An Experimental Study of Thermal Performance of a Two-Phase Loop Thermosyphon (TPLT)-Based Steam Generator: Effects of Thermal Boundary Conditions

For the Parabolic trough collector (PTC) system, thermal boundary condition of the receiver (or heating section) is important for the thermal optimization. In this work, effects of thermal boundary on thermal performance of the two-phase loop thermosyphon (TPLT) natural circulation PTC system was investigated experimentally. Three kinds of thermal boundary heating conditions (upper and lower half, and whole circular heated) and two filling ratios (FR = 0.6, 1.2) were adopted in this paper. The results show that half heating condition can improve heat transfer performance in receiver and system thermal resistance. But the preferred half heating boundary was varied as the filling ratio was changed. However, a lower thermal efficiency was observed for the partly heating boundary conditions. For a low heat flux condition in this work, the effects of thermal boundary on flow instability were not obvious, especially for the bigger filling ratio condition.

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Experimental observation of flow instability in a semi-closed two-phase natural circulation loop

Nuclear Engineering and Design ◽

10.1016/s0029-5493(99)00296-4 ◽

2000 ◽

Vol 196 (3) ◽

pp. 359-367 ◽

Cited By ~ 24

Author(s):

Jong Moon Kim ◽

Sang Yong Lee

Keyword(s):

Experimental Observation ◽

Flow Instability ◽

Natural Circulation ◽

Circulation Loop ◽

Two Phase ◽

Natural Circulation Loop

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Experimental study on Ledinegg flow instability of two-phase natural circulation in narrow rectangular channels at low pressure

Progress in Nuclear Energy ◽

10.1016/j.pnucene.2017.04.011 ◽

2017 ◽

Vol 98 ◽

pp. 321-328 ◽

Cited By ~ 6

Author(s):

Shi Qi ◽

Tao Zhou ◽

Bing Li ◽

Muhammad Ali Shahzad ◽

Yaxiong Zou ◽

...

Keyword(s):

Experimental Study ◽

Flow Instability ◽

Natural Circulation ◽

Low Pressure ◽

Two Phase ◽

Rectangular Channels

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Experimental Study on Two-Phase Natural Circulation Flow Instability in Rod Bundle Channel Under Low Pressure Condition

Volume 6A: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-81225 ◽

2018 ◽

Author(s):

Kun Cheng ◽

Sichao Tan ◽

Zheng Liu ◽

Tao Meng

Keyword(s):

Flow Instability ◽

Natural Circulation ◽

Oscillation Amplitude ◽

Density Wave ◽

Low Pressure ◽

Heating Power ◽

Pressure Condition ◽

Two Phase ◽

Rod Bundle ◽

System Pressure

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 effects of heating power, inlet subcooling degree and system pressure on the two-phase NC flow instability types and stable boundaries were studied. The experimental results show that three typical flow conditions can occur in rod bundle channel under NC condition, which are single-phase NC flow, subcooled boiling NC flow oscillation and density wave oscillations (DWO). The oscillation amplitude and period of DWO can be enlarged by increasing the heat flux. Increasing the inlet subcooling degree can increase the marginal heating power of flow instability in NC system. The occurrence of DWO can be suppressed by increasing the system pressure. The flow instability boundary presented by the subcooling number and phase change number was also obtained in present work.

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Non-Linear Time Series Analysis of the Infuence of Rolling Motion on Natural Circulation System

18th International Conference on Nuclear Engineering: Volume 4, Parts A and B ◽

10.1115/icone18-29351 ◽

2010 ◽

Author(s):

Wenchao Zhang ◽

Sichao Tan ◽

Puzhen Gao

Keyword(s):

Experimental Data ◽

Time Series ◽

Time Series Analysis ◽

Two Phase Flow ◽

Flow Instability ◽

Natural Circulation ◽

Rolling Motion ◽

Phase Flow ◽

Two Phase ◽

Series Analysis

Two-phase natural circulation flow instability under rolling motion condition was studied experimentally and theoretically. Experimental data were analyzed with nonlinear time series analysis methods. The embedding dimension, correlation dimension and K2 entropy were determined based on phase space reconstruction theory and G-P method. The maximal Lyapunov exponent was calculated according to the methods of small data sets. The nonlinear features of the two phase flow instability under rolling motion were analyzed with the results of geometric invariants coupling with the experimental data. The results indicated that rolling motion strengthened the nonlinear characteristics of two phase flow instability. Some typical nonlinear phenomena such as period-doubling bifurcations and chaotic oscillations were found in different cases.

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The Research of Flow Instability in Vertical Parallel Natural Circulation Channels Based on Relap5

Volume 4: Thermal Hydraulics ◽

10.1115/icone21-15686 ◽

2013 ◽

Author(s):

Jingjing Li ◽

Tao Zhou ◽

Mingqiang Song ◽

Yanping Huang

Keyword(s):

Two Phase Flow ◽

Single Channel ◽

Flow Instability ◽

Natural Circulation ◽

Computer Code ◽

Phase Flow ◽

Flow Oscillation ◽

Two Phase ◽

Best Estimate ◽

Estimate System

The gas-liquid two phase flow oscillation in vertical parallel natural circulation channels was performed by the best estimate system computer code Relap5. The effects of symmetry and dissymmetry degree of heated power to flow oscillation and the effects of symmetry and dissymmetry throttling to flow oscillation were researched. The results says that when the twin channels under the same conditions of geometry and boundary, the parameters of the twin channel such as flow are the same. So under these conditions the twin channels can be researched as single channel. It is more possible of flow oscillation for the channels under condition of dissymmetry heating. The use of throttling will make the channels more stable, it is more stable when the throttling coefficient increases. With the implement of dissymmetry throttling, the system is possible for out of phase flow oscillation.

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A Comprehensive Experimental Investigation of the Performance of Closed-Loop Pulsating Heat Pipes

Journal of Heat Transfer ◽

10.1115/1.4036460 ◽

2017 ◽

Vol 139 (9) ◽

Cited By ~ 1

Author(s):

M. Halimi ◽

A. Abbas Nejad ◽

M. Norouzi

Keyword(s):

Thermal Resistance ◽

Flow Regime ◽

Thermal Performance ◽

Closed Loop ◽

Heat Pipes ◽

Filling Ratio ◽

Working Fluid ◽

Physical Parameters ◽

Two Phase ◽

Laboratory Conditions

Closed-loop pulsating heat pipes (CLPHPs) are a new type of two-phase heat transfer devices that can transfer considerable heat in a small space via two-phase vapor and liquid pulsating flow and work with various types of two-phase instabilities so the operating mechanism of CLPHP is not well understood. In this work, two CLPHPs, made of Pyrex, were manufactured to observe and investigate the flow regime that occurs during the operation of CLPHP and thermal performance of the device under different laboratory conditions. In general, various working fluids were used in filling ratios of 40%, 50%, and 60% in horizontal and vertical modes to investigate the effect of thermo-physical parameters, filling ratio, nanoparticles, gravity, CLPHP structure, and input heat flux on the thermal performance of CLPHP. The results indicate that three types of flow regime may be observed given laboratory conditions. Each flow regime exerts a different effect on the thermal performance of the device. There is an optimal filling ratio for each working fluid. The increased number of turns in CLPHP generally improves the thermal performance of the system reducing the effect of the type of the working fluid on the aforementioned performance. The adoption of copper nanoparticles, which positively affect fluid motion, decreases the thermal resistance of the system as much as 6.06–42.76% depending on laboratory conditions. Moreover, gravity brings about positive changes in the flow regime decreasing thermal resistance as much as 32.13–52.58%.

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Analytical Study of Two-Phase Flow Instability in a Natural Circulation PWR Auxiliary Feedwater System

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2013-97123 ◽

2013 ◽

Author(s):

Jong Chull Jo ◽

Frederick J. Moody ◽

Kyu Sik Do

Keyword(s):

Water Level ◽

Two Phase Flow ◽

Flow Instability ◽

Natural Circulation ◽

Circulation Loop ◽

Phase Flow ◽

Vertical Pipe ◽

Two Phase ◽

Pipe Section ◽

Natural Circulation Loop

A PWR incorporates a passive auxiliary feedwater system (PAFS), a closed natural circulation loop which is aligned to feed condensed water to its corresponding steam generator (SG). During its operation, saturated steam in the SG secondary side moves up due to buoyancy force and passes through a steam line, and then flows into a tube-tank type passive condensation heat exchanger where steam is condensed inside the tubes while the tube outer surfaces are cooled by the pool water. The condensate water is passively fed into the SG economizer by gravity. Because a natural circulation loop is susceptible to two-phase flow instability, it is requisite to confirm the system is designed adequately to avoid the potential challenges to its operational safety due to the instability. This paper presents an analytical approach for assessing if the PAFS has possible thermal and fluid mechanical characteristics which could lead to an undesirable unstable or oscillating condensate water level in the vertical pipe section. Both steady and unsteady analytical solutions for a simplified natural circulation loop model of the PAFS were derived in terms of the condensate water level and velocity in the vertical pipe section. From the solutions, the criteria for determining a potential for two-phase instability in the system were obtained.

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