Absorption refrigeration system utilising engine exhaust gas for bulk gas carriers

Abstract

This study demonstrated the feasibility of an absorption refrigeration system (ARS) that is capable of utilising the engine exhaust gas of bulk gas carriers as the heat source and generating cooling source either for reliquefaction of the boil-off gas (BOG) or for heating, ventilating and air conditioning. The ARS employed an NH3/H2O mixture as the working fluid. The process was designed and simulated using the properties of the exhaust gas from the commercially available engines. The coefficient of performance increased with the temperature of the generated cooling source. A decrease in the engine load resulted in a decrease in the exhaust flow rate and, consequently, in a decrease in the cooling capacity. Although the exhaust temperature reached its minimum around the normal continuous rating, the dependence of the cooling capacity on the engine load was not significantly affected. A case study for a liquefied natural gas carrier verified that the refrigeration system afforded a sufficient cooling capacity to satisfy both the required work and the temperature level needed for reliquefaction of the BOG.