天然气冷热电三联供系统热力学分析

Thermodynamic analysis of natural gas-fired combined cooling,heating and power system

天然气先经过燃气轮发电机发电,然后利用燃气轮机排出的高温烟气推动吸收式制冷机制冷,最后利用换热器回收中温烟气中的余热加热生活热水,这种冷热电三联供方式能够显著地提高能源的利用效率。构建了天然气为燃料冷热电三联供系统典型的模型图和能流图,导出了系统各环节能量和的计算公式、三联供系统的总能量和利用率以及各部位的损失;基于能源产品的市场价格,给出了三联供系统的经济收益。以现有技术设备和典型操作工况为基础,分析讨论了环境温度以及燃气轮发电机和制冷机出口烟气温度对供冷、供热、能量利用率、利用率以及经济收益的影响。结果表明,环境和烟气的温度对系统的性能和收益都有一定的影响。

Natural gas is first used to generate electric power through micro-turbine generator, and then the high temperature exhaust gas from the turbine is used to drive absorption chiller to produce cooling, and the middle temperature flue gas from the chiller is finally used to provide domestic hot water by heat exchanger. This energy process embodies the energy cascade utilization principle. A typical model and its energy flow diagram of natural gas-fired combined cooling, heating and power （CCHP） were constructed; and the energy equations, exergy equations and exergy destructions on different sites of CCHP were deduced; the energy efficiency, exergy efficiency and economic incomes were also mathematically defined ; the influences of temperatures on cooling load, heat load, energy efficiency, exergy efficiency and economic incomes were discussed and analyzed according to the current technique and the typical operational conditions. The result shows that the thermodynamic performance and incomes of CCHP are affected by the temperatures of ambient and exhaust gas, which provides some theoretical instructions for the design, optimization and operation of CCHP.