多效管式太阳能苦咸水淡化装置热质传递强化研究

针对管式太阳能蒸馏苦咸水淡化装置产水率低的问题,提出了一种多效管式太阳能苦咸水淡化装置。文章介绍了淡化装置的构造和运行原理,提出了两种强化管式太阳能苦咸水淡化装置内部传热传质效能的方法,测试了装置在定功率和定温度运行条件下蒸发温度、冷凝温度和产水量的变化,研究了对其第二效套筒风冷和水冷条件下,装置淡水产量随运行温度变化的规律。研究结果表明:在输入功率为335 W时,装置的性能系数达到1.37;当加热温度为80℃,对装置套筒进行风冷强化时,淡水产量为1.248 kg/h,比无风冷时的装置淡水产量增加了82.5%;当对装置套筒进行水冷强化时,淡水产量为1.556 kg/h,是无水冷时的装置淡水产量的2.28倍。     

回热对竖管式太阳能海水淡化装置性能的影响

针对管式太阳能海水淡化装置淡水产量较低的问题,提出一种新的具有回热功能的竖管式太阳能海水淡化装置,通过建立装置内部传热传质关系,得到竖管式太阳能海水淡化装置理论淡水产量预测计算方法,分别对单效和两效淡化装置在回热和非回热运行条件下,定温运行工况时的淡水产量、进料海水温度等进行试验研究。结果表明,运行温度为80℃,两效淡化装置在回热运行条件下,淡水产量比非回热运行条件时增加13.32%,单效淡化装置在回热运行条件下,淡水产量比非回热运行条件时增加32.83%,进料海水温度明显升高,装置淡水产量试验测试值与理论计算值趋势一致,吻合度较好。     

低温热源驱动两级负压管式淡化装置性能研究

设计制造一种以太阳能等低温热源驱动,并在负压下运行的两级管式淡化脱盐装置。在44及62℃恒温热源加热条件下,测试装置处于101、60及20 kPa运行压力时的水温及淡水产率,对其性能进行评估。结果表明负压运行可使蒸馏系统产水率提高到常压运行时的3倍以上,同时可提升装置对热能的利用效率。此外,数据表明真空辅助技术应用于小型淡化装置时,电能消耗较低,操作压力为60及20 kPa时,真空泵每小时耗电量分别约为0.00035及0.009 kWh。结合实验数据对2～5级管式蒸馏器的能量利用效率进行估算,当热源温度为70℃时,5级蒸馏器性能系数在60 kPa负压下可达3.79。     

三效竖管降膜蒸发式太阳能苦咸水淡化装置性能研究

针对传统太阳能苦咸水淡化装置产水量小、能量利用效率低等缺陷,文章设计、制作了一种具有回热功能的三效竖管降膜蒸发式太阳能苦咸水淡化装置,利用该装置可以有效地回收水蒸气的冷凝潜热。文章对该装置在不同输入功率下的瞬态、稳态性能进行分析,对不同运行工况下该装置的性能系数进行计算,同时,对该装置在回热和非回热运行工况下的进水温度、蒸发冷凝温差和产水速率等进行对比研究。分析结果表明:当输入功率为335 W时,稳态运行条件下,该装置的产水速率为175 g/10 min,性能系数最大,可达到2;定温运行工况下,采用回热运行模式时,该装置的产水速率大于非回热运行模式,最大可增加40.67%。     

户用多效太阳能苦咸水蒸馏器产水特性研究

工业化太阳能苦咸水淡化装置占地面积大、初始投资高,难以应用于分布式户用苦咸水淡化过程。文章设计了一种户用多效太阳能苦咸水蒸馏器,该蒸馏器具有占地面积小、低品位热能驱动、运行简单等特点,可以实现分布式制备淡水。文章在实际天气条件下,测试了由平板太阳能集热器供能的户用多效太阳能苦咸水蒸馏器的产水速率,研究了该蒸馏器蒸发冷凝温度的变化情况,以及竖直方向冷凝温度梯度的分布情况。研究结果表明,晴天稳态运行时,户用多效太阳能苦咸水蒸馏器内蒸发冷凝温差的最大值约为22℃,沿竖直方向第一效冷凝套筒的冷凝温差约为9.8℃,该蒸馏器的最大产水速率为23.53 g/min,可以满足偏远地区小型户用淡水的制备需求。     

两效竖管式太阳能苦咸水淡化装置性能研究

提出了一种新型两效竖管式太阳能苦咸水淡化装置,介绍了该装置的结构和运行原理,对其性能进行了试验研究和分析,给出了装置在室内电加热试验中各测点温度变化曲线、淡水产量和室外测试结果,计算了装置在室内测试条件下的性能参数GOR。试验结果表明:在室内测试中,该装置在加热功率为305 W的条件下,淡水产量为0.39 kg/h,其性能系数为0.84;在室外试验中,该装置的淡水产量可以达到1.25 kg/h。     

横管式太阳能苦咸水淡化装置产水性能研究

提出一种新型横管式太阳能苦咸水淡化装置,介绍装置的工作原理,通过建立装置内传热传质关系,得到单效及两效横管式太阳能苦咸水淡化装置的淡水产量预测值。用电加热管代替太阳能集热系统,对单效和两效装置在稳态运行时测点温度变化和产水速率进行测试。结果表明:两个装置稳态运行时,蒸汽主要在套管内上部进行凝结,产水速率均随加热温度的升高而增大,两效淡化装置在加热温度为80℃时的淡水产量为0.728 kg/h,是单效装置的2.1倍,实验测试值与理论计算值随温度变化趋势一致,两效淡化装置性能系数可达1.67。     

负压管式蒸馏装置内水蒸气输运过程数值模拟分析

维持蒸馏空腔负压运行可显著提高海水淡化装置的产水性能。为了研究负压条件下,管式蒸馏空腔内水蒸气的输运特性,构建了CFD计算模型,并采用实验数据对CFD计算结果进行验证。此外,文章还根据CFD计算结果得到负压管式蒸馏空腔内湿空气流速、湿空气温度和水蒸气质量分数的分布情况,并对不同负压条件下,管式蒸馏装置的产水性能进行了预测。分析结果表明:管式蒸馏空腔内存在两个对称的环形流动区域,随着该空腔内水温逐渐升高以及操作压力逐渐降低,该空腔内水蒸气的质量分数逐渐增大,湿空气平均流速逐渐增大;与常压下空腔内湿空气的流速相比,当空腔内的操作压力为40 kPa时,湿空气的平均流速约增大了1.5倍;当空腔内的操作压力为40 kPa,水温为70℃时,湿空气的最大流速为0.159 m/s;与常压运行工况相比,当管式蒸馏空腔处于负压运行工况时,管式蒸馏装置的产水速率增大了1.4～6倍,管式蒸馏空腔内温度越低,负压对管式蒸馏装置的产水速率的提升效果越明显。     

锥台式降膜蒸发太阳能苦咸水淡化装置实验研究

针对传统太阳能苦咸水淡化装置运行过程中水体热容量大、传热距离长的问题,文章提出并设计了新型锥台式降膜蒸发太阳能苦咸水淡化装置,通过倾斜冷凝面以拦截浮升水蒸气,从而缩短了苦咸水液膜蒸发传热距离,减少了蒸发冷凝腔内不凝气体量,实现了封闭环形空间内小特征尺寸传热,通过对比分析冷凝面倾斜角度为70°（装置一）和冷凝面倾斜角度为45°（装置二）两装置产水速率和性能系数（GOR）,得到影响该装置性能的关键因素。结果表明,在进水流量为0.30 kg/h时,装置一最大稳态产水速率为0.24 kg/h,比装置二增加了8.33%,其最大蒸发冷凝温差为3.8℃,竖直方向冷凝温度差为1.7℃,性能系数为0.63,该研究为提升小型太阳能苦咸水淡化技术热能利用效率做了有益的探索。     

不凝气体对竖管太阳能海水淡化装置性能的影响

针对太阳能海水淡化装置内不凝气体抑制气水混合物冷凝换热的问题,设计一种竖管太阳能海水淡化装置,通过分别填充氦气和空气作为蒸发冷凝腔工作介质,研究2种不凝气体对装置产水速率、蒸发冷凝温差、热扩散系数以及竖直温度梯度分布等性能的影响机理。结果表明,该淡化装置加热温度为80℃时,填充氦气的装置产水速率为245 g/h,比填充空气的装置产水速率增加15%,填充氦气的装置上测点温度与下测点温度相差约0.1℃,基于试验数据给出不凝气体为氦气运行条件下装置内Nu与Ra的经验关联式,二者呈指数函数关系,决定系数为0.9926。     

Experimental study of the specific energy consumption for brackish water desalination by reverse osmosis

The specific energy consumption (SEC) for brackish water desalination by reverse osmosis membranes was studied experimentally at various operating conditions of feed salt water concentration, temperature, recovery and applied pressure without an energy recovery device. The results were compared with ideal theoretical values. Low‐pressure experiments, corresponding to domestic applications, were performed with a maximum pressure of 8 bar. The energy consumption at normal operating conditions was assessed with a maximum applied pressure of 18 bar. In either case, the recovery was kept between 0.3 and 0.8. Deviations between ideal and experimental values of SEC are pronounced and even more so at the lower pressures and the higher salinity concentrations. The present experimental data for brackish water desalination did not indicate an optimum of the SEC, although for a given feed concentration lower values were obtained at higher pressures, temperatures and recoveries. However, an empirical fit of the present data suggests that an economic optimum for the design and operation may exist at pressures up to 20 bar and recoveries up to 50%. Copyright © 2010 John Wiley & Sons, Ltd.     

Augmentation of solar-assisted humidification-dehumidification water desalination system using heat recovery and thermal energy storage system

In previous investigations, humidification-dehumidification (HDH) solar-assisted desalination systems were designed produce the daily fresh water during sun hours which lead to big sizes and unsteady systems. In the present study, integration of solar-assisted HDH desalination system with heat recovery and thermal energy storage unit is developed to enhance system productivity, reduces auxiliary power consumptions and system size and assure system continuous operation. The mathematical modelling based on energy and mass conservation equations is presented and solved using iterative techniques by C++ and engineering equation solver software. Detailed parametric study of the developed system is conducted for wide ranges of operating conditions and design parameters to study the effects of integrating the HDH system with solar collectors, heat recovery and thermal energy storage units on the system performance. The results revealed that (i) this integration improves system productivity and reduces operating cost, (ii) increasing air to water mass ratio and sea water temperature and decreasing ambient humidity decrease water productivity and gained output ratio (GOR) and increase operating cost parameter (OCP) and (iii) increasing air inlet temperature and sea water flow rates increase GOR and decrease OCP. Comparison with previous systems showed that the proposed system reduces the electric heating power of the system at solar noon by 37% at MR = 0.5 and gives daily fresh water productivity (123.7 kg/h) two times more than previous systems with comparable OCP (0.099 $/kg).     

低温多效蒸发海水淡化系统不同进料方式的热力学分析

应用Aspen Plus软件,建立了平流、顺流、逆流三种进料方式的低温多效蒸发海水淡化工艺流程,并进行了流程模拟,模拟结果与文献[6]进行了对比,验证了所建工艺流程的可靠性和流程模拟的准确性。在加热蒸汽质量流量和热力压缩机引射率相同的情况下,应用等温差分配法对三种进料方式海水淡化系统进行模拟计算,获得了造水比和比传热面积与蒸发器效数、浓缩比、效间温差和进料海水温度之间的关系。研究结果表明:蒸发器效数对系统的热力性能有显著影响,当效数较少时,采用平流进料方式较为合适;增大浓缩比可以提高造水比,且比传热面积变化不大;当浓缩比较大时,可采用顺流进料,以降低结垢风险;增大效间温差,会降低逆流进料方式的造水比,但会增加平流和顺流的造水比;提高进料海水温度可以提升系统热力性能,但进料海水温度受末效二次蒸汽温度的限制。     

一种新型太阳能、风能联合海水淡化装置

淡水资源短缺已成为一个世界性问题,我国也不例外.为了加大淡水供应,一条现实的途径就是充分利用我国丰富的海水资源,以及西北内陆地区的苦咸水(统称海水)进行淡化.提出了一种海水淡化装置,该装置利用温室效应原理和风能致热原理,可充分利用太阳能与风能进行海水淡化.与现有海水淡化装置相比该装置具有利用清洁能源、对环境无污染、适应性强、性价比高等特点.理论计算结果表明,该装置每小时产水量约为普通盘式太阳能海水淡化装置在晴天工作时的2倍.     

Proof-of-concept study of an integrated solar desalination system

This paper describes the performance of a directly heated solar desalination system. The design concept is based on using a direct solar energy collection unit, integrated with flash evaporation and low temperature multi-effect distillation (LT-MED) equipment. Key parameters affecting desalination rate include flashing evaporation pressure, first effect distillation pressure and seawater temperature. The experimental results indicate that at flash evaporation pressure of 0.01 MPa, first effect distillation pressure of 0.004 MPa, and the temperature of solar-heated seawater of 78 °C, the system can reach steady state operation in 17 min. At steady state, desalination rate of 0.204 × 10⁻³ m³/min is obtained. On raising temperature from 70 to 78 °C, net increase in desalination rate of 0.165 × 10⁻³ m³/min is achieved. In contrast, the change of first effect distillation pressure only had minimum effect on desalination rate. Experimental results are in agreement with the theoretical analysis. If temperature continues to increase beyond 78 °C, scaling due to precipitation of CaSO₄ takes place. In this study, the techniques that prevent the system from scaling deposits are discussed.     

柴油机EGR电控冷却系统试验研究

研究了 CA498 柴油机在不同工况下EGR冷却温度对NOx等排放的影响规律,确定了各个工况下EGR的最佳冷却温度,据此设计出一套EGR冷却温度控制装置,可以通过单片机控制伺服电动水泵的转速来调节冷却水的循环量,确保不同工况下的最佳EGR冷却温度.将该电控冷却系统在CA498柴油机上进行了试验.结果表明,与未冷却的EGR系统相比,该EGR电控冷却系统在c0和Hc的排放略有增加的情况下,可以有效地降低NOx的排放、烟度和油耗率.     

多级鼓泡式加湿除湿型太阳能海水淡化装置研究

提出一种多级鼓泡式加湿除湿型海水淡化装置。该装置主要由多曲面太阳能聚光系统、加湿层和除湿层以及相应的泵和管路组成。经聚光器加热后的高温空气在风机驱动下分别进入加湿层和除湿层,热风穿过各级筛板及筛孔,产生气泡,增大了空气与水的接触面积,强化了传热传质过程。在不同天气下对装置进行实验研究,结果表明：在晴朗天气下,装置的太阳能利用率最高可达0.41,淡化装置效率最大可达1.23,最大产水速率为3.66 kg/h,全天产水量为17.08 kg;在非晴朗天气下,装置产水量为12.43 kg。     

Effects of temperature and salt concentration on distilled water production

The paper studies the influence of salt concentration and temperature on the distillation flow rate in a single effect multi-stage system for small water distillation units for low purchasing communities of 50 to 100 people. The distillation process has been evaporation–condensation under variable conditions: temperature of the evaporation and salt concentration. The results have shown there is a dependence of the amount of the distilled water on temperature and salt concentration whose effects are more significant as the temperature rises and salt concentration lowers. The amount of the distilled water has been increased with the use of the multistage system, 103% for sea water, and 56% for brackish water. The ratio of the quantities of distilled water for both cases, sea water and brackish water, has increased from 15.8% for one single stage to 55.7% for the four stages.     

Theoretical study and practical application of the capillary film solar distiller

In the south of Algeria, to supply sufficient fresh water for the population, desalination is necessary because water resources (underground and geothermal) are brackish.This paper presents the theoretical study and the results of experiments carried out with a capillary film multi-effect distiller installed in the south of Algeria (in a village near Touggourt, where the temperature of the groundwater is about 65°C at the source). The name of this device is DIFICAP ( stiller with a lm in illary motion).The aim of our study is to improve the efficiency of this distiller. The research and development of this desalination process is carried out under the following aspects: modelisation of heat and mass transfer, experimentation under direct solar radiation in South Algeria and technical development to aim to optimize the efficiency of this distiller.The theoretical and experimental results show that the efficiency of this distiller increases when the temperature of the brackish water, the intensity of the solar radiation and the number of stages increase.     

吸收式热泵多效蒸发海水淡化热力性能研究

提出了两级吸收式热泵多效蒸发海水淡化工艺流程,并建立了系统的数学模型。计算分析了溴化锂溶液浓度和加热蒸汽温度对系统的造水比、生产单位淡水所需传热面积和吸收式热泵的热力系数的影响。研究结果表明,系统的造水比和吸收式热泵的热力系数随加热蒸汽温度和LiBr浓溶液浓度的降低而增大,生产单位质量淡水所需传热面积随加热蒸汽温度的降低而急剧增加;通过调整溴化锂溶液的浓度,能够实现对不同品质热源的利用;该系统不仅能够保证淡水不被溴化锂污染,而且其造水比明显优于喷射泵多效蒸发系统和多效蒸发系统。