Oceanographic cruises in Pahang water in October 2003 and April 2004, monsoon transition months, produce data on water characteristics. The temperature in both months showed higher values in nearshore compared to the offshore stations. The nearshore salinity in both months is lower than offshore stations. Comparatively, there were smaller differences in temperature and salinity in October than in April, with very little variation between nearshore and offshore stations. T-S diagram showed significant differences between October and April water characteristics. According to the water characteristic observations, the temperature and salinity in October was lower than in April, while dissolved oxygen was higher than in April. The lower temperature and salinity taken during the sampling time in October suggested that during this time, the study area already received the influences of strong winds due to upcoming monsoon. The warmer and saltier water obtained in April showed that during this time, the study area was influenced by southwest monsoon. Winds related to rainfall were observed to have impact to the dynamics of water characteristics during both months.
The magnetohydrodynamic (MHD) boundary-layer flow and heat transfer due to a shrinking sheet in a porous medium is considered for the first time. The Navier-Stokes equations and the heat equation are reduced to two nonlinear ordinary differential equations via similarity transformations. The transformed equations are solved by a semi-analytic method. The effects of the suction and porosity parameters, the Prandtl and Hartmann numbers on the skin friction, heat transfer rate, velocity and temperature profiles are discussed and presented, respectively.
The paper is aimed at studying fluid flow heat transfer in the axisymmetric boundary layer flow of a viscous incompressible fluid, along the axial direction of a vertical stationary isothermal cylinder in presence of uniform free stream with momentum slip. The equations governing the flow i.e. continuity, momentum and energy equation are transformed into non-similar boundary layer equations and are solved numerically employing asymptotic series method with Shanks transformation. The numerical scheme involves the Runge-Kutta fourth order scheme along with the shooting technique. The flow is analyzed for both assisting and opposing buoyancy and the effect of different parameters on fluid velocity, temperature distribution, heat transfer and shear stress parameters is presented graphically.
In this study, the numerical solution of stagnation point flow over a stretching surface, generated by Newtonian heating in which the heat transfer from the surface is proportional to the local surface temperature is considered. The transformed boundary layer equations are solved numerically using the shooting method. Numerical solutions are obtained for the local heat transfer coefficient, the surface temperature and the temperature profiles. The features of the flow and heat transfer characteristics for various values of the Prandtl number, stretching parameter and conjugate parameter are analyzed and discussed.
We study and discuss the effect of thermal slip on steady free convection flow of a viscous, incompressible micropolar fluid past a vertical moving plate in a saturated porous medium. The effect of viscous dissipation is incorporated in the energy equation. The associated partial differential equations are transformed into a system of ordinary differential equations using similarity transformations generated by a group method and this system is then solved numerically. The effect of controlling parameters on the dimensionless velocity, angular velocity and temperature as well as friction factor, couple stress factor and heat transfer rate are shown graphically and discussed in detail. It is found that the dimensional velocity and angular velocity decrease whilst the temperature increases with velocity slip parameter. It is further found that thermal slip decreases the dimensional velocity and temperature but increases the dimensional angular velocity. Data from published work and our results are found to be in good agreement.
Waste furniture boards (WFBs) contain hazardous formaldehyde and volatile organic compounds when left unmanaged or improperly disposed through landfilling and open burning. In this study, pyrolysis was examined as a disposal and recovery approach to convert three types of WFBs (i.e., particleboard, plywood, and fiberboard) into value-added chemicals using thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG-FTIR) and pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS). TG-FTIR analysis shows that pyrolysis performed at an optimum temperature of 250-550 °C produced volatile products mainly consisting of carbon dioxide, carbon monoxide, and light hydrocarbons, such as methane. Py-GC/MS shows that pyrolysis at different final temperatures and heating rates recovered mainly phenols (25.9-54.7%) for potential use as additives in gasoline, colorants, and food. The calorific value of WFBs ranged from 16 to 18 MJ/kg but the WFBs showed high H/C (1.7-1.8) and O/C (0.8-1.0) ratios that provide low chemical energy during combustion. This result indicates that WFBs are not recommended to be burned directly as fuel, however, they can be pyrolyzed and converted into solid pyrolytic products such as biochar with improved properties for fuel application. Hazardous components, such as cyclopropylmethanol, were removed and converted into value-added compounds, such as 1,4:3,6-dianhydro-d-glucopyranose, for use in pharmaceuticals. These results show that the pyrolysis of WFBs at high temperature and low heating rate is a promising feature to produce value-added chemicals and reduce the formation of harmful chemical species. Thus, the release of hazardous formaldehyde and greenhouse gases into the environment is redirected.
The stakeholders' perceptions on the impacts of Urban Heat Island (UHI) are critical for reducing exposure and influencing their response to interventions that are aimed at encouraging a behaviour change. A proper understanding of the UHI impacts on the society, economy and environment is deemed an essential motivating factor for the stakeholders to work towards UHI mitigations in the local context. This study adopted an inductive qualitative approach using Stakeholder Dialogue Sessions (SDSs) to assess the perceived impacts of UHI among various stakeholders, comprising policy makers, academicians, developers and Non-Governmental Organizations (NGO), in a tropical metropolitan city. The results revealed five themes such as deterioration of public health, acceleration of urban migration patterns and spending time in cooler areas, reduction of workers' productivity, increased energy consumption by the households and deterioration of environmental quality and natural resources that were categorized into social, economic and environmental impacts. Although most of the stakeholders were quite unfamiliar with the term UHI, they still display a good understanding of the potential impacts of UHI due to their posteriori knowledge and ability to rationalize the physical condition of the environment in which they live. The findings provide useful insights and valuable information to the local authorities to tailor necessary actions and educational campaigns to increase UHI awareness among the stakeholders. Being among the earlier studies to use a qualitative approach to attain the aforementioned objective, the findings are crucial to determine the level of understanding of the stakeholders on the impact of UHI. Through this study, the authors have highlighted the gaps and needs for knowledge improvements aimed at behaviour change among the stakeholders.
Roasting of whole-kernels is an important step in the production of pistachio paste. The effect of hot air roasting temperatures (90-190°C) and times (5-65 min) on the hardness, moisture content and colour attributes (‘L’, ‘a’ and ‘b’ values and yellowness index) of both whole-kernel and ground-state were investigated using response surface methodology (RSM). Increases in roasting temperature and time caused a decrease in all the responses except for ‘a’ value of ground-state. The interaction and quadratic models sufficiently described the changes in the hardness and colour values, respectively. The result of RSM analysis showed that hardness and colour attributes (‘L’ and ‘b’ values, yellowness index) of kernels and ‘a’ value of ground-state could be used to monitor the roasting quality of whole-kernels. This study showed that the recommended range of roasting temperature and time of whole-kernel for the production of pistachio paste were 130-140°C and 30-40 min, respectively.
The impacts of low-transition-temperature mixtures (LTTMs) pretreatment on thermal decomposition and kinetics of empty fruit bunch (EFB) were investigated by thermogravimetric analysis. EFB was pretreated with the LTTMs under different duration of pretreatment which enabled various degrees of alteration to their structure. The TG-DTG curves showed that LTTMs pretreatment on EFB shifted the temperature and rate of decomposition to higher values. The EFB pretreated with sucrose and choline chloride-based LTTMs had attained the highest mass loss of volatile matter (78.69% and 75.71%) after 18 h of pretreatment. For monosodium glutamate-based LTTMs, the 24 h pretreated EFB had achieved the maximum mass loss (76.1%). Based on the Coats-Redfern integral method, the LTTMs pretreatment led to an increase in activation energy of the thermal decomposition of EFB from 80.00 to 82.82-94.80 kJ/mol. The activation energy was mainly affected by the demineralization and alteration in cellulose crystallinity after LTTMs pretreatment.
Matched MeSH terms: Temperature; Transition Temperature
Oil palm mesocarp fiber (OPMF) and palm frond (PF) were respectively devolatilized by pyrolysis to OPMF-oil and PF-oil bio-oils and biochars, OPMF-char and PF-char in a slow-heating fixed-bed reactor. In particular, the OPMF-oil and PF-oil were produced to a maximum yield of 48wt% and 47wt% bio-oils at 550°C and 600°C, respectively. The high heating values (HHVs) of OPMF-oil and PF-oil were respectively found to be 23MJ/kg and 21MJ/kg, whereas 24.84MJ/kg and 24.15MJ/kg were for the corresponding biochar. The HHVs of the bio-oils and biochars are associated with low O/C ratios to be higher than those of the corresponding biomass. The Fourier transform infrared spectra and peak area ratios highlighted the effect of pyrolysis temperatures on the bio-oil compositions. The bio-oils are pervaded with numerous oxygenated carbonyl and aromatic compounds as suitable feedstocks for renewable fuels and chemicals.
Durian shell (DS) was pyrolyzed in a drop-type fixed-bed reactor to study the physicochemical properties of the products. The experiment was carried out with different particle sizes (up to 5mm) and reaction temperatures (250-650°C). The highest bio-oil yield was obtained at 650°C (57.45wt%) with DS size of 1-2mm. The elemental composition and higher heating value of the feedstock, bio-oil (650°C), and bio-char (650°C) were determined and compared. The compositions of product gases were determined via gas chromatography with thermal conductivity detector. The chemical composition of bio-oil was analyzed by gas chromatography-mass spectrometry. The bio-oil produced at lower temperature yields more alcohols, whereas the bio-oil produced at higher temperature contains more aromatics and carbonyls. Bio-oil has potential to be used as liquid fuel or fine chemical precursor after further upgrading. The results further showed the potential of bio-char as a solid fuel.
Understanding the water sorption characteristics of cereal is extremely essential for optimizing the drying process and ensuring storage stability. Water relation of rough rice was studied at 20, 30, 40 and 50 °C over relative humidity (RH.) between 0.113 and 0.976 using the gravimetric technique. The isotherms displayed the general sigmoid, Type II pattern and exhibited the phenomenon of hysteresis where it was more pronounced at lower temperatures. The sorption characteristics were temperature dependence where the sorption capacity of the paddy increased as the temperature was decreased at fixed (RH). Among the models assessed for their ability to fit the sorption data, Oswin equation was the best followed by the third order polynomial, GAB, Smith, Chung-Pfost, and Henderson models. The monolayer moisture content was higher for desorption than adsorption and tend to decrease with the increase in temperature. Given the temperature dependence of the sorption isotherms the isosteric heats of sorption were calculated using Claussius-Clapeyron equation. The net isosteric heats decreased as the moisture content was increased and heats of desorption were greater than that of adsorption.
Matched MeSH terms: Cold Temperature; Hot Temperature; Temperature
This paper presents a numerical study of the thermal performance of fins mounted on the bottom wall of a horizontal channel and cooled with either pure water or an Al2O3-water nanofluid. The bottom wall of the channel is heated at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The results of the numerical simulation indicate that the heat transfer rate of fins is significantly affected by the Reynolds number (Re) and the thermal conductivity of the fins. The influence of the solid volume fraction on the increase of heat transfer is more noticeable at higher values of the Re.
Matched MeSH terms: Cold Temperature; Hot Temperature; Temperature
The title compound, 3,5,7-triaza-1-azoniatricyclo[3.3.1.1(3,7)]decane 2,4-dinitrophenolate monohydrate, C6H13N4+*C6H3N2O5-*H2O, the 1:1 hydrate adduct of hexamethylenetetramine (HMT) and 2,4-dinitrophenol, undergoes a temperature phase transition. In the room-temperature phase, the adduct crystallizes in the monoclinic P2(1)/m space group, whereas in the low-temperature phase, the adduct crystallizes in the triclinic P1 space group. This phase transition is reversible, with the transition temperature at 273 K, and the phase transition is governed by hydrogen bonds and weak interactions. In both these temperature-dependent polymorphs, the crystal structure is alternately layered with sheets of hexamethylenetetramine and sheets of dinitrophenol stacked along the c axis. The hexamethylenetetramine and dinitrophenol moieties are linked by intermolecular hydrogen bonds. The water molecule in the adduct plays an important role, forming O-H...O hydrogen bonds which, together with C-H...O hydrogen bonds, bridge the adducts into molecular ribbons. Extra hydrogen bonds and weak interactions exist for the low-temperature polymorph and these interconnect the molecular ribbons into a three-dimensional packing structure. Also in these two temperature-dependent polymorphs, dinitrophenol acts as a hydrogen-bond acceptor and HMT acts as a hydrogen-bond donor.
Matched MeSH terms: Cold Temperature; Temperature; Transition Temperature
Heat pipes are widely used in various industries such as automotive, electronics, and many more. Heat pipes are used as cooling devices for electronic parts in machines that emit a large amount of heat, which can damage the devices. The heat pipes used in this investigation are loop heat pipes. These pipes can transport heat over a long distance and operate against gravity. The working fluid used in this investigation is nanofluid. Nanofluid is one of the types of working fluid that is considered to have better thermal performance than conventional fluids. Nanofluid is made of nanoparticles with base-fluid. This investigation studies the thermal performance of loop heat pipes using different types of nanofluids. Nanofluid fluids used in this study are diamond nanofluid, aluminium oxide nanofluid and silica oxide nanofluid. The effect of mass concentration of nanoparticles in the base-fluid is also studied. The results showed that as the mass concentration of nanofluids increased, the thermal resistance for diamond nanofluid and aluminium oxide nanofluid decreased, but the opposite occurred for silica oxide nanofluid but still better resultsthan pure water. This shows that diamond and aluminium oxide nanofluids shows better thermal conductivity as it has lower total thermal resistance and thermal enhancement rate compared to other nanofluids. Diamond nanofluid also had higher heat capacity than aluminium oxide nanofluid as it had a lower vapour line temperature reading.
Matched MeSH terms: Cold Temperature; Hot Temperature; Temperature
External shading geometry on buildings has been found to contribute substantially to reducing energy consumption for cooling. This study examines the effect of inclined wall self-shading strategy on heat gain in an office building. Field measurement of environmental variables such as ambient temperature, relative humidity, dew point, and wet bulb temperature was carried out in a case study inclined wall self-shading office building located in Putrajaya, Malaysia. The results of the validation of ApacheSim simulation software tool against the measured environmental variables indicated significant reliability having Pearson correlations ranging from 0.56 to 0.90. In establishing the relationship between different inclined wall strategies to the amount of heat gain, modification of the inclined wall self-shading projection (SSP) was modelled and experimented using ApacheSim simulation. Findings from the analysis revealed a relationship between heat gains into a building space and self-shading projection (SSP), as heat gains tend to reduce with increased SSP. From the findings, the optimum inclination angle of self-shading for effective heat gain reduction is based on a 45% self-shading projection. The application of inclined wall self-shading strategy in buildings would, therefore, bring about a reduction in heat gain, which invariably reduces energy consumption for cooling.
Matched MeSH terms: Cold Temperature; Hot Temperature; Temperature
Kaolin, theoretically known as having low reactivity during geopolymerization, was used as a source of aluminosilicate materials in this study. Due to this concern, it is challenging to directly produce kaolin geopolymers without pre-treatment. The addition of ground granulated blast furnace slag (GGBS) accelerated the geopolymerization process. Kaolin-GGBS geopolymer ceramic was prepared at a low sintering temperature due to the reaction of the chemical composition during the initial stage of geopolymerization. The objective of this work was to study the influence of the chemical composition towards sintering temperature of sintered kaolin-GGBS geopolymer. Kaolin-GGBS geopolymer was prepared with a ratio of solid to liquid 2:1 and cured at 60 °C for 14 days. The cured geopolymer was sintered at different temperatures: 800, 900, 1000, and 1100 °C. Sintering at 900 °C resulted in the highest compressive strength due to the formation of densified microstructure, while higher sintering temperature led to the formation of interconnected pores. The difference in the X-ray absorption near edge structure (XANES) spectra was related to the phases obtained from the X-ray diffraction analysis, such as akermanite and anothite. Thermal analysis indicated the stability of sintered kaolin-GGBS geopolymer when exposed to 1100 °C, proving that kaolin can be directly used without heat treatment in geopolymers. The geopolymerization process facilitates the stability of cured samples when directly sintered, as well as plays a significant role as a self-fluxing agent to reduce the sintering temperature when producing sintered kaolin-GGBS geopolymers.
Matched MeSH terms: Cold Temperature; Hot Temperature; Temperature
In this article, we numerically investigate the influence of thermal radiation and heat generation on the flow of an electrically conducting nanofluid past a nonlinear stretching sheet through a porous medium with frictional heating. The partial differential equations governing the flow problems are reduced to ordinary differential equations via similarity variables. The reduced equations are then solved numerically with the aid of Keller box method. The influence of physical parameters such as nanoparticle volume fraction ϕ, permeability parameter K, nonlinear stretching sheet parameter n, magnetic field parameter M, heat generation parameter Q and Eckert number Ec on the flow field, temperature distribution, skin friction and Nusselt number are studied and presented in graphical illustrations and tabular forms. The results obtained reveal that there is an enhancement in the rate of heat transfer with the rise in nanoparticle volume fraction and permeability parameter. The temperature distribution is also influenced with the presence of K, Q, R and ϕ. This shows that the solid volume fraction of nanoparticle can be used in controlling the behaviours of heat transfer and nanofluid flows.
Matched MeSH terms: Body Temperature Regulation; Hot Temperature; Temperature
The problem of entropy generation analysis and natural convection in a nanofluid square cavity with a concentric solid insert and different temperature distributions is studied numerically by the finite difference method. An isothermal heater is placed on the bottom wall while isothermal cold sources are distributed along the top and side walls of the square cavity. The remainder of these walls are kept adiabatic. Water-based nanofluids with Al 2 O 3 nanoparticles are chosen for the investigation. The governing dimensionless parameters of this study are the nanoparticles volume fraction ( 0 ≤ ϕ ≤ 0.09 ), Rayleigh number ( 10 3 ≤ R a ≤ 10 6 ) , thermal conductivity ratio ( 0.44 ≤ K r ≤ 23.8 ) and length of the inner solid ( 0 ≤ D ≤ 0.7 ). Comparisons with previously experimental and numerical published works verify a very good agreement with the proposed numerical method. Numerical results are presented graphically in the form of streamlines, isotherms and local entropy generation as well as the local and average Nusselt numbers. The obtained results indicate that the thermal conductivity ratio and the inner solid size are excellent control parameters for an optimization of heat transfer and Bejan number within the fully heated and partially cooled square cavity.
Matched MeSH terms: Cold Temperature; Hot Temperature; Temperature
The electron-phonon coupling constant of the copper oxide-based high temperature superconductors in the van Hove scenario was calculated using three known models and by employing various acoustic data. Three expressions for the transition temperature from the models were used to calculate the constants. All three models assumed a logarithmic singularity in the density of states near the Fermi surface. The calculated electron-phonon coupling constant ranged from 0.06 to 0.28. The constants increased with the transition temperature indicating a strong correlation between electron-phonon coupling and superconductivity in these materials. These values were smaller than the values estimated for the conventional three-dimensional BCS theory. The results were compared with previous reports on direct measurements of electron-phonon coupling constants in the copper oxide based superconductors.
Matched MeSH terms: Hot Temperature; Temperature; Transition Temperature