Written in EnglishRead online
Includes bibliographical references.
|Statement||sponsored by the Heat Transfer Division, ASME ; edited by F.B. Cheung, M.S. El-Genk.|
|Series||HTD ;, vol. 115, HTD (Series) ;, v. 115.|
|Contributions||Cheung, F. B., El-Genk, Mohamed S., American Society of Mechanical Enginers. Winter Meeting, American Society of Mechanical Engineers. Heat Transfer Division.|
|LC Classifications||TJ260 .A415 1989b|
|The Physical Object|
|Pagination||vii, 83 p. :|
|Number of Pages||83|
|LC Control Number||89046304|
Download Natural circulation in single-phase and two-phase flow
Naveen Kumar, in Single-Phase, Two-Phase and Supercritical Natural Circulation Systems, Effect of elevation The effect of center line elevation difference (Δ z c) between the sink and the source on the natural circulation flow rate is given in Fig.
A and B. Naveen Kumar, in Single-Phase, Two-Phase and Supercritical Natural Circulation Systems, Introduction Industrial natural circulation systems (NCSs) are quite complex in geometry and as such the phenomena taking place are not easy to understand and hence simple loop facilities are found to be useful in phenomena tracking.
Get this from a library. Natural circulation in single-phase and two-phase flow: presented at the Winter Annual Meeting of the American Society of Mechanical Engineers, San Francisco, California, December[F B Cheung; Mohamed S El-Genk; American Society of Mechanical Engineers.
Winter Annual Meeting; American Society of Mechanical Engineers. Natural circulation in a fluid filled closed loop is established by locating a heat sink in the loop at an elevation that is higher than the heat source.
The circulating fluid removes heat from source and transports it to the sink. The flow can be single phase or two phase. Two-Phase Fluid Flow.
Water at saturation conditions may exist as both a fluid and a vapor. This mixture of steam and water can cause unusual flow characteristics within fluid systems. Two-Phase Fluid Flow.
All of the fluid flow relationships discussed previously are for the flow of a single phase. This paper describes the mechanisms by which natural circulation flow was interrupted under single-phase and two-phase natural circulation conditions in APEX-CE.
Discover the world's research In fluid mechanics, two-phase flow is a flow of gas and liquid — a particular example of multiphase -phase flow can occur in various forms, such as flows transitioning from pure liquid to vapor as a result of external heating, separated flows, and dispersed two-phase flows where one phase is present in the form of particles, droplets, or bubbles in a continuous carrier phase (i.e.
This study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. The focus is on CLTPTs for electronics cooling that exhibit complex two-phase flow patterns due to. However, it is good practice to keep the hot fluid subcooled to prevent a change of phase from occurring.
It is possible to have natural circulation take place in two-phase flow, but it is usually more difficult to maintain flow. Various parameters can be used to indicate or verify natural circulation is occurring. This is dependent on plant type. literature relating to natural circulation and two -phase flow in natural circulation loops.
Section 3 gives a detailed formulation of the theoretical model developed and used to simulate and capture the thermal-hydraulic performance of the loop with the help of Q-Basic64 computer program.
Section 4 describes the experimental set-up and procedures. The behavior of boiling-induced two-phase natural circulation flow in the insulation gap was observed using a 1/ scaled experimental facility to simulate the APR(Advanced Power Reactor) A one-dimensional theoretical model has been used to analyze the steady state and stability performance of a single-phase, two-phase, and supercritical natural circulation in a uniform diameter rectangular loop.
Parametric influences of diameter, inlet temperature, and system pressure on the steady state and stability performance have been studied. A natural‐circulation loop with water as the circulating fluid was studied for a range of operation covering two‐phase flow. The work reported in this paper is concerned with the periodic oscillations of the flow rate and fluid temperature.
Two-Phase Natural Circulation. Two-phase natural circulation experiments were conducted in four uniform diameter loops of inside diameter 7, and mm with the length scales as shown in Figure 6(a).The steam separator, the condenser, and the associated piping (the portion inside the rectangular box in Figure 6(a)) were the same for all the loops.
The flow can be single phase or two phase wherein vapor flows alongside the liquid. The difference in temperature must be maintained for the natural circulation to continue.
Addition of heat by a heat source must exist at the high temperature area. In this paper, the flow characteristics in a single-phase natural circulation system were investigated and the effects of heaving, rolling and coupled motions were analyzed. The oscillation amplitude of flow rate increases with the increase of period in a certain range.
Principles, Experiments, and Numerical Studies of Supercritical Fluid Natural Circulation System: /ch Due to the unique thermal and transport properties, supercritical natural circulation loop (NCL, or thermosyphon) has been proposed in many energy systems.
Natural circulation usually arises in a closed loop between a heat source and a heat sink were the fluid motion is driven by density difference. It may also occur in enclosures or cavities where the flow is induced primarily by temperature or concentration gradients within the fluid.
The subject has. Pressure drop in two-phase flow is a major design variable, governing the pumping power required to transport two-phase fluids and also governing the recirculation rate in natural circulation systems.
The conservation equations for two-phase flow are a subset of those for Multiphase Flow. on natural circulation loops. Misale (Misale et al., ) reports an experimental investigations related to rectangular single-phase natural circulation mini-loop.
Ramos (Ramos et al., ) performed the theoretical study of the steady st ate flow in the two-ph ase thermosyphon loop with conventional tube. Single and Two-Phase Flow Thermal Hydraulics held at University of Pisa from June 19 to 30, Natural Circulation in Single-Phase Flow (9 pages) Unit 5b – Notes on Compressible Single-Phase Flow (14 pages) An old but still interesting general book on reactor safety and related phenomena.
In this work, a hybrid ultrasonic technique for diagnostic natural circulation gas-liquid two-phase flow is experimentally investigated. The method is applied on a two-phase natural circulation loop using a contrapropagating transmission flow rate measurement technique in the single phase section and a Doppler velocity measurement and single transducer pulse echo technique in the two-phase region.
The term 'two-phase flow' is also applied to mixtures of different fluids having different phases, such as air and water, or oil and natural gas.
Sometimes even three-phase flow is considered, such as in oil and gas pipelines where there might be a significant fraction of solids. Characteristics of two-phase flow: Several features make two.
Single-Phase, Two-Phase and Supercritical Natural Circulation Systems provides readers with a deep understanding of natural circulation systems. This book equips the reader with an understanding on how to detect unstable loops to ensure plant safety and reliability, calculate heat transport capabilities, and design effective natural circulation.
Scaling criteria for a natural circulation loop under single- and two-phase flow conditions are derived from the fluid balance equations, boundary conditions, and solid energy equations.
For a single-phase flow case, the continuity, integral momentum, and energy equations in one-dimensional area-averaged forms were used. Natural circulation flow behavior at reduced inventory in a VVER geometry Puustincn, M CIRCUS; a natural circulation two-phase now facility de Kruijf, W.J.M., Van dcr Hagcn, T.H.J.J., and.
Muddc, R.F Sensitivity to parameters in single-phase natural circulation via automatic differentiation of Fortran codes Ambrosini, W., and Ferreri, J. The aim of this paper is to collect and resume the work done to build and develop, at the University of Pisa, an engineering tool related to the natural circulation.
After a brief description of the different loop flow regimes in single phase and two phase, the derivation of a suitable tool to judge the NC performance in a generic system is presented.
An experimental investigation was conducted in a natural circulation (NC) loop to study the characteristics of two-phase flow instability under low pressure condition.
A 3 × 3 rod bundle channel was used as the test section. The conclusion is that sales gas transmission has to be treated as a single-phase flow and not as a "probable" two-phase flow. Also there is an inference that copying from a book does not make it entirely true and one has to do an indepth study of the subject before coming to any conclusions.
In two-phase flow, presenting the Chisholm constant (C) In natural circulation systems, the pressure drop dictates the circulation rate, and hence the other system parameters. In forced circulation systems, the pressure drop governs the pumping requirement. The homogeneous model considers the two-phase flow as a single-phase flow having.
m= v+(1‐) ℓ, used instead of the single‐phase density. The friction factor in Eq. 3 can be calculated from a single‐phase correlation and using the “liquid‐only” Reynolds number, Reℓo =GDe/ ℓ. For each abrupt flow area change in the channel (again including the inlet and outlet), the associated.
The Pennsylvania State University The Graduate School College of Earth and Mineral Sciences NUMERICAL MODELING OF NATURAL GAS TWO-PHASE FLOW SPLIT. The wide range of applications of two-phase natural circulation loops (NCLs) demands intense analyses of boiling systems, and consequently a large number of experimental and theoretical research findings are available in the literature.
There are a number of instabilities that may occur in two-phase systems. These may be classified into static and dynamic instabilities [Lahey andPodowski ()]. are the transfer functions of the single-phase and two-phase parts of the loop, Ledinegg, M.
() "Instability of flow during natural and forced circulation," Die Wärme, Natural and forced circulation systems for large devices (magnets) Forced flow superconductors for large magnets Cryogenic systems frequently experience a variety of fluid flow conditions: Single phase, subcooled liquid (incompressible) Compressible fluid flow (gases) Two phase flow.
Natural circulation based reactor designs are being studied even with supercritical water as coolant [5, 6]. In view of their wide application, both single-phase and two-phase natural circulation systems are being extensively studied.
State-of-the-art reviews on single-phase [7, 8]and two-phase [9, 10] natural circulation have been provided by. single-phase flows. However, the interactive effects of two-phase flows and fouling mechanisms are poorly understood.
Many of the industrial heat exchangers in refining and petrochemical processing operate under multi-phase flow conditions with varying flow regimes. Fouling and localized corrosion are generally experienced due to maldistribution of. single-phase natural circulation, two-phase natural circulation can also occur if there is progressive decrease of system inventory following a LOCA situation.
With decrease in system inventory, the pressure in the system also falls gradually and the decay power also reduces with time. Hence, it is. mechanism causing NC flow due to the strong coupling between the flow and the driving force. As a result, both single-phase and two-phase natural circulation systems exhibit instability where as only forced circulation two-phase systems are known to exhibit instability.
Even among two-phase systems. Heat transfer rate, pressure drop and temperature distribution of single phase (supercritical, liquid and vapor) and two-phase CO 2 based NCL compared with water/brine based natural circulation. The progressive electrification of the energy supply in airplanes leads to an increasing demand for innovative cooling technologies.
Due to high efficiency and low weight two-phase natural circulation cooling systems provide high potential for this application. Extension to Two-Phase Flow due to Bulk Boiling in the Riser The flow bulk boiling occurs when the flow enters the reactor core in the saturation state.
Assuming homogeneous flow as a convenient approximation, the same equations for single phase flow apply but with altered numerical values of the coefficients.In others, a two-phase mixture flows downward and vapor flows upward.
As long as one line has a higher time-averaged density than the other, circulation will occur. An LTS self-determines both the pressure and the flow rate, and the flow rate is often unstable: intense, short time-scale oscillations and even temporary flow reversals are common.