太阳能中温聚热可控蒸汽产生及正压多效汽化脱盐研究

In order to avoid the use of complex optical concentrator, a kind of solar thermal-concentrating and steam-generating device is developed to collect solar radiation and heat the work medium to reach medium-temperature. By establishing the heat and mass transfer mathematical model of the device, the temperature and heat flux distributions in the thermal concentrating and transporting structure, and the mechanism of phase-change heat transfer enhancement in the steam generation tube are explored. The temperature, the pressure and the associated steam generating rate in the steam generation tube under different solar irradiance, heat collecting area, heat concentration ratio and heat loss are also achieved. Some key scientific problems relevant to heat and mass transfer in the process of solar medium-temperature photo-thermal conversion and steam generation are clarified. With the optimizing of the mass and heat transport structure to reduce the heat loss, the controllable steam generation under solar medium-temperature thermal-concentration is realized. Then, the multi-effect vaporazation desalination system under positive pressure, with energy supply from solar medium-temperature thermal-concentrating device, is designed and built. It resolves the issue of high power consumption and high desalination cost in the system under negative pressure. The ways of cascade heating to reduce heat loss, optimization of the 'effect' working parameters and re-use of the steam latent heat between 'effect', are proposed to achieve effective energy utilization in the system. With the comprehensive thermal management and energy flux organization, the positive-pressure multi-effect vaporazation desalination system with energy supply by solar medium-temperature thermal-concentration in stable operation will be reached.

为避免使用复杂的光学聚光系统，研究一种太阳能聚热集热蒸汽产生装置汇聚太阳辐射加热工质达到中温温位。通过建立非聚光太阳能中温聚热集热汽化传热传质数理模型，探索聚热集热结构中温度与能流分布，及蒸汽产生管内汽化相变传热强化机理，获得不同太阳辐射强度、聚热面积、聚热比与散热损失下蒸汽发生管内的温度和压力，及其与水蒸气产生速率的关联关系，阐明太阳能中温光热转换及水汽化相变换热过程中传热传质关键科学问题。优化装置质能输运结构，减少散热损失，实现中温下可控水蒸汽产生。采用太阳能中温聚热供能方式，构建正压工作的多效汽化含盐水淡化系统，解决负压运行多效蒸发系统功耗大、造水成本高的问题。采用梯级加热以减小散热损失、优化各“效”工作参数及水蒸汽潜热“效”间复用等方法，实现能量在“效”间的协同利用及系统中质能流的耦合与匹配。通过有效的热管理及能流组织，实现太阳能聚热中温供能的含盐水淡化系统稳定运行。

项目围绕太阳能聚能可控蒸汽产生及含盐水汽化淡化中的集能、质能输运及高效用能开展研究。建立了聚热集能汽化装置和复合抛物面聚光集热汽化装置的相关数学模型，设计、优化并搭建了有预热的太阳能含盐水淡化系统进行实验研究。. 根据几何光学和太阳几何学原理，建立了不同地理位置、安装倾角、方位角下聚热集热器采光量的估算方法。构建了太阳能聚热集热装置传热传质模型，获得了不同温度及聚热集热面积下的散热损失。讨论了太阳辐射强度、聚热集热面积、聚热比、聚热传热结构等与聚热温度的关联关系，实验获得了装置的水蒸汽输出特性。通过增设反射镜，提高聚热集能装置接收的太阳辐射能量，从而提高装置工作温度，增加蒸汽产量。增设反射镜的聚热集能装置全天平均产蒸汽速率为27.79 mL/mim，全天累计产蒸汽10-13 kg。. 为强化蒸汽产生铜管内水的相变换热及汽化，研究了铜基表面的改性。采用一步电沉积法在铜基阴/阳极表面同时制备超疏水膜层。阳极铜电极表面覆盖有树枝状微/纳米分级结构的Cu[CH3(CH2)16COO]2，阴极铜电极表面出现具有立方晶体状微/纳米分级结构的Cu2O—硬脂酸。用SEM、FT-IR、XPS、接触角测量仪表征了膜层表面形貌、化学组成和润湿性，并讨论了膜层形成机理。当沉积电压为4V，沉积时间为30 min时，阳极表面静态接触角最大达到151.3°，阴极表面的静态接触角最大达到154°。. 设计并搭建了有预热的太阳能含盐水淡化实验系统。由于在低温位阶段采用太阳能热水系统加热和水蒸汽潜热回收复用，CPC集热器和聚热集能装置获得的较高温位能量更多用于水的相变汽化。系统实现较高能量综合利用效率，及系统中质能流的优化配置，可为进一步规模化经济性的太阳能含盐水淡化提供基础。