Abstract

Room cooling is traditionally used for postharvest products and is always involved with heterogeneous airflow and heat transfer. Despite the current evaluation of such heterogeneity, the irreversibility parameters are still not considered to evaluate the corresponding characteristics. Furthermore, the relationships between the irreversibility and the heterogeneous airflow and heat transfer should be also analyzed. To this end, based on the numerical simulation using an experimentally validated model, the distribution characteristics of air velocity, local mean air age, temperature, local volumetric rates of entropy generation, and entransy dissipation during the room cooling process for postharvest apples are respectively discussed. The relationships between the irreversibility parameters and apparent heterogeneity are further analyzed. The results show that higher local mean air age and temperature inside bins are resulted by lower air velocity nearby, and significant local volumetric rates of entropy generation and entransy dissipation at the surfaces of bins are also obtained for longer duration in the room cooling process. The irreversibility parameters, including local volumetric rates of entropy generation and entransy dissipation, are related to local mean air age with the Pearson’s coefficients of between 0.60 and 0.80 and better related to temperature with the Pearson’s coefficients of above 0.80.

摘要

室内冷却传统上用于采后产品，并且总是涉及不均匀的气流和热传递。尽管目前对这种异质性进行了评估，但仍然没有考虑不可逆性参数来评估相应的特征。此外，还应分析不可逆性与异质气流和传热之间的关系。为此，在使用经过实验验证的模型进行数值模拟的基础上，分别讨论了采后苹果在室内冷却过程中风速、局部平均风龄、温度、局部体积熵产生率和焓耗散的分布特征。 . 进一步分析了不可逆参数与表观异质性之间的关系。结果表明，较高的局部平均空气年龄和箱内温度是由附近较低的空气速度导致的，并且在房间冷却过程中较长的持续时间也可以获得明显的箱表面熵产生和焓耗散的局部体积率。不可逆性参数，包括熵产生和焓耗散的局部体积率，与当地平均空气年龄相关，皮尔逊系数在 0.60 和 0.80 之间，与温度相关性更好，皮尔逊系数高于 0.80。在房间冷却过程中，在较长的持续时间内，也可以在箱体表面获得显着的局部体积率的熵产生和熵耗散。不可逆性参数，包括熵产生和焓耗散的局部体积率，与当地平均空气年龄相关，皮尔逊系数在 0.60 和 0.80 之间，与温度相关性更好，皮尔逊系数高于 0.80。在房间冷却过程中，在较长的持续时间内，也可以在箱体表面获得显着的局部体积率的熵产生和熵耗散。不可逆性参数，包括熵产生和焓耗散的局部体积率，与当地平均空气年龄相关，皮尔逊系数在 0.60 和 0.80 之间，与温度相关性更好，皮尔逊系数高于 0.80。