Temperature Standard Deviation Research Articles

A comprehensive thermal analysis for the fast discharging process of a Li‐ion battery module with liquid cooling

Appropriate temperature range and distribution is necessary for Li-ion battery module, especially in real application of electric vehicles and other energy storage devices. In this study, a comprehensive design of liquid cooling–based thermal management system for a Li-ion battery module's fast discharging process is investigated, and thermal analysis and numerical computation are conducted. The effects of different flow directions, different shapes of the liquid channels, different widths of channels, different thicknesses of cold plate, and the comparison between uniform and nonuniform channels' distribution are analyzed. Simulation results indicate that the liquid cooling system provides acceptable cooling performance in preventing heat runaway of the battery module under 5C discharging current rate. A five-channel cooling plate can reduce the maximum temperature with appropriate design. Additionally, specific flow direction mini-channels, different shapes of the liquid-channels, and nonuniform channels are designed to compare the maximum temperature and uniformity of temperature distribution in the module. Maximum temperature can be improved through the increase of channel width and thickness of the cooling plate. The original design is proved to be the best design considering the maximum temperature, maximum temperature deviation, and final temperature standard deviation of the fast discharging process.

Determination of the “Wave Turbopause” Using a Numerical Differentiation Method

AbstractThis paper proposes a new algorithm to determine the wave turbopause based on numerical differentiation using temperature data collected from the Sounding of the Atmosphere using Broadband Emission Radiometry onboard the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite. The vertical gradient profile of the temperature standard deviation, which serves as a proxy of wave activity, is obtained based on Tikhonov regularization. In the vicinity of the altitude of wave turbopause, wave damping is much reduced, and upward wave propagation occurs with little damping effect. The corresponding vertical gradient profile should reach a maximum with values that are no longer negative. Thus, we determine the wave turbopause as the unique maximum that is the first after the last change in the derivative value from negative to positive. The wave turbopause altitudes determined by this new method agree well with those of previous studies, especially regarding the behavior of the monthly variation. The error of the wave turbopause altitude derived from this new method is 1.9 km, which is much improved from the error of 3.3 km estimated by the previous method. Additionally, latitudinal variations of the wave turbopause altitude for different seasons and their monthly variations for 0°, 30°N, and 70°N latitudes during 2016–2018 are presented. Similar to the mesopause, the wave turbopause also exhibits a two‐level structure with a summer minimum at high latitudes.

Stochastic coupling analysis of uncertain hydro-thermal properties for embankment in cold regions

Abstract In cold regions, the uncertain thermal property of embankment is an important basis for the safety design and construction. Especially for the high water content ground, the engineering properties are very complex and special because of the existence of moisture migration, which can cause a strong coupling effect for the stochastic hydro-thermal processes. In order to evaluate the uncertain hydro-thermal properties of embankment in cold regions, a stochastic analysis on coupled moisture migration, thermal conduction and ice-water phase transition is presented. The hydrothermal parameters are considered as random fields. A method to calculate local average variance from point variance is proposed, and a coupled modeling of stochastic hydro-thermal processes for the frozen soil is developed. The uncertain hydro-thermal behavior of an embankment along the Qinghai-Tibet railway is calculated by a stochastic coupling program, and the change rule of statistical characteristics for the temperature and unfrozen water content is obtained and analyzed. The study provides a new way to evaluate the stochastic hydro-thermal properties of embankment in cold regions, and it shows that water migration can promote uncertain heat transfer and increase the validation of temperature characteristic in frozen soil. The larger standard deviation of unfrozen water content is at the bottom of the embankment on July 15 and October 15. The average standard deviations of temperature and unfrozen water content increase with time, and the variability of uncertain hydro-thermal properties are becoming more and more obvious. These results can improve our understanding of the stochastic coupling effect of uncertain hydro-thermal process for embankment and provide a theoretical basis for design, operation and maintenance of embankment engineering in cold regions.

Multi-objective optimization design of double-layered reverting cooling plate for lithium-ion batteries

To keep the operating temperature of Li-ion battery for electric vehicles in the optimum range, a novel double-layer reverting channel was proposed, which included the collecting layer channel and the dispersed layer channel. Furthermore, the structural theory was invoked to design the reverting channel to reduce the pressure drop. To obtain the optimal cold plate structure and achieve the trade-off between objective functions (maximum temperature, surface standard deviation, and pressure drop), a multi-objective optimization design method based on genetic algorithm was applied. Taking the volume occupied by the cooling channel in the cooling plate as the constraint, the width ratio, the length ratios of the X axes and Y axes, and the channel thickness were chosen as the design variables. The Latin Hypercube Sampling (LHS) was used to select 40 design points in the design space. Further, the response surface approximation (RSA) surrogate model was adopted to establish the relationship between objective functions and the design variables. The optimization results were validated by numerical simulation, and they had reached an agreement that the new double-layered cooling channel can ensure the lithium-ion batteries to work in the optimum temperature range. Moreover, the multi-objective optimization design can reduce the maximum temperature, surface temperature standard deviation and pressure drop of the cold plate at the same time.

Assessment of left ventricle magnetic resonance temperature stability in patients in the presence of arrhythmias.

Magnetic resonance (MR) thermometry allows visualization of lesion formation in real-time during cardiac radiofrequency (RF) ablation. The present study was performed to evaluate the precision of MR thermometry without RF heating in patients exhibiting cardiac arrhythmia in a clinical setting. The evaluation relied on quantification of changes in temperature measurements caused by noise and physiological motion. Fourteen patients referred for cardiovascular magnetic resonance imaging underwent an extra sequence to test the temperature mapping stability during free-breathing acquisition. Phase images were acquired using a multi-slice, cardiac-triggered, single-shot echo planar imaging sequence. Temperature maps were calculated and displayed in real-time while the electrocardiogram (ECG) was recorded. The precision of temperature measurement was assessed by measuring the temporal standard deviation and temporal mean of consecutive temperature maps over a period of three minutes. The cardiac cycle was analyzed from ECG recordings to quantify the impact of arrhythmia events on the precision of temperature measurement. Finally, two retrospective strategies were tested to remove acquisition dynamics related either to arrhythmia events or sudden breathing motion. ECG synchronization allowed categorization of inter-beat intervals (RR) into distinct beat morphologies. Five patients were in stable sinus rhythm, while nine patients showed irregular RR intervals due to ectopic beats. An average temporal standard deviation of temperature of 1.6°C was observed in patients under sinus rhythm with a frame rate corresponding to the heart rate of the patient. The temporal standard deviation rose to 2.5°C in patients with arrhythmia. The retrospective rejection strategies increased the temperature precision measurement while maintaining a sufficient frame rate. Our results indicated that real-time cardiac MR thermometry shows good precision in patients under clinical conditions, even in the presence of arrhythmia. By providing real-time visualization of temperature distribution within the myocardium during RF delivery, MR thermometry could prevent insufficient or excessive heating and thus improve safety and efficacy.

Assessment of difference in the atmospheric surface layer turbulence characteristics during thunderstorm and clear weather days over a tropical station

The present study analyses the atmospheric surface layer characteristics (non-dimensionalised standard deviation of temperature and wind) during days of thunderstorm (DT) and clear weather days (CWD) during the months of pre-monsoon for years 2007, 2009 and 2010 at a tropical station Kharagpur (22°30′N, 87o20′E), India using the data sets collected by a 50-m instrumented tower. The study proposes site-specific relationships for thermal and mechanical characteristics of turbulence concerning atmospheric stability during DT and CWD during the pre-monsoon season. Although the analysis has not considered the data during the thunderstorm events (removed due to quality check), the relationships are different in CWD and DT cases. It is observed that during unstable stratification of CWD, values are less dispersed compared to the unstable region of DT. The study also reveals differences for stable stratification of DT and CWD days; even the thunderstorms are occurring during an unstable regime. The turbulence intensity for wind obeys the 1/3 power law, whereas for the unstable (stable) region of the temperature the − 1/3 (− 1) slope exists.

Sperm whale (Physeter macrocephalus) acoustic ecology at Ocean Station PAPA in the Gulf of Alaska – Part 2: Oceanographic drivers of interannual variability

Understanding top predator responses to environmental variability is key to assessing potential impacts of global warming on marine ecosystems. However, tracking environmental changes and their effects across multiple trophic levels up to predators can be difficult. Here, we related the interannual (2007–2012) acoustic occurrence of sperm whales (Physeter macrocephalus) at Ocean Station PAPA (OSP), in the offshore Gulf of Alaska (GOA), to environmental drivers within an explicit time-series modeling framework. In a model based on a combination of in-situ and remotely sensed variables, ocean heat content (HC), meridional current (V), eddy kinetic energy (EKE), strength of the permanent pycnocline (maxBVF), sea surface temperature (SST) and SST standard deviation (SSTsd) explained 51% of the variability in sperm whale presence, indicating a positive relationship between sperm whale occurrence and increased ocean heating, vertical stratification, and circulation. Sperm whale detections were anomalously high in summer 2010 and winter 2011, and anomalously low at the end of summer and winter 2008, and spring 2011. Results suggest these strongly anomalous detection events reflect a response to El Niño–Southern Oscillation (ENSO) events, with an 8-month lag. In the study area, El Niño leads to a stronger permanent pycnocline, a weakening of the Alaska Gyre, a northward expansion of the North Pacific Subarctic Frontal Zone, and a prevalence of offshore mesoscale eddies, likely favoring the abundance of squid and their predator, the sperm whale. The overall results are consistent with a scenario of increasing sperm whale occurrence at high latitudes under increased ocean warming.

An integrated framework for minimization of inter lithium‐ion cell temperature differences and the total volume of the cell of battery pack for electric vehicles

AbstractThere is not much research carried out on factors such as temperature differences in different regions of battery pack, which is highly important and poses a great challenge. Temperature changes across batteries affect the battery pack performance and its life span largely. Thus, the present work proposes the Integrated Finite Element‐Meta‐Optimization Framework for solving this problem. The integrated framework includes the formulation of Finite Element Model of a battery pack and Meta‐Optimization Framework for multi‐objective minimization of three objectives such as the inter‐cell temperature differences, temperature standard deviation and the total volume of the cell. In this framework, firstly Support Vector Regression (SVR) model is formulated based on the data and the SVR parameters are optimized using a genetic algorithm. It can conclude that the resulting model has a coefficient of correlation metric of 99%. The simulated annealing algorithm is then applied to find the optimal values of inter‐cell and cell‐enclosure distances for minimization of inter‐cell temperature differences and the total volume of the cell. Optimization analysis concluded that the volume of the battery pack was decreased by 29%, temperature difference (K) by 42% and SD of the temperature over the entire pack decreased by 55%.

Multi‐objective design optimization for mini‐channel cooling battery thermal management system in an electric vehicle

Lithium-ion battery packs have been generally used as the power source for electric vehicles. Heat generated during discharge and limited space in the battery pack may bring safety issues and negative effect on the battery pack. Battery thermal management system is indispensable since it can effectively moderate the temperature rise by using a simple system, thereby improving the safety of battery packs. However, the comprehensive investigation on the optimal design of battery thermal management system with liquid cooling is still rare. This article develops a comprehensive methodology to design an efficient mini-channel cooling system, which comprises thermodynamics, fluid dynamics, and structural analysis. The developed methodology mainly contains four steps: the design of the mini-channel cooling system and computational fluid dynamics analysis, the design of experiments and selection of surrogate models, formulation of optimization model, and multi-objective optimization for selection of the optimum scheme for mini-channel cooling battery thermal management system. The findings in the study display that the temperature difference decreases from 8.0878 to 7.6267 K by 5.70%, the standard temperature deviation decreases from 2.1346 to 2.1172 K by 0.82%, and the pressure drop decreases from 302.14 to 167.60 Pa by 44.53%. The developed methodology could be extended for industrial battery pack design process to enhance cooling effect thermal performance and decrease power consumption.

Temperature Distribution Optimization of an Air-Cooling Lithium-Ion Battery Pack in Electric Vehicles Based on the Response Surface Method

Electric vehicles have become a trend in recent years, and the lithium-ion battery pack provides them with high power and energy. The battery thermal system with air cooling was always used to prevent the high temperature of the battery pack to avoid cycle life reduction and safety issues of lithium-ion batteries. This work employed an easily applied optimization method to design a more efficient battery pack with lower temperature and more uniform temperature distribution. The proposed method consisted of four steps: the air-cooling system design, computational fluid dynamics code setups, selection of surrogate models, and optimization of the battery pack. The investigated battery pack contained eight prismatic cells, and the cells were discharged under normal driving conditions. It was shown that the optimized design performs a lower maximum temperature of 2.7 K reduction and a smaller temperature standard deviation of 0.3 K reduction than the original design. This methodology can also be implemented in industries where the battery pack contains more battery cells.

Computational fluid dynamics and tar formation in a low-temperature carbonization furnace for the production of carbon fibers

A three-dimensional computational fluid dynamics (CFD) model with new permeability and off-gas emission equations was developed in a four-zone low-temperature furnace (LTF) for carbon fiber carbonization. Four performance criteria (residence time, dead-volume ratio, tow temperature standard deviation, and tar formation area) were proposed to identify the optimal ratio between the two N2 flow rates introduced into the front and rear of LTF. A higher N2 flow rate at the front rather than at the rear was preferred to reduce tar formation. The tar formation area calculated from carbon activity provides useful guideline for determining optimal LTF design and operating conditions.

Novel leaf-like channels for cooling rectangular lithium ion batteries

To provide a favorable temperature for a Li-ion battery liquid cooling system, novel leaf-like channels with loops were designed as the dispersed layer. Furthermore, four collection channels along diagonal lines were established to decrease the temperature gradient, which formed a double-layer cooling channel. The effects of four structural parameters (width ratio, length ratio, bifurcation angle and channel thickness) on maximum temperature and surface standard deviation were investigated. In addition, the influence of the inlet mass flow rate was also discussed. The obtained results demonstrated that optimal maximum temperature and temperature uniformity were achieved at a width ratio of about 3/4, a length ratio close to 0.5 and a bifurcation angle in the range of 30–50°. Moreover, the thickness of the cooling channel had a strong effect on the pressure drop but only a little on the heat transfer. Increasing inlet mass flow rate can obtain the required heat dissipation capacity but at the expense of pressure drop. In summary, the synergistic effect of thickness and inlet mass flow rate can satisfy the requirements of both heat dissipation and power consumption. This optimized design can decrease the maximum temperature from 60 °C to 32 °C and the standard deviation of surface temperature from 7.1 °C to 1.4 °C. These simulation results are helpful for the design of cold plates with fractal networks.

Feasibility and safety assessment of magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU)-mediated mild hyperthermia in pelvic targets evaluated using an in vivo porcine model

Purpose: To evaluate the feasibility and assess safety parameters of magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU)-mediated hyperthermia (HT; heating to 40–45 °C) in various pelvic targets in a porcine model in vivo.Methods: Thirteen HT treatments were performed in six pigs with a commercial MRgHIFU system (Sonalleve V2, Profound Medical Inc., Mississauga, Canada) to muscle adjacent to the ventral/dorsal bladder wall and uterus to administer 42 °C (±1°) for 30 min (±5%) using an 18-mm target diameter and 100 W power. Feasibility was assessed using accuracy, uniformity, and MR-thermometry performance-based metrics. Safety parameters were assessed for tissues in the targets and beam-path by contrast-enhanced MRI, gross-pathology and histopathology.Results: Across all HT sessions, the mean difference between average temperature (Tavg) and the target temperature within the target region-of-interest (tROI, the cross-section of the heated volume at focal depth) was 0.51 ± 0.33 °C. Within the tROI, the temperature standard deviation averaged 1.55 ± 0.31 °C, the average 30-min Tavg variation was 0.80 ± 0.17 °C, and the maximum difference between Tavg and the 10th- or 90th-percentile temperature averaged 2.01 ± 0.44 °C. The average time to reach ≥41 °C and cool to ≤40 °C within the tROI at the beginning and end of treatment was 47.25 ± 27.47 s and 66.37 ± 62.68 s, respectively. Compared to unheated controls, no abnormally-perfused tissue or permanent damage was evident in the MR images, gross pathology or histological analysis.Conclusions: MRgHIFU-mediated HT is feasible and safety assessment is satisfactory for treating an array of clinically-mimicking pelvic geometries in a porcine model in vivo, implying the technique may have utility in treating pelvic targets in human patients.

Enhancement of thermal performance by converging-diverging channel in a micro tube combustor fueled by premixed hydrogen/air

As the core component of the micro thermophotovoltaic (MTPV) system, the micro combustor with a high and uniform wall temperature distribution is beneficial to improve the energy conversion efficiency. In this paper, a micro tube combustor with converging-diverging channel is proposed and the thermal performance is numerically investigated, compared with that of the micro combustor with cylindrical channel. The effects of inlet velocity of H2/air mixture, dimensionless position and diameter of throat, and solid material on the thermal performance are widely analyzed. Results show that the outer wall temperature and emitter efficiency of the micro combustor with converging-diverging channel are higher than that of the micro combustor with cylindrical channel, and the converging-diverging channel has more uniform temperature distribution. The converging-diverging micro combustor with dimensionless throat position l = 0.375 and dimensionless throat diameter β = 0.4 is more suitable for the application of MTPV system. When H2/air inlet velocity is 11 m/s and H2/air equivalence ratio is 1.0, the mean wall temperature is increased by 82.39 K and the emitter efficiency is increased by 6.59%, while the normalized temperature standard deviation is reduced by 65.85%. Additionally, the use of SiC as wall material can improve the thermal performance of the micro combustor. It is worth noting that this work will offer us significant guidelines for the optimized work of micro tube combustor.

Evaluating the Energy-Saving Potential of Solar Dedicated Ventilation Systems Based on ADRC

A solar dedicated ventilation system based on active disturbance rejection controller (ADRC) has been designed in this study and tested by experimental research to acquire better control accuracy and energy-saving potential compared with former systems. This system involves photovoltaic, solar thermal, and dedicated ventilation systems and ADRC. The solar energy replaces traditional energy to realize energy-saving potential, and ADRC takes the place of a conventional controller to gain control accuracy. The experimental results show that the temperature standard deviation is from 0.09 to 0.15 °C and difference between maximum and minimum is 0.33 to 0.49 °C (<0.5 °C) at different outdoor conditions to meet accurate control requirements. The results also show the energy-saving potential of the solar dedicated ventilation system as being equal to the power consumption of traditional systems, not including extreme situations. The solar dedicated ventilation system was used for actual operation of the cooling system of a laboratory precisely and efficiently. Consequently, the solar dedicated ventilation system based on ADRC is most suitable for hot and humid places to achieve the energy-saving objective.

Shallow-to-Deep Transition of Continental Moist Convection: Cold Pools, Surface Fluxes, and Mesoscale Organization

Abstract Large-eddy simulation is used to investigate the effects of cold pools driven by rain evaporation on the shallow-to-deep convection transition over land. The physically consistent methodologies are developed to obtain a time-dependent reference ensemble without cold pools and to apply interactive surface heat fluxes without modeling of surface energy and water budgets. Three different simulation ensembles are contrasted. The reference ensemble, in the spirit of one-dimensional single-column models, eliminates cold pools by horizontally homogenizing negative buoyancy production due to rain evaporation. The additional ensembles complement the reference cold-pool-free ensemble by including cold pools and by applying either interactive or prescribed surface fluxes. Contrasting these ensembles suggests possible improvements of convection parameterization in large-scale models of weather and climate. Without cold pools, the reference ensemble preserves key features of buoyancy-driven cellular convection associated with a field of convective plumes, as assumed in a typical convection parameterization. With cold pools, a significant enhancement of surface heat and moisture fluxes and about an hour delay of their daily maximum is simulated. Cold pools enhance near-surface temperature and moisture standard deviations as well as maxima of the near-surface updraft velocity. They also lead to the reduction of cloud lateral entrainment, deeper vertical development of the cloud layer, and a few-times-larger accumulated surface precipitation. Interactive surface fluxes provide a damping mechanism that noticeably suppresses all these effects. Perhaps surprisingly, cold pools do not significantly change the cloud-base convective mass flux that approximately follows the evolution of surface heat fluxes.

Empirical Statistical Model of Climatic Changes in the Volga Region

Climatic changes in the Volga Federal Region from 1928 to 2017 are examined. CRU data, meteorological stations, and reanalysis ERA-Interim data are used. An estimation of global factors in the variability of air temperature in the region is made. For the first time, for the VFR, an empirical-statistical model is constructed for vertical distributions (up to 64 km) of air temperature, average standard deviation of temperature, linear trend slope coefficient, and low frequency temperature component. The effect of Arctic Oscillation on temperature changes near the Earth’s surface and in the layer of 7-3 hPa in the stratosphere are evaluated.

Temperature difference relationship among precipitation, dry days, and spells in Turkey

Strong logical relationships exist between temperature difference and hydro-meteorological variables such as precipitation, dry days, and dry spells. These relationships can be used for knowing how the differences of total and top 10% heavy precipitations, dry days, and dry spells will change with respect to temperature differences? Here, daily precipitation and temperature records over Turkey are considered from 1971 to 2010, inclusive. First 30-year (1971–2000) data are used for training for temperature difference function (ΔT) and the remaining 10-year (2001–2010) is reserved for validation. The temperature difference function is validated by mean relative error, and the results are calculated for total and top 10% heavy precipitation, dry days, and spells as 14.60%, 6.14%, 2.81%, and 11.89%, respectively. The strong relationship exists between temperature difference function and standard deviation of corresponding climatic variables. Results show that standard deviation and mean relative error (MRE) have linear correlation. Also, ΔT model predictions are compared with CMIP5 RCPs projections from 2020 to 2100. The suggested model predictions fall within the range of various atmosphere-ocean global circulation (climate) model (AOGCM) scenario RCP 4.5 and RCP 8.5 projections, in addition to model predictions cross-correlation for RCP 2.6 and RCP 6.0.

Evaluation of atmospheric empirical model based on TIMED/SABER satellite temperature data

A total of 15 years of global temperature data from 2002–2016 as measured by TIMED/SABER were taken as standard to compare with those of USSA-76 and NRLMSISE-00. The accuracy of the two atmospheric models was analyzed by calculating daily mean and monthly mean temperature deviations and standard deviations of temperature deviations at different altitudes. The confidence of the model under different temperature deviations is calculated through setting the deviation between the models and the satellite observation temperature. The results show that the temperature data calculated by the two atmospheric models are in good agreement with the temperature observed by satellite. The daily mean and monthly mean accuracy of the NRLMSISE-00 are higher than those of the USSA-76. In the UMLT region, the two atmospheric models have yet to be improved to characterize the true atmosphere at the mid-high latitudes of upper mesosphere in summer and winter. The overall ability of the NRLMSISE-00 to represent the true atmosphere is superior to the USSA-76. In addition, the confidence decreases with the increase of altitude in the same latitude area and temperature deviation requirements. The confidence decreases with increasing latitude in the same altitude and temperature deviation requirements. By analyzing the differences between the atmospheric models and satellite observations. This paper provides a reference for the application of atmospheric models in engineering and provides the basis for the subsequent correction of atmospheric modes.

Impacts of Grading Rule on Urban Thermal Landscape Pattern Research

The thermodynamic landscape method is becoming a more popular approach for urban heat island research with the development of remote sensing technology. However, a limited amount of research discusses the theoretical and methodological issues of this method. This paper analyzed the reliability and stability of the results of thermal landscape pattern analysis with six different grading rules through surface temperature retrieval, landscape pattern analysis, and Geographic Information System (GIS) spatial analysis. The results demonstrate the following points. (1) The six grading methods can be categorized into two types: pixel number methods and temperature range methods. The grading results of the two kinds of methods lack comparability, whereas the grading results within one kind of method have high comparability. The temperature range methods have good consistency. The average value of the consistency indices (Si) of thermal landscape levels reaches up to 81.55%. The anomaly temperature method and standard deviation method are recommended for future research. (2) The grading rule significantly affects the stability of landscape indices, and its average variation coefficient reaches up to 22.36%. The authors suggest the use of landscape indices that have strong stability, such as shape index and landscape division index, in future research. (3) The results of the sensitivity analysis show that the change of the temperature range of thermal landscape levels affects landscape indices slightly, whereas the effect of the change of the level number of thermal landscapes on landscape indices is intense. The authors suggest categorizing the thermal landscape into six levels in future research in order to enhance the consistency and comparability among case studies.