Surface Temperature History Research Articles

熱応力評価のためのコーティングを有するパイプの外面からの内部温度変化の推定

温度変動のある高温流体にさらされるパイプの熱応力評価のため,内面の温度履歴を,パイプ外面の温度観測結果より推定する手法について検討を行った.パイプ内面がコーティングされている場合について,外面温度履歴のフーリエ変換により周波数分離し,それらの各周波数成分に対して,母材とコーティング層の振幅減少率と位相遅れを考慮することにより,外面温度履歴より内面温度履歴を推定する方法を提案した.数値シミュレーションを行った結果,温度履歴に複数の周波数成分が含まれる場合でも,推定が可能であった.計算で用いた条件の範囲では,4%程度の観測誤差が含まれていても,パイプ内面の温度履歴が良好に推定できることが明らかとなった.

30,000 Years of Ground Surface Temperature and Heat Flux Changes in Karelia Reconstructed from Borehole Temperature Data

Abstract Analyses of temperature-depth profiles logged in deep boreholes (> 1 km) permit the reconstruction of ground surface temperature (GST) and surface heat flux (SHF) histories in the period of global climate change at the border of the Pleistocene and the Holocene. We reconstructed past GST and SHF histories using data obtained from the 3.5-km-deep Onega borehole (Karelia, north-west Russia). The resulting reconstructions include information on the basal thermal regime of the Scandinavian Ice Sheet, which covered the region in the Last Glacial Maximum (LGM). The surface temperature history reveals a high amplitude of Pleistocene/ Holocene warming equal to 18-20 K. The heat flux changes precede the surface temperature changes and are close to the variations of insolation at a latitude of 60°N. A comparison of the reconstructed GST and SHF histories with the records of carbon dioxide contents in Antarctic ice cores shows that CO2 changes are much closer to temperature changes than they are to heat flux changes.

An Accurate Prediction of Surface Temperature History in a Supersonic Flight

An Accurate Prediction of Surface Temperature History in a Supersonic Flight

Optimisation of temperature observational well selection

In wellbore climatology the method of temperature inversion to determine the trends in ground surface temperature history (GSTH) assumes that the process of a well’s thermal recovery is practically completed. However, for deep wells (>100–300 m) the drilling process, due to the lengthy period of drilling fluid circulation, greatly alters the temperature of formation immediately surrounding the well. As a result, the determination of the formation temperature (with a specified absolute accuracy) at any depth requires a lengthy period of shut-in time. The objective of this study is to determine how long it takes before the error caused by mud circulation is small compared to the change arising from the change in surface temperature. In this paper we suggest two techniques, Slider’s method and utilisation of the γ-function, which enable us to estimate the rate of temperature decline and the difference between the formation and shut-in temperatures.

Recent global-warming hiatus tied to equatorial Pacific surface cooling

Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

Environmental influences on tooth growth in sperm whales from southern Australia

Long time series are a necessary tool for investigating relationships between environmental variability and population parameters in marine predators and establishing changes in these, particularly under longer-term climatic change. Multi-decadal ecological datasets are however, generally lacking, as their collection requires substantial commitment. We examined time series of growth layer group widths measured in sperm whale teeth, as indicators of energetic history, firstly to investigate commonalities in growth both within and between individuals and secondly to investigate potential relationships between tooth growth and the marine environment. Growth layer group estimates obtained from the teeth of 27 individual whales ranged 14–52 GLGs. Time series of tooth growth were highly variable both within and between individuals, reflecting differences in overall tooth structure within individuals and independence of energetic budgets among individuals. Relationships between tooth growth and broad-scale environmental variables were unclear. Spatial relationships between sea surface temperature and tooth growth histories were identified across the austral summer and corresponded to historical foraging regions in southern Australian waters. Our results demonstrate the potential for sperm whale teeth to provide extended time series of individual growth and nutritional histories. Further research is needed to understand the influence of intrinsic and extrinsic factors on tooth growth and in association, a better understanding of the responses of marine mammal species to environmental variability.

Experimental study of the effect of spray inclination on ultrafast cooling of a hot steel plate

The ultrafast cooling that occurs during high mass flux air-atomized spray impingement on a hot 6 mm thick stainless steel plate has been studied experimentally in terms of the nozzle inclination between 0° and 60°. The average mass flux of water used in the study accounts to 510 kg/m2 s. The coolants used in the study are pure water and surfactant water of 600 ppm concentration. The initial temperature of the plate has been maintained at 900 °C, which is the temperature of a hot strip on run-out table in steel industry. The transient surface heat flux and temperature histories have been estimated by an inverse heat solver using measured temperature input data. Heat transfer results demonstrates that optimum cooling efficiency (~2.76 MW/m2, 194 °C/s) for pure water has been achieved at 30° nozzle orientation. The inclined nozzle has not been found beneficial when surfactant water is used as the coolant.

A new analytical solution for assessing climate change impacts on subsurface temperature

AbstractGroundwater temperature is an important water quality parameter that affects species distributions in subsurface and surface environments. To investigate the response of subsurface temperature to atmospheric climate change, an analytical solution is derived for a one‐dimensional, transient conduction–advection equation and verified with numerical methods using the finite element code SUTRA. The solution can be directly applied to forward model the impact of future climate change on subsurface temperature profiles or inversely applied to produce a surface temperature history from measured borehole profiles. The initial conditions are represented using superimposed linear and exponential functions, and the boundary condition is expressed as an exponential function. This solution expands on a classic solution in which the initial and boundary conditions were restricted to linear functions. The exponential functions allow more flexibility in matching climate model projections (boundary conditions) and measured temperature–depth profiles (initial conditions). For example, measured borehole temperature data from the Sendai Plain and Tokyo, Japan, were used to demonstrate the improved accuracy of the exponential function for replicating temperature–depth profiles. Also, the improved accuracy of the exponential boundary condition was demonstrated using air temperature anomaly data from the Intergovernmental Panel on Climate Change. These air temperature anomalies were then used to forward model the effect of surficial thermal perturbations in subsurface environments with significant groundwater flow. The simulation results indicate that recharge can accelerate shallow subsurface warming, whereas upward groundwater discharge can enhance deeper subsurface warming. Additionally, the simulation results demonstrate that future groundwater temperatures obtained from the proposed analytical solution can deviate significantly from those produced with the classic solution. Copyright © 2013 John Wiley & Sons, Ltd.

Achievement of ultrafast cooling rate in a hot steel plate by air-atomized spray with different surfactant additives

Ultrafast cooling of a 6mm thick hot stainless steel plate (AISI 304) has been achieved by high flow conditions of air and water, which is needed at the runout table of a hot strip mill to develop advanced high strength steels. The present study primarily focuses on the effect of adding different types of surfactants at various concentration levels to air atomized water spray for enhancement of ultrafast cooling rate. The anionic, cationic and non-ionic surfactants used have been characterized by measuring their surface tension, contact angle and viscosity. The surfactant enhanced heat transfer experiments have been conducted with a full cone atomizer at a fixed nozzle to surface distance using constant air and water flow rates optimized earlier. The initial surface temperature of the test plate has been maintained at 900°C in each case. The experimental measurements have been applied to a commercial inverse heat conduction solver (INTEMP) to estimate local surface heat flux as well as surface temperature histories. The concentration of all the surfactants has been optimized based on the highest cooling rate. Depending on their spreadability, wetting characteristics and ability to foam formation, the cationic and non-ionic surfactants are found to produce better cooling effects than the anionic surfactant. These enhanced ultrafast cooling rates can be useful to produce advanced high strength steels in the steel industries.

Analytical Solution for Transient Thermal Response of an Insulated Structure

An analytical solution was derived for the transient response of an insulated aerospace vehicle structure subjected to a simplified heat pulse. This simplified problem approximates the thermal response of a thermal protection system of an atmospheric entry vehicle. The exact analytical solution is solely a function of two nondimensional parameters. A simpler function of these two parameters was developed to approximate the maximum structural temperature over a wide range of parameter values. Techniques were developed to choose constant, effective properties to represent the relevant temperature and pressure-dependent properties for the insulator and structure. A technique was also developed to map a time-varying surface temperature history to an equivalent square heat pulse. Using these techniques, the maximum structural temperature rise was calculated using the analytical solutions and shown to typically agree with finite element simulations within 10–20% over the relevant range of parameters studied.

Conjugate heat transfer analysis in high speed flows

Conjugate heat transfer studies are presented for high speed aerospace vehicle using commercial CFD software. Navier Stokes equations in the fluid domain and transient heat conduction equations in the solid domain are solved simultaneously to obtain the skin temperature history and other flow parameters. The computational methodology is applied to predict the surface temperature of high speed aerospace vehicle after validating the methodology against experimental results. Validation cases include laminar flow past axisymmetric double cone at Mach 4.57 and turbulent flow past circular cylinder at Mach 6.7. Computed flow field including cold wall heat flux, surface temperature distribution, surface temperature history match nicely with experimental as well as other numerical results. Temperature dependent material properties are found to have significant effect on the surface temperature prediction. Computed surface temperature of a high speed aerospace vehicle show good overall match with flight measured v...

RECOVERY FROM THE LITTLE ICE AGE: GEOTHERMAL EVIDENCES

We applied geothermal method for paleoclimatic reconstruction of the ground surface temperature history during the Little Ice Age and contemporary warming. We analyzed 83 borehole temperature profiles and estimated warming amplitudes and warming start dates after the Little Ice Age. The studied boreholes are situated in the Urals and Eastern Europe (Finland, Ukraine, and Belarus). Our investigation shows high degree of spatial variability of climatic changes in 18–19 centuries. Spatial distribution of amplitudes of paleoclimatic changes and warming start date testifies that warming following after the Little Ice Age was in progress in several steps and for different regions it started at different times.

Transient heat flux deduction for a slab of finite thickness using surface temperature measurements

Heat flux at a wall can be derived from time resolved measurements of the surface temperature. Current methods, which do not use temperature gradient measurements, obtain the heat flux by solving the heat equation in a wall of infinite thickness with the temperature input as a time-dependent boundary condition. The presumption of an infinite thickness and the use of these algorithm severely restricts the validity of the solution. In this paper we propose an analytical solution for a slab of finite thickness, we refer to our new algorithm as the slab model. If the opposite surface can be assumed to be ideally insulated and the properties of the wall are not temperature dependent, the heat flux can be determined solely by the surface temperature history. The slab model is derived from the Fourier equation and a method for its implementation is proposed. This algorithm is compared to the Cook–Felderman algorithm (CF), which assumes the semi-infinite medium condition. The possible error, the algorithm dependencies, as well as the noise rejection performance of the slab model are discussed.

Past climate changes and permafrost depth at the Lake El'gygytgyn site: implications from data and thermal modeling

Abstract. This study focuses on the temperature field observed in boreholes drilled as part of interdisciplinary scientific campaign targeting the El'gygytgyn Crater Lake in NE Russia. Temperature data are available from two sites: the lake borehole 5011-1 located near the center of the lake reaching 400 m depth, and the land borehole 5011-3 at the rim of the lake, with a depth of 140 m. Constraints on permafrost depth and past climate changes are derived from numerical simulation of the thermal regime associated with the lake-related talik structure. The thermal properties of the subsurface needed for these simulations are based on laboratory measurements of representative cores from the quaternary sediments and the underlying impact-affected rock, complemented by further information from geophysical logs and data from published literature. The temperature observations in the lake borehole 5011-1 are dominated by thermal perturbations related to the drilling process, and thus only give reliable values for the lowermost value in the borehole. Undisturbed temperature data recorded over more than two years are available in the 140 m deep land-based borehole 5011-3. The analysis of these observations allows determination of not only the recent mean annual ground surface temperature, but also the ground surface temperature history, though with large uncertainties. Although the depth of this borehole is by far too insufficient for a complete reconstruction of past temperatures back to the Last Glacial Maximum, it still affects the thermal regime, and thus permafrost depth. This effect is constrained by numerical modeling: assuming that the lake borehole observations are hardly influenced by the past changes in surface air temperature, an estimate of steady-state conditions is possible, leading to a meaningful value of 14 ± 5 K for the post-glacial warming. The strong curvature of the temperature data in shallower depths around 60 m can be explained by a comparatively large amplitude of the Little Ice Age (up to 4 K), with low temperatures prevailing far into the 20th century. Other mechanisms, like varying porosity, may also have an influence on the temperature profile, however, our modeling studies imply a major contribution from recent climate changes.

Nanoparticle agglomeration in an evaporating levitated droplet for different acoustic amplitudes

Radiatively heated levitated functional droplets with nanosilica suspensions exhibit three distinct stages namely pure evaporation, agglomeration, and finally structure formation. The temporal history of the droplet surface temperature shows two inflection points. One inflection point corresponds to a local maximum and demarcates the end of transient heating of the droplet and domination of vaporization. The second inflection point is a local minimum and indicates slowing down of the evaporation rate due to surface accumulation of nanoparticles. Morphology and final precipitation structures of levitated droplets are due to competing mechanisms of particle agglomeration, evaporation, and shape deformation. In this work, we provide a detailed analysis for each process and propose two important timescales for evaporation and agglomeration that determine the final diameter of the structure formed. It is seen that both agglomeration and evaporation timescales are similar functions of acoustic amplitude (sound pressure level), droplet size, viscosity, and density. However, we show that while the agglomeration timescale decreases with initial particle concentration, the evaporation timescale shows the opposite trend. The final normalized diameter can be shown to be dependent solely on the ratio of agglomeration to evaporation timescales for all concentrations and acoustic amplitudes. The structures also exhibit various aspect ratios (bowls, rings, spheroids) which depend on the ratio of the deformation timescale (tdef) and the agglomeration timescale (tg). For tdef<tg, a sharp peak in aspect ratio is seen at low concentrations of nanosilica which separates high aspect ratio structures like rings from the low aspect ratio structures like bowls and spheroids.

RECOVERY FROM THE LITTLE ICE AGE: GEOTHERMAL EVIDENCES

We applied geothermal method for paleoclimatic reconstruction of the ground surface temperature history during the Little Ice Age and contemporary warming. We analyzed 83 borehole temperature profiles and estimated warming amplitudes and warming start dates after the Little Ice Age. The studied boreholes are situated in the Urals and Eastern Europe (Finland, Ukraine, and Belarus). Our investigation shows high degree of spatial variability of climatic changes in 18–19 centuries. Spatial distribution of amplitudes of paleoclimatic changes and warming start date testifies that warming following after the Little Ice Age was in progress in several steps and for different regions it started at different times.

The study of the climate in the past and the climate change in mainland portugal using geothermal data has started in 199

The study of the climate in the past and the climate change in mainland portugal using geothermal data has started in 199. Reconstruction of ground surface temperature (GST) history from temperature logs measured in a 200 m deep borehole located 5 km away from the town of évora in portugal, indicates a warming of 1K since the second half of the nineteenth century to the middle of the 90s of the twentieth century, increasing considerably in the last 10 years. Results of the reconstruction (based on a functional space inversion – FSI – method) are compared with air temperatures recorded at the lisbon meteorological station since 185. The air temperature time series display a warming trend with the amplitude about 1K for the same period. The coupling of the air and ground temperature changes and their downward propagation by heat conduction was confirmed by repeated logging in November 2003, .7 years after obtaining the first temperature log. The method can be used in paleoclimatic studies in Antarctica as well as in areas with permafrost.

Reconstruction of remote climate change from borehole temperature measurement in the eastern part of Morocco

Data from temperature measurements in boreholes are indicators of the temperature variations associated with past climate change. This paper is a contribution to reconstruct the ground surface temperature history (GSTH) from geothermal data in the eastern part of Morocco. From a set of several temperature logs, measured in the study area, only two were found suitable for estimating the ground surface temperature history (GSTH). In order to reconstruct the surface temperature past changes the functional space inversion method (FSI) was used. The inversion reveals a recent warming in the last century with respective amplitude of 0.1 °C and 1 °C for the boreholes 2952 in Oujda and 1624 in Berkane. These results can be confirmed by the air temperature record of the meteorical station in Oujda despite the scarceness of data beyond 1959.

Determination of Time Resolved Heat Transfer Coefficient and Adiabatic Effectiveness Waveforms With Unsteady Film

Traditional hot gas path film cooling characterization involves the use of wind tunnel models to measure the spatial adiabatic effectiveness (η) and heat transfer coefficient (h) distributions. Periodic unsteadiness in the flow, however, causes fluctuations in both η and h. In this paper we present a novel inverse heat transfer methodology that may be used to approximate the η(t) and h(t) waveforms. The technique is a modification of the traditional transient heat transfer technique that, with steady flow conditions only, allows the determination of η and h from a single experiment by measuring the surface temperature history as the material changes temperature after sudden immersion in the flow. However, unlike the traditional transient technique, this new algorithm contains no assumption of steadiness in the formulation of the governing differential equations for heat transfer into a semi-infinite slab. The technique was tested by devising arbitrary waveforms for η and h at a point on a film cooled surface and running a computational simulation of an actual experimental model experiencing those flow conditions. The surface temperature history was corrupted with random noise to simulate actual surface temperature measurements and then fed into an algorithm developed here that successfully and consistently approximated the η(t) and h(t) waveforms.

Coupled continental and sea surface temperature history of southeast Africa (Zambezi River region) since Marine Isotope Stage 3

Coupled continental and sea surface temperature history of southeast Africa (Zambezi River region) since Marine Isotope Stage 3