负压环境下荔枝保鲜数值分析及实验研究

Numerical simulation and experimental verification on litchi preservation under vacuum condition

荔枝中富含营养物质,对改善国民身体素质颇有益处,但荔枝在常温下几天就会褐变,货架期非常短。为探究荔枝在负压环境的温度分布,该实验对球状荔枝进行真空预冷传热传质模拟和实验研究,模拟了真空室内压力的变化和温度分布。然后,在真空预冷期间,将荔枝分成质量均匀的4组,分别在加湿比重为0%、2%、3%、5%的情况下加湿,利用热电偶测量荔枝表面和中心的温度。研究结果表明,在传热传质模拟验证中,实验中真空室内压力和温度变化与模拟值基本吻合,当加湿比重为3%时,中心温度和表面温度下降最快,其中表面温度下降到4℃,中心温度下降到10℃,且预冷到相同的温度时,该条件下所需时间也最短。

Litchi is a kind of important fruit due to its nutrition to human health,but it is difficult to keep its freshness.Litchi will brown in a few days after harvest at normal temperature,and the shelf life is very short.To investigate the temperature distribution of litchi in a vacuum condition environment,vacuum precooling heat,mass transfer simulation and experimental study of spherical litchi were car-ried out to simulate the changes of pressure and temperature distribution in the vacuum chamber.Secondly,during the vacuum precooling process,the litchi was divided into four uniform groups with masses and humidified at 0%,2%,3%and 5%humidification specific gravity,and the temperature of the surface and center of the litchi was measured by a thermocouple.The results showed that in the heat and mass transfer simulation verification,the pressure and temperature changes in the vacuum chamber in the experiment basically match with the simulated values.Moreover,under different humidification specific gravity,when the humidification specific gravity was 3%,the center temperature and surface temperature drop the fastest.The surface temperature dropped to 4℃and the center temperature dropped to 10℃,the time required for precooling to the same temperature was also the shortest.