Dynamic modeling and control of multi-evaporator air-conditioning systems

This paper presents a new methodology for the dynamic modeling of multi-evaporator air-conditioning cycles. The resulting model is suitable for designing advanced closed-loop controllers for these systems. A generalized modeling approach is developed, which is applicable to commercially available units with any number of evaporators. Model validation against data from an experimental dual-evaporator system for step inputs to compressor speed and expansion valve opening is also presented, and the results show good prediction accuracy. The open-loop behavior observed in these simulation studies clearly indicates the effect of cross-coupling between dynamic variables of different evaporators. Finally, closed-loop control strategies based on the model and the system characteristics are discussed, and comparison of two control strategies for control of pressure and superheat of the two evaporators is also presented.