scholarly journals The use of ice to cool the concrete mix in the construction of massive structures

2021 ◽  
Vol 264 ◽  
pp. 02047
Author(s):  
Nikolay Aniskin ◽  
Trong Chuc Nguyen ◽  
Anh Kiet Bui
Keyword(s):  
Heat Transfer ◽  
Energy Balance ◽  
Initial Temperature ◽  
Concrete Block ◽  
Heat Transfer Process ◽  
The Other ◽  
Maximum Temperature ◽  
Mass Concrete ◽  
Concrete Mix ◽  
Practical Design

This article proposes a formula to determine the required amount of ice to partially replace the water in the concrete mix to control the initial temperature of the concrete mix and reduce possible cracking. The formula was created based on the principle of energy balance in the heat transfer process. At the same time, the obtained results were compared with the other methods. Besides, an example of the calculation for a concrete block during the construction was performed. The maximum temperature and temperature difference in mass concrete obtained depend significantly on the initial temperature of the concrete mixture. The research results and the proposed techniques can be used in the practical design of mass concrete structures.

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 A Simplified Method for Real-Time Prediction of Temperature in Mass Concrete at Early Age

2020 ◽  
Vol 10 (13) ◽  
pp. 4451
Author(s):  
Guo An ◽  
Ning Yang ◽  
Qingbin Li ◽  
Yu Hu ◽  
Huiting Yang
Keyword(s):  
Cement Hydration ◽  
Cooling System ◽  
Concrete Block ◽  
Arch Dam ◽  
In Situ Monitoring ◽  
Cooling Effect ◽  
Maximum Temperature ◽  
Early Age ◽  
Mass Concrete ◽  
Measuring Point

According to the practice of temperature control in dam concrete, within a few days after a concrete block is poured, the temperature at the core of the concrete rises rapidly. The maximum temperature may still exceed the standard even under a relatively perfect post-cooling system, which is mostly caused by failure to quickly and correctly judge the development of the early-age temperature. This study investigates concrete temperature at an early age via in situ monitoring data collected from Baihetan arch dam and Wudongde arch dam. A simplified algorithm of temperature prediction is formed, which only considers the heat released by cement hydration and the cooling effect of cooling pipes. The influence of a cooling pipe on the measuring point of the thermometer is investigated, and a simple empirical formula to calculate the cooling effect is obtained. An equation for the rate of hydration temperature rise is achieved by combining measured data and the formula used to calculate the cooling effect. Furthermore, through the explorations of the related data, it is determined that the cement hydration ratio of the two dams is quite low during concreting. On the basis of the data collected from the field, the method to predict temperature proposed in this study is tested and proven.

scholarly journals The Effect of Beam Intensity on Temperature Distribution in ADS Windowless Lead-Bismuth Eutectic Spallation Target

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jie Liu ◽  
Lei Gao ◽  
Wen-qiang Lu
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Temperature Distribution ◽  
Heat Transfer Process ◽  
Beam Intensity ◽  
Maximum Temperature ◽  
Flow Process ◽  
Large Power ◽  
Spallation Target ◽  
Lead Bismuth Eutectic

The spallation target is the component coupling the accelerator and the reactor and is regarded as the “heart” of the accelerator driven system (ADS). Heavy liquid metal lead-bismuth eutectic (LBE) is served as core coolant and spallation material to carry away heat deposition of spallation reaction and produce high flux neutron. So it is very important to study the heat transfer process in the target. In this paper, the steady-state flow pattern has been numerically obtained and taken as the input for the nuclear physics calculation, and then the distribution of the extreme large power density of the heat load is imported back to the computational fluid dynamics as the source term in the energy equation. Through the coupling, the transient and steady-state temperature distribution in the windowless spallation target is obtained and analyzed based on the flow process and heat transfer. Comparison of the temperature distribution with the different beam intensity shows that its shape is the same as broken wing of the butterfly. Nevertheless, the maximum temperature as well as the temperature gradient is different. The results play an important role and can be applied to the further design and optimization of the ADS windowless spallation target.

scholarly journals Heat Transfer Simulation and Temperature Rapid Prediction for Trench Laying Cable

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Chen-Zhao Fu ◽  
Wen-Rong Si ◽  
Ke-Ke Fang ◽  
Jian Yang
Keyword(s):  
Heat Transfer ◽  
Back Propagation ◽  
Computation Time ◽  
Back Propagation Neural Network ◽  
Heat Transfer Process ◽  
Maximum Temperature ◽  
Network Algorithm ◽  
Flat Type ◽  
Maximum Current ◽  
Neural Network Algorithm

Heat transfer process for trench laying cable is complex. To guarantee safe operation of the cable, it is necessary to predict the temperature and maximum current capacity of trench laying cable rapidly and accurately. Therefore, in this study, an adaptive optimized particle swarm optimization algorithm (LFVPSO) is proposed based on Levy flight algorithm, and it is used to modify the back propagation neural network algorithm (LFVPSO-BPNN). Then, combined with numerical simulations, a network algorithm for temperature prediction of trench laying cable is developed using LFVPSO-BPNN. Finally, the maximum current capacity of four-loop three-phase trench laying cable is calculated using LFVPSO-BPNN together with genetic algorithm (GA&LFVPSO-BPNN). At first, it is found that the LFVPSO-BPNN algorithm proposed in this study is reliable and accurate to predict the cable maximum temperature for different loops (Tmax,i) in the trench. Furthermore, as compared with other similar algorithms, when LFVPSO-BPNN algorithm is used to predict the temperature of trench laying cable, its computation time would be reduced and the prediction accuracy would be improved as well. Second, it is revealed that the effect of ground air temperature (Tsur) on the maximum current capacity of trench laying cable (It,max) is remarkable. As Tsur increases, the It,max for both flat-type and trefoil-type trench laying cable would significantly decrease. In addition, with the same Tsur, the It,max for the flat-type trench laying cable are obviously higher.

scholarly journals Building a nomogram to predict maximum temperature in mass concrete at an early age

2021 ◽  
Vol 263 ◽  
pp. 01008
Author(s):  
Trong - Chuc Nguyen ◽  
Van - Quang Nguyen ◽  
Nikolay Aniskin ◽  
Ba - Thang Phung ◽  
Quoc - Long Hoang
Keyword(s):  
Initial Temperature ◽  
Concrete Structures ◽  
Temperature History ◽  
Maximum Temperature ◽  
Early Age ◽  
Mass Concrete ◽  
The Finite Element Method ◽  
Thermal Cracks ◽  
Massive Concrete ◽  
Main Factor

During the construction of massive concrete structures, the main factor that affects the structure is temperature. The resulting temperature is the result of hydration of the cement and some other factors, which leads to the formation of thermal cracks at an early age. So, the prediction of temperature history in massive concrete structures has been a very important problem. In this study, with the help of numerical methods, a temperature nomogram was built to quickly determine the maximum temperature in concrete structures with different parameters such as size, cement content, and the initial temperature of the concrete mixture. The obtained temperature nomogram has been compared with the results of the finite element method and the model experiment gives reliable results. It can be used to predict maximum temperature in mass concrete structures to prevent the formation of thermal cracks.

scholarly journals Calculation of the Efficiency of Regenerative Air Heat Exchanger with Intermediate Heat Carrier

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Mikhail Ivanovich Nizovtsev ◽  
V. Yu. Borodulin
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Exchanger ◽  
Heat Carrier ◽  
Heat Transfer Process ◽  
Maximum Temperature ◽  
Operating Parameters ◽  
Air Flow Rate ◽  
Filling Height ◽  
Temperature Efficiency

The study deals with a new regenerative air heat exchanger with an intermediate heat carrier used in the systems of room ventilation. A physical and mathematical model of the heat transfer process is proposed. The influence of design and operating parameters on the temperature efficiency of the heat exchanger is analyzed. The possibility of a significant increase in its efficiency with a decrease in the packing diameter is shown. As a result of calculations, it was found that with a decrease in the filling height, the maximum temperature efficiency shifted towards a decrease in the air flow rate from its value determined from the equality of water equivalents of liquid and air.

scholarly journals PERFORMANCE ANALYSIS OF THERMAL DIODES

2006 ◽  
Vol 5 (2) ◽  
pp. 66
Author(s):  
H. A. Machado ◽  
A. G. Ramos
Keyword(s):  
Heat Transfer ◽  
Numerical Data ◽  
High Heat ◽  
Heat Transfer Process ◽  
The Other ◽  
Internal Cavity ◽  
Transfer Rates ◽  
High Heat Transfer ◽  
Long Time ◽  
Insulation Systems

The thermal diode consists in a common brick empty inside, where the internal cavity is geometrically arranged as two rectangles, disposed one over the other but not aligned. When the lower side is heated, natural convection in the air inside yields high heat transfer rates from this side to the other. When the upper side is heated, the heat transfer should run by pure conduction, and the brick with air inside works as a thermal insulator. As this brick allows a good conductance in one direction and insulation in the opposite sense, it behaves as an electric diode, being known as thermal diode. This principle is already known for a long time, but its use is still not extensive, and there are no basic rules for the cavity design or even a theoretical study of viability for this use replacing the conventional insulation systems. The objective of this work is to simulate the heat transfer process inside a thermal diode, in order to obtain the optimal geometry and dimensions and to verify the viability of its use in buildings for thermal optimization. The numerical data are validated through comparing with that obtained from the test applied to cellular concrete bricks.

scholarly journals Numerical Study of Heat Transfer in Trefoil Buried Cable with Fluidized Thermal Backfill and Laying Parameter Optimization

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Chen-Zhao Fu ◽  
Wen-Rong Si ◽  
Lei Quan ◽  
Jian Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Core Loss ◽  
Parabolic Type ◽  
Heat Transfer Process ◽  
Maximum Temperature ◽  
Natural Soil ◽  
Buried Cables ◽  
Flat Type ◽  
Proper Design

Trefoil buried cable is one of the important cable arrangements for the underground transmission line, and its heat transfer performance is relatively poor. By filling with fluidized thermal backfill material (FTB) around trefoil buried cables, the heat transfer would be efficiently enhanced, while the filling cost should also be considered. In the present study, the heat transfer process in the FTB trefoil buried cables is numerically studied, where the cable core loss and eddy current loss in the cable were coupled for the simulation. The heat transfer performances and ampacities for trefoil buried cables with different back fill materials were analysed and compared with each other. Then, the laying parameters for the parabolic-type FTB trefoil buried cables were optimized with the radial basis function neural network (RBNN) and genetic algorithm (GA). Firstly, it is found that, with FTB material, the maximum temperature in the cable core is obviously reduced, and the cable ampacity is greatly improved as compared with the cables buried around natural soil (NS). Secondly, when compared with flat-type FTB model, the heat transfer rate in the cable with parabolic-type FTB laying method would be slightly reduced, while the FTB amount used for the buried cables is greatly reduced. Finally, as for parabolic-type FTB trefoil buried cables, with proper design of geometric parameters (s1 = 0.290 m, s2 = 0.302 m, and l = 0.3 m with I = 1300 A) for the FTB laying cross section, the overall performance for the cable was optimized.

Optimization of Thermal Structure of Conduction Cooling HTS Magnet

2015 ◽  
Vol 723 ◽  
pp. 988-991
Author(s):  
Xiang Li ◽  
Gang Wu ◽  
Ke Bi ◽  
Yan Fei Li ◽  
Zhi Yin Tang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Structure ◽  
Simulation Method ◽  
Heat Transfer Process ◽  
Structure Design ◽  
Maximum Temperature ◽  
Maximum Temperature Difference ◽  
Conduction Model ◽  
Conduction Cooling ◽  
Hts Magnet

According to the structure feature of HTS magnet, heat transfer process in steady-state conditions is analyzed, and the heat conduction model of magnet unit was established. The thermal structure of conduction cooling HTS magnet was optimized to minimize the maximum temperature difference of magnet unit, and the optimization result was verified with simulation method. Simulation results show the optimization method mentioned in this paper is effective, which can provide a guidance to heat transfer structure design.

scholarly journals Challenge Analysis and Schemes Design for the CFD Simulation of PWR

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Guangliang Chen ◽  
Zhijian Zhang ◽  
Zhaofei Tian ◽  
Lei Li ◽  
Xiaomeng Dong
Keyword(s):  
Heat Transfer ◽  
Cfd Simulation ◽  
Structural Features ◽  
Heat Transfer Process ◽  
The Other ◽  
Complex Structures ◽  
Flow And Heat Transfer ◽  
Flow Channels ◽  
Choice Decision ◽  
Quantitative Regularity

CFD simulation for a PWR is an important part for the development of Numerical Virtual Reactor (NVR) in Harbin Engineering University of China. CFD simulation can provide the detailed information of the flow and heat transfer process in a PWR. However, a large number of narrow flow channels with numerous complex structures (mixing vanes, dimples, springs, etc.) are located in a typical PWR. To obtain a better CFD simulation, the challenges created by these structural features were analyzed and some quantitative regularity and estimation were given in this paper. It was found that both computing resources and time are in great need for the CFD simulation of a whole reactor. These challenges have to be resolved, so two schemes were designed to assist/realize the reduction of the simulation burden on resources and time. One scheme is used to predict the combined efficiency of the simulation conditions (configuration of computing resources and application of simulation schemes), so it can assist the better choice/decision of the combination of the simulation conditions. The other scheme is based on the suitable simplification and modification, and it can directly reduce great computing burden.

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