Humidity Rate Research Articles

An efficient strategy based on proper orthogonal decomposition for rapid determination of the location and rate of water vapor humidification in aircraft cabins

Currently, the air in commercial aircraft cabins during flights routinely exhibits extremely low relative humidity. But none of the previously published studies have addressed optimization of the humidification parameters in order to, create the desired humidity distributions in aircraft cabins at minimal cost. This study proposed an efficient strategy to accomplish the task. Under this strategy, a database of various potential humidification locations for aircraft cabins is first constructed. One scenario in the database is then selected by computational fluid dynamics (CFD)-based enumeration. Next, with the humidification location as prior information, the humidification rate and the air-supply temperature from the main ventilation system can be inversely designed by proper orthogonal decomposition. The above strategy was applied to a three-dimensional aircraft cabin model for the validated CFD cases. The results showed that an appropriate humidification for the cabin might both improve the thermal comfort of passengers and increase the humidity levels in the cabin; a decrease of the air-supply temperature from the main ventilation system would be beneficial in reducing the water vapor humidification rate required for passengers and allowing a higher humidification rate to be tolerated for the cabin walls. The parameters that improved the cabin air environment without significant moisture accumulation on walls were also provided by the proposed strategy. Compared with the full CFD simulation method, the proposed strategy is capable of providing accurate ranges of parameters while reducing the computing time by more than 95%, which demonstrates its competitive prospects.

Investigating the Impact of Hydrogen Gas Moisture Content on Electricity Generation in PEM Fuel Cells

In the realm of energy sources, non-renewable fossil fuels, such as petroleum derivatives, continue to pose a significant threat to our planet. Currently, hydrogen energy, derived from renewable sources, is under extensive research, primarily due to its high efficiency, versatile applications, and zero carbon emissions. Hydrogen gas has become an indispensable alternative energy source owing to its numerous advantages. The technology that enables efficient utilization of hydrogen gas as an energy source is fuel cells, with Polymer Electrolyte Membrane Fuel Cells (PEM Fuel Cells) being the most significant advancement in this field. In this study, anode and cathode moisture levels were investigated by experimental study on the obtained efficiency of PEM fuel cell performance. Pure hydrogen and oxygen gases were used in the anode and cathode sections of the experiment, respectively. The test stand and a 6 cell 35 watt fuel cell with 9 cm2 active area were used for the test. Temperature and water accumulation, especially humidification in PEM fuel cells, can be achieved by keeping the hydrogen flow, oxygen flow and battery temperature under control. In the experimental study, the fuel cell humidification rate is gradually increased by keeping the flow and line temperature constant. 30% - 35% - 40% - 45% - 50% - 55% - 60% - 65% - 70% of the results obtained in the voltage, amperage and their effects on watts. As a result of the experimental study, humidification rate has a significant effect on the performance of PEM fuel cell. With the increased humidification temperature, the performance of the installed system increased significantly and nominal values were found. However, it is observed that the performance decreases after a certain period of time in the values higher than 60%.

Study on the Heat and Mass Transfer Characteristics of Humidifiers in Humidification–Dehumidification Desalination Systems

The humidifier plays a key role in a humidification–dehumidification (HDH) desalination system; it directly affects both the freshwater production efficiency and energy consumption ratio of the system. In this study, for a humidifier in an HDH system, a heat–mass coupled differential equation model of spray water and air on the surface of the packing material was established, and the effects of parameters such as the spray water temperature (tw), mass flow rate of spray water (mw), air temperature (ta), and air mass flow rate (ma) on the humidification performance of humidifiers composed of eight different types of packing materials were investigated. The results show the following: (1) Under the same inlet spray water and air conditions, the humidification performance of different packing materials from good to bad is as follows: cellulose paper, polypropylene, hackettes, saddles, snowflakes, wooden slats, polyvinyl chloride, gunny bag cloth. (2) Increasing the tw can significantly improve the humidification performance. To achieve higher humidification energy efficiency, it is recommended to increase the tw to above 80 °C. (3) With the increase in the mw, although the humidification efficiency (εhum) decreases slightly, the humidification rate (mhum) increases, and the specific humidification energy ratio (ηhum) decreases accordingly. To maintain a high mhum and a low ηhum, it is advisable to control the mw at not less than 0.5 kg/s. (4) Increasing the humidifier inlet ta can improve the mhum, εhum, and ηhum, although not as effectively as increasing tw. (5) Increasing the ma can improve mhum and εhum. However, it simultaneously increases the ηhum. The results of this study can provide theoretical guidance for the selection of efficient packing materials and the optimization of humidifier operating conditions in HDH desalination systems.

Study on the Cooling Effect of Double-Layer Spray Greenhouse

Greenhouses provide suitable environmental conditions for plant growth. Double-layer plastic greenhouses are often used in many regions to ensure normal crop growth during winter since single-layer plastic greenhouses have poor insulation. However, during summer, the high insulation of double-layer plastic greenhouses, combined with excessive external solar radiation, can cause high temperatures inside the greenhouse that are not suitable for plant growth and require cooling. In this study, we propose a double-layer spray greenhouse using a high-pressure spraying system that is placed inside the double film that allows for additional cooling capacity during the summer in order to sustain plant growth. A greenhouse platform test was set up to investigate the optimum operating conditions for the nozzles and to explore changes in greenhouse microclimate under different nozzle operating conditions. The results show that (1) the cooling rate increases with increasing water supply pressure, nozzle diameter and spraying time, and the humidification rate is consistent with the change in the rate of cooling. (2) The optimal condition for cooling in this experiment is achieved with a 120° double nozzle with a nozzle diameter of 0.30 mm, a water supply pressure of 6 MPa, and a spraying time of 15 min, which can reduce the temperature by up to 5.36 °C and serve as a reference for the summer cooling of the double-layer greenhouse.

Coupled synergistic development of the sports industry and urban park ecological environment

The quality of sports and leisure has received the attention of local sports departments. The construction of sports parks has become a new hot spot to enhance the image of the city and develop sports. Therefore, this paper studies the coupled and synergistic development of the sports industry and urban park ecology. First, the current situation of urban sports parks in China is analyzed. Then the affiliation numerical method was introduced into the evaluation of park ecology. Finally, we calculate the acquisition index and evaluation and use it to analyze the ecological and environmental effects of plant communities. The results showed that in Manduhai Park, Hohhot, the temperature change of plant communities first rose and then slowly decreased, with the highest temperature at 4 pm and the lowest at 8 pm, and the cooling rate was 3.34%~5.05%. The relative humidity was highest at 8:00 a.m. and lowest at 4:00 p.m., with a humidification rate of 1.82% to 12.18%. Wind speed is the highest at 12:00 noon and the lowest in the morning and evening; the human body feels the best comfort in the morning at 8:00, and feels uncomfortable around 12:00 and 16:00, with a variation range of 71.77±2.73 to 73.19±2.54; the research found that 42% of the visitors chose leisure and sports activities; followed by 39% for entertainment and games, and 12% for cultural activities again. Thirty-one percent of the visitors were satisfied with the leisure and sports facilities, 31% thought they were average, 28% reached only basic satisfaction, and 10% were not satisfied with the leisure and sports facilities.

Numerical Analysis of Humidification Condition Effects on Protonic Ceramic Fuel Cell Performance Considering Concentration Overpotential

Protonic ceramic fuel cells (PCFCs) operating at an intermediate temperature range (400–600 °C) show high performance due to high proton conductivity in the electrolyte. Especially, because the water steam is generated at the oxygen side, so there is less dilution effect on fuel. Therefore, one of the main merits of PCFCs is that it can operate with extremely high fuel utilization. Furthermore, a higher fuel humidification rate leads to higher proton conductivity. However, under relatively high steam partial pressure, the concentration overpotential effect on cell performance may become non-negligible. In the present study, the performance of PCFC under several fuel humidification conditions is investigated by considering the influence of concentration overpotential by numerical analysis.

Experimental assessment of energy tower's performance: evaluation of the impacts of solar radiation, humidity, and chimney's height on the overall efficiency.

Solar energy is one of the most feasible options to produce energy in countries where unexploited desert areas or solar radiation are abundant. An energy tower is an effective system for electrical power generation that can perform more efficiently along with solar radiation. As the primary aim of the present study, effects of different environmental parameters on total efficacy of energy tower were investigated. In this study, the efficiency of the energy tower system is investigated experimentally by an indoor fully adjustable apparatus. In this regard, a comprehensive set of influencing parameters like air velocity, humidity, and temperature and the effects of tower height on the performance of the energy tower are individually assessed. It is demonstrated that there is a direct relationship between an increase in humidity percentage of the surrounding and performance of energy tower, meaning that a 274% increase in humidification rate led to 43% elevation in airflow velocity. The kinetic energy increases in the direction of airflow from top to bottom, and as the height of the tower lengthens, the kinetic energy enhances and subsequently increases the overall efficiency of the tower. An elevation about 2.7% in airflow velocity was seen due to an increase from 180 to 250cm in chimney height. Although the energy tower performs efficiently in the nighttime, airflow velocity increases averagely about 8% during the daytime and at the peak of the solar radiation, the airflow velocity enhances by 58% compared to nighttime.

Humidification performance of hollow-fiber membrane humidifier for air-conditioning applications

In this research, a new humidification method is proposed, and the humidification performance of a single module is experimentally investigated. The humidification module was manufactured in a cylindrical structure, and the humidification performance was evaluated by supplying air to the feed side and circulating water to the permeate side. The humidification performance was evaluated according to two main operating variables, circulating water temperature and circulating water flow rate. Experimental results showed that the humidification rate of the proposed module was 0.59 ∼ 9.49 kg/s, and the humidification effectiveness was 11.8 ∼ 95.6% under various operating conditions. The temperature of the circulating water significantly affects the humidification performance, but the flow rate of the circulating water has an insignificant effect on the humidification performance. As a result, the proposed humidifier can supply humid air with a relative humidity of 80% to the room without a temperature change under standard conditions.

Influence of coordinated operation of distributed and centralized thermoelectric dehumidifiers on the environment of prefabricated chambers

With the development of new power systems, the construction concept imposes new requirements on the internal environment of the equipment in terms of moisture protection. The study addresses the requirements of dehumidification and temperature control in the internal environment of prefabricated substations and builds the test platform for prefabricated substations to investigate the effect of coordinated operation of distributed thermoelectric dehumidifier (DTD) and centralized thermoelectric dehumidifier (CTD) on the prefabricated bay environment. It is found that: distributed dehumidifiers are effective in dehumidifying environments with humidification rates less than 2.848 ml/min; CTD should be used when the humidification rate is greater than 2.848 ml/min. DTD its relative humidity regulation can be strong but cause the ambient temperature to rise, CTD power consumption is low and the ambient temperature change is small. When the coordinated operation of the distributed and centralized dehumidifier is used to reduce the relative humidity from 95% to 69.5%, its total power consumption is only 0.260 kWh and the ambient temperature increases by 3.2 °C. Therefore, the comprehensive performance advantage is obvious, which is conducive to improving the ability to resist sudden changes in the environment and ensuring stable equipment operation.

Analysis of Rewetting Characteristics and Process Parameters in Tobacco Strip Redrying Stage

To study the rewetting characteristics of tobacco strips during the redrying stage, a conjugate heat and mass transfer model of tobacco strips was established based on their physical properties. The fundamental relationship between the multiphysical fields and humidity fields of tobacco strips and the key process parameters was considered in this model, and the feasibility of the model was verified via experiments. Based on this model, the transfer and variation laws of the moisture content, humidification rate, and temperature of tobacco strips under different relative humidity and temperature conditions were studied, and the rewetting process parameters of tobacco strips were determined using COMSOL Multiphysics. The results show that this model can be used to study the rewetting characteristics of tobacco strips during the redrying stage. The rewetting of tobacco strips can be divided into two stages, namely, the accelerated stage and approximate constant rate increase stage, where the former stage has a greater impact on the rewetting effect. The higher the relative humidity and temperature, the greater the change in the moisture content, humidification rate, and effective moisture diffusivity, and the faster the increase rate. The best rewetting effect was achieved when the relative humidity was 85% and the temperature was 55 °C. Under these conditions, the moisture content of the tobacco strips was 11% to 13%, the humidification rate was 0.03 %/s to 0.29 %/s, the highest effective moisture diffusivity was 7.8 × 10−10 m2/s, and the maximum activation energy was 37.86 kJ/mol. This study provides a theoretical basis and data support for analyzing the characteristics of the rewetting process and for optimizing the process parameters.

Sensitivity and areal differentiation of vegetation responses to hydrothermal dynamics on the northern and southern slopes of the Qinling Mountains in Shaanxi province

The Qinling Mountains, located at the junction of warm temperate and subtropical zones, serve as the boundary between north and south China. Exploring the sensitivity of the response of vegetation there to hydrothermal dynamics elucidates the dynamics and mechanisms of the main vegetation types in the context of changes in temperature and moisture. Importance should be attached to changes in vegetation in different climate zones. To reveal the sensitivity and areal differentiation of vegetation responses to hydrothermal dynamics, the spatio-temporal variation characteristics of the normalized vegetation index (NDVI) and the standardized precipitation evapotranspiration index (SPEI) on the northern and southern slopes of the Qinling Mountains from 2000 to 2018 are explored using the meteorological data of 32 meteorological stations and the MODIS NDVI datasets. The results show that: 1) The overall vegetation coverage of the Qinling Mountains improved significantly from 2000 to 2018. The NDVI rise rate and area ratio on the southern slope were higher than those on the northern slope, and the vegetation on the southern slope improved more than that on the northern slope. The Qinling Mountains showed an insignificant humidification trend. The humidification rate and humidification area of the northern slope were greater than those on the southern slope. 2) Vegetation on the northern slope of the Qinling Mountains was more sensitive to hydrothermal dynamics than that on the southern slope. Vegetation was most sensitive to hydrothermal dynamics from March to June on the northern slope, and from March to May (spring) on the southern slope. The vegetation on the northern and southern slopes was mainly affected by hydrothermal dynamics on a scale of 3–7 months, responding weakly to responding weakly to hydrothermal dynamics on a scale of 11–12 months. 3) Some 90.34% of NDVI and SPEI was positively correlated in the Qinling Mountains. Spring humidification in most parts of the study area promoted the growth of vegetation all the year round. The sensitivity of vegetation responses to hydrothermal dynamics with increasing altitude increased first and then decreased. Elevations of 800 to 1200 m were the most sensitive range for vegetation response to hydrothermal dynamics. The sensitivity of the vegetation response at elevations of 1200–3000 m decreased with increasing altitude. As regards to vegetation type, grass was most sensitive to hydrothermal dynamics on both the northern and southern slopes of the Qinling Mountains; but most other vegetation types on the northern slope were more sensitive to hydrothermal dynamics than those on the southern slope.

Experimental Study on Performance of Anode Humidification System of Large Power Fuel Cell Stack

The heat and mass transfer characteristics of the hydrogen membrane humidification system of a 70kW atmospheric pressure proton exchange membrane fuel cell stack were experimentally studied. The shell-and-tube membrane humidifier is applied to the high-power fuel cell stack hydrogen humidification system, which has the advantages of fast humidification rate and good wettability of humidified hydrogen. The liquid hydrogen is humidified by liquid water. After the humidification in the experiment, the hydrogen can always reach the supersaturation state. When the hydrogen flow rate is constant, the temperature difference between the membrane humidifier humidification water inlet and outlet decreases with the increase of the water flow rate, and the hydrogen outlet The temperature approaches the humidification water inlet temperature as the liquid water flow rate increases; increasing the humidification water flow rate can reduce the temperature difference before and after the humidification water passes through the membrane humidifier. When the temperature and flow rate of the humidified water are constant, the fuel cell stack load increases, and the relative humidity of the humidified hydrogen outlet does not change significantly.

Achievement of humidification and dehumidification desalination system by utilizing a hot water sprayer and ultrasound waves techniques

An experimental investigation on the solar system for water desalination was conducted according to the methodology of humidification-dehumidification. Tests have been properly designed and constructed to efficiently assess the productivity of fresh water during the three summer months under local weather conditions of Alexandria, Egypt. The heated air is humidified through two sequent stages,the primary stage is achieved through employing a heated water spatter from the evacuated solar collector. The Further stageis employing anultrasonic technique for its highly efficient humidification rate. The findings of fresh water output rate is affected by two main parameters; firstly the mass flow rates of both air and water spray, secondly solar radiation. Furthermore, an investigation of heated water spray flow rate over the total flow rate at four values of 0.175, 0.2, 0.25 and 0.3were done respectively. The maximum amount of daily productivity reaches to 44.8 kg/day with mass flow rate of 0.46 kg/s for air, while hot water spray ratio of 0.3. The ultrasonic humidifier improves the daily productivity by 9.3% at 0.24 kg/s and 14.6% at the maximum value of the air mass flow rate 0.46 kg/s. Economic analysis showed that the fresh water cost is about 0.0144 USD/L.

Numerical simulation of liquid desiccant evaporator driven by heat pump

The standard k-e turbulence model and discrete phase model (DPM) were used to simulate the heat and mass transfer in a liquid-desiccant evaporator driven by a heat pump using FLUENT software, and the temperature field and velocity field in the device were obtained. The performance of the liquid-desiccant evaporator was studied as the concentration of the inlet solution varied between 21% and 30% and the pipe wall temperature between 30 and 50 °C. Results show that the humidification rate and the humidification efficiency increased with the inlet air temperature, the solution flow rate, the solution temperature, and the pipe wall temperature. The humidification rate and humidification efficiency decreased with increasing moisture content in inlet air and the concentration of inlet solution. The humidification rate increased substantially but the humidification efficiency decreased as the inlet air flow rate increased. The error between the simulations and experimental results is acceptable, meaning that our model can provide a theoretical basis for optimizing the performance of a humidifying evaporator.

Numerical simulation of gas liquid two-phase flow in anode channel of low-temperature fuel cells

In this study, the gas liquid two-phase flow of low-temperature fuel cells is simulated to study the water removal process in the anode channel utilizing VOF (volume of fluid) method. It is found that the water removal process in the cathode channel is easier compared to that in the anode under the same operating condition and inlet velocity. Increasing the humidification rate and contact angle is helpful for water removal. Moreover, further simulations show that in the semicircle-U channel, the water can be removed successfully, but it will be stuck in the corner in the rectangular-U channel, which can be prevented by changing the contact angle of specific walls into extremely hydrophilic or hydrophobic. Extremely hydrophilic wall would make the entire water pave on the wall and smash into little droplets which is not only helpful in water removal and evaporation but also prevents the water from blocking the holes on the Gas Diffusion Layer (GDL). And different hydrophilic/hydrophobic levels also influence the water removal.

Experimental investigation of solar heating and humidification system based on desiccant bed heat exchanger

ABSTRACTIn this article, an experimental investigation has been made on a solar heating and humidification system. In this system, an evacuated tube solar water heater is connected to the desiccant bed heat exchanger (DBHE) by connecting pipes. The evacuated tube solar water heater supplies required heat to the DBHE for the regeneration of desiccant material. Various types of solid and composite desiccant materials have been used in the DBHE to investigate their effect on the system performance. It has been found that the system obtained its best performance with silica gel with average humidification rate of 0.63 kg/h. The maximum temperature difference of process air has been found as 16°C at the flow rate of 295.2 kg/h.

Starch characterization after ozone treatment of wheat grains

Soft wheat grains were subjected to oxidation by ozone treatment. A Box Benhken design with three variables (humidification rate, ozone inlet concentration and reaction time) was used for the experiment. Two wheat cultivars differing on their technological properties were used. The products were characterized by determining rheological, thermal and other physicochemical properties such as RVA (Rapid Visco Analyzer), DSC (Differential Scanning Calorimetry), molecular weight distribution and amylopectin branched chain length distribution. Contrary to previous works, results clearly show no significant effect of ozone treatment on wheat starch in our experimental conditions (i.e. starch extracted from ozonated whole wheat grain) whatever the cultivar studied. Only slight increases of carboxyl groups have been noticed with increasing ozonation. Modifications observed on rheological properties in flour samples (i.e. alveographic and RVA measurements) in previous works (Gozé et al., 2015) could mainly be explained by the oxidation of others molecules such as proteins and non-starch polysaccharides.

Integration of electrochemical impedance spectroscopy functionality in proton exchange membrane fuel cell power converter

This paper presents a solution of implementation of electrochemical impedance spectroscopy (EIS) functionality in the power converter used for Proton Exchange Membrane Fuel Cell (PEMFC) power management. The fuel cell is electrically coupled to an electric vehicle DC bus using a DC/AC/DC converter based on an inverter stage, a high frequency power transformer stage, and a rectifier stage. The EIS is achieved by the power converter in order to be performed without additional hardware, cost and volume. The proposed EIS process is integrated in the power control to allow real time using of EIS results for embedded diagnosis or control improvement. An experimental platform developed in the laboratory has validated the online EIS method on a 750 W 20-cell-stack. Experimental validation tests presented in this paper illustrate spectral impedance monitoring for variations of requested current, air humidification rate and hydrogen flow rate.

Investigation by a Genetic Algorithm of the Effect of Moisture Diffusion on the Fiber Matrix Interface Damage of Graphite/Epoxy Nanocomposite

The Nanocomposite graphite/epoxy material has a high mechanical tensile strength after improving, its Young's modulus substantially strengthening the matrix with nano-particles of graphite. Few patents on the absorption of water by a nanocomposite were published. In this study, we investigate the influence of the absorption of water by the matrix on the fiber matrix interface damage. Our contribution is related to the development of an analytical model based on a genetic approach, using a basic model formalism of Weibull, the model of Cox and the laws diffusion of water in a polymer, where the damage was located by a non-linear acoustic technical. The results show that the rate humidity at 60% does not affect the fiber matrix interface damage of graphite epoxy nanocomposite compared to the other composite materials carbon-epoxy (T300/914) and Polyétheréthercétone (PEEK/APC2) whose interface damage increase to 0.2. Therefore, our findings revealed that the model worked well with the phenomenon of damage to unidirectional composite and nanocomposite materials. Keywords: Damage, fiber, genetic algorithm, interface, matrix, nanocomposite, non-linear acoustic technical.

Competition between water uptake and ice nucleation by glassy organic aerosol particles

Abstract. Organic aerosol particles play a key role in climate by serving as nuclei for clouds and precipitation. Their sources and composition are highly variable, and their phase state ranges from liquid to solid under atmospheric conditions, affecting the pathway of activation to cloud droplets and ice crystals. Due to slow diffusion of water in the particle phase, organic particles may deviate in phase and morphology from their thermodynamic equilibrium state, hampering the prediction of their influence on cloud formation. We overcome this problem by combining a novel semi-empirical method for estimation of water diffusivity with a kinetic flux model that explicitly treats water diffusion. We estimate timescales for particle deliquescence as well as various ice nucleation pathways for a wide variety of organic substances, including secondary organic aerosol (SOA) from the oxidation of isoprene, α-pinene, naphthalene, and dodecane. The simulations show that, in typical atmospheric updrafts, glassy states and solid/liquid core-shell morphologies can persist for long enough that heterogeneous ice nucleation in the deposition and immersion mode can dominate over homogeneous ice nucleation. Such competition depends strongly on ambient temperature and relative humidity as well as humidification rate and particle size. Due to differences in glass transition temperature, hygroscopicity and atomic O / C ratio of the different SOA, naphthalene SOA particles have the highest potential to act as heterogeneous ice nuclei. Our findings demonstrate that kinetic limitations of water diffusion into organic aerosol particles are likely to be encountered under atmospheric conditions and can strongly affect ice nucleation pathways. For the incorporation of ice nucleation by organic aerosol particles into atmospheric models, our results demonstrate a demand for model formalisms that account for the effects of molecular diffusion and not only describe ice nucleation onsets as a function of temperature and relative humidity but also include updraft velocity, particle size and composition.