Comparison Of Thermal Performance Research Articles

Numerical comparison of thermal energy performance between spouted, fluidized and fixed beds using supercritical CO2 as fluidizing agent

The different thermal energy performance between spouted, fluidized, and fixed beds when using supercritical CO2 as a fluidizing agent was numerically investigated by employing a combined approach of Computational Fluid Dynamics (CFD) and Coarse-Grained Particle (CGP) methods. The model was first validated against experimental data available in the literature, confirming that the simulated particle velocity and temperature agreed well with the experimental measurements. The numerical results reveal that for the spouted bed, gas velocity, gas temperature, and convective heat transfer were higher in the spout region. Hence, most heat was transported directly from the inlet to the outlet of this system. For the fluidized bed, the particles near the gas inlet were quickly heated up at first, and a uniform temperature distribution was achieved in the whole bed during the later stages of the process. Concerning the fixed bed, its behavior is well-known with three temperature zones differentiated, which are a hot region, a cold zone, and the intermediate thermocline. Besides, numerical simulations allow further analysis in detail of the different heat transfer mechanisms in the configurations tested. Convection is the dominant mechanism in all cases. Conduction is noticeable in the fixed bed regime compared to the spouted or fluidized regimes, but even in this case, it is still an order of magnitude lower than the convection mechanism. Finally, thermal energy and exergy were also analyzed for the three beds.

Performance Investigation of Cylindrical Cavity Receiver Using Roughened Surfaces

Solar cavity receiver is an integral part of the solar parabolic dish collectors used for absorbing concentrated solar irradiation. The performance of the receivers can be enhanced utilizing different types of heat transfer fluids (HTF) and modified geometries. The thermal performance of a redesigned cavity receiver with solid semi-circular tube attached to its surface was investigated using CFD three-dimensional simulation. The influence of operating and geometric parameters (i.e., inlet mass flow rate and inlet temperature) were investigated. The results obtained shows that, redesigned solar cavity receiver has thermal efficiency of 8.49-10.27% higher than a normal cavity receiver with an inlet flow rate of 0.01-0.04 kg/s under the same environmental and operating conditions. The temperature of outlet of HTF increases with increases in inlet temperature for Therminol66 oil. The comparison of thermal performance using different HTF (i.e., Therminol66, Ethylene Glycol, Water) is also conducted and it is found that Therminol66 oil gives 9% and 17% higher outlet temperature than ethylene glycol and water respectively at intake flow rate of 0.02 kg/s.

Performance comparison appraisal of a fully wetted longitudinal fin of different profiles with variable thermal conductivities

The goal of this study is to examine the thermal performance and the flow of hybrid nanofluid over three types of longitudinal wetted fins encompassing thin tip fin, thick tip fin, and fin with a rectangular shape. It is pertinent to mention that both thin and thick tip fins are of exponential profile. The longitudinal fins are of variable thickness with stagnant, stretching, and shrinking cases in a fully wetted circumstance to study the heat augmentation of a conveyer belt. The previous studies considered constant temperature but, in this analysis, the variable type (temperature-dependent) i.e., exponential and linear forms of thermal conductivities are cogitated for all three cases. A comparison of thermal performance is also elaborated for variables thermal conductivities considering the above-cited three cases. The analysis would be more useful in the designing of fin structures that are helpful to enhance thermal efficiency. This is a pioneering study in this direction. The mathematical model is elucidated numerically. The impact of arising pertinent parameters is arbitrated. It is examined that inverted and rectangular fins possess more heat transfer rate in comparison to the tapered fin. Furthermore, the surface temperature of the stretching fin is higher than the shrinking fin.

Comparison of thermal performances of plywood shear walls produced with different thermal insulation materials

Comparison of thermal performances of plywood shear walls produced with different thermal insulation materials

Application of thermal and visible imaging to estimate stripe rust disease severity in wheat using supervised image classification methods

Reliable and accurate estimation of plant disease severity at the field scale is a key factor for predicting yield losses, disease management and food security. A field experiment was designed and conducted during 2017–18 and 2018–19 with 24 wheat cultivars to estimate the stripe rust severity by supervised classification of thermal and visible images using parallelepiped, minimum distance, mahalanobis distance, maximum likelihood, support vector machine and neural network methods of image classification. Results demonstrated the potential of thermal and visible imaging techniques to estimate wheat stripe rust severity with good accuracy. For both visible and thermal images used in this study, support vector machine gave the best estimates of the rust severity, while the parallelepiped method was the worst-performing method. Support vector machine and neural network methods showed d-index, Nash-Sutcliffe efficiency and coefficient of determination values above 85%, with accuracies above 98% and kappa coefficient above 0.97 for both thermal and visible images. Comparison of thermal and visible image classification performance revealed that for all the methods except support vector machine, the estimated rust severity, overall accuracy and kappa coefficient of thermal images were better than visible images. The present study clearly showed that both thermal and visible image analysis can be applied as a rapid non-destructive technique to estimate the wheat rust severity under field conditions. The study also provided a comparative insight into thermal and visible image classification methods that have great potential for sustainable plant disease management in modern agriculture.

Comparative study on the thermal performance and economic efficiency of vertical and horizontal ground heat exchangers

The ground-coupled heat pump is a shallow geothermal exploitation method taking soil as the thermal energy source. The ground heat exchanger is an important component of this system, which includes vertical or horizontal configurations. However, to the best of our knowledge, few studies exist involving the comparison of thermal performances and installation costs of two heat exchanger types considering the influence of ground climate, which makes the selection of heat exchanger configuration challenging for a specific field application. Hence, a 3-dimensional numerical model considering the variations of atmospheric conditions and soil water content is constructed in this paper. Based on this model, the thermal performances and economical efficiencies of vertical and horizontal ground heat exchangers are compared. The results indicate that the thermal performance difference between the two heat exchangers is greater in winter than in summer. The thermal performance is hardly influenced by the injection mass flow rate, while it is considerably affected by the length of heat exchanger. The thermal power rises linearly with the increase in heat exchanger length, and the increment of the vertical ground heat exchanger is higher. In addition, when the heat exchanger length is shorter than 40 m, the installation cost and thereby the total cost of the horizontal ground heat exchanger is considerably higher. With regard to both the thermal performance and economic efficiency, a vertical ground heat exchanger is only recommended when installing a single shallow ground heat exchanger. Cited as: Cui, Q., Shi, Y., Zhang, Y., Wu, R., Jiao, Y. Comparative study on the thermal performance and economic efficiency of vertical and horizontal ground heat exchangers. Advances in Geo-Energy Research, 2023, 7(1): 7-19. https://doi.org/10.46690/ager.2023.01.02

Thermal performance investigation of energy storage based U-pipe evacuated tube solar collector: An experimental study

In this study thermal performance comparison of a custom made U-Pipe evacuated tube solar collector (ETC) vs commercially available heat pipe ETC (HPETC) was investigated experimentally. The performance comparison was performed over several days with and without thermal storage media. Results from testing without thermal storage media showed U-Pipe ETC achieved higher peak water temperatures than that of HPETC, maximum of 31 °C, resulting in 13% efficiency enhancement of U-Pipe ETC compared with HPETC. Results from testing with storage materials showed peak temperatures for fin and water tank of the U-Pipe ETC as 47 °C and 38.7 °C, respectively, whereas heat pipe showed values of 60 °C and 36.7 °C for max fin and water temperatures, respectively. Further performance enhancement to the U-Pipe ETC system was investigated through integration of phase change material (PCM)72 with added 1wt% multi-walled carbon nanotubes (MWCNT) nanoparticles. Peak temperatures recorded for this experiment were 63.9 °C and 43.3 °C for the U-Pipe fin and water tank, respectively. The results from this study show that the U-Pipe setup was able to achieve higher water temperatures than that of the HPETC setup. Incorporation of nano-PCM allowed for slower heat release in the water, extending useful duration of latent heat storage capability.

Monitoring and Calculation Study in Mediterranean Residential Spaces: Thermal Performance Comparison for the Winter Season

In cold regions, the reduction in envelope thermal transmittance is often the dominant parameter in ensuring thermal comfort in buildings. However, countries in warmer climates have also adopted this same strategy, often neglecting other parameters that are more influential in their respective climate regions that can achieve thermal comfort. This study focuses on passive building strategies to ensure a building’s thermal comfort conditions in Mediterranean climates in the winter. This monitoring study compares two dwellings during the winter in Barcelona, Spain, in order to analyze the impact of not only the envelope’s thermal properties on indoor temperature, but also the role of other factors such as outdoor temperature and solar gains. The dwellings were built in different decades, each following distinct building technical codes, diverse construction techniques, and building materials. The methodology used in this study is based on thermal measurements, meteorological data, and spreadsheet calculations. Comparing these results with the recent updates in Spain’s technical code and other studies, the investigation demonstrates that to achieve a suitable indoor thermal temperature in a passive way, especially in Mediterranean climates, incorporating other factors such as the combination of thermal inertia and solar gains can be more effective than a strategy mainly focused on reducing thermal transmittance. This analysis demonstrates that a building’s thermal performance does not mainly depend on envelope thermal transmittance, but rather a complex system involving a set of variables such as thermal inertia as well as solar gains, based on parameters such as building orientation and urban context.

Comparison of thermal performance between fly ash geopolymer and fly ash-ladle furnace slag geopolymer

This paper compared the thermal stability between fly ash (FA) and fly ash-ladle furnace slag (FA-LS) geopolymers. FA-LS geopolymer was prepared by mixing FA and LS (FA:LS weight ratio of 80:20) with an alkali activator. Geopolymers were aged at room temperature for 28 days before being exposed to high temperatures (200 °C – 1000 °C). Unexposed FA and FA-LS geopolymers had a compressive strength of 38.9 MPa and 40.5 MPa, respectively. The FA and FA-LS geopolymers retained 61.6% and 91.3% compressive strength, respectively, when exposed to temperatures up to 1000 °C. FA-LS geopolymers experienced smaller variation in the density (2.6 – 5.5%) and pores (17.4 – 23.0%) compared to FA geopolymers (density and porosity of 2.9 – 25.2% and 19.0 – 30.0%, respectively). The formation of crystalline peaks, densification of matrix, pores and their connectivity, cracks and dimensional changes influenced the compressive strength of exposed geopolymers. FA-LS geopolymers could be potentially applied as heat-resistance material.

Comparison of thermal performance of steel moment and eccentrically braced frames

Eccentrically braced frames (EBFs) are typically employed in seismic design because they integrate the benefits of concentrically braced frames and moment-resisting frames, providing both high elastic stiffness and high ductility. However, the effect of fire on the structural stability of EBFs has not been well documented. Object-oriented techniques used in software program development have become popular in recent years, primarily because of their ability in addressing various complexity issues. Software developed based on an object-oriented approach is more robust than conventional software. Using the abovementioned approach, additional codes can be incorporated, thereby simplifying testing, refining, maintenance, and software extension. Furthermore, the object-oriented approach can be used for finite element analysis. This paper presents the further development of OpenSees software with the inclusion of other parameters: thermal parallel material, thermal spring element, thermal spring section, as well as beam with hinges and thermal elements subjected to fire loading. In contrast to the routine creation of fire-specific applications, these modifications improve the existing finite-element codes, thereby facilitating multi-hazard analysis (e.g., post-earthquake fire). OpenSees is considered in this study as it is an open-source application and suitable for object-oriented design. The abovementioned elements, particularly spring elements, are used extensively in structural simulations (e.g., the modeling of a link beam in an EBF); however, owing to the lack of thermal functions for these elements in OpenSees, the thermal performance of structures that involve these elements cannot be evaluated. Herein, the aforementioned new elements are introduced for the first time; furthermore, the behavior of an EBF system is investigated under thermal loads using open-source software. The thermal performance of EBFs subjected to realistic fire is evaluated in this study based on an analytical modeling of a three-story building. Finally, several compartment fire scenarios are simulated for both EBFs and gravity framing bays. Results show that the EBFs improve the fire performance of the system by extending the time to collapse.

Thermal Protection Performances of the Macro and/or Nano Enhanced PCM in a Representative Battery Pack

ABSTRACT This experimental study focused on the comparison of thermal protection performances of macro and/or nano enhanced organic PCM in a representative battery pack from low to high discharge rates. The macro/nano enhanced RT-44 provides the desired battery thermal protection requirements in terms of criteria such as maximum temperature and maximum temperature difference restriction and uniform temperature distribution throughout the battery pack. It increases the effective battery thermal protection time by 117%-32% depending on the discharge rates. While PCM thermal protection provides a more homogeneous temperature distribution throughout the battery pack, nano and/or macro enhanced one provides it throughout the cell. The macro enhancement essentially makes a major contribution to shortening the cooling time for the next use.

Experimental Comparison of Thermal Performance of Different Refrigerants and Modeling with Regression Algorithms

Experimental Comparison of Thermal Performance of Different Refrigerants and Modeling with Regression Algorithms

Comparison of thermal performance of plate and corrugated fin heatsinks with a modified base under free convection

In this paper, a numerical study was conducted to measure the convective exchange in heat sinks with curved fins mounted on a normal base (case B) and modified one (case C). Both cases are subjected to natural convection. The study was conducted for a Rayleigh number range of 1.7 × 108 to 7 × 108 and an input heat of 25 W to 144 W. The conservation of mass, momentum, turbulence and energy equations were solved using Ansys - Fluent software.The validation of the numerical model was performed by comparing the results of numerical simulation, with those calculated using empirical correlations for conventional fins (case A as reference). For each configuration, the temperature and velocity contours are given and discussed. The thermal performance of heat sinks for different fins is characterized by the heat dissipation rate per unit mass. The results showed that, the heat transfer improvement is better with the undulated fins mounted on a non-corrugated base than with the other configurations. The geometry with a corrugated fin mounted on a normal base is the most efficient. Compared to the conventional geometry, the temperature is reduced by (-18.35 °C) and the mass is minimized by 44%. Knowing that the heatsink with the corrugated fin and modified base (case C) offers a maximum mass reduction of 49%, and a slight cooling (-7.79 °C) compared to case B. But in any event, both geometries offer an advantage in terms of cooling and mass. The latter one will be useful for applications where mass is a primary consideration.

Resilience of seagrass populations to thermal stress does not reflect regional differences in ocean climate.

Summary The prevalence of local adaptation and phenotypic plasticity among populations is critical to accurately predicting when and where climate change impacts will occur. Currently, comparisons of thermal performance between populations are untested for most marine species or overlooked by models predicting the thermal sensitivity of species to extirpation.Here we compared the ecological response and recovery of seagrass populations (Posidonia oceanica) to thermal stress throughout a year‐long translocation experiment across a 2800‐km gradient in ocean climate. Transplants in central and warm‐edge locations experienced temperatures > 29°C, representing thermal anomalies > 5°C above long‐term maxima for cool‐edge populations, 1.5°C for central and < 1°C for warm‐edge populations.Cool‐edge, central and warm‐edge populations differed in thermal performance when grown under common conditions, but patterns contrasted with expectations based on thermal geography. Cool‐edge populations did not differ from warm‐edge populations under common conditions and performed significantly better than central populations in growth and survival.Our findings reveal that thermal performance does not necessarily reflect the thermal geography of a species. We demonstrate that warm‐edge populations can be less sensitive to thermal stress than cooler, central populations suggesting that Mediterranean seagrasses have greater resilience to warming than current paradigms suggest.

Low Thermal Budget Fabrication and Performance Comparison of MFM Capacitors With Thermal and Plasma-Enhanced Atomic Layer Deposited Hf0.45Zr0.55O x Ferroelectrics

The ferroelectricity of Zr-doped HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (HZO) thin films induced by low thermal budget annealing provides great potential to implement the ferroelectric functionalities into the back end of line (BEOL) process of the standard CMOS integrated circuits. However, most of previous works need high temperature annealing or long time annealing to acquire ferroelectricity. In this work, both annealing temperature and time are optimized to achieve optimal ferroelectricity of Hf <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.45</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.55</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> films produced by thermal atomic layer deposition (TALD) and plasma-enhanced atomic layer deposition (PEALD). The results indicate that the TALD and PEALD films exhibit maximum double remanent polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{P}_{r}$ </tex-math></inline-formula> ) of ~36.8 and ~ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30.0 {{ \boldsymbol {\mu }}}\text{C}/$ </tex-math></inline-formula> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively, after annealing at 330 °C for 300 s. Furthermore, the characteristics of the above annealed films are comprehensively compared. It is found that the PEALD film exhibits a higher maximum-dielectric-constant, a higher breakdown electric field, and better endurance against switching cycles than the TALD one, but more severe wake-up effects. This is ascribed to the factor that the PEALD film contains more tetragonal phase and less defects than the TALD one. In this article, the PEALD film has moderate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{r}$ </tex-math></inline-formula> and robust endurance, which is more promising for memory devices.

Comparison of thermal performances between copper and stainless steels on application of graphene coatings

Computational Fluid Dynamics (CFD) and heat transfer simulations are conducted for a cross flow heat exchanger. The heat exchanger consists of a linear pipe carrying a heated fluid. The thermal interactions between the heated fluid having a laminar flow and the walls of the pipe have been studied under the influence of an external environment of water having a turbulent flow, in a direction normal to the pipe. A RANS model with a k-ε variant was used to model the behavior of different material pipes which were observed under the varying conditions of turbulence, velocity, pressure and vorticity. When subjected to the same conditions, plots of the temperature gradient, isothermal contours, heat transfer coefficient against Reynolds number and thermal conductivity modelled against the various graphene coating thicknesses studied have shown that out of Copper and Stainless Steel the former has shown the most significant increase in thermal conductivity on the addition of a Graphene coating. Furthermore, to check for optimum efficiency, the same study was conducted with an internal coating of a Graphene layer for the aforementioned materials. It has been observed that an outer coating was not only more economically feasible, but also showed better thermal performance compared to an inner coating of graphene for copper, however it did improve the thermal performance of Stainless Steel significantly.

Thermal Performance Comparison of Parabolic Trough Collector (PTC) Using Various Nanofluids

The objective of this paper is to investigate the theoretical performance of Parabolic Trough Collector (PTC) using various nanofluids. The theoretical performances are calculated for Al2O3, graphite, magnetite, SWCNH, CuO, SiO2, MWCNT, TiO2, Fe2O3, and ZnO in water nanofluids. The heat transfer equations, thermodynamic properties of nanofluid and pumping power are utilised for the development of novel thermal model. The theoretical thermal efficiency of the PTC is calculated, and the economic viability of the technology is predicted for a range of nanofluid concentration. The results showed that the thermal conductivity increases with the concentration of nanoparticles in the base fluid. Magnetite nanofluid showed the highest thermal efficiency, followed by CuO, MWCNT, ZnO, SWCNH, TiO2, Fe2O3, Al2O3, graphite, and SiO2, respectively. The study reveals that MWCNT at 0.4% concentration is the best-suited nanofluid considering thermal gain and pumping power. Most of the nanofluids achieved optimum efficiency at 0.4% concentration. The influence of mass flow rate on thermal efficiency is evaluated. When the mass flow rate increased from 70 Kg/hr to 90Kg/hr, a 10%-20% efficiency increase is observed. Dispersing nanofluids reduces the levelized cost of energy of large-scale power plants. These findings add to the knowledge of the scientific community aimed explicitly at solar thermal energy technology. The report can also be used as a base to pursue solar thermal projects on an economic basis.

Experimental thermal performance comparison of pure and metal foam-loaded PCMs

The thermal performance of latent heat thermal energy storage (LHTES) systems considerably depends on thermal conductivity of adopted phase change materials (PCMs). To increase the low thermal conductivity of these materials, pure PCMs can be loaded with metal foams. In this study, the melting process of pure and metal-foam loaded phase change materials placed in a rectangular shape case is experimentally investigated by imposing a constant heat flux at the top. Two different paraffin waxes with melting point of about 35°C are tested. The results obtained with pure PCM are compared with those achieved from the use of PCM combined with two different porous metals: a 10 PPI aluminum foam with 96% porosity and a 20 PPI copper foam with 95% porosity. The results demonstrate how metal foams lead to a significant improvement of conduction heat transfer reducing significantly the melting time and the temperature difference between the heater and PCM.

Comparison of thermal performance between a surface and a volumetric absorption solar collector using water and Fe3O4 nanofluid

In this study, the thermal performance of a surface absorption solar collector (SASC) and a volumetric absorption solar collector (VASC) using water and Fe3O4 nanofluid was experimentally investigated. As a result, the heat removal factor (FR) and overall heat loss coefficient (UL) of the SASC were increased with the concentration and mass flow rate of the Fe3O4 nanofluid. The limit-normalized temperature difference (LNTD) of the SASC was reduced compared with that of water because of increased heat loss due to the improved heat transfer performance of the Fe3O4 nanofluid. In addition, the thermal and exergy efficiencies of the SASC using the Fe3O4 nanofluid were lower than those using water. However, in the case of the VASC, FR increased while UL decreased with the increasing mass flow rate of the Fe3O4 nanofluid. When the mass flow rate and concentration of the Fe3O4 nanofluid increase, its LNTD increased beyond water. The thermal and exergy efficiencies of the VASC using the Fe3O4 nanofluid were higher than those using water. Moreover, the maximum thermal and exergy efficiencies was the maximum when the 0.05 wt% Fe3O4 nanofluid was used in the VASC.

Thermal and Reliability Performance Comparison of DBC-Based and Organic-Based Double-Sided Cooled Power Modules

Abstract Direct Bonded Copper (DBC) is the most popular solution for conventional high-power modules because of superior thermal/electrical/mechanical performance and mature manufacturing. To meet the rising demand of power density and power rating, a Double-Sided Cooled (DSC) sandwich structure using dual insulated metal-clad substrates was proposed and DBC still dominated the substrate selection of DSC power modules. However, there are several long-existing reliability challenges of conventional DBC-based power modules and the cost of DBC is relatively high compared with organic and metal (e.g. lead frame) substrates. This study proposes a DSC 1.2 kV half-bridge power module using dual epoxy-resin Insulated Metal Substrate (eIMS) for solving DBC-based power module issues and providing a cost-effective solution. The thermal performance outperforms traditional Alumina (Al2O3) DBC-based DSC power module due to moderate thermal conductivity (10 W/mK) and thin (120 μm) epoxy-resin composite dielectric layer compared with Alumina. The breakdown voltage of this high thermally conductive organic dielectric is 5 kVAC (@ 120 μm) and the Glass Transition Temperature (Tg) is 300°C which is indispensable for Wide-Band-Gap (WBG) devices and high-power applications. In terms of thermal-mechanical reliability, the organic-based DSC power module can pass the thermal cycling test over 2000 cycles by optimizing the mechanical properties of the encapsulant material. In conclusion, this paper not only proposes a competitive organic-based power module but also a methodology of evaluation for thermal and mechanical performance.