Maximum Temperature Distribution Research Articles

The Maximum Temperature Distribution and Improvement Plan of Protected Horticulture Planning Area in Saemanguem Using CFD Simulation

The Maximum Temperature Distribution and Improvement Plan of Protected Horticulture Planning Area in Saemanguem Using CFD Simulation

STEAD: a high-resolution daily gridded temperature dataset for Spain

Abstract. Using 5520 observatories covering the whole territory of Spain (about 1 station per 90 km2 considering the whole period), a daily gridded maximum and minimum temperature was built covering a period from 1901 to 2014 in peninsular Spain and 1971 to 2014 in the Balearic and Canary Islands. A comprehensive quality control was applied to the original data, and the gaps were filled on each day and location independently. Using the filled data series, a grid of 5 km × 5 km spatial resolution was created by estimating daily temperatures and their corresponding uncertainties at each grid point. Four daily temperature indices were calculated to describe the spatial distribution of absolute maximum and minimum temperature, number of frost days and number of summer days in Spain. The southern plateau showed the maximum values of maximum absolute temperature and summer days, while the minimum absolute temperature and frost days reached their maximums at the northern plateau. The use of all the available information, the complete quality control and the high spatial resolution of the grid allowed for an accurate estimate of temperature that represents a precise spatial and temporal distribution of daily temperatures in Spain. The STEAD dataset is publicly available at https://doi.org/10.20350/digitalCSIC/8622 and can be cited as Serrano-Notivoli et al. (2019).

Effect of microchannel heat sink configuration on the thermal performance and pumping power

This paper presents a computational modeling of ten different configurations of microchannel heat sink (MCHS) with single phase liquid flow in order to compare their performance with the conventional MCHS. New configurations with a longitudinal and transverse arrangement of microchannels relative to the base plate, different number of coolant passages, cocurrent and countercurrent coolant supply were studied to obtain maximum thermal performance and uniform temperature distribution. The formation of the developing flow zones in a number of new configurations allowed to achieve higher Nusselt numbers and low thermal resistances at the same pumping power in comparison with conventional MCHS. The proposed methods of coolant supply make it possible to reduce the temperature gradients and improve the temperature uniformity on the base due to better distribution of coolant.

A Multi-Scale Analysis of the Fire Problems in an Urban Utility Tunnel

Building utility tunnels has been widely adopted as an important solution for the sustainable development of cities, but their unique fire problems have not attracted enough attention to date. With the purpose of preliminarily understanding the fire phenomena in a utility tunnel, this study performed a comprehensive analysis, including the burning behaviour of accommodated cables, hot gas temperature field and enhanced fuel burning rates based on bench-scale, full-scale and model-scale fire tests. The critical exposed radiative heat flux for the 10-kV power cable to achieve complete burning was identified. The whole burning process was divided into five phases. The cable’s noteworthy hazards and dangerous fire behaviours were also examined. The two-dimensional (2D) gas temperature fields and longitudinal maximum temperature distributions were investigated carefully, after which a versatile model was derived. The model predicted the maximum temperature attenuation of both upstream and downstream flows reasonably well. Finally, the phenomenon of enhanced fuel burning was explored. A multivariate cubic function that considers the global effects of relative width, height and distance was further proposed to estimate the enhancement coefficient. The current findings can provide designers and operators with valuable guidance for the integrated promotion of utility tunnels’ fire safety level.

Heat transfer analysis of magnesium alloy plate during transport process

Abstract Temperature detection and tracking of AZ31B magnesium alloy plate during the air-cooling transport process were investigated and carried out under different thicknesses and initial temperatures. Experimental results show that there exists a sudden temperature drop in the range of 1/4 of width distanced from the edge. When the plate is cooled by 25–56 °C, the maximum inhomogeneous temperature distribution under all process conditions will appear in width direction. For the air-cooling transport process, the temperature control model for predicting the average temperature of the Mg plate after a predetermined time period can be established by modifying the Stefan-Boltzmann empirical equation. The model mainly depends on the plate specifications and air-cooling time.

Design and Enhancement of Thermal Flow Characteristic in an Annular Diffuser under Turbulent Flow

The annular diffuser is an expansion area, which, despite its simple structure, is very important in some engineering and thermal applications. In the present research, numerical simulations were performed to investigate the temperature field and flow structure characteristics in an annular diffuser. The hub of the annular diffuser consisted of a straight semi-dimpled tube SSDT. Three different diffuser wall angles (α) 1.8°, 3.6° and 5.4° with inlet Reynolds number 1.5 × 104 were studied in details with air as a working fluid. The computational fluid dynamics CFD was used to simulate the model in a turbulent flow. The standard k-ε turbulence model was used to complete the governing equations. The numerical results, mainly the temperature distribution, pressure drop and velocity distribution for the airflow in the annular diffuser fitted with SSDT for different diffuser wall angles α were obtained and compared. It was observed that as the wall diffuser angle α increases, the enhancement of the temperature distribution and the velocity distribution decrease while the pressure drop rate increases. The maximum temperature distribution and velocity distribution were completed by diffuser wall angle α1 = 1.8° whereas, the highest pressure drop achieved by diffuser wall angle α3 = 5.4°.

Regionalization of Ukraine based on the influence of extreme values of maximum air temperature during warm and cold periods of the year

Based on the data of maximum daily near-surface air temperature (MSAT) taken from 186 meteorological stations of Ukraine the parameters of extremality with relation to maximum air temperature for different time periods as well as deviations between them during cold and warm periods of the year were calculated. Regionalization of Ukraine was carried out in order to identify climate-vulnerable regions by means of comparison, overlapping and match of the areas with the highest values towards selected extremality thresholds. The conclusion about general increase in extremality over the last decade with relation to a climatic standard is made, the areas with the greatest vulnerability are outlined, and the areas with increase in extremality degree are identified. During both periods of the year certain areas in the southern, central and eastern parts of Ukraine are considered, based on maximum air temperature data, as the most vulnerable ones. During both periods of the year over 2001-2010, as compared to 1991-2000, increase of recurrence of extreme values of average maximum of air temperature was observed: in March and December during the cold period and also from May to July, and in case of EHMP event – in August.
 Distribution of maximum air temperature of the EHMP category, in comparison to the category of extreme values, specifies and localizes the regions with the greatest vulnerability. The areas of the highest vulnerability during the cool period comprise the extreme west, south-western and southern regions and during the warm period – southern, south-eastern regions and the extreme east of Ukraine. The spatial distribution of the extreme values of the MSAT for the warm period has a predominantly meridional orientation.
 During both periods of the year regions in the south (areas of Black Sea region, Crimea, boundary subregions in the south) areas in the east and center of Ukraine affected by extreme MSAT values are the most vulnerable; in 2010-2014 this influence intensified. Increase in the vulnerability based on the maximum air temperature occurs on the background of certain changes in the atmospheric circulation, under conditions of anticyclonic fields prevalence throughout the year along with increase of the temporal exposure to the elementary synoptic process. On the other hand, the aforementioned increase of recurrence of extreme hydrometeorological phenomena is a consequence of sharp changes of synoptic situation, which is especially the case after a period of settled weather. The conclusion that atmospheric circulation is a main agent responsible for extreme weather and that it is not studied completely so far was made.

Determination of Parameters of Heat Treatment and Melting of Materials in a Solar Furnace

This article proposes a technique for defining the parameters of heat treatment and melting of materials in a solar furnace. The parameters are the flux density distribution in the working zone, the maximum heating temperature and temperature distribution in the working zone, and the specific material melting rate.

Numerical study of chemical kinetics and radiation heat transfer characteristics on the temperature distribution in the oxy-fuel combustion

In this study, The IFRF methane-oxygen combustion furnace is used to investigate the effect of the radiation model, the method of evaluated absorption and emission coefficients and the different chemical mechanisms. The simulations are performed with OpenFOAM open source software by using of PaSR (partially stirred reactor) combustion model. The numerical investigations are carried out without radiative heat transfer and with the modeling of the radiation source term using the P1 (spherical harmonic radiation model) and DO (discrete ordinate) models. To evaluate the absorption and emission coefficients used from the constant coefficients, the grey mean gases model in terms of temperature polynomial, the WSGGM (weighted sum of grey gases model) and refined WSGGM models. The investigation of the global mechanism effect on the temperature distribution in the oxy-fuel combustion is performed by the modified 2-step Westbrook-Dryer mechanism by Yin and modified 4-step Jones-Lindstedt mechanisms by Yin and Andersen. The results indicate that the lack of consideration of radiation heat transfer in the oxy-fuel combustion leads to a large error in the prediction of the maximum and average temperature distributions inside the furnace. Also, the DO model has less error than P1 model due to more heat loss prediction by P1 model in the low optical thickness. The WSGGM model for calculating of absorption and emission coefficients provide the best result in comparison with other methods. The refined 4-step Jones-Lindstedt mechanism by Andersen has best prediction of on the basis of numerical simulations.

Drill-exit temperature characteristics in drilling of UD and MD CFRP composites based on infrared thermography

This paper presents a comprehensive study on the complex drill-exit temperature characteristics in the drilling of unidirectional (UD) and multidirectional (MD) CFRPs using a state-of-art microscopy infrared imaging system. For the first time, temperature variation and distribution at drill exit have been revealed in full detail, associated with the CFRP material properties and drilling conditions. Results suggest that the actual drill/CFRP interactions have critical but similar effects on the drill-exit temperatures for UD and MD CFRPs. Specifically, three distinct cutting regions with varying temperature characteristics are evident when the main cutting edge is acting on the drill exit material. In all cases, the temperature distribution features elliptical shape, of which the eccentricity depends on the lay-up sequence and the drilling depth. In addition, the real-time temperature profiles and 2D/3D maximum temperature distribution maps are created with high visualization. With the aid of those findings, the relationships between drilling temperature maxima, their locations and drilling depths have been discovered and temperature effects on drill-exit damages have been elucidated for the first time. MD CFRP is proven more difficult to achieve high drilling qualities at certain fiber cutting angles than UD CFRP due to the associated temperature effects. Such important knowledge enables the identification of the heat affected zones and subsequently informs strategies for reducing the negative temperature effects.

Thermal Hydraulic Evaluation of a proposed annular Fuel for VVER1000 Reactor

Thorium based fuel is a promising fuel as it reduces the radiation protection cost of safety and improves the fuel performance with high burnup capability. In this paper the core of VVER-1000 nuclear reactor is designed with (Th0.9U0.1) O2 annular fuel rod for internally and externallycooled (dual cooled) fuel. Thermal performance of the present case is analyzed using ANSYS CFD code. Equivalent cell including a fuel rod and its surrounding coolant within a hexagonal assembly in the hot channel is simulated to get the maximum fuel temperature and maximum clad temperature. The results are compared with the calculated results obtained for the conventional UO2 fuel rod. Critical Heat Flux (CHF) and minimum DNBR are obtained and validated. The results indicated that the maximum fuel temperature of (Th0.9U0.1) O2 annular fuel is lower than that of the UO2 fuel by about 530oK. Lower maximum temperature and flatten temperature distribution in the thorium-based annular fuel rod provides more thermal safety margin in the reactor.

Experimental study on sodium droplet combustion and spatial temperature distribution characteristics

ABSTRACT In the operation of the sodium-cooled fast reactor, the accident caused by the leakage and combustion of liquid sodium is common and frequent. In this paper, the combustion and spatial temperature distribution characteristics at the different distances from the center of droplet and the different angles (0–30°) were studied by carrying out the experiments of the oxidation and combustion under initial temperatures (200–350°C) of sodium droplet, oxygen concentrations (12–21%) and ambient atmosphere temperatures (80°C and 180°C). The experiment results show that the ambient atmosphere temperature cannot change the three stages (surface oxidation, preignition, and combustion) of sodium droplet combustion but it will change the characteristics of every stage. When the temperature of sodium droplet excesses the characteristic temperature (600°C), the temperatures of all spatial measuring points begin to rise noticeably. The peak temperature of the sodium droplet that completely burned could roughly reach 580–1000°C. The distributions of the spatial maximum temperature in three angle directions are in conformity with exponential function as the distance increases. The study provides the technical support on the evaluation and analysis of various forms of sodium fire accidents.

Temperature-based method for determination of feed increments in crankshaft grinding

The design of a crankshaft-grinding cycle involves determining the radial infeed and axial infeed in each feed increment. A new method for determination of feed increments is developed to increase productivity while avoiding thermal damage. Analyses of the geometry, kinematics and specific-energy characteristic are made to estimate the feed-dependent distribution of maximum surface temperature along the wheel profile. It is discovered that there are two temperature maxima in the grinding zone when feeding both axially and radially. Therefore, the developed method determines the infeeds such that a predetermined burn threshold is matched in these two critical points. The new technology is validated by measurements of Barkhausen noise and residual stress. A comparison is made between the temperature-based method and the radial-plunge method previously used in production. The comparison indicates that lower cycle times are attainable with less risk of thermal damage. Results for material-removal rate and maximum surface temperature are also presented.

DAILY MINIMUM AND MAXIMUM AIR TEMPERATURE IN POLAND IN THE YEARS 1951–2005

In this study grid data of daily maximum and minimum air temperatures taken from the NCEP/NCAR reanalysis for the territory of Poland for the years 1951–2005 have been used as a basis for an analysis of the spatial distribution of daily maximum and minimum air temperature, the frequency of characteristic days and the variability of these parameters in the period analysed. The results obtained were then compared to the variability in atmospheric circulation in Europe, described by the North Atlantic Oscillation (NAO) index.

Warming across decades and deciles: minimum and maximum daily temperatures in China, 1955–2014

ABSTRACTWe report on changes in annual decile groups of daily maximum and minimum temperatures (Tmax and Tmin) from 437 weather stations across China since 1955, with special attention to the reported global warming ‘hiatus’ period since 1999. The values of Tmax and Tmin have increased significantly across all deciles between 1955 and 2014, with colder deciles of Tmin increasing faster than warmer deciles. We find abrupt increases starting at colder deciles since the early 1970s for Tmin and mid‐1980s for Tmax, followed by increases in the middle deciles in the later 1980s and in the warmer deciles in the early 1990s for both Tmax and Tmin. During the warming hiatus period, in contrast to the prior rapid warming period, colder deciles show no significant decreasing trends, while most middle to warmer deciles of Tmin continue to increase significantly, a finding which is masked in studies focusing on either average temperatures or extremes. The recent pause in the increase of mean temperatures is probably due to opposing changes in the trends at the tails of the temperature distribution. Our results demonstrate the differential changes in class intervals across the entire distribution of daily maximum and minimum temperatures.

A study on the temperature distribution based on the smoke thermal boundary layer below ceiling in the locomotive

Modern rail car system highlights an interdisciplinary cooperation between dynamics, mechanical structure and materials science. The complexity of the system presents a big challenge for full comprehension of maximum ceiling temperature distribution of motive cabin, driven by hot smoke buoyancy. The study gives helpful advice for the installation distance of the fire detector below the ceiling. To quantify the characteristics of the distributions, the concept of thermal boundary layer is introduced with two factors, smoke screen and high blockage ratio of cross section. The factors are obtained through large eddy simulation, and examined by a series of small scale experiments. As a result, the temperature gradient and distributions of characteristic temperature could be derived from thermal boundary layer (TBL) distributions, and the curve of TBL could be described by the several slope lines. A one-dimensional exponential function based on the TBL is established to predict the maximum temperature distributions under the locomotive structure.

Extreme maximum temperature events and their relationships with large-scale modes: potential hazard on the Iberian Peninsula

The aim of this paper is to analyze spatiotemporal distribution of maximum temperatures in the Iberian Peninsula (IP) by using various extreme maximum temperature indices. Thresholds for determining temperature extreme event (TEE) severity are defined using 99th percentiles of daily temperature time series for the period 1948 to 2009. The synoptic-scale fields of such events were analyzed in order to better understand the related atmospheric processes. The results indicate that the regions with a higher risk of maximum temperatures are located in the river valleys of southwest and northeast of the IP, while the Cantabrian coast and mountain ranges are characterized by lower risk. The TEEs were classified, by means of several synoptic fields (sea level pressure, temperature, and geopotential height at 850 and 500 hPa), in four clusters that largely explain their spatiotemporal distribution on the IP. The results of this study show that TEEs mainly occur associated with a ridge elongated from Subtropical areas. The relationships of TEEs with teleconnection patterns, such as the North Atlantic Oscillation (NAO), Western Mediterranean Oscillation (WeMO), and Mediterranean Oscillation (MO), showed that the interannual variability of extreme maximum temperatures is largely controlled by the dominant phase of WeMO in all seasons except wintertime where NAO is prevailing. Results related to MO pattern show less relevance in the maximum temperatures variability. The correct identification of synoptic patterns linked with the most extreme temperature event associated with each cluster will assist the prediction of events that can pose a natural hazard, thereby providing useful information for decision making and warning systems.

Phenological patterns of flowering across biogeographical regions of Europe.

Long-term changes of plant phenological phases determined by complex interactions of environmental factors are in the focus of recent climate impact research. There is a lack of studies on the comparison of biogeographical regions in Europe in terms of plant responses to climate. We examined the flowering phenology of plant species to identify the spatio-temporal patterns in their responses to environmental variables over the period 1970-2010. Data were collected from 12 countries along a 3000-km-long, North-South transect from northern to eastern Central Europe.Biogeographical regions of Europe were covered from Finland to Macedonia. Robust statistical methods were used to determine the most influential factors driving the changes of the beginning of flowering dates. Significant species-specific advancements in plant flowering onsets within the Continental (3 to 8.3 days), Alpine (2 to 3.8 days) and by highest magnitude in the Boreal biogeographical regions (2.2 to 9.6 days per decades) were found, while less pronounced responses were detected in the Pannonian and Mediterranean regions. While most of the other studies only use mean temperature in the models, we show that also the distribution of minimum and maximum temperatures are reasonable to consider as explanatory variable. Not just local (e.g. temperature) but large scale (e.g. North Atlantic Oscillation) climate factors, as well as altitude and latitude play significant role in the timing of flowering across biogeographical regions of Europe. Our analysis gave evidences that species show a delay in the timing of flowering with an increase in latitude (between the geographical coordinates of 40.9 and 67.9), and an advance with changing climate. The woody species (black locust and small-leaved lime) showed stronger advancements in their timing of flowering than the herbaceous species (dandelion, lily of the valley). In later decades (1991-2010), more pronounced phenological change was detected than during the earlier years (1970-1990), which indicates the increased influence of human induced higher spring temperatures in the late twentieth century.

Optimal Heat Transfer Coefficient Distributions during the Controlled Cooling Process of an H-Shape Steel Beam

Three-dimensional thermal-mechanical models for the prediction of heat transfer coefficient distributions with different size beams are investigated. H300 × 300, H250 × 250, and H200 × 200 H-shape steel beams are investigated in a controlled cooling process to obtain the design requirements for maximum uniform temperature distributions and minimal residual stress after controlled cooling. An algorithm developed with the conjugated-gradient method is used to optimize the heat transfer coefficient distribution. In a comparison with the three group results, the numerical results indicate that, with the same model and under the same initial temperature (T=850°C) and final temperature (T=550±10°C), the heat transfer coefficients obtained with the conjugated-gradient method can produce more uniform temperature distribution and smaller residual web stress, with objective functions of the final average temperature Tave±ΔT and maximum temperature difference to minimum min⁡ΔTmax(x,y). The maximum temperature difference is decreased by 57°C, 74°C, and 75°C for Case 1, Case 2, and Case 3, respectively, the surface maximum temperature difference is decreased by 60~80°C for three cases, and the residual stress at the web can be reduced by 20~40 MPa for three cases.

Modeling of Temperature Field during Multi-Pass GMAW Surfacing or Rebuilding of Steel Elements Taking into Account the Heat of the Deposit Metal

This paper proposed an analytical model for describing the temperature field of multi-pass arc weld surfacing. The temperature field is described analytically assuming a bimodal volumetric model of the heat source and a semi-infinite body model of the (rebuilt) workpiece. The suggested analytical solution takes into account the temperature changes caused not only by the direct heat of an electric arc, but also by the heat of the applied weld (melted metal of electrode). The solution considers temperature increments caused by overlaying consecutive welding sequences and by self-cooling of areas previously heated. Computations of the temperature field are carried out during the multi-pass gas metal arc welding (GMAW) surfacing of a steel plate. The results are presented in the form of transient and maximum (achieved in whole welding process) temperature distributions in the element’s cross-section, as well as thermal cycles at the selected point.