Internal Temperature Variations Research Articles

Overcharge failure investigation of lithium-ion batteries

Safety behaviors of a 32Ah prismatic lithium-ion battery are investigated under abusive charge conditions by monitoring the internal and external cell temperature variation. Results show that the cell internal temperature can reach 235°C before firing, which is almost 140°C higher than the cell external temperature. Although the cell resistance increases abruptly due to electrolyte oxidization when the cell is firstly overcharged to its maximum voltage (5.10V), the cell internal temperature keeps a low temperature of 50°C without notable temperature rise. However, the cathode/electrolyte interface becomes highly reactive as the cell is further overcharged. Cell internal temperature goes up to more than 200°C accompanied with massively gas production when the cell is overcharged to 180% SoC. Post-overcharge analysis on both cathode and anode indicates that lithium plating during overcharge is the major cause responsible for thermal runaway because the observed cell temperature is well above the melting point of lithium metal.

Two and Three-Dimensional Analysis Comparison of Nozzles due to Internal Pressure, Thermal Load and External Load

본 논문에서는 원통형 쉘에 부착된 노즐의 구조 건전성평가를 수행하고 그 결과를 비교하기 위해 2차원(2D)과 3차원(3D) 해석이 수행되었다. 현재 원자력 발전소에서 사용되는 3개의 노즐을 구조 건전성평가를 위해 선정하였고, 각각 노즐은 내부압력, 온도변화 및 외부하중을 받는다. 내부압력에 대한 2D 해석은 1.5이상의 계수 값을 이용하거나 응력집중 계수를 적용하여야 하고, 온도변화에 대한 2D와 3D 해석결과는 피복재의 유무와 상관없이 서로 거의 비슷하며, 외부하중에 대한 WRC Bulletin 297에 의한 해석결과는 3D 해석결과보다 더 보수적임을 확인할 수 있었다.In this paper, the two-dimensional(2D) and three-dimensional(3D) analyses have been performed in order to evaluate the structural integrities and compare 2D and 3D results for nozzles attached to cylindrical shells. Three nozzles, which are currently used in the nuclear power plant, are chosen to evaluate the structural integrities, and each nozzle is subjected to internal pressure, temperature variation and external loads. It is found that the 2D analysis for internal pressure should be performed with a factor of more than 1.5 or a stress concentration factor; 2D and 3D analysis results for temperature variation are almost similar to each other regardless of cladding; and the analysis results for external loads by WRC Bulletin 297 are more conservative than the 3D analysis results.

A novel fibre Bragg grating sensor packaging design for ultra-high temperature sensing in harsh environments

The aim of this article is to introduce a novel packaging of conventional Corning SMF-28™ single-mode fibre Bragg grating sensors for ultra-high temperature sensing. The package is in a cylindrical shape made of yttria-stabilized zirconia tubes. The fibre optic sensor is epoxied to one end inside the tube to be protected from high external temperatures and also harsh environments. Highly-oriented pyrolytic graphite tube with an exceptional anisotropic thermal conductivity with higher conductivity in transverse than radial direction is positioned around the fibre to protect it from high temperatures. Air cooling system is also provided from the other end to dissipate the transferred heat from inside the tube. The shift in the Bragg wavelength is influenced by the thermal expansion of the package and internal temperature variations, which translates into thermal expansion of the fibre. The modelling and experimental results revealed that the Bragg wavelength shift increases to 1.4 pm °C−1 at higher temperatures with linear behaviour at temperatures above 600 °C. The finite element modelling and the experimental results are also in good proximity indicating the similar trend for the shift in the Bragg wavelength.

Experimental investigation of a novel phase change cold storage used for a solar air-conditioning system

Solar energy systems in combination with thermal driven sorption chillers for air conditioning are gaining increasing attention. Since solar energy is available only during daytime and solar cooling systems are usually intermittent and susceptible to the weather, applying cold storage methods to solar air-conditioning systems is favorable to utilize renewable energy and enhance the system stability. A self-developed phase change material (PCM) providing a suitable phase change temperature of 14.97°C and a reasonable phase transition latent heat of 115.1 kJ/kg is used to fabricate a cold storage tank. The aim of this article is to experimentally investigate the performance of the cold storage tank for solar air-conditioning application. The experiment includes a small-scale steady-state testing of a single spherical capsule and a solar air-conditioning system integrated with the PCM cold storage tank. The temperature distribution and phase change interface movement of the capsule are theoretically predicted. Main parameters of the cold storage tank, namely the inlet and outlet water temperature, internal temperature variation of capsules, charging/discharging capacity and charging/discharging rate are analyzed. The experimental results show that the charging and discharging process completed in 230 min and 220 min under steady states. While under unsteady states of a solar air-conditioning system, the charging and discharging process of the phase change cold storage tank completed within 320 min and 110 min with the total amount of charging and discharging capacity of 1016.1 kJ and 942.8 kJ, respectively. The phase change cold storage tank manifests good feasibility and stability for solar air-conditioning application.

Temperature modulation of the vibrational responses of a flexible fluid-conveying pipe

AbstractIn this study, the nonlinear transverse vibration of a flexible pipe conveying hot, pressurized fluid is investigated. The pipe which is subjected to a pinned-pinned end condition extends as a result of several operating variables such as internal fluid temperature variation, pre-stress and internal pressurization. The equation of motion is solved analytically by hybrid Fourier-Laplace transforms, and the effects of inlet temperature, temperature gradient, and coefficient of area deformation are investigated on the natural frequencies and transverse dynamic response of the pipeline. While the inlet temperature and temperature gradient are found to be inversely proportional to the natural frequencies and amplitude of the dynamic response, increase in the coefficient of area deformation has little effect on the natural frequencies for the particular case considered.

Diffuse near-infrared reflectance spectroscopy during heatstroke in a mouse model: pilot study

Heatstroke, a form of hyperthermia, is a life-threatening condition characterized by an elevated core body temperature that rises above 40°C (104°F) and central nervous system dysfunction that results in delirium, convulsions, or coma. Without emergency treatment, the victim lapses into a coma and death soon follows. The study presented was conducted with a diffuse reflectance spectroscopy (DRS) setup to assess the effects of brain dysfunction that occurred during heatstroke in mice model (n=6). It was hypothesized that DRS can be utilized in small animal studies to monitor change in internal brain tissue temperature during heatstroke injury since it induces a sequence of pathologic changes that change the tissue composition and structure. Heatstroke was induced by exposure of the mice body under general anesthesia, to a high ambient temperature. A type of DRS in which the brain tissue was illuminated through the intact scalp with a broadband light source and diffuse reflected spectra was employed, taking in the spectral region between 650 and 1000 nm and acquired at an angle of 90 deg at a position on the scalp ∼12 mm from the illumination site. The temperature at the onset of the experiment was ∼34°C (rectal temperature) with increasing intervals of 1°C until mouse death. The increase in temperature caused optical scattering signal changes consistent with a structural alteration of brain tissue, ultimately resulting in death. We have found that the peak absorbance intensity and its second derivative at specific wavelengths correlate well with temperature with an exponential dependence. Based on these findings, in order to estimate the influence of temperature on the internal brain tissue a reflectance-temperature index was established and was seen to correlate as well with measured temperature. Overall, results indicate variations in neural tissue properties during heatstroke and the feasibility to monitor and assess internal temperature variations using DRS. Although several approaches have described the rise in temperature and its impact on tissue, to the best of our knowledge no information is available describing the ability to monitor temperature during heatstroke with DRS. The motivation of this study was to successfully describe this ability.

Temperature Measurement and Data Analysis of the Roller Compected Concrete Dam

Prototype observation of the concrete dam is an important and effective measure to master the operating condition of dams. Analysis of changes of concrete temperature for dams is the basis of studying the safety of dam operation. By analyzing the raw monitoring data of temperature of a RCC dam, this paper researches the changing process of concrete temperature and internal concrete partitions temperature variation of dams. It also draws the temperature field of the dam concrete. The results show that the isothermals of downstream side parallel with the surface of the downstream dam, and the isothermals of upstream side intersect with the dam. Isothermals which are near to the dam’s surface are close. This suggests that temperature gradient there is large. There is a high temperature nucleus and two low temperature nucleuses in the temperature field of the dam in summer, while in winter there is only one high temperature nucleus. So it suggests that the temperature field in summer is more complex.

An active pipe-embedded building envelope for utilizing low-grade energy sources

An active pipe-embedded building envelope, which is an external wall or roof with pipes embedded inside, was presented. This structure may utilize the circulating water in the pipe to transfer heat or coolth inside directly. This kind of structure is named “active pipe-embedded building envelope” due to dealing with the thermal energy actively inside the structure mass by circulating water. This structure not only deals with thermal energy before the external disturbance becomes cooling/heating load by using the circulating water, but also may use low-grade energy sources such as evaporative cooling, solar energy, and geothermal energy. In the meantime, this structure can also improve the indoor thermal comfort by tempering the internal wall surface temperature variation due to the thermal removal in the mass. This work further presents the thermal performance of this structure under a typical hot summer weather condition by comparing it with that of the conventional external wall/roof with numerical simulation. The results show that this pipe-embedded structure may reduce the external heat transfer significantly and reduce the internal wall surface temperature for improving thermal comfort. This work also presents the effects of the water temperature and the pipe spacing on the heat transfer of this structure. The internal surface heat transfer may reduce by about 2.6 W/m2 when the water temperature reduces by 1 °C as far as a brick wall with pipes embedded inside is concerned. When the pipe spacing reduces by 50 mm, the internal wall surface heat flux can also reduce by about 2.3 W/m2.

Simulation of the internal temperature in the Passol Laboratory, University of Debrecen

Abstract Nowadays the facades of newly built buildings have significant glazed surfaces. The solar gains in these buildings can produce discomfort caused by direct solar radiation on the one hand and by the higher indoor air temperature on the other hand. The amplitude of the indoor air temperature variation depends on the glazed area, orientation of the facade and heat storage capacity of the building. This paper presents the results of a simulation, which were made in the Passol Laboratory of University of Debrecen in order to define the internal temperature variation. The simulation proved that the highest amplitudes of the internal temperature are obtained for East orientation of the facade. The upper acceptable limit of the internal air temperature is exceeded for each analyzed orientation: North, South, East, West. Comparing different building structures, according to the obtained results, in case of the heavy structure more cooling hours are obtained, but the energy consumption for cooling is lower.

Analysis method of thermal dam deformation

Based on the internal temperature variation of a dam lagging behind the ambient temperature variation, the ambient temperature of continuous variation is disctetized, and the functional expression of the thermal displacement component of the dam caused by single instantaneous temperature variation is obtained. Considering the temporal and spatial distribution law of the ambient temperature and its relation with air and water temperature, the function is expanded into a Taylor series. As a result, the improved thermal displacement component expression for a dam monitoring model is obtained.

Elastoplastic stress–strain analysis of buried steel pipelines subjected to fault displacements with account for service loads

This paper presents an analytical model for stress–strain analysis of buried steel pipelines subjected to active fault displacements, accounting for internal pressure and temperature variation Δ T (a difference between the operational temperature and the temperature of pipelay). Along with the longitudinal stresses and strains arising from combined bending and tension due to fault displacements, additional hoop and axial stresses and strains resulting from the internal pressure and temperature variation are taken into account within a two-dimensional elastoplastic model based on the plastic flow theory. The interaction of the pipeline with the surrounding soil is modeled in axial and transverse directions using bilinear soil springs. The analysis is performed iteratively as a series of elastic solutions using a secant modulus of the pipe steel. The validation of the proposed model is performed through comparison of the obtained solutions to the results of numerical simulations of the finite-element beam-type and shell-type models in the finite-element software ANSYS 12.1. It is shown that incorporating the two-dimensional elastoplastic approach within the analytical structural model of pipeline at active fault crossings provides good correspondence to the numerical results obtained with the finite-element model for various service conditions and a range of fault intersection angles.

Thermal model for performance prediction of integrated collector storage systems

The result of many years of global research on solar water heating systems has outlined the promising approach of integrated collector storage solar water heaters (ICS-SWHs) in cold climates. This research paper aims to model the field performance of a newly developed ICS-SWH for Scottish weather conditions. Field experiments were performed to investigate the performance of the newly developed ICS-SWH and the parameters affecting it. This was followed by developing a thermal macromodel able to compare the internal temperature variation under differing external weather conditions in order to evaluate the transient performance of the ICS-SWH for field conditions. Through this work, important parameters for modeling field performance of ICS-SWH were established. The innovative modeling tool developed was found to accurately predict the bulk water temperature of the ICS-SWH for any orientation and location in the world with good accuracy.

Determination of the dynamics of temperature variation in a model object by acoustic thermography

An experiment on monitoring the dynamics of internal temperature variation in a model object by the acoustic thermography method is carried out. The measurements were performed in a cell filled with an aqueous solution of glycerol, into which a plasticine object was placed. Thermal acoustic radiation of the object was measured in the course of its heating and cooling. Two bars of acoustic thermometers positioned on two sides of the object were used for this purpose. The results of measurements allowed the reconstruction of the dynamics of the varying two-dimensional distribution of in-depth temperature. The position of the heated region, its temperature, and its characteristic size are estimated. In addition, an estimate is obtained for the absorption coefficient.

Image generation in chirp pulse microwave computed tomography (CP‐MCT) by numerical computation: Computation of a human head model

AbstractThis paper considers chirp pulse microwave CT (CP‐MCT), in which the chirp pulse and signal processing technology are used to estimate the internal structure and temperature variation of biological objects. A method is developed in which the CT image to be acquired by actual measurement can be derived by numerical computation. The aftereffect function between the transmitting and receiving antennas is calculated by a Gaussian pulse and the FDTD method. After convolution of the function with the input chirp pulse signal on the time axis, the measured signal at a point is constructed by the same signal processing as in real measurement. This computation is repeated for each point on the translation‐scanning axis. The projection data are acquired and the CT image is generated. The validity of this computation procedure, which is called the aftereffect function method, is demonstrated by comparing the resolution and the measured temperature variation in actual measurements with the results of a simulation computation. Using the aftereffect function method, the point‐spread function of an imaging system which is difficult to measure, can be derived. An analytical model for the human head is constructed. Simulations are performed for the attenuation distribution and the temperature variation distribution. Based on the results, the feasibility of the biological imaging by CP‐MCT is discussed. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 88(9): 53–63, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20190

Internal and forced climate variability during the last millennium: a model-data comparison using ensemble simulations

A three-dimensional climate model was used to perform 25 simulations over the last millennium, which are driven by the main natural and anthropogenic forcing. The results are compared to available reconstructions in order to evaluate the relative contribution of internal and forced variability during this period. At hemispheric and nearly hemispheric scale, the impact of the forcing is clear in all the simulations and knowing the forced response provides already a large amount of information about the behaviour of the climate system. Besides, at regional and local scales, the forcing has only a weak contribution to the simulated variability compared to internal variability. This result could be used to refine our conception of Medieval Warm Period and Little Ice Age (MWP and LIA). They were hemispheric-scale phenomena, since the temperature averaged over the Northern Hemisphere was, respectively generally higher/lower during those periods because of a stronger/weaker external forcing at that time. Nevertheless, at local-scale, the sign of the internal temperature variations determines to what extent the forced response will be actually visible or even masked by internal noise. Because of this role of internal variability, synchronous peak temperatures during the MWP or LIA between different locations are unlikely.

Experimental development of an intelligent refrigeration system

In this study, an alternative solution to reduce energy consumption in industrial refrigeration systems is proposed and introduced. A typical industrial refrigeration system was conceived, built and modified in the laboratory, receiving a novel power law control system, which utilizes a frequency inverter. The operation and energy consumption of the system operating either with the new control system or with the traditional on–off control were compared to realistically quantify the obtained gains. In this manner, the measured temperature data acquired from several points of both systems and the energy consumption in kW h during a 24 h experimental run period are compared. The closed-loop power law controlled system shows a much smaller variation of the cold chamber internal temperature and electrical energy consumption economy of 35.24% in comparison with the traditional on–off system, under the same operating conditions.

Forced-air Cooling Packaged Blueberries

Harvested blueberries, packaged in plastic covered 0.47-L (1-pt) fiber cups, arranged 12 cups to a corrugated master and palletized (96 masters to a pallet) were cooled with forced-air pulled horizontally through the stack. Air flow rates varied from 0.0011 to 0.0022 m3/s/kg (1.06 to 2.12 cfm/lb) of fruit. The variations in cooling rates are discussed in terms of time required to reduce the temperature one-half the difference between the starting pulp temperature and the room air temperature. Average cooling half-times ranged from 48 to 65 min for forced-air cooled fruit. The variations were attributed to differences in the air flow rate. With forced-air cooling, the differences in cooling rates at various points inside the pallet were generally small. For comparison, similar pallets were room cooled at the same time and location. The average half cooling time near the center of the pallet of room-cooled fruit was projected to be over 12 h. Average half cooling times for fruit near the outside of the pallet was approximately 6 h, indicating significant internal temperature variations. The results of this study suggest that the application of forced-air cooling can significantly reduce cooling times of packaged and palletized blueberries and provide more uniform temperatures within the pallet.

Binary mixtures: Onset of Dufour driven convection.

The onset of convection in binary mixtures enclosed between two horizontal, isothermal boundaries and driven by an externally applied vertical concentration gradient is investigated. It is shown that internal temperature variations, which are driven by the Dufour effect, can have significant influence on the stability boundaries of the quiescent state, depending on the strength of the Dufour coupling.

A simplified thermal response model

The observed dynamic thermal response of intermittently occupied buildings can usually be described by one or two time constants. This suggests that much of the complexity in detailed computer thermal response models may not always be necessary. Simplified thermal response models may be adequate for many purposes, and ought to have cost advantages, both in setting up and run time. The paper describes the basis of a simplified microcomputer model of building thermal response. Model predictions of internal temperature variation in a working school are shown to agree well with observations. The model is intended for professional use and user interface is being developed in consultation with an architectural practice.

Predictions of the heating and cooling energy requirements in buildings using the degree hours method

Abstract Methods for the prediction of seasonal energy requirements for heating or cooling buildings are briefly discussed, and a new method, the degree hours method, is described. This method requires the simulation of the pattern of internal temperature variations in a passive building over a season in response to exposure to the weather conditions. The seasonal heating or cooling energy requirement can then be calculated in relation to any chosen base temperature. Different base temperatures can be chosen for summer cooling and for winter heating, to allow for comfort requirements and casual heat gains. Predictions using this method are compared with results from an alternative published method, for an example building.