scholarly journals Main Directions of Russian Developments of Prospective Structures of Water-Cooled Supercritical Pressure Reactors

2020 ◽  
Vol 18 ◽  
pp. 34-41
Author(s):  
I. G. Sharaevsky ◽  
◽  
N. M. Fialko ◽  
A. V. Nosovskyi ◽  
L. B. Zimin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nuclear Power ◽  
Negative Impact ◽  
Environmental Safety ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Capital Costs ◽  
Advantages And Disadvantages ◽  
Process Characteristics ◽  
Supercritical Parameters

An analytical review of the evolution of attempts to create, schematic and constructive solutions for energycooled nuclear reactors with nuclear steam overheating and supercritical parameters of the working fluid in the conditions of the former USSR and the Russian Federation was made. A comparison of a number of major technical and economic characteristics of main developments of tube and tank reactors is made, the available information on the results of experimental and industrial operation of AMB reactors structures is considered, their advantages and disadvantages are evaluated in terms of technical perfection, reliability, technical and economic performance as well as environmental safety. The expected reduction in capital costs of 40% during the transition of nuclear power units with a capacity of 1,000 MW to single-circuit promising SCWR reactors is achievable only if the steam temperature rises to 625 °C, which has not yet been mastered even in traditional power engineering. The specific energy intensity of reactor’s active zones promising Russian developments under the SCWR program is in most cases extremely high, which will have a negative impact on the characteristics of nuclear safety. The conclusion is made concerning the high probability of a significant increase in the accident rate of the SCWR reactor cores, due to the insufficient study of the heat transfer process characteristics on the heat transfer surface of the TVEL under the conditions of supercritical parameters of the coolant, in particular, such phenomena as pseudo film boiling and thermoacoustic vibrations. In general, insufficient level of completeness of the latest Russian developments and lack of final conceptual projects were noted, which does not provide sufficient grounds for choosing promising schematic and constructive decisions necessary for making reasonable forecasts about the possibility of using supercritical parameters of the coolant in the modern nuclear power industry in the near future.

Analysis of Multiplicity Phenomena in Longitudinal Fins Under Multi-Boiling Conditions

2004 ◽  
Vol 126 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Rizos N. Krikkis ◽  
Stratis V. Sotirchos ◽  
Panagiotis Razelos
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Solution Structure ◽  
Heat Dissipation ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Constant Thickness ◽  
Base Temperature ◽  
Operating Variables ◽  
Convection Parameter

A numerical bifurcation analysis is carried out in order to determine the solution structure of longitudinal fins subject to multi-boiling heat transfer mode. The thermal analysis can no longer be performed independently of the working fluid since the heat transfer coefficient is temperature dependent and includes the nucleate, the transition and the film boiling regimes where the boiling curve is obtained experimentally for a specific fluid. The heat transfer process is modeled using one-dimensional heat conduction with or without heat transfer from the fin tip. Furthermore, five fin profiles are considered: the constant thickness, the trapezoidal, the triangular, the convex parabolic and the parabolic. The multiplicity structure is obtained in order to determine the different types of bifurcation diagrams, which describe the dependence of a state variable of the system (for instance the fin temperature or the heat dissipation) on a design (Conduction-Convection Parameter) or operation parameter (base Temperature Difference). Specifically the effects of the base Temperature Difference, of the Conduction-Convection Parameter and of the Biot number are analyzed and presented in several diagrams since it is important to know the behavioral features of the heat rejection mechanism such as the number of the possible steady states and the influence of a change in one or more operating variables to these states.

Analysis and Operation Optimization of Recompression Supercritical Carbon Dioxide Power Generation System Based on the Power Flow Method

2018 ◽  
Author(s):  
Xia Li ◽  
Qun Chen ◽  
Xi Chen
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Power Generation ◽  
Mass Flow ◽  
Power Flow ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Generation System ◽  
Fluid Properties ◽  
Power Generation System

Due to the peculiar physical properties, supercritical carbon dioxide (sCO2) is considered as a promising working fluid in power generation cycles with high reliability, simple structure and great efficiency. Compared with the general thermal systems, the variable properties of sCO2 make the system models obtained by the traditional modelling method more complex. Besides, the pressure distribution in the system will affect the distribution of the fluid properties, the fluid properties influencing the heat transfer process will produce an impact on the temperature distribution which will in turn affect the pressure distribution through the mass flow characteristics of all components. This contribution introduces the entransy-based power flow method to analyze and optimize a recompression sCO2 power generation system under specific boundary conditions. About the heat exchanger, by subdividing the heat transfer area into several segment, the fluid properties in each segment are considered constant. Combining the entransy dissipation thermal resistance of each segment and the energy conservation of each fluid in each segment offers the governing equations for the whole heat transfer process without any intermediate segment temperatures, based on which the power flow diagram of the overall heat transfer process is constructed. Meanwhile, the pressure drops are constrained by the mass flow characteristics of each component, and the inlet and outlet temperatures of compressors and turbines are constrained by the isentropic process constraints and the isentropic efficiencies. Combining the governing equations for the heat exchangers and the constraints for turbine and the compressors, the whole system is modeled by sequential modular method. Based on this newly developed model, applying the genetic algorithm offers the maximum thermal efficiency of the system and the corresponding optimal operating variables, such as the mass flow rate of the working fluid in the cycle, the heat capacity rate of the cold source and the recompression mass fraction under the given heat source. Furthermore, the optimization of the system under different boundary conditions is conducted to study its influence on the optimal mass flow rate of the working fluid, the heat capacity of the cold source and the maximum system thermal efficiency. The results proposes some useful design suggestions to get better performance of the recompression supercritical carbon dioxide power generation system.

Performance Evaluation of a Vertical U-Tube Ground Heat Exchanger Using a Numerical Simulation Approach

2013 ◽  
Vol 724-725 ◽  
pp. 909-915
Author(s):  
Ping Fang Hu ◽  
Zhong Yi Yu ◽  
Fei Lei ◽  
Na Zhu ◽  
Qi Ming Sun ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Ground Heat Exchanger ◽  
Ground Source Heat Pump ◽  
Ground Source

A vertical U-tube ground heat exchanger can be utilized to exchange heat with the soil in ground source heat pump systems. The outlet temperature of the working fluid through the U-tube not only accounts for heat transfer capacity of a ground heat exchanger, but also greatly affects the operational efficiency of heat pump units, which is an important characteristic parameter of heat transfer process. It is quantified by defining a thermal effectiveness coefficient. The performance evaluation is performed with a three dimensional numerical model using a finite volume technique. A dynamic simulation was conducted to analyze the thermal effectiveness as a function of soil thermal properties, backfill material properties, separation distance between the two tube legs, borehole depth and flow velocity of the working fluid. The influence of important characteristic parameters on the heat transfer performance of vertical U-tube ground heat exchangers is investigated, which may provide the references for the design of ground source heat pump systems in practice.

Application of Supercritical Fluids in Thermal- and Nuclear-Power Engineering

2021 ◽  
pp. 601-658
Author(s):  
Igor L. Pioro
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Supercritical Fluids ◽  
Nuclear Power ◽  
Power Plants ◽  
Thermal Power ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Thermal Power Plants ◽  
Power Cycles

Supercritical Fluids (SCFs) have unique thermophyscial properties and heat-transfer characteristics, which make them very attractive for use in power industry. In this chapter, specifics of thermophysical properties and heat transfer of SCFs such as water, carbon dioxide, and helium are considered and discussed. Also, particularities of heat transfer at Supercritical Pressures (SCPs) are presented, and the most accurate heat-transfer correlations are listed. Supercritical Water (SCW) is widely used as the working fluid in the SCP Rankine “steam”-turbine cycle in fossil-fuel thermal power plants. This increase in thermal efficiency is possible by application of high-temperature reactors and power cycles. Currently, six concepts of Generation-IV reactors are being developed, with coolant outlet temperatures of 500°C~1000°C. SCFs will be used as coolants (helium in GFRs and VHTRs, and SCW in SCWRs) and/or working fluids in power cycles (helium, mixture of nitrogen (80%) and helium (20%), nitrogen and carbon dioxide in Brayton gas-turbine cycles, and SCW/“steam” in Rankine cycle).

The Effect of Nanoscale Surface Modification on Boiling Heat Transfer and Critical Heat Flux

2010 ◽  
Author(s):  
Moo Hwan Kim
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nuclear Power ◽  
Power Plants ◽  
Flow Boiling ◽  
Heated Surface ◽  
Pool Boiling ◽  
Working Fluid ◽  
Wetting Ability ◽  
Modified Surface

Recently, there were lots of researches about enormous CHF enhancement with the nanofluid in pool boiling and flow boiling. It is supposed the deposition of nanoparticles on the heated surface is one of main reasons. In a real application, nanofluid has a lot of problems to be used as the working fluid because of sedimentation and aggregation. The artificial surfaces on silicon and metal were developed to have the similar effect with nanoparticles deposited on the surface. The modified surface showed the enormous ability to increase CHF in pool boiling. Furthermore, under flow boiling, it had also good results to increase CHF. In these studies, we concluded that wetting ability of surface; e.g. wettability and liquid spreading ability (hydrophilic property of surface) was a key parameter to increase CHF under both pool and flow boiling. In addition, using wettability difference of surface; e.g. hydrophilic and hydrophobic, we conducted some tests of BHT (boiling heat transfer) enhancement using the oxide silicon which have micro-sized hydrophobic islands on hydrophilic surface. By using both of these techniques, we propose an optimized surface to increase both CHF and BHT. Also, the fuel surface of nuclear power plants is modified to have same effect and the results shows a good enhancement of CHF, too.

A Review on Experimental and Numerical Investigations on Using Nanofluid in Volumetric Solar Energy Collectors

2014 ◽  
Author(s):  
Siamak Mirmasoumi ◽  
Mohammad Pourgol-Mohammad
Keyword(s):  
Heat Transfer ◽  
Power Plants ◽  
Radiant Energy ◽  
Solar Thermal ◽  
Working Fluid ◽  
Steam Generation ◽  
Solar Thermal Energy ◽  
Solar Absorption ◽  
Advantages And Disadvantages ◽  
Solar Power Plants

By a simple research in the scholarly articles, it can be realized that the tendency to using solar thermal energy has risen in the recent years due to its many reasonable advantages. In conventional solar thermal systems, HTFs (Heat Transfer Fluids) are pumped through the piping of a solar collector and after absorbing the solar radiant energy conveys it to water to make steam. No need to say that this method contains some losses via all methods of heat transfer. To solve this problem, researchers have shown that with direct steam generation, in which working fluid directly absorbs solar thermal and becomes vapor, solar power plants have the potential to be more productive. However, the aforesaid conventional HTFs don’t have efficient enough thermal properties and need to be improved. For this reason using nanofluid has become to some extent popular in heat transfer facilities like solar thermal collectors. In the present study, we are going to identify the advantages and disadvantages of using nanoparticles in direct solar absorption systems (DSASs). To achieve this, a general review on the experimental and numerical studies in this field is done. Additionally some of the most effective particles for such a special case, in which particles should have good radiative characteristics, are introduced. Finally, after discussion about the highlighted challenges of using nanofluids in DSASs, some helpful suggestions to overcome these problems will be presented.

Heat Transfer Augmentation in Solar Collectors Using Nanofluids: A Review

2020 ◽  
Vol 6 (2) ◽  
pp. 72-81 ◽  
Author(s):  
Morteza Anbarsooz ◽  
Maryam Amiri ◽  
Iman Rashidi ◽  
Mohammad Javadi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Process ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Optical Parameters ◽  
Solar Collectors ◽  
Direct Absorption ◽  
Heat Transfer Augmentation

Background: Enhancing the heat transfer rate in solar collectors is an essential factor for reducing the size of the system. Yet, various methods have been presented in the literature to increase the heat transfer rate from an absorber to the heat transfer fluid. The most important methods are: the use of evacuated receivers, addition of swirl generators/turbulators and use of various nanofluids as the heat transfer fluid. Objective: The current study reviews the achievements in the enhancement of solar collectors’ heat transfer process using various types of nanofluids. The review revealed that the most widely employed nanoparticles are Al2O3 and Carbon nanotubes (CNTs) and the most popular base fluid is water. Most of the investigations are performed on indirect solar collectors, while recently, the researchers focused on direct absorption methods. In the indirect absorption collectors, the thermal conductivity of the working fluid is essential, while in a direct absorption collector, the optical properties are also crucial. Optimization of the optical parameters along with the thermophysical properties of the nanofluid is suggested for the applications of solar collector.

Change of Operation Parameters of Waste Incinerator by Formation of Deposits

2016 ◽  
Vol 832 ◽  
pp. 207-212
Author(s):  
Jiří Moskalík
Keyword(s):  
Heat Transfer ◽  
Flue Gas ◽  
Large Scale ◽  
Negative Impact ◽  
Municipal Waste ◽  
Working Fluid ◽  
Operating Parameters ◽  
Waste Incinerator ◽  
Gas Channel ◽  
Waste Incinerators

This article is focused on formation of unwanted deposits in the municipal waste incinerator and their influence on incinerator operation. The solid deposits build up on heat transfer surfaces in flue gas channel of waste incinerator. The power stations fired solid fuels sometimes can have problems with growing of deposits. On this point of view, the municipal waste incinerators are a special category, because the municipal waste contains a lot of different types of compounds. Formation of deposits on heat transfer surfaces has in generally bad influence on operating parameters of waste incinerator. Deposits decrease the heat transfer from the flue gas into the working fluid and thereby it reduces the efficiency of incineration facility. The effect of decreasing of heat transfer ability was investigated on large-scale waste incinerator in Brno, where were monitored changes of operating parameters before and after the planned shutdown of the device. Deposits can too affect the shape of flue gas channel and thereby reduce his size. It can have more negative impact on waste incinerator operation.

Substandard carbon-containing raw materials and methods of their thermochemical processing

2021 ◽  
Vol 1-2 (183-184) ◽  
pp. 89-109
Author(s):  
Dmytro Bryk ◽  
Myroslav Podolskyy ◽  
Yury Khokha ◽  
Oleksandr Lyubchak ◽  
Lesia Kulchytska-Zhyhaylo ◽  
...  
Keyword(s):  
Negative Impact ◽  
Raw Materials ◽  
Environmental Safety ◽  
Primary Energy ◽  
Environmental Indicators ◽  
Thermochemical Conversion ◽  
Energy Potential ◽  
Capital Costs ◽  
The World ◽  
Thermochemical Processing

The analysis of the structure of consumption of primary energy resources in the world and in Ukraine are carried out. It is shown that in recent decades the share of coal is stable at 25–30 % and does not show a tendency to decrease. Similar patterns are observed in Ukraine too. It is established that in Ukraine the energy potential of reserves of substandard carbon-containing raw materials is commensurate with the deposits of conditioned coal and can be used to increase the country's energy security. At the same time, the deterioration of environmental indicators in the world and in Ukraine requires an increase in the level of environmental safety in the use of carbon-containing raw materials and appropriate environmental modernization of its thermochemical conversion methods. The paper reviews the methods of thermochemical processing of substandard carbon-containing raw materials (pyrolysis and coking, hydrogenation, gasification) and shows that the gasification process, which allows processing of various substandard fuel resources in terrestrial and underground conditions, is the most promising for environmental safety use. It is shown that developed terrestrial gasification methods are characterized by insufficient productivity of gas generators, significant capital costs for their installation and negative impact on the environment. In addition, terrestrial processing of low-quality coal is not a waste-free technology and does not solve the problem of “secondary” gasification residues recycling. Some of these shortcomings can be eliminated by using the method of underground gasification, in which there is no need to extract coal to the surface, and secondary waste remains underground.

scholarly journals Determination of the electrical power increase at the generator terminals of a nuclear power plant unit at different condenser states

2021 ◽  
Vol 3 (8(111)) ◽  
pp. 60-67
Author(s):  
Kateryna Bratkovska ◽  
Yuliya Liush
Keyword(s):  
Heat Transfer ◽  
Electricity Generation ◽  
Capital Investment ◽  
Nuclear Power ◽  
Modular Design ◽  
Cooling Water ◽  
Steam Pressure ◽  
Heat Transfer Process ◽  
Thermal Calculation ◽  
Steam Turbines

It is shown that the technical condition of condensing devices of steam turbines largely determines the amount of electricity losses, reliable and economical operation of NPP units. Analysis of the heat transfer process in the condenser showed that the main causes of load reduction are determined by rising cooling water temperature and deviation of steam pressure from normal value. It is shown that among diagnostic parameters except leakage volumes there must be an assessment of contamination of the heat transfer surface which significantly affects the reduction of electricity generation. The modernization main points of the condenser of the Zaporizhzhya NPP power unit No. 3 on the principle of "block-modular" design developed by PJSC "Turboatom" and the characteristics of the condenser provided by the new design are considered. To reflect the real mode of operation of the condensing unit, it is proposed to model the contamination of the heat exchange surface and the presence of leakages in the condenser space using the method of thermal calculation of the condenser by iterative methods. It was found that reducing the increase in electricity generation as a result of the effects of the study factors can partially or even completely absorb the effect of upgrading the condenser plant. It will provide a significant increase in electricity generation with relatively low capital investment compared to construction of new NPP power units and improve the accuracy of power generation forecasts.

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