Vapor compression systems are a popular thermal management solution for high heat load applications because they benefit from the high heat transfer rate of two-phase fluid flow. However, model-based design and control of these systems proves challenging because of the complex and coupled hydro-thermal dynamics as the working fluid changes phase in the heat exchangers. When modeling these heat exchangers, there exists a strong tradeoff between model accuracy and computational complexity. While different techniques have aimed to reduce computational complexity of the model, they come at the cost of a decrease in accuracy. On the other hand, high fidelity models are computationally expensive to run. To bridge the gap between computational efficiency and accuracy, this work develops a novel multi-state graph-based dynamic modeling approach. The multi-state graph modeling approach is used to develop a dynamic model of a two-phase heat exchanger. The heat exchanger model is integrated into a vapor compression system model and the model behavior is verified against other models present in the literature. The results demonstrate that the multi-state graph model can accurately capture system dynamics within 1% of the current state of the art modeling approaches while providing valuable modularity for system level modeling. Additionally, the computational load can be made comparable to less accurate approaches.
Bibliographical noteFunding Information:
This work was supported by a University of Illinois at Urbana-Champaign graduate fellowship and the National Science Foundation Engineering Research Center for Power Optimization of Electro Thermal Systems (POETS) with cooperative agreement EEC-1449548.
- Computationally efficient
- Dynamic modeling
- Heat exchanger
- Refrigeration system