毛细力驱动船舶余热海水淡化的应用基础研究

The main bottleneck in the development of marine desalination industry is the high cost, including the huge investment and high energy consumption. Both of these point to a common fundamental problem, that is, how to obtain the largest distilled water production rate at a given amount of energy. However, due to the limitation of the diffusion transfer mechanism, the existing technical methods are close to the theoretical limit. The progress of micro-nano heat&mass transfer has made it possible to break through the macroscopic transfer limit driven by traditional external forces.The proposed innovative desalination system is an open loop heat pipe by cutting the liquid line and stretching the suction core to the end as the brine withdrawal column compared with the loop heat pipe. The vacuum would be created naturally in the evaporator and condenser without any mechanical energy, where the seawater can be evaporated at a rather low temperature level. The project will focus on how to use low-grade waste heat (<40 °C) for high-efficiency desalination with the proposed capillary-driven seawater desalination technology. This desalination technology breaks through the closed loop operation mode of heat pipes and forms an open working system that interacts with the environment, bringing original and fundamental innovations of seawater desalination technology. Focuses will be given to the fundamental problems, including (1) operational characteristics and hydrodynamic analysis of capillary-driven desalination, (2) mechanism analysis of solute transport and salt crystallization during evaporation in porous media, (3) heat&mass transfer analysis with phase change in micro channel in periodic force field. Relevant results will serve as the important theoretical supports for the development and applications of this new technology, to establish a series of destructive innovation technologies on energy saving and seawater utilization for ship industry.

淡化成本高是当前船舶海水淡化产业发展的瓶颈，包括初投资成本和运行成本。二者指向一个共同的基础问题，即如何以尽可能小的代价，获得尽可能大的物质分离质传递流密度。然而，受扩散传递机理的限制，现有的技术方法已接近理论极限。微纳米传热传质学的进展，为突破传统外力驱动下的宏观传递极限提供了可能。本项目提出以开路热管为核心的海水淡化技术，探索利用船舶运转过程中抛弃掉的那部分低温余热（<40℃）进行高效海水淡化。该技术突破了热管封闭循环运行模式，形成一种与环境交互的开放性工作系统，带来海水淡化技术原创性的、基础性的创新。研究内容涉及毛细力驱动海水淡化的启运特征及水动力学过程、微孔通道内热湿盐高密度输运和结晶动力学问题、周期力场对毛细相变传热传质过程的作用规律等一系列新的基础科学问题和关键技术。相关研究成果将为毛细力驱动海水淡化技术的发展奠定理论基础，有望形成一批船舶行业节能和海水利用的创新性原创成果。

沿海核电企业依赖海水为冷源，约2/3的热量以热水形式直接排放至周边海域中，大量温排水给近海海域带来严重的热冲击，成为制约核电行业发展的瓶颈和冲击海洋环境的痛点问题。. “毛细蒸腾降温”技术，巧妙地移植航空航天领域应用和发展起来的热管技术，实现对相对环境温升仅7-11℃的废热水进行“小温差-高密度”取热。项目突破了“小温差毛细自动驱动海水淡化的热力系统设计”、“降温制淡装备模块化开发和工程运用方案”、“温排水降温制淡及水热同产总体技术研究”等关键技术，开发了一套面向温排水余热利用的工程应用方案。. 1）成功开发出免烧结、低成本、可规模化的毛细材料成型工艺，预先设置的槽道为蒸汽提供了很好的通道。开发的毛细组件尺寸为: 长4.06m、直径19mm、孔隙率33%，置入开路热管测试效果与第一代毛细芯-镍粉烧结（Desalination, 2017）基本一致；. 2）借助Comsol搭建了多孔介质相变过程热湿盐迁移数学模型，发现就余热制淡应用场景下，低导热系数、高孔隙率、小迂曲度的毛细组件具备更有取热性能，如：当毛细芯厚度从5mm减少为3mm时，临界取热密度从0.43W/cm2增加到4.94W/cm2。并建议毛细层厚度<5mm，孔隙率>0.35。. 3）示范运行了一套15kW级毛细驱动余热海水淡化环境测试装置，结果表面可以实现在余热温度10℃~40℃运行稳定，系统最大产水率为12.53kg/(m2·h)，为MED的2.7倍。另外，相同工况下，采用海水和蒸馏水作为运行工质时，相比蒸馏水工质，海水工质的降温能力下降约0.6℃，产水率下降4.3kg/(m2·h)。. 4）在阳江核电温排水隧洞前池旁，建成了一套1/200的温排水降温制淡一体化中试工程，主体设备占地面积100m2，设计温排水处理 900m3/h、降温幅度 2℃、额定热消纳能力为2MW。直接观察到毛细蒸腾在真实核电场景下小温差、高密度取热沸腾现象（气泡生长、破碎），淡水TDS为8~13ppm。