Helium Mass Flow Rate Research Articles

A thermodynamic comparison between organic Rankine and Kalina cycles for waste heat recovery from the Gas Turbine-Modular Helium Reactor

A comparative thermodynamic analysis and optimization is presented for waste heat recovery from the Gas Turbine-Modular Helium Reactor (GT-MHR) employing organic Rankine cycle (ORC) and Kalina cycle (KC). Thermodynamic models are developed for the stand alone GT-MHR and the two proposed combined cycles and the effects on the performances of the cycles are investigated of decision variables. The cycles' performances are then optimized based on the first and second law of thermodynamics. The results showed that, employing ORC is more appropriate than KC for GT-MHR waste heat recovery. The first and second law efficiencies of the combined GT-MHR/ORC are higher than those of the combined GT-MHR/KC. In addition, the helium mass flow rate in the combined GT-MHR/ORC is significantly lower than that in the combined GT-MHR/KC. Moreover, the high-pressure level of the ORC is extremely lower than that of the KC under optimized conditions. Furthermore, the superheated vapor at the ORC turbine exit avoids droplet erosion and allows for reliable operation while the stream exiting the KC turbine is a two-phase flow.

Quench Detection of SST-1 TF Coils by Helium Flow and Pressure Measurement

Superconducting magnets of Steady-state Superconducting Tokamak-1 (SST-1) are cooled by Supercritical helium at 4.5 K and 0.4 MPa. Two types of Venturi meters (VM) are being used for measuring helium mass flow rates in these magnets. Signal conditioning for temperature, absolute pressure and differential pressure sensors and a suitable data acquisition system has also been developed for these flow meters. These flow meters were extensively qualified during individual coil test campaigns of SST-1 TF coils. Mass flow and pressure signal behavior during quench events of TF coil tests were analyzed and a quench detection system using these signals has been proposed for TF coils. This secondary quench detection methodology and its hardware development are discussed in this paper. This paper also describes the VM design, fabrication, installation and the flow measurement system.

Influence of oxygen gas on characteristics of self-organized luminous pattern formation observed in an atmospheric dc glow discharge using a liquid electrode

Self-organized luminous pattern formation is observed in the liquid surface of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. The factors affecting pattern formation are the gap length, discharge current, helium mass flow rate and polarity. The pattern shape depends on the conductivity and temperature of the liquid electrode. A variety of patterns were observed by changing the conductivity and temperature of the liquid. We clarified that the self-organized pattern formation depends on the amount of electronegative gas, such as oxygen, in the gas in the electrode gap. When an oxygen gas flow was fed to the liquid surface from the outside in an obliquely downward direction, namely, the amount of oxygen gas on the liquid surface was increased locally, self-organized pattern formation was observed in the region with the increased amount of oxygen gas. When the amount of oxygen in the gas in the gap was changed by using a sheath flow system, the appearance of the pattern changed. The presence of oxygen gas strongly affected the self-organized pattern formation of the atmospheric dc discharge using a liquid anode.

He flow rate measurements on the engineering model for the Astro-H Soft X-ray Spectrometer dewar

The sixth X-ray Japanese astronomy satellite, namely Astro-H, will be launched in 2015. The Soft X-ray Spectrometer onboard the Astro-H is a 6×6 X-ray microcalorimeter array and provides us with both a high energy resolution of <7eV at 0.5–10keV and a 3′×3′ modest imaging capability for the first time. To cool the detector down to the operation temperature of 50mK, five cryocoolers, a 30-L superfluid helium cryostat, and a 3-stage adiabatic demagnetization refrigerator are utilized. A very small heat load up to ∼0.9mW on the helium tank is allowable to realize the helium lifetime of >3years, which consequently requires that the vapor flow rate out of the helium tank should be very small <42μg/s. We adopted a porous plug phase separator in combination with a film flow suppression system composed of an orifice, a heat exchanger and knife edge devices to retain the liquid helium under zero gravity and safely vent the small amount of the helium vapor. We measured helium mass flow rates from the helium tank equipped in the engineering model dewar. We tilted the dewar at an angle of 75° so that one side of the porous plug located at the top of the helium tank attaches the liquid helium and the porous plug separates the liquid and vapor helium by thermomechanical effect. Helium mass flow rates were measured at helium tank temperatures of 1.3, 1.5 and 1.9K. We confirmed that resultant mass flow rates are in good agreement within the systematic error or low compared to component test results and achieve all the requirements. The film flow suppression also worked normally. Therefore, we concluded that the SXS helium vent system satisfactorily performs integrated into the dewar.

Thermal hydraulic performance testing of printed circuit heat exchangers in a high-temperature helium test facility

In high-temperature gas-cooled reactors, such as a very high temperature reactor (VHTR), an intermediate heat exchanger (IHX) is required to efficiently transfer the core thermal output to a secondary fluid for electricity generation with an indirect power cycle and/or process heat applications. Currently, there is no proven high-temperature (750–800 °C or higher) compact heat exchanger technology for high-temperature reactor design concepts. In this study, printed circuit heat exchanger (PCHE), a potential IHX concept for high-temperature applications, has been investigated for their heat transfer and pressure drop characteristics under high operating temperatures and pressures.Two PCHEs, each having 10 hot and 10 cold plates with 12 channels (semicircular cross-section) in each plate are fabricated using Alloy 617 plates and tested for their performance in a high-temperature helium test facility (HTHF). The PCHE inlet temperature and pressure were varied from 85 to 390 °C/1.0–2.7 MPa for the cold side and 208–790 °C/1.0–2.7 MPa for the hot side, respectively, while the mass flow rate of helium was varied from 15 to 49 kg/h. This range of mass flow rates corresponds to PCHE channel Reynolds numbers of 950 to 4100 for the cold side and 900 to 3900 for the hot side (corresponding to the laminar and laminar-to-turbulent transition flow regimes). The obtained experimental data have been analyzed for the pressure drop and heat transfer characteristics of the heat transfer surface of the PCHEs and compared with the available models and correlations in the literature. In addition, a numerical treatment of hydrodynamically developing and hydrodynamically fully-developed laminar flow through a semicircular duct is presented. Relations developed for determining the hydrodynamic entrance length in a semicircular duct and the friction factor (or pressure drop) in the hydrodynamic entry length region for laminar flow through a semicircular duct are given. Various hydrodynamic entrance region parameters, such as incremental pressure drop number, apparent Fanning friction factor, and hydrodynamic entrance length in a semicircular duct have been numerically estimated.

Experimental investigation of two-stage active magnetic regenerative refrigerator operating between 77 K and 20 K

This paper presents an experimental investigation on a magnetic refrigerator operating between 77K and 20K. Since the magneto-caloric effect of typical magnetic refrigerant is concentrated in a narrow temperature region, four different rare-earth intermetallic compounds (GdNi2, Dy0.85Er0.15Al2, Dy0.5Dr0.5Al2, and Gd0.1Dy0.9Ni2) are utilized according to their favorable temperature regions. The magnetic refrigerator is composed of two stages each of that is made of two different porous active magnetic regenerators. Helium gas as the heat transfer medium in the magnetic refrigerator is shuttled similar to a GM type pulse tube refrigerator so that the overall cooling capacity is enhanced by gas expansion effect when both gas and magnetic expansions are properly coordinated. The approximate peak magnetic field of 4T is provided for the internal region of the regenerators by the AC superconducting magnet which can fast ramp up to the maximum field for 3s. The fabricated magnetic refrigerator reached the lowest no-load temperature of 24K and the whole temperature span was approximately 56K rather than 57K. The cooling performance of the system is sensitive according to the load match between the first and the second stages in conjunction with helium mass flow rate distribution.

New solutions to produce a cryogenic void fraction sensor of round cross-section and its applications

A new variant of the void fraction RF-sensor of the round cross-section with ID=38mm is presented. Its sensitive part is made of the ceramic pipe with a meander line on the outer surface. This technique does not disturb the flow moving in the metal pipe of the same diameter. The technical solutions to provide rather high uniformity of the electric field within the sensitive volume and excellent stability of the readings are described. Irregular steps of the meander line are chosen after computer calculations and experimental checking. Some disadvantages of the previous modifications are shown as well. A new calibration procedure is discussed: it takes into account the dependence of the resonant frequency of the empty RF-sensor on the temperature of the sensor body. The method to find a mass flow rate of the two-phase helium and hydrogen flows in the range of void fractions from 0% to 100% is demonstrated with the new RF-sensor.

Three dimensional CFD analysis of Cable-in-Conduit Conductors (CICCs) using porous medium approach

Thermohydraulic studies based on porous medium analogy, pertinent to dual channel Cable-in-Conduit Conductors (CICCs) used in International Thermonuclear Experimental Reactor (ITER), are explored in the present work. Dual channel CICC used in Toroidal Field (TF) Coil consists of a circular jacket in which superconducting cable bundles are placed in the annular channel separated from the central channel by a spiral. The cable bundle in the annular channel can be considered as saturated porous medium and the central channel can be viewed as clear region for thermohydraulic studies. In the present work, a 3D Computational Fluid Dynamics (CFD) analysis is performed on CICC by considering dual channel CICC as partially filled saturated porous medium. The 3D geometry was developed and meshed in GAMBIT-2.1.6, and exported to a commercial solver FLUENT -6.3.26 for further analysis. The effect of mass flow rate ( 6 - 10 g/s) of supercritical helium (SHe) on the velocity and pressure gradient distributions (axial and radial) in the transverse plane is presented. These studies resulted in estimating the mass flow repartition between the two channels and pumping power required to pump the SHe in CICC. In addition, the present CFD analysis brings a clear perspective of the phenomena of flow and heat transfer in complex geometries such as CICC.

CFD Analysis of Cable-In-Conduit Conductors (CICC) for Fusion Grade Magnets

In the present work, dual channel Cable-in-Conduit Conductor (CICC) is considered for Computational Fluid Dynamics (CFD) analysis to understand the complex behavior of flow. A two dimensional (2D) axisymmetric computational model mimicking the CICC is generated and meshed in GAMBIT 2.0. The meshed model is exported to FLUENT 6.3, a commercial CFD code, for further analysis. Annular bundle channel of CICC is assumed to be porous medium with porosity of 0.37 and the central channel is assumed as clear region. The effects of variations in mass flow rate (6 g/s to 10 g/s) of Supercritical helium (SHe), which is used as coolant, through CICC on the pressure gradients and velocity gradients are studied. Reynolds Averaged Navier Stokes (RANS) model is considered for the analysis with standard k-epsilon (k - e)turbulence, which is relevant to the separated flow models. Axial and Radial pressure gradients are calculated along the CICC axis and along the centre line of bundle channel. Friction factor is calculated using the shear stresses obtained from CFD analysis.

Test Results of Three Poloidal Field Superconducting Samples in SULTAN

Superconductors for the ITER Poloidal Field Coils are large cable-in-conduit conductors (CICC) made of NbTi strands encased in a round-in-square stainless steel jacket. Three prototype conductor sections for poloidal field coils PF1/6, PF2/3/4 and PF5 have been fabricated in collaboration of the domestic RF, CN and EU agencies and tested in SULTAN Test Facility at the nominal operating conditions. The test aimed to characterize the DC and AC behavior of the conductors. The DC test was focused on the current sharing temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cs</sub> ) at the nominal operating current and nominal operating background field. The take-off electric field at the nominal Helium mass flow rate was investigated versus the cable current density over a broad range of field and temperature. The AC loss measurement was performed before any electromagnetic loading and after a number of load cycles in order to define the impact of cyclic loads on the coupling currents constant of the cable. From the test results in SULTAN test facility, the margins in normal operation and the limits of the operation range of the ITER PF conductors are assessed.

Hydraulic Behaviors of KSTAR PF Coils in Operation

The superconducting coil system is one of the most important components in Korea Superconducting Tokamak Advanced Research (KSTAR), which has been operated since 2008. <TEX>$Nb_3Sn$</TEX> and NbTi superconductors are being used for cable-in-conduit conductors (CICCs) of the KSTAR toroidal field (TF) and poloidal field (PF) coils. The CICCs are cooled by forced-flow supercritical helium about 4.5 K. The temperature, pressure and mass flow rate of the supercritical helium in the CICCs are interacting with each other during the operation of the coils. The complicate behaviors of the supercritical helium have an effect on the operation and the efficiency of the helium refrigeration system (HRS) by means of, for instance, pressure drop. The hydraulic characteristics of the supercritical helium have been monitored while the TF coils have stably achieved the full current of 35 kA. In other hands, the PF coils have been operated with various pulsed or bipolar mode, so the drastic changes happen in view of hydraulics. The heat load including AC loss on the coils has been analyzed according to the measurement. These activities are important to estimate the temperature margin in various PF operation conditions. In this paper, the latest hydraulic behaviors of PF coils during KSTAR operation are presented.

Design and Manufacture of 20 kA HTS Current Leads for a Hybrid Magnet System

A new series connected 25 T hybrid magnet system is being developed by the Helmholtz Zentrum Berlin (HZB) for neutron scattering experiments. In collaboration with CRPP, high temperature superconducting (HTS) current leads have been developed for the powering of the outer superconducting coil. These HTS current leads, with a nominal current rating of 20 kA, have been designed and are being manufactured by CRPP, based on the design of the 18 kA EDIPO leads. Each of the two current leads consists of an HTS module cooled only by heat conduction from the cold end and a copper part actively cooled by helium gas of 44 K inlet temperature. To reach a temperature of 53.7 K at the warm end of the HTS a helium mass flow rate of 1.37 g/s per lead is required at a current of 20 kA. The estimated heat leak at the 4.5 K level caused only by heat conduction is as low as 1.4 W. The evolution of the temperatures in the case of a loss of flow has been calculated. In addition to the design, the main fabrication steps are described. (C) 2012 Published by Elsevier B. V. Selection and/or peer-review under responsibility of the Guest Editors.

Two-phase cryogenic flow meters: Part II – How to realize the two-phase pressure drop method

The pressure drop method to find the mass flow rate of the two-phase helium and hydrogen flows is discussed in this paper. This method is based on a combination of the narrowing device and the RF void fraction sensor described earlier. Advantages of this approach with respect to the calorimetric one are demonstrated and its metrological characteristics for different flow patterns are estimated. The discussed cryogenic technologies and methods may be used for others applications, for example, to solve some tasks in oil-producing industry.

Test results of the 18 kA EDIPO HTS current leads

For the new test facility EDIPO (European DIPOle), to be hosted by CRPP, two 18 kA HTS current leads were manufactured and successfully tested. The HTS module, made of AgMgAu/Bi-2223 tapes, is cooled only by heat conduction to the cold end, while the copper part is cooled by forced flow helium gas. The current leads were tested at low voltage up to the maximum current of 18 kA. The helium mass flow rates required for stable operation at various currents were determined. In addition to the steady state operation, the transient behavior in the case of a loss of flow was studied experimentally. The test results provide an estimate of the operational limits of the EDIPO HTS current leads.

Experimental study of detonation in a cryogenic two-phase H 2–O 2 flow

Direct initiation and propagation of detonation through a cryogenic two-phase flow constituted by liquid oxygen droplets in gaseous hydrogen at 100 K are experimentally investigated. The influence of droplet size distribution is characterized in a cryogenic gaseous helium and liquid oxygen two-phase flow. Droplet sizing and detonation experiments are conducted by varying different parameters: distance from the injector, helium and hydrogen mass flow rates, global equivalence ratio and addition of gaseous nitrogen. Droplet size distributions reveal quick vaporization of the smallest droplets of the cryogenic jet. Results in terms of wave velocity, pressure, and detonation cells show that a detonation wave can be directly initiated, with a propagation wave velocity of 20% higher than the Chapman–Jouguet value. Cell size measurements show that the mixture sensitivity is not affected by the presence of droplets. Addition of gaseous nitrogen reduces only slightly the peak pressure, but the detonation velocity is reduced by about 30%.

A Si/Glass Bulk-Micromachined Cryogenic Heat Exchanger for High Heat Loads: Fabrication, Test, and Application Results

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a 1 x 1-cm(2) footprint and a length of up to 3.5 cm. It is intended for use in Joule-Thomson (J-T) coolers and can sustain pressure exceeding 1 MPa. Tests at cold-end inlet temperatures of 237 K-252 K show that the heat exchanger effectiveness is 0.9 with 0.039-g/s helium mass flow rate. The integrated Pt RTDs present a linear response of 0.26%-0.30%/K over an operational range of 205 K-296 K but remain usable at lower temperatures. In self-cooling tests with ethane as the working fluid, a J-T system with the heat exchanger drops 76.1 K below the inlet temperature, achieving 218.7 K for a pressure of 835.8 kPa. The system reaches 200 K in transient state; further cooling is limited by impurities that freeze within the flow stream. In J-T self-cooling tests with an external heat load, the system reaches 239 K while providing 1 W of cooling. In all cases, there is an additional parasitic heat load estimated at 300-500 mW.

A carbon dioxide thermal rocket that utilizes an indigenous resource in raw form for Mars exploration

A CO2 thermal rocket that utilizes an indigenous resource directly for propulsion in Mars is proposed. The cycle of the proposed novel CO2 thermal rocket combines a CO2 power cycle with a cryogenic cycle, which is driven by solar energy. Filling CO2 after every hop enables the concept hopper with the CO2 thermal rocket to visit several regions of the planet. The energy available for consumption in the processes of the proposed CO2 thermal rocket is analysed; the simulation results obtained by applying the first law of thermodynamics show that the performance of the cycle of the CO2 thermal rocket is improved by properly designing such a system for the recovery of freezing CO2 cold energy and waste heat during the cryogenic cycle. Furthermore, the effect of thermodynamic parameters on the performance of the cycle of the CO2 thermal rocket is evaluated through parametric analysis; the results show that environmental temperature, nozzle inlet temperature, helium mass flowrate, etc. are the factors affecting thrust-specific power consumption.

2D thermal analysis for heat transfer from casing to winding pack in JT-60SA TF coils

In the framework of the Broader Approach Agreement, Europe is involved in the design activities for the Japanese Tokamak JT-60SA, investigating, among several issues, the operation of the superconducting TF magnets and their subsystems, aimed at the reactor conceptual design definition. In particular, one of the main critical aspects to study is the heating of the conductor due to both direct component of energy deposited by neutrons and by secondary gamma generated during plasma operation, and heat generated by the radiation on casing and transferred to the winding pack. Indeed, the operating temperature and the relevant temperature margin (i.e. the operating safety margin) of the magnet will depend strongly on the heat loads and on the capability of the coolant to remove it. Furthermore, the heat power to the conductor will depend on several aspects, namely the thickness of insulating material, the mass flow rate of helium flowing in the conductors and its thermodynamic properties at operating conditions, and the layout of the superconductors constituting the winding. Moreover, a crucial aspect in the final design will be the presence and position of the casing cooling channels. In this paper a 2D sensitivity analysis of heat transfer from casing to winding pack with respect to cooling channels number and position is presented, based on the reference layout of the magnet. As a result, we evaluated the optimum number and positioning of cooling channels needed, as a trade-off between magnet operating limits and available cryogenic power and if, at limit, they could be even neglected in normal operation, keeping dwell-time within reasonable values.

Energy deposition via magnetoplasmadynamic acceleration: I. Experiment

The expansion of a high-temperature fusion plasma through an expanding magnetic field is a process common to most fusion propulsion concepts. The propulsive efficiency of this process has a strong bearing on the overall performance of fusion propulsion. In order to simulate the expansion of a fusion plasma, a concept has been developed in which a high velocity plasma is first stagnated in a converging magnetic field to high (100s of eV) temperatures, then expanded though a converging/diverging magnetic nozzle. As a first step in constructing this experiment, a gigawatt magnetoplasmadynamic plasma accelerator was constructed to generate the initial high velocity plasma and has been characterized. The source is powered by a 1.6 MJ, 1.6 ms pulse forming network. The device has been operated with currents up to 300 kA and power levels up to 200 MWe. These values are among the highest levels reached in an magnetoplasmadynamic thruster. The device operation has been characterized by quasi-steady voltage and current measurements for helium mass flow rates from 0.5 to 27 g s−1. Probe results for downstream plasma density and electron temperature are also presented. The source behavior is examined in terms of current theories for magnetoplasmadynamic thrusters.

Study on cooling process of cryogenic system for superconducting magnets of BEPCII**Supported by the Project of BEPCII

In the upgrade project of the Beijing Electron Positron Collider (BEPCII), three superconducting magnets are employed to realize the goal of two orders of magnitude higher luminosity. A cryogenic system with a total capacity of 0.5 kW at 4.5 K was built at the Institute of High Energy Physics (IHEP) to support the operations of these superconducting devices. For preparing the commissioning of the system, the refrigeration process was simulated and analyzed numerically. The numerical model was based on the latest engineering progress and focused on the normal operation mode. The pressure and temperature profiles of the cryogenic system are achieved with the simulation. The influence of the helium mass flow rates to cool superconducting magnets on the thermodynamic parameters of their normal operation is also studied and discussed in this paper.