LNG冷能驱动的氨水吸收式制冷系统的性能研究

Performance Study of Ammonia-water Absorption Refrigeration System Driven by LNG Cold Energy

本文提出了一种新型的以冷制冷的氨水吸收式制冷系统。系统利用LNG气化释放的冷能作为冷源,通过少量的高品位冷能的利用来制取多量的低品位冷能,制冷循环采用氨水吸收式制冷系统。通过对系统的热力分析表明:当制冷温度(蒸发器蒸发温度)为0℃,蒸馏率为0.185,LNG冷能输入系统的温度为-60℃时,系统的性能系数为1.74。在此条件下对系统进行火用分析,发现吸收器的火用损失最大,其火用损系数约为24%,系统总的火用效率为41%。对系统进行特性规律分析,发现当蒸发器的蒸发温度不变时,发生器氨气蒸馏率的增加会使得发生器操作压力下降,LNG冷却温度下降,但同时系统的性能系数会增加。蒸馏温度越高,系统的性能越好,当制冷温度为10℃时,系统的性能系数可以达到1.8以上。

In this paper,a new model for ammonia-water absorption refrigeration system is proposed and analyzed. Cold energy which is released from the LNG(Liquefied Natural Gas) vaporization will be used in the system as a low-temperature receiver,and a small amount of high-grade cold energy is absorbed by the system and then relatively large amount of low-grade cold energy is produced. Ammonia-water absorption refrigeration system is adopted in refrigeration cycle. Thermodynamic analysis of the system shows that when the refrigeration temperature(the distillation temperature of evaporator) is 0 ℃,the distillation ratio reaches 0. 185 and as the temperature of the LNG input into the system is -60 ℃,the coefficient of performance of the system is 1. 74. Under this condition,the system is analyzed by exergy analysis method. The result shows that the exergy loss of abstraction is the largest among several equipments,approximately 27%,and the overall exergy efficient of the system is 41%. The characteristics of the system are analyzed and it is found that when the distillation temperature of evaporator is constant,with the increase in the distilled ammonia from the top of distillation column,the operating pressure of the distillation column will di-minish,the vaporization temperature of LNG will decrease and the quantity of heat absorbed by system will decrease. However,at the same time,the coefficient of performance of the system will rise. Good performance can be gained when the evaporating temperature gets higher. The coefficient of performance of the system can reach above 1. 8 with the refrigeration temperature of 10 ℃.