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.

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.

Which One of Two Ectopic Mandibular Canines will erupt to a Normal Position in the Dental Arch

2018 ◽  
Author(s):  
M Svanholt ◽  
P Svanholt ◽  
Inger Kjær
Keyword(s):  
The Other ◽  
Mixed Dentition ◽  
Dental Arch ◽  
Horizontal Position ◽  
Normal Position ◽  
Initial Stage ◽  
Mandibular Canine ◽  
The One

The purpose of this paper is to demonstrate 4 cases with bi-lateral ectopic mandibular canines and to demonstrate in each case which one of the two canines erupted to a normal position in the dental arch. The canines are observed from Orthopantomograms from 4 children (aged 8-13 years of age) in the mixed dentitions stages. Of these children 2 were males and 2 were females. From each child there was between 3-5 Orthopantomograms. These were observed over 3-4 years period. In each of the 4 cases with bi-lateral ectopia of the mandibular canines the one mandibular canine erupted into a normal position, while the other one declined into a horizontal position during the mixed dentition period. These 4 cases demonstrated that the inclination of the canines were important to observe and diagnose from the initial stage (first ortopantomogram). The cases presented, demonstrated that the unsuccessfully erupted canines ending in a horizontal position, were the canines which inclined slightly more that the contra lateral canine already from the initial stage.

FORMATION OF THE GENRE OF THE STORY IN THE CHERKESS LITERATURE: IDELOGICAL GUIDES AND THEMATIC REFERENCES

Kavkazologiya ◽  
2021 ◽  
pp. 219-288
Author(s):  
M.A. KHAKUASHEVA ◽  
◽  
L.B. KHAVZHOKOVA ◽  
Keyword(s):  
The Other ◽  
North Caucasus ◽  
Research Attention ◽  
The North ◽  
Initial Stage ◽  
Great Patriotic War ◽  
History Of ◽  
Formation And Evolution ◽  
The One ◽  
Artistic Analysis

The article examines some of the issues of the formation and evolution of the genre of the story in Circassian literature. The relevance of the study is due, on the one hand, to the insufficient development of the stated topic, on the other hand, to the need to identify trends in the development of national prose, starting from the problems of its genesis. In the center of research attention is the ideological and thematic orientation of the Circassian story mainly of the initial stage of evolution, i.e. Soviet era. In particular, the author examines the stories of S. Temirov, I. Amirokov, M. Adamokov, H. Gashokov and others, who laid the foundations of the genre in Circassian literature. During the indicated period, the Circassian tale was the first attempt to comprehend the problems of collective farms, youth brigades, the Soviet attitude to work, the range of urgent problems of young people, their aspirations, the formation of the criteria of Soviet morality. It also reflects various aspects of the Great Patriotic War, mainly as a war for independence. The research uses the method of artistic analysis. The results obtained can be used in compiling special courses on Adyghe (Kabardino-Circassian) prose, writing the history of the literature of the peoples of the North Caucasus.

Heat transfer analysis of a ventilated room with a porous partition: LB-MRT simulations

2020 ◽  
Vol 91 (2) ◽  
pp. 20904
Author(s):  
Zouhira Hireche ◽  
Lyes Nasseri ◽  
Djamel Eddine Ameziani
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Natural Convection ◽  
Reynolds Numbers ◽  
Darcy Number ◽  
The Other ◽  
Flow In Porous Media ◽  
Heat Transfer Analysis ◽  
Maximum Deviation ◽  
Important Conclusion

This article presents the hydrodynamic and thermal characteristics of transfers by forced, mixed and natural convection in a room ventilated by air displacement. The main objective is to study the effect of a porous partition on the heat transfer and therefore the thermal comfort in the room. The fluid flow future in the cavity and the heat transfer rate on the active wall have been analyzed for different permeabilities: 10−6 ≤ Da ≤ 10. The other control parameters are obviously, the Rayleigh number and the Reynolds number varied in the rows: 10 ≤ Ra ≤ 106 and 50 ≤ Re ≤ 500 respectively. The transfer equations write were solved by the Lattice Boltzmann Multiple Relaxation Time method. For flow in porous media an additional term is added in the standard LB equations, to consider the effect of the porous media, based on the generalized model, the Brinkman-Forchheimer-extended Darcy model. The most important conclusion is that the Darcian regime start for small Darcy number Da < 10−4. Spatial competition between natural convection cell and forced convection movement is observed as Ra and Re rise. The effect of Darcy number values and the height of the porous layer is barely visible with a maximum deviation less than 7% over the ranges considered. Note that the natural convection regime is never reached for low Reynolds numbers. For this Re values the cooperating natural convection only improves transfers by around 10% while, for the other Reynolds numbers the improvement in transfers due to natural and forced convections cooperation is more significant.

Validation Experiment for the Cooling Capability of Passive Auxiliary Feedwater System (PAFS) With PASCAL Facility

2012 ◽  
Author(s):  
Byoung-Uhn Bae ◽  
Seok Kim ◽  
Yu-Sun Park ◽  
Bok-Deuk Kim ◽  
Kyoung-Ho Kang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Exchanger ◽  
System Analysis ◽  
Thermal Power ◽  
Heat Removal ◽  
Steady State Condition ◽  
Single Tube ◽  
Decay Heat ◽  
Validation Experiment

The Passive Auxiliary Feedwater System (PAFS) is one of the advanced safety features adopted in the APR+ (Advanced Power Reactor Plus) which is intended to completely replace the conventional active auxiliary feedwater system. It removes the decay heat by cooling down the secondary system of the SG using condensation heat exchanger installed in the Passive Condensation Cooling Tank (PCCT). With an aim of validating the cooling and operational performance of the PAFS, PASCAL (PAFS Condensing Heat Removal Assessment Loop), was constructed to experimentally investigate the condensation heat transfer and natural convection phenomena in the PAFS. It simulates a single tube of the passive condensation heat exchangers, a steam-supply line, a return-water line, and a PCCT with a reduced area, which is equivalent to 1/240 of the prototype according to a volumetric scaling methodology with a full height. The objective of the experiment is to investigate the cooling performance and natural circulation characteristics of the PAFS by simulating a steady state condition of the thermal power. From the experiment, two-phase flow phenomena in the horizontal heat exchanger and PCCT were investigated and the cooling capability of the condensation heat exchanger was validated. Test results showed that the design of the condensation heat exchanger in PAFS could satisfy the requirement for heat removal rate of 540 kW per a single tube and the prevention of water hammer phenomenon inside the tube. It also proved that the operation of PAFS played an important role in cooling down the decay heat by natural convection without any active system. The present experimental results will contribute to improve the model of the condensation and boiling heat transfer, and also to provide the benchmark data for validating the calculation performance of a thermal hydraulic system analysis code with respect to the PAFS.

Natural Convective Flow and Heat Transfer in a Collector Storage with an Immersed Heat Exchanger: Numerical Study

2005 ◽  
Vol 127 (3) ◽  
pp. 324-332 ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Storage System ◽  
Fluid Motion ◽  
Heat Transfer Process ◽  
Strong Mixing ◽  
Scale Analysis ◽  
Three Dimensional Model

A three-dimensional model and dimensionless scale analysis of the transient fluid dynamics and heat transfer in an inclined adiabatic water-filled enclosure with an immersed cylindrical cold sink is presented. The geometry represents an integral collector storage system with an immersed heat exchanger. The modeled enclosure has an aspect ratio of 6:1 and is inclined at 30deg to the horizontal. The heat exchanger is represented by a constant surface temperature horizontal cylinder positioned near the top of the enclosure. A scale analysis of the transient heat transfer process identifies four temporal periods: conduction, quasi-steady, fluctuating, and decay. It also provides general formulations for the transient Nusselt number, and volume-averaged water temperature in the enclosure. Insight to the transient fluid and thermal processes is provided by presentation of instantaneous flow streamlines and isotherm contours during each transient period. The flow field consists of two distinct zones. The zone above the cold sink is nearly stagnant. The larger zone below the sink is one of strong mixing and recirculation initiated by the cold plume formed in the boundary layer of the cylindrical sink. Correlations for the transient Nusselt number and the dimensionless volume-averaged tank temperature predicted from the model compare favorably to prior measured data. Fluid motion in the enclosure enhances heat transfer compared to that of a cylinder in an unbounded fluid.

Numerical Study on Near-Wall Natural Convection Over a Microscale Heating Wire

2012 ◽  
Author(s):  
Leping Zhou ◽  
Yunfang Zhang ◽  
Lijun Yang ◽  
Xiaoze Du ◽  
Minami Yoda ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Heat Transfer Process ◽  
Brownian Diffusion ◽  
Wall Region ◽  
Two Phase ◽  
Heating Wire ◽  
Transfer Problems ◽  
Near Wall

The study of the natural convection over a very small heat sources is important in the analysis of heat transfer problems in the electronics industry. However, the characteristics of the spatial distribution of the velocity in the near wall region, which is crucial to the mechanisms of heat transfer process in natural convection around a microscale object, is not well understood. In this investigation, the microscale natural convection in the near wall region of a platinum micro heat source was investigated numerically, using FLUENT, a commercially available computational fluid dynamics (CFD) software, and compared with corresponding experimental results. The influence of the nanoparticles on the natural convection was observed using the single-phase or two-phase models available in FLUENT. The temperature and velocity fields were obtained, with which the Brownian diffusion coefficient was deduced. The results indicate that the temperature gradient induced Brownian diffusion and thermophoresis in the near wall region plays an important role in the microscale natural convection in the water/nanoparticle mixture investigated and are in good agreement with the results from a corresponding experimental investigation.

Numerical Heat Transfer Analysis of Flake Ice Storage System with Nanofluids

2012 ◽  
Vol 433-440 ◽  
pp. 2716-2720
Author(s):  
Jing De Zhao ◽  
Ni Liu ◽  
Yi Wang
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Storage System ◽  
Heat Transfer Analysis ◽  
Ice Storage ◽  
Electrical Load ◽  
Unsteady Heat Transfer ◽  
Numerical Heat Transfer

Ice Storage air-condition can be used to shift electrical load from on-peak hours to off-peak hours, which can bring mutual benefits to power supplier and consumers. An unsteady heat transfer numerical model is developed to predict the increment of thickness of ice layer of flake ice storage system with Cu-H2O nanofluids solidification. In this study, the speed of increment of ice layer of water and Cu-H2O nanofluids are compared.

Effect of Natural Convection on Thermal Energy Storage in Supercritical Fluids

2013 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
Adrienne S. Lavine ◽  
H. Pirouz Kavehpour ◽  
Gani B. Ganapathi ◽  
Richard E. Wirz
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Energy Storage ◽  
Supercritical Fluid ◽  
Supercritical Fluids ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Thermal Storage

Heat transfer to the storage fluid is a critical subject in thermal energy storage systems. The storage fluids that are proposed for supercritical thermal storage system are organic fluids that have poor thermal conductivity; therefore, pure conduction will not be an efficient heat transfer mechanism for the system. The current study concerns a supercritical thermal energy storage system consisting of horizontal tubes filled with a supercritical fluid. The results of this study show that the heat transfer to the supercritical fluid is highly dominated by natural convection. The buoyancy-driven flow inside the storage tubes dominates the flow field and enhances the heat transfer dramatically. Depending on the diameter of the storage tube, the buoyancy-driven flow may be laminar or turbulent. The natural convection has a significant effect on reducing the charge time compared to pure conduction. It was concluded that although the thermal conductivity of the organic supercritical fluids are relatively low, the effective laminar or turbulent natural convection compensates for this deficiency and enables the supercritical thermal storage to charge effectively.

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