海洋温差发电混合工质热力循环二次热回收影响机理研究与试验验证

Ocean thermal energy has the largest reserves among ocean energy. Efficiency of the thermodynamic cycle is the research hotspot and difficult to the utilization of ocean thermal energy conversion (OTEC) due to available temperature difference is small. Research group has constructed a new thermodynamic cycle which uses ammonia-water mixture as working fluid on the basis of preliminary studies. In addition to the existing improvement method, depleted ammonia solution secondary heat recovery was added to the system and then the efficiency of the cycle was improved. The project plans to use the freon mixed working medium which is safety and has little influence on the environment. After that apply thermodynamic principle to reveal the internal relations and mechanism between the thermodynamic cycle efficiency and secondary heat recovery. Then combined with numerical simulation, quantitative analysis of the influence of secondary heat recovery on nodal parameters and efficiency will be carried out. After that the relationship between the optimal concentration of the working fluid and efficiency of cycle under different temperature differences conditions will be achieved. Then verify the validity and accuracy of the numerical algorithm by comparing the simulated result with operating data of the testing system and obtain the optimal operation condition of the system. This study will lay the theoretical foundation and provide scientific basis for engineering application of OTEC.

海洋温差能是海洋能中储量最大的可再生能源，因可利用的海洋温差较小，热力循环方式是该研究的热点和难点。本课题组在前期研究的基础上，采用氨-水混合工质构建新热力循环，增加贫氨溶液二次热回收装置，并进行数值计算与分析。本课题拟利用安全、对环境影响小的氟利昂混合工质，运用热力学基本原理，揭示二次热回收与循环热力性能之间的内在关系，结合数值模拟，定量分析增加二次热回收后，对循环系统各节点参数和循环热力性能的影响，得到不同温差下，混合工质浓度和循环热效率之间的关系。同时与本单位正在调试的试验系统运行数据相比较，验证数值算法的有效性和准确性，得到发电系统最佳运行工况。这一研究的开展为其在海洋温差能发电工程中应用奠定理论基础和提供科学依据。

海洋温差能是一种环境友好型、可持续利用的清洁能源,但是较低的海洋温差能发电系统效率阻碍了海洋温差能发电的商业化应用。提出一种新式循环,采用氨水混合工质,以及贫氨溶液回热和中间抽气回热方式,实现对贫氨溶液及乏气的热量二次回收利用。基于能量守恒方程和热力学定律,通过对循环中各设备部分建模分析,构建了新循环的热力模型, 得到了不同温差下混合工质浓度和循环热效率之间的关系，并得到在相同浓度下循环效率与透平进口压力之间的关系。结果表明,新循环氨水混合物浓度对循环热效率有显著的影响。在温、冷海水温度一定时，存在着最佳的工质浓度值使循环热效率最高。当浓度不变时，循环热效率和透平输出功率随第一级透平入口蒸气压力的升高先升高后降低，存在最大值。冷海水温度对循环热效率和净输出功率影响很明显，随冷海水温度升高，循环热效率和净输出功率均线性下降。因此对于固定的温、冷海水工况，存在最佳工质浓度、最佳透平进口压力使得循环热效率最高。改建10kW二次热回收海洋温差能发电系统，系统中采用氟利昂为运行工质，得到了系统平稳运行工况下的发电性能，新循环模型的建立及由此得到的各部分性能分析结果,可为海洋温差能商业化开发提供基础数据理论支撑。