scholarly journals Effects of Albedo and Thermal Inertia on Pavement Surface Temperatures with Convective Boundary Conditions—A CFD Study

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2078
Author(s):  
Tathagata Acharya ◽  
Brooke Riehl ◽  
Alan Fuchs
Keyword(s):  
Building Materials ◽  
Thermal Inertia ◽  
Concrete Surface ◽  
Published Data ◽  
Concrete Pavements ◽  
Ambient Conditions ◽  
Convective Boundary ◽  
Ambient Temperatures ◽  
Pavement Surface ◽  
Surface Temperatures

The urban heat island (UHI) effect increases the ambient temperatures in cities and alters the energy budget of building materials. Urban surfaces such as pavements and roofs absorb solar heat and re-emit it back into the atmosphere, contributing towards the UHI effect. Over the past few decades, researchers have identified albedo and thermal inertia as two of the most significant thermal properties that influence pavement surface temperatures under a given solar load. However, published data for comparisons of albedo and thermal inertia are currently inadequate. This work focuses on asphalt and concrete as two important materials used in the construction of pavements. Computational fluid dynamics (CFD) analyses are performed on asphalt and concrete pavements with the same dimensions and under the same ambient conditions. Under given conditions, the pavement top surface temperature is evaluated with varying albedo and thermal inertia values. The results show that the asphalt surface temperatures are consistently higher than the concrete surface temperatures. Surface temperatures under solar load reduce with increasing albedo and thermal inertia values for both asphalt and concrete pavements. The CFD results show that increasing the albedo is more effective in reducing pavement surface temperatures than increasing the thermal inertia.

Using Thermoelectric Cooling With Tourniquets for Nerve Preservation

2016 ◽  
Author(s):  
M. Trupiano ◽  
S. Aarabi ◽  
A. F. Emery
Keyword(s):  
Thermal Conditions ◽  
Ambient Conditions ◽  
Transfer Coefficients ◽  
Thermoelectric Coolers ◽  
Ambient Temperatures ◽  
Nerve Preservation ◽  
Heat Transfer Coefficients ◽  
Surface Temperatures ◽  
Element Simulation ◽  
Free And Forced Convection

The use of a tourniquet leads to nerve damage, even if applied for short periods of time. This damage can be minimized if the limb is cooled. Because of the low conductivities of human tissue, core limb cooling is slow unless the surface temperature is very cool. Subzero surface temperatures can lead to skin injury (i.e., frostbite). Ideally one would adjust the limb surface temperatures as a function of time to maximize the cooling rate while avoiding permanent tissue damage. One possible approach is to use a thermoelectric cooler (TEC) in conjunction with a programmable power supply. TEC performance varies strongly with heat absorption rate, a function of limb thermal properties, and hot side temperatures that are strongly affected by the surface conditions on the hot side, i.e., overall heat transfer coefficients and ambient conditions. The paper describes the use of finite element simulation to predict the usefulness of using thermoelectric coolers applied to the surface of a limb when compared to the standard approach of using ice packs. Since the TEC performance is strongly influenced by its warm side thermal conditions, experimental results are presented for different ambient temperatures, free and forced convection, and evaporation of water from a wickable covering.

scholarly journals Analyses of urban pavement surface temperatures

2015 ◽  
Vol 10 (3) ◽  
pp. 239-246 ◽  
Author(s):  
Aleksandra Deluka-Tibljaš ◽  
Sanja Šurdonja ◽  
Sergije Babić ◽  
Marijana Cuculić
Keyword(s):  
Urban Areas ◽  
Concrete Surface ◽  
City Centre ◽  
Heat Islands ◽  
Pavement Surface ◽  
Island Effect ◽  
Surface Temperatures ◽  
Additional Heating ◽  
Air Temperatures ◽  
Surface Materials

Heat islands are areas that have higher air temperatures than their surroundings. It has been proven that the use of certain types of pavement surface materials contributes to the occurrence of heat islands. The heat island effect is dominant in urban areas, mainly in city centres. To identify potentially favourable pavement surface materials that are suitable for the use on surfaces in urban areas, an extensive analysis of in-place material temperatures was conducted in the city centre of Rijeka (Croatia) during the summer of 2011 and 2012. The measurements included temperatures of pavement surfaces made of asphalt, concrete and stone. The analysis results identified local materials whose use help to reduce or mitigate the effect of additional heating in the urban environment caused by emission of heat from pavement surfaces. In terms of additional heating of urbanized areas, asphalt has proven to be significantly less favourable than other analysed materials. In addition to the materials selected for the use in wearing courses, their characteristics and the microclimates of the locations where they will be placed must be taken into consideration. Among the standard paving materials, in terms of heating and temperature, concrete is more favourable than asphalt because the differences between concrete surface temperatures and air temperatures are significantly smaller than between asphalt surface temperatures and air temperatures. Stone surfaces have proven to be the most favourable. The analysis results presented can be used to establish clear guidelines for using specific materials under specific conditions.

Measurements of laminar premixed methane—air flame thickness at ambient conditions

2009 ◽  
Vol 223 (8) ◽  
pp. 1969-1973 ◽  
Author(s):  
A Clarke ◽  
G K Hargrave
Keyword(s):  
Schlieren Image ◽  
Published Data ◽  
Ambient Conditions ◽  
Cold Surface ◽  
Data Set ◽  
Ambient Temperatures ◽  
Flame Thickness ◽  
Simultaneous Imaging ◽  
Experimental Errors

A new experimental data set for the flame thickness of laminar premixed methane—air flames at ambient conditions is presented. Prior to combustion the temperature and pressure of the premixed mixture were 298 K>5 K and 100 kPa>5 kPa, respectively. The fuel—air equivalence ratio was varied from 0.8 to 1.4 in 0.05 steps. The data were obtained using simultaneous imaging of the visible and Schlieren cones on the central axis of the symmetrical flame front of a non-cooled burner configuration. The data were analysed and the plane obtained from the Schlieren image corrected using a one-dimensional energy balance to obtain the position of the cold surface of the flame and hence allow determination of the flame thickness. The data presented agree within experimental errors with the limited existing published data. For the range of equivalence ratios studied, a second-order equation was fitted and presented for methane—air flames at atmospheric pressure and ambient temperatures.

scholarly journals LiNbO3Coating on Concrete Surface: A New and Environmentally Friendly Route for Artificial Photosynthesis

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Ranjit K. Nath ◽  
M. F. M. Zain ◽  
Abdul Amir H. Kadhum
Keyword(s):  
Building Materials ◽  
Artificial Photosynthesis ◽  
Reaction Pathway ◽  
Research Work ◽  
Pollution Prevention ◽  
Environmentally Friendly ◽  
Concrete Surface ◽  
Concrete Material ◽  
Gas Phases ◽  
Work Done

The addition of a photocatalyst to ordinary building materials such as concrete creates environmentally friendly materials by which air pollution or pollution of the surface can be diminished. The use of LiNbO3photocatalyst in concrete material would be more beneficial since it can produce artificial photosynthesis in concrete. In these research photoassisted solid-gas phases reduction of carbon dioxide (artificial photosynthesis) was performed using a photocatalyst, LiNbO3, coated on concrete surface under illumination of UV-visible or sunlight and showed that LiNbO3achieved high conversion of CO2into products despite the low levels of band-gap light available. The high reaction efficiency of LiNbO3is explained by its strong remnant polarization (70 µC/cm2), allowing a longer lifetime of photoinduced carriers as well as an alternative reaction pathway. Due to the ease of usage and good photocatalytic efficiency, the research work done showed its potential application in pollution prevention.

scholarly journals Synthesis of Nanotips Through Femtosecond Laser Ablation of Glass with Assisted Gas

2021 ◽  
Author(s):  
Nikunj Patel
Keyword(s):  
Femtosecond Laser ◽  
Building Materials ◽  
High Vacuum ◽  
Synthesis Method ◽  
Femtosecond Laser Ablation ◽  
Target Surface ◽  
Laser Pulses ◽  
Single Step ◽  
Femtosecond Laser Irradiation ◽  
Ambient Conditions

Nanotips are the key nanostructures for many applications. Until now, the nanotips of only the crystalline materials have been produced via various deposition methods which require sophisticated equipment, high vacuum, and clean room operations. This thesis proposes a single step, rapid synthesis method using femtosecond laser irradiation at megahertz frequency with background flow of nitrogen gas at ambient conditions. Amorphous nanotips are obtained without the use of catalyst. The nanotips grow from highly energetic plasma generated when target is irradiated with laser pulses. The vapor condensates, nanoparticles and droplets from the plasma get deposited back on to the hot target surface where they experience force imbalance due to which the stems for the nanotips growth are initiated. Once the stems are generated, the continuous deposition of vapor condensates [sic] provides building materials to the stems to complete the growth of nanotips. Further study found that the growth of the nanotips is influenced by laser parameters and gas conditions.

scholarly journals A Lesson of Sustainability Given by The Tropical Modernism in Kinshasa: The BCB Headquarters by Maurice Houyoux

2021 ◽  
Vol 3 (1) ◽  
pp. p22
Author(s):  
Alexis Tshiunza ◽  
Manlio Michieletto ◽  
Olatunde Adedayo
Keyword(s):  
Building Materials ◽  
Relevant Literature ◽  
Weather Condition ◽  
Tropical Region ◽  
Published Data ◽  
The Sun ◽  
Existing Buildings ◽  
Key Issues ◽  
Observation Method ◽  
Belgian Congo

The tropical region is often considered as a region where the sun shines intensely and the temperature varies at certain times of the year. In the case of Congo, the average weather condition is considered cool, however, there have been cases where the temperature reached up to 43° C. It is therefore imperative for buildings in this region to take into account the temperature variation while considering the comfort of the users. During the design and construction of the Bank of Belgian Congo, the availability of data to assist the architect Maurice Houyoux in meeting the challenge of the region was unavailable. The architect had to be creative in planning and overcoming the challenges posed by the environment. This paper seeks to examine the issues confronted by Maurice Houyoux and the design solutions he provided to ensure that the building was functional and responded to the tropical challenges. In undertaking this study, a historical approach was adopted through the review of relevant literature on the building and designs within the period of the development of the bank. An observation method was also deployed to verify some of the information found in the literature. The findings are presented using pictures and sketches to explain some of the key issues relevant to the design of the bank. The findings showed that despite the reduced number of published data for designing in such a region, the architect was able to examine the existing buildings and discuss with users of other constructions to obtain relevant data. The findings also showed that the building was able to respond to peculiar requirements to be functional. The paper concludes that the local building materials and traditional builders can be used to achieve a contemporary building that fits into the context towards sustainable architecture.

scholarly journals Mechanical and thermal characterization of a beet pulp-starch composite for building applications

2019 ◽  
Vol 85 ◽  
pp. 08005
Author(s):  
Hamzé Karpaky ◽  
Chadi Maalouf ◽  
Christophe Bliard ◽  
Alexandre Gacoin ◽  
Mohammed Lachi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Sugar Beet ◽  
Building Materials ◽  
Potato Starch ◽  
Starch Content ◽  
Compressive Strain ◽  
Thermal Inertia ◽  
Thermal Characterization ◽  
Sugar Beet Pulp ◽  
Beet Pulp

This work shows the making of a new bio-based material for building insulation from sugar beet pulp and potato starch. The material is both lightweight and ecofriendly. The influence of starch/ sugar beet pulp ratio (S/BP) is studied. Four binder mass dosages are considered, 10, 20, 30 and 40% (relative to the beet pulp). Samples are characterized in terms of absolute and bulk density, compressive and flexural strength, as well as thermal properties (thermal conductivity and thermal inertia). The compressive strength increases linearly with the S/BP mass ratio to reach 0.52 MPa and the compressive strain is 30%. The thermal conductivity is to around 0.070 W/m. K. The results obtained shows that increasing starch amount tends to decrease composite porosity but increases thermal conductivity and mechanical properties. Depending on the starch content, beet pulp composites have a good thermal and can be used as building materials.

Microscale Heat Island Characterization of Rigid Pavements

2017 ◽  
Vol 2639 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Sushobhan Sen ◽  
Jeffery Roesler
Keyword(s):  
Radiative Forcing ◽  
Time Lag ◽  
Thermal Inertia ◽  
Concrete Pavements ◽  
Heat Island ◽  
Rigid Pavements ◽  
Subsurface Layers ◽  
Urban Heat ◽  
Base Course

Rigid pavements have an impact on the urban heat island (UHI) and hence the surrounding environment and human comfort. Currently, most studies use a mesoscale approach in UHI characterization of pavements. This study proposes a microscale approach that can be incorporated into a pavement life-cycle assessment (LCA). The heat flux of various concrete pavements containing layers of varying thermal diffusivity and inertia was simulated. The surface pavement radiative forcing (RFp) was developed as a metric for use in a pavement LCA. Additionally, the heat conducted and stored in each concrete pavement system was analyzed using an average seasonal day metric to understand the temporal pavement energetics. Of the various thermal cases, only a higher albedo surface significantly changed the RFp for a fixed climate. However, a time lag was induced by the thermal inertia of the base course, which decreased the amount of heat conducted out of the pavement at night by storing heat in the base course for a longer time, effectively reducing nighttime UHI. Diurnal variations in thermal behavior can be controlled by changing the thermal properties of subsurface layers, which can be used to partially mitigate UHI.

Impact of Sweeping Jet on Area-Averaged Impingement Heat Transfer

2019 ◽  
Author(s):  
Andrea Osorio ◽  
Justin Hodges ◽  
Husam Zawati ◽  
Erik J. Fernandez ◽  
Jayanta S. Kapat ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heated Surface ◽  
Thermal Inertia ◽  
Jet Impingement ◽  
Target Surface ◽  
Bottom Surface ◽  
Fluidic Oscillator ◽  
Surface Temperatures ◽  
Sweeping Motion ◽  
The Impact

Abstract A series of sweeping jet-impingement experiments are conducted over a circular heated surface, with a main objective of understanding the impact of the unique flow field on the resulting heat transfer. The sweeping motion of the fluidic oscillator is influenced by the sweeping frequency and sweeping angle where each is directly dependent on the geometric design (i.e. internal feedback loops, mixing chamber, etc.). The target surface consists of a heated copper disk, where heater power is supplied to the bottom surface of the disk and adjusted until a differential of 30°C is obtained between the jet and target surface temperatures. An energy balance over the target surface temperatures provides a means for calculating area-averaged heat transfer rate, hence Nusselt number. An increase in the sweeping jet’s thermal inertia initiates an augmentation in heat transfer due to sweeping motion of the jet across the target surface. PIV data was acquired for two jet configurations, confined and unconfined, so that the recirculation behavior can be determined. The fluidic oscillator is found to improve only at a low z/d. At large z/d (greater than 4 in this study), the fluidic oscillator adversely affects the heat transfer.

Friction and Texture Retention of Concrete Pavements

2020 ◽  
Vol 2674 (6) ◽  
pp. 457-465
Author(s):  
Satyavati Komaragiri ◽  
Armen Amirkhanian ◽  
Amit Bhasin
Keyword(s):  
Coarse Aggregate ◽  
Concrete Surface ◽  
Concrete Pavement ◽  
Concrete Pavements ◽  
Department Of Transportation ◽  
Polishing Process ◽  
Friction Tester ◽  
Circular Track ◽  
Grinding Operations ◽  
Better Than

In the late 1980s and early 1990s, the Alabama Department of Transportation (ALDOT), U.S., noticed a decline in skid trailer numbers on concrete pavements shortly after grinding operations. The engineers at the time suspected that the coarse aggregate caused the decline in these numbers and the resulting conclusion led to a ban of carbonate aggregates in mainline concrete pavement in Alabama that is still in place. This detailed laboratory study re-examines the fundamental friction issues that led to this policy. A total of 48 aggregate, grinding, and grooving combinations were tested as part of this study. Three aggregate sources were examined: a siliceous source, a “hard” limestone source, and a “soft” limestone source. Two blade spacings were examined for grinding operations: 52 blades/ft and 60 blades/ft. Some ground specimens were also grooved. Finally, a set of specimens had the Next Generation Concrete Surface (NGCS) applied to them. The specimens were polished with the National Center for Asphalt Technology (NCAT) three-wheel polishing device (TWPD). The dynamic friction tester was used to evaluate friction values at various points through the polishing process. After the polishing, the macrotexture was characterized using the circular track meter. Across the board, the highest performing texture was that with no grooves and 52 blades/ft. Very generally, the loss of friction decreased with increasing siliceous content. However, some of the trends were extremely minor and, in a few cases, siliceous aggregates caused higher friction loss. There were numerous instances when blended carbonate/siliceous concrete pavement surfaces performed better than sole siliceous concrete pavement surfaces.

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