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.

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.

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).

Design of ionic liquids as liquid desiccant for an air conditioning system

Suitable control of the humidity can contribute to electric energy savings. However, the present dehumidification system has many weak points. The liquid desiccant air-conditioning system has recently gained growing interest from the stand point of reducing energy consumption during dehumidification. In order to find the appropriate ionic liquids(ILs) as a desiccant for the liquid desiccant air-conditioner system, we conducted a systematic evaluation of the humidification capability of 16 types of ILs. Among the tested ILs, tributyl(methyl)phosphonium dimethyl phosphate([P4441][DMPO_4]) exhibited the best dehumidification capacity and had a less corrosive effect on four types of metals as possible piping materials. It should be noted that this [P_(4441)][DMPO_4] has a very stable nature and produced no odor while conducting the experiment and storing for over 1 year at room temperature under ambient conditions. Furthermore, it was revealed that a 77%(w/w) aqueous solution of [P4441][DMPO_4] worked as an efficient desiccant liquid for the liquid desiccant air-conditioner system.

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.

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.

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.

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.

Development of Temperature-Humidity Independent Control Air-Conditioning Unit for Residential Buildings

Cooling panels are increasingly used in domestic residential buildings.To provide medium temperature cold water for the cooling panel,and dehumidify the indoor air simultaneously,a new kind of temperature-humidity independent control air-conditioning unit was developed for single residential house by utilizing multi-variable technology.First,the supply air temperature was studied to determine the proper supply air flow rate for the humidity control.Then,the energy consumption of different temperature-humidity independent control systems was studied.The analysis indicates that unity evaporating temperature can be used to handle the moisture load and sensible heat load in two evaporators.So the unit scheme was put forward.Two evaporators were used to produce medium temperature water and dry air separately,and electric expansion valves were used to control the refrigerant distribution between the two evaporators.Then,experimental work was carried out to investigate the influence of compressor frequency,refrigerant distribution on the dehumidification capacity,energy efficiency and refrigeration capacity.In the end,the paper concludes that both compressor frequency and refrigerant distribution can control the dehumidification capacity,but the former influences the EER more than the latter,while the latter influences the refrigeration capacity more than the former.We can find a proper running point at certain sensible and latent cooling load by adjusting both compressor frequency and electric expansion valve.The energy consumption of this kind of unit was estimated and compared with present room air conditioners,which shows that it can save about 41% cooling energy consumption.

AN EXTENSION OF THE METHOD FOR PREDICTING PERMEABILITY THROUGH POLYMER MEMBRANES FROM SIMPLE GASES TO WATER VAPOR

It is found that there is a linear relationship between log P-w, and the parameter term V-f/0.5 E(coh) [1+(delta(w) - delta(p))(2)/delta(p)(2), from the water permeability (P-w) data of 21 polymers covering 4 orders of magnitude. This correlation may be useful in choosing membrane materials for dehumidification of gases.

Sensitivity analysis of the DehumReq model to evaluate the impact of predominant factors on dehumidification requirement of greenhouses in cold regions

In this study,the sensitivity of a novel dehumidification requirement model(DehumReq)is analyzed to evaluate the effect of the predominant factors on the dehumidification needs of the greenhouses.The hourly dehumidification demand and sensitivity coefficient(SC)are estimated for three different seasons:warm(July),mild(May),and cold(November),by using the local sensitivity analysis method.Based on SC values,the solar radiation,air exchange,leaf area index(LAI),and indoor setpoints(temperature,relative humidity(RH),and water vapor partial pressure(WVPP))have significant impact on the dehumidifi-cation needs,and the impact varies from season to season.Most parameters have a higher SC in summer,whereas solar radiation and LAI have a higher SC in mild season.The dehumidification load increases 4 times of its base value with increasing solar radiation by 200 W/m^(2),and the highest LAI(10)caused 5 times increment of the load.The changing of WVPP from its base value(1.5 kPa)to maximum(2.9 kPa)reduces the load 70%in summer.Air exchange was found to be the most crucial parameter because it is the main dehumidification approach that has a large range and is easily adjustable for any greenhouses.Sufficient air exchange by ventilation or infiltration will reduce the dehumidification load to zero in May and November and minimizes it to only nighttime load in July.For the other parameters,higher ambient air RH and indoor air speed will result in higher the dehumidification load;whereas higher inner surface condensation will result in lower dehumidifi-cation load.The result of this study will assist in the selection of the most efficient moisture control strategies and techniques for greenhouse humidity control.

Recent progress in liquid desiccant dehumidification and air-conditioning:A review

This paper presents a literature review on the recent research progress in liquid desiccant dehumidification and air conditioning systems.The physical features of various liquid desiccant materials and their dehumidification performances have been summarized.With the aim to improve the dehumidification characteristics,mixed sol-vents desiccants have become research hot topics recently.Various types of dehumidifiers and their integration with liquid desiccant dehumidification system have been reviewed.The combination of liquid desiccant dehumid-ification system with solar collector,vapour compression system,heat pump system,CHP system,etc.have been grouped and compared.It is shown that the majority of the recent research work for liquid desiccant dehumid-ification systems has concentrated on numerical simulations,a considerable amount of works are still required for the practical investigations of innovative material(mixed solvents)and hybrid systems.

Design of quaternary ammonium type-ionic liquids as desiccants for an air-conditioning system

The liquid desiccant air-conditioning system allows reducing energy consumption compared to the conventional compressor-type air conditioners.In order to develop desiccant materials for air conditioners,we have investigated the dehumidification capability of quaternary ammonium Ionic Liquids(ILs)and the equilibrium water vapor pressure of aqueous solutions of these ammonium salts.Among the seven tested types of ILs,2-hydroxyN,N,N-trimethylethan-1-aminium dimethylphosphate([Ch][DMPO4])displayed the best dehumidification capability and the lowest equilibrium water vapor pressure.Furthermore,the 80%aqueous solution of[Ch][DMPO4]exhibited a less corrosive effect on four types of metals,i.e.,steel(hot dip zinc-aluminum alloy plated steel),copper(C1100P),aluminum(A5052),and stainless steel(SUS:SUS304).It should be noted that this[Ch][DMPO4]is not only non-toxic but also exhibits a stable nature;the aqueous solution produced no odor after storing for over 1 year under ambient conditions.

Desiccant Performance Evaluation of Desiccant-Coated Heat Exchanger-Based Heat Pump by Equilibrium Model

By combining the advantages of desiccant dehumidification and vapor compression refrigeration,the desiccant-coated heat exchanger-based heat pump(DCHE HP)is regarded as a promising alternative to the traditional vapor-compression air conditioning system(VCAC).Selecting proper desiccants from a large number of candidates is of great importance to improve the performance of DCHE HP.However,this task is challenging using current experimental or modelling strategies.In this work,we developed an equilibrium model to evaluate the power consumption of 39 DCHE HPs coated with different desiccants under various operating conditions.Eventually,five desiccants with low power consumption were selected.It was also demonstrated that under given operating conditions,the DCHE HP based on the five selected desiccants can save 21.3%–32.9%power compared with the VCAC.The power consumption of the DCHE HP is largely dependent on the heat of adsorption,the cyclical water uptakes and the remained moisture contents of the coating desiccants.It was further revealed that the moderate heat of adsorption,the larger cyclical water uptake and the lower remained moisture content are preferable for reducing the system energy demand.This work reported a quick evaluation of 39 desiccants for DCHE HP by an equilibrium model,which may also offer insights into the choosing and designing of desiccants for DCHE HP.

Experimental Study of the Removal of Fine Particulate Matter and Moisture from Flue Gas

Liquid desiccant systems are promising methods to recover water and waste heat simultaneously from flue gas.Prior research found that the reduction of particulate matter could occur during the absorption processes.In the present paper,experiments were carried out to explore the effect of removing fine particulate matter(PM_(2.5))in a liquid desiccant dehumidifier.Aqueous calcium chloride(CaCl_(2))was used as the desiccant in the experiments.The discrepancies in mass and energy conservation were within±10%and±15%,respectively,which showed the good reliability of the experimental results.Additionally,23.5%–46.0%of the PM_(2.5)and 23.9%–45.1%of the moisture in the flue gas were removed.By comparing the desiccant solution and water,it was found that they could minimally remove PM_(2.5)through washing the flue gas.Regardless of whether the flue gas was dehumidified by water or the solution,the removal fractions of PM_(2.5)of these two methods could be very close if they achieve the same fraction of moisture removal.From the results of a parameter analysis,it was found that the removal fraction of PM_(2.5)was nearly proportional to the removal fraction of moisture within the experimental range.

Wet‑Spinning Knittable Hygroscopic Organogel Fibers Toward Moisture‑Capture‑Enabled Multifunctional Devices

Atmospheric moisture exploitation is emerging as a promising alternative to relieve the shortage of freshwater and energy.Efforts to exploit hygroscopic materials featuring flexibility,programmability,and accessibility are crucial to portable and adaptable devices.However,current two-dimensional(2D)or three-dimensional(3D)-based hygroscopic materials are dif-ficult to adapt to diverse irregular surfaces and meet breathability,which severely hinders their wide applications in wearable and programmable devices.Herein,hygroscopic organogel fibers(HOGFs)were designed via a wet-spinning strategy.The achieved fibers were composed of the hydrophilic polymeric network,hygroscopic solvent,and photothermal/antibacterial Ag nanoparticles(AgNPs),enabling hygroscopic capacity,photothermal conversion,and antibacterial.Owing to the good knittable feature,the HOGFs can be readily woven to adjusted 2D textiles to function as an efficient self-sustained solar evaporator of 4-layer woven HOGF device with a saturated moisture capacity of 1.63 kg m^(-2) and water-releasing rate of 1.46 kg m^(-2) h^(-1).Furthermore,the 2D textile can be applied as a wearable dehumidification device to efficiently remove the evaporative moisture from human skin to maintain a comfortable environment.It can reduce the humidity from 90 to 33.4%within 12.5 min.In addition,the introduction of AgNPs can also endow the HOGFs with antibacterial features,demonstrat-ing significant potential in personal healthcare.