters (containing dust that included CNTs) of a vacuum cleaner; (3) a vacuum cleaner was used to collect CNTs (emission with exhaust air from the cleaner); (4) the container of CNTs was opened; and (5) CNTs in the bin of the cleaner were transferred to a container. In these processes, airborne CNTs were only found inside the enclosures, except for a small amount of CNTs released from the glove box when it was opened. Electron microscopic observations of aerosol particles found CNT clusters, which were fragments of CNT forests, with sizes ranging from submicrometers to tens of micrometers.     

冷库预冷流动传热物理场分布研究

冷库预冷是传统的果蔬采后预冷方法,前人研究通过数值模拟使冷库预冷过程的流场和温度场可视化,本文进一步分析空气流速、局部平均空气龄、温度、熵产、(火用)损和(火积)耗散等物理场的分布特性,指出其间存在密切联系。塑料筐周围的空气流速和流向与内部的局部平均空气龄有关,并影响内部的传热速率。传热熵产率、传热(火用)损率和(火积)耗散率的分布特性及其变化趋势相似,局部高值与局部平均空气龄较低的区域均出现在塑料筐的表面。