Mass, energy and exergy analysis of cooling system of a beverage plant

In this study, vapor compression cooling system of a beverage plant was investigated thermodynamically using hourly data that was recorded once for four weeks. There are two refrigerant cycles; primary refrigerant is ammonia and secondary refrigerant is mixture of monoethylene glycol-water in the system. Firstly, mass analyses were carried out and refrigerant mass flow values for control volumes were obtained by using conservation of mass equation. Energy analyses were realized by using mass flow rates as second phase. Heat and work interactions were determined for control volumes using conservation of energy equation in accordance with assumptions for control volumes. Also COP values were obtained by carrying out energy analysis. Exergy analyses were carried out by using mass flow rates, heat and work values obtained for control volumes in cycle as last phase. Exergy losses occurred in control volumes were determined by using exergy balance equation in accordance with assumptions for control volumes. The biggest exergy losses were occurred in compressors (%59.53) followed by evaporators (%27.86), expansion valves (%7.11) and condensers (%5.5). Besides, inputs of exergy to control volumes were obtained by using exergy analysis. Thus exergy efficiencies of control volumes were determined by using exergy losses and inputs exergy values. In this study, it was observed that exergy losses, exergy efficiencies and COP values determined for control volumes were investigated for different refrigerant mass flow rates, evaporator temperatures and time. The values obtained were given in graphical forms. It was observed that system which was operated in low capacities causes exergy losses highly increase and exergy efficiencies and COPR values decrease significantly. Superheating, subcooling and decreasing temperature of condenser are not applied in the plant. Effects of the applications on an ideal cycle were investigated and in this regard optimization options were discussed by considering the biggest exergy loss in compressors.