Performance study of supplying cooling load and output power combined cycle using the cold energy of the small scale LNG
Performance study of supplying cooling load and output power combined cycle using the cold energy of the small scale LNG
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DOI：
10.1016/j.energy.2019.01.094
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发表时间：
2019-04
期刊：
影响因子：
9
通讯作者：
Jinghong Ning;Zhili Sun;Q. Dong;Xing-De Liu
中科院分区：
文献类型：
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作者：
Jinghong Ning;Zhili Sun;Q. Dong;Xing-De Liu
小流量液化天然气的气化过程还释放大量的冷能和压力能。为了有效利用冷能和压力能，提出了一种提供冷负荷和输出功率的联合循环。联合循环中，一个制冷循环用于食品冷冻储藏，两个制冷循环用于食品冷却储藏，两个冷冻水循环用于空调，制冷循环工质采用R717。分析了联合循环的火用效率和性能系数。制冷循环中蒸发器的火用效率最低，各膨胀机和冷凝器的火用效率均高于泵。蒸发器、膨胀机、泵和冷凝器的火用效率随着R717制冷剂蒸发温度的升高而增加。空调各冷冻水泵的耗电量高于制冷循环中R717泵的耗电量。 LNG泵的功耗比两台冷冻水泵低。随着NG膨胀机出口压力降低，NG膨胀机入口压力升高，泵总功耗和系统总膨胀输出功率增大。系统总膨胀输出功率中，NG膨胀机占2/3以上。随着NG膨胀机出口压力的增加，系统火用效率和联合循环性能系数降低。随着NG膨胀机入口压力的增加，系统的火用效率增加。然而，NG膨胀机的入口压力升高，导致系统性能系数降低。并且在天然气膨胀机进出口压力相同的情况下，天然气质量流量增加，系统的火用效率和性能系数几乎没有变化。当天然气质量流量为1kg/s，天然气膨胀机进出口压力分别为10000kPa和600kPa时，系统火用效率和性能系数分别达到85.19%和6.525。
The gasification process of small flows of liquefied natural gas also releases large amounts of cold energy and pressure energy. In order to effectively utilize the cold energy and the pressure energy, a combined cycle for supplying cooling load and output power was proposed. In the combined cycle,one refrigeration cycle for food frozen storage, two refrigeration cycles for food cooling storage, two chilled water cycles for air conditioning, R717 is used as working substance of refrigeration cycles. The exergy efficiency and performance coefficient of the combined cycle were analyzed. The exergy efficiency of evaporator is the lowest, the exergy efficiency of each expander and condenser is higher than that of the pump in refrigeration cycles. The exergy efficiency of evaporator, expander, pump and condenser increases with the increase of evaporation temperature of R717 refrigerant. The power consumption of the each chilled water pump for air conditioning is higher than that of the R717 pumps in refrigeration cycles. LNG pump power consumption is lower than that of two chilled water pumps. As the outlet pressure of the NG expander decreases, and the pressure at the inlet of the NG expander increases, the total pump power consumption and the system total expansion output power increases. Among the system total expansion output power, NG expander accounts for more than 2/3. With the increase of the outlet pressure of the NG expander, the system exergy efficiency and the performance coefficient of combined cycle decreases. With the increase of the inlet pressure of the NG expander, the exergy efficiency of the system increases. However the inlet pressure of NG expander rises resulting in reduction in the performance coefficient of the system. And at the same inlet and outlet pressure of NG expander, the mass flow rate of NG increases, the exergy efficiency and the performance coefficient of the system hardly changes. When the mass flow rate of NG is 1 kg/s, and the inlet and outlet pressures of NG expander are 10000 kPa and 600 kPa, the exergy efficiency and the performance coefficient of the system reaches 85.19% and 6.525 respectively.