外文翻译---果蔬太阳能干燥脱水装置设计.doc

果蔬太阳能干燥脱水装置设计摘要：根据广式凉果的干燥特性，设计开发了一套小型全天候太阳能干燥设备，并对该设备进行应用试验研究，对比分析不同凉果在研制的干燥设备中的实际应用结果，与传统的自然日晒干燥、热风干燥相比的优势，寻找设备干燥凉果最佳工艺条件，对工厂的实际运作起指导作用。（1）该小型装置特点是利用对 V 型太阳能集热板进行改造，使之成为既可输送热风，也可实现储存热量于热水中，该设备由集热板，干燥室，小型风机，储热水箱，蛇行风管，水泵，温湿度感应器，小型换热器，自动控制阀门及空气过滤装置组成，有完整的一套集热收集太阳能系统和热风干燥系统。白天干燥过程中，风从集热器底部经加热后进入干燥室干燥，排出的热风经鼓风机重新进风，当干燥室内温度过高时，自动控制阀将打开，水由集热器加热收集热量储存于保温水箱中；夜间当温度感应器感应干燥室内部温度过低，由控制阀中断集热器进风口，风由水箱中蛇形风管由水加热进入干燥室，之后类似于白天干燥过程；白天重新开始时，控制单元驱动控制阀关闭蛇形风管进风口，打开集热器进风口，又开始集热板热风干燥过程，储热水箱又可开始储存热能，周而复始，实现连续干燥操作；气候条件不佳时，可利用水箱中的电热丝加热水，通过蛇形风管实现热风干燥过程。该太阳能连续供热式干燥设备，能连续供热、全天候工作、成本低、结构简单、干燥效率且热利用效率高。（2）试验中采用的自主研制太阳能干燥设备，空气对流方式为自然对流和强制对流方式，研究了样品的干燥特性，在达到干燥要求的情况下，自然对流干燥时间需 14h，强制对流干燥所需时间为 12h，远远低于传统日晒干燥（50h），自然对流干燥整个干燥过程样品的平均 Deff值为 1.3910-6m2/s，强制对流干燥过程中样品的平均 Deff值为1.2610-6m2/s，两种干燥方式干燥的水分扩散能力都比较均匀。（3）干燥设备自然对流干燥和强制对流干燥两种干燥方式下，以干湿梅作为试验样品，研究样品的理化品质及感官特性，试验结果表明，随着湿基湿含量的降低，处于不同层的梅子成品时的总糖、总酸和盐含量均有不同程度的增加，在样品色泽方面，非酶褐变使各层样品的 L*值和 a 值上升，但对于 b 值而言，果皮果肉在干燥过程中趋势相反（果皮 b 值下降，果肉 b 值上升），达到出厂产品品质要求。通过对干燥设备不同干燥方式不同物料层，样品理化及感官特性的研究，试验结果表明，自然对流方式通过适当的调整物料层的位置，对于样品的品质会有一定程度的提高，而强制对流方式由于干燥相对比较稳定，不需要通过调整物料层的位置来提高样品的品质。（4）太阳能干燥设备不同干燥方式下的应用研究表明，相对于自然日晒干燥、温室、烘箱干燥等传统干燥方式，太阳能干燥设备存在明显优势，干燥时间明显缩短，最多可以缩短 76%，设备干燥总效率为 63.4%，干燥过程环保节能；干燥环境高温低湿，产品品质干燥效率和生产成本均有不同程度的提高，可以满足包括梅子等热敏性物料。在内的多种农产品的干燥要求。（5）样品干燥至目标水分含量时，自然日晒大约需要 50h，温室干燥约为 30h，烘箱热风干燥需要 12h，自制太阳能干燥设备自然对流方式及强制对流干燥方式耗时分别为 14h 和 12h。强制对流、烘箱干燥、自然对流、温室干燥与自然日晒干燥在 12h 内湿含量分别降至 58.08%、57.08%、60.21%、64.32%、69.22%。在干燥到相同的湿基湿含量（最终产品）的时候，五种干燥方式干燥产品水分活度均到达储藏要求，产品品质均达到了产品出厂的要求，综合而言，太阳能干燥设备干燥效果最佳。综上分析可以知道，利用自制广式凉果小型太阳能全天候干燥设备研究温室、自然对流和强制对流等干燥方式与传统热风干燥与自然日晒干燥的差异，本试验为小型太阳能全天候干燥设备对工厂的加工生产中的实际应用提供理论依据。太阳辐射具有分散性和断续性的特点，是太阳能利用中最大的困难。如何有效地收集蓄积太阳能，对太阳能的利用效率有着非常重要的影响。太阳能在建筑采暖和农业日光温室的应用中，太阳墙是太阳能收集和蓄积的关键技术，是实现太阳能-建筑-体化的重要组成部分，也是世界各国学者普遍研究和关注的课题。因此，太阳墙的研究有着非常重要的意义。本文综合分析了国内外“太阳墙”的研究现状，集多孔介质复合Trombe墙和太阳能多孔集热墙优点为一体，设计了一种多孔介质太阳墙，并采用数值模拟的方法对多孔介质太阳墙的传热机理及应用进行了研究。 从简化的角度出发，建立描述多孔介质太阳墙传热与流动特性的一维数学模型，对作为媒质的空气在多孔墙内的流动，以及与多孔墙之间的换热机理进行了初步的研究。结果表明:多孔墙能收集与蓄积太阳能，并加热空气;降低多孔墙入口空气速度，能够提高空气的温度;在保证所需的太阳辐射吸收率的条件下，增大多孔墙的孔隙率与渗透率，能够提高空气的温度;当多孔固体材料采用金属与非金属材料时，出口空气温度有着较大的差别。当多孔骨架材料采用铝时，空气的温升幅度较大，出口空气温度高，而采用岩石，空气的温升幅度较小。在实际应用中，应合理选择渗透率和多孔骨架材料，尽可能地降低初投资。 基于对多孔墙的热分析，为降低多孔墙与环境之间的辐射与对流换热损失，从结构上对多孔墙进行改进，设计了一种新型的多孔太阳墙系统。在多孔墙的集热面与环境之间设玻璃盖板，形成玻璃通道。利用玻璃通道的“温室效应”降低热损失和收集热空气。在多孔墙内侧通道内设有风机，在风机的作用下，室外空气流入多孔墙，与多孔墙进行热交换后，被加热到一定的温度，用于冬季的供暖。基于二维稳态Navier-Stoke方程、饱和多孔介质Brinkrnan-Forchheimer Extended Darcy模型和能量双方程模型，对这种设有风机并附加玻璃通道的新型的多孔太阳墙系统内的传热与流动特性进行数值模拟。结果表明:风机的设计对系统内温度场和流场有较大的影响;降低空气入口流速，可减小空气流动阻力，提高多孔墙的集热效率;附加玻璃通道的多孔太阳墙可减小长波辐射损失，并具有收集热空气的作用。因此，它具有较高的集热效率。 设计了一种多孔蓄热墙-温室系统。将温室北墙设计为由“半透明”的等径、均匀的多孔球堆积而成的多孔墙，能吸收和蓄积太阳能，加热温室空气，而且能够主动地调节温室内的热环境。将温室与多孔蓄热墙结合起来，充分发挥两者的作用。从而提高了温室的太阳能利用效果。借助带内热源的饱和多孔介质能量双方程模型和Brinkman-Forchheimer Extended Darcy模型以及k-。紊流模型，对该太阳能温室系统的传热与流动特性进行预测。在此基础上，进一步模拟分析了孔隙率分层多孔墙对温室系统特性的影响。结果表明:温室系统的入口参数和多孔墙的结构对温室内的温度场、流场和压力场有较大的影响。因此，针对一定结构的温室系统，应根据温室热环境的要求，合理地设计多孔墙本体，调节风机的运行工况。 设计了两种通风方式下的多孔太阳墙采暖系统。采用饱和多孔介质Brinlanan-Forchheirner Extended Darcy模型、带内热源的能量双方程模型以及k-。紊流模型对采暖系统内的传热与流动特性进行计算、分析和比较。结果表明，多孔太阳墙采暖系统的送排风方式，对采暖房内的温度场、流场有很大的影响，它直接影响到系统的保温作用，对多孔墙的热利用率有较大的影响。因此，在实际应用中，应合理地设计多孔太阳墙采暖系统，提高多孔墙的热利用率，从而降低多孔墙的热价。 对局部和斜坡地板送风式多孔太阳墙采暖系统内的传热与流动进行了数值模拟，得到了两种系统内的温度分布、流场分布。分析了架空地板的结构、地板送风口尺寸对采暖房内温度场和流场的影响;分析了建筑南墙对室内温度的影响。结果表明:采用地板送风方式，能够保证采暖房内均匀的温度场和流场;采用斜坡式地板送风方式，更有利于保证各送风口流量分布均匀。在实际应用中，应注意建筑承重墙的隔热，防止“热蚀”现象发生。 针对多孔墙的结构特点，采用描述填充结构的多孔介质模型，进一步分析了多孔墙的结构特性。结果表明:增大颗粒直径和孔隙率能够降低系统的阻力。这一结果提供了优化多孔墙的结构参数。设计了多孔太阳墙测试系统，该系统能用于测试多孔太阳墙系统的阻力，多孔墙的吸收率和体积换热系数等特性参数。但由于太阳辐射的模拟是一个难点，因此，为了精确测试多孔墙的热性能，还需对测试系统进行改进。关键词：太阳能干燥，强制对流，温室干燥Fruit and vegetable solar drying dehydration unit designABSTRACT：In this paper, a small scale solar drying equipment was designed based on the study of drying characteristics of preserved fruits of “Study of Drying Characteristics of Preserved Fruit”.The test and applied research of the solar drying equipment was studied and the application of the results of different preserved fruits in the development of the solar drying equipment were analyzed compared to the traditional natural sun drying, hot air drying. The optimum conditions for drying preserved fruits under the solar drying equipment was to be find out and the advantages of the drying equipment was also to be find out. The actual operation of the solar equipment for plants was investigated.(1) The characteristics of the small scale solar drying devices is the reform of the V-plate solar collectors, making it not only transported hot air, but also stored heat in water. The device was comprised of heat collector, drying room, small fan, water storage tank, blast pipe, pumps, temperature and humidity sensors, small heat exchangers, control valves and air filter. And it composed of a complete set of system to collect solar energy and hot air drying system. Drying process during the daytime, the hot air was blew into the drying chamber from the bottom of the collector. Hot air discharged from the chamber was sent back into the chamber by the blower. When the drying chamber temperature was too high than desire, the automatic control valve opens to stored heat to the water tank by the heating collectors. Drying process during the nighttime, when the temperature sensor sensed that the internal temperature of the drying room was too low, the control valve inlet of the collector was interrupted, hot air blew from the pipe in the water tank into the drying chamber. The drying process was similar to the daytime drying process. When the second day started, the control valve inlet of the collector opened, collector plates began daytime drying process. The process was recycled to achieve continuous drying operation. During poor weather conditions, the water in the water tank was heated by the electric, the control valve inlet of the collector was interrupted, hot air blew from the pipe in the water tank into the drying chamber. The drying process was similar to the daytime drying process. The advantage of the solar drying equipment was continuous heating, low cost, simple structure, high drying and thermal efficiency.(2) Air convection of the solar drying equipment included natural convection and forcedconvection. And the drying characteristics of the sample were studied in the solar drying equipment. Drying time of the process of natural convection required to 14h to attain the drying requirement, while the process of forced convection drying time required 12h, far below the traditional the process of sun drying which required 50h. During drying process of the sample, the Deff value was 1.39 10-6m2/s under the natural convection, while the Deff value was 1.26 10-6 m2/s under the forced convection for the drying process of the sample. The Deffvalue of two drying processes could improve that the capacity of the water of the sample spread evenly.(3) Chemical quality and sensory characteristics of the plum samples were investigated under two drying methods of the solar equipment. The experiment results showed that with lower moisture content of the samples, the sugar content, acid content and the salt content of the sample increased at different layers of the drying room.For the color of the sample, the value of L* and the value of a increased caused by non-enzymatic browning. The peel and the pulp of the sample had the opposite trend during the drying process for the value of b. The b value of peel decreased while the b value of pulp increased. All the experiment value was according to the factory product quality requirements. Chemical quality and sensory characteristics of the plum samples were investigated in different layers of the solar drying equipment. Results show that appropriate adjustments to the location of materials were recommended during natural convection to improve the quality of the products. For the quality of products were relatively stable during forced convection drying process, it had no needs for adjusting the position to improve the quality of the sample.(4) The research of solar drying equipment under different drying methods showed that solar drying device has obvious advantages compared to natural sun drying, greenhouse drying, oven drying. The drying time of solar drying device was shortened up to 76%, while the total efficiency of the solar drying equipment was up to 63.4%. The drying process under solar drying equipment was environmental protection and energy conservation. The drying environment was with high temperature and low humidity. The product quality and drying efficiency was some kind of increasing while the costs decreased in varying degrees. The equipment could meet the drying requirement of varieties of agricultural products.(5) Samples were dried to target water content under different drying methods, the natural sun drying took about 50h, while greenhouse drying and oven drying took about 30h and 12h respectively. Drying time of solar drying equipment under natural convection and forced convection needed 14h and 12h respectively. The moisture content within 12h underforced convection drying, oven drying, natural convection drying, natural sun drying and greenhouse drying were reduced to 58.08%, 57.08%, 60.21%, 64.32%, 69.22% respectively. The water activity of dried product which was dried to the same water content under five different drying methods reached the storage requirements and the product quality met the requirements of the factory. In all, the solar drying device obtained the best drying effect. Fully aware of the analysis could be known that greenhouse drying, natural convection and forced convection drying were investigated by using the self-made solar drying equipment. The difference among solar drying equipment, traditional hot air drying and natural sun drying were also investigated. The test results provided theoretical basis for practical application of the self-made solar drying equipment to the factory production.The characteristics of discontinuity and disperse of solar radiation give a great difficulty in solar energy applications. The absorption and storage of solar radiation has important effect on the utilization efficiency of solar energy. In heating buildings and greenhouses, the solar wall is a key part to incorporate the utilization of solar energy with the building, and also subject studied by researchers at home and abroad. So, it is very important to study the solar wall. In this paper, actualities of investigations on solar wall at home and abroad are analyzed. A new porous solar wall is designed by using the excellences of the porous composite Trombe wall and the porous absorption solar wall. In addition, based on numerical simulation, the application and heat transfer performances of the porous solar wall are studied.For simplification, one-dimensional mathematic model is used to describe the heat transfer and flow in the porous solar wall. The flow and heat transfer in the porous wall with the air as heat transfer medium are investigated primarily. To reach such conclusions, the porous wall can collect and store solar energy, and heat air; The air temperature will increase with a decrease in the inlet velocity; On the premise of demand for solar radiation collection, the air temperature will increase with an increase in the porosity and permeability of the porous wall; There are different results when metal and nonmetal are used as the material of the porous matrix, respectively. The increase speed of the air temperature is quicker when aluminum is used as the material of the porous wall. In contrast, the increase speed of the air temperature becomes slower when rock is used as the material of the porous wall. Consequently, the permeability and material of the porous wall should be carefully selected to reduce the cost of the porous solar wall.Based on the thermal analysis, the structure of the porous solar wall is improved and a new porous solar wall is designed to reduce convection and radiation heat exchanges between the porous wall and the ambient. The glass plate is located between the porous wall and the ambient to form a glass duct, which can reduce heat losses and collect hot air by using greenhouse effective. Additionally, the fan is located in the duct near the inside surface of the porous wall. Under the action of the fan, the ambient air flows into the porous wall and exchanges heat with the porous wall. Then the air is heated to certain value to demand for heating in winter. Based on the two-dimensional steady Navier-Stokes equations, Brinkman-Forchheimer Extended Darcy model and energy two-equation model for saturated porous medium, the flow and heat transfer in the new porous solar wall system with glass duct and fan are simulated. The results show that the design of the fan has significant influence on the flow field and temperature field, the flow resistance will decrease and the thermal efficiency of porous wall will increase with a decrease in the inlet velocity, the porous wall with the glass duct can decrease length-wave radiation and collect hot air. So the new porous solar wall system can obtain a higher thermal efficiency as compared with a conventional one.A new greenhouse with heat-storage porous wall is designed, in which the north wall is a heat-storage porous wall. Equal diameter, uniform and semitransparent porous balls are used as the material of the porous solar wall, which can collect and store solar energy to heat the air in the greenhouse, and condition the thermal environment in the greenhouse. Their effect both can be exerted fully by combining the greenhouse with the heat-storage porous wall, which causes the higher solar energy utilization efficiency. Based on Brinkman-Forchheimer Extended Darcy model and energy two-equation model with internal heat source for saturated porous medium k-E turbulent model, the flow and heat transfer characteristics of solar greenhouse system are simulated. Additionally, the influence of the porous wall with layered porosity on the characteristics of the greenhouse is also analyzed by numerical simulation further. The results show that the inlet parameters of the greenhouse and the structure of the porous wall have great effect on the temperature field, the flow field and the pressure field. So, for a certain structure of the greenhouse, the porous wall should be designed and the fan operation should be also conditioned reasonably according to the admired thermal environment in the greenhouse.Two kinds of new solar heating systems with a new porous heat storage wall are designed, which have different ventilation patterns. Based on k-E turbulent model, Brinkman-Forchheimer Extended Darcy model and energy two-equation model for saturated porous medium, the coupled heat transfer and flow characteristics in the new solar heating system are simulated, analyzed and compared. The results show that ventilation pattern has great effect on temperature field and flow field, which also has important influence on the insulation of the heating system and the thermal efficiency of the porous heat storage wall. Thus in real applications, the solar heating system with porous heat storage wall should be designed properly in order to increase the thermal efficiency of porous solar wall and decrease the heating price for porous simulating