scholarly journals Heat transfer by seepage in sand: Influence of saturated hydraulic conductivity and porosity

2021 ◽  
pp. 61-75
Author(s):  
Yaser Ghafoori ◽  
Matej Maček ◽  
Andrej Vidmar ◽  
Jaromír Říha ◽  
Andrej Kryžanowski
Keyword(s):  
Heat Transfer ◽  
Hydraulic Conductivity ◽  
Initial Conditions ◽  
Numerical Models ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Seepage Flow ◽  
Heat Transfer Process ◽  
Saturated Hydraulic Conductivity ◽  
Distributed Temperature Sensor

Heat transfer within the soil is a complex process in the presence of seepage flow. In such conditions, the soil’s thermal behavior is influenced by the thermal and hydraulic properties of the medium as well as the initial conditions and boundary conditions to which the medium is subjected. This paper presents the experimental and numerical studies of heat transfer within the sand subjected to the seepage flow. It focuses on the influence of saturated hydraulic conductivity and the porosity of medium on the heat transfer process. The temperature distribution within the sand was monitored by the optical fiber Distributed Temperature Sensor (DTS). The experiment was performed on three types of silica-dominated sands with different saturated hydraulic conductivities and different Soil Water Characteristic Curve (SWCC). In addition to the experimental study, a coupled hydrothermal numerical model was designed in FEFLOW software and validated by comparing its results with the experimental measurements. To determine the influence of porosity and saturated hydraulic conductivity on heat transfer, we analyzed the numerical models for different values of porosity and saturated hydraulic conductivity. The numerical and experimental studies showed that the thermal velocity is higher in sand with higher saturated hydraulic conductivity and temperature declination occurs more quickly due to the heat convection process. Saturated sand with larger porosity has an overall higher heat capacity, wherefore the temperature declination started later in the measuring points but dropped down lower close to the temperature of the upstream water.

scholarly journals Experimental study of heat transfer through cooling water circuit in a reactor vault by using Al2O3 nano fluid

2018 ◽  
Vol 22 (2) ◽  
pp. 1149-1161 ◽  
Author(s):  
Maria Anish ◽  
Balakrishnan Kanimozh
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Base Fluid ◽  
Nuclear Reactor ◽  
Characteristic Curve ◽  
Reactor Core ◽  
Cooling Water ◽  
Heat Transfer Process ◽  
Nano Fluid ◽  
Al2o3 Nanoparticle

The heat produced in the nuclear reactor due to fission reaction must be kept in control or else it will damage the components in the reactor core. Nuclear plants are using water for the operation dissipation of heat. Instead, some chemical substances which have higher heat transfer coefficient and high thermal conductivity. This experiment aims to find out how efficiently a nanofluid can dissipate heat from the reactor vault. The most commonly used nanofluid is Al2O3 nanoparticle with water or ethylene as base fluid. The Al2O3 has good thermal property and it is easily available. In addition, it can be stabilized in various PH levels. The nanofluid is fed into the reactor?s coolant circuit. The various temperature distribution leads to different characteristic curve that occurs on various valve condition leading to a detailed study on how temperature distribution carries throughout the cooling circuit. As a combination of Al2O3 as a nanoparticle and therminol 55 as base fluid are used for the heat transfer process. The Al2O3 nanoparticle is mixed in therminol 55 at 0.05 vol.% concentration. Numerical analysis on the reactor vault model was carried out by using ABAQUS and the experimental results were compared with numerical results.

Experimental studies of the propagation of combustion in solids

1992 ◽  
Vol 339 (1654) ◽  
pp. 387-394 ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Steady State ◽  
Chemical Kinetics ◽  
Profile Analysis ◽  
Numerical Models ◽  
Experimental Studies ◽  
Dimensional Model ◽  
Thermal Methods ◽  
One Dimensional

The application of thermal methods to the study of steady-state combustion is described. Such methods provide a route to information on heat transfer and chemical kinetics which forms a basis for the implementation of numerical models. The experimental results from thermal analysis and temperature profile analysis have been examined within the context of a simple pseudo one-dimensional model of propagation offering some confirmation of the validity of the approach.

Research on Heat-Transfer Process of the Radiant Ceiling Cooling System

2012 ◽  
Vol 512-515 ◽  
pp. 2171-2174 ◽  
Author(s):  
Quan Ying Yan ◽  
Ran Huo ◽  
Li Li Jin
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Cooling System ◽  
Numerical Models ◽  
Cooling Water ◽  
Lower Surface ◽  
Cooling Capacity ◽  
Heat Transfer Process ◽  
Lower Surface Temperature ◽  
Selection Of

Physical and numerical models of the radiant ceiling cooling system were built and numerically simulated. The results showed that the lower the temperature of cooling water is, the lower surface temperature the ceiling has, and the bigger the cooling capacity is. The bigger the depth of tubes is, the higher the surface temperature and the smaller the cooling capacity. The differences are not evident. The bigger the distance of tubes is, the bigger the surface temperature is and the smaller the cooling capacity is. The diameter of tubes has a few influences on the surface temperature and the cooling capacity. Results in this paper can provide basis and guide for the design of the project, the selection of parameters and the feasibility of the system.

COMPARISON OF METHODS FOR DETERMINING SATURATED HYDRAULIC CONDUCTIVITY AND DRAINABLE POROSITY OF TWO SOUTHERN ALBERTA SOILS

1986 ◽  
Vol 66 (2) ◽  
pp. 249-259 ◽  
Author(s):  
G. D. BUCKLAND ◽  
D. B. HARKER ◽  
T. G. SOMMERFELDT
Keyword(s):  
Soil Moisture ◽  
Hydraulic Conductivity ◽  
Characteristic Curve ◽  
Subsurface Drainage ◽  
Saturated Hydraulic Conductivity ◽  
Drainage Design ◽  
Moisture Characteristic ◽  
Constant Head ◽  
Subsurface Drains ◽  
Drainable Porosity

Saturated hydraulic conductivity (Ks) and drainable porosity (f) determined by different methods and for different depths were compared with those determined from the performance of drainage systems installed at two locations. These comparisons were made to determine which methods are suitable for use in subsurface drainage design. Auger hole and constant-head well permeameter Ks were 140 and 110%, respectively, of Ks determined from subsurface drains. Agreement of horizontal or vertical Ks, from in situ falling-head permeameters; to other methods was satisfactory providing sample numbers were large. Ks by Tempe cells was only 3–10% of drain Ks and in one instance was significantly lower than Ks determined by all other methods. At one site a profile-averaged value of f determined from the soil moisture characteristic curve (0–5 kPa) of semidisturbed cores agreed with that determined from drainage trials. At the other site, a satisfactory value of f was found only when the zone in which the water table fluctuated was considered. Results indicate that Ks determined by the auger hole and constant-head well permeameter methods, and f determined from the soil moisture characteristic curve of semidisturbed cores, are sufficiently reliable and practical for subsurface drainage design. Key words: Subsurface drainage, hydraulic conductivity, drainable porosity

scholarly journals One-dimensional large-strain thaw consolidation using nonlinear effective stress – void ratio – hydraulic conductivity relationships

2018 ◽  
Vol 55 (3) ◽  
pp. 414-426 ◽  
Author(s):  
Simon Dumais ◽  
Jean-Marie Konrad
Keyword(s):  
Heat Transfer ◽  
Hydraulic Conductivity ◽  
Effective Stress ◽  
Void Ratio ◽  
Moving Boundary ◽  
Initial Conditions ◽  
Large Strain ◽  
One Dimensional ◽  
Consolidation Theory ◽  
Thaw Consolidation

A one-dimensional model for the consolidation of thawing soils is formulated in terms of large-strain consolidation and heat-transfer equations. The model integrates heat transfer due to conduction, phase change, and advection. The hydromechanical behaviour is modelled by large-strain consolidation theory. The equations are coupled in a moving boundary scheme developed in Lagrangian coordinates. Finite strains are allowed and nonlinear effective stress – void ratio – hydraulic conductivity relationships are proposed to characterize the thawing soil properties. Initial conditions and boundary conditions are presented with special consideration for the moving boundary condition at the thaw front developed in terms of large-strain consolidation. The proposed model is applied and compared with small-strain thaw consolidation theory in a theoretical working example of a thawing fine-grained soil sample. The modelling results are presented in terms of temperature, thaw penetration, settlements, void ratio, and excess pore-water pressures.

Numerical Investigation of Impingement Heat Transfer Enhancement on a Flat Plate with an Attached Porous Medium

2011 ◽  
Vol 312-315 ◽  
pp. 477-482 ◽  
Author(s):  
Pey Shey Wu ◽  
Yi Wen Lo ◽  
Fong Chia Cheng
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Flat Plate ◽  
Numerical Models ◽  
Thick Layer ◽  
Jet Impingement ◽  
Heat Transfer Process ◽  
Heated Plate ◽  
Impingement Heat Transfer ◽  
Hole Geometry

The enhancement of impingement heat transfer on a flat plate covered with a thick layer of porous medium with or without a center hole was numerically investigated. The renormalization group turbulence model is selected for the fluid region while Forchheimer extended Darcy’s model is used for porous region. The numerical models were justified by comparisons with available experimental data. Computational results show that an attached porous medium with a center hole can effectively enhance jet impingement heat transfer while an attached thick porous layer without a center hole has detrimental effect. The physics of these results are supported and well explained by the detailed flow patterns. The most influential parameters in this heat transfer process include the jet Reynolds number and the center hole geometry (hole depth and jet-to-hole diameter ratio). A good hole geometry should well trap the jet and direct the coolant along the heated plate.

scholarly journals Experimental studies and mathematical modeling on the effects of rapid airflow and baking temperature during baking

2020 ◽  
pp. 469
Author(s):  
Mazidah Mior Zakuan Azmi ◽  
Anvarjon Ahmedov ◽  
Farah Saleena Taip
Keyword(s):  
Heat Transfer ◽  
Volume Expansion ◽  
Numerical Models ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Transfer Model ◽  
Temperature Profiles ◽  
Convection Oven ◽  
Baking Process ◽  
Cake Baking

Rapid airflow in oven will influence the heat transfer in baking process therefore the purpose of this study is to experimentally and numerically investigate the effects of operating conditions on the heat transfer mechanism and volume expansion during baking. Cakes are baked in an air fryer and convection oven with constant speed 5.11 m/s and 0.88 m/s respectively at 150, 160, 170 °C in different baking times. A heat transfer model was defined to describe the influence of baking temperature on internal cake temperature by Fourier’s law. It was observed that the presence of rapid airflow (air fryer) and increment in oven temperature yielded an increase in volume expansion but produced a less moist product. Cakes baked in the presence of rapid airflow at 150 °C were moister but with little volume expansion in the cakes compared to convection oven-baked cakes. Significant correlation between the numerical models with experimental temperature profiles were recorded during complete cake baking process.

scholarly journals Actual problems of the thermal hydraulic reliability ensuring of prospective nuclear reactors with supercritical parameters

2021 ◽  
Vol 20 ◽  
pp. 27-38
Author(s):  
I. G. Sharayevsky ◽  
◽  
N. M. Fialko ◽  
A. V. Nosovskyi ◽  
L. B. Zimin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermodynamic Parameters ◽  
Experimental Studies ◽  
Heat Removal ◽  
Heat Transfer Process ◽  
Critical Area ◽  
Water Coolant ◽  
Operational Parameters ◽  
Reliable Determination ◽  
Light Water

There is a significant lack of reliable information on the physical characteristics of thermohydraulic processes in emergency heat transfer modes when cooling the surface of fuel rods with light water coolant with supercritical thermodynamic parameters, in particular, on the physics of heat transfer processes and hydromechanics in the critical area. It is shown that in these conditions there is physical uncertainty about the causes of deteriorating heat transfer, which limits the possibility of creating effective calculation techniques for reliable determination of the upper limit of safe forcing of the heat transfer process in the core. At present, the vast majority of theoretical and experimental studies of thermohydraulic processes in the near-critical area have been performed only for the socalled “normal” heat transfer, which corresponds to the heat removal conditions with mixed turbulent convection of superheated to “gas” state of light water coolant in its inertial mode. Attention is paid to the possible appearance of macromolecular ensembles on this surface in the form of pseudo-vapor formations, which are capable of causing an emergency mode of pseudo-film boiling. On the basis of the given experimental data of various authors existence of rather deep physical analogy between processes of heat exchange in supercritical thermodynamic system and unheated boiling at subcritical parameters of the heat carrier is proved. Existence of the pseudo-boiling process in the conditions of supercritical thermodynamic parameters makes it impossible to use in the thermohydraulic calculation the empirical dependences for “hot” gas for the range of active zones operational parameters.

scholarly journals Heat Transfer Modeling in Bone Tumour Hyperthermia Induced by Hydroxyapatite Magnetic Thermo-Seeds

2020 ◽  
Vol 14 (1) ◽  
pp. 77-89
Author(s):  
Fabio Fanari ◽  
Lorena Mariani ◽  
Francesco Desogus
Keyword(s):  
Heat Transfer ◽  
Numerical Models ◽  
Bone Tumour ◽  
Heat Transfer Process ◽  
Thermal Treatments ◽  
Hyperthermia Treatment ◽  
Theoretical Frameworks ◽  
Thermal Dynamics ◽  
Electromagnetic Power ◽  
Proposed Model

Background: Hyperthermia is an adjuvant oncologic thermal therapy. In the case of deep-seated bone cancers, the interstitial hyperthermia treatment can be performed using thermo-seeds, implanted biomaterial components that are able to convert external electromagnetic power into thermal one. Several magnetic biomaterials have been synthesized for thermal treatments of cancer. However, less attention has been paid to the modeling description of the therapy, especially when the bio-heat transfer process is coupled to the electromagnetic heating. Objective: In this work, a comparison between the available analytical and numerical models is presented. Methods: A non-linear multiphysics model is used to study and describe the performance of cylindrical magnetic hydroxyapatite thermo-seeds to treat residual cancer cells of bone tumours. Results: The thermal dynamics and treatment outcome are carefully evaluated. Under the exposure of a magnetic field of 30 mT, working at 300 kHz, it was found that magnetic hydroxyapatite implants with a size of 10 mm × 10 mm could increase the temperature above 42 °C for 60 min. Conclusion: The proposed model overcomes the limitations of the available theoretical frameworks, and the results reveal the relevancy of the implant geometry to the effectiveness of the hyperthermia treatment.

scholarly journals Modeling of the heat transfer process in an air heat pump fanless evaporator

2018 ◽  
Vol 240 ◽  
pp. 05012
Author(s):  
Piotr Kopeć ◽  
Beata Niezgoda-Żelasko
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Mixed Convection ◽  
Heat Pump ◽  
Transfer Process ◽  
Experimental Studies ◽  
Heat Transfer Process ◽  
Cfd Modeling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

This paper analyses the mixed convection process in a fanless evaporator of an air heat pump. The text of the paper shows the authors’ experimental studies results of the temperature distribution and the local values of heat transfer coefficients on the outer surface of vertical tubes with longitudinal fins for the case of mixed convection and fins of a specific shape of their cross-section (prismatic, wavy fins). The experimental studies include the air velocities wa=2,3 m/s and the temperature differences between air and the refrigerant inside the heat exchanger tubes which is ΔT=24-40K. The results obtained were used for verification of CFD modeling of the heat transfer process for the discussed case of heat transfer and the geometry of the finned surface. The numerical analysis was performed for: the temperature distribution along the fin height, the tube perimeter and height, the distribution of local heat transfer coefficients on the finned tube perimeter and along its height. The simulated calculations were used to verify the method of determination of fin efficiency.

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