Papers by Keyword: Dehumidification

Abstract: As an important factor to measure environmental comfort, humidity control is very important. However, previous dehumidification methods have many defects, such as condensation and adsorbents, which often require a lot of energy. The growing requirements of an indoor environment can stem from the development of living levels and technology. Humidity, as an important factor to measure environmental comfort, affects living and production, and indoor humidity control is an indispensable part of modern architecture. However, there are many defects in the previous dehumidification methods, such as condensation dehumidification, which often requires a lot of energy. Traditional adsorbents (such as zeolite silica and activated alumina) have problems with fragile structures or high regeneration temperatures. In this paper, an indoor dehumidification device based on the porous metal-organic framework {MOF-801, Zr₆O4(OH)₄(Fumarate)₆}, can realize the indoor dehumidification process only by using a small amount of solar energy (1 kilowatt per square meter). The device is expected to remove 0.2113 kg/h of moisture per square meter MOF-801, only needs a few additional energy inputs.

Abstract: In this paper, an experimental work studies the principal operating parameters of a proposed desalination process using air humidification-dehumidification method. The major objective of this work is to determine the humid air behavior through the desalination system. Different operating conditions including the effect of the water temperature at the entry to the humidifier, the ratio of the mass of water to the air, the air/water flow rate, and cooling water at entry the dehumidifier on the desalination performance were studied. The results show that the freshwater increases with increasing the water temperature at the inlet of the humidifier, the ratio of the mass of water to air, and cooling water flow rate in the dehumidifier. Cooling water outlet temperature at the condenser increases with increasing the water temperature at humidifier inlet. Also, it decreases as increasing cooling water flow rate while the ratio of the mass of water to air achieves the highest productivity and gained output ratio (GOR). The achieved mass ratio (MR) is 4.5 and the mass flow rate of air is 0.8 kg/min.

Abstract: In order to control humidity in air conditioning system, various desiccants are used to dehumidify air in air conditioners. One of simple methods, which can be used to coat desiccant materials on surface of heat exchanger in air conditioners, is dip coating. Typical, desiccants used in dehumidifying system is silica gel in a form of solid-state powder. This powder has low adhesion with the heat exchanger surface. To improve adhesion of the silica gel powder, some glue is generally applied on the surface of heat exchanger. The dehumidification properties of silica gel, however, will be remarkably reduced because of less surface area of silica gel powder. Instead of silica powder, this work aims to synthesize silica gel using sol-gel method, which the sol-state material can be suitably used in dip coating. In experimental study, silica gel was synthesized by sol-gel method of precursors with 1 M sulfuric acid (H₂SO₄). The pH was adjusted using sodium silicate solution (Na₂O(SiO₂)_x.xH₂O) and rinsing with DI water. Surface area, pore volume and size, phase composition, morphology, and percentage of moisture adsorption of the synthesized silica gel were characterized. Silica gel fabricated with pH 5 showed the highest percentage of moisture adsorption compared with other samples. In addition to the highest percentage, silica gel with pH 5 could adsorb water up to 28 times of its own weight. X-ray diffraction (XRD) results showed that Na₂SO₄ impurity were successfully eliminated after rinsing with DI water more than 4 times. Finally, adhesive property of silica gel on aluminium-fin samples was tested with scalloped tape-test method. It was observed that, to improve the adhesion property of silica gel on the aluminium fins, prior to dipping of silica gel, the fins should be etched with sulfuric acid. The acid can adjust the surface of fines to be much rougher.

Abstract: A novel evaporative cooling system, which uses an ejector for refrigeration, integrated with a membrane dehumidification module has been studied. In the system investigated, where ultrasonic nebulizers are utilized to pulverize water into droplets for evaporation. The cooling effect influenced by the intensity of ultrasonic automization has been experimentally studied. The prototype of the membrane module is made and several experiments are conducted to evaluate its effect on the system. It is found that, in a permanent inlet air condition, the temperature drop would increase as intensity of ultrasonic grows. Cooling effect of the ejector is better in dry ambient condition compared to moist one. When in the humid environment, the membrane module would increase the system refrigeration capacity by 80%.

Abstract: Desiccant dehumidification can reduce energy consumption of air conditioner. However, mass transfer of water from air to the desiccant is critical for efficiency. Mass transfer characteristics of spray column were experimentally studied, and some correlations were attempted.

Abstract: According to the existing problems of conventional air conditioning system, this paper presents a new form air-conditioning based on the principle of gravity cycle, analyze its merits and drawbacks and application area, to provide a theoretical basis for the popularization and application of the new air conditioning form.

Abstract: Liquid dehumidification air-conditioning system is a promising air-conditioning system as it is environment-friendly, capable of utilizing low grade heat and less dependent on the electric power. However, because of the heat waste, its performance is not yet as competitive as vapour compression system. To improve, a photovoltaic driven system is proposed in this paper: electricity is applied to regenerate desiccant; the electric energy comes from solar power. Performance analysis has been made. The results show the coefficient of performance of the new system is influenced by the concentration of the desiccant and can approach 6 at certain circumstances. It also shows that LiBr solution is more favorable among three common used desiccants. Moreover, this paper presents the new progress of experimental research on this system.

Abstract: In this paper a new type of open absorption the liquid desiccant, air conditioning system will be introduced. The dehumidifier and regenerator play the most important role in this system.For liquid-gas contact, packed towers with low pressure drop provide good heat and mass transfer characteristics for compact designs. Thus, this analysis considers the packed tower liquid desiccant systems. The experimental data have been obtained from a built prototype of liquid desiccant system in a packed bed unit with a surface area per unit volume ratio of 125m2/m3, the liquid desiccant, viz lithium chloride. The result showed that the mean mass transfer coefficient of the packing dehumidifier was 0.02kg/m2s. Also the absorber characteristic parameter, the packing size or number of transfer units (NTU), and air-to-desiccant solution mass flow rate ratio (ASMR) are crucial parameters. These parameters affect humidity and enthalpy effectiveness and will be introduced and defined in this paper.

Abstract: To improve indoor air quality, mass transfer is an important part in air handling process, which is helpful for the control of humidity of air. This paper presents mass transfer dynamic analysis of isothermal and opposite flow process theoretically. The pressure difference analysis is used to show the changing of pressures of two phases in dehumidification process. It calculates the partial pressure of water vapor in wet air and the vapor pressure of LiCl solution. Also it gives the curves of pressure change in dehumidification of isothermal and opposite flow by lithium chloride. Results from this paper can be used as theoretical foundation for the experimental design of dehumidification of air by LiCl solution.

Abstract: Microwaves are electromagnetic waves of frequencies from 300 MHz to 300 GHz, corresponding to wavelengths from 1 m to 1 mm. For industrial application is allowed more frequencies, but we are mainly interested in the frequency 2 450 MHz, a wavelength of 12,2 cm, which we use in our applications. The heating occurs so that the electric field in the water molecules orient themselves according to polarization. Microwaves are a classical electromagnetic radiation with frequency lower than the solar radiation and therefore leave no residual radiation harmful to health. Using the device is completely safe, damage to health can occur only by direct irradiation of a few cm for several minutes, either intentionally or careless handling of the machine.