Heat Flow Profiles Research Articles

Numerical energy and entropy analyses of a tube with wavy tape insert including CoFe2O4/water nanofluid under laminar regime

The primary objective of this investigation is to assess the impact of vortex generator geometry and nanofluid on thermohydraulic and irreversibility characteristics within a laminar flow regime. The study introduces an original CoFe2O4/H2O (1 % vol.) nanofluid and employs a wave tape insert to induce forced convection in a tube, accompanied by first and second-law thermodynamic analysis. The novelty of this research lies in the numerical exploration of heat transfer and flow profiles for a nanofluid in a tube, varying the wave rate (y = 4-5-6). The investigation considers the laminar model and single-phase approach in all analyses under constant heat flux (q” = 2000 W/m2). The study observed that the nanofluid flowing in the tube with a wave ratio of 4, 5, and 6 resulted in an average enhancement in the Nusselt number of 93.25 %, 86.26 %, and 80.06 %, respectively. The optimal performance evaluation criterion (PEC) for water flowing in the tube with a wave ratio of 6 at Re = 500 exhibited an increase of 11.0 %, whereas the CoFe2O4/H2O flow showed a 9.14 % increment in the average PEC along the Reynolds number. Moreover, the total entropy generation values for water flowing in tubes with wave ratios of 5, 6, and 4 exhibited increases of 101.88 %, 94.66 %, and 51.34 %, respectively, in comparison to the smooth tube.

Performance analysis of deep borehole heat exchangers for decarbonization of heating systems

AbstractMeeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector. Heat pumps with deep borehole exchangers are a promising solution to reduce emissions. Here the thermal behavior of deep borehole exchangers (DBHEs) ranging from 1 to 2 km was analyzed for various heat flow profiles. A strong correlation between thermal energy extraction and power output from DBHEs was found, also influenced by the heating profile employed. Longer operating time over the year typically resulted in higher energy production, while shorter one yielded higher average thermal power output, highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs. Short breaks in operation for regenerating the borehole, for example, with waste heat, proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat. The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space. As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year, the technology is best suitable for larger heat loads.

Comparative analysis of thermal stability and electrochemical performance of NaNi1/3Fe1/3Mn1/3O2 cathode in different electrolytes for sodium ion batteries

The electrochemical compatibility and thermal stability of cathode and electrolyte guarantee the intrinsic safety of batteries. The NaNi1/3Fe1/3Mn1/3O2 (NaNFM) cathode for sodium ion batteries (SIBs) has not received, sufficient attention concerning its thermal safety compared to its electrochemical properties. Herein, we investigated the thermal stability of NaNFM, exothermic reaction and electrochemical performance of NaNFM with various electrolytes. The comprehensive electrochemical performance of NaNFM in different electrolytes followed this sequence: sodium hexafluorophosphate (NaPF6) > sodium bis(trifluoromethyl-sulfonyl)imide (NaTFSI) > sodium perchlorate (NaClO4)- based electrolytes. Additionally, ethylene carbonate (EC): propylene carbonate (PC)- type electrolytes displayed superior cycling stability compared to ethylene carbonate (EC): diethyl carbonate (DEC)- type electrolytes. Moreover, the heat flow profiles demonstrated that the thermal stability between NaNFM and various electrolytes could be ordered according to the total heat release as: NaClO4 < NaPF6 < NaTFSI-based electrolyte. X-ray diffractometer (XRD), scanning electron microscope (SEM) and x-ray photoelectron spectrometer (XPS) analyses were carried out to investigate the changes in crystal structure, morphology and valence state of thermal reaction products after microcalorimetric analysis experiments. These findings provide valuable insights for the safe application of the NaNFM cathode in SIBs.

Artificial intelligence approach for energy and entropy analyses of NiFe2O4/H2O nanofluid flow in a tube with vortex generator

The base purpose of the study is to examine the influence of vortex generator geometry and nanofluid on thermo-hydraulic and irreversibility behavior by using a numerical and predictable approach under a laminar flow regime. The selection of an original magnetic nanofluid, the handling of forced convection in a tube including a vortex generator with the artificial neural network approach, and the 2nd law analysis of thermodynamics reflect the novelty of the study. In this context, it was explored numerically for heat transfer and flow profiles of NiFe2O4/H2O flowing with 1% volume fraction in a tube with different vortex generator geometries. This study has been carried out with the solutions under constant heat flux conditions of 2000 W/m2 along the tube. The analyzes have been applied in the range of 500≤Re≤2000. The Laminar model and single-phase approach in all analyses have been taken into account. Heat convection coefficient, pressure drop, and entropy generation were analyzed for the smooth tube and tube with wave ratio (WR=h/w) of 2, 3, and 4. Levenberg-Marquardt as train algorithm and Learngdm and Tansig as transfer function was used as the MLP network model in the present study. As a result, The highest heat transfer ratio, pressure drop, frictional entropy, and total entropy values are obtained for the tube with a wave ratio of 2. The highest deviation rates between the predicted and numerical results for WT1 and WT2 cases (the supreme among all cases) have been seen as 4.67% and 1.73% for the heat convection coefficient and pressure drop values, respectively.

Time-Resolved Electrochemical Heat Flow Calorimetry for the Analysis of Highly Dynamic Processes in Lithium-Ion Batteries

Isothermal microcalorimetry is used to study the heat flow of lithium-ion cells to provide insight into active material characteristics and to provide data required for a thermal optimization on the cell and system level. Recent research has shown the application of this technique to cells during high cycling rates, for example fast charging. However, the limitation of isothermal microcalorimetry is the low-pass characteristic of the measured heat flow, introduced by the thermal inertia of the setup and the calorimeter itself. To solve this problem, we introduce an optimized cell holder design and a novel data processing method for a time-resolved measurement of highly dynamic heat flow profiles. These are described in detail and validated using a synthetic power profile applied to a dummy cell. Experiments on a graphite-lithium half-cell illustrate the improvement of the method and the optimized cell holder when compared to the state-of-the-art setup, demonstrating the 3.6 times faster time response, which was further improved using a post-processing deconvolution technique. The thus improved time resolution provides the acquisition of more detailed features than currently shown in the literature and allows an accurate correlation of the thermal signals to electrochemical features like, e.g., the differential voltage of the cell.

Effects of Baffle Height and Baffle Location on Heat Transfer and Flow Profiles in a Baffled Duct: A CFD Analysis

CFD analysis of flow and heat transfer characteristics in a baffled duct is reported. The baffle locations ( s = 0.05 H – 0.40 H ), flow paths (V-apex directing Downstream or VD and V-apex directing Upstream or VU), and baffle heights ( b = 0.05 H – 0.30 H ) are investigated in the laminar flow regime with the Reynolds number based on the entry conditions between 100 and 2,000. Solutions of the present work are obtained by the finite volume method (a commercial code). Key mechanisms such as fluid streams, impinging streams, and disturbed thermal boundary layer in the baffled duct are observed. The baffle locations have high impact on flow and heat transfer behavior. The best heat transfer rate of the baffled duct is 15.55 times higher than that of the general duct with no baffle, while the optimum TEF is 4.06.

Heat flow and 2D multichannel seismic reflection survey of the Devil's Hole geothermal reservoir in the Wagner basin, northern Gulf of California

The Wagner basin, located in the northernmost Gulf of California, hosts a large reservoir with geothermal potential documented in recent heat flow surveys. Although there is evidence of heat generation above the average value for an oceanic crust in the Wagner basin, it is unclear what the heat source is. To better understand the thermal structure in the northern Gulf of California, we acquired four 2D multichannel seismic reflection profiles and two systematic heat flow profiles across the Wagner basin. The survey targeted a geothermal anomaly, which we denominated “Devil's Hole” in a clear reference to pockmarks on the seafloor, and very high heat flow values. The heat flow profiles are ∼12 and ∼9 km long, are sub perpendicular to each other, have a nominal measurement spacing of ∼1 km, and were located along the transects of two of the four seismic reflection profiles. The two remaining seismic profiles are ∼34 and ∼40 km long, respectively, and are oriented SWW-NEE. To obtain seismic images, we used a conventional seismic processing workflow. After heat flow data correction, the minimum, maximum, and standard deviation of heat flow values for the Wagner basin are 295±42 and 10,894±114 mW/m2. We interpret the relatively high heat flow and large variability in the central part of the acquired profiles is caused by upward fluid flow at the Wagner fault zone. In contrast, the lower heat flow in the western flank of the basin suggest conductive heat transfer given the absence of faults. Based on these observations, we develop a geological model in which venting is not the product of a nascent spreading center as other authors have suggested. Instead, hydrothermal activity appears to result from isolated thermal plumes, rising from the base of the sedimentary column, captured by permeable fracture systems.

Design of a Stable Coamorphous System Using Lactose as an Antiplasticizing Agent for Diphenhydramine Hydrochloride with a Low Glass Transition Temperature.

Coamorphous systems comprising small molecules are emerging as counterparts to polymeric solid dispersions. However, the glass transition temperatures (Tgs) of coamorphous materials are relatively low because of the lack of polymeric carriers with higher Tgs. This study aimed to investigate the applicability of lactose (LAC) as an antiplasticizing coformer to a coamorphous system. Diphenhydramine hydrochloride (DPH) was selected as a model drug (Tg = 16 °C). Differential scanning calorimetry showed a comelting point in addition to a decrease in the neat melting points depending on the composition of the physical mixtures, suggesting that the mixture of DPH-LAC was eutectic. The melting point of the eutectic mixture was calculated according to the Schröder-van Laar equation. The heat of fusion of the eutectic mixture was maximized at a 70:30 molar ratio of DPH to LAC; at this point, the melting peaks of the pure components disappeared. The heat flow profiles following the melting and cooling of DPH-LAC physical mixtures at the ratios from 10:90 to 90:10 showed a single Tg, suggesting the formation of a coamorphous system. Lactose showed a Tg of over 100 °C, and the Tg of DPH increased with the molar ratio of LAC; it was 84 °C at a 10:90 molar ratio of DPH to LAC. The Raman image indicated the formation of a homogeneous dispersion of DPH and LAC in the coamorphous system. Peak shifts in the infrared spectra indicated the presence of intermolecular interactions between the amino group of DPH and the hydroxyl group of LAC. Principal component analysis of the infrared spectra revealed a significant change at the 70:30 molar ratio of DPH to LAC, which was in agreement with the results of the thermal analysis. A stability test at 40 °C revealed rapid crystallization of the supercooled liquid DPH. The coamorphous samples containing 10-50% of LAC remained in an amorphous state for 21 days, and no crystallization was observed for the samples containing >60% of LAC for 28 days. The relatively lower Tg (less than 40 °C) of the coamorphous system containing 10-50% of LAC might have caused crystallization during storage. These findings indicate that LAC, which is a safe and widely used pharmaceutical excipient, can be applied to coamorphous systems as an antiplasticizing coformer.

Analysis of heat fluxes in ceramic block type building pieces

In Norte de Santander, Colombia, there is a ceramic cluster made up of 59 companies dedicated to the production of construction materials derived from clay, a vernacular material with a wide extraction potential in the region. Fired clay products in different hollow block presentations represent 15% of industrial production, these construction pieces are low cost and show a high demand in the local masonry market, therefore, their thermo-physical characteristics largely build the thermal envelope of “Cucuteña”. This research comparatively evaluates the thermal behavior of four types of ceramic blocks with different perforations, applying the finite element method in thermal simulations that consider a conductivity of 0.407 W/m°C in the ceramic to establish the influence of the shape on the temperature distribution and heat flow profiles of each piece subjected to environmental conditions of a warm semi-arid climate, with average maximum temperatures of 33 °C and an average maximum solar radiation of 796.8 Wh/m2 under extreme climatic conditions in the city of San Jose de Cúcuta, Colombia. The results of the study allow identifying the ceramic block of 6 rectangular holes as the product that, due to its physical characteristics, presents a better alternative to be applied in constructions that seek thermal efficiency.

Study on thermal stability and thermal decomposition mechanism of 1-((cyano-1-methylethyl) azo) formamide

1-((Cyano-1-methylethyl) azo) formamide (CABN) is an azo initiator that has the inherent property of being decomposed at high temperatures with considerable amounts of heat generated. The thermal hazard of CABN is the main consideration in the occurrence of serious accidents. In this study, differential scanning calorimetry (DSC) was used to obtain the heat flow profiles and thermodynamic parameters of pure and impure CABN at various heating rates. The gaseous products and decomposition residues corresponding to each mass loss stage of CABN were judged by a thermogravimetry-mass spectrometer (TG-MS) and infrared spectrometer (IR). The optimal thermal decomposition reaction path of CABN was simulated and determined by the Gaussian software. The Materials Studio software was used to simulate the front-line orbits and energy gaps of CABN and its mixture to determine the influence of impurities on the thermal stability of CABN. Above results showed that the addition of the impurities caused an increased thermal decomposition risk of CABN. N2, CO, CO2, CH4N2O, 2-aminoisobutyronitrile, and isobutyronitrile were the potential products as a result of the thermal decomposition of CABN. The results of this study are expected to provide the fundamentals for safely handling CABN in preparation, production, transportation, and storage purposes.

A simple method to create hydrophobic mortar using bacteria grown in liquid cultures

The ingress of water-soluble aggressive species is a major cause to the reduced service life of concrete structures. Bulk modification by adding hydrophobic agents in the cementitious materials is commonly applied to reduce water penetration into the concrete matrix. However, conventional hydrophobic modifications of concrete are associated with several unresolved major drawbacks such as high cost and toxicity. Here, we investigate the impact of safe and easy-to-culture bacteria on the hydrophobic properties of concrete. We demonstrate that hydrophobic concrete can be conveniently created by using the liquid culture of bacteria without the need of growing biofilms as suggested by previous research, even with a strain that does not present innate hydrophobicity. These key findings greatly improve the feasibility for the large-scale application of water resistance cementitious materials. Scanning electron microscopy and X-ray diffraction analyses indicated higher levels of micro-calcite formations with the increased addition of bacteria. These micro-calcite structures account for the dramatic increase in surface roughness which leads to elevated hydrophobic properties of the hybrid concrete. This phenomenon is reminiscent of the “lotus-leaf effect”, with ultrahydrophobicity arising from the nano- and microscopic topologies of surfaces. Bacteria-modified cement presents distinct heat-flow profiles during hydration consistent with the increased calcite formation. Taken together, this research gives unprecedented mechanistic insight into the design of microbial-modified concrete with hydrophobic properties particularly useful in floating and offshore structures. Given the large repertoire of bacteria still to be used, our work sets the stage for the future design of microbial-based hydrophobic concrete that can be tailored with additional functions such as self-healing and odor removal.

Flexible hybrid solid electrolyte incorporating ligament-shaped Li6.25Al0.25La3Zr2O12 filler for all-solid-state lithium-metal batteries

In this study we used a solution-casting method to fabricate a hybrid solid electrolyte (HSE) membrane based on a poly(vinylidene fluoride–co–hexafluoropropylene)/polyacrylonitrile (PVDF-HFP/PAN) polymer blend loaded with an interconnected ligament–shaped Li6.25Al0.25La3Zr2O12 (Al-doped LLZO) filler and applied it in all-solid-state lithium-metal batteries (ASSLMBs). The as-prepared HSE containing the optimized quantity of Al-doped LLZO@PVDF-HFP/PAN/LiClO4/succinonitrile filler displayed high ionic conductivity (1.12 × 10–4 S m–1 at 25 °C), a wide electrochemical stability window [up to 4.2 V (Li/Li+)], and a high transference number (0.42). A full cell based on the composite cathode NCM811 (LNi0.8Co0.1Mn0.1O2, c-NCM811)/HSE/Li had a highest discharge specific capacity of 160.92 mA h g–1 at 0.1 C and a capacity retention of 92.52% after 100 cycles; at 0.2 C, these values were 144.70 mA h g–1 and 85.72% (after 100 cycles), respectively. The Li+ diffusion coefficient of the c-NCM811/HSE/Li cell was one order of magnitude higher than that of the corresponding cell having a bare cathode (b-NCM811/HSE/Li) as well as c-NCM811/SPE+10%SN/Li. We used a multiple-mode calorimetry device to investigate the in situ heat flow profiles of c-NCM811/HSE/Li, c-NCM811/SPE/Li, and b-NCM811/HSE/Li cells; the c-NCM811/HSE/Li cell exhibited the lowest heat profile. Thus, ASSLMBs featuring the NCM811 composite cathode and this as-prepared HSE have great potential for use in applications requiring batteries of high energy density.

A new fractional exothermic reactions model having constant heat source in porous media with power, exponential and Mittag-Leffler laws

The present article deals with the exothermic reactions model having constant heat source in the porous media with strong memory effects. The Caputo, Caputo-Fabrizio and Atangana-Baleanu fractional operators are used to induce memory effects in the mathematical modeling of exothermic reactions. The patterns of heat flow profiles are very essential for heat transfer in every kind of the thermal insulation. In the present investigation, we focus on the driving force problem due to the fact that temperature gradient is assumed. The mathematical equation of the problem is confined in a fractional energy balance equation (FEBE), which furnishes the temperature portrayal in conduction state having uniform heat source on steady state. The fractional Laplace decomposition technique is utilized to obtain the numerical solution of the corresponding FEBE describing the exothermic reactions. Some numerical results for the fractional exothermic reactions model are presented through graphs and tables.

Structure of planar shock waves in gaseous mixtures based on ab initio direct simulation

The structure of planar shock wave propagating through a helium–argon mixture is modeledby the direct simulation Monte Carlo (DSMC) method based on ab initio potentials for a wide range of the Mach number and for various molar fractions. The use of ab initio potentials allows us to carry out the simulation without any adjustable parameter usually extracted from experimental data. As a result, the density, temperature, molar fraction, diffusion velocity, pressure tensor and heat flow profiles inside of the shock wave are calculated. The temperature overshoot phenomenon is discussed in details. The slopes of density are calculated with the numerical error less than 0.5 %. It is pointed out that the slopes for mixture are always smaller than those for a single gas.

Kinetic and safety parameters of decomposition of neat Tert-Butyl (2-Ethylhexyl) monoperoxy Carbonate and in organic solvents

The thermal decomposition reaction of tert-butyl (2-ethylhexyl) monoperoxy carbonate (TBEC) was studied in solution with different solvents (anisole, xylene and ethylbenzene) and alone. The kinetics of each system was explored by DSC measurements in isothermal and non-isothermal conditions. Analysis of heat flow profiles released in the isothermal mode combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer allowed to propose a chemical decomposition model. An empirical nth order rate equation was used to describe the decomposition of neat TBEC. In pure solvent the mechanism was modeled by two parallel reactions. The first one followed an empirical nth order rate equation. The second one was modeled by a transfer reaction of the radical to the solvent. An adiabatic calorimeter was used to identify the effects of solvents on important reactive hazards such as onset temperature, pressure hazard and the Time to maximum rate (TMRad) or temperature at which TMRad is 24h (TD24). The last parameter was compared with that estimated by DSC study. The kinetic parameters estimation was achieved using a mixed estimation method where a genetic algorithm is combined with a locally convergent method.

Subsurface Temperature Modeling using Integrated Modeling for Nuclear Reactor Site Assessment in Volcanic Zone

Indonesia has giant vulcanic arc that almost the largest vulcanic arc in the world. Therefore, one of the main risk for nuclear site plan is the vulcanic area. Therefore to reduce the risk, one of most safety nuclear site plant is old vulcanic area. In this paper, we propose to predict subsurface temperature profile to ensure the condition of subsurface of vulcanic zone. Geothermal heat flow is important parameter in modeling of subsurface temperature. The subsurface temperature is one of vulcanic activity parameter which very important for nuclear site plant risk assesment. The integrated modeling for predicting subsurface temperature profile is carried out by combining geothermal heat flow and subsurface profiles resulted from either seismic or gravity measurement. The finite difference of Fourier’s law is applied to surface temperature, temperature gradient, geothermal heat flow and thermal conductivity profile for producing subsurface temperature distribution accurately. This subsurface temperature profile is essential to characterize the vulcanic zone whether it is still active or inactive. Characterization of vulcanic activity is very useful to ensure or to minimize the risk of nuclear site plant in vulcanic zone. One of interesting case study of nuclear site plan in Indonesia is mount Muriah site plan, this method is useful to ensure whether mount Muriah is still active or inactive now

Hot and cold subduction systems in the Western Pacific Ocean: insights from heat flows

AbstractWe calculate a predicted interpolating result of surface heat flow based on a data set with 2674 measurements in the Western Pacific. Comparisons of heat flow profiles between the back‐arc basin and the corresponding subduction slab show that the cold subducting slab may cause indirectly the thermal activities of back‐arc basins. We estimate that values of &lt;50 mW/m2 for both the Philippine Sea Plate and the Pacific Plate may respectively cause the thermal activity of the Okinawa Trough and the Kuril Basin. Moreover, cold subduction may release carbonatitic liquid at different depths, and the process of releasing liquid ends up with the maximum range of serpentinization. The hot subduction system has released most of the water before being incorporated into the mantle wedge; therefore, at great depths, the amount of carbon may dominate the subducting process by controlling partial melting. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Inferring the role of NiO nanoparticles from the thermal behavior of virgin and adsorbed hydrocarbons

Simultaneous analysis of differential thermogravimetry (DTG) and differential scanning calorimetry (DCS) data is the key for identifying probable reactions and extracting their kinetic parameters under isothermal and non-isothermal conditions. However, an assumption of kinetically controlled thermal behavior needs to be adequately examined. Mass transfer limitations as well as multiple reactions of multiple species may be encountered while studying the thermal behavior of virgin and adsorbed crude oils. This, in turn, leads to uncertainties on the actual role of the adsorbent. In this paper we address these challenges and reflect on recent publication by Nassar et al. (2013) pertaining to catalyzed oxidation of adsorbed asphaltenes onto NiO nanoparticles. More specifically, we show that accounting for mass loss due to the adsorbent nanoparticles increases the value of the activation energy and, subsequently, influences conclusions on the role of the nanoparticle. In addition, we show that, for a given temperature zone, presenting heat flow profiles per gram of mass lost within that zone provides more reliable comparison between the size of reaction peaks. Finally, we address the heat treatment of oil and its effect on the adsorbed species, and explore the role of surface exposure and the interaction between the nanoparticles and the heavy oil fractions.

Thermal decomposition kinetic of 1,1-di(tert-butylperoxy)cyclohexane in organic solvents

Abstract The thermal decomposition reaction of 1,1-di(tert-butylperoxy)cyclohexane (BPCH) was studied in pure solvents (anisole, xylene and ethylbenzene) and alone. The kinetics of each system was explored by means of microcalorimetric measurements (DSC) in isothermal and non-isothermal conditions. Analysis of heat flow profiles released in the isothermal mode combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer allowed to propose a chemical decomposition model. An empirical n th order rate equation was used to describe the decomposition of BPCH alone. In pure solvent, the mechanism was modeled by two parallel reactions. The first one followed an empirical n th order rate equation. The second one was modeled by a transfer reaction of the radical to the solvent. The kinetic parameters estimation was achieved using a mixed estimation method where a genetic algorithm is combined with a locally convergent method.

Earthquake and Geothermal Energy

The origin of earthquake has long been recognized as resulting from strike-slip instability of plate tectonics along the fault lines. Several events of earthquake around the globe have happened which cannot be explained by this theory. In this work we investigated the earthquake data along with other observed facts like heat flow profiles etc…of the Indian subcontinent and found a high-quality correlation among the various indicators, like the earthquake events, seismic prone zones, heat flow regions and the geothermal sites. As a consequence, we proposed a hypothesis which can adequately explain all the earthquake events around the globe as well as the overall geo-dynamics. It is basically the geothermal power, which makes plate tectonics to stand still, strike and slip over. The plates are merely a working solid while the driving force is the geothermal energy. The non-utilized accumulated geothermal power shakes the earth along the plate boundaries and also triggers the intra-plate seismicity. In the light of the results reported by the California Energy Commission from the ongoing geothermal power project at the Big Geysers in California, we further propounded that by harnessing the surplus geothermal energy the intensity and risk of the impending earthquakes can be substantially reduced.