Development and Experiment of Multi- functional Wood Dehumidification Dryer

A multi functional wood dehumidification dryer has been developed recently. The dryer can carry out air dehumidification by using only one refrigeration system, in which heat supplying and moisture air are exhausted by changing the position of several air dampers. In this paper, the work principles and characteristics of the dehumidification dryer are introduced, and the testing results about the thermal engineering performance of the dehumidification dryer, as well as the experiment results of drying several species of lumbers are expounded.

Performance analysis of three-stage liquid desiccant deep dehumidification processor driven by heat pump

A new type of a heat pump driven three-stage lithium bromide liquid desiccant deep dehumidification processor is presented,which can dehumidify the outdoor humid air to a rather dry state,even when there is no available indoor exhaust air.The test results show that with an outdoor air temperature of 28 to 31 ℃ and an outdoor air humidity ratio of 11 to 14 g/kg,the supply air temperature and the supply air humidity ratio are 1.6 to 2.6 ℃ and 2.6 to 3.0 g/kg,respectively,and the coefficient of performance（COP）of the processor is 1.8.During the test,a liquid pipeline link problem leading to mixture losses of hot and cold liquid desiccants is found.These pipelines are modified.Then,the performance of the modified processor is investigated.And the experimental results show that with an outdoor air temperature of 25 to 32 ℃ and an outdoor air humidity ratio of 18 to 21 g/kg,the supply air temperature and the supply air humidity ratio are 3.2 to 4.0 ℃ and 3.4 to 3.6 g/kg,respectively,and the COP is 2.8.Finally,a mathematical model of the processor is established.The comparison of the simulation results and the test results of the processor exhibits that the pipeline modification improves the performance by about 20%.

Liquid dehumidification-assisted evaporative supercooling method for ice slurry production

Due to the fact that the conventional ice slurry production system using supercooled water suffers from ice block and depends heavily on electric power,a novel ice slurry production system is proposed.The new system consists of two major parts：the evaporative supercooling process and the liquid dehumidification process.The classical diffusion-control equation is improved by introducing an impact factor into the simulation analysis in the evaporative supercooling process.Meanwhile,experiments are carried out by adopting the particle analyzer to detect the radii and the velocities of the droplets,and an infrared camera to examine the temperature profile of the physical process.It is found that the theoretical conclusion agrees well with the experimental results.Compared with the conventional system,the new system can alleviate the burden on electric power and raise efficiency.These improvements are essentially attributed to the reutilization of the inner waste heat generated from the system itself.

Optimized Operation of a Solar-Driven Thermoelectric Dehumidification System for Fresh Water Production

The work presents a parametric analysis of the performance of a solar-driven thermoelectric system to dehumidify air and produce fresh water. The system is combined with a solar distiller humidifying ambient air to enhance distillate output to meet the specified fresh water needs for a residential application. The presented system is a totally renewable energy-based system taking advantage of the clean solar energy. A model is developed to simulate the air dehumidification process using TEC （thermoelectrically cooled） channels. An optimization problem for setting system operational parameters is formulated to meet the fresh water requirement of 10 liters per day for a typical residential application in the Lebanese coastal humid climate. Using five TEC channels of length of 1.2 m and area of 0.07 - 0.05 m^2 integrated with 1.2 m^2 solar distiller is capable of meeting the water demand, where the air mass flow rate introduced to each TEC channel is optimally set at 0.0155 kg/s. The optimal electrical current input to the TEC modules from the photovoltaic solar panels varied depending on the month and is set at 2.2 A in June, 2.1 A in July and 2.0 A in August, September and October per each TEC module.

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.

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.

Improvement of conventional liquid desiccant dehumidification technology

A new system of liquid desiccant dehumidification,called ultrasound atomization dehumidification system,is proposed.In this system,a packed bed is replaced by ultrasound atomization technology,so high resistance and liquid desiccant consumption caused by the packed bed are avoided.A mathematical model is established to predict the efficiency and the liquid consumption of the dehumidification process under ideal conditions.Through comparing the simulation results with the experimental data of a conventional packed-bed dehumidifier,it is found that the liquid desiccant consumption of the conventional packed-bed dehumidifier is much greater than that under ideal conditions.In the proposed system,the dehumidification process occurs on the surfaces of the micron liquid desiccant droplets produced with the irradiation of ultrasound,so there is a greater contact area created with the same quantity of the liquid desiccant;moreover,the power consumption is lower because there are no nozzles and no solution pump.It can be seen that this new system is closer to ideal conditions when compared with the conventional liquid desiccant dehumidification system.

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.

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).

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.

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 %.

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.

Industrial Application of a Deep Purification Technology for Flue Gas Involving Phase-Transition Agglomeration and Dehumidification

A moist plume forms when the flue gas emitted from wet desulfurization equipment exits into the ambi- ent air, resulting in a waste of water resources and visual pollution. In addition, sulfur trioxide （SO3）, water with dissolved salts, and particles in the wet flue gas form secondary pollution in the surrounding atmosphere. In this study, a deep purification technology for flue gas involving phase-transition agglom- eration and dehumidification （PAD） is proposed. This deep purification technology includes two technical routes： the integrated technology of phase-transition agglomeration and a wet electrostatic precipitator （PAW）; and the integrated technology of phase-transition agglomeration and a mist eliminator （PAM）. Industrial applications of PAW and PAM were carried out on 630 and 1000 MW coal-fired units, respectively. The results show that the average amount of recycled water obtained from wet flue gas by means of PAD is more than 4 g.（kg.℃）-1 Decreasing the wet flue gas temperature by 1.5-5.3 ℃ allows 5%-20% of the moisture in the flue gas to be recycled; therefore, this process could effectively save water resources and significantly reduce water vapor emissions. In addition, the moist plume is effectively elim- inated. With the use of this process, the ion concentration in droplets of flue gas is decreased by more than 65%, the SO3 removal efficiency from flue gas is greater than 75%, and the removal efficiency of par- ticulate matter is 92.53%.

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^-2·s^-1, and 0.7-1.3kg·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.

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.

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.

An ultrasonic humidification fluorescent tracing method for detecting unsaturated atmospheric water absorption by the aerial parts of desert plants

Atmospheric water absorption by plants has been explored for more than two centuries, and the aerial parts of plants, particularly the leaves of certain species, have been demonstrated to have an ability to absorb and utilize saturated atmospheric water such as fog, dew and condensed water. So far, however, there have been few studies on the aerial parts of desert plants in their absorption of unsaturated water from the atmosphere. This study presents an ultrasonic humidification fluorescent tracing method of detecting unsaturated atmospheric water absorption by the aerial parts of desert plants. We constructed an organic glass room based on the sizes of field plants. Then, the aboveground parts of the plants were humidified in the sealed glasshouse using an ultrasonic humidifier containing fluorescent reagents. The humidity and wetting time were controlled by turning on or off the humidifier according to the reading of a thermo-hygrometer suspended in the glasshouse. Fluorescence microscopy was employed to observe these plant samples. This method can generate unsaturated atmospheric water vapor and incorporate other fluorescent reagents or water-soluble chemical reagents for gasified humidification. In addition, it can identify plant parts that absorb unsaturated atmospheric water from the air, detect water absorption sites on the surface of leaves or tender stems, and determine the ability of tissues or microstructure of aerial parts to absorb water. This method provides a direct visual evidence for the inspection of leaf or tender stem microstructure in response to unsaturated atmospheric water absorption. Moreover, this method shows that aqueous pores in the cuticles of leaves or tender stems of desert plants are large enough to allow the passage of ionic fluorescent brightener with a molecular weight of up to 917 g/mol. Thus, this paper provides an important approach that explores the mechanism by which desert plants utilize unsaturated atmospheric water.

Study on Calculations of Humidification Tower with Humid Air Turbine Cycle at High Temperature and Pressure

Humidification is an important step in humid air turbine system. The calculation on humidification is carried out at 423.15—573.15K, 5—15MPa. The results suggest that to produce high-enthalpy moist air, high water temperature and large water flow are needed. The water temperature is the most sensitive parameter to the humidification tower. And it is better for the humidification tower to work at temperature higher than 523 K when the system pressure is higher than 5 MPa. The comparison between the model used in this paper and ideal model shows that the ideal model can be used in simulation to simply the calculation when the temperature is lower than 473 K and pressure is lower than 5 MPa.

Humidification vibration deformation behavior of intact loess

A parameter, known as the parameter of humidification vibration deformation, was proposed, describing quantitatively the impact of water content on vibration settlement deformation, and its relationship with humidification water content, dynamic shear stress peak value, initial consolidation stress and vibration frequency was built. The result shows that 1） the parameter of humidification vibration deformation increases with the vibration shear stress peak value increasing. 2） The humidification water content has significant influence on the curve of the parameter of humidification vibration deformation and the peak vibration shear stress. When the humidification water content is low, the curve increases slowly. However, when the humidification water content is high, the curve increases rapidly. 3） Initial consolidation stress has significant influence on the humidification vibration deformation coefficient. When initial consolidation stress is not large enough to destroy the loess structure, with initial consolidation stress increasing, the humidification vibration deformation coefficient decreases. On the contrary, the humidification vibration deformation coefficient increases with initial consolidation stress increasing. 4） With the increase of vibration time, the parameter of humidification vibration settlement shows an increasing trend overall. The initial dynamic shear stress peak value and humidification water content all have significant effects on the curve of the parameter of humidification vibration settlement and vibration time. However, the humidification water content is even more significant.