Temperature distributions in MEMS microheaters during gas phase experiments in an environmental TEM.

The flameless oxyfuel combustion technology has been proven to be a promising new method to reduce the fuel consumption and pollutants in industrial applications [...]

Chemical kinetics for operando electron microscopy of catalysts: 3D modeling of gas and temperature distributions during catalytic reactions

Closed greenhouses are crucial buildings for agriculture in controlled environments because they offer the best growing conditions for crops and shield them from outside influences. Researchers can now better optimize design parameters for increased crop output and energy efficiency by simulating airflow and temperature distribution inside closed greenhouses with the use of computational fluid dynamics (CFD) modeling. We examine the temperature distribution and airflow patterns inside the greenhouse under various environmental conditions using CFD simulations. Our findings show that, in comparison to traditional greenhouse constructions, the novel design greatly improves temperature uniformity and lowers energy use. Moreover, the greenhouse's thermal insulation design minimizes heat loss during the colder months, enhancing energy efficiency overall. We offer important insights into how design changes affect airflow dynamics and thermal performance in enclosed greenhouses by utilizing CFD modeling. Our research highlights how effective CFD modeling can be in maximizing crop yields and achieving sustainable agricultural practices through greenhouse design optimization. The integration of novel design components for improved energy efficiency and crop yield is a feasible outcome of this research, which advances the field of closed greenhouse technology overall. The research highlights the value of using CFD modeling to inform the design of next-generation closed greenhouse systems and has important ramifications for sustainable agriculture methods and greenhouse management techniques. The goals were to assess how well various heating/cooling systems maintained the ideal environmental conditions for plant growth. A verified CFD model was used to run the simulations, which took into account a number of variables including the shape of the greenhouse, the outside environment, and the interior heat sources. Important discoveries include understanding temperature gradients, airflow patterns, and possible areas for environmental management enhancement are presented in this paper. Results showed that the species mass transfer of vapor (H2o) will vary over time.

In some nuclear reactors, under accidental conditions, core debris forms a molten pool, which is later located in a core catcher. The core catcher proposed by the authors uses special refractory material to absorb enthalpy of corium so that temperatures are within 1500 K, which is possible to cool with side cooling and top flooding. Since performing a full-scale prototypic experiment is extremely challenging and complex because of the involvement of very high temperatures and the presence of radioactive materials, it is important to develop a Computational Fluid Dynamics (CFD) model capable of simulating coolability of the melt pool with the above cooling strategy. In the present work, a CFD model was developed for the above purpose and was benchmarked with experiments conducted under simulated conditions by the authors. The experiment involved the melting of about 25 L of sodium borosilicate glass at about 1473 K and cooling it in a scaled-down core catcher model. In the presence of decay heat inside the melt pool, turbulent natural convection plays an important role in the temperature distribution inside the melt pool and on the vessel walls. For this, we used different turbulence models. Comparisons among the Standard k-ε, Shear Stress Transport (SST) k-ω, and two-dimensional (2D) Large Eddy Simulation (LES) turbulence models show that SST k-ω and 2D LES turbulences are found to be in good agreement with the experimental results for the temperature distribution in the melt pool, and SST k-ω is found to be computationally less expensive than 2D LES. In general, the CFD model is capable of simulating heat transfer with phase changes inside the heat-generating melt pool. In view of this, the model can be further extended to include cooling of the melt pool in the prototype core catcher. The evolution of crust formation has been investigated in detail using a CFD model.

This paper presents a computational fluid dynamics (CFD) modeling approach for designing intake and discharge structures in a discharge canal for nuclear and fossil power plants. It discusses how the CFD models are developed, what types of results can be obtained from the CFD modeling study and how the results are used for developing designs of the intake and discharge structures. The pros and cons of the CFD modeling method for this type of application are also discussed. Intake and discharge structures for a “Helper Cooling Tower South” will be added to the discharge canal of the Crystal River Energy Complex (CREC). The CFD modeling was used to confirm suitable locations for the new intake and discharge structures to minimize potential recirculation and potential loss of cooling tower efficiency, and to evaluate the erosion of the banks on the north and south side of the canal due to the flow from the discharge structure. The CFD model was developed using FLUENT for the existing and future configurations of the discharge canal that consists of the existing intake, discharges, and the new intake and discharge structures. The CFD modeling runs were performed to investigate three-dimensional flow patterns, velocities and temperatures in the discharge canal under current and future operating conditions. Current and future conditions refer to those before and after installation of the Helper Cooling Tower South Intake and Discharge structures, respectively. Comparing the CFD results (streamlines, temperature and velocity distributions, etc.) for the future conditions to those for the existing conditions, the locations and designs of the new intake and discharge structures were assessed and developed. This study demonstrates that the new intake is not impacted by the new and existing discharge structures, and the existing intake will perform similarly as it performs before the construction of the new intake and discharges. The study also identifies some sections of the canal banks and bottom that may need to be protected from erosion due to the impacts of the high velocity water from the discharge structures.

High performance computing (HPC) facilities consist of a large number of computer servers, which dissipate thermal energy in a data center. Efficient heat dissipation of these high density servers is a major concern to increase the life of electronic devices. Cooling of these devices involve thermal management strategies based on energy efficient cooling in a raised floor configuration, which depends on proper air flow distribution in an under-floor plenum, configuration of perforated tiles and arrangement of servers in racks. The current investigation was carried out with an objective to study air flow pattern inside plenum and to find out a better predictive tile model for air flow distribution through perforated tile. The full scale Computational Fluid Dynamics (CFD) model was used to predict flow over perforated tiles and temperature distribution over server racks inlet at different cold aisles. The governing equations (mass, momentum and energy) were solved to compute flow and temperature distribution in the computational domain. The RANS based k–e turbulence model was used for estimating turbulent kinetic energy (k) and turbulence dissipation rate (e). The under-floor blockages and CRAC locations were found to be significant parameters influencing flow distribution in different cold aisles. The CFD model was validated by carrying out experimental works. The deviation in flow rates obtained by CFD model was within 15 % with respect to experimental values for different rows in cold aisle. Cold aisle containment for over provisioned case of data centre was studied using modified body force model, which predicted better hot air entrainment and momentum rise of cold air as compared to porous jump model. The root mean square error (RMSE) of the temperature predicted by the modified body force model was 1.68 °C, whereas the RMSE predicted by porous jump model was 1.72 °C. Based on the CFD simulation studies, some energy saving opportunities were suggested for improving the thermal performance of the HPC facility.

In this study, a Computational Fluid Dynamic (CFD) model is established to obtain the 3-D flow characteristic, temperature distribution of the pressurized water reactor (PWR) upper plenum and hot-legs. In the CFD model, the flow domain includes the upper plenum, the 61 control rod guide tubes, the 40 support columns, the three hot-legs. The inlet boundary located at the exit of the reactor core and the outlet boundary is set at the hot-leg pipes several meters away from upper plenum. The temperature and flow distribution at the inlet boundary are given by sub-channel codes. The computational mesh used in the present work is polyhedron element and a mesh sensitivity study is performed. The RANS equations for incompressible flow is solved with a Realizable k-ε turbulence model using the commercial CFD code STAR-CCM+. The analysis results show that the flow field of the upper plenum is very complex and the temperature distribution at inlet boundary have significant impact to the coolant mixing in the upper plenum as well as the hot-legs. The detailed coolant mixing patterns are important references to design the reactor core fuel management and the internal structure in upper plenum.

In this study, a Computational Fluid Dynamic (CFD) model is established to obtain the 3-D flow characteristic, temperature distribution of the pressurized water reactor (PWR) upper plenum and hot-legs. In the CFD model, the flow domain includes the upper plenum, the 61 control rod guide tubes, the 40 support columns, the three hot-legs. The inlet boundary located at the exit of the reactor core and the outlet boundary is set at the hot-leg pipes several meters away from upper plenum. The temperature and flow distribution at the inlet boundary are given by sub-channel codes. The computational mesh used in the present work is polyhedron element and a mesh sensitivity study is performed. The RANS equations for incompressible flow is solved with a Realizable k-ε turbulence model using the commercial CFD code STAR-CCM+. The analysis results show that the flow field of the upper plenum is very complex and the temperature distribution at inlet boundary have significant impact to the coolant mixing in the upper plenum as well as the hot-legs. The detailed coolant mixing patterns are important references to design the reactor core fuel management and the internal structure in upper plenum.

The importance of performance monitoring is growing as the number of high-pressure, high-temperature (HPHT) wells continues to increase in deepwater and ultra-deepwater fields. Accurate prediction of HPHT well performance is essential for enhancing deepwater oil and gas production operations. Applying computational fluid dynamics (CFD) modeling to three- phase gas-oil-water flow in HPHT well conditions is an emerging concept. Multiphase flow in HPHT wells is extremely complex and depends on a multitude of effects including the properties of gas/oil/water, well geometries and configurations, operating pressures and temperatures, and multiphase flow patterns.In this work, simulations have been performed for three-phase flow in HPHT wells using CFD modeling techniques. The calculated results for phase velocity, pressure and temperature distribution are discussed in detail. The CFD simulation results are compared with measured field data and a finite difference-based mechanistic model. Reasonable agreements are achieved.Extensive parametric analysis of the three-phase flow system is performed to validate the viability of the CFD model as a predictive tool. The CFD model is demonstratively capable of predicting pressure drop and multiphase flow profiles in the HPHT well throughout various simulated production conditions. The experience gained from the CFD model studies can potentially improve the operations of HPHT wells in terms of increased productivity and enhanced reservoir management. In addition, results demonstrate the capability of the CFD model to predict various multiphase phenomena associated with HPHT well operations.

A Coupled FE and CFD Approach to Predict the Cutting Tool Temperature Profile in Machining

An oil-film bearing is a mechanical component that exploits the hydrodynamic lubrication principle to support a rotating shaft. In tilting-pad journal bearings, the pad ability to tilt allows the bearings to support the load, theoretically eliminating the cross-coupling forces that compromise the system stability, as occur in fixed geometry bearings. The temperature of the oil at the leading edge of the pad results from the oil-mixing process that occurs in the between-pad region. A correct prediction of this temperature is fundamental for the estimation of the static and dynamic properties of Tilting Pad Journal Bearings (TPJBs). The most common approach used for the estimation of the leading-edge temperature adopts the so-called mixing-coefficients approach. A hot oil carry-over coefficient is used to describe the fraction of hot oil coming from the upstream pad. A constant leading-edge temperature is obtained as a result. In general, the value selected for the hot oil carry-over factor strongly affects the results and needs to be accurately selected. In this study, a three-dimensional Computational Fluid Dynamic (CFD) model is introduced to simulate the mixing of the oil in the groove and to extract the temperature distribution at the leading edge of downstream pads. The CFD model is then linked to a thermo-hydrodynamic (THD) model for the oil-films that solves both the Reynolds and the energy equations. To validate the integrated model, an experimental campaign was carried out by introducing an array of temperature probes in the groove. Finally, the numerically estimated temperature distribution at the leading edge of the downstream pad is compared with the experimental results.

SOFCs/SOECs are typically composed of ceramic materials, which are highly complex at the nano-scale. Scanning and transmission electron microscopy (SEM and TEM) are routinely applied for studying these nano-scaled structures post mortem, but only few SOFC/SOEC studies have applied environmental TEM (ETEM). ETEM offer the possibility to record image series (movies) of the ceramic nanostructures with atomic scale resolution during exposure to a reactive gas environment at elevated temperatures. The present contribution focuses on the typical reduction preparation step for the state-of-the-art Ni/YSZ (YSZ = Y2O3-stabilized ZrO2) based anodes for SOFC and cathodes for SOEC. Specifically, the reduction of nickel oxide to form the catalytically active nickel surface is monitored directly at the nano- and atomic scale by using an ETEM. The reduction process was followed while exposing NiO/YSZ and pure NiO to H2 at temperatures from room temperature to ca. 800°C. The NiO/YSZ was prepared by crushing down a tape casted and sintered model anode/cathode into a fine powder. Previous studies based on averaging techniques have shown that the reduction of pure NiO is a relatively rapid process, while the reduction of NiO/YSZ is slower, which indicates that the presence of YSZ inhibits the reduction of NiO. In the presents in situ experiments the temperature dependent reduction profile are found similar for the both nano-scaled NiO and NiO/YSZ sample. The apparent inhibitive effect of YSZ on NiO reduction is therefore not caused by a direct interaction between NiO and YSZ, but is an indirect effect depending on the NiO being integrated in a macroscopic network of NiO/YSZ. A Titan E-Cell 80-300ST TEM was used for the in situ work in combination with the chip-based heating holder from Protochips which facilitated rapid temperature ramping for example from room temperature to 800°C in only 1 s. The ETEM results are compared to complementary averaging techniques such as thermo-gravimetric analysis (TGA) and X-ray diffraction analysis (XRD).The figure presents a TEM image series of NiO during exposure to 2 mbar H2 and constant temperature ramping rate of 1°C/min. The NiO observed in the first image at 320°C is dense. From the lower left corner a front of porous Ni is progressing until full reduction at 340°C.

Introduction: Medium and low technology greenhouses use natural ventilation as a method of temperature and humidity control. However, at certain times of the year, this is insufficient to extract excess heat inside the greenhouse, so devices such as hydrophanes (humidifiers) have been implemented to reduce the temperature. It is necessary to know the behavior of temperature and humidity, since both factors influence the development of crops and, therefore, their yield. Objective: To develop a computational fluid dynamics (CFD) model of a naturally ventilated zenithal greenhouse equipped with hydrophanes to understand the spatial and temporal distribution of temperature and humidity inside the greenhouse. Methodology: The experiment was carried out in a greenhouse equipped with hydrophanes and grown with bell pepper. Temperature and humidity measurements were performed from March 7 to 25, 2014. The ANSYS Workbench program was used for the 3D CFD modeling. Results: The CFD model satisfactorily described the temperature and humidity distribution of the greenhouse, with an error of 0.11 to 3.43 °C for temperature, and 0.44 to 10.80 % for humidity. Limitations of the study: Numerical modeling using CFD is inadequate to model the temporality of the variables. Originality: There are few studies that model humidity behavior with CFD and the use of hydrophanes in Mexico. Conclusions: The CFD model allowed visualizing the distribution of temperature and air humidity inside the greenhouse.

Langmuir analysis of electron beam induced plasma in environmental TEM

An exact prediction of temperature inside cylindrical lithium ion (Li-ion) batteries is important for their safe operation, extended life expectancy and development of next generation battery management systems. Research attempts have been made to place temperature sensors inside cylindrical Li-ion batteries [1, 2], but such arrangements are not yet commercially available. Alternatively, a computational fluid dynamics (CFD) approach can be used to accurately predict internal temperature profiles. This computational technique couples the multiphysics phenomena occurring inside cylindrical Li-ion batteries [3, 4]. In this work we present a coupled one dimensional electrochemical and three dimensional thermal CFD model, to predict internal and surface temperature profiles of a commercially available 21700 cylindrical Li-ion battery. Since the operating temperature has an important effect on Li-ion battery ageing, the CFD model is coupled with the solid electrolyte interphase (SEI) formation on the negative electrode. The SEI formation and growth is one of the main reasons that shortens the life expectancy of Li-ion batteries with liquid electrolytes and needs to be addressed in computational models [5]. The developed CFD model will be used to predict temperature profiles and SEI growth response to charge, discharge and rest duty-cycle periods of the 21700 cylindrical Li-ion battery. Surface temperature and voltage profiles acquired from the CFD model will be compared against experimental results to confirm the validity of the computational model. Such an extended model will represent a computational framework to potentially decrease the cost and number of 21700 cylindrical Li-ion battery experiments with different duty-cycle scenarios. It will also support the design of more advanced battery management systems and optimise the cooling and heating system of battery modules and packs.