Solid Desiccant Dehumidification Techniques Inspired from Natural Electroosmosis Phenomena

Electroosmosis has been shown to be an effective means of different applications in various fields such as Micro-Electro-Mechanical systems （MEMS） and biomimetics applications. This paper aims to prove the concept that the electroosmosis phenomena can also be cooperated into larger scale applications in the building service industry like dehumidification or damping proof. The electroosmotic flow inside a porous medium is validated experimentally to further understand the dehumidification mechanism of combined techniques. An experimental test validates that the condensation from the porous medium can be obtained by electroosmotic force generated by external electric field, especially for specific desiccant powders like zeolite and diatomaceous earth. With a range of volts from 5 V to 20 V applying between the testing plates, the maximum flow rate through the cross section in the testing plate achieved during the peak period is 1.35 laL＇min 1. These promising phenomena can act as an alternative way for energy choice in dehumidification industrial field. Further researches on new regeneration methods for solid desiccant dehumidification are required to make the system simple, energy-saving and suitable for small air conditioning units.

Water Desalination Using a Humidification-Dehumidification Technique—A Detailed Review

Solar humidification-dehumidification desalination technology has been reviewed in detail in this paper. This review would also throw light on the scope for further research and recommendations in active distillation system by humidification and dehumidification (HDH). Also in this article, a review has been done on different types of (HDH) systems. Thermal modeling was done for various types of humidification and dehumidification(HDH) distillation system. From the present review, it is found that the humidification-dehumidification desalination process HDH will be a suitable choice for fresh water production when the demand is decentralized. HDH is a low temperature process where total required thermal energy can be obtained from solar energy. Capacity of HDH units is between that produced by conventional methods and solar stills. Moreover, HDH is distinguished by simple operation and maintenance. Also from the present condensed review, it was observed that an increase in evaporator and condenser surface areas significantly improves system productivity. But prior to implementing any techniques in design improvement, it is necessary to optimize the MEH unit by optimizing its component size to understand the effect of feed water and air flow rates. Although a fair amount of simulation studies have been conducted in the past, further design simulation is required to fully understand the complicated effects of air and water flow rates, the optimum size of individual components or modules of the unit and to generate a comprehensive model for the system.

Experimental Investigation of a Vertical Tubular Desalination Unit Using Humidification-Dehumidification Process

A vertical tubular desalination unit with shell and tube structure was built to perform humidification and dehumidification simultaneously on the tube and shell side of the column, respectively. The effects of several operating conditions on the productivity and thermal efficiency of the column were investigated. The results show that both the productivity and thermal efficiency of the column enhance with the elevation of the inlet water temperature. The flow rates of water and carrier gas both have optimal operating ranges, which are 10-30 kg·h^-1 and 4-7kg·h^-1 for the present column, respectively. Meanwhile, the increase of external steam flow rate will promote the productivity of the column but reduce its thermal efficiency.

The Experiment and Simulation of Solid Desiccant Dehumidification for Air-Conditioning System in a Tropical Humid Climate

The aim of this research was to study and design a solid desiccant dehumidification system suitable for tropical climate to reduce the latent load of air-conditioning system and improve the thermal comfort. Different dehumidifiers such as desiccant column and desiccant wheel were investigated. The ANSYS and TRASYS software were used to predict the results of dehumidifiers and the desiccant cooling systems, respectively. The desiccant bed contained approximately 15 kg of silica-gel, with 3 mm average diameter. Results indicated that the pressure drop and the adsorption rate of desiccant column are usually higher than those of the desiccant wheel. The feasible and practical adsorption rate of desiccant wheel was 0.102 kgw/h at air flow rate 1.0 kg/min, regenerated air temperature of 55?C and at a wheel speed of 2.5 rpm. The humidity ratio of conditioning space and cooling load of split-type air conditioner was decreased to 0.002 kgw/kgda (14%) and 0.71 kWth (19.26%), respectively. Consequently, the thermal comfort was improved from 0.5 PMV (10.12% PPD) to 0.3 PMV (7.04% PPD).

Modelling and Experimental Investigation of Humidification- Dehumidification Desalination Using a Carbon-Filled-Plastic Shell-Tube Column

The modelling and experimental investigation of a thermally coupled humidification-dehumidification desalination process using a carbon-filled-polypropylene shell-tube column are presented.A heat/mass transfer model is established to study the correlation among productivity,thermal efficiency,physicochemical parameters (gas/liquid phase temperature,heat/mass transfer coefficient,Reynolds number etc.),and operating conditions(the temperature of feed water,the flow rates of external steam,feed water,and carrier air);at the same time,the effects of operating conditions on the productivity and thermal eficiency of the column are investigated both theoretically and experimentally,which indicate that the optimum flow rates of external steam,feed water,and carrier gas are 0.18,60,and 10kg.h- 1,respectively,and the higher the feed water temperature(≤95℃)is,the greater the productivity and the thermal efficiency will be.Furthermore,performance comparison with the previous study shows that the condensate productivity of this carbon-filled-plastic column is not lower than that of the copper column,which demonstrates the practicability and feasibility of applying such a plastic column to the humidification-dehumidification desalination process.

Membrane-based air dehumidification:A comparative review on membrane contactors,separative membranes and adsorptive membranes

This review compares the different types of membrane processes for air dehumidification.Three main categories of membrane-based dehumidification are identified–membrane contactors using porous membranes with concentrated liquid desiccants,separative membranes using dense membrane morphology with a pressure gradient to drive the separation of moisture from air,and adsorptive membranes using nanofibrous membranes which adsorb and capture moisture to realise dehumidification.Drawing upon the importance of dehumidification and humidity control for urban sustainability and energy efficacy,this review critically analyses and recognizes the three unique categories of membrane-based air dehumidification technologies.Essentially,the discussion is broken into three sections-one for each category-discriminating in terms of the driving force,membrane structure and properties,and its performance indicators.Readers will notice that despite having the same objective to dehumidify air,the polymers used amongst each category differs to suit the operating requirements and optimize dehumidification performance.At the end of each section,a performance table or summary of dehumidifying membranes in its class is provided.The final section concludes with a comparative review of the three categories on membrane-based air dehumidification technologies and draw inspiration from parallel research to rationalise the potential and innovative use of promising materials in membrane fabrication for air dehumidification.

Thermodynamic performance assessment of vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system(VMD-ACERS)

Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system.This work establishes a novel coefficient of performance(COP)model of VMD-ACERS.The main parameters affecting the COP of conventional fan coil unit cooling system(FCUCS)and VMD-ACERS are investigated.The performance of FCUCS and VMD-ACERS are compared,and the energy-saving potential of VMD-ACERS is proved.Results indicate that,for FCUCS,the importance ranking of parameters is basically stable.However,for VMD-ACERS,the importance ranking will be affected by FCU and refrigerant.The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure.On the contrary,superheating,subcooling are relatively less important parameters.For VMD-ACERS,it is not necessary to pursue the membrane with very high selectivity,because the selectivity of membrane would also be a less important parameter when it reaches 500.The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 k Pa.The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC,and can extend the application of THIC air-conditioning system.

Energy conservation research of dehumidification system for main cable anticorrosion of suspension bridge

The necessity of the main cable anticorrosion for suspension bridge is described, and operating principles and composition of main cable dehumidification system are analyzed. An idea using the waste heat of high temperature outlet air of dehumidification system to heat up regeneration air of rotary-type dehumidifier is put forward in this paper. The concrete scheme is to install a heat exchanger on air-out pipeline of roots blower and air-in pipeline of regeneration electric heater of rotary dehumidifier. Air preheated by the heat exchanger enters regeneration electric heater of rotary-type dehumidifier. Energy conservation of main cable dehumidification system for the Yangtze River highway bridge is calculated, and the results show that energy conservation rate can reach 44 %.

A Review Study of Experimental and Theoretical Humidification Dehumidification Solar Desalination Technology

Most of the desalination technologies consume a huge quantity of energy resulting from petroleum products in the form of heat or electrical energy. Solar desalination is a promisingly sustainable freshwater production technology. Solar desalination humidification dehumidification process showed the best approach as it is of the highest overall energy efficiency. In this review paper, a detailed study of the previous work is performed on solar humidification dehumidification desalination techniques experimentally and theoretically. Also in this review, different types of HDH systems were mentioned. The review showed that the humidification dehumidification desalination systems are suitable for decentralized demand. On the other hand, capacity of HDH units is not as large as conventional methods or small as solar stills. Finally, this study threw light on the scope of the parameters which have a considerable influence on increasing the freshwater output of the HDH systems as feed water flow rate, air flow rate, and design of the evaporator, condenser, and packing material. A brief economical study and a comparison of the costs per liter are performed for various humidification dehumidification desalination systems presented in this study.

Simplified Calculation of Flow Resistance of Suspension Bridge Main Cable Dehumidification System

To calculate the flow resistance of a main cable dehumidification system,this study considers the air flow in the main cable as the flow in a porous medium,and adopts the Hagen–Poiseuille equation by using average hydraulic radius and capillary bundle models.A mathematical derivation is combined with an experimental study to obtain a semi-empirical flow resistance formula.Additionally,Fluent software is used to simulate the flow resistance across the main cable relative to the experimental values.Based on the actual measured results for a Yangtze River bridge,this study verifies the semi-empirical formula,and indicates that it can be applied in actual engineering.

Experimental Investigation of Modified Polypropylene Shell-Tube Column Using Humidification-Dehumidification Desalination Process

The polypropylene tubes with surface modification were installed in a baffled shell-tube column to conduct the thermally coupled humidification and dehumidification desalination process. The effects of several operating parameters (feed water temperature, water flow rate, carrier air flow rate, and external steam flow rate) on the productivity and thermal efficiency of this column were investigated experimentally. The results show that the feed water temperature has a positive effect on the productivity and thermal efficiency, while the flow rates of external steam, feed water,and carrier air should be optimized within the ranges of 0.006—0.020 kg·m-2·s-1, 0.005—0.015 kg·m-1·s-1, and 0.7—1.3 kg·m-2·s-1, respectively; the flow rates of feed water and carrier air are greatly controlled by the wetting state of the tubes. In comparison with the previous desalination column installing the coppery tubes, the present column can reach nearly the same production capacity of distilled water, which demonstrates the feasibility of applying such a plastic column to the humidification and dehumidification desalination process.

Improving thermal comfort of high-temperature environment of heading face through dehumidification

In order to improve the thermal environment of high-temperature heading face,moisture content of supply air is reduced by dehumidification, and the relative humidity ofenvironment air of the heading face is also decreased.First, according to the coefficient ofperformance of dehumidifier, the capacity of dehumidification was calculated.Second, inthe engineering example of the heading face, quantitative changes of WBGT (Wet BulbGlobe Temperature) were compared between with dehumidification and without dehumidification.Based on WBGT standards, the thermal comfort of high-temperature environmentof heading face was evaluated between with dehumidification and without handling.Reducingthe relative humidity of airflow through dehumidification, the thermal comfort of ahigh-temperature environment of heading face can improve greatly.Even if dry bulb temperatureof airflow is not decreased, the thermal comfort of heading face environment isalso improved to some extent.

4种用于温室除湿的亲水翅片管蒸发器热湿传递性能分析

温室冬季高效除湿需求已经成为制约中国温室产业高质量发展的技术难题之一。为了提高温室用冷冻除湿系统中亲水翅片管蒸发器的热湿传递性能,该研究建立了低温高湿工况下平翅片、带涡产生器平翅片、波纹翅片、开缝翅片4种亲水翅片管蒸发器空气侧的数值传热模型,采用蒸发器的换热量Q、努塞尔特数Nu、摩擦因子f、单位翅片面积析湿量和强化传热因子JF等评价参数,对比分析了低温高湿工况下4种亲水翅片管蒸发器空气侧热湿传递性能。结果表明,与平翅片相比,带涡产生器平翅片、波纹翅片、开缝翅片空气侧的Nu、Q和f均高于平翅片,且开缝翅片的Q和f在相同条件下均最大;4种翅片的f随入口风速的增大而大幅度减小,而相对湿度对f的影响较小;单位翅片面积析湿量均随入口风速和相对湿度的增大而增大,波纹翅片的除湿能力最优;在入口风速1~4 m/s和相对湿度80%~95%条件下,波纹翅片管蒸发器的JF因子平均值最大,其热性能最优;在冬季寒冷地区低温高湿的温室中,推荐选用波纹亲水翅片管蒸发器对温室内空气进行除湿。该研究可为温室低温高湿环境下除湿系统用亲水翅片管蒸发器的设计与应用提供参考。

一种新型溶液除湿空调系统能耗及应用分析

传统空调系统通常采用温湿度联合处理的方式,该方式存在舒适性差、能源消耗大等问题。针对以上问题,提出一种利用复合直接蒸发冷却制冷水的溶液除湿空调系统,该系统可以有效节省功耗,符合节能减排的发展趋势。在研究过程中,以某办公楼为研究对象,利用TRNSYS仿真软件建立该系统,研究其在制冷季7—9月的能耗,分析其节能性及适用性。结果表明:当空调新风系统使用太阳能热水作为再生热源时,总供热能耗为6.1×10^(5)kW·h,总耗功为8.73×10^(4)kW·h。相比于传统空调系统,节能率达到55.2%,为降低空调系统能耗提供了新思路。

两步法高效含氚净化水空气载带系统研究

针对现有含氚净化水空气载带技术排放效率低、环境适应性差的问题,提出一种基于溴化锂制冷驱动溶液除湿和高效雾化加湿的两步法含氚净化水空气载带系统,搭建了载带量大于2 t/d的试验样机,并在不同工况下开展了载带实验研究。结果显示:试验样机在空气温度3~50℃、空气相对湿度0~90%的环境工况下可安全、高效地排放含氚净化水,试验样机在典型工况、高湿工况、高温工况下,载带量分别为100.8、119.9、96.0 kg/h,与一步法相比,载带量分别提升了298.4%、508.6%、60.0%。这表明,基于两步法的含氚净化水空气载带系统可大幅拓宽含氚净化水安全排放的环境适应范围,且排放效率较高,可为含氚净化水的排放应用提供参考。

舱外航天服除湿装置除湿及再生特性

在舱外航天服环境控制与生命保障系统中,除湿装置能够对介质气体中湿气进行去除,可有效提高CO_(2)分压传感器的测量灵敏度。为适应舱外航天服的使用模式、出舱时间,同时延长除湿装置在舱外航天服中的使用次数,提出了使用舱外航天服氧瓶剩余氧气进行硅胶吹扫再生的方法,为分析除湿装置的除湿特性、再生特性以及使用模式对其性能影响,首先对比了氯化钙、变色硅胶和细孔硅胶等干燥剂的物理特性和除湿性能;其次,采用纯氧吹扫的方式对变色硅胶进行了除湿再生试验研究;最后,对比分析了除湿装置使用模式对其除湿性能的影响特性。试验结果表明:CaCl_(2)颗粒的除湿效果优于变色硅胶,但吸湿后CaCl_(2)干燥剂会出现坍塌短路的现象;在相同试验条件下,变色硅胶的连续除湿时间为32 h,而细孔硅胶的连续除湿时间为23 h;除湿过程经过暂停后,除湿特性发生变化,间断模式的出口绝对湿度随着除湿时间的增加而有所增大,并且高于正常模式下的出口绝对湿度。变色硅胶的物理特性稳定且在满足除湿要求下的除湿时间较长,更适用于该系统中的除湿装置;且变色硅胶经过纯氧吹扫后可循环使用,具备多次除湿功能;间断模式会造成硅胶内部含水量的重新分配,降低除湿装置内硅胶的整体吸湿能力。本研究为舱外航天服环境控制与生命保障系统中除湿装置干燥剂的选择以及再生特性的优化提供了基础数据和理论指导。

基于溶液除湿的新型粮食干燥设备设计及特性分析

我国每年因粮食霉变等原因造成的损失巨大,粮食干燥是实现安全储藏的重要环节之一。另外,随着对粮食品质要求的不断提高,低温通风除湿干燥成为一个主要发展方向。溶液除湿技术相比于冷凝法去湿,具有除湿效果好、温湿度控制精确、节能等优势,应用日益广泛。该设计以“绿色、健康、生态”粮食储藏为理念,开发了基于溶液除湿的新型粮食干燥设备,并通过实验,对机组性能进行了分析。实验证明,不同环境空气工况下,机组出口空气参数达到了设计要求。该系统以电能驱动,并利用冷凝废热驱动溶液循环,系统制冷性能系数(coefficient of refrigeration performance,COPC)可达4.20以上、除湿性能系数(dehumidification coefficient,COPD)不低于3.1,与冷凝法低温干燥机相比可节能50%以上,与烘干机相比可节能20%左右,节能效果显著。从环保、储粮品质的提升、系统节能考虑,该设备具有较大优势,市场应用前景广阔。

预冷除湿/预热再生型溶液除湿空调系统实验研究

提出了一种预冷除湿/预热再生型溶液除湿空调系统,利用热泵的低品位热能预处理溶液,同时使用温度18℃、浓度27%的低温低浓度溶液作为除湿溶液.通过实验研究了除湿侧溶液预冷、再生侧溶液预热后对系统除湿/再生性能的影响,以及系统采用低温低浓度溶液后整体性能的变化规律.结果表明:(1)随着预冷后除湿溶液温度降低,空气含湿量差和除湿效率分别提升16.3%和6.4%;随着溶液流量的提升,空气含湿量差和除湿效率分别上升22%和20%.(2)随着预热后再生温度的升高,再生量由0.132 g/s增加到0.414 g/s,再生热效率由0.196增加到了0.397.预热后再生溶液流量上升时,溶液再生量提升近13%;再生热效率提升6%左右.(3)相较于常温高浓度溶液,系统采用低温低浓度溶液后除湿能力基本不变,除湿前后空气的温降增大,运行成本降低了23%.研究结果为高温高湿地区溶液除湿系统整体性能提升提供了可行的解决方案.