Experimental investigation on binary ammonia–water and ternary ammonia–water–lithium bromide mixture-based absorption refrigeration systems for fishing ships

Abstract

Heat recovery of marine engine exhaust gas is an effective way of improving the onboard fuel economy and environmental compliance of fishing ships. Among such heat recovery techniques, the absorption refrigeration cycle shows potential as it can convert the exhaust thermal energy into refrigeration output and meet the onboard refrigeration requirement. However, the severe operating conditions on the shipboard poses a great challenge for its application. This paper presents an experimental investigation of an absorption refrigeration system for the heat recovery of marine engine exhaust gas. To overcome the adverse effect of the severe onboard condition on the rectification process of the absorption refrigeration system, a ternary ammonia–water–lithium bromide mixture is selected as the working fluid. A prototype of the absorption system is designed and an experimental investigation is conducted. Then, the performances of both the ternary ammonia–water–lithium bromide-based system and binary ammonia–water-based system are compared. The results show that the rectifier heat exchange area can be reduced by approximately 16% under the experimental working condition. Furthermore, the ternary system operates at a relatively lower pressure, with a refrigeration temperature of less than −15.0 °C, which is higher compared to the temperature of less than −23.6 °C associated with the binary system. Nevertheless, the ternary system achieves a remarkably higher cooling capacity. Moreover, by using the ternary ammonia–water–lithium bromide mixture, the heat loss of the prototype is reduced while the coefficient of performance and electric coefficient of performance are increased, indicating that the ternary system has a higher energy conversion efficiency.