黄瓜冷激处理过程分层数值模拟与传热特性分析  

Layered numerical simulation and heat transfer characteristic analysis on cold shock treatment of cucumber

作　　者：陈爱强[1] 杨昭[1] 张娜[1] 赵松松[1] 陈明峰[1] 

机构地区：[1]天津大学热能研究所,天津300072

出　　处：《农业工程学报》2015年第4期312-318,共7页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金项目(51476111;51276124);教育部博士点基金项目(20130032130006);天津市科技支撑计划项目(12ZCDGGX49400)

摘　　要：为研究果蔬冷激过程中内部组织传热特征,根据果蔬生理结构特征建立并验证了柱状果蔬的分层传热模型。利用所建模型分析了以空气和冷水为处理介质时流速、果蔬尺寸、组织热物性差异对黄瓜冷激传热过程的影响。结果表明,所建模型在黄瓜中心、距中心2R/5及4R/5(R为黄瓜半径)处的平均温度误差(MEE)分别为0.423、0.377和0.842℃,最大绝对误差(MAE)为1.713℃,具有较高精度。空气流速由1 m/s增至5 m/s过程中,黄瓜降温速率增幅较大,对流换热热阻对传热过程影响较大;水流速度由0.2 m/s增至1.8 m/s过程中,黄瓜中心处降温速率增幅较小,果蔬内部热阻对传热过程具有较大影响。以水为处理介质时,物性差异的影响大于以空气为处理介质时的影响。研究结果可为果蔬冷激处理工艺优化提供理论参考。Cold shock treatment has been extensively studied as an effective physical treatment method to improve the storage quality of fruits and vegetables because of environmental benefit. To simulate cold shock treatment and study the heat transfer characteristics of cylindrical postharvest fruits and vegetables in those processes, a heat transfer model was proposed based on the structural features of fruits and vegetables in present study. The cucumber tissue was divided into three layers according to the structural characteristics, and thermophysical properties of each layer were also measured. Cold shock treatment of cucumber with 0℃ cold water was conducted in a constant temperature tank designed by the authors. The measured temperatures of the cucumber tissue at the center, two-fifths of the radius and four-fifths of the radius from the center of fruits during water cooling were compared against the results obtained from the simulation by the model. The maximum error between simulated and measured temperatures was 1.713℃, and the mean errors at the center, two-fifths of the radius and four-fifths of the radius form the center of the cucumber were 0.423, 0.377 and 0.842℃, respectively. The comparison analysis showed that the simulation results were in good agreement with the measured values, which indicated the reliability of the model. Using the validated model, the cold shock processes of the cucumbers with chilled air and cold water were simulated, and the effects of flow velocity of medium, fruit size and thermophysical property difference inside the cucumber on the heat transfer process were also analyzed. Results showed that, when cold shock treatment was conducted with cold water at 0℃, the cooling rate of cucumber tissue was faster, and it caused a shorter required duration and larger temperature gradient along the radius of the cucumber, which resulted that the chilling stress experienced by outside tissue was longer than that experienced by inside tissue of the cucumber. Different from cold water,

关 键 词：热传递 模型 机理 黄瓜 冷激处理 柱状果蔬 

分 类 号：S609.3[农业科学—园艺学]