Coolant Flow Parameters Research Articles

The Multifunctional Nuclear Magnetic Flowmeter for Control to the Consumption and Condition of Coolant in Nuclear Reactors

The necessity of coolant flow consumption measurement accuracy increase in the nuclear reactor primary circuit has been substantiated. Additionally, the need to control the coolant condition in the current flow inside the pipeline is shown. Nowadays, the real-time coolant’s condition control function is not implemented at stationary nuclear power plants or mobile nuclear power plants used in moving objects. It is shown that a coolant consumption measurement error decreases and its condition data availability increases the heat transfer efficiency and the electrical energy generation (without the nuclear reactor and steam generator design change). Problems arising during coolant consumption control using various flowmeters models in the nuclear reactor primary circuit are considered. It has been found that nuclear magnetic flowmeters can solve these problems. New difficulties are noted as emerging when using pulsed nuclear magnetic flowmeters designs developed for measuring hydrocarbons, water, biological compounds consumption, and condition control. A new nuclear magnetic flowmeter design has been developed using a modulation technique for nuclear magnetic resonance signal recording. Methods for measuring the coolant flow’s longitudinal T1 and transverse T2 relaxation times are presented. Investigations of coolant flow parameters (consumption and relaxation times) inside the pipeline have been carried out. It is found that the measurement error for these parameters does not exceed 1%. The prospects of using the developed nuclear magnetic flowmeter-relaxometer design in the nuclear reactor first circuit are shown.

Studies of critical heat fluxes in small diameter channels

The paper presents the results of experimental studies of critical heat flows in vertical small diameter channels, when the coolant moves from bottom to top, which were carried out in the Obninsk branch of MEPhI in the 1970s of the last century but have not become widespread due to the lack of demand for their practical use. Nowadays, the interest in such works is manifested, first of all, in the development of compact plants and devices, particularly in nuclear power engineering. As a coolant, water, Freon-12 and 96% ethyl alcohol were used. High velocities of underheated liquid at high heat fluxes on the channel wall lead to the so-called “fast crisis” of heat transfer. In this case, the magnitude of the heat flux depends mainly on the parameters of the coolant flow in the wall zone rather than the flow core. The “slow crisis” is mainly observed at high vapor concentrations, relatively low mass flow rates and in an annular-dispersed flow. The value of the critical heat flow in this case depends mainly on the flow parameters in the core, which are probably close to the average coolant flow parameters. The conditions in the near-wall region are also largely determined by the flow in the core. High heat transfer coefficients in a flow moving at high speed usually result in a much smaller and slower rise in the wall temperature. Sometimes a DNB heat flux can occur bypassing the boiling process. In the core of a VVER-type reactor operating in its nominal mode, surface boiling is present in a number of fuel rods. Probably, surface boiling will also be present in transportable and small-size nuclear power plants. Therefore, an important task is to conduct relevant research in this area.

Stability analysis on flow parameters in coolant temperature control system of lead-cooled fast reactor

Lead-cooled Fast Reactor (LFR), one of the promising nuclear energy technologies for future advanced system, is well foreseen in meeting the goals of Generation IV fission reactor. In LFR, Coolant Temperature Control System (CTCS) is one of the critical parts, and the influence of coolant flow parameters on the stability analysis is worth investigating and studying. In this paper, we use the CLEAR-S, an integrated multifunctional non-nuclear test facility, as reference and the stability analysis of CTCS, concerned to coolant flow rate has been completed based on simplified coolant thermal circulation model. Location of eigenvalues and calculation results of real stability radius, both qualitatively and quantitatively reflect the influence of coolant flow rate on stability respectively. The analysis results show that the feed-water flow rate in steady state is a critical parameter for CLEAR-S, because larger feed-water flow rate can improve stability apparently. However, LBE coolant flow rate has little impact on system stability. The results of this work will provide an effective reference for design and operation of LFR.

Obtaining of Analytical Relations for Hydraulic Parameters of Channels With Two Phase Flow Using Open CFD Toolbox

The present work is dedicated to verification of numerical model in standard solver of open-source CFD code OpenFOAM for two-phase flow simulation and to determination of so-called “baseline” model parameters. Investigation of heterogeneous coolant flow parameters, which leads to abnormal friction increase of channel in two-phase adiabatic “water-gas” flows with low void fractions, presented.

Film cooling effectiveness for three-row compound angle hole design on flat plate using PSP technique

This paper investigates effects of geometrical and coolant flow parameters for a three-row compound angle hole design over a flat plate. These included β=+45° and −45°, in-line and staggered arrangement, hole spacing (4d, 6d and 8d), five blowing ratios (0.5–1.5) and three density ratios (1.0, 1.5, 2.0). Spanwise averaged effectiveness plots and contours were developed using Pressure-Sensitive Paint (PSP) technique and cross comparisons were carried out. The parametric results obtained from experiment generally agreed with widely accepted trends: the cascade effect of coolant jets for multi-hole design increases film effectiveness especially at large x/d, increasing density ratio increases effectiveness particularly at higher blowing ratio and increasing hole spacing has a detrimental effect on film cooling. However, some interesting observations are discovered including: staggered arrangement is not always the most optimum design (β=+45°, −45°, −45° with staggered 2nd and 3rd row reported the lowest effectiveness for all blowing ratios and density ratios); in-line arrangement of holes with opposing orientation angles (β=+45°, −45°, −45°) yields better effectiveness; blowing ratio effect is strongly dependent on geometric design. Moreover, hole spacing effect is closely related to neighboring coolant jet coalescence and interaction with mainstream flow. Currently, little data is available on three-row design in open literature; this study provides systematic, baseline information for future studies.

Investigation of heat transfer and pressure drop in an annular channel with heat transfer intensifiers

Results from systematic investigations of heat transfer and pressure drop for water flow in an annular channel using an efficient method for enhancing heat transfer on a convex heating surface are presented. The main technical data of the thermal-hydraulic experimental setup are given together with a brief description of the control, monitoring, and physical parameters measurement and recording systems, as well as primary experimental data processing and storage system. The test section, the enhancement method based on setting up swirl flows, the geometrical characteristics of intensifiers, their schematic design, and installation technology are described. The experimental data are obtained in a wide range of coolant flow parameters under the conditions of single-phase convection with using intensifiers having different shapes. The test measurements carried out on a smooth annular channel showed good agreement with the classic correlations both for heat transfer and pressure drop, thereby confirming reliability of the experimental data. A considerable improvement in heat removal efficiency on the convex heating surface is obtained. The value of heat transfer coefficient is a factor of 1.8 higher than it is for smooth annular channels. The region of the values of intensifier geometrical characteristics and Reynolds numbers for which the growth of heat transfer prevails over the growth of pressure drop is established. It is shown that the maximums of heat transfer and pressure drop are observed at quite definite values of intensifier geometrical characteristics. The primary experimental data are processed and presented as a dependence of the Nusselt number on the Reynolds number for different values of the intensifier’s relative fin height Ḣ. The value of Ḣ at which heat transfer reaches its maximum is found. The experiments were carried out in the pressure range p = 3.0–10.0 MPa and at the constant temperature of liquid at the test section inlet equal to 100°C. The influence of peripheral liquid flow swirling pitch on heat transfer and pressure drop is studied. An empirical correlation describing the dependence of heat transfer on the intensifier geometrical characteristics is obtained.

Aerothermal Optimization and Experimental Verification for Discrete Turbine Airfoil Film Cooling

The optimization aims to maximize the film cooling performance while minimizing the corresponding aerodynamic penalty. The cooling performance is assessed using the adiabatic film cooling effectiveness, while the aerodynamic penalty is measured with a mass-averaged total pressure loss coefficient. Two design variables are selected: the coolant-to-mainstream temperature ratio and the coolant-to-mainstream total pressure ratio. Two staggered rows of discrete cylindrical film cooling holes on the suction surface of a turbine vane are considered. A nondominated sorting genetic algorithm (NSGA-II) is coupled with an artificial neural network (ANN) to perform a multiple-objective optimization of the coolant flow parameters on the vane suction surface. Three-dimensional Reynolds-averaged Navier–Stokes (RANS) simulations are employed to construct the ANN network that produces low-fidelity predictions of the objective functions during the optimization. The effect of varying the coolant flow parameters on the adiabatic film cooling effectiveness and the aerodynamic loss is analyzed using the optimization method and RANS simulations. The computational fluid dynamics predictions of the adiabatic film cooling effectiveness and aerodynamic performance are assessed and validated against corresponding experimental measurements. The optimal solutions are reproduced in the experimental facility and the Pareto front is substantiated with experimental data.

Electromagnetic and Thermal Analysis of Open-Circuit Air Cooled High-Speed Permanent Magnet Machines With Gramme Ring Windings

This paper investigates the electromagnetic and thermal performances of the open-circuit air cooled high-speed permanent magnet motor (HSPMM) with Gramme ring windings. Take a 36 kr/min, 75 kW HSPMM as an example, the electromagnetic losses, in particular the rotor eddy current loss and the stator iron loss of the motor are calculated. The influences of switching frequency and air gap length on these losses are studied. Then, a computational fluid dynamics (CFD) model is composed to calculate its coolant flow parameters and the temperature distribution. Based on the CFD results, a lumped-parameter thermal network (LPTN) is created and verified. Then, a 24 kr/min, 140 kW prototype with the same structure and cooling configuration is designed using the LPTN. Experiments show that the calculated results are with reasonable accuracy. Finally, a sensitivity analysis is applied to the 140 kW prototype based on the LPTN to disclose the influences of different parameters on the rotor permanent magnet temperature rise.

Analytical benchmarks for verification of thermal-hydraulic codes based on sub-channel approach

Over the last year (2007), preliminary tests have been performed on the Moroccan TRIGA MARK II research reactor to show that, under all operating conditions, the coolant parameters fall within the ranges allowing the safe working conditions of the reactor core. In parallel, a sub-channel thermal-hydraulic code, named SACATRI (Sub-channel Analysis Code for Application to TRIGA reactors), was developed to satisfy the needs of numerical simulation tools, able to predict the coolant flow parameters. The thermal-hydraulic model of SACATRI code is based on four partial differential equations that describe the conservation of mass, energy, axial and transversal momentum. However, to achieve the full task of any numerical code, verification is a highly recommended activity for assessing the accuracy of computational simulations. This paper presents a new procedure which can be used during code and solution verification activities of thermal-hydraulic tools based on sub-channel approach. The technique of verification proposed is based mainly on the combination of the method of manufactured solution and the order of accuracy test. The verification of SACATRI code allowed the elaboration of exact analytical benchmarks that can be used to assess the mathematical correctness of the numerical solution to the elaborated model.

Effects of heat-transfer rate and coolant flow parameters on heating and cooling rates

It is shown that change in the heat-transfer coefficient over a wide range does not alter the heating or cooling rate, which is determined by the heat transfer along the flow.

Transient temperature response of a porous matrix entering a planetary atmosphere

An analysis is made of the transient temperature behavior of a transpiration-cooled porous matrix entering a planetary atmosphere with constant velocity and negative entry angle. The analysis is based on one dimensional heat conduction in a porous plate subjected to a time dependent heat flux at one side and cooled internally by mass injection from a constant temperature reservoir at the opposite side. An exact closed-form solution is obtained and temperature charts are presented for a wide range of Fourier number and coolant flow parameters.