CAJ | 학술논문

差压预冷能够快速降温，是果蔬采后处理的重要方法，温度是整个过程的核心，为了更精准地监控预冷包装小环境的温度变化，该文充分考虑果品采后的呼吸热和蒸腾潜热，建立包装箱内带衬垫层装球形果品的差压预冷数学模型，基于计算机流体力学，借助Fluent软件采用标准κ-ε模型和SIMPLE算法，利用UDF（user define function）模块实现热源项的加载，模拟包装箱侧面上开孔率为11.2%的圆形、键槽形2种开孔工况下间隔、平方间隔和错位间隔3种排列果品的瞬态温度场，并进行试验测试比较，得到的温度变化与模拟结果吻合性较好，验证了所建模型的可靠性。平方间隔排列时果品的温度分布较均匀，间隔排列时整体预冷较慢；水果内部存在温度梯度，表面和中心温度相差高达7℃左右；键槽形开孔利于冷风的横向扩散，错位间隔时较圆形开孔预冷均匀度提高约10%，温度低2℃。预冷时建议开孔设计与内部果品的排列相协调改善气流组织，错位间隔排列时键槽形开孔较宜。
차압예랭능구쾌속강온，시과소채후처리적중요방법，온도시정개과정적핵심，위료경정준지감공예랭포장소배경적온도변화，해문충분고필과품채후적호흡열화증등잠열，건립포장상내대츤점층장구형과품적차압예랭수학모형，기우계산궤류체역학，차조Fluent연건채용표준κ-ε모형화SIMPLE산법，이용UDF（user define function）모괴실현열원항적가재，모의포장상측면상개공솔위11.2%적원형、건조형2충개공공황하간격、평방간격화착위간격3충배렬과품적순태온도장，병진행시험측시비교，득도적온도변화여모의결과문합성교호，험증료소건모형적가고성。평방간격배렬시과품적온도분포교균균，간격배렬시정체예랭교만；수과내부존재온도제도，표면화중심온도상차고체7℃좌우；건조형개공리우랭풍적횡향확산，착위간격시교원형개공예랭균균도제고약10%，온도저2℃。예랭시건의개공설계여내부과품적배렬상협조개선기류조직，착위간격배렬시건조형개공교의。
Forced-air precooling is more conductive to achieve a rapid cooling, and it is widely applied in the commercial processing treatment of fresh produce after harvest and recognized to be an efficient cooling method. Emphatically, the temperature plays a critical role during the whole cooling process that influencing the comfort of packed fruits and then the shelf life. In order to predict and monitor the temperature changes of produce inside the ventilated packages, a transient mathematical model was developed that considering the latent heat source due to respiration and evaporation of spherical fruits inside tray-layered packaging box during forced-air precooling process. Based on computational fluid dynamics, Fluent TM 2.3.26 along with the standard k-ε model and SIMPLE algorithm for the pressure velocity coupling solution was employed to simulate the three-dimensional transient temperature field of layered fruits in forced-air precooling. Particularly, the inner heat source was added to the energy equation and loaded to the numerical solution dynamically by UDF (user defined function) for interpreting corresponding heat source files. Temperature fields of fruits stacked in three different patterns (spaced stacking pattern, paralleled stacking pattern and crossed stacking pattern) in different ventilated packages with circle and oblong side vents in the same opening area of 11.2%were analyzed. The experimental validations were performed, and the simulated data agreed well with the experimental results. Thus the mathematical model was reliable and can be used to the research of produce precooling. It is demonstrated that temperature distribution was more homogeneous for fruits in paralleled stacking pattern, while the slowest cooling rate and the highest temperature of fruit for spaced stacking pattern condition. What’s more, the temperature gradient in fruit can not be ignored for the center temperature and surface temperature difference up to about 7℃. Additionally, oblong vents design can balance the lateral and longitudinal diffusion of inlet airflow and ease the turbulent fluid inside packages for promoting the overall cooling rate and uniformity. Specifically for fruits in crossed stacking pattern, the cooling uniformity of oblong vents condition increased by about 10%and the slowest cooling temperature of fruit was 2℃ lower compared with the circle vents condition. As a result, ventilated packaging design for cooling fruits should be in tune with the internal stacking pattern as well as the trays to adjust the airflow and provide a adequate but uniform cooling environment, and for tray-layered fruits in crossed stacking pattern, oblong vents configuration with large ratio of the major axis to the minor axis can be suggested as better ventilated packaging design.