Size Of Blockage Research Articles

Estimation of Blockage Position, Geometry, and Solidity in Molten Salt Pipelines.

In solar thermal plants, the use of molten salt as a heat transfer fluid is an advantageous alternative, although it has some disadvantages such as the formation of salt plugs in the pipes due to possible stratification of the salt or its solidification. The aim of this study was to implement an electromagnetic acoustic transducer (EMAT) not only capable of identifying the position of the plug, but also of determining whether the plug blocks the entire conductive surface or, on the contrary, is partial, allowing the fluid to pass through a smaller section. The proposed transducer is intended to be minimally invasive, allowing it to be used in the same way as a temperature probe. To do so, it creates torsional waves in the pipe, which are then used for a combination of measurements: pulse-echo and attenuation of the acoustic waves. Two materials with different densities (silicone and cement) were used in the tests carried out, which made it possible to check that for a given size of blockage, it is possible to identify the type of material from which it is formed.

Thermal-hydraulics analysis of flow blockage events for fuel assembly in a sodium-cooled fast reactor

The subchannel code ATHAS-LMR has been improved for analyzing thermal-hydraulics characteristics of flow blockage events in the fuel assembly of a sodium-cooled fast reactor (SFR). Based on the in-depth study of the phenomenon of flow blockage and combined with the characteristics of fast reactor assembly, enhanced models for the wire-wrap spacer and convective heat transfer have been added to account for changes in transverse flow in the presence of blockages. And appropriate transverse mixing and local resistance model are also implemented in ATHAS-LMR-FB. The improved code has been assessed against experimental data obtained at adiabatic and diabatic conditions in SFR assemblies with simulated flow blockages. Good agreement between predictions and experimental data on velocity and temperature distributions downstream of the blockage has been observed. Comparison of predictions of various analytical tools have also been performed. Predictions of the improved ATHAS-LMR code are shown to be compatible with those of other analytical tools. An in-depth analysis of effects of location and size of blockage has been carried out for the fuel assembly of the China Experimental Fast Reactor. Boiling has been predicted to occur for blockage ratios greater than 55.61% at the central location of the fuel assembly. Peak cladding and coolant temperatures are predicted at the axial location 70% of the rod length (just downstream of the maximum local power position of the non-uniform axial power profile).

Identification of partial blockages in pipelines using genetic algorithms

A methodology to identify the partial blockages in a simple pipeline using genetic algorithms for non-harmonic flows is presented in this paper. A sinusoidal flow generated by the periodic on-and-off operation of a valve at the outlet is investigated in the time domain and it is observed that pressure variation at the valve is influenced by the opening size of blockage and its location. In this technique, the unsteady (steady oscillatory) pressure time series at only one location is required to identify two blockages. In the proposed methodology, the solution of the governing hyperbolic PDEs of pipe flow is obtained using the method of characteristics. For any piping system similar to the hypothetical pipe system used in the simulations, generalized best amplitude and best frequency of the valve operation are determined, which give maximum deviation in pressure responses for a specific blockage at different locations for a given constant-head reservoir. The generalized best amplitude and best frequency of the valve operation are also obtained for two blockages. Accuracy of the proposed methodology in identifying blockages in a hypothetical simple pipe system with increased noise in the simulated measurements is studied. A non-dimensional variable is proposed to determine whether the proposed methodology is applicable to isolate partial blockages in a piping system. Finally, the proposed methodology is experimentally validated on a laboratory piping system for a single blockage and two blockages.

Computational analysis of mixed convection heat transfer characteristics in lid-driven cavity containing triangular block with constant heat flux: Effect of Prandtl and Grashof numbers

The present numerical work explores the mixed convective flow and heat transfer analysis in top lid driven square cavity containing heated triangular block with constant heat flux (CHF) thermal condition. The fluid flow in the cavity is driven by top moving wall in +x direction, while all other walls are stationary. Governing equations are solved by using finite volume method (FVM) and SIMPLE scheme for range of pertaining parameters such as, Reynolds number (Re=1, 10, 50, 100, 500 and 1000), Prandtl number (Pr=1, 50, 100), and Grashof number (Gr=0, 102, 103, 104 and 105). The influence of size of blockage (b=10%, 20% and 30%) on momentum and heat transfer characteristics has also been explored. The physical insights of systems are delineated by analyzing variation of streamlines and isotherm contours; while the heat transfer characteristics are explored by using dimensionless heat transfer coefficient or Nusselt number (local as well as averaged values). It is observed that increase in Reynolds number enhances the heat transfer rate (Nusselt number) only up to Re=180–220, later, deterioration of heat transfer rate is observed. The critical (Recr) as well as stagnant (Restag) Reynolds number of heat transfer for present case are identified.

Detection of Partial Blockage in Single Pipelines

A methodology is presented for the detection of partial blockages in single pipelines by the frequency response method. A steady-oscillatory flow produced by the periodic opening and closing of a valve located at the downstream end is analyzed in the frequency domain by using the transfer matrix method, and a peak pressure frequency response at the valve is developed. The comparison between the peak pressure frequency responses obtained by using the frequency response method and the method of characteristics is satisfactory. If there is a single partial blockage in a piping system, its location may be detected by the pattern and the number of peaks in the peak pressure frequency response. The size of the partial blockage may be determined from the mean peak pressure fluctuation. For two partial blockages, the effective size of the blockages can be determined from the peak pressure frequency response. Knowing the pre- and postdevelopmental frequency responses of a system with an additional partial blockage, the location and size of this additional partial blockage can be detected.

Flow Testing Methods to Detect and Characterize Partial Blockages in Looped Subsea Flowlines

Looping subsea flowlines is one method being utilized for flow assurance. Looping allows the possibility of circulating chemicals and/or tools to remediate partial flowline blockages due to wax, paraffins, asphaltenes, hydrates, sand, and scale. This study considers if flow testing can provide an a priori knowledge of the presence and/or size of the partial blockage before remedial action is taken. The techniques developed are for single-phase liquid flow and can be applied during circulation operations in looped flowlines or in single-phase oil transportation lines. Using these models, a blockage map is created to indicate what size of blockage can be detected and what size of blockage can be characterized as to length and diameter of the restriction. Field-scale verification was obtained by placing fixed length and diameter partial blockages in the 9460-ft LSU flowloop (3.64-in. i.d.). Tests were conducted with liquid rates to 11 bpm (15,840 bbl/day) and pressures to 4000 psia.

Pattern recognition of temperatures produced by malfunctions in fast reactor fuel elements

The use of pattern recognition in interpreting temperature noise from monitoring thermocouples in LMFBRs has been studied. Blockages and other malfunctions in fuel-coolant passages produce temperature noise through the random mixing in coolant fluid turbulence. Other, benign, sources of temperature noise can make it difficult to interpret the noise. Pattern recognition can effectively unscramble the mixed signal and give an accurate measure of the size of the original malfunction. The study uses temperatures calculated by a turbulence model, and shows how a pattern-recognition classifier can be built to estimate the size of blockage from measurable features in the noise signal.