Surface Temperature Of Materials Research Articles

Thermo-electrical behaviour of cyclic olefin copolymer/exfoliated graphite nanoplatelets nanocomposites foamed through supercritical carbon dioxide

In this work, novel electrically conductive cyclic olefin copolymer/exfoliated graphite nanoplatelets foams were prepared through a supercritical carbon dioxide treatment starting from the corresponding unfoamed materials prepared by melt compounding, in order to investigate their thermo-electrical properties. For both unfoamed and foamed samples, the exfoliated graphite nanoplatelets introduction led to a systematic enhancement of the thermal degradation temperature. Dynamic-mechanical thermal analysis revealed that the nanofiller addition promoted an enhancement of the storage modulus and of the glass transition temperature over the whole range of the applied foaming pressures. While for unfoamed materials exfoliated graphite nanoplatelets introduction determined an important decrease of the electrical resistivity, the foaming process induced the breakage of the conductive path, with a consequent increase of electrical resistivity. Evaluation of the surface heating upon voltage application showed that the surface temperature of unfoamed materials could be noticeably increased at relatively low voltage levels, while a less pronounced surface heating could be obtained with the corresponding nanocomposite foams.

Assessment of various parametric effects on the performance of a commercial grade photovoltaic solar panel

This paper presents the implementation of an integrated photovoltaic solar panel model which includes all the necessary parameters in order to simulate and analyze using Matlab/Simulink software. The integrated photovoltaic model is validated with Matlab/Simulink simulation for a commercially available 100W photovoltaic solar panel module. Using the commercial solar panel specifications, such as solar irradiation, panel temperature, etc. the integrated model solved with Matlab/Simulink returns an I-V and P-V performance characteristics under various conditions which enabled detailed analysis, assessment of parametric effect on the performance of the solar panel. According to the model simulation results for a commercial RNG-100D solar panel, it was found that panel performance was mostly affected by the variations of solar radiation/insolation, panel surface temperature, series resistance, shunt resistance and band gap energies of the semiconductor materials. The commercial solar panel simulation results show that a photovoltaic panel output power reduces as module temperature decreases. Taking the effect of sunlight irradiance and cell temperature into consideration, the output current and power characteristics of PV model are simulated and results can be optimized using the proposed model. The integrated model enables the dynamics of PV power system to be easily simulated, analyzed, and optimized.

Analysis of surface temperature measurements over complex urban sites

The aim of this study is to analyse the thermal properties of natural and artificial urban surfaces and the impact of surface colours and shading. Measuring campaigns were conducted in spring and summer (2018-2019) in the district XI of Budapest to determine the surface temperature of various urban materials. The results show that the coolest surfaces are natural covers (water, vegetation), while the hottest surfaces are concrete pavements, asphalt and rubber paving when exposed to direct solar radiation. Moreover, among concrete pavements, light coloured surfaces warm up 5-6 °C less on average compared to dark coloured surfaces. The use of rubber paving may be disadvantageous from the urban climatological point of view, as these surfaces become extremely hot under sunny conditions.

Application of pyrometer and standard sample to determine surface temperature of studied materials

Determining the surface temperature of materials with unknown emissivity is studied. A method for determining the surface temperature using a standard sample of average spectral normal emissivity in the wavelength range of 1,65–1,80 μm and an industrially produced Metis M322 pyrometer operating in the same wavelength range. The surface temperature of studied samples of the composite material and platinum was determined experimentally from the temperature of a standard sample located on the studied surfaces. The relative error in determining the surface temperature of the studied materials, introduced by the proposed method, was calculated taking into account the temperatures of the platinum and the composite material, determined from the temperature of the standard sample located on the studied surfaces, and from the temperature of the studied surfaces in the absence of the standard sample. The relative errors thus obtained did not exceed 1,7 % for the composite material and 0,5% for the platinum at surface temperatures of about 973 K. It was also found that: the inaccuracy of a priori data on the emissivity of the standard sample in the range (–0,01; 0,01) relative to the average emissivity increases the relative error in determining the temperature of the composite material by 0,68 %, and the installation of a standard sample on the studied materials leads to temperature changes on the periphery of the surface not exceeding 0,47 % for composite material and 0,05 % for platinum.

Quality analysis of microwave dried iron yam chips controlled by infrared thermal imaging

Abstract The aim was to study the real-time temperature control by infrared thermography and the quality changes of the iron yam chips during drying processes. Microwave (MW) and heat pump (HP) were used to dry iron yam chips at 50, 60 and 70 °C. The material surface temperatures were online controlled by infrared thermal imaging system in the process of microwave drying. Temperature, drying efficiency, texture and color were estimated. The experimental results were shown on the basis of drying process characteristics and dried product qualities. Temperature fluctuations became more violent with the increase of drying time and drying temperature, and had a negative impact on the quality of dried iron yam chips. There were no significant differences of hardness and cohesiveness between both drying methods. The springiness and chewiness values of iron yams dried by HP were lower than samples dried by MW. It is worth noting that lightness and white index values of the iron yam chips dried by microwave at 70°C were obviously lower (p < 0.05) than the fresh samples and the iron yam chips dried by heat pump.

Bake-Out Strategy Considering Energy Consumption for Improvement of Indoor Air Quality in Floor Heating Environments.

Improved quality of life has led to a growing demand for better indoor air quality (IAQ). Buildings are becoming more airtight and insulated in order to minimize energy consumption. The importance of both energy conservation and IAQ improvement has been recognized and addressed by many studies. Bake-out is the process of using indoor heating to remove volatile compounds present in building materials and furnishings so that they can be vented out into the atmosphere. Indiscriminate use of heating to increase the surface temperature of materials during this process can result in significant loss of energy. Therefore, energy-efficient bake-out should be performed by considering both the floor temperature and the emission amount of pollutants. This study aims to investigate an effective and economical bake-out implementation strategy via experimentation and computational fluid dynamics analysis. The results showed weak direct correlation between the heating energy consumption and the amount of pollutants emitted. The study also highlights the passive option of installing sorptive building materials for improving IAQ economically.

Effects of urban geometry and green area on thermal condition of urban street canyons in Bangkok

ABSTRACTUrban geometry and green area have a great impact on urban heat island intensity (UHII) in Bangkok. The current study focuses on 1) effect of height-to-width (H/W) ratios of street canyon on increasing UHII; and 2) percentage of tree coverage and non-tree coverage area, the surface temperature of pervious and impervious surfaces, and the surface temperature of planting materials. The night-time investigation to indicate the UHII influenced by H/W ratio was done with car traverse. UHII magnitudes were 6.33 K, 6.70 K and 4.54 K for the days representing rainy season, winter, and summer, respectively. Results from the daytime investigation to study green area effect show that surface temperature varies according to percentage of pervious surface area. With combination of tree coverage area, surface temperature will be decreased more. The optimum surface temperature was found when pervious surface was around 60% and tree coverage was around 25%.

Climate Mitigation and Adaptation Strategies for Roofs and Pavements: A Case Study at Sapienza University Campus

The progressively emerging concept of urban resilience to climate change highlights the importance of mitigation and adaptation measures, and the need to integrate urban climatology in the design process, in order to better understand the multiple effects of combined green and cool technologies for the transition to climate responsive and thermally comfortable urban open spaces. This study focuses the attention on selected mitigation and adaptation technologies; two renovation scenarios were designed and modeled according to the minimal intervention criterion. The study pays attention to the effect on surface temperature and physiological equivalent temperature (PET) of vegetation and high albedo materials characterizing the horizontal boundaries of the site. The Sapienza University campus, a historical site in Rome, is taken as a case study. These results highlight the importance of treed open spaces and the combination of permeable green pavements associated with cool roofs as the most effective strategy for the mitigation of summer heatwaves and the improvement of outdoor thermal comfort.

Influence of steam condensation on vitamin C retention in green turnip undergoing low pressure superheated steam drying

AbstractIn this article, green turnip discs were dried in low pressure superheated steam for high vitamin C retention. Drying kinetics and vitamin C variation in green turnip was studied at 95 mbar in superheated steam from 75 to 90 °C, considering the influence of steam condensation on the retention of vitamin C. It was found that an amount of vitamin C was transferred in the condensate water during drying process, especially in the constant evaporation period. Due to steam condensation and assistant electrical heating, the material surface temperature was higher than the water boiling point temperature at corresponding environment pressure when superheated steam stopped condensing. The condensate occurred in material surface could enhance the loss of vitamin C in green turnip. Vacuum preheating could reduce the amount of steam condensation and material temperature rise, and hence the vitamin C retention in green turnip was higher than that in continuous superheated steam drying.Practical applicationsGreen turnip is a nutritional, economical and healthy plant, which contains various nutrients such as carotene, ascorbic acid, protein, etc. Dried green turnip has been used as a resource of food seasoning and pickled foods. Fresh green turnip having relatively high moisture contents is very sensitive to microbial spoilage. Drying is one of the most common methods used for green turnip preservation. LPSSD is an innovative technology and which has been applied for dehydration of biological materials due to high nutrients retention, better product appearance, and energy efficiency. Low pressure superheated steam drying process has an initial steam condensation period, transferring an amount of latent heat to the material. It has been demonstrated that steam condensation on sample surface have some influence on material quality. Understanding the effect of condensation on vitamin C retention in green turnip is helpful for improving the quality of dried green turnip slices.

A stable cellular automaton model for composite materials with defects

PurposeAs the internal defects (pore defect) of materials formed during the preparation of the composite material have important effects on wear process, the model has been improved to simulate it.Design/methodology/approachMaterials with defects were simulated by an improved cellular automaton model which show changes in three-dimensional topography, temperature of surface and coefficient of friction (COF) during wear process.FindingsIt is found that defects increase temperature of material surface. Besides, the materials with little defects have a smaller COF than base materials, as the large block defects make the COF larger than base materials.Originality/valueExcept for effects of defects were simulated in model, how to initialize the surface temperature status that many reports do not take into account can be preferred. And the model is convenient to simulate complex composite materials by setting different properties of cells.

Quantitative Analysis Procedure for Building Materials in Historic Buildings by Applying Infrared Thermography

Historic buildings have a great cultural and architectural value. It is necessary to analyze their state of conservation, but sometimes it is difficult to perform laboratory tests without damaging this heritage. In the field of architecture, infrared thermography is usually used to provide descriptive information about the surface temperature of building materials. This current research presents a methodology widely applicable to historic buildings. As an example of application, the study is focused in the Seminary-School of Corpus Christi of Valencia (Spain), a very outstanding building from the 16th Century. This research presents an analytical study to be able to differentiate the temperature distribution of all pixels of a thermographic image. Thermal images are a matrix of data and their study helps us in decision-making based on objective data.

Experimental study on performance of outdoor ground materials in aspect of surface temperature by constant field experiment in subtropical climate city

In order to create a comfortable building thermal environment, it is important to study the outdoor ground materials performance. In this article, we carried out a constant field experiment in Guangzhou, China, studying on the variations of the surface temperature of three common outdoor building materials: concrete, pavement and grass. We put the equipment on six experiment points respectively to measure the ground surface temperature constantly. The result shows that because of the specific heat capacity, both concrete and pavement have an obvious time delay during their temperature decrease when the grass ground has almost no time delay. And when in the same conditions (exposed to sunlight all day), the material with a low specific heat capacity has a more sensitive variation in temperature. The lower the specific capacity is, the steeper the variation trend of the surface temperature will be. So compared with concrete, the pavement brick ground with a low specific heat capacity has a higher surface temperature in daytime and a lower temperature in the late night time. When in different conditions (different time exposed to sunlight), the temperature value is proportional to the time exposed to the sunlight between the same materials. The concrete exposed to sunlight all day has the highest temperature when the shaded one has the lowest. This experiment reveals that both specific heat capacity and the exposed time to sunlight has a strong influence on the surface temperature of outdoor materials. In subtropical region, the materials with a higher specific heat capacity and a less time exposed to sunlight may be more beneficial to the building thermal environment.

Preliminary Results on Thermal Shock Behavior of CuZnAl Shape Memory Alloy Using a Solar Concentrator as Heating Source

It is highly accepted that martensitic transformation can be induced by temperature variation and by stress solicitation. Using a solar concentrator, we manage to increase the material surface temperature (till 573 respectively 873 K) in very short periods of time in order to analyze the material behavior under thermal shocks. The heating/cooling process was registered and analyzed during the experiments. Material surface was analyzed before and after thermal shocks by microstructure point of view using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The experiments follow the material behavior during fast heating and propose the possibility of activating smart materials using the sun heat for aerospace applications.

Transient heat transfer analysis of laminated materials based on extended separation of variables

In general, when the one-dimensional heat conduction equation is solved by the method of separation of variables, we need to know the governing equations, two boundary conditions and initial condition. Because the thermophysical parameters in different layers of laminated materials are different, the heat conduction model cannot be expressed by the same governing equation. For each layer of laminated material, the boundary condition is unknown. That equation can-not be solved directly by the general separation variable method. In this work the separation of variable method is extended. The temperature field of laminated material's heat transfer is divided into many minute time intervals on the time axis. Based on differential conception, in a minimum time interval, the temperature at the junction of laminated materials can be considered to be proportional to time. Assume that the slope coefficient makes the boundary condition known, then for each layer of laminated materials, the general separation of variables method will be used to solve the temperature field. According to the same temperature and the energy continuity at the junction of laminated materials, one can solve the slope coefficient. The temperature field in the whole time domain can be obtained through cycling. Then the three-layer insulation materials are analyzed by the extended separation variable method. The correctness of the method is verified by comparing the calculated results with those from the finite element method. The influences of the type and thickness of heat insulation layer, heat transfer coefficient, air temperature on the heat insulation are studied. It is found that the thermal conductivity of the thermal insulation layer has a great influence on the insulation. The material with low heat conduction coefficient can enhance the heat insulation effect. The thicker the thickness of the insulation layer, the more slowly the surface temperature of the heat insulation material rises, and the lower the final temperature, the better the insulation effect is. The thicker the thickness of the insulation layer, the smaller the heat flux density of the heat insulation material shell is, and the better the heat insulation effect when the heat transfer reaches a stable state. All calculation results are consistent with physical phenomena. In this work, the analytical method is used to solve the heat transfer problem of laminated materials. Compared with the general numerical methods, the analytical method presents clear physical meaning and high efficiency of operation as well.

Thermal comfort of pedestrian spaces and the influence of pavement materials on warming up during summer

Public space is very valuable for a variety of community activities. Open public space comfort is one of the main indicators that provide its enjoyability, attractiveness and liveability. Having in mind that the climate conditions and the implemented urban design are influential in providing pedestrian thermal comfort, this study will focus on physical attributes of used pavement materials and their impact when they are exposed to high summer temperatures as well as on thermal comfort of the users of open public spaces. The methods that were used in the analysis include the method of direct surveying of inhabitants, the method of observation and the method of measuring the characteristics of different materials used for pavement in the pedestrian zone. The measuring of the current surface temperature of different paving materials used for pedestrian zone was performed during the summer season (July, August, and September) of 2015 in the central city zone of the city of Niš, with the goal of determining the maximum heating up of horizontal surfaces, i.e. pavements. The survey was done in July 2015 in the main square in Niš. The measuring determined that in the same conditions, various materials yield various maximum temperatures. It was also concluded that the type of material, colour, roughness and shading of an area affect the heating up of pedestrian surfaces. The purpose of this paper is to highlight the complexity of the relationship between microclimate thermal comfort in public open spaces and the measured temperature of the pavement surface, and to emphasize the importance of this relationship in the context of contemporary urban design. The paper presents the case study of pedestrian spaces in the central area of the City of Niš in Serbia.

Infrared thermographic measurement of the surface temperature and emissivity of glossy materials

Determination of the surface temperature and emissivity of glossy materials is a complicated task due to the relatively wide range of emissivity values and the reflection of infrared radiation from surrounding objects. As a consequence, standard methods used in infrared thermography are not applicable. In this article, an alternative method is proposed for the measurement of the surface temperature and emissivity of glossy materials used in the external structures of buildings that is based on an external source of thermal radiation. It is shown that the method gives quite accurate values of emissivity of both low- and high-emissivity glossy materials, whereas the surface temperature of low-emissivity glossy materials is less accurate and strongly depends on the accuracy of the used thermal camera.

Photo-assisted electron emission from illuminated monolayer graphene

We establish a formalism to address co-existing and complementing thermionic and photoelectric emission from a monolayer graphene sheet illuminated via monochromatic laser radiation and operating at a finite temperature. Taking into account the two dimensional Fermi-Dirac statistics as is applicable for a graphene sheet, the electron energy redistribution due to thermal agitation via laser irradiation, and Fowler's approach of the electron emission, along with Born's approximation to evaluate the tunneling probability, the expressions for the photoelectric and thermionic emission flux have been derived. The cumulative emission flux is observed to be sensitive to the parametric tuning of the laser and material specifications. Based on the parametric analysis, the photoemission flux is noticed to dominate over its coexisting counterpart thermionic emission flux for smaller values of the material work function, surface temperature, and laser wavelength; the analytical estimates are in reasonably good agreement with the recent experimental observations [Massicotte et al., Nat. Commun. 7, 12174 (2016)]. The results evince the efficient utilization of a graphene layer as a photo-thermionic emitter.

Modification of electron density in F layer of ionosphere by dust suspension

The effect of the suspension of high/low work function dust in the F layer ionospheric plasma has been investigated. On the basis of kinetics formulation of the F-layer dusty plasma, the local electron density is shown to reduce or enhance by inserting fine dust of appropriate physical/material properties. The formulation includes the number and energy balance of the plasma constituents along with the charging of the dust particles; a novel approach to investigate the effect of diffusion on plasma particles in the F-layer has been outlined. The consequence of the physical parameters of dust, namely, number density, material work function, photo-efficiency, and surface temperature, on the charging of dust and local plasma parameters at different ionospheric altitudes in the F layer has been worked out and presented graphically; the significance of plasma diffusion has been highlighted. The modification in local plasma density in the midday F-layer is seen to be sensitive to the dust parameters and altitude profile of the ionospheric plasma. Such modification in the local electron density is certainly of interest for radio wave propagation through the F layer.

Inverse technique for determining temperature dependence of material properties

PurposeThis paper aims to present a methodology of finding temperature dependencies of selected physical parameters of metals. The method is based on the combination of measurement of the surface temperature of material during the process of heating and subsequent solution of the inverse problem using multi-parametric optimization.Design/methodology/approachThe methodology is based on measurements and numerical solution of the forward and inverse problem, taking into account all involved nonlinearities (saturation curve of the processed steel material and temperature dependences of its physical parameters). The inverse problem is solved by a genetic algorithm.FindingsThe suggested methodology was successfully verified on several metal materials whose temperature-dependent parameters are known. The calculated and measured results exhibit a very good accordance (the differences do not exceed about 10 per cent for room and higher temperatures).Research limitations/implicationsAt this moment, the methodology successfully works when the temperature dependence of just one material parameter is to be found (which means that the temperature dependencies of other parameters are known). The accuracy of results also depends on the correctness of other input data.Practical implicationsThis paper provides a relatively easy possibility of finding the temperature dependencies of thermal conductivity or heat capacity of various alloys.Originality/valueThe paper proposes a methodology of finding the temperature dependence of a given material parameter that is not known in advance (which is of great importance in case of alloys).

Incubation time of heterogeneous growth of islands in the mode of incomplete condensation

The incubation time necessary for the growth of surface islands on heterogeneous nucleation centers to begin has been theoretically analyzed depending on the material gas flow and surface temperature. It is shown that, under heterogeneous growth in the mode of incomplete condensation, the incubation time increases with temperature according to the Arrhenius law and is inversely proportional to the flow, irrespective of the mechanism of diffusion transport to islands. The results obtained have been qualitatively compared with the experimental data on the incubation time for three-dimensional GaN islands arising in the initial stage of self-induced growth of GaN nanowires.