An accurate low-order model of a fin-and-tube heat exchanger for the dynamic simulation of heat pumps

Dynamic modeling of heat exchangers is essential for the analysis, control, and optimization of vapor compression systems such as heat pumps and air conditioners. These technologies are increasingly relevant in the context of energy transition, where regulatory frameworks and climate goals demand improved energy efficiency and reduced greenhouse gas emissions. Accurate yet computationally efficient models are crucial for system-level simulation, control design, and digital twin development. Traditional low-order approaches, such as lumped-parameter and moving boundary models, offer fast computation but often lack the fidelity needed to capture dynamic two-phase phenomena, especially under transient or off-design conditions. Finite volume models offer better accuracy but are often too computationally demanding for real-time applications. This work presents a segment-by-segment heat exchanger model that balances accuracy and efficiency, allowing for detailed prediction of dynamic behavior with limited computational cost. The model was developed using the Simscape language within the Simulink® environment and validated in both condenser and evaporator modes. Numerical comparisons with EVAP-COND 5.0 showed a maximum deviation of 2.7% for sensible heat transfer in condenser mode, and 6.8% and -2.4% for latent and sensible heat transfer in evaporator mode, respectively. Moreover, steady-state experimental validation corroborated these results, with overall heat flow rate predictions consistently within a  ± 10% error band. Thanks to this dual numerical and experimental validation, the proposed model provides a reliable tool for designing advanced, energy-efficient HVAC systems under stringent regulatory frameworks.