不同预冷方式、包装及果实规格对番茄预冷效果的影响

研究了不同包装的番茄在常温条件下堆货对其品温、失重率及感官评价的影响,比较了不同预冷方式、包装及果实规格番茄的预冷效果。结果表明：番茄常温堆放24 h后,纸箱包装的番茄品温变化较小,保持果实品质效果较好;番茄压差预冷时间可比冷库预冷时间缩短1 h,且失重率较低;不同规格的番茄预冷速率差异显著,应分别预冷;4种不同的包装中,以塑料箱包装的番茄冷库预冷效果最佳,失重率相对较低。     

果蔬强制通风预冷过程中温度场分布的分析

果蔬预冷是冷链的首要环节之一。以100 t冷库为研究对象,建立了气体区和果蔬区的数学、物理模型,采用k-ε紊流模型和非稳态求解方法,运用计算流体力学软件对果蔬预冷降温过程进行了三维非稳态数值模拟。在其他参数相同的条件下,比较分析了不同风速和送风方式下的温度场分布情况。结果表明：送风速度对库内温度场有显著影响,温度随风速的增大而降低,且温度梯度逐渐减小;对比两种送风方式,上送下回送风方式预冷均匀性较好。     

不同送风湿度下储粮机械通风效果的数值模拟研究

以多孔介质传热传质、计算流体动力学理论为基础,采用数值模拟方法,保持其他参数不变,改变送风的湿度,探究就仓通风时,送风相对湿度分别为55%、60%、65%的条件下,0.3 m、2.1 m、3.7 m和5.5 m这四个粮层的温度和水分含量随时间的变化情况,得出送风湿度对粮堆各层温度和水分含量的影响,研究结果可以为储粮通风操作提供参考。     

冷藏车内温度场和湿度场的数值模拟研究

应用流体力学（CFD）软件Fluent,采用k-ζ流模型和非稳态求解方法,对加入货物冷藏车的温度场和湿度场进行了三维非稳态数值模拟计算．得到了冷藏车蒸发器区、中心区、货物区以及边壁等处的温湿度分布。冷藏车内流场的数值模拟结果可以为监测与控制冷藏车内的环境提供技术依据。     

不同熔化速率下的电渣重熔过程数值模拟分析

电渣重熔能提高钢锭的质量,从而满足特种行业的需要,其过程伴随着复杂的物理现象,存在着磁流体流动、传热和传质以及电化学等多方面的影响。通过耦合电磁以及流动和温度方程对电渣重熔过程的三维瞬态进行了数学模拟,研究了熔化速率对重熔过程的影响。结果表明：电流密度、焦耳热和电磁力都随着熔化速率的增大而增大,当熔化速率由14.4 kg/h增加到27.0kg/h,电流密度、焦耳热和电磁力最大值的增大比例超过100%。随着熔化速率的增大,温度最大值有小幅的增加,而且速度最大值的增大幅度接近50%;金属熔池深度则由27 mm增大到38 mm,不利于保证铸坯的质量。     

Numerical Simulation of HVAC in Vehicle Air Conditioning System

Through applying the theory of Computational Fluid Dynamics(CFD),this paper describes the numerical simulation of a typical HVAC in vehicle air conditioning system for improving on the structure of HVAC,shortening the time periods of product design and reducing the costs of design. By applying CFD to simulate designs and improve on the inconsepuential designs,it can make the symmetrical distributing of velocity and temperature of air in HVAC,obtain a proper value of velocity and reduce the yawp value.From the result of simulation,the numerical model has been optimized.It advances the capability of air-conditioning system.While applying CFD to the design of HVAC,it carry the purpose of shortening design the periods of HVAC and reducing the costs of empolderings and tests.     

Exploration of Positive Pressure Mechanical Air Supply System

The problems are discussed in positive pressure mechanical air supply system design, when the actual status is far different from what figures in the code based. Expressions must be used to determine the supply air rate. The rate between length and width of rectangle air channel should be less than 6. To avoid some uncertain factor, correction factor for absolute coarseness should choose the bigger figure. The smoke control and extraction design of smoke controlling stair hall must be divide into two parts: The overground and the underground. When setting positive pressure mechanical air supply system in smoke controlling stair hall, the outer window in the hall must be fixed. To insure the inner surface of smoke controlling stair hall keep compact and lubricity, communion should be done with governor of builders.     

Numerical simulation of flow field dynamics characteristics for a novel twin screw kneader

The numerical simulation for dynamic characteristics of the flow field of a novel twin screw kneader is carried out. The numerical simulation model of twin screw kneader is established,and the three dimensional,isothermal and steady numerical analyses of non newtonian fluid are presented based on computational fluid dynamics(CFD)theory,and the characteristics under the conditions of different speeds and center distances,such as the distribution of pressure and velocity field,the maximum shear stress,the mass flow rate and so on,are studied. The research results show that：with increasing speed,the maximum flow pressure,the mass flow rate and the maximum shear stress increase; the maximum shear stress increases first and then decreases with increasing of center distance of the screw rotors,while the mass flow rate increases with increasing of center distance; but when the center distance reaches a certain degree,the mass flow rate is negative and the material appears serious reflux which can make the kneader stop working. The results provide a theoretical basis for performance prediction and reasonable designing for the novel twin screw kneader.     

机械通风降温效果的数值评估

地槽通风是机械通风的常用形式,是保证粮食安全储存和保持粮食品质的重要措施.常规的试验研究测量方法难以全面和准确评估设计的有效性和合理性.本研究利用计算机流动模拟的方法(CFD)对常用的U形地槽通风方案进行了数值研究,获得了风道中流速和压力分布的关键性数据,发现了与实际现象相符合的通风死角区域,同时又发现了常规测量手段中难以探测到的风道之间存在的通风薄弱区域,在理论上分析了存在通风死角和风道压力损失的原因.计算流体力学研究方法的运用可成为机械通风优化设计研究的有效工具,为今后机械通风应用技术的发展提供针对性和实用性的依据.