Thermodynamic Analysis of a Marine Refrigeration Machine with Ammonia

Abstract

The purpose of this study is to present a thermodynamic modeling of a marine chiller using ammonia as a refrigerant. The modeling is based on the first and second laws of thermodynamics and the fundamental laws of heat transfer. System performance in terms of coefficient of performance, total exergy losses and exegetic efficiency, have calculated the temperatures of sea water and air in puts, respectively, of the condenser and evaporator and their exchange surfaces. The thermodynamic properties of the refrigerant were calculated using simple and reliable state equations. The results showed that the exergy efficiency can, in some cases; do not follow the behavior of the coefficient of performance. In this study, a thermodynamic modeling of a marine refrigeration machine using ammonia as refrigerant was presented. The results showed that the performance of the machine increases as the temperature of the air entering the evaporator increases. On the other hand, an increase in the temperature of the sea water decreases this performance. In addition, the increased surfaces of the heat exchangers (condenser and evaporator) increase the performance of the machine because the formula for the quantity of heat exchanged with the external environment is Q = KXSXΔT (K: Is the heat exchange coefficient, ΔT: Is the temperature variation between the two media and S: Is the exchange surface), therefore the larger the surface, the better the exchange, which makes the performance better. In addition, we observe that the exegetical parameters may in some cases not match the COP.