带肋片多效管式海水淡化装置的实验研究

设计一种带肋片多效管式海水淡化装置并利用模拟热源对装置进行实验研究。实验中对系统稳态产水性能进行测试,给出系统在不同运行温度、压力下的产水速率和性能系数。实验结果表明:装置小时产水量随运行温度升高而增大,80℃时小时产水量为0.59 kg/h;对装置进行抽真空后装置的小时产水量增加明显,在运行温度为70℃压力为0.31 k Pa时,小时产水量最大为1.19 kg/h;装置的性能系数最高达1.5,定功率运行10 h,产水量最高为8.58 kg。     

多效增湿除湿太阳能海水淡化装置的性能试验

文章提出了一种具有规模灵活、操作简单、维护运行成本低廉、易于和可再生能源结合等优点的新型多效增湿除湿太阳能海水淡化装置;介绍了装置的结构和运行原理,进行了海水运行温度、进水流量等影响产水性能的参数的实验研究。研究结果表明,装置产水量随进水流量和运行温度增加而增大,当进水流量为906 kg/h时,装置产水量达到58.14 kg/h。该多效增湿除湿海水淡化系统具有较大的性能提升空间和广阔的应用前景。     

叠置式太阳能加湿除湿海水淡化系统的稳态性能研究

介绍一种基于空气加湿除湿技术的太阳能海水淡化装置,装置中除湿腔叠置在加湿腔的上部,以此缩小装置的占地面积并利用热湿空气自然上升的浮力,形成一种新结构。详细说明装置的结构和运行原理,并研究控制海水运行温度、流量、循环空气流率等参数对装置产水性能的影响。实验结果表明,装置产水量随进水流量和运行温度增加而增加,当温度为90℃时,进水流量为420 kg/h,装置的最大产水量达到10.38 kg/h,装置性能系数GOR最大为1.33。系统在类似条件下的理论产水率达到约15.6 kg/h,性能系数达到1.90。对生化小球和加湿帘2种填料及不同填料厚度的产水性能进行测试,结果表明填料的选择,要结合装置体积和传质效率来综合考虑。     

竖壁自储水式太阳能蒸馏装置运行特性分析

设计一台三效回热竖壁自储水式太阳能海水淡化装置。对其在实际天气下的运行参数进行测试,得到装置全天温度、产水率及累计产水量变化曲线,实验测试中装置性能系数为1.35。构建装置的传热传质计算模型,通过与实验数据对比验证模型的准确性并进一步对装置特性进行研究。利用所构建模型分析系统的能量流动情况,结果发现无效热能散失过大是装置在实际天气运行时性能系数偏低的主要原因。最后,对该类太阳能海水淡化系统经优化后的实地运行性能进行预测和评估,为工程应用提供指导。     

一种回收蒸发潜热太阳能蒸馏装置的研究

对一种回收蒸发潜热的太阳能蒸馏装置进行了研究.结果表明,太阳辐照度、冷凝器冷却海水流量和蒸发器入口海水温度是影响系统性能的主要因素,当冷凝器冷却海水流量为45 l/h,蒸发器入口海水温度为75℃时,系统具有较大的淡水产量和合适的系统GOR值.     

一种回收蒸发潜热太阳能蒸馏装置的研究

对一种回收蒸发潜热的太阳能蒸馏装置进行了研究。结果表明，太阳辐照度、冷凝器冷却海水流量和蒸发器入口海水温度是影响系统性能的主要因素，当冷凝器冷却海水流量为４５ｌ／ｈ，蒸发器入口海水温度为７５℃时，系统具有较大的淡水产量和合适的系统ＧＯＲ值。     

一种新型家用太阳能海水淡化装置

设计了一种具有折皱底面的多级迭盘式家用太阳能海水淡化装置。该装置由热管式真空集热管和多级海水淡化器两部分组成。在实际天气条件下,对该装置性能进行了测试,给出了该装置每0.5 h的产水量、累计产水量以及各级水盘的水温随运行时间的变化曲线。实验结果表明,在测试当天累计太阳辐射量22.46 MJ/（m^2.d）条件下,该装置产水量可达9.34 kg/（m^2.d）,单位太阳辐射能产水量为1.50 kg/kWh;该装置的性能系数达到0.956,是传统单级盘式太阳能蒸馏器性能系数的2.7倍。该装置使用简便,运行可靠,维护费用低,在淡水缺乏的岛屿或偏远的咸水湖地区,是一种较为理想的家用太阳能海水淡化装置。     

海岛小型太阳能海水淡化装置及产水量影响研究

以所研制的可用于海岛景观生态修复的小型太阳能海水淡化装置为研究对象,通过实地测量的方法,对装置性能及产水量影响因素进行了研究。结果表明:装置室内海水温度与透光面板内壁面温度之差ΔT是海水蒸发产水主要影响因素。在任何装置室内温度下,海水表面蒸发都可进行,但只有当ΔT为正值的时间段内,才可有效的产生淡水。装置内海水深度对产水效率具有影响,在本研究中,水深较浅时,产水量差异不大,但水深较大时,随着水深的增加,产水量增加。装置覆盖面板材质对产水量有一定影响,试验研究表明,相比普通玻璃面板,有机玻璃盖板有利于提高产水量。装置内增加黑色海绵等吸热物质,将起到延缓池内水温下降的效果,有利于显著提高产水量。     

LNG冷能驱动的氨水吸收式制冷系统的性能研究

本文提出了一种新型的以冷制冷的氨水吸收式制冷系统。系统利用LNG气化释放的冷能作为冷源,通过少量的高品位冷能的利用来制取多量的低品位冷能,制冷循环采用氨水吸收式制冷系统。通过对系统的热力分析表明:当制冷温度(蒸发器蒸发温度)为0℃,蒸馏率为0.185,LNG冷能输入系统的温度为-60℃时,系统的性能系数为1.74。在此条件下对系统进行火用分析,发现吸收器的火用损失最大,其火用损系数约为24%,系统总的火用效率为41%。对系统进行特性规律分析,发现当蒸发器的蒸发温度不变时,发生器氨气蒸馏率的增加会使得发生器操作压力下降,LNG冷却温度下降,但同时系统的性能系数会增加。蒸馏温度越高,系统的性能越好,当制冷温度为10℃时,系统的性能系数可以达到1.8以上。     

具有防融霜装置的蒸发器结霜特性及性能仿真研究

以具有防融霜装置的蒸发器为研究对象,建立基于理想最小防融霜补热量和结霜量无量纲关联式的空气源热泵动态模型,并依据实验数据验证其精确性,通过数值模拟分析不同环境参数对具有防融霜装置的蒸发器性能的影响。结果表明：后置式与跨越式系统蒸发器换热系数要高于前置式与传统电辅热系统,霜层厚度更小,分布更均匀;当相对湿度一定时,蒸发器换热系数随温度升高而增大;当空气温度不变时,换热系数随相对湿度的下降而减小,霜层更均匀;温度对蒸发器换热系数的影响比相对湿度更大。     

Humidification-dehumidification water desalination system integrated with multiple evaporators/condensers heat pump unit

A study of the performance enhancement of a humidification-dehumidification (HDH) system integrated with multiple evaporators/condensers heat pump (HP) and heat recovery units is presented. The HP unit is intended to deliver necessary heating for humidifier and heating/cooling for dehumidifier in a new strategy. The proposed integrated system is capable to produce fresh water from the HDH system and HP unit. Four different configurations of the system formed by excluding/adding condensers and evaporators were investigated; mode-A (seawater precooling and reheating), mode-B (seawater reheating), mode-C (seawater precooling and humid air reheating), and mode-D (humid air reheating). Fresh water productivity, fresh water ratio, system water recovery, gain output ratio, specific work consumption, and fresh water production cost were used as performance measuring parameters of the system. The influences of operating parameters on the system performance were analytically studied and experimentally validated for different system configurations. The results indicate the enhancement of the systems' performance with increasing ambient air temperature and humidity, seawater and air flow rates, and with decreasing seawater temperature. The system configuration of mode-B shows the best performance with fresh water production of 61.94 kg/h and gain output ratio of 4.97 which are higher than those of the other configurations by 13%, 55%, 85% and 11%, 48%, and 75%, respectively. Comparisons of the proposed configurations with the other HDH desalination systems available in the literature were presented and better performance of the proposed systems was noticed.     

Thermodynamic analysis of a new double-pressure condensation power generation system recovering LNG cold energy for hydrogen production

Cold energy during the LNG regasification process is usually applied for power generation, but the electricity demand varies with the time. Therefore, a thought that transforming electrical energy into hydrogen energy by PEM electrolyzer is put forward to adjust the adaptability of power output to electricity demand. This paper proposes a new double-pressure condensation Rankine cycle integrated with PEM electrolyzer for hydrogen production. In this system, seawater is used as the heat source, and binary mixed working fluids are applied. Meanwhile, multi-stream heat exchanger is introduced to improve the irreversibility of heat transfer between LNG and working fluid. The key system parameters, including seawater temperature, the first-stage condensation temperature, the second-stage condensation temperature, and outlet temperature of LNG, are studied to clarify their effects on net power generation, hydrogen production rate and energy efficiency. Furthermore, the hydrogen production rate is as the objective function, these parameters are optimized by genetic algorithm. Results show that seawater temperature has positive impact on the net power output and hydrogen production rate. The first-stage condensation temperature, the second-stage condensation temperature, and outlet temperature of LNG have diverse effects on the system performance. Under the optimal working conditions, when the LNG regasification pressure are 600, 2500, 3000 and 7000 kPa, the increasing rate for optimized net power output, hydrogen production rate and energy efficiency are more than 11.68%, 11.67% and 8.88%, respectively. The cost of hydrogen production with the proposed system varies from 1.93 $/kg H2 to 2.88 $/kg H2 when LNG regasification pressure changes from 600 kPa to 7000 kPa.     

Numerical Investigation of Two-Phase Flow in Natural Gas Ejector

Increasing production and recovery from the mature oil and gas fields often requires a boosting system when the gas pressure is lower than that demanded by the transportation or process system. The supersonic ejector, considered to be a cost-effective way to boost the production of a low-pressure gas well, was introduced into the industrial field. However, the exploitation of natural gas often accompanies with water. The computational fluid dynamics (CFD) technique was employed to investigate the two-phase effect (water droplets) on the performance of natural gas ejector for the motive pressure ranging from 11.0 MPa to 13.0 MPa, induced pressure from 3.0 MPa to 5.0 MPa, and backpressure from 5.1 MPa to 5.6 MPa, while the injected water flow rate was less than 0.03 kg s^?1. The numerical results show that the entrainment ratio of the two-phase operation was higher than that of the single-phase operation with the variation of backpressure. Meanwhile, the entrainment ratio increased with the increase of injected water flow rate into the primary flow. When the water was injected into the secondary flow, the entrainment ratio decreased as the injected water flow rate increased, but the critical backpressure remained unchanged.     

A novel vacuum wastewater treatment plant integrated with a solar absorption system

In this investigation, a novel use of the solar absorption refrigeration systems was introduced by using it to enhance the operation of vacuum wastewater treatment plant. Wastewater treatment systems require a source of heat for evaporation, a cooling section for condensation and a mean of evacuation to facilitate evaporation. The solar absorption system can take over the first two tasks. Among the commercially available vacuum evaporators, one was selected and modified by replacing the conventional heat pump with the solar absorption system. Two validated mathematical models available in the literature, one for solar absorption subsystem and one for vacuum evaporation subsystem, were integrated together to perform the analysis. The impacts of solar absorption subsystem parameters along with vacuum evaporator subsystem parameters on the overall performance were investigated using the developed program. System performance was evaluated in terms of evaporation rate and condensate rate production. It was found that the degree of superheat had the greatest impact on the rate of evaporation. At low levels of supply temperature to the vacuum chamber, using only heat provided by the absorption system, the evaporation rate exceeded 60 kg/h. If the hot water was further heated by passing through the solar collector storage tank, the evaporation rate exceeded 200 kg/h.     

电厂水环式真空泵冷却系统的问题及其对机组出力的影响

通过对电厂中常用的水环式真空泵冷却系统运行实际情况的分析研究，指出其运行中存在但常被忽视的问题：由于真空泵冷却水温升高而导致的抽气能力严重降低，使机组背压升高，出力下降。文章提出凝汽器的压力实际受到两个瓶颈的限制：一是循环水的温度，二是真空泵的极限工作压力，而这一点常没有被足够的注意，导致凝汽器压力明显升高。由于凝汽器压力对机组运行的出力和经济性影响很大，文章提出了对真空泵冷却系统改进的建议，即尽量降低真空泵冷却水入口温度，在平时运行时应密切注意真空泵热交换器的运行状况。图3     

Performance of anodic recirculation by a variable flow ejector for a solid oxide fuel cell system under partial loads

An anode gas recycle (AGR) system driven by a variable flow rate ejector was developed for use in small-scale solid oxide fuel cell (SOFC) systems. The partial load conditions were simulated through recycling power generation experiments to clarify the fundamental characteristics of the variable flow ejector by using actual 1 kW-class SOFC equipment at the steady state. We achieved power generation in a range of recirculation ratios under partial load conditions of 62.5%–80% by controlling the recirculation characteristics with the developed ejector by using a needle. Results showed that the recirculation ratio can be controlled in the range of 0.595–0.694 by adjusting the driving energy with the ejector even at a partial load where the fuel gas flow rate of the ejector changes. Furthermore, the effect of the recirculation ratio on SOFC output was discussed based on the results of gas analyses and temperature measurements. As the recirculation ratio increased, the fuel concentration at the SOFC inlet decreased and the water vapor concentration increased. However, the effect of the recirculation ratio on the stack temperature and output power was proposed to be small. In addition, it was confirmed that the operation was performed under safe conditions where no carbon deposition occurred by circulating the steam generated inside the SOFC without an external water supply. Ejector characteristics during power generation experiments were lower than those at room temperature, which indicates that an ejector upstream pressure of approximately 20–170 kPa gauge pressure was required. Variations in the fluid properties of the driver gas in the ejector motive nozzle heated by the hot suction gas were found to degrade the performance of the ejector installed in the SOFC system, as compared with the results of simulation experiments at room temperature. Nevertheless, the recirculation ratio range required for operation could be satisfied by adjusting the flow velocity of the driving gas through needle control.     

Parametric study of heat/mass transfer performance of seawater–air two-phase counterflow in packing in seawater cooling towers

A large amount of waste heat generated in industrial production needs to be discharged by circulating cooling water systems. To save freshwater resources, freshwater cooling towers have been widely replaced by seawater cooling towers in coastal areas, but research on the thermal performance of seawater cooling towers is still relatively less. In this study, a detailed calculation model based on the heat/mass transfer process of seawater–air two-phase counterflow was established, and the reliability of the proposed model was verified. The computer program developed under the VC++ framework was used for the numerical solution of the model. The effects of five inlet parameters on the cooling efficiency and heat dissipation were studied. The simulation results showed that with the increase of salinity, the cooling performance was reduced. When the salinity increased by 10 g/kg, the outlet water temperature rose by about 0.13°C. The wet-bulb temperature increased by 1°C and the cooling efficiency increased by about 0.77%, while total heat dissipation was reduced by about 36.37 kW. When the air–water ratio increased, the cooling performance was improved, but the maximum cooling efficiency was affected by heat load. The change of dry-bulb temperature had little effect on the cooling performance. With the increase of water temperature, the cooling efficiency and heat dissipation increased. The calculation model and simulation results can provide practical guidance for the operation of seawater cooling towers.     

A seawater freeze desalination prototype system utilizing LNG cold energy

The freeze desalination method is not being used widely, since it needs refrigeration system that consumes much electricity. On the other hand, liquefied natural gas (LNG) releases a lot of cold energy during its vaporization process. Thus, combining the two processes of LNG vaporization and seawater freezing may produce freshwater in an economical and environment-friendly way. In this paper, a seawater freeze desalination prototype system is designed and manufactured. In this system, R410A is chosen as the secondary refrigerant to transfer cold energy from LNG to seawater, and a flake ice-maker is adopted to produce ice. Experiments are conducted with the prototype system, with liquid nitrogen as the cold source. The results show that the system is able to reach the designed fresh water capacity of 150 L h^?1, with the converted cold energy efficiency above 2 kg (fresh water)·kg (LNG)^?1. The salt removal rate of the system is about 50%, indicating that one cycle of the freeze desalination is not enough for producing drinking water. The influences of some key factors, such as refrigerant evaporating temperature, number of spraying nozzles at the water distributing disk, and seawater flowrate, on the salinity of the formed ice are also tested.     

Control and experimental characterization of a methanol reformer for a 350 W high temperature polymer electrolyte membrane fuel cell system

This work presents a control strategy for controlling the methanol reformer temperature of a 350 W high temperature polymer electrolyte membrane fuel cell system, by using a cascade control structure for reliable system operation. The primary states affecting the methanol catalyst bed temperature is the water and methanol mixture fuel flow and the burner fuel/air ratio and combined flow. An experimental setup is presented capable of testing the methanol reformer used in the Serenergy H3 350 Mobile Battery Charger; a high temperature polymer electrolyte membrane (HTPEM) fuel cell system. The experimental system consists of a fuel evaporator utilizing the high temperature waste gas from the cathode air cooled 45 cell HTPEM fuel cell stack. The fuel cells used are BASF P1000 MEAs which use phosphoric acid doped polybenzimidazole membranes. The resulting reformate gas output of the reformer system is shown at different reformer temperatures and fuel flows, using the implemented reformer control strategy. The gas quality of the output reformate gas is of HTPEM grade quality, and sufficient for supporting efficient and reliable HTPEM fuel cell operation with CO concentrations of around 1% at the nominal reformer operating temperatures. As expected increasing temperatures also increase the dry gas CO content of the reformate gas and decreases the methanol slip. The hydrogen content of the gas was measured at around 73% with 25% CO₂.     

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).