Design optimisation of CO2 gas cooler/condenser in a refrigeration system
Design optimisation of CO2 gas cooler/condenser in a refrigeration system
复制标题
制冷系统中二氧化碳气体冷却器/冷凝器的设计优化
DOI：
10.1016/j.apenergy.2015.01.123
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发表时间：
2015
期刊：
影响因子：
11.2
通讯作者：
Ge Y
中科院分区：
文献类型：
--
作者：
Ge Y
作为一种天然工质，CO2在制冷系统中得到了广泛的应用，传统的制冷系统是通过外部气流将热量释放到环境中的。由于其特殊的热物性，特别是低临界温度，通过高压侧换热器的CO2热释放将不可避免地经历超临界或亚临界过程，这取决于环境空气温度和头部压力控制。相应地，在年度运行期间，换热器将间歇性地充当系统内的气体冷却器或冷凝器。为实现这些目标，特意建造了两个不同结构设计和控制的二氧化碳翅片管式气体冷却器/冷凝器，并与现有的二氧化碳增压制冷系统试验台连接。因此，可以通过实验来深入研究不同结构设计、控制和系统集成的CO2气体冷却器/冷凝器在不同运行条件下的性能。同时，采用分布式(详细模型)和集中(简单模型)两种方法建立了翅片管式CO2气体冷却器/冷凝器的模型。前者用于对工质温度分布、局部换热速率和管路布置的影响进行详细的预测，而后者适用于系统集成的模拟和优化，计算时间较短。这两个模型都经过了测量验证，而且简单的模型已经与其他组件模型集成在一起，从而创建了一个系统模型。因此，可以比较和分析二氧化碳气体冷却器/冷凝器的尺寸和控制对系统性能的影响。
As a natural working fluid, CO2has been widely applied in refrigeration systems where heat is conventionally released to ambient through external airflow. Owing to its extraordinary thermophysical properties, especially a low critical temperature, the CO2heat release through a high-pressure side heat exchanger will inevitably undergo either supercritical or subcritical processes, depending on ambient air temperatures and head pressure controls. Correspondingly, the heat exchanger will act intermittently as either a gas cooler or condenser within the system during an annual operation. Such evidence should therefore be taken into account for an optimal design of the heat exchanger and head pressure controls in order to significantly enhance the performance of both components and the associated system.To achieve these targets, two CO2finned-tube gas coolers/condensers with different structural designs and controls have been purposely built, instrumented and connected with an existing test rig of a CO2booster refrigeration system. Consequently, the performance of the CO2gas coolers/condensers with different structure designs, controls and system integration at different operating conditions can be thoroughly investigated through experimentation. In the meantime, models of the finned-tube CO2gas coolers/condensers have been developed using both the distributed (detailed model) and lumped (simple model) methods. The former is employed to give a detailed prediction of the working fluid temperature profiles, localised heat transfer rates and effects of pipe circuitry arrangements, while the latter is suitable for the simulation and optimisation of system integration with less computation time. Both models have been validated with measurements, and moreover the simple model has been integrated with other component models so as to create a system model. The effects of the CO2gas cooler/condenser sizes and controls on the system performance can thus be compared and analysed.