Gas Temperature Research Articles

Thermometry with a dissipative heavy impurity

Improving the measurement precision of low temperature is significant in fundamental science and advanced quantum technology application. However, the measurement precision of temperature T usually diverges as T tends to zero. Here, by utilizing a heavy impurity to measure the temperature of a Bose gas, we obtain the Landau bound to precision δ2T∝T2 to avoid the divergence. When the initial momentum of the heavy impurity is close to be fixed and nonzero, the measurement precision can be δ2T∝T3 to break the Landau bound. We derive the momentum distribution of the heavy impurity at any moment and obtain the optimal measurement precision of the temperature by calculating the Fisher information. As a result, we find that increasing the expectation value P0 and reducing the variance Δ/2 of the initial momentum can help to improve the measurement precision. Moreover, under certain conditions, Δ/P0 is a relevant parameter, the smallness of which helps improve the thermometric precision of the probe. In addition, the momentum measurement is the optimal measurement of the temperature in the case that the initial momentum is close to be fixed and not equal to zero. The kinetic energy measurement is the optimal measurement in the case that the expectation value of the initial momentum is close to zero. Finally, we obtain that the temperatures of two Bose gases can be measured simultaneously. The simultaneous measurement precision is proportional to T2 when two temperatures are close to T. Published by the American Physical Society 2024

Study of the Incidence of CO and CO2 Gas Emission Levels and Temperature, of the Automotive Air Conditioning System Inside an Interprovincial Bus at Different Environmental and Operating Conditions

Study of the Incidence of CO and CO2 Gas Emission Levels and Temperature, of the Automotive Air Conditioning System Inside an Interprovincial Bus at Different Environmental and Operating Conditions

Split injection timing optimization in ammonia/biodiesel powered by RCCI engine

Employing carbon-neutral (NH3) and low carbon footprint (biodiesel) fuels in Reactivity Controlled Compression Ignition (RCCI) engine mode is one possible method for minimizing carbon emissions in diesel engines. In this study, a Compression Ignition (CI) engine was customized to run in RCCI mode, employing High Reactive Fuel (HRF) as biodiesel and Low Reactive Fuel (LRF) as ammonia (NH3). Based on our earlier findings, the proportion of ammonia in premixing is fixed at 40 %. In the first phase, the primary injection timing of the algal biodiesel varied between 12 and 21°CA bTDC at a preset pre-injection timing of 46°CA bTDC. In the next phase, the pre-injection time varied between 46 and 54°CA bTDC, with the optimal main injection time being 18°CA. The result suggested that the optimal main and pre-injection at 18 and 58°CA bTDC increased the Cylinder Pressure (CP) by 30.1 %, and peak HRR and combustion phase angle were advanced. Brake Thermal Efficiency exhibited an 11 % enhancement, with Brake Specific Energy Consumption decreasing by 24.1 %. Nitrogen Oxide levels saw an increase of around 39.5 %. In contrast, reductions of 19.2 %, 23.5 %, 39.7 %, and 21.7 % were observed in Hydrocarbons, Carbon Monoxide, smoke emissions, and Exhaust Gas Temperature, respectively, compared to the single injection under full load conditions.

Evaluation of ethanol-gasoline blends in SI engines using experimental and ANN techniques

Fuel combustion has become a major global concern, with much research focusing on the various emissions resulting from different types of fuels. Due to the harmful pollutant emissions from fossil fuels, the world has turned to renewable and alternative fuels to limit toxic emissions and greenhouse effects. Ethanol is a biofuel that, when used in spark ignition engines with gasoline can improve the octane number, combustion efficiency, and produce less emissions. The current research studies the effect of different ethanol blends E0, E5, E10, and E15 with gasoline 92 on engine performance parameters and emissions of a GX35 four-stroke engine at different engine speeds. The results along the speed range reveal that increasing ethanol amount leads to an average increase of 2.7%, 1%, and 1.1% in brake power (BP), brake thermal efficiency (BTE), and CO2 emissions, respectively. Meanwhile, it causes an average decrease of 28 °C, 3%, 15 ppm, and 0.18% in exhaust gas temperature (EGT), brake-specific fuel consumption (BSFC), HC, and CO emissions respectively. Moreover, the current study develops an Artificial Neural Networks (ANN) model for predicting the performance and emissions of spark ignition (SI) engines. Python programming language is used for ANN coding to train and validate the ANN model with E15. Regression plots were generated to visualize the correlation between the target and predicted data, indicating outstanding performance. The results confirmed the model’s reliability for BP, EGT, CO, CO2, and HC parameters with R2 values more than 0.99 and with acceptable performance for BSFC and BTE with R2 of 0.9339, and 0.9708, respectively. To ensure that the is no overfitting during the ANN study, we used different statistical methods, such as validation set, cross-validation, and learning curves.

Design of dual-channel Swiss-roll reactor for high-performance hydrogen production from ethanol steam reforming through waste heat valorization

Steam reforming is one of the most economical and efficient methods for hydrogen production. However, one of its glaring issues is the heat supply, which is used to maintain the reactions. Among reactors for hydrogen production, Swiss-roll reactors have exhibited exceptional performance in sustaining the heat required for reactions. Furthermore, heat supply via waste heat recovery has been an attractive industrial prospect for improving the sustainability of hydrogen production. This study proposes a design of a novel Swiss-roll reactor with dual channels to harvest waste heat from the flue gas to sustain the steam reforming reactions. Ethanol is used as a feedstock due to its environmentally benign properties. Numerical simulations are conducted to establish the reactor's catalytic reactions and heat transfer phenomena under the variations of gas hourly space velocity (GHSV), steam-to-ethanol (S/E) ratio, and inlet flue gas temperature. Heat recovery improves at higher GHSVs and lower S/E ratios at the cost of less efficient hydrogen production, while high inlet flue gas temperature improves heat recovery and hydrogen production. The novel reactor design can fulfill complete ethanol conversion maintained by heat recovered from waste flue gas, achieving 86.6 % hydrogen production efficiency and 72.7 % heat recovery under optimal operating conditions.

Experimental exploration of potassium compounds in the vicinity of a burning biomass pellet: From near-surface to downstream

The concentrations of gas-phase potassium hydroxide (KOH), potassium chloride (KCl) and atomic potassium (K(g)) were quantitatively measured from the near-surface to downstream area of burning pinewood pellets by a newly developed photofragmentation tunable diode laser absorption spectroscopy (PF-TDLAS) technique to reveal the original form of the released potassium. The novel arrangement of the PF-TDLAS system enabled a spatial resolution of ∼1 mm3, which made it possible to obtain temporal release profiles of K(g)/KOH/KCl at different heights above the burning pellet surface. Surface temperature and mass loss of the wood pellet as well as the gas temperature at measurement points were measured simultaneously. During the devolatilization stage, the release of all three potassium species was observed, with each of them accounting for ∼1/3; while in char oxidation stage, the release of KOH was dominant, but the release intensity was strongly influenced by the local oxygen content. The results from different measurement heights showed there was a notable difference in potassium release profiles of different potassium species over the near-surface area, where the detected potassium forms were the best representative of the originally released forms of potassium. For a period of time during the devolatilization stage, only K(g) was detected in the near-surface area, and the concentration was significantly lower than the downstream area where KOH and KCl coexisted. This suggested that a large amount of potassium might leave the pellet as organic-K, which cannot be detected by the PF-TDLAS method. During char oxidation stage, the total potassium concentration at the near-surface area was also lower than the downstream area, but it was due to the lack of oxygen at the measurement position. A potassium release mechanism during the devolatilization stage of biomass combustion was proposed based on the experimental measurements, and the results also indicated the importance of spatially resolved measurement.

A novel preheating system in pressure reduction stations—natural gas directly flowing inside deep borehole heat exchangers

To prevent hydrates from forming during the pressure reduction process in natural gas pressure reduction stations (i.e., city gate stations, CGS), fuel-intensive preheating methods are normally adopted, leading to high fuel consumption and carbon emissions. In this study, an innovative preheating system for natural gas is proposed, which is called the “Direct Geothermal Heating System” (DGHS). The main idea is to inject high-pressure natural gas into geothermal wells before the throttling valve; thus, natural gas is directly heated by the surrounding strata when it flows through the geothermal well. A proper temperature for natural gas should be ensured, as natural gas goes back to the ground for pressure regulation. The idea is performed based on the preheating configuration using coaxial deep borehole heat exchangers (DBHE). A mathematical model describing the flow and heat transfer processes of DGHS through DBHE is established to study its heat transfer characteristics. Additionally, the environmental and economic benefits of the proposed configuration are also investigated. Through the CGS case in this paper, the findings indicate that, over the fifteen years of preheating with a DBHE depth of 2000 m and inlet flow rate of 4.39 × 107 Nm³/year, the outlet temperature of the throttling valve remains within the range of 17 °C–37 °C, meeting the heating requirement of CGS. Among fifteen preheating cycles, the average peak heating power of the DBHE reaches 105.78 kW. In addition, in the 15th year, the proposed system has a 1/3 cost of a traditional line heater, along with a reduction of 46.43 × 105 kg in CO2 emission. The DGHS for natural gas is easy to establish and operate; once it is promoted on a large scale, it will produce huge economic and environmental benefits.

A Comprehensive Approach to Biodiesel Blend Selection Using GRA-TOPSIS: A Case Study of Waste Cooking Oils in Egypt

The transition to sustainable energy sources is critical for addressing global environmental challenges. In 2017, Egypt produced about 500,000 tons of waste cooking oil from various sources including food industries, restaurants and hotels. Sadly, 90% of households choose to dispose of their used cooking oil by pouring it down the drain or into their village’s sewers instead of using proper disposal methods. The process involves converting waste cooking oil (WCO) into biodiesel.This study introduces a multi-criteria decision-making approach to identify the optimal biodiesel blend from waste cooking oils in Egypt. By leveraging the grey relational analysis (GRA) combined with the technique for order preference by similarity to the ideal solution (TOPSIS), we evaluate eight biodiesel blends (diesel, B5, B10, B20, B30, B50, B75, B100) against various performance metrics, including carbon monoxide, carbon dioxide, nitrogen oxides, hydrocarbons, particulate matter, engine power, fuel consumption, engine noise, and exhaust gas temperature. The experimental analysis used a single-cylinder, constant-speed, direct-injection eight cylinder diesel engine under varying load conditions. Our methodology involved feature engineering and model building to enhance predictive accuracy. The results demonstrated significant improvements in monitoring accuracy, with diesel, B5, and B20 emerging as the top-performing blends. Notably, the B5 blend showed the best overall performance, balancing efficiency and emissions. This study highlights the potential of integrating advanced AI-driven decision-making frameworks into biodiesel blend selection, promoting cleaner energy solutions and optimizing engine performance. Our findings underscore the substantial benefits of waste cooking oils for biodiesel production, contributing to environmental sustainability and energy efficiency.

Quantifying leaks from Schrader valves in air conditioning systems

Refrigerants are a critical component of air conditioning and heat pump systems, but their high global warming potential has led to increasing concerns about their environmental impact. This research quantifies leakage from Schrader valves commonly used in air conditioning equipment. These valves serve as access points for refrigerant circuits and are often cited by service technicians as a source of leaks, contributing to greenhouse gas emissions. The study conducted laboratory testing of Schrader valves using an innovative experimental apparatus that tracked pressure and temperature of nitrogen gas contained by the valve over a 64-h test. The study found that 8 out of 61 used Schrader valves tested leaked at rates that would result in substantial refrigerant loss (M = 1,280 g/yr, SD = 3,168 g/yr, range = 9.4 to 9,117 g/yr). Gasketed caps were found to prevent refrigerant loss. Combining a Schrader valve with a gasketed cap significantly reduces the risk of leaks, and their use should be encouraged in air conditioning systems. The methodology developed for estimating leak rates from Schrader valves could be applied to other components in refrigeration systems, contributing to more comprehensive efforts to reduce refrigerant emissions.

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications.

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

Thermodynamic Study on the Vortex Teeth of Electric Scroll Compressors Based on Gradient Tooth Height

Through the analysis of the adhesion between the tooth head and axial clearance leakage attributed to vortex tooth shape deformation, an innovative tooth shape design concept has been introduced entitled “progressive change tooth high vortex tooth”. This unique design includes a gradual change in tooth height and an elevated vortex tooth profile, using temperature-sensitive materials to enhance the resolution of temperature loading on the vortex disc. By refining the process of resolving the temperature loading on the vortex disc, the mean temperature function of the fluid domain along the wall of the vortex tooth is calculated, and a steady-state temperature distribution model for the solid domain of the vortex tooth is formulated. Subsequently, a finite element model for the high eddy current disc is constructed using Abaqus 2021 finite element software, which facilitates the calculation of stress–strain distribution within the high eddy current disc under both gas pressure and temperature field loads. The results show that, especially under conditions of low speed and low exhaust pressure, the temperature load mainly influences the maximum deformation and stress distribution of the vortex tooth. Specifically, under the influence of heat-solid coupling, the maximum deformation of the progressive change tooth high vortex tooth occurs in close proximity to the central compression cavity, reaching up to 13 microns. These results provide a crucial theoretical basis for the structural design and performance optimization of the compressor.

Thermodynamic Study on the Vortex Teeth of Electric Scroll Compressors Based on Gradient Tooth Height

Through the analysis of the adhesion between the tooth head and axial clearance leakage attributed to vortex tooth shape deformation, an innovative tooth shape design concept has been introduced entitled “progressive change tooth high vortex tooth”. This unique design includes a gradual change in tooth height and an elevated vortex tooth profile, using temperature-sensitive materials to enhance the resolution of temperature loading on the vortex disc. By refining the process of resolving the temperature loading on the vortex disc, the mean temperature function of the fluid domain along the wall of the vortex tooth is calculated, and a steady-state temperature distribution model for the solid domain of the vortex tooth is formulated. Subsequently, a finite element model for the high eddy current disc is constructed using Abaqus 2021 finite element software, which facilitates the calculation of stress–strain distribution within the high eddy current disc under both gas pressure and temperature field loads. The results show that, especially under conditions of low speed and low exhaust pressure, the temperature load mainly influences the maximum deformation and stress distribution of the vortex tooth. Specifically, under the influence of heat-solid coupling, the maximum deformation of the progressive change tooth high vortex tooth occurs in close proximity to the central compression cavity, reaching up to 13 microns. These results provide a crucial theoretical basis for the structural design and performance optimization of the compressor.

Advancing hydrogen generation: Kinetic insights and process refinement for sorption-enhanced steam gasification of biomass utilizing waste carbide slag

Sorption enhanced steam gasification of biomass (SESGB) presents a promising approach for producing high-purity H2 with potential for zero or negative carbon emissions. This study investigated the effects of gasification temperature, CaO to carbon in biomass molar ratio [CaO/C], and steam flow on the SESGB process, employing carbide slag (CS) and its modifications, CSSi2 (mass ratio of CS to SiO2 is 98:2) and CSCG5 (mass ratio of CS to coal gangue (CG) is 95:5), as CaO-based sorbents. The investigation included non-isothermal and isothermal gasification experiments and kinetic analyses using corn cob (CC) in a macro-weight thermogravimetric setup, alongside a fixed-bed pyrolysis-gasification system to assess operational parameter effects on gas product. The results suggested that CO2 capture by CaO reduced the mass loss during the main gasification as the [CaO/C] increased. The appropriate temperature for SESGB process should be selected between 550 and 700 °C at atmospheric pressure. The appropriate amount of sorbent or steam could facilitate the gasification reaction, but excessive addition led to adverse effects. Operational parameters influenced the apparent activation energy (Ea) by affecting various gasification reactions. For each test, Ea at the char gasification stage was significantly higher than that at the rapid pyrolysis stage. The addition of CS notably increased H2 concentration and yield, while sharply reducing CO2 levels. H2 concentration initially rose and then fell with greater steam flow, peaking at 76.11 vol% for a steam flow of 1.0 g/min. H2 yield peaked at 298 mL/g biomass with a steam flow of 1.5 g/min, a gasification temperature of 600 °C and a [CaO/C] of 1.0. Increasing gasification temperature remarkably boosted the H2 and CO2 yields. Optimal conditions for the SESGB using CS as a sorbent, determined via response surface methodology (RSM), include a gasification temperature of 666 °C, a [CaO/C] of 1.99, and a steam flow of 0.5 g/min, under which H2 and CO2 yields were 464 and 48 mL/g biomass, respectively. CSSi2 and CSCG5 demonstrated excellent cyclic H2 production stability, maintaining H2 yields around 440 mL/g biomass and low CO2 yields (∼60 mL/g biomass) across five cycles. The study results offer new insights for the high-value utilization of agroforestry biomass and the reduction and resource utilization of industrial waste.

Thermodynamic and life cycle assessment analysis of polymer-containing oily sludge supercritical water gasification system combined with Organic Rankine Cycle

With the development of polymer flooding technology, polymer-containing oily sludge (PCOS) has become a major pollutant on offshore oil platforms. Supercritical water gasification system is an efficient and pollution-free technology compared to conventional PCOS treatment. However, the system model for PCOS has not yet been established and the theoretical model for system optimization is insufficient. In this work, a novel auto-thermal system is established based on supercritical water gasification technology for the treatment of PCOS. Through the thermodynamic analysis, an optimization plan is concluded and used for the establishment of a modified system with Organic Rankine Cycle. Results show that the two-stage reactor reduces the gasification reaction temperature from 652 °C to 502 °C, and the Organic Rankine Cycle system using Isopropanol recover 9.1 % chemical exergy of feedstock with the optimal parameters (superheat, evaporation temperature and circulating pressure). The energy and exergy efficiency of the modified system has increased by 52.4 % and 42.4 % compared to the original system. Besides, a life cycle assessment is adopted for the environment analysis. The results show that the increasing gasification temperature and PCOS slurry concentration can reduce system unit exergy loss. Global Warming Potential reaching the minimum value of 26.1 at 65 wt%.

Performance Analysis of a New Cogeneration System with Efficient Utilization of Waste Heat Resources and Energy Conversion Capabilities

This paper proposes a new type of cogeneration system coupled by Organic Rankine Cycle (ORC), Absorption Heat Pump (AHP), and Compression Heat Pump (CHP). The new system can meet the needs of different scenarios. Simulations were conducted to analyze the effect of different factors on the parameters and performance indexes of the new system and compared with the system of ORC, AHP, CHP. The results showed that the factors of flue gas temperature at evaporator1 outlet and CHP have the greatest effect on the parameters and performance indexes of the Organic Absorption-Compression Coupling Heat Power (OACCHP) system, and the effect of AHP on the parameters and performance indexes of the OACCHP system can be ignored. In the given range of flue gas temperature at evaporator1 outlet, the heat production of total and net work is reduced by 1.17% and 33.33%, respectively. In a given range of CHP evaporation temperature, the heat production of the total is reduced by 5.74%. In the given range of the outlet temperature of the gas cooler, the heat production of the total is increased by 10.58%. In a given working condition, compared with the single ORC system, the single CHP system, and the single AHP system, the thermal efficiency, COP, and energy earning rate of the OACCHP system are increased by up to 755.49%, 59.8%, 5.8%, respectively. Finally, the optimal operating conditions for different scenarios were determined.

Following fuel conversion during biomass gasification using tunable diode laser absorption spectroscopy diagnostics

The efficiency of the gasification process and product quality largely depend on the degree of fuel conversion. We present the real-time in-situ tunable diode laser measurements of main carbon and oxygen-containing species in the hot reactor core of a pilot-scale entrained flow biomass gasifier (EFG). The concentrations of CO, CO2, CH4, C2H2, H2O, soot, and gas temperature were measured during the air and oxygen-enriched gasification of stem wood at varying equivalence ratios. The experiments were made at the upper and lower optical ports inside a 4 m long, ceramic-lined, atmospheric EFG, allowing to access the degree of the fuel conversion inside the reactor. The exhaust composition was measured by micro-GC, FTIR, and low-pressure impactor. There was a good agreement between the data measured inside the reactor and at the exhaust for oxygen-enriched gasification implying that the chemical reactions are practically frozen downstream the optical ports. For air, the data indicated that the gasification reactions are still active at the measurement locations. Significant concentrations of C2H2, up to 5000 ppm, were found inside the reactor.

LAS-on-edge: A real-time laser absorption spectroscopic water vapor sensor on edge computing platforms

Real-time and in situ water vapor (H2O) sensors are increasingly demanded to indicate thermochemical parameters of energy systems. As an accurate, fast and non-intrusive sensing technology, laser absorption spectroscopy (LAS) enables simultaneous measurement of gas concentration and temperature. Due to the complex spectral computation, real-time and rapid LAS signal processing are still challenging. Most state-of-the-art LAS sensors utilize high-level computing units to post-process laser measurements in real time, hindering their portable deployment in harsh industrial environments. To address the above challenge, we developed an online LAS gas sensor on edging computing platforms, named as LAS-on-Edge. The developed sensor achieves an online monitoring rate up to 62.5 Hz by deploying a spectral-informed neural network on an embedded device. Simultaneously, it reserves the raw kilo-Hz measurements offline for underlying dynamics understanding. The LAS-on-Edge sensor’s compactness also enables its flexible and in situ integration. The sensor is firstly used to monitor a slow mist diffusion and accumulation process, exhibiting a high measurement accuracy with low spectra recovery residuals below 0.01. It is further applied to online monitor the H2O concentration and temperature variation during a lab-scale propane combustion process. It demonstrates a minimal temperature deviation of 1.86 % compared to the thermocouple reference in the flame. The sensor also successfully detects the fundamental flame pulsation at 5.65 Hz as well as high-frequency pulsations exceeding 200 Hz, thereby effectively reveals underlying flame dynamic behaviors.

Validation of effect of composite additive on optimized combustion characteristics of CI engine using AHP and GRA method

The primary focus of this study is the validation of composite additives with the help of additional optimization methods and the analysis of its effect on the combustion characteristics of compression ignition (CI) engines. Previous work on the identification of the correct multi additive combination by Taguchi and the TOPSIS optimization method has shown substantial improvements in the performance and emission characteristics of CI engines. The same work was extended using the GRA Optimization method with the Multi-Criteria Decision-Making (MCDM) optimization technique known as the Analytic Hierarchy Process (AHP) to validate the optimization results from the previous optimization work. Remarkably, all optimization methods yielded consistent results, pointing to the superiority of the composite additive sample ‘D8EH6E4 hence supporting the outcome of previous work. Subsequent testing and comparison of this novel composite additive with baseline diesel fuel for combustion characteristics analysis demonstrated notable improvements in combustion parameters, including a 25 % reduction in the rate of pressure rise, an 18 % decrease in net heat release rate, and a 6 % decrease in mean gas temperature.

Numerical Study of Porous Cylindrical Containment for the Fuel Element of a Centrifugal Nuclear Thermal Rocket

For deep-space propulsion and interplanetary exploration, the centrifugal nuclear thermal rocket (CNTR) has the ability to achieve a very high specific impulse (Isp) metric beyond that of conventional chemical rockets or solid-core nuclear thermal propulsion systems. The high Isp allows the rocket to use less propellant or achieve a higher velocity for shorter transit times. However, the cylindrical containment structure of a CNTR fuel element encounters extreme conditions, as it houses molten uranium at temperatures exceeding 1408 K, leading to challenges such as dissolution, chemical reactions, and thermal stresses that conventional materials struggle to withstand. This study aims to address this issue by analyzing appropriate materials for constructing the cylindrical containment component. The operating conditions of the annular porous medium that confines the liquid uranium in the centrifugal fuel element are simulated by conducting a comprehensive one-dimensional numerical analysis using a range of candidate porous materials, including Mo, W, zirconium carbide, and silicon carbide. The porous structure facilitates the flow of the hydrogen propellant into the internal molten uranium section, where it gains significant thermal energy while simultaneously cooling the cylinder. The containment cylinder has an internal temperature of 1478.1 K, exceeding the melting point of uranium, while the external gas temperature of the hydrogen propellant is much lower. This temperature difference induces significant thermal stresses in the cylinder. The porous containment cylinder made from molybdenum was able to maintain elastic deformation throughout the thickness of the cylinder, showcasing its ability to handle these extreme thermal stress conditions. Tungsten, on the other hand, experienced plastic deformation at the cylinder’s edges and elastic deformation through the middle radial locations. In contrast, the stresses experienced by the ceramic materials far exceeded their failure stress values, leading to brittle failure. These findings will help with the refinement of the CNTR design, edging it closer to practical implementation.

Long term relationships of electron density with solar activity

Greenhouse gases such as carbon dioxide and methane that are causing climate change may cause long term trends in the thermosphere and ionosphere. The paper aims to contribute to explore long term effects in the ionosphere focusing on the impact of solar activity changes. Peak electron density data derived from vertical sounding measurements covering 65 years at the ionosonde stations Juliusruh (JR055), Boulder (BC840) and Kokubunji (TO536), have been utilized to estimate the long-term behavior of daytime ionospheric F2 layer ionization in relation to the solar 10.7 cm radio flux index F10.7. In parallel, Global Navigation Satellite System (GNSS) based vertical total electron content (TEC) data over the ionosonde stations in combination with the peak electron density data have been used to derive the equivalent slab thickness τ for estimating long-term behavior in the time period 1996-2022. A new approach has been developed for deriving production and loss term proxies for studying long-term ionization effects from F2 layer peak electron density and TEC data. The derived coefficients allow estimating the long-term variation of atomic oxygen and molecular nitrogen concentrations including their ratio during winter months. The noon-time slab thickness values over Juliusruh correlate well with the decrease of F10.7 and the F2 layer peak height and enable estimating the neutral gas temperature. The equivalent slab thickness decreases by about 20 km per decade in the period 1996-2022, indicating a thermospheric cooling by about 100 K per decade for Juliusruh. Whereas the oxygen concentration decreases, the loss term, considered as a proxy for molecular components of the neutral gas, in particular N2, increases with the long-term solar activity variation. Considering 11 years averages of the production and loss terms under wintertime conditions, the long-term study reveals for the O/N2 ratio a percentage decrease of 5% per decade and for F10.7 about 3.1% per decade in a linear approach referred to the year 1970. Linear models of 11 years averaged NmF2 and foF2 from corresponding F10.7 show a very close correlation with the temporal variation of F10.7 until about 1990. The root mean square errors are in the order of 1.0 -1.3 ‧1010m-3 for NmF2 and 0.03-0.05 MHz for foF2. After 1990 the linear models clearly deviate from F10.7 at all selected ionosonde stations indicating a non-local effect.