Switchover control strategies for improving performance of refrigeration systems under off-design conditions

A typical 3-ton vapor compression refrigeration system using R-22 as the re frigerant is addressed. Two models are developed: a design model and a hier archical control model. The design model is operated to observe the respons e of a typical system under various off-design operating conditions. In lie u of laboratory experiments. the normalized responses from the design model (normalized with respect to the design conditions) are compared to the nor malized values based on the experimental data reported in the literature. T his is done to validate the design model to the extent possible, limited by the reported experimental data in the literature. From this design model a hierarchical control model is developed, in which different control techni ques fors system capacity regulation and for operation over a range of ambi ent temperature are employed. BY varying corresponding control parameters i n each technique, information is developed regarding the refrigerant condit ions within the system and system performance under different operating con ditions. From the results of these simulations, hierarchical or switchover control strategy for an integrated refrigeration system is postulated to ac hieve the specific operational requirements with the highest feasible syste m efficiency over a wide range of off-design operating conditions. A simila r approach can be used to postulate different hierarchical control based on other performance measures and considerations.