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Dynamic Modeling of Chilled Water Cooling Coils 冷冻水冷却盘管的动态建模
1194-RP的目标是为冷却盘管开发计算效率高、充分验证且有充分记录的瞬态模型。首先,使用具有简化几何结构的逆流式热交换器的详细模型评估简化建模的假设。研究发现,盘管外表面凝结水的瞬变可以忽略,在除湿条件下,路易斯数的单位是有效的。集总鳍效率法适用于瞬态线圈分析。然而,在潮湿条件下,推导出了显热传热的修正翅片效率。 然后,针对真实的换热器几何结构,开发了更简化的模型,包括用给定的盘管物理描述求解瞬态能量平衡。研究了数值求解技术的影响,并确定了一个简化模型,该模型代表了精度和计算要求之间的良好折衷。使用从实验室测试的两个不同线圈获得的数据进行了彻底的实验验证。将该模型与文献中现有的简化模型进行了比较,证实了该模型能够更好地预测冷却盘管的瞬态性能。 最后,在正演模型的基础上建立了一个更简单的反演模型,并提出了一种两步参数估计方法。两种模型都用C++编码,并作为一个DLL文件实现,可以在MATLAB中调用。本项目开发的瞬态模型可用于测试反馈控制器以及故障检测和诊断方法。
The objective of 1194-RP was to develop computationally efficient, fully validated, and well-documented transient models for cooling coils. First, assumptions that simplify the modeling were evaluated using a detailed model for a counter-flow heat exchanger with a simplified geometry. It was found that transients associated with water condensate on the coil outer surface can be neglected and a Lewis number of unity is valid under dehumidifying conditions. A lumped fin efficiency approach is applicable to transient coil analysis. However, a modified fin efficiency for sensible heat transfer was derived for wet conditions. More simplified models were then developed for realistic heat exchanger geometries, which involve solving transient energy balances with a given coil physical description. The impact of numerical solution techniques was investigated, and a simplified model was identified that represents a good compromise between accuracy and computational requirements. A thorough experimental validation was performed using data obtained from two different coils tested in the laboratory. The model was compared with existing simplified models available in the literature and confirmed to provide improved predictions of cooling coil transient performance. Finally, a simpler inverse model was developed on the basis of the forward model and a two-step approach for parameter estimation was presented. Both models were coded in C++ and implemented as a DLL file that can be called in MatLab. The transient models developed in this project are useful for testing feedback controllers and fault detection and diagnostic methods.
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