OTEC增温再热朗肯动力循环分析

Analysis of Temperature-Increasing Based OTEC Cycle

本文提出了一种OTEC(OTEC,Ocean Thermal Energy Conversion)增温再热朗肯动力循环,通过第二类吸收式热泵提升热源品质,在热力循环中创造一个相对高温区,与表层温海水共同对朗肯循环的湿工质进行过热,保证了透平出口干度,提升了循环的平均吸热温度,实现了单一热源下的梯级加热和能级匹配,系统效率得到较大的提升。论文构建了OTEC增温再热朗肯动力循环热力学模型,对比了增温再热朗肯动力循环与传统循环的热力性能,并分析了热泵子循环的最佳增温温度。结果表明:增温再热的效果与OTEC循环工质有较大关联,且存在最佳增温温度;对于采用R134A等近似等熵工质的OTEC循环,增温再热的热力性能提升不明显;而对于CO_(2)等工作在亚临界区间的工质而言,增温再热可使热效率提升19.63%41.71%;对于NH3等过热需求较大工质而言,增温再热具有显著的提升效果;其中NH3工质的提升幅度最高,最佳增温温度为42.5°C,OTEC循环热效率可由2.34%提升至4.25%,升幅达84.45%。

A temperature-increasing based OTEC (Ocean Thermal Energy Conversion) cycle is proposed in this paper.Based on the combined of the heat pump cycle and the power cycle,a relatively high temperature region is created in the cycle to heat the working fluid together with the heat source of surface warm seawater,which guarantees the dryness of the working fluid at the turbine outlet and so that improves the average heat absorption temperature of the cycle.The thermodynamic model of temperature-increasing based OTEC cycle was established,the thermodynamic performance comparison between the proposed cycle and traditional cycle was made.Besides,the optimal temperature-increasing value of heat pump sub-cycle was analyzed.The results show that the effect of reheating is related to the working fluid of the OTEC cycle,and there exists an optimal temperature-increasing value;for the OTEC cycle using R134a and other approximate isentropic refrigerants,the thermodynamic performance of the proposed cycle is not significantly improved;for CO_(2)of which working in the subcritical region,the thermal efficiency can increase by 19.63%~41.71%;for NH3and other working fluids with large demand for superheat,the OTEC cycle performance can be significantly improved;NH3based cycle has the best performance,and the optimal temperature-increasing value is 42.5°C.The thermal efficiency can be increased from 2.34% to 4.25%,with an increase of 84.45% compared to traditional cycle.