Low-temperature ammonia absorption refrigeration system based on the temperature difference uniformity principle: Optimization analysis

Abstract

AARS (ammonia absorption refrigeration system) is one of the effective ways to utilize low-temperature waste heat below 100 °C for industrial applications. This novel system of LT-AARS is designed based on the principle of temperature difference uniformity for improving the overall COP. The partial condenser at the distillation section is adopted to achieve the purity of ammonia to more than 99.9 % with a small reflux ratio. A thermodynamic model is established to analyze the influence of the optimized distillation process on system performance and exergy loss. These modifications reduce the temperature difference uniformity factor from 1.12 to 1.025 and improve the COP from 0.414 to 065. Meanwhile, it is proved that the LT-AARS protocol is reasonable and effective by comparing the experimental values with the theoretical model. The exergy loss of the absorber and distiller accounts for about 55 % of the total exergy losses of LT-AARS. With the increases in refrigeration temperature from −15 to 5 °C and heat source temperature from 80 to 100 ℃, the COP can reach a maximum of 0.77. ECOP first increases sharply and then decreases slowly with the increase of refrigeration and heat source temperature, and ECOP has a maximum value. The optimal range of △x for LT-AARS varies from 5 % to 10 %. The COP and ECOP of the LT-AARS are more than 0.6 and 0.3, respectively.