Terms Of Heat Load Research Articles

Magnetohydrodynamic velocity and pressure drop in manifolds of a WCLL TBM

In the frame of the EUROfusion breeding blanket research activities, the water cooled lead lithium (WCLL) blanket is considered as reference liquid metal blanket design to be tested in ITER and to be used in a DEMO reactor. The design of breeding blankets represents a major challenge for fusion reactor engineering because of the performance requirements and the severe operating conditions in terms of heat load and neutron flux. Liquid metal alloys such as lead-lithium, PbLi, are considered as breeder material, due to their lithium content required for tritium production, and as heat transfer medium because of their large thermal conductivity and the possibility to be operated at high temperature. On the other hand, the motion of the electrically conducting breeder in the plasma-confining magnetic field induces electric currents and generates strong electromagnetic forces that modify significantly the velocity distribution in the blanket compared to hydrodynamic conditions and increase pressure losses. Magnetohydrodynamic (MHD) pressure drops have to be carefully quantified, since excessive values can jeopardize the feasibility of the considered blanket concept. The present work investigates numerically liquid metal MHD flows in manifolds of a WCLL test blanket module. Velocity and pressure distributions are analyzed.

MHD flow in liquid metal blankets: Major design issues, MHD guidelines and numerical analysis

The design of breeding blankets represents the major challenge for fusion reactor engineering because of performance requirements and severe operating conditions in terms of heat load and neutron flux. Liquid metal alloys such as lead-lithium, due to their lithium content, can be used to breed tritium, one of the plasma fuel components, and owing to their high thermal conductivity, they may serve as coolants. On the other hand, there are technical issues related to the fact that the liquid metals are electrically conducting and interact with the plasma-confining magnetic field. Induced electric currents and generated electromagnetic forces affect velocity and pressure distribution in the blankets. Magnetohydrodynamic (MHD) flows for fusion applications have been often investigated in simplified geometries, such as pipes, ducts, bends, with focus on their fundamental features. These analyses are essential, since results remain valid as background for the development of blanket designs, even when a concept is dismissed. However, the conceptual study of fusion blankets requires to take into account the global multiple effects, that arise when the full system is considered. Progress made in fusion-related MHD research results from combined numerical and experimental activities. In this paper we review and summarize features of 2D and 3D MHD flows that are typical in liquid metal blankets, together with available correlations for MHD pressure losses. This knowledge can provide simple design MHD guidelines that support a preliminary estimate of MHD effects in a blanket concept, in terms of pressure drop and flow distribution.

Benchmark of beam acceleration codes on a high voltage negative ion accelerator for fusion with a new hypothesis on the beam meniscus

It is a widely recognized phenomenon that, in negative ion sources for NBI, the magnetic fields in the source cause an asymmetry of the current density at the meniscus, which affects the beam optics. In order to achieve a more realistic estimation of the negative ion beam optics, the ion current density profile at the beamlet meniscus is sometimes assumed to be non-symmetric with respect to the beamlet axis. The new hypothesis tested in this paper is an empirical law obtained by recent investigations on a similar Kamaboko ion source, which relates this asymmetry to the magnetic field strength at the meniscus and to the power injected in the ion source. For the first time this hypothesis is used to directly and correctly predict the value of the beamlet deflection.The MeV ion source Test Facility (MTF) is a high voltage negative ion beam accelerator dedicated to fusion experiments in QST, Naka, Ibaraki, Japan. MTF can be operated as a three- or five-stage multi-aperture accelerator with a configuration and beam energy comparable to the future ITER NBI. In 2019, experiments were conducted on MTF aiming at accelerating a H- beam with high energy and good optics for a long duration of the beam (around 100 s). These experiments allowed to measure the beamlet divergence and deflection as well as the heat loads due to particle impinging on the accelerator grids, over a wide range of operating parameters. The predictions of several beam simulation codes (Opera, COMSOL, SLACCAD, EAMCC3D) have been compared to the experimental measurements, which allows to obtain a good agreement in terms of beam optics and a fair agreement in terms of heat loads.

Influence of a magnetic field on plasma energy transfer to material surfaces in edge-localized mode simulation experiments with QSPA-M

The features of plasma energy transfer to material surfaces during plasma–surface interactions (PSIs) in the presence of a strong magnetic field are investigated within the recently developed quasi-stationary plasma accelerator, QSPA-M. This novel PSI test-bed facility can reproduce edge localized mode (ELM) impacts, both in terms of heat load and particle flux to the surface, and provide plasma transportation in an external magnetic field, which mimics the divertor conditions. Investigations of energy transfer to the material surface have been performed for varied plasma heat load and external magnetic field values. Calorimetry, optical emission spectroscopy and high-speed imaging were applied for PSI characterization. For perpendicular plasma incidence, it has been shown that the transient plasma layer is formed in front of the surface by the stopped head of the plasma stream even for rather small plasma heat loads, which do not result in surface melting. The plasma density in this near-surface layer is much higher than in the impacting stream. It leads to the arisen screening effect for energy transfer to the surface. For B = 0, the thickness of the screening layer is less than 3 cm, but it increases to 15 cm when B = 0.8 T. The shielding effect due to the formation of a dense plasma layer in front of the exposed surface should be favorable for material performance, being important for decreasing the overall erosion of plasma-facing components during a large number of repetitive ELMs.

Production of 11C and 18F Isotopes. Getting the “Glucose, 11C “ Radiopharmaceutical

The results of the photonuclear production of 11C and 18F isotopes in various target-matrices are summarized. The studies were performed using linear electron accelerators of the R&DE "Accelerator" NSC KIPT NAS of Ukraine in the energy range 10 -40 MeV to determine the possibilities of obtaining the maximum achievable activity levels of 11C isotopes, and 18F with a view to planning further developments on the creation of radiopharmaceutical for these nuclear isotopes. In the framework of the above approach, we measured the activity levels of the 18F which is transferred to the surrounding aquatic environment during irradiation of targets-matrices of fluoroplastic (C2F4) with bremsstrahlung flux. The release of the 18F isotope into the aquatic environment under the most favorable conditions (in terms of energy and average beam current) was 3.6% of the target-matrices activity - 40 MBq/g, which is a very low figure. Despite the encouraging value of the specific activity of 18F isotope in lithium fluoride (LiF) -77 MBq/g target–matrices and hydrofluoric acid (HF) - close to 100 MBq/g, the process of extracting 18F from C2F4, LiF and HF as basis of the radiopharmaceutical is not sufficiently effective and brings into question the feasibility of such a methodology for producing 18F isotope for further use. More efficient was the production of the 11C isotope in the irradiated target-matrix of the standard therapeutic form "glucose monohydrate" (glucose). It was shown that, as a result of irradiation of glucose with a gamma-quanta beam, it is possible to “label” glucose with the 11C isotope, which is formed as a result of the photonuclear reaction 12C(γ, n)11C at the 12C nucleus, which is part of the glucose molecule C6H12O6 ×H2O. Irradiated sample of glucose dissolved in a given volume of solvent (distilled water) will be ready for use radiopharmaceutical "Glucose, 11C". It has been shown that the “photonuclear method” provides for obtaining the “Glucose, 11C” radiopharmaceutical complex with total activity necessary for performing PET diagnostics. The radiopharmaceutical "Glucose, 11C" by the time of its use has 100% radionuclide purity. “Glucose, 11C” obtained in this way was produced for the first time. The choice of the optimal design of a water-cooled target station, providing a moderate (in terms of heat loads) mode of irradiation of a capsule filled with glucose tablets, is discussed. Using the program “SolidWorks FlowSimulation 2011”, the quantitative characteristics of the flow rates of water flowing around the glucose capsule and the converter are calculated.

Novel test-bed facility for PSI issues in fusion reactor conditions on the base of next generation QSPA plasma accelerator

In this report a concept of a new generation QSPA with external B-field up to 2 T has been discussed. A novel test-bed facility, which was recently constructed in Kharkov IPP NSC KIPT, has been described. It allows for a new level of plasma stream parameters and its wide variation in new QSPA-M device, as well as possible combination of steady-state and pulsed plasma loads to the materials during the exposures. First plasma is recently obtained. Careful optimization of the operational regimes of the plasma accelerator’s functional components and plasma dynamics in the magnetic system of QSPA-M device has started approaching step by step the necessary level of plasma parameters and their effective variation. The relevant results on plasma stream characterization are presented. Energy density distributions in plasma stream have been measured with calorimetry. Spectroscopy and probe technique have also been applied for plasma parameters measurements. The obtained results demonstrate the ability of QSPA-M to reproduce the ELM impacts in fusion reactor, both in terms of heat load and particle flux to the surface.

Exergoeconomic optimization of an ammonia–water hybrid absorption–compression heat pump for heat supply in a spray-drying facility

Spray-drying facilities are among the most energy intensive industrial processes. Using a heat pump to recover waste heat and replace gas combustion has the potential to attain both economic and emissions savings. In the case examined a drying gas of ambient air is heated to 200 °C yielding a heat load of 6.1 MW. The exhaust air from the drying process is 80 °C. The implementation of an ammonia–water hybrid absorption–compression heat pump to partly cover the heat load is investigated. A thermodynamic analysis is applied to determine optimal circulation ratios for a number of ammonia mass fractions and heat pump loads. An exergoeconomic optimization is applied to minimize the lifetime cost of the system. Technological limitations are imposed to constrain the solution to commercial components. The best possible implementation is identified in terms of heat load, ammonia mass fraction and circulation ratio. The best possible implementation is a 895 kW heat pump with an ammonia mass fraction of 0.82 and a circulation ratio of 0.43. This results in economic savings with a present value of 146,000 € and a yearly CO2 emissions reduction of 227 ton.

A First Baseline for the Magnets in the High Luminosity LHC Insertion Regions

The High Luminosity LHC (HL-LHC) project aims at accumulating 3000 fb-1 in the years 2023-2035, i.e., ten times more w.r.t. the nominal LHC performance expected for 2010-2021. One key element to reach this challenging performance is a new insertion region to reduce the beam size in the interaction point by approximately a factor two. This requires larger aperture magnets in the region spanning from the interaction point to the matching section quadrupoles. This aperture has been fixed to 150 mm for the inner triplet quadrupoles in 2012. In this paper, we give a first baseline of the interaction region. We discuss the main motivations that lead us to choose the technology, the combination of fields/gradients and lengths, the apertures, the quantity of superconductor, and the operational margin. Key elements are also the constraints given by the energy deposition in terms of heat load and radiation damage; we present the main features related to shielding and heat removal.

Assessment of methods to reduce the energy consumption of food cold stores

Energy is a major cost in the operation of food cold stores. Work has shown that considerable energy savings can be achieved in cold stores. Results from 38 cold store audits carried out across Europe are presented.Substantial savings could be achieved if operation of cold storage facilities were optimised in terms of heat loads on the rooms and the operation of the refrigeration system. Many improvements identified were low in cost (improved door protection, defrost optimisation, control settings and repairs). In large stores (>100 m3) most improvements identified were cost effective and had short payback times, whereas in small stores there were fewer energy saving options that had realistic payback times. The potential for large energy savings of at minimum 8% and at maximum 72% were identified by optimising usage of stores, repairing current equipment and by retrofitting of energy efficient equipment. Often these improvements had short payback times of less than 1 year.In each facility the options to reduce energy consumption varied. This indicated that to fully identify the maximum energy savings, recommendations need to be specific to a particular plant. General recommendations cannot fully exploit the energy savings available and therefore to maximise energy savings it is essential to monitor and analyse data from each facility.

Applying Combined Pinch and Exergy Analysis to Closed-Cycle Gas Turbine System Design

Pinch technology has developed into a powerful tool for thermodynamic analysis of chemical processes and associated utilities, resulting in significant energy savings. Conventional pinch analysis identifies the most economical energy consumption in terms of heat loads and provides practical design guidelines to achieve this. However, in analyzing systems involving heat and power, for example, steam and gas turbines, etc., pure heat load analysis is insufficient. Exergy analysis, on the other hand, provides a tool for heat and power analysis, although at times it does not provide clear practical design guidelines. An appropriate combination of pinch and exergy analysis can provide practical methodology for the analysis of heat and power systems. The methodology has been successfully applied to refrigeration systems. This paper introduces the application of a combined pinch and exergy approach to commercial power plants with a demonstration example of a closed-cycle gas turbine (CCGT) system. Efficiency improvement of about 0.82 percent (50.2 to 51.02 percent) can be obtained by application of the new approach. More importantly, the approach can be used as an analysis and screening tool for the various design improvements and is generally applicable to any commercial power generation facility.

Variable conductance heat pipes - A first-order model

The variable-conductance heat pipe (VCHP) is modeled as a one-dimensional fin with a discrete heated zone between unknown axial locations /t and -/0. The length /t is constrained by the distribution of noncondensable gas throughout the length of the pipe and in a temperature-controlled, wicked reservoir; the length -/0 must be determined empirically. Internal heat and mass transfer processes are subsumed by postulating that condensation imposes a specified local heat flux in the heated zone only. An analytically tractable heat flux distribution is assumed by introducing a parameter s that must be determined either empirically or intuitively. The heat pipe operates in a steady state and loses energy either by convection or linearized radiation, with different values of heat loss coefficient in the active and inactive condenser zones. A closed-form solution for axial temperature is found in terms of heat load, reservoir temperature, environmental conditions, wick/wall thermal conductance, the two parameters ( —/0,s), and the condensation front location lv An algebraic expression for the condensation front is obtained from the noncondensable gas inventory; the mass distribution integral is decomposed into zonal integrals and each integral is evaluated by a mean value approximation based on mean zonal temperature. The temperature and condensation front equations must be solved simultaneously to predict VCHP performance. Data of Edwards and Marcus are used to evaluate the empirical constants (-/0,s). An example is included to illustrate how the formulation may be used to predict diffusion freezeout and specify the gas reservoir volume.