Hot Source Research Articles

A High-Throughput Hot Surface Ion Source for Electromagnetic Radioisotope Separation

An available supply of high-specific-activity radioisotopes was identified by the U.S. Department of Energy as a critical priority to the development and eventual deployment of next-generation medical diagnostic and cancer therapy tools. Work at the University of Missouri Research Reactor Center has been undertaken to develop an electromagnetic isotope separation technique that will leverage the production capabilities of the 10-MW reactor to provide radiolanthanides in quantities suitable for use in preclinical trials. A high-throughput concept design based on a solid tantalum hot surface ion source and an insertable titanium crucible will be described. Significant aspects of the electrical and thermal design of the ion source will be presented. Novel heating and cooling strategies were employed to concentrate heating where it is most needed while attempting to reduce thermal stress where heating is not required. Thermal testing from the commissioning process will be presented to demonstrate the temperature at several key locations in and around the ion source.

Reactive cooling simulation of electronic components

Low-grade heat recovery is an indispensable solution towards high energy efficiency of power electronics. The fast pace of sustainable digitalisation calls for developing alternative solutions to create a sustainable loop for decreasing the energy footprint. However, heat transfer under low-temperature differences challenges effective heat recovery processes. Therefore, in this paper, reactive fluid performance in a practical heat exchanger is investigated using high-fidelity finite rate chemistry method, which is a key step to deploy the attractive Ericsson cycle for low-temperature heat-to-electricity conversion. Under fixed thermal efficiency, it is found that replacing non-reactive fluid by N2O4 reactive fluid can immediately boost electrical efficiency of an Ericsson cycle by at least 260%. The needed primary heat exchanger component in an integrated cooling and power electronic system can be 54.8% smaller in volume whilst enabling a 26% higher thermal performance, provided that the hot source temperature is low (<403 K). For thermal processes involving high temperature hot source, substantial limitation of chemical reaction rate on the effectiveness of an Ericsson cycle is identified. Remarkably, low temperature difference is not a limitation for reactive heat transfer that continuous endo-/exothermic reaction happening throughout a heat exchanger improves Nusselt number Nu = 7.5 by a factor of ∼ 1.3 than the corresponding value (Nu = 5.9) for non-reactive fluid. Turbulence is found beneficial for reactive heat transfer, suggesting the use of corrugated-type heat exchangers for better thermal exchange rates.

Nonlinear models for coupling the effects of stimulated Raman scattering to inertial confinement fusion codes

Laser plasma instabilities (LPI) reduce driver-target coupling, alter implosion symmetry, and therefore can fundamentally limit fusion performance in inertial confinement fusion (ICF). Developing a predictive modeling capability for LPI effects can critically advance the success of the field. We perform vector particle-in-cell simulations of multi-speckled laser beams undergoing stimulated Raman scattering (SRS) at various densities and intensities relevant to mainly indirectly driven and a subset of parameter space for directly driven ICF systems, focusing on the regimes with intensities above the onset of electron trapping. Based on the wavenumber of the SRS daughter electron plasma wave, we identify several regions with underpinning SRS saturation physics: the electron-trapping dominated region with intermediate kλD values, the strong Landau damping region at larger kλD values, and the region where the Langmuir decay instability arises at lower kλD values. We develop a nonlinear SRS reflectivity model that features the base trapping-dominated scaling of (kλD)−4 and its modifications. Electron trapping deforms the initialized electron distribution functions, and we have developed a new δf-Gaussian-mixture algorithm for an accurate characterization of the trapped hot electron population. With this SRS hot electron description, we construct a nonlinear energy deposition model and a hot electron source model—based on a modified Manley–Rowe relation—suitable for including SRS effects as a sub-grid module in a high-fidelity ICF design code.

IMPROVEMENT OF THE SECURITY SYSTEM AGAINST POLLUTANTS USING A CIRCULAR CONE

This study focuses on the improvement of a security system against the pollutants dispersing from Industrial chimneys. In order to simulate the system, we study numerically a turbulent flow generated by a heated open cone at the extremities. Different control parameters were used to improve the thermal and dynamic behavior of the considered flow. In this study, the interaction of pollutants with its surrounding environment simulated by the cone walls was investigated. This study was focused on convection, which is natural, turbulent, steady, 2-D, incompressible flow passing through a vertical conical channel with a heated source at the center of the cone inlet that performed uniform heating at a constant temperature. The interior of the conical wall channel was reheated via the thermal radiation emitted by the hot source. The studied system was mathematically presented by the continuity, Navier stokes, energy and K-epsilon equations. The computational fluid dynamics analysisand ANSYS-FLUENT software were used. The optimal cone can provide further control of the pollutants velocity at the exit. The thermal and dynamic profiles exhibitedgood stability and homogeneity at the cone exit.

A newly constructed Linear Experimental Advanced Device LEAD

The Linear Experimental Advanced Device (LEAD) has been constructed for comprehensive studies on plasma turbulence, plasma-material interaction and new techniques for tokamaks at Southwestern Institute of Physics (SWIP). The vacuum vessel of this linear device is 3055 mm long. It consists of three parts, i.e. the source chamber, the linear magnetized confinement chamber and the plasma-material interaction (PMI) chamber. Kinds of plasma sources, including radio-frequency (RF) sources and a hot cathode source, have been developed to produce steady-state plasma. Wave-mode helicon plasmas can be excited by a large-size four-ring-antenna RF source when the input power is higher than 180 W. The typical electron density is higher than 1019/m3. Transfer from distinct narrowband drift waves to broadband turbulence is observed by means of adjusting the axial magnetic field, which makes LEAD a suitable device to investigate plasma turbulence. Auxiliary heating systems, including a 2.45 GHz Electron Cyclotron Resonance and an ion heating source, and a 1.5 MV ion accelerator are to be installed on LEAD. It promises a particle flow of over 1023/m2s and a heat load of several MW/m2, which makes LEAD a suitable platform for not only fundamental plasma physics but also PMI research.

The evaluation of the first and second laws of thermodynamics for the pulsating MHD nanofluid flow using CFD and machine learning approach

Background: By developing high-tech instruments, especially digital devices, a need to have efficient and compact cooling is of crucial importance. In the current study, heat transfer enhancement in a microchannel for cooling two hot sources is numerically investigated. Methods: The effects of imposing a magnetic field, a pulsating flow, and using a hybrid nanofluid are tested. Further, the entropy generation is evaluated and the strength of irreversibility sources is discussed. Reynolds number, Hartmann number, nanofluid volume fraction, inlet velocity amplitude, and frequency are chosen as the independent parameters. An artificial neural network is applied to have a prediction tool for the mean Nusselt number and Bejan number. The analysis for choosing the best neuron number for MLP is conducted. The predictive mathematical description is fed to a multi-objective genetic algorithm (NSGA-II) to find the optimum operating conditions of thermal cooling. Significant findings: The results show that Intensifying the inlet amplitude from 0.1 to 0.8 makes the heat transfer and pressure drop increment respectively by 100% and 300%. However, the amplitude increment remains an inverse effect on the Bejan number by a decrement of about 3–4%. The sensitivity analysis shows the first rank of importance belongs to the Reynolds number the Hartmann number shows the least importance in the ranking.

Geochemical signature of a deeply subducted slab in the source of post-collisional magmatism: A case study from the Western Tianshan NW China

The contributions of deeply subducted slabs to post-collisional magmatism are poorly constrained. Here, we present a study of the post-collisional, Early Permian (ca. 279 Ma), Hamisite basalts from the Western Tianshan NW China to trace the geochemical fingerprints of deeply subducted slab. The Hamisite basalts have arc-like trace element patterns but high Nb/Ta ratios (18.4−23.0). They have slightly enriched Sr−Nd isotopic compositions (87Sr/86Sr = 0.7048−0.7052; εNd[t] = 2.02−3.85), which indicates that the basalts were derived from an enriched mantle source. Extremely low δ7Li values (−5.76‰ to 0.20‰) imply the involvement of a deeply subducted slab (i.e., eclogites) in the source. Correlations among Nb/Ta and (Dy/Yb)N ratios, and rare earth element contents, indicate that the deeply subducted slab contained residual rutile and garnet but no epidote. Given that melting of eclogites requires an anomalously hot mantle source, we propose that mantle upwelling during post-collisional extension triggered melting of the deeply subducted slab. Our results indicate that melting of a deeply subducted slab can generate a metasomatized mantle source with high Nb/Ta ratios, which could be a hidden, high-Nb/Ta reservoir on Earth. Low δ7Li values and high Nb/Ta ratios could be a fingerprint of recycling of a deeply subducted slab.

Mixed Convection in a Horizontal Channel–Cavity Arrangement with Different Heat Source Locations

Several researchers are very interested in mixed convection heat transfer because of how widely it is used, particularly for solar thermal collectors, cooling electronic equipment, and chemical process instruments. Using COMSOL-Multiphysics, this article establishes laminar coupled mixed convection heat transfer characteristics across a horizontal channel–cavity architecture. Investigations are conducted into the effect of heat source location on isotherms, velocity distribution, pressure, temperature, average and local Nusselt numbers, and air density. The intake airflow Reynolds number is assumed constant on 2.8814. The enclosure with an isothermally heated right wall in the shape of a “&lt;” as a heat source in three configurations (heat source in the base (1st case), in the upper step (2nd case), and the below step (3rd case). The obtained numerical results present that the higher heat transfer is performed in case two because the heat source is near the contact surface between the channel and the cavity. With the hot sources’ locations being altered, the velocity distribution seems to be unchanged. The increase in the positive y axis has no impact on the pressure distribution throughout the channel. Changing the position of the heated source does not seem to have any impact on the pressure distribution. Air density profiles start to diverge across cases around y = 0.035 m; the third example has a larger value than the second case, and the latter case has a larger value in the density distribution than the former. The contact between the enclosure and the channel (y = 0), where the greatest Nusselt number also occurs, exhibits the highest heat transfer. The maximal Nusselt number falls as y’s absolute value rises.

Lower crustal hot zones as zircon incubators: Inherited zircon antecryts in diorites from a mafic mush reservoir

Abstract Continental arcs are key sites of granitic magmatism, yet details of the origins of these magmas, including the role and contribution of mafic magma, the timing and location of initial zircon formation and how zircon isotopic signatures relate to granite formation, remain as challenges. Here we use U–Pb dating, trace elements and Hf isotopic systematics of zircon in mafic microgranular enclaves (MMEs), from the convergent plate margin Satkatbong diorite (SKD) in Korea to understand lower arc magmatism and zircon production. The host granitic body and MMEs display similar major element evolutionary trends and similar ranges of Sr, Nd and Hf isotopes, implying a cognatic relationship. Zircons show a large variability in ε Hf ( t ) ( c. 6 units) and age (&gt;30 Ma). We propose that the SKD and MMEs originated from the same, long-lasting, lower crustal mush reservoir, enabling long and variable residence times for zircons. Prolonged zircon ages, combined with the Hf isotope variability within a single pluton (SKD and its MME), indicate that not all zircons were instantaneously crystallized in a rapidly cooling shallow magma chamber but were continuously formed in a long-lasting hot source. A low-melt-fraction mush type reservoir in a deep crustal hot zone provides a viable model for the source setting. Continuous replenishment of mafic magmas acts as the main re-activator of the reservoir, and provide a critical role in spawning zircons that record a long age span, because (1) the magma adds Zr into the reservoir, enabling it to reach zircon saturation and (2) the generated zircon grains are transported upward as antecrysts by flow inside of the reservoir. This means that antecrysts with different ages may mix with each other in the ascending magma body. The significance of this model is that a conclusive time of intrusion cannot be constrained by such zircon ages, as these antecrysts constitute inherited grains.

Isothermal thermodynamic analysis investigation of the Stirling engine types (alpha, beta, gamma): A theatrical study

Stirling engine is type of external combustion engines, closed and cyclic that operates on the Stirling cycle. This paper presents a theatrical thermodynamic investigation to compare between Stirling engine major types (alpha, beta, gamma) with ideal isothermal model based on Schmidt analysis, air as the working fluid was tested. The impact of hot source temperature and cold sink temperature, engine speed and mass of working fluid were also considered. The results shows that gamma engine is more efficient than other types with output power 197.8 W while beta with 195 W and alpha with 140 W based on modeling data in this study.

Crack formation of camshaft castings: Hot tearing susceptibility and root causes

As a widely used cyclical motion component, the camshaft plays a key role in the accuracy and stability of the whole machine. Micro hot cracks in the camshaft casting process are an important cause of failure in subsequent machining and operation. In this paper, the hot tearing susceptibility of the camshaft in the casting process was studied using the alloy composition (carbon equivalent and Mn/S ratio) and mold preheating temperature. The formation mechanism of the hot tear source was analyzed through the microscopic morphology of the fracture-sensitive cross-section. Using the improved Clyne-Davies model and the newly proposed hot tearing susceptibility (HTS) model, the results show that as the carbon equivalent and Mn/S ratio increase, the hot tearing susceptibility of the camshaft first decreases and then increases. The hot tearing tendency of the casting can be reduced by appropriately increasing the mold preheating temperature. The microscopic morphology indicates that the initiation and propagation of the crack source are caused by the excessively serious non-equilibrium solidification of the camshaft metal fluid. Finally, potential countermeasures are proposed to decrease micro hot cracks in camshaft castings, including the adjustment of alloy composition, optimization of casting process parameters, and improvement of system solidification conditions.

Natural convection of NEPCM in a partial porous H-shaped cavity: ISPH simulation

PurposeThis paper aims to investigate the conformable fractal approaches of unsteady natural convection in a partial layer porous H-shaped cavity suspended by nano-encapsulated phase change material (NEPCM) by the incompressible smoothed particle hydrodynamics method.Design/methodology/approachThe partial hot sources with variable height L_Hot are in the H-cavity’s sides and center. The performed numerical simulations are obtained at the variations of the following parameters: source of hot length L_Hot = (0.4–1.6), conformable fractal parameterα(0.97–1), fusion temperatureθf(0.05–0.9), thermal radiation parameterRd(0–7), Rayleigh numberRa(103–106), Darcy parameterDa(10−2to 10−5) and Hartmann numberHa(0–80).FindingsThe main outcomes showed the implication of hot source length L_Hot, Rayleigh number and fusion temperature in controlling the contours of a heat capacity within H-shaped cavity. The presence of a porous layer in the right zone of H-shaped cavity prevents the nanofluid flow within this area at lower Darcy parameter. An increment in the thermal radiation parameter declines the heat transfer and changes the heat capacity contours within H-shaped cavity. The velocity field is strongly enhanced by an augmentation on Rayleigh number. Increasing the Hartmann number shrinks the velocity field within H-shaped cavity.Originality/valueThe novelty of this work is solving the conformable fractal approaches of unsteady natural convection in a partial layer porous H-shaped cavity suspended by NEPCM.

New horizons in magnetic refrigeration using artificial intelligence

A number of magnetic refrigeration prototypes have been developed in recent years. Nevertheless, their optimization remains a challenging process. This paper presents an efficient approach based on artificial intelligence for optimizing the cooling performance of multi-layer active magnetic regenerators. To this end, a validated numerical model was used to predict the temperature difference between the hot and cold sources of a four-layer active magnetic regenerator. By using a nanofluid as a heat transfer fluid, the maximum temperature span of the device can be increased by approximately 20%. More importantly, by simultaneously optimizing a set of 10 key parameters, including the geometric parameters and the working conditions, the thermodynamic performance of the four-layer active magnetic regenerator prototype can be markedly enhanced by almost 40%. The newly established approach will be of considerable practical importance to both scientists and engineers since it will enable them to avoid costly experimental trials by optimizing a wide number of parameters.

Energy, exergy and exergoeconomic analysis and optimisation of the scale-up of a combined ammonia-water absorption pilot plant producing electricity and refrigeration

A low-temperature heat driven ammonia-water combined absorption cycle is studied in this paper from a thermodynamic and exergoeconomic point of view. The work is based on an absorption chiller prototype to which a partial admission turbine has been added in parallel to the cooling production line for the production of electricity.First, the performance of the pilot plant is analysed in the design point and in a base case characterised by a hot source temperature of 100 °C, intermediate source temperature of 25 °C and cold source temperature of 10 °C. Exergoeconomic performance is assessed for two different cost of the fuel thermal input. Being the small scale of the plant very penalising, the scale-up of the plant to a size 25 times bigger is evaluated. Unit cost of products in this case is strongly reduced, mainly because of the constant cost and increased efficiency of the turbine.Parametric studies are carried out on the temperature of the sources and on the size of components to assess how these parameters influence the performance of the cycle. Finally, an optimisation aiming at minimizing the unit cost of products is performed on the size of heat exchangers for the base case working point and fixing constant the size of the turbine. The optimised cycle layout allows reaching a unit cost of produced cooling of 10.14 $/GJ (0.036 $/kWh) and a cost of produced electricity of 40.45 $/GJ (0.145 $/kWh) if the cost of the thermal input is neglected. When a thermal input cost of 15 $/GJ is considered, the calculated cooling and electricity cost are 66.7 $/GJ (0.24 $/kWh) and 106.8 $/GJ (0.384 $/kWh) respectively. In both cases the optimal vapour split ratio between cooling and power production lines is found to be around 0.47.

OPTIMIZATION OF CONTROL PARAMETERS OF THERMAL PLUME INTERACTION WITH ENVIRONMENT

The present work is interested in the mathematical and numerical modeling of the effects of different parameters such as the angle of the cone, the length of the cone, the hot source radius, and the hot source length on thermal plume flow in interaction with its surrounding. The behavior of the guided thermal plume flow can give us more knowledge about the control parameters of different applications relevant to the environment and industry. This study investigates the thermal plume in interaction with its surrounding environment. To determine the control parameters that influence this flow we must study at the beginning mathematically and numerically the studied flow thru a natural convection flow generated by a circular hot source at the entrance of a vertical cone (Figure 1). In this work, the flow is natural convection, turbulent, steady, two-dimensional, incompressible flow. Numerical results are obtained using CFD analysis based on mathematical modeling of the flow and ANSYS-FLUENT software. The introduction of the hot source with a different radius causes an important change in the flow structure. The profiles show a very strong gradient in the temperature in the zone near the plume source for a specific cone angle. The comparison of different profiles indicates the optimized control parameters of the flow.

Superior Thermoelectric Performance of SiGe Nanowires Epitaxially Integrated into Thermal Micro-Harvesters.

Semiconductor nanowires have demonstrated fascinating properties with applications in a wide range of fields, including energy and information technologies. Particularly, increasing attention has focused on SiGe nanowires for applications in a thermoelectric generation. In this work, a bottom-up vapour-liquid-solid chemical vapour Deposition methodology is employed to integrate heavily boron-doped SiGe nanowires on thermoelectric generators. Thermoelectrical properties -, i.e., electrical and thermal conductivities and Seebeck coefficient - of grown nanowires are fully characterized at temperatures ranging from 300 to 600 K, allowing the complete determination of the Figure-of-merit, zT, with obtained values of 0.4 at 600 K for optimally doped nanowires. A correlation between doping level, thermoelectric performance, and elemental distribution is established employing advanced elemental mapping (synchrotron-based nano-X-ray fluorescence). Moreover, the operation of p-doped SiGe NWs integrated into silicon micromachined thermoelectrical generators is shown over standalone and series- and parallel-connected arrays. Maximum open circuit voltage of 13.8mV and power output as high as 15.6 µW cm-2 are reached in series and parallel configurations, respectively, operating upon thermal gradients generated with hot sources at 200 °C and air flows of 1.5 m s-1 . These results pave the way for direct application of SiGe nanowire-based micro-thermoelectric generators in the field of the Internet of Things.

Mock-up experimental study on the performance of a combined cooling-domestic hot water-ground source heat pump system

A ground source heat pump (GSHP) delivers heat from a condenser to the ground when it operates with cooling mode. However, the ground temperature increases when the GSHP system operates for a long time. The increased ground temperature can deteriorate the GSHP’s coefficient of performance (COP). To maintain the balance between the ground temperature and COP, the condensation heat from the cooling GSHP can be used for other heating systems before it is transferred to the ground. This study proposes a combined GSHP system connecting a three RT cooling GSHP with a 1.5 RT domestic hot water (DHW) heat pump, and the performance of the system was evaluated through mock-up experiments. In the combined GSHP system, the condensation heat of the cooling system was used as the heat source of the DHW system. Therefore, the ground temperature could be reduced, and the performances of both the GSHP cooler and DHW heater pump could be enhanced. Mock-up experiments for performance evaluation were conducted with cooling-only, DHW-only, and cooling-DHW operational modes. The results showed that cooling-DHW operation slowed down the change in heat source temperature. In comparison with those of the cooling-only and DWH-only heat pumps, the COPs of the cooling heat pump and DHW heat pump of the combined system were increased by 12.93% and 15.47%, respectively. Moreover, the total COP of the cooling-DHW combined GSHP system increased by 4.4% and 29.55% in comparison with those of the cooling-only GSHP and DHW-only GSHP systems, respectively. Practical application A combined GSHP system was proposed by connecting a GSHP for space cooling with a heat pump for DHW to mitigate the ground temperature changes due to the long-term operation of the GSHP system. The combined system reuses the condensation heat generated by the cooling heat pump as the heat source of the DHW heat pump for ensuring the system performance and building energy saving. Therefore, this system is suitable for buildings with large energy use and heavy hot water demand, especially in summer, such as hospital and hotel buildings.

Zeotropic mixtures study in plate heat exchangers and ORC systems

Based on the known scientific literature, there are no correlations in the scientific literature to predict the two-phase heat transfer coefficients of Hydrofluoroethers pure fluids and zeotropic mixtures used in plate heat exchangers. This work has allowed the development of evaporation and condensation correlations for such fluids. Correlations based on dimensionless numbers and working fluids critical properties gave promising results, with a prediction of the two-phase heat transfer coefficient around 15% for heat source and 50% for cooling source which led respectively to a prediction of 4% and 6% for the global thermal power exchanged. The behavior of the organic Rankine cycle heat sources and the working fluids used within was also been studied. For this purpose, the influence of the heat sources flow rates variation on the performance of the hot and cold exchangers was analyzed. Results obtained showed a similar behavior and performance variation of the heat exchangers both when using pure fluids and zeotropic mixtures. Zeotropic mixtures working fluids in ORC system are often supposed in the literature to significantly increase the performance of this thermodynamic cycle due to better heat transfer at the hot source. Nevertheless, the great majority of these studies are numerical and do not take into account the interactions and system effects existing within the thermodynamic cycle when using a mixture instead of a pure fluid. This work has allowed to highlight this complexity and to provide a better understanding of the use of zeotropic mixtures.

A novel coupling discretization method for modeling multi-phase heat exchangers

This paper presents a novel coupling discretization method for modelling multi-phase heat exchangers. In the method, the moving boundary method is adopted as the solver to solve each of the finite volume control volume divided by the method of finite volume method. When all finite volume control volume are solved, the finite volume control volume boundary values are updated based on the relationships of finite volume control volume. The solving procedure is initiated when the starting values of hot source fluid and cold source fluid outlet of the heat exchanger are given by the user and terminated when these values no longer change anymore. The experimental results of a plate heat exchanger with R245fa and Therminol 66 as cold source fluid and hot source fluid are adopted to validate the proposed model. Simulation results of 11 operating conditions show that the maximum deviation is within ?4% compared to the measured values. The model presented in this paper is appropriate for heat exchangers under operating conditions either with or without fluid phase change, such as the evaporator and condenser in the ORC system.

Upgrade of the relative calibration methods and Bayesian inference processing for electron cyclotron emission radiometry

An upgraded local oscillator (LO) hopping calibration method based on a blackbody hot source and a perturbation analysis of the magnetic field difference method are introduced in this work. The blackbody hot source is used to evaluate the difference in the relative coefficients between the two LO hopping frequencies in the same channels. Then the coefficients are obtained by multiplying the LO hopping frequencies coefficients by LO hopping calibration coefficients. In this way, it is more flexible and stable than the in-situ calibration. The magnetic field difference method provides another calibration method to obtain the relative calibration coefficients of the electron cyclotron emission radiometers (ECE). In general, the magnetic field difference method needs two similar shots but with a difference of 2.1% (for HL-2M) in the magnetic field. Meanwhile, there are some errors because of the deviation of detection positions in the same channels between the two shots. For evaluating the calibration errors, the impact of the displacement, Te perturbation of the core region, and magnetic field difference has been discussed. The result shows that a larger magnetic field difference can improve the accuracy of the calibration. In the end, Bayesian inference has been utilized to evaluate the calibration coefficients and get the most probable calibration coefficients along with its the confidence interval.