摘要
建立了描述球形食品在真空冷却中传热、传质的数学模型。通过数值求解得到真空压力、产品质量、产品温度 (表面温度、中心温度、质量平均温度 )随时间的变化曲线。实验装置中高精度的数据采集系统能够在线测定和记录真空室压力、产品质量、产品不同位置的温度随时间的变化。在春收甘蓝的真空冷却实验中 ,模拟的压力和实测的压力在 10 0 0 0～60 0Pa的降压过程中最大相差 10 0Pa ;模拟值和实测值间温度的最大差值小于 1℃ ;真空冷却中 ,模拟的甘蓝的水分损失率是 3 .3 2 % ,实测的甘蓝水分损失率是 2 .97% ,相差 0 .3 5 %。研究结果对真空冷却中产品的蒸发换热特性提供了一些基本的流动和传热规律。
A mathematical model is developed for the heat and mass transfer of spherical foods during vacuum cooling. Variation histories of total pressure of the vacuum system, product mass as well as product temperature(including surface temperature,center temperature and mass-average temperature) are achieved by numerical calculation. Data collecting system with high accuracy can test and record the vacuum pressure, product mass, and product temperatures at different positions. The experiment was carried out on the vacuum cooling of spring-harvested head lettuce. The maxium difference between the simulated pressure and tested pressure is less than 100 Pa when the pressure ranges from 10000 Pa to 600 Pa. The maxium difference between the simulated temperature and tested temperature is 1℃. The simulated water loss ratio of head lettuce is 3.32%, while the tested water loss ratio is 2.97%, the difference is 0.35%. The research results provide some basic rules for flow and heat transfer about the characteriatics of evaporation heat transfer of product during vacuum cooling.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2003年第6期205-208,共4页
Transactions of the Chinese Society of Agricultural Engineering
基金
上海市重大攻关项目 (0 2 391 2 0 63)
关键词
真空冷却
传热传质
预冷
货架期
vacuum cooling
heat and mass transfer
precooling
shelf life
