Flowing Air Stream Research Articles

Continuous quantitative analysis of low concentrations of tributyl phosphate (TBP) vapors in flowing air streams.

A quantitative analytical technique is described for measuring low concentrations of airborne tributyl phosphate (TBP) vapors. This technique used a modified Meloy PA460 continuous phosphorus gas analyzer. Concentrations of TBP as low as 0.12 mg/m3 were detected. A procedure for calibration of this instrument using TBP vapor is also detailed.

Gas absorption by a liquid layer flowing on the wall of a pipe

AbstractA method is presented for predicting absorption rates for liquid layers flowing along a wall. It is based on results presently available in the literature as well as on the results of studies we recently carried out on the rate of oxygen absorption from a flowing air stream into water layers on the bottom of a horizontal enclosed channel and on the inside of a vertical pipe. Absorption measurements can be interpreted by assuming that the process is controlled by eddies whose length and velocity are characterized by bulk turbulence properties and that in a region of thickness δ close to the interface the turbulence is dampened by viscosity.

Comparison of porous copolymers and related adsorbents for the stripping of low molecular weight compounds from a flowing air stream

Comparison of porous copolymers and related adsorbents for the stripping of low molecular weight compounds from a flowing air stream

Periodic heat transfer in directly opposed free and forced convection flow

An experimental study of the heat transfer from small circular cylinders placed horizontal to a downward flowing air stream is reported. Based on heat-transfer measurements and flow visualization, a model for directly opposed free and forced convection was developed. Three modes of flow were observed. For very low velocities the free convection, buoyant plume dominates the heat transfer. At a “lower critical” Reynolds number, when the free and forced convections are of the same order of magnitude, a well defined periodic heat transfer was obtained. The periodic heat transfer was due to the build-up of the buoyant forces to a magnitude where they overcame the downward force of the air flow. At an “upper critical” Reynolds number the periodic heat transfer abruptly ceases. For velocities greater than the upper critical limit the forces due to the air flow dominate. A potential like, laminar sheet forms, as a shroud around the thermal layer of the hot cylinder. The average heat transfer from the cylinder decreases with increasing Reynolds number for both the case of dominant free convection and the periodic heat-transfer regime. The minimum value of the heat transfer occurred at the upper critical Reynolds number.

Minimum ignition energies in flowing kerosine-air mixtures

Measurements of minimum ignition energy were carried out on kerosine sprays injected into a flowing air stream under conditions of atmospheric pressure and temperature. All the measurements were performed using optimum values of spark duration and with the spark gap adjusted to slightly exceed the quenching distance. Tests were carried out at air velocities up to 50 m/sec on five simplex swirl atomizers designed to produce fuel drops ranging in Sauter Mean Diameter (SMD) from 30 to 100 μm. Ignition was accomplished using capacitance sparks whose energy level could be varied in steps from 3 to 130 mJ. The results obtained clearly demonstrate that by far the most important factor influencing minimum energy is fuel drop size. Ignition performance is improved by increase in spark energy, but very large additional amounts of energy are needed to compensate for even a slight deterioration in atomization quality. It is shown that, for any given atomizer, an increase in velocity can actually improve the weak ignition limit, due to the beneficial effect of velocity on atomization quality. If, however, the fuel drop size is maintained constant, then increase in air velocity has a detrimental effect on the weak ignition limit, in agreement with results obtained on gaseous mixtures.

Evaporation characteristics of kerosine sprays injected into a flowing air stream

An experimental investigation was conducted on the evaporation characteristics of aviation kerosine fuel sprays when injected into flowing airstreams at atmospheric pressure. A continuous sampling probe technique was used to determine the rate of spray evaporation. The fuel was injected in a downstream direction from a series of swirl atomizers which were located in turn at the centre of a circular duct of constant cross-sectional area. Evaporation characteristics were determined at distances of 0.15 to 0.45m from the atomizer. Inlet air temperatures and velocities ranged from 288 to 500°K and 24.5 to 42.5 m/s respectively. Analysis of the results obtained led to the following empirical expression for the rate of fuel evaporation:- N 100−N =3.37×10 −6 T a 1000 4.32 V a 100 1.71 δP f 0.56 FN −4.32 L 1.57

WATER TEMPERATURE VARIATIONS WITHIN A MAJOR RIVER SYSTEM

This paper examines the relationships between river water temperature, air temperature and stream flow measured continuously for one year at four sites along the main stream of the river Tees in northern England. Maximum and minimum river temperatures were found to correlate fairly closely with equivalent air temperatures at each site, but some emphasis was placed on the effects of hydrological factors on water temperature variations within the 818 km2 basin. The range of water temperature fluctuations was shown to increase upstream and the highest river maxima were also recorded in the upper reaches of the river, owing to the relatively low volume of discharge. On a shorter time scale, stream flow was also found to exert an important influence on river temperature during snowmelt and peak flow events arising from storm rainfall. A multiple regression analysis indicated that air temperature and stream flow together accounted for up to 85 % of the variation of daily maximum and minimum river temperatures in summer.

Decomposition in Soil of Waste Cooking Oils Used in Potato Processing

AbstractCooking oils used in potato processing are sometimes wasted in small quantities into the effluent that goes to land disposal. To determine the effect of this oil on land, palm and soybean oils were added to Portneuf silt loam at rates of 0.1, 0.5, 1.0, and 5.0 g oil in 100 g soil (2.2, 11.2, 22.4, and 112 metric tons/ha, respectively). Nitrogen was added and the mixtures were incubated at constant temperature in a CO2‐free continuously flowing air stream. Evolved CO2 was scrubbed from the air stream and decomposition calculated. Both oils decomposed at the same rate at each application rate. Maximum weekly decomposition was approximately 8 and 2.5 metric tons/ha for the 112 and 11.2 metric ton‐applications, respectively. There was no evidence for toxicity to the decomposition systems with the high application of oil and no evidence that difficulty would develop with land disposal of wastes containing these edible cooking oils.

Ignition of Kerosine Fuel Sprays in a Flowing Air Stream

Abstract The ignition of kerosine fuel sprays in a flowing air stream was studied experimentally. Ignition was accomplished using electrical sparks whose energy level could be varied in steps between 19.3 and 130 millijoules. Tests were carried out at air velocities up to 46 metres/second on five simplex swirl atomizers designed to produce fuel drops ranging from 30 to 120 microns in diameter. The results obtained show that minimum ignition energy is strongly dependent on both air velocity and fuel drop size. Their implication to the designer of combustion equipment is that significant reductions in the size and weight of ignition systems could be achieved by improvements in fuel atomization and by local reduction of air velocity in the ignition zone.

Increasing efficiency

On take‐off at sea level conditions, the burner section of the JT9D‐7 and‐15 engines reaches 2,350°F. In the Boeing 747 and McDonnell Douglas DC‐10, developing 45,500lb of thrust, the turbine blades need to be kept at some 500° cooler at 1,850°F, to preserve the metal. Two per cent of the total engine airflow streams at a rate of 51b/scc through 2,900 needle thin holes which have to be bored in the baffles.

Wind-generated waves in thin liquid films with soluble contaminant

Craik (1968) has previously examined the stability of horizontal liquid films when an air stream flows over the liquid surface and when the surface is contaminated by an insoluble surface-active agent. The present theoretical work extends this investigation to examine the role of soluble surface-active agents for cases where the liquid Reynolds number is small. This role is found to be a rather complex one which, under suitable conditions, may be either stabilizing or destabilizing.Related experimental work is described which yields results in qualitative agreement with the theoretical analysis.

End effects on interphase heat and mass transfer in a cubically packed bed of spheres

AbstractHeat (and mass) transfer data were obtained for the constant rate evaporation of water from two layers of porous spheres in simple cubic array (ϵ = 0.4764) to a flowing air stream, over a particle Reynolds number range of 200‐900.It was found that the cumulative effect of adding inert layers of non‐porous spheres at the entrance and exit was to lower (rather than raise, as in the case of randomly packed beds) the extent of heat and mass transfer between the active spheres and the fluid, the minimum number of inert layers required to eliminate end effects being three at the entrance and two at the exit. The specific effect of adding only one inert layer to the entrance, with none at the exit, was to raise somewhat the extent of heat and mass transfer. Interpretations are offered for these trends.The simple cubic assemblage showed substantially lower values of the heat (and mass) transfer factors than those of randomly packed beds.

Blunt body flow of a viscous radiating gas

THE results of a number of papers D-41 show that in the calculation of the blunt body flow of a hypersonic air stream taking radiation into account, it is necessary to take into consideration the radiation cooling of the shock layer, the absorption of energy and the dependence of the absorption coefficient not only on the temperature and density, but also on the frequency. The radiation cooling may lead to the appearance of a significant temperature gradient in the main part of the shock wave, which throws some doubt on possibility of dividing the shock layer into a region of non-viscous flow and a boundary layer. When there is absorption the radiative transfer of energy leads to interaction between the main and boundary flow regions. It is extremely difficult to take account of consideration of these regions of the shock layer, especially if we take into account the complex nature of the dependence of the absorption coefficient of air on the frequency. Therefore, in studying the blunt flow of radiating air taking into account radiation cooling and absorption, it is necessary at the same time to consider the entire flow between the shock wave and the frontal surface of the body.

The Spontaneous Ignition of Hydrocarbon Fuels in a Flowing System

An apparatus is described in which the ignition delays of fuel sprays have been measured over a range of pressures (30–60 atm.), temperatures (770–980°K), and velocities up to 70 ft/s (21 m/s), in a continuously flowing air stream. Experiments have been made over this range of conditions with 21 hydrocarbon fuels and the appropriate values of ignition delay for any given engine or fuel can be interpolated. For the engine designer, equations are recommended relating ignition delay, air pressure, and temperature for a range of commercial fuels from diesel fuel to a premium grade gasoline. Curves are presented indicating the variation of ignition delay with cetane number and octane number, and a relationship between these two parameters has been derived.

Wind-generated waves in contaminated liquid films

A uniform liquid film on a horizontal flat plate may be unstable to small disturbances when an air stream flows over the liquid surface. The stability of such films is examined for cases where the film is contaminated by an insoluble surface-active agent.Two approximate analyses are given, which are applicable to liquid films at moderately large Reynolds numbers and at fairly small Reynolds numbers, respectively. These supplement previous work on uncontaminated films by Miles (1960), Cohen & Hanratty (1965) and Craik (1966).At large liquid Reynolds numbers, the presence of surface contamination enhances stability due to increased dissipation in the viscous layer just within the liquid surface; but, at small liquid Reynolds numbers, there exists a class of disturbances for which surface elasticity may be destabilizing.

Investigation of the hydeodynamic boundary layer on a disk washed by a transverse stream

The results are given of an experimental investigation and of theoretical calculation of the hydrodynamic boundary layer on flat disks washed by transverse flow of an air stream.

A PHYSIOLOGICAL CONSIDERATION ON THE COURSE OF THE NASAL AIR-STREAMS

The Author made experimental studies on the courses of the nasal air-streams using models prep- ared from man, monkeys, dogs, cats, pigs, rabbits and cattles and the following results were obtained. The inspired airstream passes through the nose so as to cover the whole surface of the maxilloturbi nal like flat sheets. In man, the inspired air-stream flows ascending the front upper end of the middle turbinate like wide sheats, and then covers the complete surface of the inferior-turbinate in the form of an arc.Next, the exspired air stream passes through the nose as thick layer filling the whole respiratory area, and exspires out from the nostril in both man and other animals. In man, this thick layer of stream fills all spaces below the middle meatus. These phenomenons can be reasoned that the exspired air is exspired out from an area of greater diameter into one of smaller dimensions. The author concluded that these air stream processes observed from my experiments are most rational and scientific for maintenance of the physiological functions of nasal cavity

Temperature gradients in turbulent gas streams: Effect of viscous dissipation on evaluation of total conductivity

AbstractValues of the total conductivity in a turbulently flowing air stream were originally reported without regard to the effects of viscous dissipation upon the results. By utilizing measurements of the shear taken at the time of the original study, the reported values of total conductivity were corrected for the effect of viscous dissipation. The effect of such dissipation upon the values of total conductivity is the greatest under conditions involving small temperature gradients and high Reynolds numbers.

Solar distillation of salt water in plastic tubes using a flowing air stream

Experiments on the solar distillation of salt water are described in which the blackened water partially fills long horizontal plastic tubes. Air is swept along the surface of the solar-heated water, and the water vapor is removed in a water-cooled condenser. The effect of one or two enclosing tubes and the effect of different types of plastics were studied. The efficiencies of solar distillation were about 20 to 40 per cent, based on hourly performance and on the area of water intercepting the radiation.

An Analog Computer for Studying Heat Transfer During a Thermal Recovery Process

Published in Petroleum Transactions, AIME, Volume 204, 1955, pages 205–212. Abstract A design is presented for an electrical analog computer which can solve non-steady state heat transfer problems in an extensive radial formation containing a moving cylindrical source. The computer is used to simulate a simplified thermal oil recovery process in which heat transfer from a moving, constant temperature source takes place radially by conduction only. Temperature distribution curves are shown for several different assumed modes of travel for the heat source. The data are used to estimate the residual fuel requirements necessary to maintain a self-propagating isothermal front for the particular system being studied. Although the computer is designed to represent an unique system, conversion factors can be adjusted to show the effects of changing the assumed values of system constants, such as thermal conductivity of the formation and temperature of the source isotherm. Examples are given to illustrate the relative influence the assumed values of these variables will have upon the quantity of fuel required to maintain the source. The maximum effect of heat transfer by the flowing air stream is estimated mathematically, and full requirements for this system are shown to be markedly reduced. Inasmuch as the examples discussed refer to a simplified process, the results are not directly applicable to a practical field operation. It is believed, however, that the data illustrate some general trends which are important in thermal recovery processes. Data from laboratory and field experimentation can be used to modify the computer to take into account the influence of heat transfer by various mechanisms, for example, by injected air and by fluids ahead of the hot zone. With such refinements it would be possible to estimate more accurately the limiting values for the rate of travel of the high temperature front and for the required air injection rates. Use of this computer should aid in evaluating the economic feasibility of oil recovery by various thermal processes. It is hoped this paper will stimulate further work by others to help accomplish this objective.