Theoretical Assessment of Convective and Radiative Heat Losses in a One-Dimensional Multiregion Premixed Flame With Counter-Flow Design Crossing Through Biofuel Particles

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Mehdi Bidabadi ◽  
Saman Hosseinzadeh ◽  
Sadegh Sadeghi ◽  
Mostafa Setareh
Keyword(s):  
Temperature Profile ◽  
Radiative Heat ◽  
Flame Structure ◽  
Flame Temperature ◽  
Heat Losses ◽  
Flame Velocity ◽  
Mass Fractions ◽  
Interface Matching ◽  
Energy Balances ◽  
Stagnation Plane

Due to perspective of biomass usage as a viable source of energy, this paper suggests a potential theoretical approach for studying multiregion nonadiabatic premixed flames with counterflow design crossing through the mixture of air (oxidizer) and lycopodium particles (biofuel). In this research, convective and radiative heat losses are analytically described. Due to the properties of lycopodium, roles of drying and vaporization are included so that the flame structure is created from preheating, drying, vaporization, reaction, and postflame regions. To follow temperature profile and mass fraction of the biofuel in solid and gaseous phases, dimensionalized and nondimensionalized forms of mass and energy balances are expressed. To ensure the continuity and calculate the positions of drying, vaporization, and flame fronts, interface matching conditions are derived employing matlab and mathematica software. For validation purpose, results for temperature profile is compared with those provided in a previous research study and an appropriate is observed under the same conditions. Finally, changes in flame velocity, flame temperature, solid and gaseous fuel mass fractions, and particle size with position measured from the position of stagnation plane, strain rate, and heat transfer coefficient in the presence/absence of losses are evaluated.

Fiber energy efficiency Part I: Extended entropy model

2014 ◽  
Vol 29 (2) ◽  
pp. 322-331 ◽  
Author(s):  
Anders Karlström ◽  
Karin Eriksson
Keyword(s):  
Energy Efficiency ◽  
Temperature Profile ◽  
Dynamic Models ◽  
Fluid Dynamic ◽  
Multiscale Model ◽  
Process Conditions ◽  
Entropy Model ◽  
Refining Zone ◽  
Energy Balances ◽  
Flat Zone

Abstract This is the first in a series of papers presenting the development of a comprehensive multiscale model with focus on fiber energy efficiency in thermo mechanical pulp processes. The fiber energy efficiency is related to the defibration and fibrillation work obtained when fibers and fiber bundles interact with the refining bars. The fiber energy efficiency differs from the total refining energy efficiency which includes the thermodynamical work as well. Extracting defibration and fibrillation work along the radius in the refining zone gives information valuable for fiber development studies.Models for this process must handle physical variables as well as machine specific parameters at different scales. To span the material and energy balances, spatial measurements from the refining zone must be available. In this paper, measurements of temperature profile and plate gaps from a full-scale CD-refiner are considered as model inputs together with a number of process variables. This enables the distributed consistency in the refining zone as well as the split of the total work between the flat zone and the CD-zone to be derived. As the temperature profile and the plate gap are available in the flat zone and the CD-zone at different process conditions it is also shown that the distributed pulp dynamic viscosity can be obtained. This is normally unknown in refining processes but certainly useful for all fluid dynamic models describing the bar-to-fiber interactions. Finally, it is shown that the inclusion of the machine parameters will be vital to get good estimates of the refining conditions and especially the split between the thermodynamical work and the defibration/fibrillation work.

Innovative energy and mass balance of a continuous evaporating crystallizer

2019 ◽  
pp. 646-654
Author(s):  
Jan Iciek ◽  
Kornel Hulak ◽  
Radosław Gruska
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Working Conditions ◽  
Crystallization Process ◽  
Heat Losses ◽  
Inert Gas ◽  
Gas Removal ◽  
Energy Balances ◽  
Heat Released ◽  
Mass And Energy Balances

The article presents the mass and energy balances of the sucrose crystallization process in a continuous evaporating crystallizer. The developed algorithm allows to assess the working conditions of the continuous evaporating crystallizers and the technological and energy parameters. The energy balance algorithm takes into account the heat released during the crystallization of sucrose, which was analyzed in this study, heat losses to the environment and heat losses due the vapor used for inert gas removal.

Effect of Corrugated Cover Directional Transmittance on the Thermal Performance of a Solar Collector

1981 ◽  
Vol 103 (2) ◽  
pp. 144-152
Author(s):  
T. F. Smith ◽  
S. Chaidar
Keyword(s):  
Solar Energy ◽  
Periodic Function ◽  
Thermal Performance ◽  
Solar Collector ◽  
Radiative Heat ◽  
Structural Strength ◽  
Heat Losses ◽  
Light Weight ◽  
Fiberglass Composite ◽  
Reduced Costs

The benefits of light weight, structural strength, and reduced costs without significant reduction of transmission of solar energy of a corrugated fiberglass composite cover promise wide utilization of this cover in solar collectors to suppress convective and radiative heat losses from the absorber panel. In order to evaluate the thermal performance of a collector with a corrugated cover, the directional transmittance of the cover must be available. A study was undertaken to develop a model for the directional transmittance of a corrugated cover as represented by a sinusoidal periodic function. As an application of this model, hourly and daily thermal efficiencies of a solar collector with a corrugated cover are presented.

scholarly journals Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

2019 ◽  
Vol 9 (19) ◽  
pp. 3989 ◽  
Author(s):  
Cheng Wang ◽  
Anthony Chun Yin Yuen ◽  
Qing Nian Chan ◽  
Timothy Bo Yuan Chen ◽  
Qian Chen ◽  
...  
Keyword(s):  
Flame Structure ◽  
Flame Temperature ◽  
Combustion Process ◽  
Flame Height ◽  
Reacting Flow ◽  
Detailed Chemistry ◽  
Eddy Generation ◽  
Fire Whirl ◽  
Generation Mechanisms ◽  
The Impact

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5   m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

Radiative heat losses from gas flames

1974 ◽  
Vol 7 (4) ◽  
pp. 492-495
Author(s):  
A. I. Rozlovskii ◽  
V. G. Khasanov ◽  
R. Kh. Gimatdinov
Keyword(s):  
Radiative Heat ◽  
Heat Losses

N-Heptane Pool Fire Behavior in a Controlled Oxygen and Low-Pressure Environment

2014 ◽  
Author(s):  
Quanyi Liu ◽  
Kewei Chen ◽  
Nan Wu ◽  
Jiusheng Yin ◽  
Rui Yang ◽  
...  
Keyword(s):  
High Altitude ◽  
Radiative Heat ◽  
Flame Temperature ◽  
Fire Behavior ◽  
Low Pressure ◽  
Pool Fire ◽  
Fire Tests ◽  
Mass Burning Rate ◽  
Low Oxygen ◽  
Lower Temperature

Fires at high altitude airports have attracted a lot of attention. Such fires show some special characteristics because of the coupling impact of low pressure and low oxygen levels. Some experiments, which were conducted recently at high altitude locations, such as Lhasa and in some low pressure chambers, were usually extinguished due to the limited supply of oxygen. In order to reveal the dependence of fire behavior on pressure comprehensively, a low-pressure chamber with ventilation control of 2×3×4.65m3 in volume has been developed and built, which can allow larger scale fire tests to be conducted and simulate more realistic high-altitude environment. In this study, pool fire tests using 20-cm and 30-cm-diameter pans are configured under five different static pressures, e.g. 101kPa, 75kPa, 64kPa, 38kPa and 24kPa. Each test has been repeated three times. The parameters measured include flame temperature, radiative heat flux, and mass loss etc. It is concluded that under lower pressure, mass burning rate is lower, temperature is higher, and height of the flame is higher, which demonstrated that low pressure fire is more dangerous to the buildings at high altitude airports.

A Numerical Investigation on the Effect of Hydrogen and Syngas Addition on the Ignition of JP-8 Surrogates

2012 ◽  
Author(s):  
Thomas Helma ◽  
S. K. Aggarwal
Keyword(s):  
Numerical Investigation ◽  
Ignition Delay ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Flame Structure ◽  
Flame Temperature ◽  
Kinetic Mechanism ◽  
Smoke Point ◽  
Temperature Profiles ◽  
Two Component

A numerical study is carried out investigating the effect of hydrogen and syngas addition on the ignition of two JP-8 surrogates, a two-component surrogate and a six-component surrogate. This six-component surrogate has previously been found to accurately simulate the smoke point, volatility, flame temperature profiles, and extinction limits of JP-8, while the two component surrogates has been shown to reproduce the flame structure predicted with the six-component surrogate. CHEMKIN 10101 is used to simulate ignition in a closed homogenous reactor under adiabatic and isobaric conditions. The parameters include temperature ranging from 850–1250 K, pressure of 20 atm, and equivalence ratio ϕ = 1.0. The CRECK-0810 kinetic mechanism, involving 341 species and 9173 reactions, is used to model the ignition chemistry. For the conditions studied, the addition of H2 or syngas in small quantities has no effect on the ignition behavior of either the surrogates or their individual components. Addition of H2 or syngas in larger quantities increases and decreases the ignition delay at low and high temperatures, respectively. For the conditions investigated, the ignition behavior of both the surrogates is predominantly determined by the ignition chemistry of n-dodecane.

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