Experimental study of electrostatic fields influencing thermal processes in gaseous methane at its natural convection

2021 ◽  
Author(s):  
V.A. Altunin ◽  
K.V. Altunin ◽  
M.R. Abdullin ◽  
M.R. Chigarev ◽  
I.N. Aliev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Plants ◽  
Discharge Zone ◽  
Thermal Processes ◽  
Electrostatic Fields ◽  
Experimental Base ◽  
Gaseous Media ◽  
History Of ◽  
The Heat Transfer Coefficient

The paper shows the history of studying electrostatic fields in various gaseous media, including gaseous methane, and substantiates the necessity to experimentally study electrostatic fields influencing thermal processes in gaseous methane at its natural convection. We describe the experimental base and working areas with the use of electrostatic fields, as well as the method of conducting experimental research. The results of the influence of electrostatic fields on the coefficient of heat transfer to gaseous methane and on the negative process of sedimentation in it — during its natural convection are presented. In our research, we found zones of possible intensification of heat transfer to gaseous methane and zones of saturation with electrostatic fields, in which a further increase in the heat transfer coefficient is impossible. We experimentally established that the boundary of the zone of the beginning of saturation with electrostatic fields is also the beginning of the corona discharge zone. The research results formed the basis for the method of using electrostatic fields in aircraft engines and power plants.

Methods for calculating thermal processes under conditions of natural convection of gaseous methane under the influence of electrostatic fields

2021 ◽  
Author(s):  
V.A. Altunin ◽  
K.V. Altunin ◽  
M.R. Abdullin ◽  
M.R. Chigarev ◽  
I.N. Aliev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Plants ◽  
Experimental Studies ◽  
Thermal Processes ◽  
Technical Literature ◽  
New Methods ◽  
Electric Wind ◽  
Electrostatic Fields ◽  
General Method

Relying on the review and analysis of scientific and technical literature, as well as the results of experimental studies, we developed new methods for calculating thermal processes occurring in gaseous methane during its natural convection, under the influence of electrostatic fields. In this study we show methods for calculating and determining the coefficients of heat transfer to gaseous methane under the influence of electric wind, as well as methods for calculating and determining the effect of electrostatic fields on the negative process of sedimentation on a heated experimental working plate in the volume of gaseous methane. A general method has been developed for the effective and safe application of electrostatic fields in gaseous methane, which must be carried out in the calculations, design, creation, and operation of new engines, power plants, and techno systems for single and reusable ground, air, aerospace and space-based aircraft.

Experimental study of thermal processes in gaseous methane at its natural convection

2021 ◽  
Author(s):  
V.A. Altunin ◽  
K.V. Altunin ◽  
M.R. Abdullin ◽  
M.R. Chigarev ◽  
I.N. Aliev ◽  
...  
Keyword(s):  
Experimental Study ◽  
Natural Convection ◽  
Power Plants ◽  
New Technologies ◽  
New Technology ◽  
Liquid Hydrocarbon ◽  
Thermal Processes ◽  
Rocket Engines ◽  
Air Jet ◽  
Single Use

The paper discovers the reasons for the transfer of single-use or reusable ground, air, aerospace, and space-based engines and power plants from liquid hydrocarbon fuels and coolers to gaseous fuels, or rather, to liquefied natural gas methane. The study gives specific examples of creating a new technology and using methane fuel and fuel in the existing units; lists the classes of methane engines and power plants, among which the main ones being piston engines and internal combustion power plants, air-jet engines and power plants, liquid propellant rocket engines and power plants. Findings of research show that it is necessary to experimentally study gaseous methane, so that it could be effectively used in advanced single-use or reusable ground, air, aerospace and space-based engines and power plants, and their features should be taken into account when designing and developing new technologies. The study introduces the results of the experimental study of thermal processes in gaseous methane during its natural convection, describes the experimental base in detail, as well as the procedure for conducting experiments, and develops methods for calculating the heat transfer coefficient to gaseous methane relying on the research results.

Heat Transfer Enhancement of Natural Convection Along a Vertical Heated Plate by Microbubble Injection

2011 ◽  
Author(s):  
Kazuaki Yamamoto ◽  
Atsuhide Kitagawa ◽  
Yoshimichi Hagiwara
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Heat Transfer Enhancement ◽  
Bubble Diameter ◽  
Heated Plate ◽  
Transfer Enhancement ◽  
Bubble Layer ◽  
Q 30 ◽  
The Heat Transfer Coefficient

This paper describes the heat transfer enhancement of natural convection along a vertical heated plate due to injection of microbubbles. Thermocouples are used for the temperature measurement and an image processing technique is used for obtaining the bubble diameter and the bubble layer thickness. The working fluid used is tap water, and hydrogen bubbles generated by electrolysis of the water are used as the microbubbles. The mean bubble diameter dm ranges from 26 to 57 μm. For each of the laminar and transition regions, the significant heat transfer enhancement is caused by the microbubble injection. Under a constant bubble flow rate (Q = 42 mm3/s), in the laminar region, the heat transfer coefficient for dm = 39 μm is higher than that for dm = 57 μm, but it is vice versa at x = 770 mm (transition region). Under a constant bubble size (dm = 39 μm), at each measurement position, the heat transfer coefficient for Q = 42 mm3/s is higher than that for Q = 30 mm3/s. These are deeply related to the fluctuation of the bubble layer thickness and small-scale eddy motions inherent in the flow. Moreover, in the case of dm = 39 μm and Q = 30 mm3/s, the heat transfer gain (which is the ratio of the heat transfer rate obtained with the microbubble injection to the power consumption of the mirobubble generation) is approximately 33. Therefore, microbubble injection is a very highly efficient technique for enhancing the natural convection heat transfer of water along a vertical flat plate.

Natural Convection Heat Transfer in Horizontal Cylindrical Cavities: A Computational Fluid Dynamics (CFD) Investigation

2013 ◽  
Author(s):  
Daniele Ludovisi ◽  
Ivo A. Garza
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Plants ◽  
Convection Heat Transfer ◽  
Weather Conditions ◽  
Freezing Temperature ◽  
Cold Weather ◽  
Pipe Surface ◽  
Cfd Models ◽  
Different Diameters

Many processes in power plants involve the storage and transfer of fluids including water in outdoor pipelines. Under extreme cold weather conditions, water can freeze if allowed to cool down to the freezing temperature. Installing insulation and maintaining adequate flow rate can sometimes prevent problems. However, during extended non-processing times, there are circumstances where cool down cannot be avoided and heat tracing along the piping becomes a necessity. In many instances, the need for the installation of heat tracing is simply determined based on pipe size. However, by performing accurate calculations, it is possible to determine if the need for heat tracing is real or not, thus saving on installation and maintenance costs. Correlations for the estimation of the heat transfer coefficient in horizontal cavities are not sufficiently documented in literature. In the present work, two-dimensional CFD models are used to investigate the natural convection in water-filled horizontal pipes of different diameters. The analysis has been carried out based on the assumption of a uniform pipe surface temperature. The Nusselt number is estimated as a function of the Rayleigh number and shown not to be strongly dependent on the Prandtl number. The analysis and the results of the numerical investigation are presented and compared to experimental data and other correlations available in literature. The documented correlation has an expanded range of applicability to high and low Rayleigh numbers, is supported by numerical and experimental results and is expressed in a simple form.

The Effect of Density Variation on Heat Transfer in the Critical Region

1961 ◽  
Vol 83 (2) ◽  
pp. 176-181 ◽  
Author(s):  
Yih-Yun Hsu ◽  
J. M. Smith
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Critical Point ◽  
Critical Region ◽  
Large Density ◽  
The Heat Transfer Coefficient

The heat-transfer coefficient between fluid and tube wall in turbulent flow depends upon the physical and thermal properties of the fluid. When density changes across the diameter of the tube are large (for example, when the fluid is near the critical point), the variable density can affect the transfer of momentum and heat. Equations are developed for predicting the magnitude of this effect on the heat-transfer coefficient. Deissler’s [5] expressions for the eddy diffusivity are employed in solving the equations for heat and momentum transfer. For flow in vertical tubes large density variations can also affect the heat transfer by inducing natural convection. By considering the influence of body forces on the shear stress, equations are derived to predict the effect of natural convection on the heat-transfer coefficient for turbulent flow. The results indicate that the effect is significant only for relatively high Grashof numbers and low Reynolds numbers. Such conditions may be encountered in flow of a fluid near its thermodynamic critical point. The derived equations are applied for carbon dioxide flow in the critical region under the conditions for which experimental data were measured by Bringer and Smith [2]. Because of the high Reynolds and low Grashof numbers, natural convection is not significant. However, the effect of the large density variations is found to be significant, and the predicted results agree well with the experimental data.

Elaboration of a criterion heat transfer equation of electrostatic fields influence in kerosene medium at free convection and deposit formation

2021 ◽  
Author(s):  
K.V. Altunin
Keyword(s):  
Heat Transfer ◽  
Power Plants ◽  
Liquid Hydrocarbon ◽  
Deposit Formation ◽  
Heat Transfer Intensification ◽  
Electrostatic Fields ◽  
Fuel Delivery ◽  
Criterion Equation ◽  
New Criterion ◽  
Dimensionless Similarity

The paper focuses on the problem of deposit formation in engines and power plants operating on liquid hydrocarbon fuels and coolers, and analyzes hydrocarbon deposit formation on heated fuel-delivery metal at increased temperature. First, an experimental setup was created to study the effect of electrostatic fields on the heat transfer intensification in liquid aviation kerosene TS-1 and the process of deposit formation on a heated working plate. Then, the effect of electric wind on thermal processes was visualized using the Tepler optical setup and the influence of electrostatic fields on the processes of heat transfer of deposit formation in the kerosene medium when using coaxial needles as electrodes was studied. Finally, findings of the research were generalized and a new criterion equation with a created dimensionless similarity number of electric convection and deposit formation simplex was introduced.

Natural Convection of Viscoplastic Fluids in an Enclosure With Localized Heating and Symmetrical Cooling

2013 ◽  
Author(s):  
Mohd. Ashique Hassan ◽  
Manabendra Pathak ◽  
Mohd. Kaleem Khan
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Constant Heat Flux ◽  
Bottom Wall ◽  
Viscoplastic Fluid ◽  
Square Enclosure ◽  
Viscoplastic Fluids ◽  
Localized Heating ◽  
Side Walls ◽  
The Heat Transfer Coefficient

In this study a computational investigation of two-dimensional, steady-state, natural convection of viscoplastic fluid in a square enclosure has been presented. The enclosure has been locally heated from the bottom wall using a constant heat flux source and symmetrically cooled from both the side walls. The other walls are maintained as insulated surfaces. Finite volume based code has been used in the simulation and Bingham model has been used to model the rheology of the enclosed viscoplastic fluids. Simulations have been made for three different heating lengths of the bottom wall. The flow phenomenon and heat transfer inside the enclosure have been investigated for different properties of viscoplastic fluid, heating conditions and heated length. It has been observed that for a particular thermal condition the heat transfer coefficient or the Nusselt number decrease with the increase in yield stress value of the fluid due to weakening of convective circulation.

Transient Pool Boiling Heat Transfer—Part 1: Incipient Boiling Superheat

1977 ◽  
Vol 99 (4) ◽  
pp. 547-553 ◽  
Author(s):  
A. Sakurai ◽  
M. Shiotsu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Boiling Point ◽  
Boiling Heat Transfer ◽  
High Heat ◽  
The Other ◽  
High Heat Flux ◽  
The Heat Transfer Coefficient

Incipient boiling superheat for exponentially increasing heat inputs to a platinum wire supported horizontally in a pool of water was measured for exponential periods ranging from 5 ms to 10 s and for subcoolings ranging from 25 to 75K under atomospheric pressure. The heat transfer coefficient before the initiation of boiling was related to those by conduction and by natural convection. The heat flux at the incipient boiling point increased with the decrease in the period. The log-log plot of the heat flux against the superheat at the incipient boiling point had a single asymptotic line of slope 2 which was independent of subcoolings in the high heat flux region. On the other hand, as the heat flux decreased to zero, the superheat tended to approach to a constant value for each subcooling. This asymptotic superheat at zero heat flux was higher for higher subcooling. Transient incipient boiling superheat was reasonably explained by the combination of two kinds of incipient boiling models.

Improved Correlation for Natural Convection Heat Transfer From Inclined Cylinders Having Different Emissivities

1999 ◽  
Author(s):  
Jeffrey C. Stewart ◽  
William S. Janna
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
The Heat Transfer Coefficient

Abstract The purpose of this study was to develop an improved correlation for natural convection heat transfer from inclined cylinders having different emissivities. The angle of cylinder inclination varied from horizontal to vertical in 15° increments. The heat transfer coefficient was obtained experimentally with the cylinder in a state of constant heat flux. Three surface finishes were used in the experiment, which consisted of polished copper, black paint, and aluminum paint. The heat transfer coefficients in all cases varied from 1.21 to 1.65 BTU/(hr·ft2·R) [6.87 to 9.37 W/(m2·K)]. Rayeigh numbers for all experiments varied from 1.31 × 103 to 2.23 × 103. The heat transfer coefficient decreased for each cylinder with an increasing angle of inclination (from horizontal to vertical). The goal of this study was to produce Nusselt-Rayleigh number correlations for each cylinder, and then ultimately produce a single equation that can be applied for all emissivities. The Rayleigh number included a geometry term to account for the inclination of the cylinder. The form of the equation that best represented the data was a power law equation.

Problems of Thermophysics and Thermal Engineering for the New Technologies of the Twenty-First Century

2005 ◽  
Vol 58 (3) ◽  
pp. 206-223 ◽  
Author(s):  
I. Z. Kopp
Keyword(s):  
Heat Transfer ◽  
Power Plants ◽  
Large Scale ◽  
New Technologies ◽  
Review Article ◽  
Thermal Engineering ◽  
Thermal Processes ◽  
Two Phase ◽  
Temperature Plasma ◽  
New Approaches

This review article gives an overview of some topics related to classical and modern problems in the theory of heat, its meaning for various branches, and thermal management of equipment. The specific requirements for new technologies involved in the thermal operation of miniaturized instruments, components of equipment, devices, units operating in fast-response regimes, improvement of heat resistance, reliability, and endurance are considered. Special requirements have been put forward for nanotechnologies, where engineering parts, elements of devices, and technological equipment have microscopic and submicroscopic dimensions. Also, the stringent requirements of thermal modes of modern large-scale technologies in such branches of industry as nuclear power engineering and rocket-space engineering have become more important and determining. The thermal modes of these technologies call for new approaches to the design of the thermodynamic state of micro- and macrosystems, high-temperature plasma, and cryogenic temperatures. New results of the study of the mechanism of heat transfer in phase transitions, principally in new approaches to the problem of enhancement of heat transfer in one- and two-phase flows are presented. The importance of studies of thermal processes providing reliable thermal modes of new power plants, microsystems, and nanotechnologies is shown. The significance of advances in the study of thermal processes for developing the theory of heat is discussed. Especially considered are achievements in the theory of heat for its role in the decisions of actual problems of biology, medicine, and environment. This review article cites 105 references, most of them in Russian.

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