| 气流改善泡沫树莓果浆微波干燥均匀性提高能量利用率 |
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| 引用本文： | 郑先哲,秦庆雨,王磊,朱勇,沈柳杨,付晗宇.气流改善泡沫树莓果浆微波干燥均匀性提高能量利用率[J].农业工程学报,2019,35(14):280-290. |
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| 作者姓名： | 郑先哲 秦庆雨 王磊 朱勇 沈柳杨 付晗宇 |
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| 作者单位： | 东北农业大学工程学院，哈尔滨 150030,东北农业大学工程学院，哈尔滨 150030,东北农业大学工程学院，哈尔滨 150030,东北农业大学工程学院，哈尔滨 150030,东北农业大学工程学院，哈尔滨 150030,东北农业大学工程学院，哈尔滨 150030 |
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| 基金项目： | 国家自然科学基金项目（31571848、31271911）；哈尔滨市科技项目（2017RAXXJ028） |
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| 摘 要： | 为满足浆果低能耗、高品质的生产过程的需要,采用理论分析、数值模拟与台架试验相结合的方法,研究气流与微波协同作用对泡沫果浆干燥均匀性和微波能利用率的影响规律。结果表明:在气流与微波协同干燥中由于物料的介电特性指标及表观导热、气体渗流、气相导热、液相导热等系数变化,从而影响泡沫果浆料层中传热、传质过程。泡沫果浆传热及传质系数变化,影响泡沫果浆内部热传导及水分传递,温度及含水率直接影响泡沫果浆介电特性指标,进而影响物料微波能吸收。气流在料层边界热对流量及料层内的热传导量是表征气流、微波协同作用的主要指标,当料层边界热对流量与内部热传导量比值低于27.79时,气流与微波协同作用产生正向效应,提高微波能利用率;当料层边界热对流量与内部热传导量比值高于27.79时,此协同作用产生负向效应,降低微波能利用率;气流携带泡沫果浆中蒸发出的水蒸气,降低物料表层湿空气压力,导致泡沫果浆气泡的产生和破裂,强化传热传质过程,进而提高料层内温度及含水率分布均匀性。当气流速度小于1.5m/s时,气流速度与干燥均匀性呈显著正相关;当气流速度大于1.5m/s时,气流速度对物料干燥均匀性影响不显著;在气流速度为1.5m/s时,干燥时间短,微波能利用率最高,相比无通风时提高了17.57%,微波能吸收量、温度及含水率分布的均匀度分别提高了20%、19%及27%,符合低能耗、高品质的浆果干燥生产要求,研究结果为浆果微波泡沫干燥工艺优化提供依据。
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| 关 键 词： | 微波 干燥 模型 泡沫 均匀性 通风 能量利用 |
| 收稿时间： | 2019/4/10 0:00:00 |
| 修稿时间： | 2019/6/14 0:00:00 |
Airflow improving foam berry pulp microwave drying uniformity and energy efficiency |
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| Zheng Xianzhe,Qin Qingyu,Wang Lei,Zhu Yong,Shen Liuyang and Fu Hanyu.Airflow improving foam berry pulp microwave drying uniformity and energy efficiency[J].Transactions of the Chinese Society of Agricultural Engineering,2019,35(14):280-290. |
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| Authors: | Zheng Xianzhe Qin Qingyu Wang Lei Zhu Yong Shen Liuyang and Fu Hanyu |
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| Institution: | College of Engineering, Northeast Agricultural University, Harbin 150030, China,College of Engineering, Northeast Agricultural University, Harbin 150030, China,College of Engineering, Northeast Agricultural University, Harbin 150030, China,College of Engineering, Northeast Agricultural University, Harbin 150030, China,College of Engineering, Northeast Agricultural University, Harbin 150030, China and College of Engineering, Northeast Agricultural University, Harbin 150030, China |
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| Abstract: | In order to improve the drying quality and the utilization of microwave energy for the raspberry drying processing, a combination method including theoretical analysis, numerical simulation and bench test is employed to study the effects of the synergic action of ventilation and microwave drying on the drying uniformity and the utilization rate of microwave energy for foamed pulp. The results showed that the heat transfer and mass transfer process of foamed pulp were depended on the synergistic drying process of ventilation and microwave, which were apparent thermal conductivity, the coefficient of gas percolation, the thermal conductivity of gas phase and the thermal conductivity of liquid phase, respectively. The heat conduction and the moisture transfer of foamed pulp were related to the changes of the coefficient of heat transfer and mass transfer of foamed pulp under microwave drying. In addition, the temperature and moisture content of foamed pulp directly influence the dielectric properties of foamed pulp, which determine the absorption of microwave energy (AME) of the material. The ratio of heat convection amount at the boundary of the material layer to the heat conduction amount inside the material layer (RVD) were introduced to characterize the synergistic effect of ventilation and microwave for the drying of raspberry pulp. The results showed that the synergistic effect of ventilation and microwave has a positive effect at RVD less than 27.79 to promote the utilization rate of microwave energy (URME), other than the synergistic effect reducing the utilization rate of microwave energy. The ventilation flow air could take away the steam from the foam pulp, and reduce the pressure of wet air on the surface of the material, which accelerated the evaporation of water and the emergence and rupture of the bubble of the foamed pulp. The phenomenon of bubble boiling inside raspberry pulp enhances the heat and mass transfer process to improve the distribution uniformity of temperature (DUT) and moisture content (DUM). Ventilation velocity less than 1.5 m/s had a significant positive influence on the drying uniformity inside material layer. However, no significant effect was found the ventilation velocity higher than 1.5 m/s on the drying uniformity. Ventilation velocity of 1.5 m/s was developed as the reasonable level with highest drying efficiency and the utilization rate of microwave energy. Compared with no ventilation, ventilation velocity of 1.5 m/s improved the URME, AME, DUT and DUM to 17.57%, 20%, 19% and by 27%, respectively. The research results meet the requirements of drying production of berries with low consumption of energy and high quality, which also provide a theoretical basis for the optimization of microwave foam in drying technology for berries. |
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| Keywords: | microwave drying models foam uniformity ventilation energy utilization |
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