Thermal Modeling Approach Research Articles

Thermal modeling and optimization of microalgal biomass production in the harsh desert conditions of State of Qatar

Microalgal culture in solar conditions raises several challenges, especially in the harsh desert areas of the Middle East where microalgal culture is a valuable candidate for biomass production on non-arable land.Here we investigate issues related to the temperature regimes involved in open culture systems used to cultivate microalgae in the State of Qatar. A generic thermal modeling approach is presented. The model produced takes into account all relevant heat exchanges involved in the process, including solar radiation absorption, water evaporation and convection with ambient air, and is proved valid for accurate prediction of temperature regimes.The model is then used to analyze heat exchanges and thermal behavior of the process for both summer and winter periods. Temperature regimes are then compared to the requirements of a heat-resistant and a temperate-climate microalgal strain. Finally, various simulations are run to identify how to set an optimized yearly microalgal culture in harsh desert conditions.

Testing Production Scenarios for (Anti-)(Hyper-)nuclei with Multiplicity-dependent Measurements at the LHC

The production of light anti- and hyper-nuclei provides unique observables to characterise the system created in high energy proton-proton (pp), proton-nucleus (pA) and nucleus-nucleus (AA) collisions. In particular, nuclei and hyper-nuclei are special objects with respect to non-composite hadrons (such as pions, kaons, protons, etc.), because their size is comparable to a fraction or the whole system created in the collision. Their formation is typically described within the framework of coalescence and thermal-statistical production models. In order to distinguish between the two production scenarios, we propose to measure the coalescence parameter B$_{A}$ for different anti- and hyper-nuclei (that differ by mass, size and internal wave-function) as a function of the size of the particle emitting source. The latter can be controlled by performing systematic measurements of light (anti-)(hyper-)nuclei in different collision systems (pp, pA, AA) and as a function of the multiplicity of particles created in the collision. While it is often argued that the coalescence and the thermal model approach give very similar predictions for the production of light nuclei in heavy-ion collisions, our study shows that large differences can be expected for hyper-nuclei with extended wave-functions, as the hyper-triton. We compare the model predictions with data from the ALICE experiment and we discuss perspectives for future measurements with the upgraded detectors during the High-Luminosity LHC phase in the next decade.

A Preconditioned Iterative Approach for Efficient Full Chip Thermal Analysis on Massively Parallel Platforms

Efficient full-chip thermal simulation is among the most challenging problems facing the EDA industry today, especially for modern 3D integrated circuits, due to the huge linear systems resulting from thermal modeling approaches that require unreasonably long computational times. While the formulation problem, by applying a thermal equivalent circuit, is prevalent and can be easily constructed, the corresponding 3D equations network has an undesirable time-consuming numerical simulation. Direct linear solvers are not capable of handling such huge problems, and iterative methods are the only feasible approach. In this paper, we propose a computationally-efficient iterative method with a parallel preconditioned technique that exploits the resources of massively-parallel architectures such as Graphic Processor Units (GPUs). Experimental results demonstrate that the proposed method achieves a speedup of 2.2× in CPU execution and a 26.93× speedup in GPU execution over the state-of-the-art iterative method.

A hybrid building thermal modeling approach for predicting temperatures in typical, detached, two-story houses

Within the residential building sector, the air-conditioning (AC) load is the main target for peak load shifting and reduction since it is the largest contributor to peak demand. By leveraging its power flexibility, residential AC is a good candidate to provide building demand response and peak load shifting. For realization of accurate and reliable control of AC loads, a building thermal model, which characterizes the properties of a building’s envelope and its thermal mass, is an essential component for accurate indoor temperature or cooling/heating demand prediction. Building thermal models include two types: “Forward” and “Data-Driven”. Due to time-saving and cost-effective characteristics, different data-driven models have been developed in a number of research studies. However, few developed models can predict temperatures in respective zones of a multiple-zone building with an open air path between zones e.g., an open stairwell connecting two floors of a home. In this research, a novel hybrid modeling approach is proposed to predict the average indoor air temperatures of both the upstairs and downstairs. This “hybrid” solution integrates both gray-box, i.e. RC model and black-box models. A developed RC model is used to predict the building mean temperature, and black-box model, in which the supervised machine learning algorithms are leveraged, is used to predict the temperature difference between the downstairs and upstairs. Compared with the measured data from a real house, the results obtained have acceptable/satisfactory accuracy. The method proposed in this study integrates the advantages of black-box and gray-box modeling. It can be used as a reliable alternative to predict the average temperatures in respective floors of typical detached two-story houses.

Pressure–enthalpy coupled thermal resistance and capacity model (PH-TRCM) for direct-expansion borehole heat exchangers: Application for supercritical CO2

A fully transient model for a direct expansion borehole heat exchanger was modeled by means of the thermal resistance and capacity model approach. The fluid defined in terms of pressure and enthalpy is coupled to the borehole heat exchanger and the surrounding ground described in terms of temperature. This model was compared against the well known infinite cylindrical source model and showed very good agreements for the mean fluid temperature, borehole wall temperature and borehole resistance. For supercritical CO2 applications, the work demonstrates that both the fluid's inlet pressure and mass flow rate influences the useful length of the BHE.

Power and thermal modeling approach for homogeneously stacked butterfly fat tree architecture in 3D ICs

AbstractLow‐power consumption and heat dissipation are becoming serious issues in the design process of the 3D integrated circuit (IC). The multiple dies are stacked and communicated through‐silicon vias to work as a single device to achieve high performance with minimum power and heat dissipation. This paper presents the power and thermal modeling approaches for the power/heat estimation of homogenous integration of network‐on‐chip‐based tree architecture in 3D IC design. The preliminary experimental work of power model is divided in 2 major parts of the design. The first part estimates the power of network‐on‐chip tree architecture on each stack/layer separately, and the second estimates the power dissipation of the uniformly distributed through‐silicon vias and input/output pads. The model uses a linear function to estimate the average power dissipation. The thermal model estimates the heat dissipation by using thermal sensors on different sections of the individual layer. For an entire IC design, the average power/thermal is extracted by simple addition of all power/thermal estimation results of the model. The design is operated with multiple frequencies to find the most appropriate frequency to minimize power dissipation. In experiments, the average maximum error is estimated 16.29%.

A computationally efficient thermal modelling approach of the linear friction welding process

Numerical models used to simulate LFW rely on the modelling of the oscillations to generate heat. As a consequence, simulations are time consuming, making analysis of 3D geometries difficult. To address this, a model was developed of a Ti–6Al–4V LFW that applied the weld heat at the interface and ignored the material deformation and expulsion which was captured by sequentially removing row of elements. The model captured the experimental trends and showed that the maximum interface temperature was achieved when a burn-off rate of between 2 and 3mm/s occurred. Moreover, the models showed that the interface temperature is reduced when a weld is produced with a higher pressure and when the workpieces are oscillated along the shorter of the two interface dimensions. This modelling approach provides a computationally efficient foundation for subsequent residual stress modelling, which is of interest to end users of the process.

Data integration and conceptual modelling of the Larderello geothermal area, Italy

In the frame of the Integrated Method for Advanced Geothermal Exploration (IMAGE) Project, a reliable exploration and resource assessment workflow was implemented on the basis of an integrated and multidisciplinary approach. Our study addressed to a better understanding of the thermal structure of the deepest part of the Larderello geothermal field (Southern Tuscany, Italy) by integrating structural, geological, geochemical, geochronological, petrological and geophysical data. With the aim to characterize the reservoir located nearby an important seismic reflector (the K-horizon), we systematized the available data and, successively, we applied a numerical thermal modelling approach to test our hypotheses and concepts.

Hydropriming accelerates seed germination of Medicago sativa under stressful conditions: A thermal and hydrotime model approach

This study determined the effects of priming on germination in response to temperature, water potential and NaCl. Thermal and hydrotime models were utilized to evaluate changes in parameters of the model after priming. Priming reduced the amount of thermal time in both cultivars, but slightly increased the base temperature for germination from 1.0 to 3.5°C in “Longdong”. Priming significantly increased germination rate at high water potential but had no effect at low water potential. Further, priming reduced the hydrotime constant but made the median base water potential value slightly more positive in both cultivars. Thus, priming increased germination rate in water but decrease it under severe water stress. Germination rate was significantly increased in both cultivars under salinity (NaCl) stress. Moreover, priming improved seedling growth in response to temperature, water and salinity stress in both cultivars.

Temperature Validation of 3D Model for the Reversing Hot Rolling in Connection with a Coil Model

The complex thermal modelling approach of the reversing hot strip rolling in connection with a coil model was developed. The coil model provides the modelling of the (un-) and coiling process. The modelling approach is based on object-orientated principals and implemented in MATLAB using library OOPDE and will be the base for the forecasting of the microstructure and the resulting material properties of strip during the reversing hot rolling. The model was validated using experimental data received after carrying out of the 2-pass reversing hot strip rolling of magnesium alloy AZ31. The results show a sufficient correspondence between experimental and calculated temperatures during the 1st and 2nd rolling pass.

Effect of design configurations on water flow window performance

Water flow window has very good application potential in zero carbon buildings of the warm climate. In this study, the effects of water-flow window configurations were investigated, such as the water layer thickness and glazing height-to-width ratio (GHTWR). The effects of distribution header design on the thermal and flow characteristics were also analyzed. Its long-term dynamic thermal performance was examined through a self-developed simulation program, of which the FORTRAN code was previously validated through comparison with experimental data. In the current study, the one-dimensional thermal simulation modelling approach was further justified through CFD analysis. Then the overall thermal performance of the window system was evaluated from the aspects of useful water heat gain and the impact on space air-conditioning power consumptions. A water layer of thickness around 15–20 mm and a GHTWR of 0.4 were found desirable for the tested cases. While the size and distribution of the header openings would affect the localized water flow and temperature distribution, their effect on the laminar upward flow and the final temperature rise is not significant.

Numerical study on temperature distribution of high-strength concrete-filled steel tubes subjected to a fire

High-strength concrete-filled steel tube (CFST) columns offer a number of benefits and are widely used in high-rise building construction. This paper presents a brand new thermal modeling approach in comparison with tremendous test data for the heat transfer analysis. A heat transfer model has been developed to predict the thermal response of high-strength CFST columns under standard fire conditions with consideration of a number of parameters: steel and furnace emissivity, thermal interface conductance and concrete strength. The verified numerical models discussed the variation of emissivity of steel surfaces and thermal interface conductance in fire. It can be concluded that the influence of emissivity and thermal interface conductance is considerable in the numerical analysis. It is also demonstrated that thermal behavior of high-strength CFST columns subjected to fire during heating and cooling stages, and providing the guidance on predicting thermal response of high-strength concrete-filled steel tube columns.

Diagonal and off-diagonal susceptibilities of conserved quantities in relativistic heavy-ion collisions

Susceptibilities of conserved quantities, such as baryon number, strangeness and electric charge are sensitive to the onset of quantum chromodynamics phase transition, and are expected to provide information on the matter produced in heavy-ion collision experiments. A comprehensive study of the second order diagonal susceptibilities and cross correlations has been made within a thermal model approach of the hadron resonance gas model as well as with a hadronic transport model, ultra-relativistic quantum molecular dynamics. We perform a detailed analysis of the effect of detector acceptances and choice of particle species in the experimental measurements of the susceptibilities for heavy-ion collisions corresponding to = 4 GeV to 200 GeV. The transverse momentum cutoff dependence of suitably normalised susceptibilities are proposed as useful observables to probe the properties of the medium at freezeout.

Thermal Modeling of an Intermediate Pressure Steam Turbine by Means of Conjugate Heat Transfer—Simulation and Validation

Today's power market asks for highly efficient turbines which can operate at a maximum flexibility, achieving a high lifetime and all of this on competitive product costs. In order to increase the plant cycle efficiency, during the past years, nominal steam temperatures and pressures have been continuously increased. To fulfill the lifetime requirements and still achieve the product cost requirements, accurate mechanical integrity based assessments on cyclic lifetime became more and more important. For this reason, precise boundary conditions in terms of local temperatures as well as heat transfer coefficients are essential. In order to gain such information and understand the flow physics behind them, more and more complex thermal modeling approaches are necessary, like computational fluid dynamics (CFD) or even conjugate heat transfer (CHT). A proper application of calculation rules and methods is crucial regarding the determination of thermal stresses, thermal expansion, lifetime, or creep. The aim is to exploit during turbine developments the limits of the designs with the selected materials. A huge effort especially in validation and understanding of those methodologies was done with detailed numerical investigations associated to extensive measurement studies at onsite turbines in operation. This paper focuses on the validation of numerical models based on CHT calculations against experimental data of a large intermediate pressure steam turbine module regarding the temperature distribution at the inner and outer casing for nominal load as well as transient shut-down.

Thermal modeling and heat flow density interpretation of the onshore Northwest Java Basin, Indonesia

Studies pertaining to heat flow density distribution in Indonesian tertiary sedimentary basins have been conducted intermittently throughout more than two decades. Even so, all of these studies have always concentrated on the basic compilations of thermal gradient, thermal conductivity, and terrestrial heat flow datasets or the study of basin thermal history rather than on the investigations into their present thermal regime. In addition, syntheses on the possible causes to the observed heat flow density distribution in these basins have been largely determined only on the basis of its correlation with geological and geophysical evidences. One basin experiencing this particular problem is the onshore Northwest Java Basin, where knowledge of the present-day subsurface temperature structure is virtually absent and interpretation of heat flow distribution has been mainly qualitative. For these reasons, in this study we have attempted to quantitatively characterize the present subsurface temperature distribution and surface heat flow density of the onshore Northwest Java Basin using a simple numerical thermal modeling approach, based on the most recent heat flow datasets. Taking into account a conductive heat transfer process, the modeling exercise is aimed at deriving a 3-D subsurface temperature distribution. The temperature distribution is translated into the predicted surface heat flow distribution. The modeled temperature field reveals its dependence on the geometrical aspects of the basin’s basement. Comparison between the computed and the observed heat flow densities, taking into account the uncertainties of both, suggests that advective heat transport by groundwater flow may be present, in addition to conduction. The modeling results are thus capable of demonstrating the importance of a quantitative approach in studying the present thermal state of a sedimentary basin.

Practical steady-state temperature prediction of active embedded chips into high density electronic board

Printed Wiring Board die embedding technology is an innovative packaging alternative to address a very high degree of integration by stacking multiple core layers housing active chips. Nevertheless this increases the thermal management challenges by concentrating heat dissipation at the heart of the substrate and exacerbates the need of adequate cooling. In order to allow the electronic designers to early analyse the limits of the in-layer power dissipation, depending on the chip location inside the board, various analytical thermal modelling approaches were investigated. Therefore the buried active chips can be represented using surface or volumetric heating sources according with the expected accuracy. Moreover the current work describes the comparison of the volumetric heating source analytical model with the state-of-art numerical detailed models of several embedded chips configurations, and debates about the need or not to simulate in full details the embedded chips as well as the surrounding layers and micro-via structures of the substrate. The results highlight that the thermal behaviour predictions of the analytical model are found to be within ±5% of relative error and so demonstrate their relevance to model an embedded chip and its neighbouring heating chips or components. Further this predictive model proves to be in good agreement with an experimental characterization performed on a thermal test vehicle. To summarize, the developed analytical approach promotes several practical solutions to achieve a more efficient design and to early identify the potential issues of board cooling.

Thermal error characteristic analysis and modeling for machine tools due to time-varying environmental temperature

The accuracy of machine tools is affected by both internal heat sources and time-varying environmental temperature. Therefore, the thermal deformation caused by environmental temperature variation is an important factor, which requires attention during thermal error modeling. In order to analyze the influence of time-varying environmental temperature on the thermal error of the machine tool, this paper proposed a thermal error modeling approach by using the thermal error transfer function of the machine tool. The approach was implemented in the following three steps. First, the thermal time constant of major components was calculated, according to structural parameters. Then, the thermal error transfer function of the components was derived. Finally, the thermal error transfer function of the whole machine was built based on the construction relationship. The analytical approaches of time domain and frequency domain were applied to obtain the thermal characteristics of machine tools based on the thermal error transfer function. Numerical simulations and the Z-axis operating experiment of three-axis milling machine were performed to verify the accuracy and effectiveness of the thermal error predicted model. The result shows that the proposed model is versatile and general with a clear modeling mechanism, which would provide a useful tool for the analysis and optimization design of machine tools with good thermal robustness.

A combined diffusion and thermal modeling approach to determine peak temperatures of thermal metamorphism experienced by meteorites

Carbonaceous chondrites are affected to different degrees by thermal and aqueous metamorphism on their parent bodies. However, the degree of alteration has been categorized mainly by relative scales and achieving quantitative information about metamorphic temperature by conventional mineral thermometry is problematic for low petrologic types. We have developed a general approach to estimate the metamorphic peak temperature experienced by type 3 chondrites from diffusion zoning in minerals, and have applied this approach to olivine in type I and type II chondrules of CO3 chondrites.To obtain metamorphic temperatures from diffusion zoning, we have combined diffusion modeling with thermal modeling of the meteorite parent body. The integrated diffusion coefficient over time (Γ) was identified as a useful parameter to quantify the extent of chemical change by diffusion occurring in a mineral during a given thermal history. Knowing the temperature dependence of the diffusion coefficient, Γ values can be calculated for each thermal history and be compared to the Γ values obtained from diffusion modeling. For thermal histories realistic for the parent body, Γ depends primarily on the metamorphic peak temperature, so that Γ values determined from diffusion profiles in meteorite minerals can be directly related to the metamorphic peak temperature. This general approach is relatively insensitive to uncertainties in the input parameters for the thermal model.We found that chemical zoning in type I and type II chondrule olivine of the CO chondrites Kainsaz and Lancé was largely influenced by solid state diffusion, which is evident from the observed correlation of zoning anisotropy with the crystallographic orientation. Chemical zoning in type II chondrule olivine is mainly igneous for CO chondrites of petrologic types up to at least 3.2 (Kainsaz) and was influenced only minor by diffusion during parent body metamorphism. Fe–Mg zoning in type II chondrule olivine and around sealed cracks in type I chondrule olivine yields similar Γ values, indicating a formation of both zoning features during a common thermal history on the parent body. In addition, Γ values for type II chondrule olivine correlate with metamorphic grade. The application of this approach on Fe–Mg zoning in type II chondrule olivine of CO3 chondrites yields estimates of maximum metamorphic peak temperatures ranging from 653 to 849K for different petrologic subtypes. The Fe–Mg zoning of type I chondrule olivine is not consistent with the peak temperature estimates from type II chondrule olivine, suggesting an additional contribution of solar nebular processes to type I chondrule olivine zoning prior to accretion into the parent body.

3-D FEM and Lumped-Parameter Network Transient Thermal Analysis of Induction and Permanent Magnet Motors for Aerospace Applications

Three dimensional (3–D), finite–element (FE) models and original lumped–parameter networks are developed for the transient thermal analysis of a permanent magnet motor (PMM) and an induction motor (IM) specifically designed and optimized for a demanding aerospace actuation application. A systematic comparison between the two different thermal modeling approaches is carried out using different loading conditions.

Conceptual hydrodynamic-thermal mapping modelling for coral reefs at south Singapore sea

Coral reefs are important ecosystems that not only provide shelter and breeding ground for many marine species, but can also control of carbon dioxide level in ocean and act as coastal protection mechanism. Reduction of coral reefs at Singapore coastal waters (SCW) region remains as an important study to identify the environmental impact from its busy industrial activities especially at the surrounding of Jurong Island in the south. This kind of study at SCW was often being related to issues such as turbidity, sedimentation, pollutant transport (from industry activities) effects in literatures, but seldom investigated from the thermal change aspect. In this paper, a computational model was constructed using the Delft3D hydrodynamic module to produce wave simulations on sea regions surrounding Singapore Island. The complicated semi-diurnal and diurnal tidal wave events experienced by SCW were simulated for 2 weeks duration and compared to the Admiralty measured data. To simulate the thermal mapping at the south Singapore coastal waters (SSCW) region, we first adapted a conversion of industrial to thermal discharge; then from the discharge affected area a thermal map was further computed to compare with the measured coral map. The outcomes show that the proposed novel thermal modelling approach has quite precisely simulated the coral map at SSCW, with the condition that the near-field thermal sources are considered (with the coverage area in the limit of 20km×20km).