Direct simulation of thermally and mechanically coupled particle-laden flow

SIMULATION ◽  
2021 ◽  
pp. 003754972110551
Author(s):  
Laurie A Florio
Keyword(s):  
Heat Transfer ◽  
Solid Body ◽  
Volume Fraction ◽  
Learning Algorithm ◽  
Thermal Conditions ◽  
Solid Surfaces ◽  
Transfer Coefficients ◽  
Flow Paths ◽  
Local Flow ◽  
Property Variation

This work describes a unique technique to simulate continuously and directly coupled fluid flow and moving particles including both mechanical and thermal interactions between the flow, particles, and flow paths. The particles/flow paths are discretized within a computational fluid dynamics flow domain so that the local flow and temperature field conditions surrounding each particle or other solid body are known along with the local temperature distribution within the particle and other solids. Contact conduction between solid bodies including contact resistance, conjugate heat transfer at the fluid–solid interfaces, and even radiation exchanges between solid surfaces and between solid surfaces and the fluid are incorporated in the thermal interactions and a soft collision model simulates the solid body mechanical contact. The ability to capture these local flow and thermal effects removes reliance on correlations for fluid forces and for heat transfer coefficients/exchange and removes restrictions on the flow regime and particle size and volume fraction considered. Larger particle sizes and higher particle concentration conditions can be studied with local effects captured. The method was tested for a range of particle thermal and mechanical properties, driving pressures, and for limited radiation parameters. The results reveal important information about the basic thermal and flow phenomena that cannot be obtained in standard modeling methods and demonstrate the utility of the modeling method. The technique can be applied to examine phenomena dependent on local thermal conditions such as chemical reactions, material property variation, agglomerate formation, and phase change. The methods can also be used as a basis for machine learning algorithm development for flows with large particle counts so that more detailed phenomena can be considered compared to those provided by standard techniques with reduced computational costs compared to those with fully resolved particles in the flow.

scholarly journals Heat Transfer Boundary Conditions in the RELAP5-3D Code

2008 ◽  
Author(s):  
Richard A. Riemke ◽  
Cliff B. Davis ◽  
Richard R. Schultz
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Surface Temperature ◽  
Volume Fraction ◽  
Control Variable ◽  
Time Dependent ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
General Table

The heat transfer boundary conditions used in the RELAP5-3D computer program have evolved over the years. Currently, RELAP5-3D has the following options for the heat transfer boundary conditions: (a) heat transfer correlation package option, (b) non-convective option (from radiation/conduction enclosure model or symmetry/insulated conditions), and (c) other options (setting the surface temperature to a volume fraction averaged fluid temperature of the boundary volume, obtaining the surface temperature from a control variable, obtaining the surface temperature from a time-dependent general table, obtaining the heat flux from a time-dependent general table, or obtaining heat transfer coefficients from either a time- or temperature-dependent general table). These options will be discussed, including the more recent ones.

Two-Phase Pressure Drop and Boiling Heat Transfer in a Single Horizontal Microchannel

2006 ◽  
Author(s):  
Cheol Huh ◽  
Moo Hwan Kim
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Local Flow ◽  
Heat Transfer Coefficients ◽  
Phase Pressure

With a single microchannel and a series of microheaters made with MEMS technique, two-phase pressure drop and local flow boiling heat transfer were investigated using deionized water in a single horizontal rectangular microchannel. The test microchannel has a hydraulic diameter of 100 μm and length of 40 mm. A real time observation of the flow patterns with simultaneous measurement are made possible. Tests are performed for mass fluxes of 90, 169, and 267 kg/m2s and heat fluxes of from 100 to 600 kW/m2. The experimental local flow boiling heat transfer coefficients and two-phase frictional pressure gradient are evaluated and the effects of heat flux, mass flux, and vapor qualities on flow boiling are studied. Both the evaluated experimental data are compared with existing correlations. The experimental heat transfer coefficients are nearly independent on mass flux and the vapor quality. Most of all correlations do not provide reliable heat transfer coefficients predictions with vapor quality and prediction accuracy. As for two-phase pressure drop, the measured pressure drop increases with the mass flux and heat flux. Most of all existing correlations of two-phase frictional pressure gradient do not predict the experimental data except some limited conditions.

Developing Turbulent Flow and Heat Transfer in Concentric Annuli

1972 ◽  
Vol 1 (1) ◽  
pp. 13-24
Author(s):  
Y. Lee ◽  
S.D. Park
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Thermal Conditions ◽  
Eddy Diffusivity ◽  
Gas Flows ◽  
Local Flow ◽  
Number Range ◽  
Starting Position ◽  
Eddy Diffusivities ◽  
Flow And Heat Transfer

The problem of the simultaneously developing turbulent flow and heat transfer in concentric annuli was studied from an integral viewpoint, based on a modified model for the eddy diffusivity of momentum together with a new ratio of eddy diffusivities obtained from experiment. Solutions were obtained for one surface uniformly heated and the other insulated. The analytical results were then compared with the measurement of local flow and thermal conditions for air flow through four concentric annuli for a Reynolds number range of about 20,000 to 110,000. The analysis assumed the flow was turbulent everywhere. In the experimental work the flow was tripped at the starting position of both the velocity and thermal boundary layers. Air was chosen in the experiment as it represents gas flows in general.

scholarly journals CONVECTIVE HEAT TRANSFER CHARACTERISTICS OF AQUEOUS TiO2 NANOFLUID UNDER LAMINAR FLOW CONDITIONS

2008 ◽  
Vol 07 (06) ◽  
pp. 325-331 ◽  
Author(s):  
S. M. SOHEL MURSHED ◽  
KAI CHOONG LEONG ◽  
CHUN YANG ◽  
NAM-TRUNG NGUYEN
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Enhancement Of Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Constant Wall Heat Flux

This paper reports an experimental investigation into force convective heat transfer of nanofluids flowing through a cylindrical minichannel under laminar flow and constant wall heat flux conditions. Sample nanofluids were prepared by dispersing different volumetric concentrations (0.2–0.8%) of nanoparticles in deionized water. The results showed that both the convective heat transfer coefficient and the Nusselt number of the nanofluid increase considerably with the nanoparticle volume fraction as well as the Reynolds number. Along with the enhanced thermal conductivity of nanofluids, the migration, interactions, and Brownian motion of nanoparticles and the resulting disturbance of the boundary layer are responsible for the observed enhancement of heat transfer coefficients of nanofluids.

Heat Transfer to Supercritical Water in Smooth-Bore Tubes

1965 ◽  
Vol 87 (4) ◽  
pp. 477-483 ◽  
Author(s):  
H. S. Swenson ◽  
J. R. Carver ◽  
C. R. Kakarala
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Supercritical Water ◽  
Convection Heat Transfer ◽  
Physical Property ◽  
Transfer Coefficients ◽  
Property Variation ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
Data Points

Local forced convection heat-transfer coefficients for supercritical water flowing inside smooth-bore tubes were obtained experimentally over a range of pressures (3300 to 6000 psia) and bulk temperatures (167 to 1068 F). Because the thermophysical properties of supercritical fluids change rapidly with temperature in the pseudocritical range, conventional forced convection correlations were unable to fit the data. However, a satisfactory correlation for fully developed turbulent flow was obtained by properly modifying the conventional nondimensional model to account for the physical property variation across the boundary layer. Out of 2951 data points, 95 percent lie within ±15 percent of the correlation. It was also found that the same equation correlated supercritical pressure heat-transfer data of carbon dioxide over a wide range of conditions with good accuracy.

scholarly journals Flow Characteristic and Heat Transfer for Non-Newtonian Nanofluid in Rectangular Microchannels with Teardrop Dimples/Protrusions

Open Physics ◽  
2017 ◽  
Vol 15 (1) ◽  
pp. 197-206 ◽  
Author(s):  
Zheyuan Zhang ◽  
Yonghui Xie ◽  
Di Zhang ◽  
Gongnan Xie
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Flow Characteristics ◽  
Relative Depth ◽  
Microchannel Heat Sink ◽  
Local Flow ◽  
Flow And Heat Transfer ◽  
Fanning Friction Factor ◽  
Limiting Streamlines

AbstractPorous cavity technology is one of the effective ways to improve local flow structures and thus the overall heat transfer of heat exchanging devices. In the present investigation, the flow characteristics and heat transfer in a microchannel heat sink with teardrop dimples/protrusions are studied with a numerical method. The working substances are Al2O3-water nanofluids, which are defined by power-law shear-thinning model. The relative depth and positive eccentricity of dimples/protrusions arranged in the microchannels are 0.2 and 0.3 respectively. The inlet velocity varies in the range of 1.41 m⋅s−1to 8.69 m⋅s−1and the volume fraction ranges from 0.5% to 3.5%. The effects of the flow and heat transfer characteristics are investigated by analyzing the limiting streamlines structures and temperature distributions. The overall thermal performance is evaluated by parameters of Fanning friction factor, Nusselt number and thermal performance. It is shown that the combination of teardrop dimple/protrusion structure and Al2O3-water nanofluids could effectively strengthen heat transfer with low pressure loss. Moreover, in order to obtain the best overall thermal performance, working substances with volume faction of 3.5% is preferred for the proposed microchannel structure.

scholarly journals Thermal modes simulation of cooling panels in waste water pumping stations

Vestnik MGSU ◽  
2021 ◽  
pp. 1378-1387
Author(s):  
Vitaly I. Prohorov ◽  
Muhammet A. Razakov
Keyword(s):  
Waste Water ◽  
Heat Transfer ◽  
Mathematical Model ◽  
Thermal Conditions ◽  
Engineering Calculation ◽  
Transfer Coefficients ◽  
Pumping Station ◽  
Heat Transfer Coefficients ◽  
Water Pumping ◽  
Functional Areas

Introduction. Authors considers a new method of cooling some functional areas in a city sewage pumping station. They have used the works of Isachenko V.A., Osipov V.A., Sukomel A.S., Bogoslovsky V.N. to simulate the PLI panel’s stationary thermal regime. Materials and methods. Authors have considered the mathematical modeling of stationary and non-stationary thermal phenomena in the PLI panel in this paper. There are the possibilities of modeling the thermal modes of the panel PLI which depending on the place of installation of this device. Authors have given the theoretical characteristics of the heated air in this device and some results of survey in a high voltage urban waste water pumping station in Moscow. There are the heat inputs and heat losses calculations of PLI panel’s various structural elements which carried out using the theory of similarity in this article. Researchers considered the possibility of use other empirical results to determine some of the coefficients which involved in modeling. It has been presented different heat transfer coefficients which could be used in thermal conditions model of PLI panel. There are the validation of the developed models which proved by comparing the deviations in the heat balance equation of the PLI panel. Results. Authors has developed a physical and mathematical model of PLI panel’s thermal modes for a sewage pimping station. Authors have given the recommendations on the possibility of using the different heat transfer coefficients in PLI panel’s thermal conditions modeling process. A numerical experiment was carried out to simulate one PLI panel under the conditions of a sewage pumping station by researchers in this paper. Conclusions. According to the information, this physical and mathematical model can be used for engineering calculation when engineer is selecting the characteristics of PLI panel and also it could be used to clarifying the distributions of heat flow from PLI panel.

Anomalous Enhancement of Heat Transfer to H2O/CO2 Mixtures in Near-Critical Region

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Hanlin Zhang ◽  
Haomin Wu ◽  
Sha Li ◽  
Dong Liu ◽  
Qiang Li
Keyword(s):  
Heat Transfer ◽  
Critical Point ◽  
Heat Transfer Enhancement ◽  
Convection Heat Transfer ◽  
High Mass ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Property Variation ◽  
Mass Fractions ◽  
Efficient Heat Transfer

Abstract Heat transfer to supercritical H2O/CO2 mixtures (24 MPa, 310 to 430 °C, and CO2 mass fractions up to 18.5%), the working fluids of a novel power generation system with coal gasified in supercritical water, was experimentally investigated for typical working conditions of this system. For these conditions, i.e., high mass velocities (above 1200 kg m−2 s−1) and low heat flux (below 300 kW m−2), the convection heat transfer coefficients (HTCs) of supercritical pure fluids usually increase with temperature, peak near the pseudo-critical point, i.e., heat transfer enhancement, and then decrease for higher temperatures. Here, we experimentally demonstrated a new heat transfer enhancement phenomenon for supercritical H2O/CO2 mixtures. A high-temperature and high-pressure apparatus was setup to measure the convection HTCs of the supercritical H2O/CO2 mixtures. Experimental results show that surprisingly two distinct peaks of convection HTCs appear, with one corresponding temperature being the pseudo-critical point of the H2O/CO2 mixture, i.e., the thermophysical property variation induced mechanism, and the other one being the critical miscible point of the mixture, i.e., the dissolution-induced mechanism. These results pave the way to efficient heat transfer devices that use supercritical mixtures as heat transfer fluids.

Numerical Study on the Mechanism of Heat Transfer Enhancement in Fe3O4 Nanoferrofluids With Magnetic Field

2019 ◽  
Author(s):  
Chenfei Wang ◽  
Dongdong Gao ◽  
Minli Bai ◽  
Peng Wang ◽  
Yubai Li
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Fe3o4 Nanoparticles ◽  
Volume Fraction ◽  
Numerical Study ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Enhancement Of Heat Transfer

Abstract Nanofluids is reported to significantly enhance heat transfer but with little cost of pressure loss. To further the enhancement of heat transfer using Fe3O4 nanofluids, a magnetic field is employed to control the trajectory of Fe3O4 nanoparticles. A numerical study is conducted with commercial soft ANSYS FLUENT and the simulations are done with a two-phase flow approach named Euler-Lagrange. By comparing heat transfer of laminar flow in a horizontal tube with magnetic field or not, various volume fraction (0.5%/2%) and Reynolds numbers (Re = 200–1000) are considered. Results show that magnetic field contributes an average 4% promotion in convective heat transfer coefficients compared with the condition of no magnet. The mechanism of the enhancement of heat transfer with magnetic field is explored based on the analysis of velocity field. Fe3O4 Nanoparticles move up and down under the magnetic force, and convective heat transfer is enhanced because of the disturbance of the Fe3O4 nanoparticles. Slip flow between the base fluid and nanoparticles also contributes to the enhancement of heat transfer.

Heat Transfer and Pressure Drop Simulation of CO2-Hydrate Mixture in Tube

2017 ◽  
Vol 25 (01) ◽  
pp. 1750005 ◽  
Author(s):  
Benedict Prah ◽  
Rin Yun
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Flow Characteristics ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Mixture Flow ◽  
Heat Transfer Coefficients ◽  
Two Phases ◽  
Energy Equations

The formation of CO2 hydrate during CO2 transportation presents a complex two-phase flow within tube. A two-dimensional CFD model for CO2 hydrate mixture flow in tube is derived based on the Eulerian multiphase flow modeling approach in which the two phases consist of CO2 gas and CO2 hydrate particles. A coupled Eulerian multiphase and nonisothermal flow model without phase-change is developed based on COMSOL Multiphysics built-in application modes. The model couples the mass, momentum, and energy equations for the two phases to solve the temperature and flow characteristics of the CO2 hydrate mixture flow in tube. CO2 hydrate particles are found to settle down during flow even under high velocity operation. The pressure drop increased linearly with inlet volume fraction from 1.29[Formula: see text]kPa for 0.1–5.2[Formula: see text]kPa for 0.5, and the related overall heat transfer coefficients of the CO2 hydrate mixture computed from the model ranged from 980 to 4000[Formula: see text]W/m2K with variation of CO2 hydrate volume fraction.

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