scholarly journals Formation of glacier tables caused by differential ice melting

2021 ◽  
Author(s):  
Marceau Hénot ◽  
Vincent Langlois ◽  
Nicolas Plihon ◽  
Nicolas Taberlet
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Field Measurements ◽  
The Other ◽  
Solar Irradiation ◽  
Shielding Effect ◽  
Ice Melting ◽  
Conduction Model ◽  
The One ◽  
Direct Solar Irradiation

Abstract. Glacier tables are structures frequently encountered on temperate glaciers. They consist of a rock supported by a narrow ice foot which forms through differential melting of the ice. In this article, we investigate their formation by following their dynamics on the Mer de glace glacier (Alps, France). We report field measurements of four specific glacier tables over the course of several days, as well as snapshot measurements of a field of 80 tables performed on one given day. We develop a simple analytical 1-D heat conduction model accounting for the various mechanisms of the heat transfer on the glacier using local meteoreorological data, and which displays excellent agreement with the field measurements. We show that the formation of glacier tables results from a competition between two effects: on the one hand, a geometrical amplification of the heat flux received by the rock and transmitted to the ice underneath on the one hand, and on the other hand, a shielding effect resulting from the warmer temperature of the rocks compared to that of the ice (reducing the sensible and net infrared incident fluxes). The latter is greatly amplified by direct solar irradiation, which induces a strong temperature gradient across the thickness of the rock.

Thermodynamic Analysis of the Internal Melt-Ice-on-Tube during Melting under Natural Convection

2014 ◽  
Vol 937 ◽  
pp. 375-380
Author(s):  
Yi Liu ◽  
Xin Chen
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Storage System ◽  
Heat Transfer Process ◽  
The Other ◽  
Ice Storage ◽  
Ice Melting ◽  
Single Tube ◽  
Initial Stage ◽  
The One

The numerical simulation of the ice melting processes in internal melt-ice-on-tube which is applied widely in the ice storage system is carried out. The dynamic mathematical models about melting are established and solved by using enthalpy method. Natural convection of the melted water in the course of melting is studied, and natural convection influences on single tube in melting heat transfer process is analyzed under the related parameters. Several conclusions are obtained:1. Because of natural convection of the melted water, the curve of melting interface is no longer a circle, but a curve changing with angle. The melting radius reaches minimum at the bottom and maximum at the top.2. The one with natural convention is compared to the other not considered. At initial stage, the influence of natural convection is smaller in the course of melting. However, the influence of natural convention increases along with melting.

Gas Turbine Combustor Liner Wall Heat Load Characterization for Different Gaseous Fuels

2019 ◽  
Author(s):  
Kishore Ranganath Ramakrishnan ◽  
Shoaib Ahmed ◽  
Benjamin Wahls ◽  
Prashant Singh ◽  
Maria A. Aleman ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Load ◽  
Recirculation Zone ◽  
Flame Temperature ◽  
Conduction Model ◽  
Steady State Condition ◽  
Gaseous Fuels ◽  
Peak Heat Flux ◽  
Combustor Liner

Abstract The knowledge of detailed distribution of heat load on swirl stabilized combustor liner wall is imperative in the development of liner-specific cooling arrangements, aimed towards maintaining uniform liner wall temperatures for reduced thermal stress levels. Heat transfer and fluid flow experiments have been conducted on a swirl stabilized lean premixed combustor to understand the behavior of Methane-, Propane-, and Butane-based flames. These fuels were compared at different equivalence ratios for a matching adiabatic flame temperature of Methane at 0.65 equivalence ratio. Above experiments were carried out a fixed Reynolds number (based on the combustor diameter) of 12000, where the pre-heated air temperature was approximately 373K. Combustor liner in this setup was made from 4 mm thick quartz tube. An infrared camera was used to record the inner and outer temperatures of liner wall, and two-dimensional heat conduction model was used to find the wall heat flux at a quasi-steady state condition. Flow field in the combustor was measured through Particle Image Velocimetry. The variation of peak heat flux on the liner wall, position of peak heat flux and heat transfer, and position of impingement of flame on the liner have been presented in this study. For all three gaseous fuels studied, the major swirl stabilized flame features such as corner recirculation zone, central recirculation zone and shear layers have been observed to be similar. Liner wall and exhaust temperature for Butane was highest among the fuel tested in this study which was expected as the heat released from combustion of Butane is higher than that of Methane and Propane.

scholarly journals A method of experimental studies of heat transfer processes between industrial constructions

2018 ◽  
Vol 230 ◽  
pp. 02021
Author(s):  
Vadym Nizhnyk ◽  
Oksana Kyrychenko ◽  
Olexandr Tarasenko ◽  
Andrii Shvydenko ◽  
Serhii Hovalenkov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Flux Density ◽  
Experimental Studies ◽  
Heat Radiation ◽  
Ambient Conditions ◽  
Transfer Processes ◽  
Density Values ◽  
New Type ◽  
The One

A method of experimental study of heat transfer processes between industrial constructions during a fire was developed. Types of equipment necessary for the conduction of the experimental studies were determined. A new type of specimen to be used as the one to be studied when conducting experimental studies was developed. Installation sites of thermocouples and heat flux detector on the specimen under study are shown as layout. Installation sites of the specimens under study relative to heat radiation source were substantiated experimentally. Succession of the conduction of the experimental studies of heat transfer processes between industrial constructions during a fire was developed which consists of the following procedures: production of specimens for the studies, measurement and recording on ambient conditions, measuring of temperature and heat flux on the surface of the specimen under study, and filling 55B test fire with water and diesel fuel. It was established that average temperatures and heat flux density values as well as flame geometry should be measured when performing experimental studies.

Flow Film Boiling From a Sphere to Subcooled Freon-11

1986 ◽  
Vol 108 (4) ◽  
pp. 934-938 ◽  
Author(s):  
J. A. Orozco ◽  
L. C. Witte
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Empirical Correlation ◽  
The Other ◽  
Film Boiling ◽  
Vapor Film ◽  
Peak Heat Flux ◽  
Semi Empirical

The boiling curves for flow boiling of freon-11 from a fluid-heated 3.81-cm-dia copper sphere showed dual maxima. One maximum corresponded to the nucleate peak heat flux while the other was caused by transitory behavior of the wake behind the sphere. Film boiling data were predicted well by the theory of Witte and Orozco. A semi-empirical correlation of the film boiling data accounting for both liquid velocity and subcooling predicted the heat transfer to within +/− 20 percent. The conditions at which the vapor film became unstable were also determined for various sub-coolings and velocities.

Effect of the Inclination on Three-Dimensional Incompressible Fluid Flow in a Discretely Heated Cavity

2013 ◽  
Vol 597 ◽  
pp. 3-8
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida ◽  
Slawomir Smolen ◽  
Touria Mediouni
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Vertical Wall ◽  
Three Dimensional ◽  
The Other ◽  
Uniform Temperature ◽  
Incompressible Fluid Flow ◽  
Electronic Components ◽  
Flow And Heat Transfer

Natural convection in inclined cubic cavity, discretely heated, is studied numerically using a three-dimensional finite volume formulation. Two heating square portions are placed on the vertical wall of the enclosure, while the rest of the considered wall is adiabatic. These sections, similar to the integrated electronic components, generate a heat flux q". The opposite vertical wall is maintained at a cold uniform temperature Tc and the other walls are adiabatic. The fluid flow and heat transfer in the cavity are studied for different sets of the governing parameters, namely the Rayleigh number Ra (103 ≤ Ra ≤ 107), the cavity inclination γ (- 45° ≤ γ ≤ 45°) and the position of the heating sections λ (0.3 ≤ λ ≤ 0.7). The dimensions of the heater sections, ε = D / H and the longitudinal aspect ratio of the cavity Ax = H / L are respectively fixed to 0.35 and 1.

Experimental Study of Uniform and Non-Uniform Transverse Heat Flux Distribution Effect on the Onset of Nucleate Boiling

2017 ◽  
Author(s):  
Omar S. Al-Yahia ◽  
Taewoo Kim ◽  
Daeseong Jo
Keyword(s):  
Heat Flux ◽  
Power Distribution ◽  
Test Section ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
The Other ◽  
Heated Plate ◽  
Heated Section ◽  
Other Hand ◽  
The One

An experiment study is conducted to investigate the effect of transverse power distribution on the Onset of Nucleate Boiling (ONB) through a one-side heated narrow rectangular channel. Two test section are used to perform the experiment; uniform and non-uniform heated suction. The demineralized water is flowing in upward direction through the coolant channel with a thickness of 2.35 mm, a width of 54 mm, and a length of 300 mm. The experiment is carried out under different thermal power (0.5 kW – 6.5 kW) for the both test section. As well as, a wide variety of inlet subcooling and flow velocity are used as; 65−35 °C and 0.1–1.0 m/s, respectively. The wall temperature distribution of the heated plate is measured by 10 TCs for the uniformly heated test section, and 20 TC for the non-uniformly heated section. On the other hand, the ONB location is visualized via high speed camera, in which the ONB occurs near the edges for the non-uniformly heated section and occurs at the center of the heated surface for the uniformly power distribution. The results of the ONB heat flux and temperature in the non-uniformly heated section are compared against the one in the uniformly heated power. The results show the variety of the ONB location, ONB heat flux with the different power distribution. With the increase of the power, the ONB is shifted toward the inlet. On the other hand, the ONB for the non-uniform power distribution occurs near the edges at power lower than that the one in the uniformly power distribution. Also, the results are compared against the available correlations, such as Bergles and Rohsenow (1965), Jens and Lottes (1951), and Thom et al. (1965), as well as other experimental results done by several research institutes.

Experimental Investigation of Influence of Dissolved Salts and Surfactant on Heat Transfer in Atomized Spray Quenching of Metal

2010 ◽  
Author(s):  
Umair Alam ◽  
Khalid Abd alrahman ◽  
Eckehard Specht
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Measurement ◽  
Pure Water ◽  
The Other ◽  
Film Boiling ◽  
Wetting Front ◽  
Maximum Heat ◽  
Boiling Regime ◽  
Front Position

Spray quenching is widely used in industrial applications. In atomized spray quenching (ASQ), water and air are supplied to the nozzle at a certain flow rate and pressure to produce a full cone spray consisting of discrete droplets. Impingement density of spray i.e. coolant mass flow per unit area per second is considered to be the most influential parameter for heat transfer. Impingement density varies with radius and so as the heat flux. Water quality is altered by adding five different salts i.e. NaCl, Na2SO4, NaHCO3, Na2CO3, and MgSO4 in de-ionized water with various concentrations. On the other hand, a surfactant Ethoxylated ester, which is commonly added in cooling water in cast houses of metals, is added to pure water in different concentrations i.e 50, 100, 200 and 500ppm. A circular disc made of Nickel of thickness 2mm is heated to 600°C and sprayed on one side by atomized spray and the temperature distribution with respect to time is measured using Infrared camera on the other side of the disc. By this IR thermography, transient temperature measurement can be done within the window of 320×80 pixels with a minimum pixel real distance of 1mm on the sheet surface. Frequency of measurement is 150Hz. Since the temperature measurement and cooling sides are opposite at 2mm thickness apart, inverse heat conduction problem is solved by applying finite element method for calculating temperature and heat flux on the quenched side of metal sheet with respect to space and time. It has been observed that increasing the concentration of salts increase the leidenfrost point and shortens the film boiling regime. While addition of surfactants decrease the leidenfrost point and prolong the film boiling regime. Maximum heat flux position is considered as the wetting front position. There is an abrupt variation of heat flux at wetting front position due to the change of boiling phenomenon. Wetting front velocity has been compared for salt solutions, surfactant and de-ionized or pure water.

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.

Effect of Reynolds Number on Deposition in Fuels Flowing Over Heated Surfaces

2013 ◽  
Author(s):  
Clifford Moses
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Chemical Reactions ◽  
Initial Conditions ◽  
The Other ◽  
Heat Transfer Analysis ◽  
Surface Deposition ◽  
Conflicting Evidence ◽  
Increasing Demand ◽  
The One

An increasing demand is being put on the fuel as a heat sink in modern aircraft. In the end, the fuel flows through the atomizer which on the one hand is the hottest part of its thermal history, but on the other hand the most critical for resisting deposition. Most studies have concentrated on the chemistry of deposition, and in recent years there have been modeling efforts. Deposition is really the end product of a coupling between heat transfer to the fuel, chemical reactions to form insoluble gums, followed by the transport of these gums to the surface to form deposits. There is conflicting evidence and theory in the literature concerning the effect of turbulence on deposition, i.e., whether deposition increases or decreases with increasing Reynolds number. This paper demonstrates through a heat transfer analysis that the effect of Reynolds number depends upon the boundary/initial conditions. If the flow is heated from the surface, deposition decreases with increasing Reynolds number; however, for isothermal flows, i.e., preheated, deposition will increase with Reynolds number.

Measurement of Condensation Curves for Dropwise Condensation of Steam at Atmospheric Pressure

1983 ◽  
Vol 105 (3) ◽  
pp. 633-638 ◽  
Author(s):  
I. Tanasawa ◽  
Y. Utaka
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Atmospheric Pressure ◽  
Heat Fluxes ◽  
Dropwise Condensation ◽  
Maximum Heat ◽  
Transfer Block ◽  
Peak Heat Flux ◽  
The One ◽  
The Heat Transfer Coefficient

Condensation curves for dropwise condensation of steam at atmospheric pressure were measured for the range of surface subcooling between 0.5 and 180 K using a heat transfer block having a concave spherical condensing surface. The heat transfer coefficient remained constant with the increase of surface subcooling up to about 10 K, and then it decreased. The maximum heat fluxes were found to be between 9.3 and 12.2 MW/m2. Dropwise condensation could be observed at a surface subcooling larger than the one corresponding to the peak heat flux, but shortly the mode of condensation shifted to pseudo-film or on-ice condensation.

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