CAJ | 학술논문

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。
위연구과소랭격과정중내부조직전열특정，근거과소생리결구특정건립병험증료주상과소적분층전열모형。이용소건모형분석료이공기화랭수위처리개질시류속、과소척촌、조직열물성차이대황과랭격전열과정적영향。결과표명，소건모형재황과중심、거중심2R/5급4R/5（R위황과반경）처적평균온도오차（MEE）분별위0.423、0.377화0.842℃，최대절대오차（MAE）위1.713℃，구유교고정도。공기류속유1 m/s증지5 m/s과정중，황과강온속솔증폭교대，대류환열열조대전열과정영향교대；수류속도유0.2 m/s증지1.8 m/s과정중，황과중심처강온속솔증폭교소，과소내부열조대전열과정구유교대영향。이수위처리개질시，물성차이적영향대우이공기위처리개질시적영향。연구결과가위과소랭격처리공예우화제공이론삼고。
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, the cooling rate of cucumber tissue conducted with chilling air was slower during cold shock treatment. This type of cooling required longer duration of cold shock treatment, and the temperature gradient was smaller along the radius of the cucumber, which resulted that chilling stresses experienced by all cucumber tissues were similar. Therefore, cooling medium should be selected according to the heat transfer characteristics of fruits and vegetables with different cooling mediums. The cooling rate increased largely with increased airflow speed of chilling air, which increased from 1 m/s to 5 m/s, and the convective heat resistance had great influence on the whole heat transfer process, so air speed should be improved to reduce the required duration of cold shock treatment. When the water velocity increased from 0.2 m/s to 1.8 m/s, the cooling rate of the cucumber increased by small amplitude, especially when it was more than 0.6 m/s, and the heat resistance of inner cucumber had a significant effect on the whole cooling process. The water speed should be reduced to lower the energy consumption of circulating pump. The thermophysical property difference had greater influence when cold water was used than that when cold air was used. The results can provide theoretical reference for optimizing the process parameters in cold shock treatment of postharvest fruits and vegetables.