纳米混合工质ORC蒸发过程传热强化影响机制及与热源匹配特性

Organic Rankine cycle (ORC) has a widely application on thermoelectric conversion at low temperature. The temperature glide characteristic of mixture working fluids can reduce effectively the irreversible loss of the process. However, compared to the pure working fluids, the deterioration of heat transfer performance for mixture working fluids cause the increase in investment. The development of new mixture working fluids with higher thermal conductivity and better heat transfer performance is one of the effective ways to solve the problems of low cycle efficiency and high cost. Based on the heat transfer enhancement of nanoparticles, this project intends to add nanoparticles with good heat transfer performance into the binary mixture working fluids to prepare nano-mixed working fluids. The thermophysical properties will be established and the influencing mechanism of heat transfer characteristics by the particle concentration, temperature, and adsorption layer will be discussed. A nano-mixed working fluid with good stability will be prepared, and the migration rule and energy transfer characteristics of the evaporation process under different critical operating parameters will be investigated. The optimization based on the minimization of irreversible loss will be conducted and the matching characteristic between nano-mixture thermophysical properties, heat transfer enhancement for evaporation process, and heat source will be examined. The operation characteristics of the components for different nano-particles and binary mixture working fluids will be tested, and the basic cycle characteristics will be further obtained. The implementation of this project will provide a new idea to reduce the irreversibility of the cycle process and improve the energy efficiency, while it has important academic significance and application value for the development of low grade waste heat power generation technology.

有机朗肯循环技术在中低温热电转换领域具有广泛的应用前景。利用混合工质温度滑移特性可以有效降低过程不可逆损失，然而与纯工质相比，其传热性能降低导致成本高的问题。开发导热系数高和传热性能好的新型混合工质，是解决循环效率低和成本高的有效途径之一。基于纳米颗粒强化能量传递的特性，本项目拟将纳米颗粒添加入二元混合工质制备成纳米混合工质，采用分子动力学模拟方法，建立纳米混合工质热物性计算模型，明确颗粒浓度、温度和吸附层等对其强化传热特性的影响机制；探讨不同关键运行参数下蒸发过程组分迁移规律和能量传递特性，开展不可逆损失最小为原则的优化，阐明工质热物性、蒸发过程传热强化和热源参数的匹配特性；探讨不同纳米颗粒和二元混合工质对循环各部件热力特性的协同关系，获取实验基本运行特性。本项目的实施可为提高循环能量利用效率提供新思路，对发展中低品位余热发电技术给予科学支撑。

有机朗肯循环技术在中低温热电转换领域具有广泛的应用前景。利用混合工质温度滑移特性可以有效降低过程不可逆损失，然而与纯工质相比，其传热性能降低导致成本高的问题。开发导热系数高和传热性能好的新型混合工质，是解决循环效率低和成本高的有效途径之一。为此，本项目基于纳米颗粒强化能量传递的特性，将纳米颗粒添加入二元混合工质制备成纳米混合工质，开展了稳定性测试和流动传热特性实验研究，获得了纳米有机工质透光率、粘性和导热性能的变化规律；实验测试了不同质量流量下R123、ZnO/R123、TiO2/R123和ZnO/TiO2/R123四种工质蒸发过程的流动传热特性，表征了不同纳米颗粒和浓度对纯工质综合传热系数的提升增量；研究了混合工质对超-亚临界双压蒸发有机朗肯循环系统的影响机制；实验测试运行参数对循环性能的影响规律，深入研究润滑油比例、回热器和运行策略对系统性能的影响；构建基于实验数据的动态预测模型，以净输出功率最大和热效率最高为优化目标，开展关键运行参数的协同优化研究，获得热效率和净输出功的相互约束关联式。本项目的实施可为提高循环能量利用效率提供新思路，对发展中低品位余热发电技术给予科学支撑。