Refrigerator system modeling and validation

This paper reports the dynamic characteristics of an ammonia refrigerator system developed based on mass and energy conservation equations in lumped parametric form for the evaporator, condenser, expansion valve and reciprocal compressor. The dynamic behavior of the refrigerator system is observed with perturbations in expansion valve opening rate and compressor rotation speed. As a result, the behavior of ammonia-refrigerant vapor compression cycle is observed in terms of safety of the compressor from entering liquid ammonia and effective use of the evaporator. In order to design an appropriate controller to manipulate the expansion valve and compressor, it is necessary to have an overall dynamic behavior investigation for the system including the secondary fluid flow systems in the heat exchangers. The developed model is validated using experimental data with sudden step changes in expansion valve opening rate and compressor rotation speed.