scholarly journals Thermal Performance of Cemented Paste Backfill Body Considering Its Slurry Sedimentary Characteristics in Underground Backfill Stopes

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7400
Author(s):  
Chao Huan ◽  
Sha Zhang ◽  
Xiaoxuan Zhao ◽  
Shengteng Li ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Simulation Model ◽  
Flow Direction ◽  
Seepage Flow ◽  
Parameter Determination ◽  
Conductive Heat ◽  
Cemented Paste Backfill ◽  
Exchange Performance ◽  
Paste Backfill

The combined mine backfill–geothermal (CMBG) system can be used to effectively extract geothermal energy by installing a heat exchange tube (HET) in the underground backfilled stopes of mines, which can be used as the heat supply for buildings in mines and the surrounding areas. The efficient performance of this system strongly depends on the thermal exchange process between the HET and its surrounding cemented paste backfill body (CPB). In this study, a validated simulation model is established to investigate the heat exchange performance of CPB, in which the nonuniformly distributed thermal properties in CPB are fully considered. The results indicate that the increase in the porosity has a negative effect on the heat exchange performance of CPB. With the increase in the porosity, the decreased rate of the conductive heat transfer in CPB could be up to approximately 18%. In conditions with seepage flow, the heat transfer capacity of CPB could be effectively improved. Generally, a higher hydraulic conductivity corresponds to a higher heat transfer performance of CPB. When the seepage velocity rose from 2 × 10−6 to 6 × 10−6 m/s, the thermal conductivity of CPB achieved a 114% increase from 1.843 to 3.957 W/(m·K). Furthermore, it was found that the thermal energy accumulates along the seepage flow direction, enhancing the thermal influencing radius of the HET in this direction. Thus, the arrangement of HETs should fully take into account the seepage flow effect. This proposed simulation model could provide a reference for parameter determination and optimization of CMBG systems.

Research on the Construction Technology of Radial Underground Heat Exchanger and its Heat Exchange Performance

2014 ◽  
Vol 580-583 ◽  
pp. 2488-2491
Author(s):  
Rong Hui Wang ◽  
Qing Hua Wang ◽  
Ye Feng
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Surface Temperature ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Ground Heat Exchanger ◽  
Construction Technology ◽  
Exchange Performance ◽  
Radial Heat

5 radial heat exchange wells were designed, and the different angle drilling, drilling pipe, and grouting backfill construction technology was studied. In addition, the heat transfer performance of the buried radial heat exchange wells was tested. The results show that, design of pipe equipment is feasible, construction is convenient, and the ratio of backfill material is reasonable; the heat transfer performance of 90 °buried tube is the best. The smaller the angle with the ground heat exchanger, the greater the heat exchange performance is affected by the surface temperature.

scholarly journals Heat exchange of a roller with a particle from polymeric material when it is pressed into tissue

2019 ◽  
Vol 298 ◽  
pp. 00086
Author(s):  
Vladimir Fedyaev ◽  
Valentin Khaliulin ◽  
Marat Faskhutdinov ◽  
Alexey Belyaev ◽  
Liliya Sirotkina
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Initial Conditions ◽  
Thermal Contact ◽  
Polymer Particle ◽  
Heat Propagation ◽  
Conductive Heat ◽  
Polymer Particles ◽  
Heat Conservation ◽  
The Heat Balance

We study the heat transfer of polymer particles with a roller that presses the material of the particles into the fabric. Provided that the speed of movement of the tissue with the particles relative to the roller is small, the heat exchange of the pressed particles with the environment is not taken into account, a mathematical model of conductive heat transfer in the contacting roller, polymer particle and reinforcing fabric is proposed. This model includes heat conservation equations written with respect to average temperatures of the roller, particles, fabric, as well as boundary and initial conditions. Assuming that there is perfect thermal contact between the polymer particles and the fabric, in the direction of heat propagation the average thickness of the pressed tissue particle is small, the layer of material of particles and fabric is considered thermally thin, the temperature in it varies slightly in thickness. As a result, the initial system of three equations is reduced to one equation with respect to the temperature of the roller, which is supplemented by the corresponding boundary and initial conditions. In the case when the temperature along the radius of the roller varies along its radius linearly, the specific heat flux on the surface of the roller is estimated. After that, this expression is substituted into the heat balance equation of a thermally thin layer consisting of particle material and tissue, which is integrated after certain transformations.

The Thermohydraulic Characteristics and Optimization Study of Radial Porous Heatsinks Using Multi-Objective Computational Method

2021 ◽  
Author(s):  
Amer Al-damook ◽  
Itimad D J Azzawi
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Entropy Generation ◽  
Heat Sink ◽  
Flow Direction ◽  
Inlet Temperature ◽  
Conductive Heat ◽  
Saturated Porous Media ◽  
Total Entropy ◽  
Multi Objective

Abstract The use of porous media to improve conductive heat transfer has been at the focus of interest in recent years. Limited studies, however, have focused on heat transfer in radial heat sinks fully and partially saturated porous media with a different arrangement. The current research, therefore, addresses the ability of radial porous heat sink solutions as a development of the above-mentioned investigations to improve the thermohydraulic characteristics and reduce the effect of 2nd thermodynamics law. The response surface method technique (RSM) with ANSYS FLUENT-CFD is accomplished to optimize the thermohydraulic features and the total entropy generation by the multi-objective optimum design for different parameters design such as porosity (Ø), inlet temperature (Tin) and applied heat flux (Q) simultaneously after achieving the optimum porous media arrangement related to the flow direction. The results showed that in terms of the flow direction, the optimum radial porous heat sink of 100%PM model was recognized (fully saturated porous media). Moreover, a significant agreement between the predicted and numerical simulation data for the optimum values is also seen. The optimum and undesirable designs of the thermohydraulic features, the total entropy generation and the optimum thermal management are detected in this investigation.

3-D Numerical Simulation of Structure Optimization of Rectangular Fin Tube Economizer

2008 ◽  
Author(s):  
Yu-Kun Lu¨ ◽  
Quan Lu
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Transfer Characteristic ◽  
Correlation Equation ◽  
Exchange Performance ◽  
Tube Arrangement ◽  
Flow Through ◽  
Fin Tube ◽  
Heat Exchange Efficiency ◽  
Porous Medium Model

The FLUENT6.2 software is adopted for numerical simulating heat transfer and flow characteristic of the gas when it flow through rectangular tube bundles in transverse direction, the array separation of tubes effected to heat transfer and flow is analyzed, the correlation equation of heat transfer characteristic is derived, and bases on the velocity distributing the rational tube arrangement is adopt to optimize economizer. Taking a certain power plant’s 200MW boiler economizer as an example, the porous medium model and heat exchanger model are employed for simulating. The study result indicates that: the heat-exchange performance of the economizer taking variable-pitch tube arrangement is excelled than the primary one, the discrepancy of gas pressure drop of them is narrow. The essay has direct significance for the structure optimizing and increasing heat exchange efficiency of power plant economizer.

Heat Transfer in Novel Internally-Finned Heat Exchange Passages

2008 ◽  
Author(s):  
Fuguo Zhou ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Flow Direction ◽  
Turbine Blades ◽  
Internal Heat ◽  
High Heat ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Performance Factors ◽  
High Heat Transfer

Heat exchange passages usually use internal fins to enhance heat transfer. These fins have ranged from simple ribs or turbulators to complex helical inserts. Applications of interest range from traditional heat exchangers to internal cooling of turbine blades. In the present paper, a novel fin design that combines the benefits of swirl, impingement and high heat transfer surface area is presented. Measurements of the internal heat transfer coefficients are provided using a liquid crystal technique. Pressure drop along the passage are also measured, therefore friction factors and thermal performance factors are presented. The experiments cover Reynolds number from 10,000 to 40,000 based on the hydraulic diameter of the main channel of the test section. Two models are tested, which have fins oriented at 30 degree and 45 degree to the flow direction, respectively. The results demonstrate that these novel designs produce overall heat transfer ratios greater than 3 compared to the smooth passage.

Effect of Flow Direction of Heating Medium on Heat Transfer Performance of Single-Path Plate-Fin Evaporator

2017 ◽  
Author(s):  
Kazuaki Shikichi ◽  
Takayuki Ueno ◽  
Hitoshi Asano
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Pressure Loss ◽  
Heat Transfer Performance ◽  
Flow Direction ◽  
Large Temperature ◽  
Transfer Performance ◽  
Counter Flow ◽  
Heating Medium

Effect of flow direction of heating medium on the heat transfer performance of upward evaporating refrigerant flows in a plate-fin heat exchanger was examined using HFC-134a as the refrigerant. The heat exchanger had a single refrigerant channel sandwiched by two water channels. Hot water flew upward or downward to form a parallel or counter flow heat exchange, respectively. To understand the heat flux distribution, temperature distributions on the outside wall of the water channel were visualized by an IR camera. As the results, it was shown that the difference in heat transfer rate between the parallel and counter flow was a little due to the large temperature difference in the heat exchange. The pressure loss of the refrigerant flow was larger for the parallel flow than the counter flow. It could be estimated from the wall temperature distribution that the increase in pressure loss might be caused by inhomogeneous phase distribution of the refrigerant flow.

scholarly journals Effect of Surface Structure Complexity on Interfacial Droplet Behavior of Superhydrophobic Titanium Surfaces for Robust Dropwise Condensation

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4107
Author(s):  
Je-Un Jeong ◽  
Dae-Yun Ji ◽  
Kwon-Yeong Lee ◽  
Woonbong Hwang ◽  
Chang-Hun Lee ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Surface Structure ◽  
Surface Structures ◽  
Superhydrophobic Surfaces ◽  
Dropwise Condensation ◽  
Exchange Performance ◽  
Droplet Behavior ◽  
Titanium Surfaces ◽  
Structure Complexity

In general, the dropwise condensation supported by superhydrophobic surfaces results in enhanced heat transfer relative to condensation on normal surfaces. However, in supersaturated environments that exceed a certain supersaturation threshold, moisture penetrates the surface structures and results in attached condensation, which reduces the condensation heat transfer efficiency. Therefore, when designing superhydrophobic surfaces for condensers, the surface structure must be resistant to attached condensation in supersaturated conditions. The gap size and complexity of the micro/nanoscale surface structure are the main factors that can be controlled to maintain water repellency in supersaturated environments. In this study, the condensation heat exchange performance was characterized for three different superhydrophobic titanium surface structures via droplet behavior (DB) mapping to evaluate their suitability for power plant condensers. In addition, it was demonstrated that increasing the surface structure complexity increases the versatility of the titanium surfaces by extending the window for improved heat exchange performance. This study demonstrates the usefulness of DB mapping for evaluating the performance of superhydrophobic surfaces regarding their applicability for industrial condenser systems.

Numerical Study of Fluid Flow and Heat Transfer in Plate-Fin Heat Transfer Exchanger of HTGR

2016 ◽  
Author(s):  
Wei Peng ◽  
Tao Chen ◽  
Xiaoyong Yang ◽  
Gang Zhao ◽  
Jie Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Numerical Study ◽  
Steady State Solution ◽  
Fluid Temperature ◽  
Heat Transfer Characteristics ◽  
Inlet Velocity ◽  
Exchange Performance ◽  
Flow And Heat Transfer ◽  
Better Than

This paper numerically study the flow and heat transfer characteristics of fluids within the plate-fin heat exchangers with plain and serrated fins. The calculation result is steady-state solution. Effects of the parameters such as inlet velocity and fin type on heat exchange performance are analyzed. The result indicates that under the same inlet velocity, the fluid temperature would be more uniform for the serrated fins. Whereas for the plain fins, the stratified distribution of the fluid temperature is more obvious. Being different from the plain fins, the serrated fins can destroy the boundary layer periodically and strengthen the disorder of the flow field, so its heat exchange performance is better than the plain fins’, however, the pressure drop with serrated fins increases correspondingly.

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