Analysis on stress and deformation of large‐scale concentric recuperator for high‐temperature PbLi loop

A lead lithium (PbLi) loop named as DRAGON‐V was constructed in China to test key technologies of material corrosion, thermal‐hydraulics, safety issues, etc for PbLi blanket of fusion reactor. The concentric recuperator, one of the most important components, was used to recover the enthalpy in the loop. To design the concentric recuperator structure, the tangent angle θ between straight pipe and elbow as well as the bending radius R for U‐type connecting elbow were analyzed, respectively. It was indicated that the elbow presented well thermal deformation–absorbing function and reduced the thermal stress. There was a little effect on the deformation and heat transfer for the variation of R and θ, but the stress intensity increased with bending radius R and decreased with tangent angle θ. The results showed that the stress intensity in the structure with θ = 5° and R = 1.5D was smaller than the others. And the optimized structure was evaluated according to standard of Steel Pressure Vessel—Design by Analysis, the structural strength met the design requirement, and large margin was kept for engineering application.     

Code development for analyzing transient behaviors induced by the in-box LOCA of liquid blanket in hydrogen fusion energy systems

Blanket is the strategic component in hydrogen fusion energy system, converting nuclear energy of hydrogen nuclei to thermal energy which could be further transported for the production of electricity. In order to investigate blanket transient behaviors induced by the in-box LOCA (Loss of Coolant Accident), a code named LBBFoam for high pressure compressible multi-phase flow is developed based on OpenFOAM, which is capable of simulating accident-induced pressure wave propagation in the blanket module. Two classic one dimension shock tube cases were simulated to verify the code. With this code, three scenarios with 8 MPa helium injection into PbLi in a blanket-like container were analyzed to capture pressure oscillation and bubble transportation characteristics. It is found that the maximum pressure in the PbLi zone exceeds and even doubles the helium injection pressure due to the reflection and superposition of pressure waves. This suggests that the traditional structural safety design limits of helium cooled PbLi blanket, which is usually set as the operating pressure of helium coolant, would be too low considering pressure wave superposition. This code will provide an assessment tool for the structural safety of blanket.     

A new calorimetric facility to investigate radiative‐convective heat exchangers for concentrated solar power applications

A new calorimetric facility for the aerothermal assessment of radiative‐convective heat exchangers in concentrating solar power applications has been developed and is described in this paper. The configuration of volumetric solar receivers enables concentrated sunlight to be absorbed and conducted within their solid volume, from where it is gradually transferred by forced convection to a heat transfer fluid flowing through their structure. Current design trends towards higher thermal conversion efficiencies have led to the use of complex intricate geometries to maximise temperatures deep inside the structure. The work presented aims to aid these objectives by commissioning a new experimental facility for the fully integrated evaluation of such components. The facility is composed of a high‐flux solar simulator that provides 1.2 kW of radiative power, a radiation homogeniser, inlet and outlet collector modules, and a working section that can accommodate volumetric receivers up to 80 mm × 80 mm in aperture. Irradiance levels and flow field nondimensional governing parameters are highly representative of on‐sun experiments at larger scales. Results from experiments with a siliconised silicon carbide monolithic honeycomb are presented, conducted at realistic conditions of incident radiative power per unit mass flow rate to validate its design point operation. Measurements conducted include absorber solid temperature distributions, air inlet and outlet temperatures, pressure drop, incident heat flux, and overall thermal efficiency. The relative influence of different sources of thermal loss is analysed and discussed.     

Large-scale hydrogen release in an isothermal confined area

INERIS has set up large-scale fully instrumented experiments to study the formation of flammable clouds resulting from a finite duration leakage of hydrogen in a quiescent room (80 m³ chamber). Concentration, temperature and mass flow measurements were monitored during the release period and several hours after. Experiments were carried out for mass flow rates ranging from 0.2 g/s to 1 g/s. The instrumentation allowed the observation and quantification of rich hydrogen layers stratification effects. This paper presents both the experimental facility and the test results. These experimental results have been used to assess and benchmark CFD tools capabilities [1].     

Introduction and preliminary testing of a 5 m3/h hydrogen production facility by Iodine–Sulfur thermochemical process

The Iodine–Sulfur (IS) or Sulfur–Iodine (SI) thermochemical water-splitting cycle is considered as one of the most promising hydrogen production methods through thermal chemical cycle process with heat. This paper introduces the new built hydrogen production testing facility of IS process made by industrial structural material (IS-5m³ facility). The TC4, Hastelloy C276 and SiC materials were chosen in this pilot-scale testing facility for different modules. The new designed structure of Bunsen reactor, HI decomposer and H₂SO₄ decomposer are described particularly, and the corresponding individual tests are successfully executed to verify the function of each section. Based on testing, a preliminary continuous experimental run was carried out in September of 2021 for about 4 h with the hydrogen production capacity of 80 L/h. The problems such as slight corrosion, lower hydrogen gas yield and shorter operation time faced in this experiment will be modified in the near future. A longer time operation and higher H₂ production rate test will be carried out soon.     

A novel design and experimental study of a cryogenic loop heat pipe with high heat transfer capability

A cryogenic loop heat pipe (CLHP) has been developed for future aerospace applications at TIPC (Technical Institute of Physics and Chemistry). This article presents a novel design of a cryogenic loop heat pipe and corresponding test system. The CLHP studied in this work has demonstrated to be able to operate in liquid-nitrogen temperature range using nitrogen as working fluid and to transfer large amount of heat over long distance with very small temperature difference. This device has been tested at three different orientations with respect to the relative position of the liquid line and the vapor line. The experimental results show that the CLHP can have a heat transfer capability of up to 12 W under horizontal and adverse gravity orientations and up to 20 W in liquid-nitrogen temperature range under gravity-assisted orientation.     

Induction heating apparatus for high temperature testing of thermo-mechanical properties

A low cost high temperature test facility designed and built for the purpose of thermo-mechanical testing is described. An induction heater provides variable heating rates, simple operation and easy access for temperature and strain measurement. Specially designed high temperature specimen grips with water-cooling allow for testing over long periods of time. Contact temperature and strain measurements are utilised to provide accurate and reliable results. Detail is given on the experimental procedure including calibration of the thermocouple temperature measurement. A validation study of the thermal expansion and tensile Young’s Modulus of carbon steel 1020 at temperatures up to 850 °C proves the accuracy of the test set-up and procedure. Results are given for the stress–strain curves of aluminium alloy 7000 T4 at various temperatures to further demonstrate the capabilities of the test facility. The measured thermo-mechanical properties of these materials were used to develop high temperature constitutive models for implementation in finite element thermal–structural analysis of hypersonic structures.     

General characteristics of two-phase flow distribution in a compact heat exchanger

An experimental loop representing a compact plate heat exchanger was built up to study the two-phase distribution in the different header channels. The test section consists of a cylindrical horizontal header and eight rectangular channels in which the liquid and vapour flow rates are evaluated and the flow inside the header can be visualized. Several geometrical and functional parameters to study the two-phase distribution were tested using “HFE 7100” at a temperature close to 57 °C and a pressure close to 100 kPa. A flow pattern map in the header was built up using the different entry parameters on which a quantitative understanding of the two-phase distribution could be deduced.     

Natural and forced ventilation study in an enclosure hosting a fuel cell

The purpose of the experimental work described in this paper is the determination of the ventilation requirements in enclosures containing fuel cells such that, in the case of a small non catastrophic release, the H₂ concentration in air for zone 2 ATEX (2% v/v) is not exceeded. A full scale fuel cell was placed inside the experimental facility having 25 m³ volume. Three different leaks were investigated (40, 90 and 180 Nlt/min) and H₂ concentrations were measured at five locations inside the facility. Several vent areas were examined for the cases of natural ventilation. When natural ventilation failed to ensure H₂ concentrations less than 2% v/v in the facility, mechanical ventilation using two fans was investigated.Based on the experimental set up, it was found that natural ventilation is sufficient when the air-flow calculated from ATEX guidelines is higher than 0.009 m³/s and the release flow rate corresponds to a non-catastrophic release, i.e. 40 Nlt/min. For higher release flow rates most of the ventilation configurations were not sufficient to maintain a H₂ concentration less than 2% v/v.All forced ventilation configurations examined (together with the free ventilation areas used) were sufficient to maintain a H₂ concentration below 2% v/v for 40 Nlt/min and 90 Nlt/min release flow rates. For the higher release flow rate of 180 Nlt/min, most of the forced ventilation configurations were insufficient.     

Experimental study of hydrogen production process with aluminum and water

This study reported a novel hydrogen production experimental set up, which utilizes the chemical reaction between aluminum and water to produce hydrogen. The developed experimental setup had an aluminum powder spraying subsystem integrated within the overall setup. The effectiveness of this hydrogen production experimental set up was improved using 149-μm aluminum powder, and nitrogen gas as the medium to facilitate the spraying of the aluminum powder. Furthermore, the study utilized sodium hydroxide as the reaction promoter. The various experimental conditions implemented during the testing process included changes in the water temperature and system inputs. The criteria used to evaluate the system performance were the hydrogen yield and hydrogen production rate. The tap water was able to achieve a full hydrogen yield due to its composition, however, the 50% increase in NaOH mass trial was able to achieve a higher yield of 97.15% and 95.44% for the 3g and 6g aluminum sample test respectively. Furthermore, seawater was found to achieve a yield of 58.8%, which can be considered a viable option for future testing. Furthermore, seawater's abundance also adds to its viability for future testing. Also, the study results showed that an increase in reaction temperature best facilitates a chemical reaction taking place. This was evident during the staring temperature of the water test for the 6g aluminum samples. For instance, the maximum hydrogen production rate for the 70 °C was 35.04 mL/s, while the smallest peak for hydrogen production rate was observed using the 40 °C as the starting temperature. The 40 °C test produced a maximum hydrogen production rate value of 27.99 mL/s.     

PSA Solar furnace: A facility for testing PV cells under concentrated solar radiation

The Plataforma Solar de Almería (PSA), the largest centre for research, development and testing of concentration solar thermal technologies in Europe, has started to apply its knowledge, facilities and resources to development of the Concentration PV technology in an EU-funded project HiConPV. A facility for testing PV cells under solar radiation concentrated up to 2000× has recently been completed. The advantages of this facility are that, since it is illuminated by solar radiation, it is possible to obtain the appropriate cell spectral response directly, and the flash tests can be combined with prolonged PV-cell irradiation on large surfaces (up to 150 cm²), so the thermal response of the PV cell can be evaluated simultaneously.     

Experimental study on cotton stalk combustion in a circulating fluidized bed

This paper summarizes the results of an experimental study on cotton stalk (CS) combustion in a circulating fluidized bed. The mixing and fluidizing characteristics of binary mixture of CS with 10–100 mm in length and alumina bed material with a certain size distribution in a cold test facility were studied. The results show that CS by itself cannot fluidize, and adding inert bed material can improve the fluidization condition. CS can mix well with alumina at fluidization number N = 3–7. As N is more than 7, there will exist a little more segregation. The study concerning combustion characteristics of pure CS was performed on a circulating fluidized bed with a heat input of 0.5 MW. The effects of fluidizing velocity, secondary air flow and gas flow to the loop seal on the bed temperature profiles were investigated. Although there is a little more segregation at N higher than 7 in the cold tests, the hot experimental results indicate that slight segregation has little effect on the steady combustion of the dense region. In this study, the concentrations of major gaseous pollutants (CO, SO₂ and NO) in flue (stack) gas were measured.     

Demonstration of a free-piston rapid compression facility for the study of high temperature combustion phenomena

A free-piston rapid-compression facility (RCF) has been developed at the University of Michigan (UM) for use in studying high-temperature combustion phenomena, including gas-phase combustion synthesis and homogeneous-charge-compression ignition systems. The facility is designed to rapidly compress a mixture of test gases in a nearly adiabatic process. A range of compression ratios, currently 16 to 37, can be obtained. The high temperatures and pressures generated by the RCF can be maintained for in excess of 50 ms, providing an order-of-magnitude increase in observation time over what can be obtained using shock tubes. The facility is instrumented for temperature and pressure measurements as well as optical access for use with laser and other optical diagnostics. This work describes the UM-RCF and its operation, establishes obtainable pressures and temperatures (over 1900 kPa and 970 K for predominantly N₂ gas mixtures and over 785 kPa and 2000 K for Ar gas mixtures), and demonstrates the repeatability of the UM-RCF experiments (<3% run-to-run variability in peak pressure) for combustion studies. The experimental results for time histories of temperature and pressure are interpreted using analytical isentropic models. Comparison between the isentropic predictions and the experimental data indicates excellent agreement and supports the conclusion that the core region of the test gases is nominally uniform and is compressed isentropically.     

Experimental and Numerical Investigation on a Two-Phase Natural Circulation Test Facility

A geometrically similar model of the proposed Advanced Heavy Water Reactor being designed and built by Bhabha Atomic Research Centre has been conceived and built at Indian Institute of Technology, Bombay. The basic objective of setting up such a facility and conducting experimental studies was to simulate the thermal-hydraulic behavior during the startup and also during part or full power operation. Owing to hydrodynamic instabilities observed in natural circulation system, it is necessary to know the stability boundaries. In this paper, the details of the experimental facility, experimental studies, and numerical simulations carried out using RELAP5/MOD 3.2 are discussed. Type I and type II stability boundaries and stable two-phase operation zones have been experimentally obtained at various pressures and inlet subcooling and the results are correlated using appropriate nondimensional numbers. Further, the experimental facility is modeled using the thermal-hydraulic code RELAP5/MOD 3.2. The single-phase pressure drops measured in the loop are used to estimate the appropriate loss coefficients used in the model. The model is then used to predict stability boundaries, and the predictions are compared with the experimental findings. The details of the experimental model and simulation results are presented. The capability of RELAP5/MOD 3.2 to predict the flow oscillations during instabilities is discussed.     

Experimental study on a cryogenic loop heat pipe with high heat capacity

Cryogenic loop heat pipes (CLHPs) are efficient heat transfer devices based on two-phase flow. Loop heat pipes for room temperature applications have achieved satisfactory thermal control functions with the benefits of no mechanical moving part, vibration isolation, thermal insulation, long heat transport distance and so on. While there exist many problems for low temperature applications of loop heat pipes, such as limited heat transport capacity, which could not meet the increasing requirement of instrument heat dissipation. This paper presents an advanced CLHP operating at liquid-nitrogen temperature range. An improved condenser structure is introduced to the CLHP, which greatly reduces the flow resistance and increases the cooling capability of the condenser. Many experiments have been carried out on the CLHP prototype for performance test, and one set of the experimental results with a 3.2 MPa fill pressure at room temperature is presented in this paper. It is shown that the advanced CLHP prototype can be operated reliably with a high heat transfer capacity up to 41 W and a limited temperature difference of 6 K across a 0.48 m transport distance.     

Synchronization of self-sustained thermostatic oscillations in a thermal-hydraulic network

Flow and temperature oscillations occur under normal conditions in a thermal system with thermostatic control. We present experimental results of the synchronization of multiple oscillators in the secondaries of a thermal-hydraulic network. The test facility is composed of three secondary loops with heat exchangers that exchange heat with a primary heating loop on one side and a primary cooling loop on the other. A thermostatic controller senses the temperature at the outlet of a heat exchanger and modulates the flow rate in that loop. The flow valve is partially closed if the temperature goes above an upper limit and is completely opened if it falls below a lower limit. As a consequence a self-sustained flow and temperature oscillation is set up in that secondary. The frequency of the oscillation depends on the dead-band between the upper and lower temperature limits. Coupled oscillators are set up by the simultaneous action of multiple controllers on different branches. Frequency locking, phase synchronization as well as phase slips are observed to occur due to thermal-hydraulic coupling between the controllers. The phenomenon is a function of the detuning between them which is altered by changing the dead-band of the controllers.     

An experimental analysis of subcooled leakage flow through slits from high pressure high temperature pipelines

The work presented here is an experimental investigation of the critical flashing flow of initially subcooled water through circumferential slits in pipes. The study provides first hand information about the prediction of leak flow rates in piping and pressure vessels retaining high temperature and high pressure. The dedicated experimental facility loop simulates the thermal hydraulic condition of Pressurized Heavy Water Reactors (PHWR). The critical flow characteristics found for varying leakage cross sections at different stagnation pressure and different degree of subcooling has been demonstrated in this paper. A marked decrease in mass flux has been found as subcooling decreases for a fixed stagnation pressure. More observation has revealed that the tighter slits or openings with very short duct as small as 0.8 cm flow length have different flow behavior than greater opening dimensions or with longer flow channels or that for nozzles. The critical flow has been seen to occur at higher pressure differentials along the flaws and prominent changes in the flow rate is reported to occur with varying dimensional parameters of the slit or cracks.     

Concept,design, and energy analysis of an integrated power-to-methanol process utilizing a tubular proton-conducting solid oxide electrolysis cell

An alternative power-to-methanol process based on an integration of a tubular proton-conducting solid oxide electrolysis cell into a methanol synthesis unit is explained, energetically evaluated and technically presented. Being currently developed in the joint research project DELTA, the novel process has the potential for a significant increase in system efficiency, if the heat from the exothermic synthesis reaction can be utilized and/or kinetic advantages can be achieved.For the experimental proof of the concept and a comprehensive characterization of the process, a test platform is currently under construction. The design of the flexible test facility with the complex technical integration of both processes (electrolysis and synthesis) is described briefly. The chemical reactor, where electrolysis and synthesis are taking place, allows for an operation at temperatures (for electrolysis) up to 700 °C, pressures of 10 MPa and a current (across the electrolysis cell) of up to 100 A. Moreover, a precise pressure balancing system between both gas volumes, an axial temperature measurement and the possibility of regulating both processes inside the pressure vessel are pivotal properties of the test facility.