Assessment of the Thermal Radiation Spread in Special Conditions

2021 ◽  
pp. 13-20
Author(s):  
Yu.V. Gamera ◽  
◽  
Yu.Yu. Petrova ◽  
S.V. Ovcharov ◽  
L.V. Yagupova ◽  
...  
Keyword(s):  
Thermal Radiation ◽  
High Speed ◽  
Side Surface ◽  
Heat Fluxes ◽  
Gas Pipelines ◽  
Ground Source ◽  
Column Type ◽  
Main Pipelines ◽  
Gas Ignition ◽  
Hazardous Production

Increase of the requirements for the safety of hazardous production facilities stimulates the development and improvement of the methodological approaches to accidents consequences assessment on the main gas and other pipelines. Existing models for determining heat fluxes from radiating flame surfaces are focused on assessing damage under standard conditions when the epicenter of the accident is at the same altitude level with potential recipients and there are no barriers between them. In practice, special conditions are often implemented, in particular: fires on the pipelines located in the mountainous areas, safe passage of aircraft near the burning site, protection of objects from thermal radiation by installing impenetrable screens. Approaches are proposed related to assessing heat fluxes at the receiving sites located at different altitude levels with the fire source, as well as during accidents with ignition on the gas pipelines in the presence of screens protecting against thermal radiation. A parameter is introduced that describes the effect of the multilevel location of the source and the recipient on radiation — the coefficient of change in the thermal radiation flux from the side surface of a column-type fire in the absence of a wind, depending on the location height and distance in relation to the ground source of combustion of the site receiving the radiation. An expression is given for determining safe height of the flight of aircraft over a column-type fire in the range of flame heights from 50 to 850 m. Isolines of the fields of heat fluxes from the flame of a high-speed flat jet are calculated when the radiation is screened by a wall located at a normalized distance. The results obtained make it possible to predict the consequences of accidents on the main gas pipelines with gas ignition considering the relief, to assess the boundaries of safe corridors for flights of the aircraft near gas pipelines, and to efficiently develop means of protecting objects surrounding the main pipelines from thermal radiation from a flat torch.

scholarly journals APPLICATION OF ABLATION MATERIALSFOR HEAT PROTECTION OF CABINS OF FIRE-FIGHTING MACHINES

2020 ◽  
Vol 9 (4) ◽  
pp. 134-141
Author(s):  
Vladimir Kotenko ◽  
Vladimir Abrazumov ◽  
Mihail Ermochenkov
Keyword(s):  
Thermal Radiation ◽  
Forest Fire ◽  
Forest Fires ◽  
Thermal Protection ◽  
Protective Coatings ◽  
Heat Exposure ◽  
Heat Fluxes ◽  
Main Requirement ◽  
Low Efficiency ◽  
Intense Heat

Forest fires are accompanied by the release of a huge amount of heat, and the temperature at the edge of a forest fire, where firefighting equipment usually operates, reaches 300-700 °C. Fire engines are exposed to intense heat to extinguish forest fires. The main requirement for the design of such machines is the availability of rational thermal protection. Studies of various methods of thermal protection of cabins have showed the possibility of lowering the temperature on the inner surface of the cabin, but these methods show low efficiency. Protection of cabs from thermal radiation is not provided in the new developments of forest fire machines. It is proposed to use pre-preg coatings to protect cabins of forest fire engines. They are successfully used in spacecraft designs. Recent technologies for the production of such materials, developed recently, have significantly reduced the cost of production of these materials. It expands the possibilities of their application for other equipment subjected to intense heat exposure. The calculations have showed that the heat-protective coatings of the cabins made of pre-pregs quickly warm up to acceptable temperatures. However the use of water reserves in the tank of the car to cool the inside of the cabs provides high protection efficiency even at the limiting values of heat fluxes that occur in the fireplace. At the same time, water is not consumed; it is heated, circulating between the tank and the heat exchanger. The proposed method of protecting cabs of fire machines from thermal radiation is original one. It is a subject of further development.

Analysis of Thermal Radiation Models for Large Open Pool Fire on Ship Deck

2013 ◽  
Vol 470 ◽  
pp. 259-262
Author(s):  
Li Bin Ding ◽  
Jin Yun Pu ◽  
Kai Ren
Keyword(s):  
Heat Flux ◽  
Thermal Radiation ◽  
Point Source ◽  
Engineering Design ◽  
Source Model ◽  
Heat Fluxes ◽  
Pool Fire

Three radiation models are discussed in the present paper. The heat fluxes vary considerably between different methods. In all models, fluxes vary highly on the position of nearing the flame and are almost identical on the far away position. Heat fluxes calculated from point source model is less than other two models, and Shokri-Beyler model is highest. Shokri-Beyler method is most applicable at heat fluxes greater than 5 KW/m2 and recommended in engineering design, and Mudan model is not applicable for calculating the heat flux nearing the flame.

Incipient Flow Boiling in a Vertical Channel With a Wavy Wall

2010 ◽  
Author(s):  
T. Netz ◽  
R. Shalem ◽  
J. Aharon ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
High Speed ◽  
Flow Boiling ◽  
Heated Surface ◽  
Vertical Channel ◽  
Infrared Camera ◽  
Heat Fluxes ◽  
Heated Wall ◽  
Boiling Incipience

In the present study, incipient flow boiling of water is studied experimentally in a square-cross-section vertical channel. Water, preheated to 60–80 degrees Celsius, flows upwards. The channel has an electrically heated wall, where the heat fluxes can be as high as above one megawatt per square meter. The experiment is repeated for different water flow rates, and the maximum Reynolds number reached in the present study is 27,300. Boiling is observed and recorded using a high-speed digital video camera. The temperature field on the heated surface is measured with an infrared camera and a software is used to obtain quantitative temperature data. Thus, the recorded boiling images are analyzed in conjunction with the detailed temperature field. The dependence of incipient boiling on the flow and heat transfer parameters is established. For a flat wall, the results for various velocities and subcooling conditions agree well with the existing literature. Furthermore, three different wavy heated surfaces are explored, having the same pitch of 4mm but different amplitudes of 0.25mm, 0.5mm and 0.75mm. The effect of surface waviness on single-phase heat transfer and boiling incipience is shown. The differences in boiling incipience on various surfaces are elucidated, and the effect of wave amplitude on the results is discussed.

scholarly journals A New Simulation Model for Vertical Spiral Ground Heat Exchangers Combining Cylindrical Source Model and Capacity Resistance Model

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1339 ◽  
Author(s):  
Takao Katsura ◽  
Takashi Higashitani ◽  
Yuzhi Fang ◽  
Yoshitaka Sakata ◽  
Katsunori Nagano ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Simulation Model ◽  
High Speed ◽  
Approximate Equation ◽  
Source Model ◽  
Calculation Model ◽  
Ground Heat Exchangers ◽  
Ground Source ◽  
Equivalent Length ◽  
Cylindrical Source

Considering the heat capacity inside vertical spiral ground heat exchanger (VSGHEX) in the simulation is one of the most noteworthy challenge to design the ground source heat pump (GSHP) system with VSGHEXs. In this paper, a new simulation model for VSGHEXs is developed by combining the ICS model with the CaRM. The developed simulation model can consider the heat capacity inside VSGHEX and provide dynamic calculation with high speed and appropriate precision. In order to apply the CaRM, the equivalent length was introduced. Then, the equivalent length was approximated by comparing the results of the CaRM and the numerical calculation. In addition, the calculation model of the VSGHEX was integrated into the design and simulation tool for the GSHP system. The accuracy of the tool was verified by comparing with the measurements. The error between supply temperatures of the measurements and calculation is approximately 2 °C at the maximum. Finally, assuming GSHP systems with VSGHEXs, whose spiral diameter was 500 mm and depth was 4 m, were installed in residential houses in Japan, the required numbers of VSGHEXs were estimated. The results showed a strong correlation between the total heating or cooling load and the required number. Therefore, the required number can be estimated by using the simplified approximate equation.

Heat Flux Determination From Ultrasonic Pulse Measurements

2008 ◽  
Author(s):  
M. R. Myers ◽  
D. G. Walker ◽  
D. E. Yuhas ◽  
M. J. Mutton
Keyword(s):  
Heat Flux ◽  
Data Reduction ◽  
High Speed ◽  
Acoustic Pulse ◽  
Time Of Flight ◽  
Ultrasonic Pulse ◽  
Heat Fluxes ◽  
Measured Signal ◽  
Suitable Model ◽  
Ultrasonic Time

Ultrasonic time of flight measurements have been used to estimate the interior temperature of propulsion systems remotely. All that is needed is acoustic access to the boundary in question and a suitable model for the heat transfer along the path of the pulse train. The interior temperature is then deduced from a change in the time of flight and the temperature dependent velocity factor, which is obtained for various materials as a calibration step. Because the acoustic pulse samples the entire temperature distribution, inverse data reduction routines have been shown to provide stable and accurate estimates of the unknown temperature boundary. However, this technique is even more interesting when applied to unknown heat flux boundaries. Normally, the estimation of heat fluxes is even more susceptible to uncertainty in the measurement compared to temperature estimates. However, ultrasonic sensors can be treated as extremely high-speed calorimeters where the heat flux is directly proportional to the measured signal. Through some simple one-dimensional analyses, this work will show that heat flux is a more natural and stable quantity to estimate from ultrasonic time of flight. We have also introduced an approach for data reduction that makes use of a composite velocity factor, which is easier to measure.

Development of High Speed and High Temperature Atomic Layer Thermopiles

2019 ◽  
Author(s):  
Lakshya Bhatnagar ◽  
Guillermo Paniagua
Keyword(s):  
Heat Flux ◽  
High Temperature ◽  
High Speed ◽  
Cooling System ◽  
Numerical Study ◽  
Measurement Data ◽  
Atomic Layer ◽  
Heat Fluxes ◽  
Heat Transfer Analysis ◽  
Uncertainty Estimates

Abstract This work aims to provide a technique with which high frequency heat flux measurement data can be acquired in systems with high operational temperatures and high-speed flows with quantifiable and accurate uncertainty estimates. This manuscript presents the detailed calibration and application of an atomic layer thermopile, for heat fluxes with a frequency bandwidth of 0 to 1MHz. Two calibration procedures with a detailed uncertainty analysis. The first procedure consists using a laser to deliver radiation heat flux, while the second consists of a convective heat blowdown experiment. The use of this probe is demonstrated in a high-speed environment at Mach 2. The sensor effectively captures the passage of the normal shock wave and the values are compared with those computed using surface temperature measurement. Finally, a numerical study is carried out to design a cooling system that will allow the sensor to survive in high temperature conditions of 1273K while the sensor film is maintained at 323K. A two-dimensional axisymmetric conjugate heat transfer analysis is carried out to obtain the desired geometry.

Nucleate Boiling From Micro-Machined Surfaces

2003 ◽  
Author(s):  
Adrian M. Holland ◽  
Colin P. Garner
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Imaging System ◽  
Laser System ◽  
Ccd Camera ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Frame Rate ◽  
High Speed Imaging ◽  
Machined Surfaces

This paper discusses the production and use of laser-machined surfaces that provide enhanced nucleate boiling and heat transfer characteristics. The surface features of heated plates are known to have a significant effect on nucleate boiling heat transfer and bubble growth dynamics. Nucleate boiling starts from discrete bubbles that form on surface imperfections, such as cavities or scratches. The gas or vapours trapped in these imperfections serve as nuclei for the bubbles. After inception, the bubbles grow to a certain size and depart from the surface. In this work, special heated surfaces were manufactured by laser machining cavities into polished aluminium plates. This was accomplished with a Nd:YAG laser system, which allowed drilling of cavities of a known diameter. The size range of cavities was 20 to 250 micrometers. The resulting nucleate pool boiling was analysed using a novel high-speed imaging system comprising an infrared laser and high resolution CCD camera. This system was operated up to a 2 kHz frame rate and digital image processing allowed bubbles to be analysed statistically in terms of departure diameter, departure frequency, growth rate, shape and velocity. Data was obtained for heat fluxes up to 60 kW.m−2. Bubble measurements were obtained working with water at atmospheric pressure. The surface cavity diameters were selected to control the temperature at which vapour bubbles started to grow on the surface. The selected size and spacing of the cavities was also explored to provide optimal heat transfer.

Incorporation of THD Boundary Conditions for the Efficient Evaluation of Journal Bearing Performance

2007 ◽  
Author(s):  
P. S. Keogh ◽  
M. M. Khonsari
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Current Practice ◽  
Journal Bearing ◽  
Coefficient Matrix ◽  
Journal Bearings ◽  
Heat Fluxes ◽  
Solid Component ◽  
Influence Coefficient ◽  
Thermal Boundary Conditions

The evaluation of the thermohydrodynamic (THD) performance of journal bearings continues to be an important issue. This is particularly so for high speed or heavily loaded bearing designs. This paper focuses attention on the thermal boundary conditions at the lubricant-bearing interface. The solid component conduction problem is solved in advance of the main THD analysis. Boundary conditions are then imposed on the lubricant THD analysis through use of an appropriate influence coefficient matrix that incorporates the solid component conduction problem. This avoids the current practice of solving the lubricant and solid component problems separately in an iterative loop to achieve continuous temperatures and heat fluxes at the interface. Instead, only the lubricant problem needs to be solved using the boundary conditions imposed by the influence coefficient matrix.

Subcooled Flow Boiling on Micro-Porous Structured Copper Surface in a Vertical Mini-Gap Channel

2019 ◽  
Author(s):  
Junye Li ◽  
Kan Zhou ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
Copper Surface ◽  
Heat Fluxes ◽  
High Speed Flow ◽  
Subcooled Flow Boiling ◽  
Mass Fluxes ◽  
Speed Flow ◽  
Subcooled Flow

Abstract An experimental investigation of subcooled flow boiling in a large width-to-height-ratio, one-sided heating rectangular mini-gap channel was conducted with deionized water as the working fluid. The super-hydrophobicity micro-porous structured copper surface was utilized in the experiments. High speed flow visualization was conducted to illustrate the effects of heat flux and mass rate on the heat transfer coefficient and flow pattern on the surfaces. The mass fluxes were in the range of 200–500 kg/m2s, the wall heat fluxes were spanned from 40–400 kW/m2. With increments of imposed heat flux, the slopes of boiling curves for superhydrophobic micro-porous copper surfaces increased rapidly, indicating the Onset of Nucleate Boiling. Heat transfer characteristics were discussed with variation of heat fluxes and mass fluxes, the trends of which were analyzed with the aid of high speed flow visualization.

Changing from a Vertical Burr to a Horizontal Burr in the Vertical-Type High-Speed Twin-Roll Caster

2020 ◽  
Vol 1007 ◽  
pp. 29-33
Author(s):  
Toshio Haga ◽  
Yushi Murakami ◽  
Shou Kitamura ◽  
Hisaki Watari ◽  
Shinichi Nishida
Keyword(s):  
Mild Steel ◽  
High Speed ◽  
Side Surface ◽  
Strip Casting ◽  
Strip Edge ◽  
Twin Roll Caster ◽  
Roll Gap ◽  
Twin Roll ◽  
Semisolid Metal

Strip casting using a side dam plate produces a vertical burr at the strip edge. In the present study, changing this vertical burr into a horizontal burr using a burr changer is proposed. The burr changer was placed inside the side dam plate. The burr changer was made from mild steel and an insulator sheet and cut along the shape of the roll. The burr changer was placed so as to prevent exhaustion of semisolid metal between the side dam plate and the roll-side surface. When the position of the burr changer was appropriate, the vertical burr changed into a horizontal burr. The horizontal burr was flat. The width of the horizontal burr was affected by the lowest position of the burr changer and became narrower as the lowest position of the burr changer approached the roll gap position.

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