The paper presents the dynamic characterization of a novel CO₂ system designed for the refrigerated transport sector, when equipped to a medium-size refrigerated truck, during a daily typical long-distance delivery mission. The system takes advantage of a two-phase ejector to improve its performances and an auxiliary evaporator to extend the ejector operating range towards mild ambient temperatures. The system is designed allowing the possibility to switch between different configurations during operation, in order to maximize the COP or the refrigerating capacity, as a function of internal air and external environmental conditions. A numerical model of the system and its control strategy is developed using a 0-D dynamic commercial software, and coupled with a validated model of a refrigerated body. Simulation results show an average COP equal to 1.60 and an overall Duty Cycle of 10% for the delivery mission. The 96.6% of the total cooling energy is provided exploiting both the main and the auxiliary evaporator; however, dynamic simulations allowed highlighting that using the configuration exploiting both the evaporators during the hottest moments of the day can become counterproductive. Moreover, the behavior of the two-phase ejector under different environmental air temperature conditions is investigated. The maximum values of the average ejector efficiency (10.1%) and of the average pressure lift (1.59 bar) are reached for the highest external ambient temperatures (36.0 °C). Finally, to avoid the temperature and pressure drift inside the low pressure side of the refrigerating system during a long time of inactivity, an innovative safety control system based on the definition of a maximum allowed pressure level inside the low pressure side of the cooling unit is proposed.

本文介绍了新型CO ₂的动态表征在日常的长途运输任务中，当为中型冷藏车配备冷藏系统时，该系统是专门为冷藏运输行业设计的。该系统利用两相喷射器来改善其性能，并利用辅助蒸发器将喷射器的工作范围扩展到温和的环境温度。该系统的设计允许根据内部空气和外部环境条件，在运行期间在不同配置之间进行切换，以使COP或制冷能力最大化。该系统的数值模型及其控制策略是使用0-D动态商业软件开发的，并与经过验证的冷冻机体模型相结合。仿真结果显示，交付任务的平均COP等于1.60，总占空比为10％。利用主蒸发器和辅助蒸发器可提供总冷却能量的96.6％；但是，动态模拟可以突出显示在一天中最热的时刻使用同时利用两个蒸发器的配置会适得其反。此外，研究了两相喷射器在不同环境空气温度条件下的行为。对于最高的外部环境温度（36.0°C），达到平均喷射器效率（10.1％）和平均压力升程（1.59 bar）的最大值。最后，为避免长时间不活动，制冷系统低压侧的温度和压力漂移，