Search results for "pressure drop"
showing 10 items of 57 documents
Online measurement of floc size, viscosity, and consistency of cellulose microfibril suspensions with optical coherence tomography
2021
AbstractIn this study, cellulose microfibril (CMF) suspensions were imaged during pipe flow at consistencies of 0.4%, 1.0%, and 1.6% with optical coherence tomography (OCT) to obtain images of the structure and the local velocity of the suspension. The viscosities obtained by combining pressure loss measurement with the OCT velocity data showed typical shear thinning behavior and were in excellent agreement with viscosities obtained with ultrasound velocity profiling. The structural OCT images were used to calculate the radial and the axial floc sizes of the suspension. A fit of power law to the geometrical floc size–shear stress data gave the same power law index for all consistencies, sug…
Analyses of single- and two-phase flow pressure drops in helical pipes using a modified RELAP5 code
2012
Abstract Thermal fluid dynamics analyses on single- and two-phase flows in helical pipes of steam generators to be used in Generation III and IV nuclear reactors have been performed. The study concerned with experimental activities as well code simulations carried out in the framework of a collaboration between the Department of Energetics of the Polytechnic of Torino and the Department of Energy of the University of Palermo. The goal was the validation of models implemented in Relap5/Mod3.2β thermal–hydraulic advanced code to simulate the hydrodynamic behaviour of helical pipe components in spite of the one-dimensional nature of the code. It is shown that much of the experimental data obta…
A semi-empirical approach for predicting two-phase flow discharge through branches of various orientations connected to a horizontal main pipe
2010
Abstract The subdivision of two-phase flow in branching conduits consisting of a large horizontal main pipe with upward, downward, or lateral branches of reduced diameter is of great interest in various technological fields. For example, these conduits are important in light-water nuclear reactors (LWRs) in the case of a small break loss-of-coolant accident (SBLOCA) in a leg of the reactor's primary coolant loops, as well as for breaks or valve malfunctions in a large pipeline. In these kinds of circumstances, the relevant phenomenology often involves phase stratification coupled with possible liquid entrainment or gas pool-through phenomena. Therefore, these phenomena were studied in depth…
Hydrodynamics of a cocurrent downflow of gas and foaming liquid through the packed bed. Part II. Liquid holdup and gas pressure drop
2003
Abstract In the present study the results of experiments have been presented whose aim was to determine the values of liquid holdup as well as gas pressure drop through the packing for systems foaming under the pulse flow regime. On the basis of 245 experimental points for the pulse flow regime the verification of the models describing the hydrodynamics of the system has been performed. Attention was focused on the models of Benkrid et al. (Chem. Eng. Sci. 52 (1997) 4021), Pina et al. (AIChE J. 47 (2001) 19) and Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987). It has been concluded that none of the models analysed describes the hydrodynamics of the foaming systems with enough accuracy. Next,…
Modifications induced in the renin-angiotensin-aldo-sterone system of rats by alpha-blocking drugs.
1978
Summary The data reported in the present paper refer to quantitative variations of plasma renin activity and plasma aldosterone levels after administration of alpha-blocking agents, i.e. phentolamine, phenoxybenzamine and gihydroergotoxin derivatives, either to rats kept on a standard diet with water ad libitum or to rats receiving distilled water load, the latter treatment causing an increase of both plasma renin activity and plasma aldosterone levels if compared to control values. No strict correlation between (a) drug-induced modifications of plasma renin activity and plasma aldosterone levels and (b) blood pressure drop caused by the same drugs was shown to occur under either experiment…
Loop seals in circulating fluidized beds – Review and parametric studies using CPFD simulation
2020
Abstract Loop seal is a robust particle recycling technique used in circulating fluidized bed (CFB) reactors. The rate and the location of the loop seal aeration exert a significant impact on the rate of particle circulation (GS). The standpipe balances the cumulative pressure drop across the rest of the CFB by adjusting its particle height or gas-particle slip velocity. Higher fraction of the loop seal aeration naturally flows down to riser. Increased pressure drop in the standpipe results in high rate of particle circulation. Computational-particle-fluid-dynamic (CPFD) code is customized for multiphase flow modelling. The inbuilt tool of “BC connectors” was incorporated to downsize a CFB …
Numerical simulation of nanofluids for improved cooling efficiency in a 3D copper microchannel heat sink (MCHS)
2017
ABSTRACTIn this paper, laminar nanofluid flow in 3D copper microchannel heat sink (MCHS) with rectangular cross section, and a constant heat flux, has been treated numerically using the computational fluid dynamics software (FLUENT). Results for the temperature and velocity distributions in the investigated MCHS are presented. In addition, experimental and numerical values are compared in terms of friction factors, convective heat transfer coefficients, wall temperature and pressure drops, for various particle volume concentrations and Reynolds numbers. The numerical results show that enhancing the heat flux has a very weak effect on the heat transfer coefficient for pure water, but an appr…
An enhanced, near-term HCPB design as driver blanket for the EU DEMO
2019
The Helium Cooled Pebble Bed (HCPB) breeding blanket is a candidate as driver blanket for the EU DEMO. The reference design of the HCPB is based on a cooling plate “sandwich” arrangement built in Multi-Module Segments. This architecture significantly improved the tritium breeding performance (TBR = 1.15) and the plant circulating power (≈130 MW) compared to the former ITER-like “beer-box”-like design (TBR<1.10, plant circulating power>200 MW). However, several issues remain with this design, in which (1) the still large power required per He circulator (beyond the state-of-the-art for these components) and (2) the large tritium inventory foreseen in Be have been identified as the most…
Simplified Procedure to Evaluate Head Losses in Drip Irrigation Laterals
2005
The lateral lines of a drip irrigation system consist of pressurized pipelines with inline or online emitters. Proper hydraulic design of drip laterals usually requires the accurate evaluation of the total head losses, represented by friction losses along the pipe and the emitters, and local losses due to the emitter connections. This paper extends the local loss evaluation procedure, previously obtained for coextruded laterals, on the basis of new experiments. In addition, a simplified procedure was proposed based on the constant outlet discharge assumption for a quick evaluation of total head losses in drip irrigation lines, taking into account the total local loss due to the emitter conn…
Flow and Heat Transfer in Corrugated Passages: Direct and Large Eddy Simulation and Comparison with Experimental Results
1993
Direct and large-eddy numerical simulations are presented for the transitional and turbulent flow with heat transfer in corrugated passages, representative of compact heat exchangers such as rotary air preheaters (regenerators), at Reynolds number ranging from 103 to 104. Pressure drop and heat transfer results are compared with wind-tunnel experimental data; the agreement is quite satisfactory, and superior to that obtained by more traditional methods.