【作者】 徐辉；

【导师】 代彦军；

【作者基本信息】 上海交通大学 ， 动力工程及工程热物理， 2020， 博士

【摘要】 利用海水淡化方法从海水中分离出淡水已成为缓解淡水供应压力的一种有效措施,例如比较适用于大、中规模的多级闪蒸、低温多效以及反渗透等海水淡化技术。然而,很多情况下,实际的用水点比较分散,且用水量较小、所处位置常规能源受限。此时,对高效稳定的小型海水淡化技术有更为迫切的需求。太阳能辅助增湿除湿海水淡化技术,凭借其能耗低、产水率高、结构简单、常压工作等优势,可在小规模淡水供应场合中发挥重要作用。目前该技术面临着增湿和除湿过程相互制约、系统对稳定热源依赖性较强以及热回收效率不高等问题,很大程度上限制了其发展和推广。基于以上背景,本文提出了太阳能热泵辅助以及增强型弱压缩的增湿除湿海水淡化循环方法,使海水淡化产水率指标大幅度提高,主要工作如下:首先,根据太阳能增湿除湿的循环特点,提出了单级以及两级太阳能热泵增湿除湿海水淡化循环,揭示了增强热回收对增湿除湿海水淡化的性能提升机理,明确了增湿过程和除湿过程独立处理时的能量转移方式,解决了常规增湿除湿循环中增湿性能和除湿性能相互制约的难题,提高了系统的热回收能力和产水性能。为解决常规增湿除湿过程中热回收效率不高的难题,创新性的提出了增强型弱压缩增湿除湿太阳能海水淡化循环,降低了对稳定热源的依赖,实现了对热量的“无损”回收,使产水性能指标大幅改善。其次,搭建了太阳能热泵增湿除湿海水淡化实验测试装置。通过典型工况下的单因素敏感性实验测试和热力性能分析,揭示了系统的运行特性。基于两级太阳能热泵增湿除湿海水淡化系统,建立了数学模型,并通过采用双因素敏感性分析的方法完成了对加湿过程和除湿过程的优化分析。研究结果表明,与常规热泵增湿除湿海水淡化系统相比,实现了增湿过程和除湿过程独立处理的太阳能热泵增湿除湿海水淡化系统的最大SEC(Specific electrical consumption)提高了近60%至16.8 kg/k Wh。最后,建成了增强型弱压缩增湿除湿太阳能海水淡化循环实验装置,提出了综合反映系统能效水平的新评价指标:GORe(Gain-output-ratio equivalent)。通过理论分析和实验测试,阐明了新型循环的运行特性与规律,揭示了弱压缩过程变压力工作压差对产水过程的影响机制,发现了喷淋海水温度和系统工作压差是影响产水性能最为关键的两个因素。完成了对系统加湿环节、压差分配调控环节和海水加热温度环节的优化,增强型弱压缩增湿除湿海水淡化系统GOR约为6.49,相比常规增湿除湿海水淡化(GOR=3.5)提高了近85%;系统的GORe可达2.60,为目前国际同类研究最好水平。本文所提出的太阳能热泵增湿除湿以及增强型弱压缩增湿除湿海水淡化循环丰富和发展了太阳能海水淡化技术,显著提高了系统的单位能耗产水率,对促进太阳能驱动增湿除湿海水淡化技术的规模化应用,有着重要的理论参考意义和实用应用价值。更多还原

【Abstract】 Obtaining fresh water from seawater by using desalination technology has become an effective measure to relieve the pressure on fresh water supply,such as multi-stage flash(MSF),low-temperature multi-effect distillation(LT-MED)and reverse osmosis(RO)et al.,which are all suitable for large/medium-size scale desalination.However,in many cases,the actual water consuming point is relatively distributed,and the water consumption is also very small.In this context,there will be a more urgent need for efficient and stable desalination technology in small-scale.Solar assisted humidification dehumidification(HDH)can play an important role in small-scale fresh water supply depending on its outstanding advantages of low energy consumption,high fresh water productivity and simple structure.However,the problems,such as the mutual restriction between humidificaition process and dehumidification process,strong dependence on stable heat sources and low heat recovery efficiency,largely limit its development and application.Based on the above background,a solar assisted heat pump,and a weak moist air compression humidification dehumidification processes were developed,and improved the fresh water productivity significantly.The main research works in this paper are summarized as follows:Firstly,according to the characteristics of solar HDH desalination system,the single-stage and two-stage solar assisted heat pump(SAHP)HDH desalination systems were proposed,respectively.The mechanisms of the performance enhancement on HDH process by improving the heat recovery were extensively investigated.The modes of energy conversion in the independent treatment for humidification process and dehumidification process were also studied in-depth.Consequently,the problems of mutual restriction between humidifier and dehumidifier in conventional HDH process were solved successfully,improving the heat recovery efficiency and system performance.Meanwhile,in order to solve the problem of low-heat recovery caused by the introduction of cooling seawater in conventional HDH process,an enhanced HDH(E-HDH)solar desalination system with weakly compressed moist air was further developed in this paper.This E-HDH cycle successfully reduces the dependence on the stable heat sources,realizes the complete heat recovery process,which makes it possible for significant increasement in fresh water productivity.Secondly,the SAHP HDH desalination experimental setup was then designed and constructed.The operation characteristics of the system was also obtained by the single factor sensitivity test and thermal performance analysis under typical working conditions.The mathematical model was established based on the proposed two-stage SAHP HDH desalination system.The optimization analysis of humidification process and dehumidification process was carried out using the two-factor sensitivity analysis method.The results showed that compared with the conventional HDH desalination system,the maximum SEC(Specific electrical consumption)of the SAHP HDH desalination system which has realized the completely independent treatment between humidification process and dehumidification process increases by nearly 60% to 16.8 kg/k Wh.Finally,an enhanced HDH(E-HDH)solar desalination system with weakly compressed moist air was developed.The experimental setup was designed and constructed.A new performance index GORe(Gained-output-ratio equivalent)was proposed,which can comprehensively evaluate the system performance from the electrical and thermal aspects.Based on the theoretical analysis and experimental tests,the operation characteristics and rules of the novel desalination system were mastered.The influence mechanisms of variable working pressure difference on fresh water productivity in the weak compression process were intensively studied.It was found that the spraying seawater temperature and the working pressure difference are the two most important factors affecting the fresh water productivity.And the optimization analysis of the humidification process,the pressure difference distribution control process and the seawater heated process was achieved.Compared with conventional HDH desalination system(GOR<3.5),the GOR of E-HDH system is about 6.49,which is an increase of nearly 85%.Additionally,the system GORe can also reach 2.60,which is one of the best records in the similar research.The solar assisted heat pump HDH desalination system and the enhanced HDH solar desalination system with weakly compressed moist air proposed in this paper enrich the technologies in the solar assisted HDH desalination system and also significantly improve the system performance,which has important theoretical significance and practical value in the promotion of the scale application for solar desalination technology.更多还原