Experimental Investigation of Spray Evaporation in Turbulent Flow in Countercurrent Humidifier

The process in the countercurrent humidifier of HAT cycle involves the evaporation of atomized liquids in a turbulent environment. To allow an optimization of such process and provide data for the validation of numerical calculation, the spray evaporation in a countercurrent air stream was studied experimentally. Measurements were taken for different flow parameters, such as airflow rate and liquid flow rate in order to provide reliable data. Phase-Doppler anemometry (PDA) was applied to obtain the spatial change of the droplet size spectrum in the flow field and to measure droplet size-velocity correlations. These local measured profiles of droplet mean velocities, velocity fluctuations and droplet mean diameters were obtained by averaging over all droplet size classes. Moreover, DualPDA signal processing allows accurate determination of the droplet mass flux and local concentration, from which the global evaporation rates could also be determined. These local temperature profiles were measured using the thermocouple and acquired by data acquisition system based on virtual instrument (VI) technology.

Investigation of Inspiratory Circuit Condensation due to Room Temperature in a Heated Humidifier during Mechanical Ventilation

Heating and humidification control during mechanical ventilation is important. Water condensation can occur due to insufficient humidification. Condensation in the breathing circuit can cause various adverse events. In this study, we investigated whether the occurrence of tubing condensation in the breathing circuit could be affected by room temperature using a simulated respiratory circuit with a humidifier. The room temperature was set at 23°C, 25°C, and 27°C, and mechanical ventilation was performed for 8 h. The inspired gas was appropriately heated and humidified according to the manufacturer’s instructions. The weight of the circuit was measured every 2 h at room temperature to estimate the amount of condensation. During the mechanical ventilation, condensation continued to increase at a room temperature of 23°C, but only for the first 2 h at 25°C, and did not occur at 27°C. The room temperature of the indoor environment was one of the factors generating water condensation in the breathing circuit with a humidifier even when a heater wire in the breathing circuit was appropriately operated.

Design Research of a Novel Aftercool-Humidifier Concept for Humid Air Turbine Cycle

Humid air turbine cycle(HAT)has potential of electrical efficiencies comparable to combined cycle,with lower investment cost and NO_(x) emission.The typical heat exchanger network of HAT consists of intercooler(if there is),aftercooler,recuperator,economizer and humidifier,which brings higher efficiency but makes the system more complex.To simplify HAT layout,a novel humidifier concept is proposed by integrating the aftercooler into traditional counter-current humidifier.Based on this concept,a one-dimensional model including pressure drop and exergy calculation is established to distinguish the thermodynamic and hydrodynamic characteristics,and then the structural parameters,such as the number of rows and columns,tube diameter,pitch and type for a micro HAT are identified.The results show that the aftercool-humidifier plays the same role as original aftercooler and humidifier,and can match the in-tube air,out-tube air and water stream well with lower volume.In the case of micro HAT cycle,the volume of heat and mass transfer area can be reduced by 47%compared with traditional design.The major thermal resistance occurred in the convection heat transfer process inside the tube;however,using enhanced tube cannot effectively improve the compactness of device.

Numerical simulation of membrane humidifier with different flow fields for medical application

Medical humidifier is one of the vital instruments for a respiratory patient in hospital,which is used to humidify the required oxygen for respiratory patients.The conventional type of humidifier,bubble humidifier,has some technical problems,including the need to drain condensed water and a lack of accurate control of air or oxygen required by the patient.In contrast,Membrane humidifier has exciting advantages,including the simplicity of the system,the absence of moving parts,very low noise,and the ability to control temperature and humidity.In this study,three configurations,including parallel,cross,and serpentine of a single module of a membrane humidifier according to the person's weight and breathing rate(the range of 10–28 SLPM)are numerically investigated.For validation of numerical models,a membrane humidifier experimental setup test is used.The obtained results indicated that the crossflow configuration for membrane humidifier has a minimum Dew Point Approach Temperature(DPAT)(2<DPAT<5),which confirms that this flow field has better performance than other flow fields.The results show that increasing the volume flow rate increases the DPAT for membrane humidifiers and Water Vapor Temperature Recovery(WVTR).Furthermore,with an increase of 7 L/min of the gas mixture,the relative humidity has decreased by about 30%.This decrease was most outstanding in the cross-flow field and less in the serpentine flow field.

Analysis of the Efficacy of Humidified High-Flow Nasal Oxygen Therapy Combined with Alveolar Lavage in the Treatment of Patients with Severe Pneumonia Complicated with Respiratory Failure

Objective:To analyze the curative effect of humidified high-flow nasal oxygen therapy combined with alveolar lavage in patients with severe pneumonia and respiratory failure.Methods:120 patients with severe pneumonia complicated with respiratory failure admitted to the Third People’s Hospital of Xining from July 2021 to December 2022 were randomly divided into two groups:group A and group B.The patients in group A were given humidified high-flow nasal oxygen therapy combined with alveolar lavage,whereas those in group B were given humidified high-flow nasal oxygen therapy.The treatment efficacy,blood gas analysis results,and differences in inflammatory mediators were compared between the two groups.Results:The curative effect in group A(96.67%)was significantly higher than that in group B(81.67%),P<0.05;the partial pressure of carbon dioxide(PaCO2),partial pressure of oxygen(PaO2),oxygen saturation(SpO2),and Horowitz index(P/F)of group A were significantly better than group B,P<0.05;the interleukin 6(IL-6),tumor necrosis factor alpha(TNF-α),and C-reactive protein(CRP)levels,white blood cell(WBC)count,serum procalcitonin(PCT),and neutrophil(N)percentage of group A were significantly lower than those of group B,P<0.05.Conclusion:For patients with severe pneumonia complicated with respiratory failure,alveolar lavage,on the basis of humidified high-flow oxygen therapy,can inhibit local inflammation,improve blood gas analysis results,promote disease recovery,and improve the clinical treatment effect。

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.

Recent Progress of Aerosol Light-scattering Enhancement Factor Studies in China

Assessment of the radiative forcing of aerosols in models still lacks sufficient input data for aerosol hygroscopicity. The light scattering enhancement factor [ f(RH, λ)] is a crucial parameter for describing aerosol hygroscopic growth properties.In this paper, we provide a survey of f(RH, λ) studies in China for the past seven years, including instrument developments of humidified nephelometers, ambient f(RH, λ) measurements in China, f(RH, λ) parameterization schemes, and f(RH, λ)applications in aerosol measurements. Comparisons of different f(RH, λ) parameterizations are carried out to check their performance in China using field measurement datasets. We also summary the parameterization schemes for predicting f(RH, λ)with aerosol chemical compositions. The recently developed methods to observe other aerosol properties using f(RH, λ)measurements, such as calculating the aerosol hygroscopicity parameter, cloud condensation nuclei number concentration,aerosol liquid water content, and aerosol asymmetry factor, are introduced. Suggestions for further research on f(RH, λ) in China are given.

Numerical Simulation for Roadways in Swelling Rock Under Coupling Function of Water and Ground Pressure

According to the analogical relation in the governing differential equations of the humidity stress field theory and the temperature stress field theory, the problem of solving the humidity stress field was transformed into that of solving the temperature stress field by the change of parameters. As a result, the problem of roadways in swelling rock under the coupling function of water and ground pressure can be solved by the analytical module of temperature stress field in software ANSYS. In the numerical simulation mentioned above, three kinds of supporting, i.e. steel support, bolting support and non support, were taken into account, the pressure distribution and deformation state of roadways with a swelling rock floor under the coupling function of water and ground pressure were analyzed and compared with those in the action of only ground pressure. The research results provides a scientific basis for the deformation control of roadways in swelling rock.

Empirical Model to Calculate the Thermodynamic Wet-Bulb Temperature of Moist Air

An equation model for calculating the adiabatic temperature of the wet-bulb thermometer has been obtained empirical fit through a meteorological database, specificly a trough relative humidity and air temperature. A comparison of the results of calculations with the use of this equation and from meteorological database was made. The model deducted of the comparison is valid for a dry bulb temperature range of 3°C to 35°C and for relative humidity percentage in a range of 7% to 97%. Normalized errors are less than 5.5%. It means a maximum variation of 0.55°C from data. However, this variation from error represents only 3.6% of the data sample. The equation model was satisfactory.

REGRESSION OF HEAT AND MOISTURE EXCHANGE DIAGRAM OF SWISS LUWA AIR WASHER

The thesis has changed the heat and moisture exchange curves of Swiss Luwa air washer into double efficiency formulas which are widely used in our country with a computer, and also worked out the regression formula of heat transfer efficiency(X). This has created favourable condition for us to use computer in our calculation of Luwa air washer.

Proton Exchange Membrane Fuel Cell with Humidifying Zone

Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in the membrane electrode assembly (MEA) of each cell, in which the moisture of the cathode exhaust gas could transfer through the membrane to humidify anode or cathode dry gas. With a simple model, the relative humidity (RH) of the dry air exhaust from a membrane humidifier with 100% RH stream as a counter flow is calculated to be 60.0%, which is very close to the experimental result (62.2%). Fuel cell performances with hydrogen humidifying, air humidifying and no humidifying are compared at 50, 60 and 70°C and the results indicate that humidifying is necessary and the novel design with humidifying zone in MEA is effective to humidify dry reactants. The hydrogen humidifying shows better performance in short term, while water recovered is limited and the stability is not as good as air humidifying. It is recommended that both air and hydrogen should be humidified with proper design of the humidifying zones in MEA and plates.

Numerical Simulation and Experimental Studies of Air Treatment Process with Water Spray of One Row Counter Flow

The present work is focused on heat and mass transfer in a direct evaporative air cooler of one row counter flow spray. Models of the two-phase flow in such a air treatment system have been developed. The fields of temperature and relative humidity in spray chamber, as well as the trajectories of sprayed drops have been obtained by numerical method. Experiments aiming at quantifying the system performance and its influence factors have been conducted. It indicates that the increase of air velocity and water/air ratio while the decrease of nozzle density are favorable. The performance of the system of parallel flow spray and counter flow spray have been compared by means of humidifying efficiency. Comparison between numerical simulation and experimental results demonstrate good agreement for outlet air temperature with a maximum error of 8% observed for air relative humidity.

Numerical Simulation and Experimental Studies of Air Treatment Process with Water Spray of One Row Parallel Flow

The main purpose of the present work is to make a further insight into the procedure of heat and mass transfer between water droplets sprayed and air stream in a direct evaporative air cooler used in air-conditioning system in textile mills. The thermodynamic models of the two-phase flow in such a air treatment system have been developed for one row parallel flow spray.The fields of temperature and relative humidity in spraylchamber, as well as the trajectories of sprayed drops have been obtained by calculation. A series of experiment aiming at quantifying the system performance and its influence factors have been conducted. It indicates that the increases of air velocity and water/air ratio while the decrease of nozzle density are favorable. Finally, the comparison between numerical simulation and experimental results have been carried out. Good agreements have been found for outlet air temperaturewhile a maximum error of 10% has been observed for air relative humidity.

Humidifying Effect of Riparian Wetland Park of Shijiazhuang, Hebei Province in Autumn

As an important part of urban green space system, wetland parks have good ecological environment and various landscape resources, which play an irreplaceable role in adjusting the climate, beautifying the environment and maintaining regional ecological balance. Therefore, research on humidifying effect of wetland park is of great significance. Air humidity below the height of 1.5 m above various underlying surfaces was measured in Taiping Riparian Wetland Park of Shijiazhuang. Monitoring time was selected in October 10–12, 2012 and six days among September and October, 2013 which were sunny days without wind(or the speed of wind less than 0.2 m/s). By analyzing the basic distribution regularity of humidity from horizontal and vertical directions at different times in autumn days, humidifying effect of various types of plants could be summarized from the sampled data. The humidifying effect of arbor-grasses can strengthen with the increase of temperature. The humidifying effect is the strongest at 10:00–14:00, then, it weakens after noon and the reduction rate tends to be smaller. Second, the humidity above the height of 0.2 m changes at a small scale and is much lower than that close to ground, which reveals great effect of ground cover plants and soil moisture. According to the monitoring data below the height of 1.5 m, the humidifying effect of shrubs is stronger than that of arbor-grasses. Last, the humidifying effect of surfaces with different land covers from strong to weak are shrubs, arbor-grasses, river. The rational allocation on various types of wetlands with a wide variety of structures can improve the atmospheric environment more effectively.

Humidifying Effect of Green Space during Spring in Yuxi Park of Shijiazhuang City of China

As one of the important parts of urban ecosystem, urban green space plays an irreplaceable role in maintaining the balance of carbon and oxygen, absorbing the pollution and removing dust, killing bacteria, purifying soil and water. To analyze the spatio-temporal changes of humidifying effect of green lands at the spring daytime, the authors monitored the air humidity within 1.8 m high from various underlying surfaces, including arbor-grass lands, shrub lands, herb lands and a cement pavement, from late February to late April in 2015 and 2016, when it was sunny and windless, in the Yuxi park of Shijiazhuang. The results were compared with the monitoring data of a bare land(190 m×120 m) without environmental interventions such as vegetation and water. The results could be summarized as follows:(1) The humidifying effect of green spaces was the weakest at 8:00 a.m. during the late February, whereas it was the strongest at 10:00 a.m.; from late March to late April, the humidifying effect of green spaces strengthened with the increase of air temperature, and the strongest was noted around 12:00-16:00.(2) The humidifying effect of various types of green lands was the strongest close to the ground, and reduced from 0.2 m to 1.8 m. This vertical stratification became apparent after the plants sprouted, the vertical difference of humidifying effect was the most significant in the herb lands, less significant in arbor-grass lands, and least in the shrub lands.(3) Multiple comparison analysis of the humidity data showed that relative humidity of all green lands achieved the significant level(P < 0.05), indicating the strong effect of landscape plants in adjusting atmospheric humidity in spring.(4) The humidifying effect of the artificial lake was more remarkable before the plants sprouted, however, with the rapid growth of plant leaves, theeffect gradually reduced and became even weaker than the effect of vegetation. Although the humidifying effect in spring was weaker than that in summer and autumn, the effect of humidification was more complicated during the growth of green leaves in spring than in summer and autumn. This is useful to construct the theory system of ecological environment effect of green lands in spring, summer and autumn.

Hygrometry behavior during high-flow nasal oxygen therapy and non-invasive mechanical ventilation:A narrative review of bench to clinical studies

Recently,there has been growing interest in knowing the best hygrometry level during high-flow nasal oxygen and non-invasive ventilation(NIV)and its potential influence on the outcome.Various studies have shown that breathing cold and dry air results in excessive water loss by nasal mucosa,reduced mucociliary clearance,in-creased airway resistance,reduced epithelial cell function,increased inflammation,sloughing of tracheal epithe-lium,and submucosal inflammation.With the Coronavirus Disease 2019 pandemic,using high-flow nasal oxygen with a heated humidifier has become an emerging form of non-invasive support among clinicians.However,we cannot always assume stable humidification.Similarly,there are no clear guidelines for using humidification dur-ing NIV,although humidification of inspired gas during invasive ventilation is an accepted standard of care.NIV disturbs the normal physiological system that warms and humidifies inspired gases.If NIV is supplied through an intensive care unit ventilator that utilizes anhydrous gases from compressed wall air and oxygen,the risk of dry-ness increases.In addition,patients with acute respiratory failure tend to breathe through the mouth during NIV,which is a less efficient route than nasal breathing for adding heat and moisture to the inspired gas.Obstructive sleep apnea syndrome is one of the most important indications for chronic use of NIV at home.Available data suggest that up to 60%of patients with obstructive sleep apnea syndrome who use continuous positive airway pressure therapy experience nasal congestion and dryness of the mouth and nose.Therefore,humidifying the inspired gas in NIV may be essential for patient comfort and compliance with treatment.We aimed to review the available bench and clinical studies that addressed the utility of hygrometry in NIV and nasal high-flow oxygen and discuss the technical limitations of different humidification systems for both systems.

Experimental Evaluation of a Multistage Reciprocating Evaporative Cooler Performance for Varied Climatic Conditions

Current system focuses on design&construction of a multistage reciprocating evaporative cooling test rig.Four packings that are used will undergo the reciprocating action,powered by the cam follower mechanism maintained at an actual rotation speed.Inlet dry bulb temperature&humidity values are varied to replicate the varying climatic conditions,and the output parameters such as cooling load,evaporation rate(ER),humidification efficiency(HE),coefficient of performance(COP)are obtained.Output results showed that as inlet humidity raises,the performance of system drops.With the rise in the camshaft speed or packing velocity,there is an upsurge in the performance until a cam speed of 10 r/min or packing velocity of 0.083 m/s and with further increases in the value,overall performance drops.The system gave a maximum COP,ER,and HE equal to 3.80,73.87%,and 0.53 g/kg respectively.A rise in the inlet air temperature yielded a maximum change in dry bulb temperature of 8.2℃.Overall,results indicated that evaporative cooling is more effective in arid climates than the cold and humid climates.Air quality test is performed to measure CO_(2),Total Volatile Organic Compound(TVOC),and Formaldehyde(HCHO),and it is found that humidified air entering the defined space is of excellent quality.

Application of Taguchi Method for the Optimization of System Parameters of Centrifugal Evaporative Air Cooler

A new evaporative cooling system based on the action of centrifugal forces is proposed.Such systems are suitable for cooling large air volumes in tropical climates.Effects of geometrical and operational parameters on system performance are optimized using Taguchi method.It is observed that disc speed,air flow rate and water flow rate are found to have major influence on system performance and other parameter,viz.,disc diameter,pin geometry,evaporation chamber length and orientation of pin have less influence.

An Experimental Study on the Motion of Droplets in Flue Gas Humidification Activator with Pulse Laser Sheet Photography

In this paper a technique is introduced on visualization of emulsified droplets in gas stream by pulse laser sheet photography. By this technique fairly clear photographs of the concentration and velocity profiles of water droplets in an activation reactor were obtained. The results of the study show that with a venturi tube installed in the activator, the distribution of the droplets is more uniform than without it; the uniformity of the distribution of the droplets can improve the efficiency of the activation of the sorbent particles in the reactor. The picture of the collision of the droplets was obtained in the experiment, which could be used as basis for the study of the mechanism of humidified activation process. The results of the experimental study of the deposition of the droplets on the reactor walls is also described and discussed.

Effects of vegetation restoration on local microclimate on the Loess Plateau

With the implementation of the Grain for Green Project,vegetation cover has experienced great changes throughout the Loess Plateau(LP).These changes substantially influence the intensity of evapotranspiration(ET),thereby regulating the local microclimate.In this study,we estimated ET based on the Penman-Monteith(PM)method and Priestley-Taylor Jet Propulsion Laboratory(PT-JPL)model and quantitatively estimated the mass of water vapor and heat absorption on the LP.We analyzed the regulatory effect of vegetation restoration on local microclimate from 2000 to 2015 and found the following:(1)Both the leaf area index(LAI)value and actual ET increased significantly across the region during the study period,and there was a significant positive correlation between them in spatial patterns and temporal trends.(2)Vegetation regulated the local microclimate through ET,which increased the absolute humidity by 2.76-3.29 g m^(-3),increased the relative humidity by 15.43%-19.31%and reduced the temperature by 5.38-6.43℃per day from June to September.(3)The cooling and humidifying effects of vegetation were also affected by the temperature on the LP.(4)Correlation analysis showed that LAI was significantly correlated with temperature at the monthly scale,and the response of vegetation growth to temperature had no time-lag effect.This paper presents new insights into quantitatively assessing the regulatory effect of vegetation on the local microclimate through ET and helps to objectively evaluate the ecological effects of the Grain for Green Project on the LP.