Detailed Thermal Model Research Articles

Low-Cost Thermal Point Clouds of Indoor Environments

Abstract. The integration of low-cost thermal sensors with Apple Smart Devices supports the generation of 3D point clouds that include temperature indicators. This generates a new perspective for the study of buildings, allowing for fast and reliable examination of physical building structures. To the best of our knowledge, this study is the first to demonstrate the use of affordable sensors for 3D thermal point cloud generation. The study involved capturing data from the LiDAR and thermal sensors, followed by an extrinsic calibration process to align the datasets. Subsequently, the point cloud was segmented based on different acquisition poses of the device and finally, the thermal data was projected onto the 3D model, integrating temperature information with spatial coordinates. Our results demonstrate the effectiveness of the approach for three-dimensional point cloud generation in indoor environments, highlighting significant thermal variations and enabling thermal mapping of building structures. Furthermore, our findings underscore the feasibility of employing low-cost sensors for generating detailed thermal models, opening possibilities for widespread adoption in various building analysis applications. This approach provides a comprehensive and cost-effective solution for building monitoring, democratizing access to advanced evaluation tools.

Nonlinear mechanical response of UHSS rectangular plate under thermo-mechanical-metallurgical coupling

The mechanical properties of ultrahigh-strength steel (UHSS) produced through the gradient thermoforming process (GTP) are significantly influenced by residual stress and deformation. However, the precise distribution of these factors during GTP remains unclear. To address this issue, a detailed thermal model is developed, incorporating key heat transfer mechanisms, including coupled heat conduction and radiation, using the method of separation of variables. Furthermore, the displacement and stress fields of UHSS rectangular plates are derived using the differential quadrature method (DQM), accounting for phase transitions and external load. The combination of the separation of variables and DQM methods significantly improves computational efficiency. Furthermore, this study presents the first analysis of the combined effects of thermal load, phase transitions, and external forces on UHSS rectangular plates. Finally, through a combination of theoretical analysis, experimental validation, and case studies, the influence of material properties, geometric parameters, and external load on the temperature, stress, and displacement fields is examined. The findings reveal that heating rate, phase transitions, and external load play a critical role in the stress and displacement distribution in UHSS plates during GTP. This research provides a theoretical foundation for optimizing GTP process parameters and material design, ultimately enhancing the quality and performance of UHSS components.

Modeling and Controlling Many-Core HPC Processors: an Alternative to PID and Moving Average Algorithms

The race towards performance increase and computing power has led to chips with heterogeneous and complex designs, integrating an ever-growing number of cores on the same monolithic chip or chiplet silicon die. Higher integration density, compounded with the slowdown of technology-driven power reduction, implies that power and thermal management become increasingly relevant. Unfortunately, existing research lacks a detailed analysis and modeling of thermal, power, and electrical coupling effects and how they have to be jointly considered to perform dynamic control of complex and heterogeneous mpsoc. To close the gap, in this work, we first provide a detailed thermal and power model targeting a modern hpc mpsoc. We consider real-world coupling effects such as actuators’ non-idealities and the exponential relation between the dissipated power, the temperature state, and the voltage level in a single processing element. We analyze how these factors affect the control algorithm behavior and the type of challenges that they pose. Based on the analysis, we propose a thermal capping strategy inspired by Fuzzy control theory to replace the state-of-the-art PID controller, as well as a root-finding iterative method to optimally choose the shared voltage value among cores grouped in the same voltage domain. We evaluate the proposed controller with model-in-the-loop and hardware-in-the-loop co-simulations. We show an improvement over state-of-the-art methods of up to \(5\times\) the maximum exceeded temperature while providing an average of \(3.56\%\) faster application execution runtime across all the evaluation scenarios.

Experimentally validated thermal modeling for temperature prediction of photovoltaic modules under variable environmental conditions

In this work, a detailed analysis and thermal modeling for temperature prediction of a stand-alone photovoltaic module is performed. The study aims to present precise estimation of module temperature, since it is an important parameter for power output calculation. Hence, the required data were collected via experiments. Accounting for all heat transfer mechanisms, and following model validation, a proposed algorithm was implemented to investigate heat transfer from the module to its surrounding and predict different layers’ temperature. Results indicate that accurate energy distribution and temperature prediction was achieved by the adopted thermal model, only about 16% of the received energy is converted to electrical power while the rest is released by heat. Moreover, the proposed simulation algorithm provided one of the best results in comparison to literature models, achieving an R2 of 0.963 and a MAE of 1.883, which is very close to the best overall model by King at R2=0.973 and MAE=1.663. Additionally, two new models for module temperature prediction were proposed. After testing on new data, the explicit model provided a reasonable first approximation attaining an adjusted R2 of 0.97 and a MSE of 3.505, and an accurate implicit model, achieving a MSE of only 1.268.

Model Based Exploration of Physical Parameters for Liquid Hydrogen System Insulation Performance

Cryogenic Systems require a highly efficient insulation so as to limit the heat ingress and boil-off, which is generally achieved through the use of vacuum combined with an insulated media. The performance of Multi layer Insulation (MLI) will be investigated with detailed thermal models developed to account for all the heat transfer contributions, solid conduction, gaseous conduction and radiation. Results are presented for an usual cold vacuum pressure (CVP) corresponding to high vacuum (<10−6 torr) and compared with available experimental measurements for state of the art technologies. The nominal thermal performances are then evaluated for a cold temperature of 20K (representative of liquid hydrogen storage temperature), for a degraded CVP with hydrogen and nitrogen as residual gasses and for increased hot boundary temperatures. Other parameters are also discussed such as, the number of layers, material, layers density, venting options, assembly process and material optical properties. Finally, a sensitivity of the thermal performance is also presented with a pressure gradient through the insulation thickness, that could be induced by cryopumping, materials outgassing, pumping times or small leakages.

Development and application of a thermal model for the improved stepped solar still with a built-in passive condenser

Recently, the author proposed, fabricated, and experimentally tested an improved stepped solar still (ISS) with a built-in passive condenser, which exhibited significantly better performance than the standard version. Therefore, this paper presents a detailed transient thermal (theoretical) model for the ISS. The model is based on mass and energy balance equations for various components of the solar still, including the absorber, saline water, glass cover, insulation layer, backplate, condenser plate, and humid air in both the evaporator and condenser chambers. The model was programmed and solved using the MATLAB software. In contrast to previous studies that confined their model validation to a single day and specific conditions, this investigation rigorously validated the developed model using a comprehensive range of experimental data collected under diverse operational and meteorological conditions. Results show that, for all the conditions considered, there is very good agreement between the theoretical and experimental observations. The model has a maximum relative error of 3.7% in the estimation of daily freshwater yields, and it has a root-mean-square error (RMSE) of 4.7, 2.9, and 2.7 0C in the estimation of glass cover, absorber, and brine water temperatures, respectively. Finally, the model is used to predict and theoretically investigate the impact of meteorological design and operating parameters on the performance of the ISS. The analysis showed that a 20% increase/decrease in solar intensity would cause a corresponding increase/decrease in daily production by approximately the same amount.

Considerations on the Development of High-Power Density Inverters for Highly Integrated Motor Drives

In transportation electrification, power modules are considered the best choice for power switches to build a high-power inverter. Recently, several studies have presented prototypes that use parallel discrete MOSFETs and show similar overall output capabilities. This paper aims to compare the maximum output power and losses of inverters with different types (surface-mounted, through-hole-mounted and power modules) of commercially available switching devices, and, therefore, discuss the theoretical boundaries of each technology. The numerical analysis relies on detailed power loss and thermal models, with adjustments made for gate current and realistic parameters of the cooling system. The analysis includes two case studies with different targets, including minimum dimensional characteristics and maximum output power. The results demonstrate that discrete MOSFETs can provide improved capabilities in contrast to power modules under certain conditions.

Thermal Modeling of Photovoltaic Panel for Cell Temperature and Power Output Predictions under Outdoor Climatic Conditions of Jodhpur

The rise in the temperature severely affects photovoltaic cell efficiency and hence its power output. Moreover, it also causes the development of thermal stresses that may reduce their life span. Thus, there is a need for an accurate estimation of the cell’s working temperature. In this paper, a detailed thermal model based on various heat transfer modes involved and their governing equations has been presented to estimate the cell temperature of a PV module using MATLAB software under different climatic and solar insolation conditions. In order to validate the presented model, an experimental setup has been built and operated under actual outdoor conditions of Jodhpur, a city in the Thar Desert of Rajasthan. For the peak summer month of June, the predicted glass cover outer surface temperature has been found to be within 0.2–4.5°C of experimentally measured values and the back sheet temperature is found to be within 0.5–5.5°C. The predicted and measured power outputs have been found to be within 0.85–1.2 W while the efficiency values are within 0.17–0.38%. For the early summer month of April, the variations are 0.13–4.1°C, 0.2–4.1°C, 0.44–1.65 W, and 0.1–0.5% for glass cover temperature, back sheet temperature, power output, and efficiency, respectively. Thus, the predictions of the developed thermal model have exhibited a good agreement with the experimental results. The maximum glass cover temperatures recorded were 60°C and 65.5°C when the ambient temperatures were 35°C and 42°C near the noon for the early summer and peak summer day experiments, respectively. The presented model can be used to generate a year-round cell temperature data for the known environmental data of a location, which can help in the selection or development of appropriate cooling technology at the planning stage of the installation of a solar PV plant.

Emissive cathode immersed in a plasma: plasma–cathode interactions, operation and stability

Thermionic emission from a polycrystalline tungsten emissive cathode immersed in a magnetized plasma column is investigated experimentally and numerically. Electrical and optical measurements of the cathode temperature show a highly inhomogeneous cathode temperature profile due to plasma–cathode interactions. The spatially and temporally resolved cathode temperature profile provides an in-depth understanding of the thermionic electron current, in excellent agreement with experimental data. The plasma-cathode coupling leads to a sharp and heterogeneous rise in temperature along the cathode, which can eventually lead to unstable cathode operation, with divergent current growth. A detailed thermal modeling accurately reproduces the experimental measurements, and allows to quantify precisely the relative importance of heating and cooling mechanisms in the operation of the cathode immersed in the plasma. Numerical resolution of the resulting integro-differential equation highlights the essential role of heterogeneous ohmic heating and the importance of ion bombardment heating in the emergence of unstable regimes. Detailed thermal modelling enables operating regimes to be predicted in excellent agreement with experimental results.

Aggregate Modeling of Thermostatically Controlled Loads for Microgrid Energy Management Systems

Second-to-second renewable power fluctuations can severely hinder the frequency regulation performance of modern isolated microgrids, as these typically have a low inertia and significant renewable energy integration. In this context, the present paper studies the coordinated control of Thermostatically Controlled Loads (TCLs) for managing short-term power imbalances, and their integration in microgrid operations through the use of aggregate TCL models. In particular, two computationally efficient and accurate aggregate TCL models are developed: a virtual battery model representing the aggregate flexibility of TCLs considering solar irradiance heat gains and wall/floor heat transfers, and a frequency transient model representing the aggregate dynamics of a TCL collection considering communication delays and the presence of model uncertainty and time-variability. The proposed aggregate TCL models are then used to design a practical Energy Management System (EMS) integrating TCL flexibility, and study the impact of TCL integration on microgrid operation and frequency control. Computational experiments using detailed frequency transient and thermal dynamic models are presented, demonstrating the accuracy of the proposed aggregate TCL models, as well as the economic and reliability benefits resulting from using these aggregate models to integrate TCLs in microgrid operations.

Mechanical Ventilation Heat Recovery Modelling for AccuRate Home—A Benchmark Tool for Whole House Energy Rating in Australia

To manage energy-efficient indoor air quality, mechanical ventilation with a heat recovery system provides an effective measure to remove extra moisture and air contaminants, especially in bathrooms. Previous studies reveal that heat recovery technology can reduce energy consumption, and its calculation needs detailed information on the thermal performance of exhaust air. However, there are few studies on the thermal performance of bathroom exhaust air during and after showers. This study proposed a detailed thermal performance prediction model for bathroom exhaust air based on the coupled heat and mass transfer theory. The proposed model was implemented into the AccuRate Home engine to estimate the thermal performance of residential buildings with heat recovery systems. The time variation of the water film temperature and thickness on the bathroom floor can be estimated by the proposed model, which is helpful in determining whether the water has completely evaporated. Simulation results show that changing the airflow rate in the bathroom has little effect on drying the wet floor without additional heating. The additional air heater installed in the bathroom can improve floor water evaporation efficiency by 24.7% under an airflow rate of 507.6 m3/h. It also demonstrates that heat recovery can significantly decrease the building energy demand with the fresh air load increasing and contribute about 0.6 stars improvement for the houses in Hobart (heating-dominated region). It may be reduced by around 3.3 MJ/(m2·year) for the houses in other regions. With this study, guidelines for optimizing the control strategy of the dehumidification process are put forward.

Analysis of plate heat exchangers in binary flashing cycle using low-temperature heat source

The utilization of low-temperature heat sources represents an efficient technology that has the potential to significantly reduce both energy consumption and greenhouse gas emissions. Among the various technologies that harness low-temperature heat sources, the binary flashing cycle (BFC) stands out as a promising option. The application of the BFC is highly dependent on the thermal–hydraulic performance of the heat exchangers, which underscores the critical importance of effective heat exchanger design. The popular used plate heat exchangers (PHEs) are selected as suitable candidates for BFC system. Detailed thermodynamic, hydraulic, and thermal design models for the BFC system are developed for PHEs. The effects of geometrical parameters of the evaporator and condenser on the heat exchanger area and pressure drop are investigated simultaneously. It is revealed the increments in plate width and plate number leads to an augmentation of the heat exchanger area while concurrently reducing the pressure drop. Moreover, an optimal plate space is identified, which minimizes the pressure drop. Additionally, it is observed that the evaporator and condenser exhibit superior thermal–hydraulic performance, when the corrugation angle is approximately 60°. Furthermore, a multi-objective optimization approach employing Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is utilized to determine the optimal geometrical parameters. In order to classify the alternatives to the obtained Pareto front, the technique of order preference by similarity to the ideal situation (TOPSIS) is applied. It should be noted that the decision variable is influenced by the weight factor assigned to the objective function. The optimal plate width, channel spacing, plate number, and chevron angle range from 0.3–0.56 m, 3.5–5.9 mm, 20–24, 68–74°, 0.20–0.75 m, 3–7 mm, 30–32, and 56–59°, respectively. The study provides valuable insights for decision-makers involved in engineering application regarding the thermal–hydraulic performance of plate heat exchangers within the BFC system.

Distribution of surface heat flow and effects on the subsurface temperatures in the northern part of Thrace Basin, NW Turkey

The Thrace Basin in northwestern Turkey is a deep Eocene–Oligocene hydrocarbon-bearing sedimentary basin. The basin has potential for geothermal energy utilization in the future due to its favorable geological conditions. In this study, we combined the available bottom hole temperature (BHT) data from 70 points with the thermal conductivity and radiogenic heat productions of the basin formations, and generated a detailed thermal model of the northern part of the basin. For heat flow determinations from the BHT data, we applied Bullard’s thermal resistance method on formation thermal conductivities and thicknesses. The results give an average surface heat flow of 65.8 ± 11.3 mW/m2. We obtained high heat flow values (75–80 mW/m2) in the eastern and western sides, and the central part of the study area. These relatively high heat flow values can be explained by the combined effect of basement topography and the variations in the radiogenic heat production of the basement rocks. The calculated subsurface temperatures in selected hydrocarbon fields vary in the range of 45–64 °C at 1 km depth, 99–136 °C at 3 km depth, and 155–208 °C at 5 km depth as a result of local variations of the surface heat flow and formation thermal resistances. These variations in subsurface temperatures can have significant effects on the cost of geothermal energy production in future.

Late Miocene–early Pliocene tectonic to erosional exhumation in the northwest of the Arabia–Eurasia collision zone

AbstractThe exhumation of actively deforming orogenic systems is commonly due to the incision of river systems in response to tectonically driven surface uplift. However, a regional base level and/or climatic variations can also cause erosional exhumation. The temporal and spatial distinction of the dominant mechanism during the topographic evolution of orogens is challenging. Using detailed morphological analyses and thermal modelling of an intrusive body through triple dating (zircon U–Pb, ZHe, and AHe), combined with the previously published structural, detrital, and bedrock low‐temperature thermochronometry (apatite fission track and apatite helium) analysis, the transition from early Oligocene (~27 Ma) and middle Miocene (~12 Ma) tectonic exhumation to late Miocene–early Pliocene (~7–5 Ma) river incision and erosional exhumation in the Talesh Mountains in the NW of the Arabia–Eurasia collision zone was documented. The late Miocene‐early Pliocene incision and the contemporaneous rapid exhumation documented in the Talesh Mountains are related to the base‐level fall of the Caspian Sea due to its isolation from the Paratethys domain. The effect of this base‐level fall then migrated to the margin of the Iranian Plateau and captured the overspilled basins (~4 Ma).

Development of CMOS dosimetry in proton minibeams for enhanced QA and primary standard absorbed dose calorimetry

Performing accurate and reliable dosimetry in spatially fractionated beams remains a significant challenge due to the steep dose gradients and microscopic scale of features. This results in many conventional detectors and instrumentation being unsuitable for online dosimetry, necessitating frequent offline validation using radiochromic film.In this study, the use of a Complementary Metal-Oxide-Semiconductor (CMOS) detector for evaluation of relative real-time dosimetry of proton minibeam radiation therapy (pMBRT) was investigated. The linearity of the CMOS detector was investigated by varying the proton beam current, with a comparison to a PTW 34001 Roos ionisation chamber used to carry out an independent check. It was found that the relative peaks and valleys of the pMBRT beam could be measured, with results comparable to EBT3XD film. The high sensitivity of the CMOS detector meant it was able to measure dose profiles from peak to valley regions, something not possible with the EBT3XD. The CMOS detector was compared to the treatment delivery log files, with correlation in beam position seen as the beam is scanned along each slit, but not across; and agreement in beam intensity, with the CMOS detector able to observe beam interruptions.Lastly, the CMOS detector was used in conjunction with the NPL primary-standard proton calorimeter (NPL PSPC) for a preliminary study on combining the NPL PSPC with high resolution temporal information about the incident pMBRT beam. The ultimate aim of this approach is to facilitate detailed thermal modelling to reduce the overall uncertainty in the absolute dose measured from the calorimeter. In these experiments, saturation in the CMOS pixels prevented further thermal modelling of the radiation induced heat flow, however the instantaneous dose rate was observed to be comparable with the predicted NPL PSPC response obtained by masking the CMOS detector.

A 3-D Finite Difference Method for Obtaining the Steady-State Temperature Field of a PCB Circuit

The temperature rise caused by the heat generated by the on-board LED driver module during work will lead to the rise of product failure rate. The thermal analysis of this drive module should not only consider the heat and packaging of the LED itself, but also the influence of other power components. Common commercial thermal simulation software, such as ANSYS ICEPAK or FLOTHEM, usually requires detailed thermal models for such printed circuit board (PCB)-level thermal simulation, and requires a large number of simulation parameter settings and a long simulation time to obtain temperature results that are barely close to the actual. In this article, a 3-D finite difference method is proposed to obtain the steady-state temperature field of PCB circuit. The model can be used to calculate the steady-state temperature field of PCB circuit by setting different component sizes, power, and thermal conductivity. This article uses this method to calculate the temperature field of PCB steady-state working with MATLAB. The experimental measurement of PCB is compared with thermal simulation by ANSYS ICEPAK. It proves that the temperature results obtained by this method are similar to the actual test temperature compared with ANSYS ICEPAK. The time required for calculation is greatly reduced.

Compact Thermal Modelling of Magnetic Components using an Admittance Matrix Approach

Unlike semiconductor devices, the thermal modelling of magnetic components has not been standardized. Due to this lack of standardization in the academic community, most proposed magnetic component thermal models have not been evaluated for boundary condition independence. Hence, they cannot be classified as Compact Thermal Models (CTMs). In this study, CTMs of a PQ 30/40 inductor are developed using an admittance matrix-based approach. First, a Detailed Thermal Model (DTM) of the inductor under direct current excitation is developed and validated using experimental test results for power dissipation varying from 2.6 to 11.9 W. Following this, a single heat source CTM is developed from the DTM data using the admittance matrix approach. The thermal performance of the deduced CTM is evaluated for fifteen different boundary condition scenarios with surface heat transfer coefficients varying between 1 to 200 . The surface temperature and heat flux predictions were within 5% of the DTM results, while the junction temperature error was 10%. Most magnetic components like transformers and inductors have multiple loss sources. Hence, the DTM and CTM were re-evaluated for multiple heat sources. The resulting multi-heat source CTM was also observed to accurately predict surface temperatures and heat fluxes.

Investigation on the structure function of an electronic packaging to verify detailed thermal model assumptions

Investigation on the structure function of an electronic packaging to verify detailed thermal model assumptions

Combining welding-induced residual stress with thermal and mechanical stress in continuous welded rail

Continuously welded rail (CWR) with flash-butt welded joints has become standard practice for railway construction around the world. The welding process during rail installation or repair forms a residual stress field in the weldment altering locally the distribution and amplitude of the total stress that develops when the rail is in service. This paper presents a computer simulation approach to study the combined residual, thermal, and mechanical stress caused by the fastener system that develops in rail during the in-track welding and installation. The proposed approach simulates within a Finite Element Analysis framework the rail welding and installation sequence using detailed thermal and mechanical models of the weldment formation, and in-track installation. The model is validated with experimental measurements reported in the literature. It is implemented in a study that demonstrates the combined effects of such stresses with stress that develops in the rail during a daily solar-induced thermal cycle. A non-trivial stress gradient is observed where the mean tensile stress in the weldment is elevated relative to the rail at large. The higher mean stress warrants further investigations in view of fatigue performance under wheel loading. The proposed computer simulation approach is a tool that will enable future investigations focusing on more detailed examinations of weldment behavior, particularly concerning fatigue failures and track configurations, as well as in optimizing welding parameters to control the development of residual stresses.

Cell selection and thermal management system design for a 5C-rate ultrafast charging battery module

In the pursuit of ultrafast charging electric vehicles, cell selection and thermal management play a critical role. This work explores the selection of a suitable battery cell, design of a battery module thermal management system, and thermal modelling of the cells and module. Four different cells are compared, each with unique characteristics that present advantages and disadvantages for ultrafast charging. The cells are first characterized in a lab, and their suitability for ultrafast charging is evaluated based on the experimental results. Factors such as charging efficiency and required cooling system size are also considered. Simplified thermal models are used for comparison of the different cells. A three-cell, liquid-cooled test module is designed and constructed for a selected cell, and detailed fluid and thermal models are developed for the module. Module temperatures at steady state and over time—during a series of fast charges and over a repeated driving and fast charge cycle—are simulated and compared to lab measurements. For a 5C charge, a peak temperature of 34.6°C is measured in the lab, and modelled within 0.6°C.