Rotary heat exchanger model for control and energy calculations

Rotary heat recovery exchangers are widely used in ventilation systems, and the units are known for their high efficiency and almost maintenance-free operation. Temperature efficiencies above 80% are not uncommon. Performing dynamical analyses of rotary heat exchangers are in many situations advantageous, especially in connection to installation of such equipment in VAV systems. Efficiencies and flows are varying parameters that are crucial for energy calculations, but also for control. The dynamical analysis can effectively be carried out by addressing a dynamical model. This paper presents a simplified model for a rotary heat recovery unit that can be used both in CAV or VAV systems for control and energy analysis. The model is based on a further development of existing models, and is able to account for varying leakage, varying flows and temperatures. The model has been implemented in the Matlab Simulink environment. Simulations show that the results represent real conditions in an adequate way. This has been verified through comparison with measurements.