Numerical Simulation Study on Supercritical Natural Circulation Flow and Heat Transfer in Narrow Rectangular Channels

2013 ◽  
Author(s):  
Mingqiang Song ◽  
Tao Zhou ◽  
Jingjing Li ◽  
Juan Chen ◽  
Wanxu Cheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Subcritical Water ◽  
Natural Circulation ◽  
Fluid Velocity ◽  
Engineering Calculation ◽  
Thermal Engineering ◽  
Ansys Cfx ◽  
Rectangular Channels ◽  
Study Parameter

When the model of natural circulation in vertical rectangular channels with gap 1 mm was created, considering the character of supercritical water, the distribution of fluid velocity, temperature and density were obtained with the help of ANSYS CFX. The conclusion is that supercritical density is much lower than that of subcritical water in this study parameter and that the heat transfer ability of supercritical water is higher than that of subcritical water. Futuremore, narrow rectangular channels contribute supercritical fluid to transfer heat, which lay the foundation of accurate supercritical thermal engineering calculation.

An Experiment of Natural Circulation Flow and Heat Transfer With Supercritical Water in Parallel Channels

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Yuzhou Chen ◽  
Chunsheng Yang ◽  
Minfu Zhao ◽  
Keming Bi ◽  
Kaiwen Du
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Supercritical Water ◽  
Dynamic Instability ◽  
Flow Instability ◽  
Natural Circulation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Parallel Channels

An experiment of natural circulation of supercritical water in parallel channels was performed in bare tubes of inner diameter 7.98 mm and heated length 1.3 m, covering the ranges of pressure of 24.7–25.5 MPa, mass flux of 400–1000  kg/m2 s, and heat flux of up to 1.83  MW/m2. When the heat flux reached 1.12  MW/m2, the outlet water temperature jumped from 325°C to 360°C, associated with a decrease in the flow rate and an initiation of dynamic instability. When the heat flux exceeded 1.39  MW/m2, the flow instability was stronger, and the flow rate increased in one channel and decreased in another one. Until the heat flux reached 1.61  MW/m2, the outlet water temperatures of two channels reached the pseudocritical point, and the flow rates of two channels tended to close each other. The experiment with a single heated channel was also performed for comparison. The measurements on the heat-transfer coefficients (HTCs) were compared to the calculations by the Bishop et al., Jackson’s, and Mokry et al. correlations, showing different agreements within various conditions.

ASSESSMENT OF THERMAL PROTECTIVE CHARACTERISTICS OF WELL MASONRY WITH THE USE OF NO-FINE EXPANDED-CLAY LIGHTWEIGHT CONCRETE

2019 ◽  
Vol 9 (1) ◽  
pp. 15-19
Author(s):  
Yury S. VYTCHIKOV ◽  
Mikhail E. SAPAREV ◽  
Andrey S. PRILEPSKY ◽  
Darya D. KONYAKINA
Keyword(s):  
Heat Transfer ◽  
Lightweight Concrete ◽  
Engineering Calculation ◽  
Temperature Fields ◽  
Thermal Engineering ◽  
Transfer Resistance ◽  
Heat Engineering ◽  
Energy Efficient Buildings ◽  
Engineering Technique ◽  
Original Construction

As part of the implementation of programs for the resettlement of dilapidated housing and rural construction, special attention is paid to the construction of low rise energy efficient buildings. Analysis of various technologies for the construction of low rise buildings revealed the feasibility of using expanded clay concrete as a structural and insulating material in three layer exterior walls and well laying. The presented heat engineering calculation of the original construction of the well masonry showed rather high values of the reduced heat transfer resistance and the coefficient of heat engineering uniformity. Rather high accuracy of the presented engineering technique of thermal engineering calculation is confirmed by comparison of the received data on resistance to heat transfer of an external wall by the approximate analytical method with data of computer simulation of temperature fields by a finite element method.

Study on Flow and Heat Transfer Characteristics of Different States of Water Under Natural Circulation

2014 ◽  
Author(s):  
Zhongyun Ju ◽  
Tao Zhou ◽  
Jingjing Li ◽  
Zejun Xiao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Supercritical Water ◽  
Natural Circulation ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Software CFX is used to build a typical natural circulation loop to study flow and heat transfer characteristics of water vapor, the vapor-liquid two-phase and supercritical water under natural circulation. During the process of natural circulation, the variation of parameters, heat transfer coefficient and mass flow is compared. It is found that when formed a natural circulation, the steam has a lower mass flow and heat transfer coefficient, while the two parameters of two-phase and supercritical water are higher. Indicates that the heat transfer capability of steam is weak, the steam cannot transfer heat out opportunely when serious accidents take place. The two-phase water is of high heat transfer coefficient. Supercritical water is of strong exchange capacity, supercritical water under natural circulation is a promising flow pattern.

scholarly journals Cooling of a battery pack of a car, working on renewable energy

2018 ◽  
Vol 245 ◽  
pp. 15003 ◽  
Author(s):  
Ivan Kasatkin ◽  
Mikle Egorov ◽  
Evgeny Kotov ◽  
Evgeny Zakhlebaev
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Heat Removal ◽  
Lithium Ion ◽  
Operating Mode ◽  
Engineering Calculation ◽  
Electrical Circuit ◽  
Thermal Engineering ◽  
Air Cooling ◽  
Forced Air

The aim of the work is to choose a method of a solar car battery cooling. The student engineering team of Peter the Great Petersburg Polytechnic University designs the car. The analysis of the electrical circuit of the battery is carried out, the heat release is estimated due to three factors. According to the conditions of reliable operation of the battery, it is necessary to maintain its temperature range below 45°C, which requires cooling. The paper analyzes the possibilities of liquid, air-cooling, compares the free and forced methods of convective heat transfer. For the normal operating mode of the electric vehicle, environmental temperature at the level up to 38°C, a criterion thermal engineering calculation of the forced air-cooling of the corridor assembly of 405 battery cells providing the required heat dissipation is performed. It is shown that relatively high values of the heat transfer coefficient are provided under turbulent flow conditions characterized by Reynolds criteria above 103. On the basis of an analysis of the steady-state stationary heat-removal regime, it was concluded that an air flow provides a temperature gradient, sufficient for cooling the lithium-ion battery of a Solar Car «Polytech Solar».

Study on the Influence Factors of Heat Transfer Coefficient of Supercritical Water Under Different Circulation Modes

2020 ◽  
Author(s):  
Peng Xu ◽  
Tao Zhou ◽  
Jialei Zhang ◽  
Juan Chen ◽  
Zhongguan Fu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Flow Rate ◽  
Supercritical Water ◽  
Natural Circulation ◽  
Inlet Temperature ◽  
The Heat Transfer Coefficient

Abstract There are many factors that can affect the heat transfer coefficient (HTC) of supercritical water in forced and natural circulation. The correlation between the factors with the HTC under different circulation modes has an important influence on the reactor core design. By extracting the experimental data of supercritical water in forced circulation and natural circulation, the grey correlation model was used to analyze the relational degree between these factors with HTC. The results show that: Under the condition of forced circulation, there is a positive correlation between the inlet temperature, mass flow velocity, the thickness of the grid body with the HTC of supercritical water, and the order is: mass flow velocity > inlet temperature > the thickness of the grid body; there is a negative correlation between the pressure, heat flux with the heat transfer coefficient of supercritical water, and the order is: pressure > heat flux. Under the condition of natural circulation, there is a positively correlation between heating power, inlet temperature and circulation flow rate with HTC, and the order of magnitude is: circulation flow rate > heating power > inlet temperature; diameter and pressure are negatively correlated with heat transfer coefficient, and the order of magnitude is: pressure > diameter. In the two circulation modes, mass flow rate is an important factor affecting the heat transfer capacity of supercritical water, while the effect of heat flux on the heat transfer coefficient is contrary.

Experimental Study of Heat Transfer in a 7-Element Bundle Cooled With Supercritical Freon-12

2012 ◽  
Author(s):  
G. Richards ◽  
J. Samuel ◽  
A. S. Shelegov ◽  
P. L. Kirillov ◽  
I. L. Pioro ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Supercritical Water ◽  
Mass Flux ◽  
Test Section ◽  
High Pressures ◽  
Natural Circulation ◽  
Heat Fluxes ◽  
Bulk Fluid ◽  
Test Loop

Experimental data on SuperCritical-Water (SCW) cooled bundles are very limited. Major problems with performing such experiments are technical difficulties in testing and experimental costs at high pressures, temperatures and heat fluxes. Also, there are only a few SCW experimental setups currently in the world capable of providing data. SuperCritical Water-cooled nuclear Reactors (SCWRs), as one of the six concepts of Generation IV reactors, cannot be designed without such data. Therefore, a preliminary approach uses modeling fluids such as carbon dioxide and refrigerants instead of water are practical. In particularly, experiments in supercritical refrigerant-cooled bundles can be used. One of the SC modeling fluids typically used is Freon-12 (R-12) with the critical pressure of 4.136 MPa and the critical temperature of 111.97°C. A set of experimental data obtained at the Institute of Physics and Power Engineering (IPPE, Obninsk, Russia) in a vertically-oriented bundle cooled with supercritical R-12 was analyzed. This dataset consisted of 20 runs. The test section was 7-element bundle installed in a hexagonal flow channel with 3 grid spacers. Data was collected at pressures of approximately 4.65 MPa for several different combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. The values of mass flux were ranged from 400 to 1320 kg/m2s and inlet temperatures ranged from 72 to 120°C. The test section consisted of fuel-element simulators that were 9.5 mm in OD with the total heated length of about 1 m. Bulk-fluid and wall temperature profiles were recorded using a combination of 8 thermocouples. Analysis of the data has confirmed that there are three distinct heat-transfer regimes for forced convention in supercritical fluids: 1) Normal heat transfer; 2) Deteriorated heat transfer characterized with higher than expected wall temperatures; and 3) Enhanced heat transfer characterized with lower than expected wall temperatures. It was also confirmed that the effects of spacers are evident which was previously observed in sub-critical experimental data. Further analysis needs to be conducted on the deteriorated heat transfer phenomena for low mass flux cases which represent accident scenarios. This can be done by designing a natural circulation experimental test loop.

The Basic Thermal Hydraulic Issues of Applying Supercritical Fluid to Nuclear Reactors

2021 ◽  
pp. 682-716
Author(s):  
Jinguang Zang ◽  
Xiao Yan ◽  
Yanping Huang
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Flow Instability ◽  
Nuclear Reactors ◽  
Natural Circulation ◽  
Parallel Channel ◽  
Validation Data ◽  
Channel System ◽  
Stability Issues ◽  
The Heat Transfer Coefficient

This chapter is mainly focused on illustrating some introductory progress on thermal hydraulic issues of supercritical water, including heat transfer characteristics, pressure loss characteristics, flow stability issues, and numerical method. These works are mainly to give a basic idea of elementary but important topics in this area. An analytical method was proposed up to predict the heat transfer coefficient and friction coefficient based on the two-layer wall function. Flow instability experiments have been carried out in a two-parallel-channel system with supercritical water, aiming to provide an up-to-date knowledge of supercritical flow instability phenomena and initial validation data for numerical analysis. The natural circulation instability of supercritical water was also investigated in the experiments.

scholarly journals Study on the Movement and Deposition of Particles in Supercritical Water Natural Circulation Based on Grey Correlation Theory

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2315
Author(s):  
Liangyu Zhu ◽  
Tao Zhou ◽  
Xijia Ding ◽  
Xuemeng Qin ◽  
Jialei Zhang
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Particle Deposition ◽  
Particle Concentration ◽  
Natural Circulation ◽  
Particle Diameter ◽  
Heating Power ◽  
Stable Operation ◽  
Initial Flow ◽  
Heating Section

The movement and deposition of particles that occur during their natural circulation in supercritical water exercise an important impact on the safe and stable operation of a supercritical water reactor (SCWR). When supercritical water flows in pipelines, a large number of corrosive particles may be generated due to pipeline corrosion or the purity of the fluid itself. The presence of particulate matter affects the heat transfer efficiency of the pipeline, increasing flow resistance and easily promoting heat transfer deterioration. ANSYS-CFX numerical analysis software was used to simulate the natural circulation loop of supercritical water, and micron particles were added in the initial flow field. The effects of heating power, particle concentration and particle diameter on particle deposition were obtained. Through this analysis, it can be concluded that the heating of the pipeline has a certain inhibitory effect on the deposition of particles. The rise in both initial particle concentration and particle diameter serve to reinforce the deposition of particles in the heating section. Depending on the degree of influence, the contributory parameters to particle deposition include particle diameter, particle concentration and heating power in turn.

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