scholarly journals A Study on Plume Dispersion Characteristics of Two Discrete Plume Stacks for Negative Temperature Gradient Conditions

2021 ◽  
Author(s):  
Hrishikesh Sivanandan ◽  
V. Ratna Kishore ◽  
Mukesh Goel ◽  
Abhishek Asthana
Keyword(s):  
Temperature Gradient ◽  
Vertical Direction ◽  
Negative Temperature ◽  
Atmospheric Temperature ◽  
Plume Dispersion ◽  
Dispersion Characteristics ◽  
Flow Solver ◽  
Lower Temperature ◽  
Two Temperature ◽  
Equal Height

AbstractThe dispersion of air pollutants emitted from industries has been studied ever since the dawn of industrialisation. The present work focuses on investigating the effect of negative atmospheric temperature gradient and the plume stack orientation of two individual equal-height stacks on the vertical rise and dispersion of the plume. The study carried out upon three-stack layout configurations namely inline, 45° and non-inline, separated by an inter-stack distance of 12 times the exit chimney diameter (12 D) and 22 times the exit chimney diameter (22 D) in each case over the two temperature gradients of −0.2 K/100 m and −0.5 K/100 m. The turbulence is modelled using realisable k-ε model, a model used in the FLUENT flow solver. In the case of the inline configuration, the upwind plume shields its downwind counterpart, which in turn allows for higher plume rise at a given temperature gradient. The plume oscillates more in the case of inline than 45° and non-inline cases. Also, for a temperature gradient of −0.5 K/100 m, the plumes oscillate violently in the vertical direction, mainly because, with the initial rise of the plume, cold air from higher altitudes moves down and forms a layer of lower temperature closer to the ground. The present study is important to highlight the plume dispersion characteristics under negative temperature gradient conditions.

scholarly journals Computational study on the mechanism and kinetics for the reaction between HO2 and n-propyl peroxy radical

RSC Advances ◽  
2019 ◽  
Vol 9 (69) ◽  
pp. 40437-40444
Author(s):  
Zhenli Yang ◽  
Xiaoxiao Lin ◽  
Jiacheng Zhou ◽  
Mingfeng Hu ◽  
Yanbo Gai ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Temperature Regime ◽  
Computational Study ◽  
Peroxy Radical ◽  
Negative Temperature ◽  
Mechanism And Kinetics ◽  
Lower Temperature

The negative temperature dependence for the HO2 + n-C3H7O2 reaction in lower temperature regime.

MECHANISM AND KINETICS OF THE CH3CH2C(O)OCH2CH3 + OH REACTION: A THEORETICAL STUDY

2011 ◽  
Vol 10 (05) ◽  
pp. 691-709 ◽  
Author(s):  
CONG HOU ◽  
CHENG-GANG CI ◽  
TONG-YIN JIN ◽  
YONG-XIA WANG ◽  
JING-YAO LIUM
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Negative Temperature ◽  
State Theory ◽  
Measured Temperature ◽  
Temperature Range ◽  
Global Rate ◽  
Abstraction Reaction ◽  
Lower Temperature ◽  
Kinetic Calculations

The hydrogen abstraction reaction of CH 3 CH 2 C(O)OCH 2 CH 3 + OH has been studied theoretically by dual-level direct dynamics method. Six H-abstraction channels were found for this reaction. The required potential energy surface information for the kinetic calculations was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants were calculated by the improved canonical variational transition-state theory with small-curvature tunneling correction (ICVT/SCT) approach in the temperature range of 200–2000 K. It is shown that the "methylene H-abstraction" from the alkoxy end of the ester CH 3 CH 2 C(O)OCH 2 CH 3 is the dominant channel at lower temperature (< 400 K), while the other channels from the acetyl end should be taken into account as the temperature increases and become the competitive ones at higher temperature. The calculated global rate constants are in good agreement with the experimental ones in the measured temperature range and exhibit a negative temperature dependence below 500 K. A four-parameter rate constant expression was fitted from the calculated kinetic data between 200–2000 K.

scholarly journals Study of a temperature gradient metamorphism of snow from 3-D images: time evolution of microstructures, physical properties and their associated anisotropy

2014 ◽  
Vol 8 (6) ◽  
pp. 2255-2274 ◽  
Author(s):  
N. Calonne ◽  
F. Flin ◽  
C. Geindreau ◽  
B. Lesaffre ◽  
S. Rolland du Roscoat
Keyword(s):  
Temperature Gradient ◽  
Physical Properties ◽  
Time Evolution ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Large Set ◽  
Correlation Lengths ◽  
Snow Properties ◽  
Cold Room ◽  
Anisotropy Coefficients

Abstract. We carried out a study to monitor the time evolution of microstructural and physical properties of snow during temperature gradient metamorphism: a snow slab was subjected to a constant temperature gradient in the vertical direction for 3 weeks in a cold room, and regularly sampled in order to obtain a series of three-dimensional (3-D) images using X-ray microtomography. A large set of properties was then computed from this series of 3-D images: density, specific surface area, correlation lengths, mean and Gaussian curvature distributions, air and ice tortuosities, effective thermal conductivity, and intrinsic permeability. Whenever possible, specific attention was paid to assess these properties along the vertical and horizontal directions, and an anisotropy coefficient defined as the ratio of the vertical over the horizontal values was deduced. The time evolution of these properties, as well as their anisotropy coefficients, was investigated, showing the development of a strong anisotropic behavior during the experiment. Most of the computed physical properties of snow were then compared with two analytical estimates (self-consistent estimates and dilute beds of spheroids) based on the snow density, and the size and anisotropy of the microstructure through the correlation lengths. These models, which require only basic microstructural information, offer rather good estimates of the properties and anisotropy coefficients for our experiment without any fitting parameters. Our results highlight the interplay between the microstructure and physical properties, showing that the physical properties of snow subjected to a temperature gradient cannot be described accurately using only isotropic parameters such as the density and require more refined information. Furthermore, this study constitutes a detailed database on the evolution of snow properties under a temperature gradient, which can be used as a guideline and a validation tool for snow metamorphism models at the micro- or macroscale.

Female pheromone and the behaviour of male guppies (Poecilia reticulata) in a temperature gradient

1985 ◽  
Vol 63 (5) ◽  
pp. 1211-1213 ◽  
Author(s):  
P. H. Johansen
Keyword(s):  
Sex Pheromone ◽  
Temperature Gradient ◽  
Poecilia Reticulata ◽  
Chemical Cues ◽  
Water Mixture ◽  
Horizontal Temperature Gradient ◽  
Temperature Preference ◽  
Female Pheromone ◽  
Lower Temperature ◽  
Estradiol 17Β

When the two sexes of the guppy are tested separately in a horizontal temperature gradient apparatus, males show a significantly lower temperature preference (23.5 °C) than females (27.4 °C). However, when the two sexes are tested together, males select the same location as the females. Infusion of female holding water, which contains sex pheromone, results in the attraction of males to the site of infusion, as does the infusion of a water mixture of estradiol-17β, but not estrone, estriol, or testosterone. Temporarily plugging the nares, thereby blocking olfaction, prevents the males from responding to the chemical cues.

Effects of sexual maturation and sex steroid hormone treatment on the temperature preference of the guppy, Poecilia reticulata (Peters)

1980 ◽  
Vol 58 (4) ◽  
pp. 586-588 ◽  
Author(s):  
Peter H. Johansen ◽  
Jennifer A. Cross
Keyword(s):  
Temperature Gradient ◽  
Poecilia Reticulata ◽  
Steroid Hormone ◽  
Hormone Treatment ◽  
Sex Steroid ◽  
Horizontal Temperature Gradient ◽  
Temperature Preference ◽  
Preferred Temperature ◽  
Sex Steroid Hormone ◽  
Lower Temperature

In a horizontal temperature gradient, male guppies prefer a significantly lower temperature (24.5 °C) than females (28.2 °C) or juveniles (28.1 °C). Treatment of juveniles and females with testosterone lowers their preferred temperature to that of males. The reduction in the preferred temperature of testosterone-treated juveniles can occur without the development of male secondary sexual characters. Estrogen treatment of juveniles is without effect, as is treatment of males with estrogen or testosterone. It is postulated that testosterone acts at the level of the hypothalamic thermoregulatory centre.

scholarly journals The isothermal layer of the atmosphere and atmospheric radiation

1909 ◽  
Vol 82 (551) ◽  
pp. 43-70 ◽  
Keyword(s):  
High Pressure ◽  
Temperature Gradient ◽  
Temperature Change ◽  
Atmospheric Temperature ◽  
Atmospheric Radiation ◽  
Average Height ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Temperature Changes ◽  
Isothermal Layer

The investigation of the upper air by means of balloons carrying self-recording instruments, which have furnished values for the atmospheric temperature up to heights between 15 and 20 kilometres, has revealed the existence of an abnormal change in the vertical temperature gradient. After a fairly uniform fall, with increasing altitude, of about 6° C. per kilometre, a height is reached above which the temperature changes very little, sometimes increasing, sometimes diminishing slowly. The phenomenon was first noticed by M. Teisserenc de Bort in a communication to the Société de Physique in June, 1899. He improved his apparatus and made further investigations, in many cases sending up the balloons by night to eliminate any possible insolation effects. He found the average height, at which the change began, to be about 11 kilometres. He discovered also that the height was greater near the centre of high pressure areas than in low pressure areas, the average heights for the two cases being 12-5 and 10 kilometres respectively. More recently he found that the height increased with approach towards the equator and that near the equator, ballons-sondes , ascending to 15 kilometres, had failed to reach this layer if it existed there. He proposed to call this layer, in which little temperature change occurred, the “Isothermal Layer of the Atmosphere,” and the name has been generally accepted.

Development of Localized Deformation in AA 2024-O

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
S. Kweon ◽  
A. J. Beaudoin ◽  
P. Kurath ◽  
M. Li
Keyword(s):  
Temperature Gradient ◽  
Work Hardening ◽  
Mechanical Response ◽  
High Strain ◽  
Strain Rates ◽  
Compression Tests ◽  
Localized Deformation ◽  
Aa 2024 ◽  
Higher Temperature ◽  
Lower Temperature

An experimental study is presented to (1) quantify the rate-sensitive mechanical response and (2) examine the localized deformation behavior under an applied temperature gradient in the alloy AA 2024. Isothermal flow stresses are obtained at temperatures from −100°C to 495°C and strain rates from 10−2/s to 10−5/s using routine compression tests and a novel cyclic test, which expedites the characterization. The material displays two distinct kinetic responses with both being amenable to localization phenomena. The lower temperature/high strain rate regime displays a rate-insensitive yield with Stage III/IV work hardening. At higher temperature/low strain rates, a rate-sensitive response with little work hardening is observed. In order to relate the material constitutive behavior to the development of localized deformation, a temperature gradient test is performed wherein temperature differences of approximately 30°C are enforced between the top and bottom surfaces of a cylindrical compression test specimen. Deformation heterogeneity developed in the two distinct regimes of material response is illustrative of warm and hot working conditions typical of industrial processes, such as rolling.

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