Air Flow Humidity Research Articles

Simultaneous Online Measurement of H2O and CO2 in the Humid CO2 Adsorption/Desorption Process.

A dew point meter (DP) and an infrared (IR) CO2 analyzer were assembled in a humid CO2 adsorption/desorption system in series for simultaneous online measurements of H2O and CO2, respectively. The humidifier, by using surface-flushing on a saturated brine solution was self-made for the generation of humid air flow. It was found that by this method it became relatively easy to obtain a low H2O content in air flow and that its fluctuation could be reduced compared to the bubbling method. Water calibration for the DP-IR detector is necessary to be conducted for minimizing the measurement error of H2O. It demonstrated that the relative error (RA) for simultaneous online measurements H2O and CO2 in the desorption process is lower than 0.1%. The high RA in the adsorption of H2O is attributed to H2O adsorption on the transfer pipe and amplification of the measurement error. The high accuracy of simultaneous online measurements of H2O and CO2 is promising for investigating their co-adsorption/desorption behaviors, especially for direct CO2 capture from ambient air.

Study of influence of operational parameters on the mass condensate flux in the condenser of seawater greenhouse at Muscat, Oman

The main objective of this theoretical work is to study the influence of the operating parameters such as relative humidity, dry-bulb temperature, seawater temperature, humid air flow rate, and seawater flow rate on fresh water produced by dehumidification of humid air in the condenser of an existing seawater greenhouse that is located in Muscat, Oman. The theoretical results show that the mass condensate rate of the process increases with the augmentation of the relative humidity, the dry-bulb temperature, and the humid air flow rate. However, the seawater temperature and the seawater flow rate have a negative effect. The maximum theoretical mass condensate rate obtained was about 155 kg/h. This result is obtained under the following conditions: for air dry-bulb temperature Tdb = 50°C, relative humidity RH = 97%, inlet seawater temperature Tswin = 28.33°C, humid air flow rate m˙air=23.22kg/s, and seawater flow rate m˙sw=5.87kg/s.

The effects of PEP-1-FK506BP on dry eye disease in a rat model.

As FK506 binding proteins (FK506BPs) are known to play an important role in the regulation of a variety of biological processes related to cell survival, this study was designed to examined the protective effects of FK506 binding protein 12 (FK506BP) on low humidity air flow induced dry eye in a rat model using transduced PEP-1-FK506BP. After the topical application of PEP-1-FK506BP, tear volumes were markedly increased and significant prevention of cornea damage was observed compared with dry eye rats. Further, immunohistochemical analysis demonstrated that PEP-1-FK506BP markedly prevented damage to the cornea, the bulbar conjunctiva, and the palpebral conjunctiva epithelial lining compared with dry eye rats. In addition, caspase-3 and PARP expression levels were found to be decreased. These results demonstrated that topical application of PEP-1-FK506BP significantly ameliorates dry eye injury in an animal model. Thus, we suggest that PEP-1-FK506BP can be developed as a new ophthalmic drop to treat dry eye diseases. [BMB Reports 2015; 48(3): 153-158]

Study on icing evolution rule in process of liquid evaporation-freezing by humidity difference

Desalination by freezing is of great prospect due to its low energy consumption, little pollution, freedom of corrosion and ease of scaling. A novel freezing desalination method driven by humidity difference between air flow and liquid surface is proposed and verified in this paper. In order to reveal its mechanism, an unsteady-state thermodynamics model was established to simulate icing movement on liquid surface according to heat and mass balance. Effects of humidity difference, airflow velocity and mass diffusion coefficient on icing development were analyzed through theory analysis and experiments. It was found that the larger humidity difference and larger airflow velocity had evident effects on the liquid evaporation-freezing. Meanwhile, fast mass diffusion between mediums was also beneficial to this freezing process.

All-Optical Graphene Oxide Humidity Sensors

The optical characteristics of graphene oxide (GO) were explored to design and fabricate a GO-based optical humidity sensor. GO film was coated onto a SU8 polymer channel waveguide using the drop-casting technique. The proposed sensor shows a high TE-mode absorption at 1550 nm. Due to the dependence of the dielectric properties of the GO film on water content, this high TE-mode absorption decreases when the ambient relative humidity increases. The proposed sensor shows a rapid response (<1 s) to periodically interrupted humid air flow. The transmission of the proposed sensor shows a linear response of 0.553 dB/% RH in the range of 60% to 100% RH.

Effect of Emissivity on the Heat and Mass Transfer of Humid Air in a Cavity Filled with Solid Obstacles

The work reported here is a 2D numerical study on the buoyancy-driven low-speed turbulent flow of humid air inside a rectangular cavity partially filled with solid cylindrical objects for a Rayleigh number of 1.45 × 109. Variations of Nusselt number, buoyancy flux, vapor mass fraction, and turbulence viscosity ratio are presented for various emissivity values of wall surfaces. It was observed that during the natural convection process, radiation effects are very significant and the air/water vapor combination results in a small increase in heat transfer as compared with the pure natural convection of dry air.

Cloud-Resolving 4D-Var Assimilation of Doppler Wind Lidar Data on a Meso-Gamma-Scale Convective System

Abstract The authors evaluated the effects of assimilating three-dimensional Doppler wind lidar (DWL) data on the forecast of the heavy rainfall event of 5 July 2010 in Japan, produced by an isolated mesoscale convective system (MCS) at a meso-gamma scale in a system consisting of only warm rain clouds. Several impact experiments using the nonhydrostatic four-dimensional variational data assimilation system (NHM-4DVAR) and the Japan Meteorological Agency nonhydrostatic model with a 2-km horizontal grid spacing were conducted in which 1) no observations were assimilated (NODA), 2) radar reflectivity and radial velocity determined by Doppler radar and precipitable water vapor determined by GPS satellite observations were assimilated (CTL), and 3) radial velocity determined by DWL were added to the CTL experiment (LDR) and five data denial and two observational error sensitivity experiments. Although both NODA and CTL simulated an MCS, only LDR captured the intensity, location, and horizontal scale of the observed MCS. Assimilating DWL data improved the wind direction and speed of low-level airflows, thus improving the accuracy of the simulated water vapor flux. The examination of the impacts of specific assimilations and assigned observation errors showed that assimilation of all data types is important for forecasting intense MCSs. The investigation of the MCS structure showed that large amounts of water vapor were supplied to the rainfall event by southerly flow. A midlevel inversion layer led to the production of exclusively liquid water particles in the MCS, and in combination with the humid airflow into the MCS, this inversion layer may be another important factor in its development.

A composite material made of mesoporous siliceous shale impregnated with lithium chloride for an open sorption thermal energy storage system

In this study we developed a composite mesoporous honeycomb element based on Wakkanai siliceous shale (WSS) and lithium chloride (LiCl), to act as a thermal energy storage medium that can directly contact the functional air in an open sorption thermal energy storage system. The mesopores of the WSS were filled with LiCl to improve its sorption capability as a new sorption thermal energy storage material. The honeycomb thermal energy storage element impregnated with 9.6wt% LiCl was installed in the developed open sorption thermal energy storage experimental setup. The experimental results showed that this impregnated honeycomb element could be regenerated at a lower regeneration temperature, even at 60°C, and also exhibited high volumetric heat storage density. Furthermore, at a certain regeneration temperature, the element impregnated with 9.6wt% LiCl supplied air with a relatively constant high outlet air temperature compared to the element filled with 22.4wt% CaCl2 under the same inlet air conditions in the sorption process, and the proposed element was less affected by the humid air flow rate. The sorption rate was observed to significantly affect the outlet air temperature during the sorption process. We confirmed that the developed composite material filled with LiCl exhibited good stability, boosting the possibility of its long-term use.

Thermal behavior of open cell aluminum foams in forced air: Experimental analysis

This paper deals with the study of thermal and fluid dynamics properties of the open cell metal foams. A thermo-fluid dynamic analysis of three different types of aluminum alloy foams, 5, 10 and 20 pores per inch (PPI) was carried out by using a novel ad hoc built instrumentation. In particular, it has been investigated the Heat Transfer Coefficient (HTC*) and the Pressure Drop (PD) under a flow of forced humid air. The influence of the main parameters, temperature of the metal foam and speed of humid air, both on the HTC* and on the PD was examined. Design of experiments (DOE) approach was used as support to interpret the experimental findings and the physical phenomena involved in HTC* and in PD, between foams and air. The analysis permitted to detect the effects of the operational parameters, foam pore size, air flux and temperature on the HTC* and on the PD.

Meteorological impacts of sea-surface temperature associated with the humid airflow from Tropical Cyclone Talas (2011)

Abstract. This paper examines meteorological impacts of sea-surface temperature (SST) in the presence of the humid airflow from Tropical Cyclone Talas (2011). To investigate the influence of the SST on the severe weather in and around Japan, sensitivity simulations were conducted using six SST data products covering a period of 7 days. The upward sea-surface latent heat flux that accumulated over the 7-day period was high around the Kuroshio during the slow passage of the tropical cyclone. Large differences were found among the individual SST products around the southern coast of Japan. The coastal warm SST anomaly of ~ 1.5 °C enhanced the surface upward latent heat fluxes (by 60 to 80%), surface southeasterly winds (by 6 to 8%), and surface water mixing ratios (by 4%) over the coastal sea area. The enhanced latent heat flux resulting from the coastal SST anomaly contributed to the further enhancement of the latent heat flux itself via a positive feedback with the amplified surface horizontal wind. The SST anomalies produced an anomaly in 7-day precipitation (ca. 40 mm) along the mountainsides and over a coastal area where the surface wind anomaly was locally large. Thus, coastal SST error is important in the atmospheric simulation of accumulated evaporation and precipitation associated with tropical cyclones making landfall.

Relationship between North Pacific Oscillation in May and Drought/Flood in Summer in North China

The relationship between the North Pacific Oscillation( NPO) in May and the summer drought /flood in North China was analysed using the NCEP /NCAR month by month reanalysis data from 1948 to 2011 including sea level pressure,500 hPa geopotential height,specific humidity( 8 layers) and wind field( 8 layers). The North Pacific Oscillation Index( NPOI) which reflects the changes of the sea level pressure in North Pacific was calculated firstly. Then the correlation coefficient between NPOI and Palmer Drought Severity Index( PDSI)which represents the situation of summer drought /flood in North China from 1960 to 2011 was also calculated.The results show that there is a positive correlation between NPO and summer drought /flood in North China.When in positive NPOI years,PDSI in summer is higher than normal,and North China has more summer floods; otherwise,in negative NPOI years,PDSI in summer is lower than normal,and North China has more summer droughts. In order to explain the positive correlation between NPO and summer drought /flood in North China,wind vector field on 850 hPa and geopotential height field on 500 hPa were composite analysed,respectively,and compare the different intensity,area and position of western boundary of Western Pacific Subtropical High( WPSH) when NPO is in different strength( weak and strong). The possible circulation mechanism is that when in positive( negative) NPOI years,on lower layer( 850 hPa wind field),the common action of anti-cyclonic( cyclonic) in Ural Mountains,the cyclone( anti-cyclonic) of Lake Baikal,and the anti-cyclonic( cyclonic) anomaly circulation in West Pacific have strengthened( weakened) the convergence of south-west warm and humid air flows of low layer in North China region. And also,when in positive( negative) NPOI years,500 hPa geopotential height anomaly shows ‘+-+'( ‘-+-') wave train,and WPSH is stronger( weaker) shifting northwest( southeast) than normal years,cold and warm air activities make more( less) rainfall in North China.Vertically intergraded moisture fluxes was calculated,in order to show water transportation of summer drought /flood in North China and study the relationship between NPO in May and sea surface temperature in winter by using composition method. In the difference of vertically intergraded moisture fluxes field in summer,the moisture transport from the Arabian Sea and Bay of Bengal and the West Pacific make North China the positive anomaly of water vapor moisture,so there is more rainfall in North China; In divergence field,the water vapor divergence is negative in North China,so it is moisture sink and there is more rain. And also the Arabian Sea,Bay of Bengal,the south of Indo-China Peninsula to the South China Sea and the Western Pacific are the water vapor divergence centers,which are important vapor source for North China. The SST in winter in Pacific Ocean has forcing role on NPO in May,which influences summer drought /flood in North China.

Temporal evolution characteristics of an annular-mode gliding arc discharge in a vortex flow

An annular-mode gliding arc discharge powered by a 50 Hz alternating current (ac) supply was studied in a vortex flow of dry and humid air. Its temporal evolution characteristics were investigated by electrical measurement, temporally resolved imaging, and temporally resolved optical emission spectroscopic measurements. Three discharge stages of arc-ignition, arc-gliding, and arc-extinction were clearly observed in each half-cycle of the discharge. During the arc-gliding stage, the intensity of light emission from the arc root at the cathode was remarkably higher than that at other areas. The spectral intensity of N2(C3Πu−B3Πg) during the arc-ignition stage was much higher than that during the arc-gliding stage, which was contrary to the temporal evolutions of spectral intensities for N2+(B2Σu+−X2Σg+) and OH(A2Σ+−X2Πi). Temporally resolved vibrational and rotational temperatures of N2 were also presented and decreased with increasing the water vapor content.

Estimation of a Nusselt Correlations for Numerical Prediction of Frost Thickness Growth over a Cold Cylinder

This paper evaluates numerically some of the parameters involved in modeling the process of frost formation over a cold cylinder surface subject to the flow of humid air. Was utilized for numerical predictions the empirical Nusselt correlation from the literature, obtained in experimental studies on frost formation phenomena of frost grow over a cold cylinder surface. To predict frosting process a numerical solution was utilized, and a new correlation for Nusselt number based on the experimental correlation of Kim was estimated. For the new Nusselt correlation an optimization method that adjusts the numerical solution of modeling the frost formation process with experimental results of the frost layer thickness was used. The calculation procedure allows the estimation of the parameter K of equation. The modeling process was validated by comparison with available experimental data.

Analysis of the performance of the evaporator of automotive air conditioning system

The purpose of this research was to establish a theoretical model for the evaporator of automotive air conditioning system and conducting simulations to evaluate the effect of operation parameters, environmental conditions, and design parameters on the performance of evaporator. An automotive air conditioning system primarily consists of four components: the compressor, the condenser, the refrigerant controller, and the evaporator. The refrigerant flow in the evaporator can be divided into two regions: the evaporating region and the superheat region. The refrigerant in the first region is a two-phase flow, while the refrigerant in the latter region is in the state of superheated vapor. The air flowing through the interior of the evaporator can also be divided into two zones: the unsaturated zone and the saturated zone. Water vapor is condensed in the saturated zone while in the unsaturated zone, no water condenses. Because the refrigerant flow and the airflow are perpendicular to each other, the distribution of refrigerant in the evaporating region and the superheat region does not coincide with the distribution of air in the unsaturated zone and the saturated zone. This study examines the effects of different design parameters, environmental conditions and operating parameters on the cooling capacity and superheat of an air conditioning system. Design parameters include the length of the refrigerant channel, the length of the air channel, and the thickness of the fins. Environmental conditions include the air inlet temperature and absolute humidity. Operation conditions include the refrigerant inlet enthalpy, inlet air flow rate, and refrigerant mass flow rate. Results of simulation demonstrated that fins with 50 micron meters width has the greatest cooling capacity for identical outer dimensions; thicker or thinner fins only decreased cooling capacity. Under different outer dimensions, longer refrigerant tubes and air channels created a greater cooling capacity. However, the increase in cooling capacity becomes less and less if the refrigerant flow was fixed because the heat transfer capability of the gaseous refrigerant was limited. In this study, an increase of 19% in cooling capacity can be reached as the length of refrigerant channels was increased, and the increased length of the air channels can promote the cooling capacity by 22%. Besides, it was found in this study that a decrease in the refrigerant inlet enthalpy, the inlet air flow rate, the air inlet temperature, and the inlet absolute humidity, or an increase in the refrigerant mass flow rate, would extend the superheat region and decrease the refrigerant’s superheat. It was also found that the cooling capacity of air conditioners is extremely sensitive to changes in the refrigerant mass flow rate and the inlet enthalpy, and variations more than 50% were found in the operating ranges examined in this study. However, changes in the inlet temperature, absolute humidity, and inlet air flow rate only resulted in variations between 10% and 20% in the examined ranges of conditions. Finally, a correlation among these variables and the simulated cooling capacity was obtained in this study, enabling the relevant researchers to evaluate automotive air conditioning performance under different environmental conditions and operation parameters more easily.

COMPARISON OF AIR DISTRIBUTION SYSTEMS IN ICE RINK ARENA VENTILATION

The paper presents the requirements and functions of ventilation in ice rink arenas and discusses difficulties and problems of ventilation in such objects. Particular attention has been paid to two types of inside used air distribution systems – traditional-integrated and modern-separated where the functions of tribune ventilation and dehumidification of the air over the ice surface were separated. The flow of humid air and heat in the designed hall was modelled numerically using the ANSYS CFX code based on computational fluid dynamics (CFD) technique. Air distribution systems in the ice rink arena were compared based on the results of numerical calculations.

흡착과 탈착 과정 동안 제습 로터의 열/물질 전달

흡착식 제습기에 적용되는 제습 로터는 높은 제습 성능을 달성키 위해, 흡수율이 높은 재질로 구성된 수많은 미세 채널을 포함하고 있다. 본 연구에서는 습공기 흐름에 의해 나타나는 제습 로터 내부의 반복적인 흡착/탈착 과정에 대한 수치해석 결과를 소개한다. 수치해석의 정확도와 효율성을 고려하여 흡습층 내부에서는 표면 확산(surface diffusion)만을 고려하여 해석을 수행하였다. 해석결과는 이전의 연구와 비교하였고, 온도에 대한 비교 오차는 약 2%이하인 점을 감안하여 해석결과가 매우 잘 일치하는 것을 확인하였다. 단일 채널 내부에서 유동층 (flow layer)과 흡습층 (desiccant layer) 간 열/물질전달 연계 해석을 통하여 채널 내부의 수증기 분율, 흡수된 물 분율과 온도 등에 대한 시간 및 공간적 변화를 나타내었다.

Decontamination of a Hospital Room Using Gaseous Chlorine Dioxide: Bacillus anthracis, Francisella tularensis, and Yersinia pestis

This study assessed the efficacy of gaseous chlorine dioxide for inactivation of Bacillus anthracis, Francisella tularensis, and Yersinia pestis in a hospital patient care suite. Spore and vegetative cells of Bacillus anthracis Sterne 34F2, spores of Bacillus atrophaeus ATCC 9372 and vegetative cells of both Francisella tularensis ATCC 6223 and Yersinia pestis A1122 were exposed to gaseous chlorine dioxide in a patient care suite. Organism inactivation was then assessed by log reduction in viable organisms postexposure to chlorine dioxide gas compared to non-exposed control organism. Hospital room decontamination protocols utilizing chlorine dioxide gas concentrations of 377 to 385 ppm maintained to exposures of 767 ppm-hours with 65% relative humidity consistently achieved complete inactivation of B. anthracis and B. atrophaeus spores, as well as vegetative cells of B. anthracis, F. tularensis, and Y. pestis. Decrease in exposure (ppm-hours) and relative humidity (<65%) or restricting airflow reduced inactivation but achieved >8 log reductions in organisms. Up to 10-log reductions were achieved in a hospital room with limited impact on adjacent areas, indicating chlorine dioxide concentrations needed for decontamination of highly concentrated (>6 logs) organisms can be achieved throughout a hospital room. This study translates laboratory chlorine dioxide fumigation studies applied in a complex clinical environment.

A rigorous analysis of simultaneous heat and mass transfer in the pasta drying process

This study presents a two dimensional analysis of coupled heat and mass transfer during the process of pasta drying. Velocity and temperature distributions of air flowing around the pasta are predicted in steady state condition. Using these profiles and the similarity between heat and mass boundary layers, local convective heat and mass transfer coefficients were determined on different points of pasta surface. By employing these values, the solution of coupled heat and mass transfer equations within the pasta object in unsteady state condition was obtained. Furthermore the effects of operating conditions such as velocity, temperature and relative humidity of air flow on drying rate of pasta were studied. Sensitivity analysis results show that the effects of air temperature and relative humidity on the rate of drying are more important than the effect of air velocity. Finally, the results obtained from this analysis were compared with the experimental data reported in the literatures and a good agreement was observed while, no adjustable parameter is used in the presented model.

Honeycomb membranes prepared from 3-O-amino acid functionalized cellulose derivatives

The development of value-added wood-derived polymer products is of significant importance. Of particular interest is the synthesis of advanced bioactive cellulosic materials. In the present research, novel cellulosic honeycomb films are reported. Cellulose was reacted with dimethylthexylsilyl chloride to form regioselective 2,6-di-O-thexyldimethylsilyl cellulose followed by substitution of the C3 with functionalized poly(ethylene glycol) (PEG). The free end of the PEG side chains of the regioselective 3-O-poly(ethylene glycol)–2,6-di-O-thexyldimethylsilyl cellulose served as an attachment point for bioactive molecules. As an example, Fmoc–Gly–OH was linked to the free end of PEG to produce 3-O-Fmoc–Gly–poly(ethylene glycol)–2,6-di-O-thexyldimethylsilyl cellulose. Honeycomb films were produced through film casting under a humid airflow. AFM analysis revealed the directed self-assembly of the 3-O-Fmoc–Gly–poly(ethylene glycol)–2,6-di-O-thexyldimethylsilyl cellulose wherein the pendent 3-O-Fmoc–Gly–poly(ethylene glycol) groups allocated preferentially around the edges of the honeycomb pores.

Combustion Rate of Solid Carbon in the Axisymmetric Stagnation Flowfield Established over a Sphere and/or a Flat Plate

Carbon combustion in the forward stagnation flowfield has been examined through experimental comparisons, by conducting aerothermochemical analyses, with the surface C-O2and C-CO2reactions and the gas-phase CO-O2reaction taken into account. By virtue of the generalized species-enthalpy coupling functions, close coupling of those reactions has been elucidated. Explicit combustion-rate expressions by use of the transfer number in terms of the natural logarithmic term, just like that for droplet combustion, have further been obtained for the combustion response in the limiting situations. It has been confirmed that before the establishment of CO flame, the combustion rate can fairly be represented by the expression in the frozen mode, that after its establishment by the expression in the flame-attached or flame-detached modes, and that the critical condition derived by the asymptotics can fairly predict the surface temperature for its establishment. The formulation has further been extended to include the surface C-H2O and gas-phase H2-O2reactions additionally, so as to evaluate the combustion rate in humid airflow. Since those expressions are explicit and have fair accuracy, they are anticipated to make various contributions not only for qualitative/quantitative studies, but also for various aerospace applications, including propulsion with high-energy-density fuels.