【作者】 刘伟涛；

【导师】 李汴生；

【作者基本信息】 华南理工大学 ， 食品科学， 2010， 硕士

【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1.39×10-6m2/s,强制对流干燥过程中样品的平均Deff值为1.26×10-6 m2/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侯干燥设备研究温室、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侯干燥设备对工厂的加工生产中的实际应用提供理论依据。更多还原

【Abstract】 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 forced convection. 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 Deff value 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 under forced 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.更多还原