scholarly journals Gas-air mixture explosion behaviour research at different temperatures

2021 ◽  
Vol 2094 (5) ◽  
pp. 052052
Author(s):  
S V Klochkov ◽  
A N Minkin ◽  
D A Edimichev ◽  
A A Krekhov ◽  
E V Chistova
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Flow Control ◽  
Low Temperatures ◽  
Test Bench ◽  
Meteorological Conditions ◽  
Gas Mixture ◽  
Initial Moment ◽  
Different Temperatures ◽  
Plastic Bag

Abstract This article discusses gas-air mixture explosion properties depending on its initial parameters. Authors use the heat flow control sensor to obtain the most dangerous concentration range at normal and low temperatures. The dependences of heat flux changes at initial moment of explosion under different conditions are analyzed. The survey setup was a plastic bag filled with a gas mixture. Experiments were carried out with (without) holding the substance and with (without) using the turbulators. The reliability of acquired data was assessed by running a tenfold repetition of each test bench under identical meteorological conditions.

Heat Flow Calorimetry

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Flow ◽  
Heat Sink ◽  
Reaction Vessel ◽  
Heat Output ◽  
Large Numbers ◽  
Different Temperatures

Heat flow calorimeters, also known as “heat flux,” “heat conduction,” or “heat leakage” calorimeters, are instruments where the heat output or input associated with a given phenomenon is transferred between a reaction vessel and a heat sink. This heat transfer can be monitored with high thermal conductivity thermopiles containing large numbers of identical thermocouple junctions regularly arranged around the reaction vessel (the cell) and connecting its outside wall to the heat sink (the thermostat). The determination of the heat flow relies on the so-called Seebeck effect. An electric potential, known as thermoelectric force and represented by E, is observed when two wires of different metals are joined at both ends and these junctions are subjected to different temperatures, T1 and T2. Several thermocouples can be associated, forming a thermopile. For small temperature differences, the thermoelectric force generated by the thermopile is proportional to T1 − T2 and to the number of thermocouples of the pile (n): E = nε ′ (T1 − T2) (9.1) where ε′ is the thermoelectric power of a single thermocouple (ε′ = dE/dT).

scholarly journals A Comparative Electrochemical and Morphological Investigation on the Behavior of NiCr and CoCr Dental Alloys at Various Temperatures

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 256
Author(s):  
Florentina Golgovici ◽  
Mariana Prodana ◽  
Florentina Gina Ionascu ◽  
Ioana Demetrescu
Keyword(s):  
Low Temperatures ◽  
Artificial Saliva ◽  
Electrochemical Stability ◽  
Morphological Investigation ◽  
Dental Alloys ◽  
Ion Release ◽  
Icp Ms ◽  
Different Temperatures ◽  
Good Concordance ◽  
Increasing Temperature

The purpose of our study is to compare the behavior of two reprocessed dental alloys (NiCr and CoCr) at different temperatures considering the idea that food and drinks in the oral cavity create various compositions at different pH levels; the novelty is the investigation of temperature effect on corrosion parameters and ion release of dental alloys. Electrochemical stability was studied together with morphology, elemental composition and ions release determination. The results obtained are in good concordance: electrochemistry studies reveal that the corrosion rate is increasing by increasing the temperature. From SEM coupled with EDS, the oxide film formed on the surface of the alloys is stable at low temperatures and a trend to break after 310K. ICP-MS results evidence that in accordance with increasing temperature, the quantities of ions released from the alloys immersed in artificial saliva also increase, though they still remain small, less than 20 ppm.

A Model for Droplet Vaporization for Use in Gasoline and HCCI Engine Applications

2004 ◽  
Vol 126 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Youngchul Ra ◽  
Rolf D. Feitz
Keyword(s):  
Heat Flux ◽  
Internal Heat ◽  
Droplet Surface ◽  
Fuel Vapor ◽  
Gas Mixture ◽  
Ambient Temperatures ◽  
Droplet Vaporization ◽  
Flux Model ◽  
Heat Flux Model

A model for unsteady droplet vaporization is presented that considers the droplet temperature range from flash-boiling conditions to normal evaporation. The theory of continuous thermodynamics was used to model the properties and compositions of multicomponent fuels such as gasoline. In order to model the change of evaporation rate from normal to boiling conditions more realistically, an unsteady internal heat flux model and a new model for the determination of the droplet surface temperature is proposed. An explicit form of the equation to determine the heat flux from the surrounding gas mixture to the droplet-gas interface was obtained from an approximate solution of the quasi-steady energy equation for the surrounding gas mixture, with the inter-diffusion of fuel vapor and the surrounding gas taken into account. The model was applied to calculate evaporation processes of droplets for various ambient temperatures and droplet temperatures.

scholarly journals The effects of environmental temperature on the properties of myofibrillar adenosine triphosphatase from various species of fish

1973 ◽  
Vol 133 (4) ◽  
pp. 735-738 ◽  
Author(s):  
Ian A. Johnston ◽  
Neil Frearson ◽  
Geoffrey Goldspink
Keyword(s):  
Low Temperatures ◽  
Half Life ◽  
Adenosine Triphosphatase ◽  
Environmental Temperature ◽  
Cold Water ◽  
Warm Water ◽  
Adenosine Triphosphatase Activity ◽  
Water Fish ◽  
Different Temperatures ◽  
Myotomal Muscle

1. Myofibrillar adenosine triphosphatase (ATPase) activities were measured for white myotomal muscle of 19 species of fish. 2. The activity was measured at different temperatures and after periods of preincubation at 37°C. 3. The inactivation half-life at 37°C depended on environmental temperature, increasing as the temperature increased. 4. Cold-water fish had higher myofibrillar adenosine triphosphatase activity at low temperatures than had warm-water fish. 5. The significance of these results is discussed.

scholarly journals Expansion of the Range of Refrigeration of the Surface Heat Flow Unit Under Conductive Energy Produce

2018 ◽  
pp. 27-32
Author(s):  
S. Kovtun
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Flux Density ◽  
Heat Flux Density ◽  
Dynamic Range ◽  
Density Measurement ◽  
Lower Boundary ◽  
Surface Heat ◽  
Total Uncertainty ◽  
Unit Of Measurement

The article presents the results of investigations of factors that influence the accuracy of reproduction of the unit of measurement of the surface density of the heat flow by conductivity. Components of the uncertainty of the surface heat flux density measurement were analyzed using the Ishikawa cause-and-effect diagram, as shown in Fig. 1 The mathematical model of the method of reproduction of the unit of measurement was obtained, which takes into account the influence of the sources of uncertainty by making the corresponding corrections. The possibility of extending the lower boundary of the dynamic range by the correction of the factors having the greatest influence is substantiated. The rationale is based on the estimation of the uncertainty of the individual components, which, in the course of the correction of their impact, should not exceed the values (achieved to date). As an example, the calculation of the total uncertainty in the reproduction of the heat flux density of 20 W·m-2 is given. Table 1 contains all data important for the uncertainty analysis such as input quantities, their estimated values as well as the associated sensitivity coefficients and the variances determined.

scholarly journals Using a coupled large-eddy simulation–aerosol radiation model to investigate urban haze: sensitivity to aerosol loading and meteorological conditions

2020 ◽  
Vol 20 (20) ◽  
pp. 11893-11906
Author(s):  
Jessica Slater ◽  
Juha Tonttila ◽  
Gordon McFiggans ◽  
Paul Connolly ◽  
Sami Romakkaniemi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Feedback Loop ◽  
Meteorological Conditions ◽  
Anthropogenic Heat ◽  
Aerosol Loading ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Boundary Layer Dynamics

Abstract. The aerosol–radiation–meteorology feedback loop is the process by which aerosols interact with solar radiation to influence boundary layer meteorology. Through this feedback, aerosols cause cooling of the surface, resulting in reduced buoyant turbulence, enhanced atmospheric stratification and suppressed boundary layer growth. These changes in meteorology result in the accumulation of aerosols in a shallow boundary layer, which can enhance the extent of aerosol–radiation interactions. The feedback effect is thought to be important during periods of high aerosol concentrations, for example, during urban haze. However, direct quantification and isolation of the factors and processes affecting the feedback loop have thus far been limited to observations and low-resolution modelling studies. The coupled large-eddy simulation (LES)–aerosol model, the University of California, Los Angeles large-eddy simulation – Sectional Aerosol Scheme for Large Scale Applications (UCLALES-SALSA), allows for direct interpretation on the sensitivity of boundary layer dynamics to aerosol perturbations. In this work, UCLALES-SALSA has for the first time been explicitly set up to model the urban environment, including addition of an anthropogenic heat flux and treatment of heat storage terms, to examine the sensitivity of meteorology to the newly coupled aerosol–radiation scheme. We find that (a) sensitivity of boundary layer dynamics in the model to initial meteorological conditions is extremely high, (b) simulations with high aerosol loading (220 µg m−3) compared to low aerosol loading (55 µg m−3) cause overall surface cooling and a reduction in sensible heat flux, turbulent kinetic energy and planetary boundary layer height for all 3 d examined, and (c) initial meteorological conditions impact the vertical distribution of aerosols throughout the day.

scholarly journals CONSEQUENCES OF PRESOWING INFLUENCE OF LOW AND VARIABLE TEMPERATURES ON CARROT AND RADISH SEEDS

2019 ◽  
pp. 62-64
Author(s):  
S. R. Gasanov ◽  
S. A. Mammadova
Keyword(s):  
Low Temperatures ◽  
Raphanus Sativus ◽  
Seed Treatment ◽  
Growth And Yield ◽  
Average Weight ◽  
Vegetable Crops ◽  
Root Crops ◽  
Different Temperatures ◽  
Sowing Seed ◽  
The Impact

The study of the dynamics of plant growth and yield of vegetable crops (carrot variety Absheron winter (Daucus carota subsp. sativus (Hoffm.) Schьbl.) and radish variety Virovsky white (Raphanus sativus var.radicula Pers.)) was conducted in the field conditions after presowing exposure to different temperatures: I option – sowing of seeds exposed to low temperatures (for 15 days the swollen for 24 hours seeds were kept at a temperature of 0±1°С); Option II - sowing of seeds exposed to variable temperatures (for 5 days, the swollen for 24 hours seeds were exposed to variable temperatures of + 20°C (8 hours) and 0±1°C (16 hours) and then 10 days at a temperature of 0±1°C; K1 – sowing dry seeds; K2 – sowing soaked seeds. The impact on the seeds of low and variable temperatures caused an increase in growth processes, both in radish and carrot. Both studied crops showed a tendency to increase the yield to a greater extent when exposed to swollen seeds with variable temperatures. Thus, the average weight of radish crops exceeded the control variant by 47.1% and carrots by 27.6%. The yield of root crops per m2increased by 36.4% for radish and 30.0% for carrot. To increase the productivity of vegetable crops, we recommend using the studied methods of pre-sowing seed treatment in practice.

Oxygen Effect in Diamond Deposition at Low Temperatures

1989 ◽  
Vol 162 ◽  
Author(s):  
Y. Liou ◽  
A. Inspektor ◽  
R. Weimer ◽  
D. Knight ◽  
R. Messier
Keyword(s):  
Thin Films ◽  
Low Temperatures ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Gas Mixtures ◽  
Diamond Growth ◽  
Oxygen Effect ◽  
Gas Mixture ◽  
Diamond Thin Films ◽  
Deposited Films

ABSTRACTDiamond thin films were deposited on different substrates at low temperatures (lowest temperature∼ 300°C, estimated) in a microwave plasma enhanced chemical vapor deposition (MPCVD) system. The deposited films were amorphous carbon or diamond films depending on the different gas mixtures used. The growth rate of diamond thin films was decreased by adding oxygen to the gas mixture. The addition of oxygen to the gas mixtures was found to be important for diamond growth at low temperatures. Different concentrations of oxygen have been added into the gas mixture. Without oxygen, the deposited films were white soots and easily scratched off. Increasing the oxygen input improved the quality of the Raman peaks and increased the film transpancy. The diamond films were also characterized by scanning electron microscopy (SEM).

Thermal metamaterials for radiative plus conductive heat flow control

2020 ◽  
Vol 116 (19) ◽  
pp. 191902
Author(s):  
Ercan M. Dede ◽  
Ziqi Yu ◽  
Paul Schmalenberg ◽  
Hideo Iizuka
Keyword(s):  
Heat Flow ◽  
Flow Control ◽  
Conductive Heat ◽  
Conductive Heat Flow

scholarly journals The Heat Flux Vector(s) in a Two Component Fluid Mixture

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 77
Author(s):  
A. D. Kirwan ◽  
Mehrdad Massoudi
Keyword(s):  
Heat Flux ◽  
Interaction Force ◽  
Heat Fluxes ◽  
Fluid Mixture ◽  
Two Fluids ◽  
Heat Flux Vector ◽  
Special Cases ◽  
Different Temperatures ◽  
Phenomenological Coefficients ◽  
Kinematic Properties

Bulk kinematic properties of mixtures such as velocity are known to be the density weighed averages of the constituent velocities. No such paradigm exists for the heat flux of mixtures when the constituents have different temperatures. Using standard principles such as frame indifference, we address this topic by developing linear constitutive equations for the constituent heat fluxes, the interaction force between constituents, and the stresses for a mixture of two fluids. Although these equations contain 18 phenomenological coefficients, we are able to use the Clausius-Duhem inequality to obtain inequalities involving the principal and cross flux coefficients. The theory is applied to some special cases and shown to reduce to standard results when the constituents have the same temperature.

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