Stream Of Dry Air Research Articles

Measurements of the wake flame behind a sphere via Raman scattering.

An experimental study was made of the structure of the wake flame formed behind a porous sphere from which methane was discharged into a uniform stream of dust-free dry air. The laser Raman scattering technique was applied to measure the temperature and the number density of gaseous molecules in the flame. Flame temperature was determined from the measured results of the Stokes-Raman spectrum of nitrogen molecule which was irradiated by the Argon laser (488 nm). measurements were also made of the flame emission spectroscopy. The results showed that the maximum temperature was observed near the periphery of the visible flame. The ratio of the number densities of oxygen and nitrogen molecules in the central portion of the flame was much lower than the value in the room air. Strong OH emission was observed near the maximum temperature region.

Vapor concentration profile around an evaporating sphere in an air stream.

The laser Rayleigh scattering technique was applied for the time and space resolved measurements of vapor concentration around a sphere of liquid fuel or freon evaporating in a vertically upward free stream of dust-free dry air with uniform velocity and temperature profiles. The Rayleigh signal from a minute volume of vapor air mixture subjected to the monochromatic radiation of a focused argon laser was collected by the optical detection system. A peak in the lateral distribution of the time-averaged vapor concentration was observed at a location off the central axis of the flow in the wake behind the sphere. The longitudinal vapor concentration profile was fairly uniform except in the vicinity of the sphere. A rise in air velocity caused a decrease in the boundary layer thickness while the vapor concentration remained almost unchanged. The vapor concentration increased with an increase in air temperature and volatility of liquid.

Evaporation and pervaporation of a binary mixture from an inert carrier liquid

AbstractBench‐Scale experiments were carried out with the ternary mixture 2‐propanol/water/glycerol. In a cylindrical vessel, the stirred and thermostated liquid was exposed to a preheated and either dry or humidified air stream. The mixture was evaporated either from a free surface or from the surface of a porous plate. On evaporating the mixture from a porous plate into a dry air stream, the less volatile component water escapes preferentially; in the case of evaporation from a free surface, water is retained in the mixture. In the former case, selectivity is liquid diffusion controlled, in the latter, the gas‐side mass transfer and the thermodynamic equilibrium are the controlling mechanisms. On reducing the gas flow rate, the more volatile alcohol evaporates preferentially in both cases; the selectivity is controlled only by thermodynamic equilibrium. Humidification of the air stream with water vapour causes preferential evaporation of the alcohol at an increased rate. Furthermore, instabilities in the liquid boundary layer due to density gradients and surface tension effects may affect the selectivity of evaporation. Experimental results show that the selectivity of evaporation can be manipulated by choosing appropriate evaporation conditions. The theory, which applies the generalized Stefan‐Maxwell equations to diffusion in the liquid, can describe these effects.

Drying of polyvinyl alcohol in a closed-circuit dryer

The sorption isotherm and the drying rate curve represent the basis for the design of a dryer for solvent wetted polyvinyl alcohol (36 wt.% methyl acetate, 62 wt.% methanol, 2 wt.% water). In this study the sorption isotherms of polyvinyl alcohol wetted with a mixture of methyl acetate and methanol were measured at 40, 60 and 80 °C, and the drying rate curves of solvent-wetted polyvinyl alcohol layers 3, 10 and 20 mm in height in a dry air stream (air temperatures 30, 60 and 100 °C, air velocities 0.2 and 1 m s −1) were investigated. The hygroscopic equilibrium moisture content can be determined by means of the sorption isotherm, and the belt area of the dryer by means of the drying rate curves.

Spontaneous ignition of sodium in dry and moist air streams

The spontaneous ignition behavior of liquid sodium was studied experimentally, using the stagnation region of impinging air streams of various humidity, and a unique technique which kept the sodium from reacting until it was heated to a predetermined temperature. It was found that the spontaneous ignition temperature increased with increasing humidity of the air stream, and also that ignition occurred in two distinct stages of surface reaction, and finally a gas phase reaction. The first stage of the surface reaction, which was affected by humidity, was controlled by the rate of the surface reaction, while the second stage was controlled by the oxygen diffusion rate through the boundary layer formed over the sample surface. The ignition mechanism is discussed, and the effect of moisture on the ignition temperature is explained in terms of the formation of “protective” NaOH in the reaction film produced on the sample surface during the ignition process.

Evaporation under an obliquely impinging laminar ducted slot jet — a numerical model

Results of a numerical study of the flow, heat and mass transfer under a semi-confined laminar slot jet are presented for oblique impingement into a crossflowing stream. The specific case studied is that of evaporation of water from the isothermal wet impingement surface into a relatively dry air stream.

An improved and simple method for determining diene conjugation in autoxidized polyunsaturated fatty acids

The autoxidation of linolenic acid was produced at room temperature in a rotating apparatus by passing a stream of dry air over a thin layer of polyunsaturated fatty acid (PUFA). During these experiments, volatile thiobarbituric acid positive product(s), were recovered. The extent of fatty acid autoxidation was measured either (a) by the production of malonaldehyde (MDA) or (b) by the height of the peak at 233 nm of the second derivative spectrum, corresponding to the hidden maximum at 235 nm in the normal absorbance spectra of autoxidized PUFA. The identification of the conjugated double bond structure, arising from the autoxidation of linolenic acid was further confirmed by 1H-NMR spectrometric determinations.

Turnover of Tritiated Water in Calamondin Plants1

Abstract The turnover of water in small fruit-bearing plants of calamondin (Citrus madurensis Loureiro) was studied by following the uptake of tritium-labelled nutrient solution. The turnover was much greater in vegetative tissue than in the fruit. Even after 3 days, the radioactivity of water in the fruit, relative to that in the solution, did not reach 20%, compared with about 60% in the leaf tissue. The radioactivity of water in the pedicel reached 60%, similar to that in leaf tissue. Decay of radioactivity in fruit was considerably slower than in other organs when the plant was transferred from a labelled to a non-labelled solution. The turnover of water in fruit was extremely slow even when transpiration was increased by exposing the entire plant or fruit alone to a stream of dry air. Defoliation of fruit-bearing branches decreased the entry of water into fruit tissues. The availability of water for fruit growth in view of the competition offered by the leaves is discussed.

Klinokinetic and klinotactic humidity reactions of the beetles Hylobius abietis and Tenebrio molitor

ABSTRACT. The effects of spatially uniform but temporally changing air humidity stimuli on the orientation behaviour of the large pine weevil (Hylobius abietis L.) and the flour beetle (Tenebrio molitor L.) were studied in a specially constructed vertical air flow chamber. Moist‐acclimatized but hygronegative pine weevils were exposed for 10 s to a moist air stream (c. 85% R.H.) and then for 10 s to a dry air stream (c. 50% R.H.). The Tenebrio were divided into two groups acclimatized to moist and dry air respectively. For each group the humidity during the initial 5 s in the air stream was the same as during acclimatization, and then changed to the alternative level. In Hylobius the change from moist to dry air caused a decrease in spatial displacement brought about by a decrease in walking speed and an increase in the amount of turning per unit time. In Tenebrio the change from dry to moist air caused a decrease of walking speed and a turning‐back reaction based, presumptively, on idiothetic information about the insect's previous walking direction. The average angle turned during 2 s after the humidity change was 165°. In moist‐adapted beetles the dry air stream caused an identical orthokinetic arrestment, but no klinokinetic or klinotactic reaction. Klinokinesis is redefined as a change in the circular variance of turning angles per unit time, which does not change the mean direction (or directions in cases of multimodal distributions) of the circular distribution. Accordingly, klinotaxis consists of a change in the mean directions) of the circular distribution of angular velocities. In both species the turning frequency was more constant than turning per unit distance, suggesting a temporal control in the nervous system of klinokinetic and klinotactic behaviour.

Capability of Iron(III) Hydroxide Oxides for an NOx Sensor

The utilization of α-FeOOH, γ-FeOOH, and amorphous iron(III) hydroxide for an NOx sensor has been explored. The change in electrial current through the compressed specimen of each sample by injecting gases containing NO of 1-104 ppm was measured at 60°C in a stream of dry air. The current dropped within 10 s by 1% for 7-FeOOH and 4-5% for a FeOOH and amorphous iron (III) hydroxide when exposed to 100 ppm NOx(Fig.3 and 4). The reproducibility of signals at 100 ppm NOx ±10%. The lowest NOx concentration detectable was 1-2 ppm. Almost no effect of coexisting SO, (up to 1: 3 NOx/SO2) was shown on the performances of the γ-FeOOH sensor (Fig.5). The possible use of FeOOH for an NOx sensor is suggested.

Non-destructive measurement of residual adsorption capacity of charcoal filters

A non-destructive method has been developed to measure the residual adsorption capacity (RAC) of charcoal filter beds while in use. A small sample of a weakly adsorbed gas is pulsed as a square wave into the gas stream that passes through the adsorption filter. The effluent pulse is detected by means of an appropriate detector. The RAC of the carbon bed is proportional to the retantion time of the gas. The filter is an adsorption bed that behaves as a gas-solid Chromatograph, and only bare sites, not covered by heavy adsorbate, are available to the pulsed gas. The system chosen was M-11 gas mask canisters containing 2.8 cm × 87 cm 2 ASC Whetlerite charcoal beds loaded to various degrees with highly polar dimethyl methyl phosphonate (DMMP), which simulated a strongly adsorbed pollutant. 10 cm 3 aliquots of non-polar test gases methane and ethane were pulsed into a stream of dry air, at flow velocities of 5.47 l./min (1.05 cm/sec) and bed temperature of 25°C. The retention times of CH 4 dropped from 0.9 min over bare ASC Whetlerite to 0.5 min over carbon 50% saturated with DMMP. Ethane times fell from 24 to 7 min. The accuracy of RAC determination using methane was ± 1.0%. The time required for the test was < l min for methane, < 30 min for ethane.

LOW TEMPERATURE AIR DRYING OF CARROT CUBES

ABSTRACTIndividual frozen carrot cubes were suspended on wires and dried in a stream of low temperature dry air. One of the cubes was suspended on a thermocouple. During drying the weight and temperature of the product and the specific humidity, velocity and temperature of the air were recorded. An analytical model, utilizing the concept of external and internal resistances to the transfer of heat and mass, was developed for the prediction of the drying rate. The experimental data were used to determine a functional relationship between the internal resistances and the fraction of the original moisture remaining in the product. The drying rates predicted were in good agreement with experimental results.

Physiological Adaptations of Aquatic Newts (Notophthalmus viridescens) to a Terrestrial Environment

Aquatic newts (Notophthalmus viridescens) are able to adapt to terrestrial environments in nature. In this study aquatic newts were made to adapt to a simulated terrestrial environment of moist paper towels. Along with the typical morphological changes of tail fin loss and change of the skin from smooth and mucous to rough and dry, a variety of physiological adaptations were observed. When dehydrated in a stream of dry air, aquatic newts lost motor control (the ability to right themselves) after a water loss of only 22% of body weight. Aquatic newts adapted to a simulated terrestrial environment (terrestrial newts) maintained motor control until a water loss of 30% of body weight occurred. During rehydration, dehydrated terrestrial newts regained water five times as fast as dehydrated aquatic newts. Terrestrial newts showed a slightly greater dehydration rate than did the aquatic newts. Both aquatic and terrestrial newts could maintain themselves in sodium and chloride balance in a 1 mM NaCl solution, h...

Thin-layer chromatographic method for the determination of digitoxin in human serum

A specific assay for therapy control purposes and the toxicology of digitoxin is described. Digitoxin is isolated from serum (2 ml) by means of a single extraction with chloroform. Part of the organic phase is evaporated to dryness at 40° in a stream of dry air and the residue is dissolved in a small volume of chloroform. Conventional thin-layer chromatography (TLC) is used for the separation of digitoxin and its metabolites and digoxin. Fluorescence of the spots can be generated by treatment with hydrogen chloride vapour under the influence of a quartz-halogen lamp. Interpolation between two reference standards gives the concentration in the sample. Linearity is observed between 2 and 20 ng. Extensive recovery studies in the therapeutic range of 10–50 ng/nl have been performed. The results showed an overall recovery of 99.1% with a standard deviation of 11.2%. The sensitivity is 1–2 ng of digitoxin when standards are applied on a conventional TLC plate with a small diameter. The time needed for one analysis is about 412 h, the real time of analysis being 212 h; in serial studies, 20–24 determinations could be made daily. Whereas in the descriptions of most methods it is not mentioned whether digitoxin metabolites are co-determined, the present assay separates the digitoxin completely from the other compounds in serum, and thus enables the total fate of digitoxin in relation to the clinical effect to be studied more specifically than by radioimmunoassay.

A mechanically refrigerated gas stream (to -120°C) and some useful accessories

A system for cooling a stream of dry air to −120°C is described. Mechanically refrigerated cooling units are used to maintain the cold baths in which heat exchangers are immersed. Adapters for converting a precession camera to a flat-plate oscillation-rotation camera and for mounting crossed polaroids on the precession camera are described. These devices are particularly useful for examining and aligning crystals grown in situ at low temperatures. They can also be used for aligning crystals on the precession camera even when monochromated radiation is used.

A simple photometric determination of sulphuric acid aerosol

Sulphuric acid aerosol in air may be determined after collection on a filter as equivalent to the amount diaethylamine it absorbs from a stream of dry air to which this reactant has been added in vapour form. This amount may be determined by a simple photometric method. The detection limit is about 0.2 μg m −3, the reproducibility is about 10 per cent. Other acidic particles interfere to an extent in the order of 20 per cent, depending on acid strength and physical state.

Filtration of Airborne Particulates By Gravel Filters: II. Collection Efficiency And Pressure Drop In Filtering Fume

The collection efficiency of gravel layers to remove ammonium chloride fume from dry air streams is initially low, but increases sharply with increasing particulate load W on the gravel. The pressure drop ΔP across the gravel layer is low and changes little with particulate load until it reaches a threshold load W/P , whereupon AP increases abruptly with erratic fluctuations. The effects of gravel size, layer thickness, and air flow velocity upon Δ vs. W, AP vs. W, WP, and the cumulative collection efficiency from zero load to WP are presented. The application of these data for air filtration is also discussed.

Airlicking: Thirsty rats prefer a warm dry airstream to a warm humid airstream

Water-deprived rats were trained to airlick in a chamber containing two drinking tubes through which air of ambient temperature and humidity was pumped. After each rat had learned to airlick and had developed a strong position preference for one of the tubes, the airstream emerging from that tube was heated to 42°C and saturated with humidity. The other airstream was heated to 42°C but its humidity was not increased. All rats developed a strong preference for licking the dry airstream and they maintained this preference throughout many position reversals. It is concluded that evaporative cooling of the orolingual tissues makes an important contribution to the reinforcement obtained from airlicking.

Nitric Oxide Sorption by Calcareous Soils: I. Capacity, Rate, and Sorption Products in Air Dry Soils

AbstractAt room temperature, air dry calcareous soils sorbed from 0.5 to 2% NO by weight within 10 to 15 min from a dry air stream containing 1.6% NO by volume. The sorption capacity increased with 0.4 to 0.7‐th power of NO concentration and the soil specific surface and was independent of the soil acidtitratable basicity. The sorption rate was approximately proportional to the unused portions of the capacity with rate constants ranging from 0.4 to 1 min‐1. Less than 10% of sorbed NO was lost by heating at 105C or a suction of 65 cm Hg for 24 hours. The NO sorbed by the soil was converted to NO‐3.

Change in interfacial tension during mass transfer. III. Surface temperature of water during vaporization

The vaporization of water from a suspended drop in a stream of dry air has been studied by measuring the surface tension and the temperature of the drop during vaporization. The surface temperature, defined as it is in equilibrium with the observed surface tension, coincides with the observed temperature inside the drop, although the latter decreased considerably during vaporization. The rate of vaporization and the heat transfer coefficient from the air to the drop depend on the velocity of the air stream. No effect of sodium dodecylsulfate added to the drop on the rate of vaporization was found. It has been concluded that the rate-determining step of the vaporization in the present system is the diffusion of water in the gas phase.