Improvement In Thermal Performance Research Articles

An Evaluation on Thermal Performance Improvements for SiC Power Module Integrated With Vapor Chamber in MMC

In this article, the improvements in thermal performances of the SiC power module integrated with vapor chamber (VC) under modular multilevel converters (MMCs) working conditions are evaluated for the first time. The copper baseplate of the SiC power module is replaced by a VC with the same size, which has the advantages of good temperature uniformity, excellent thermal conductivity, compactness, flexible design, high integration, and low cost. The FEM simulation results show that the hotspot temperature, maximum temperature difference among the chips, and low-frequency temperature swing (TS <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{L}$ </tex-math></inline-formula> ) can be significantly reduced. Then, the well-designed VC is customized and integrated with the SiC power module. Finally, the advantages of VC in improving the thermal performances of power modules in SiC-MMC are validated by the comparative experiment. The experimental results show that the local over-temperature and thermal unbalance of the power module in SiC-MMC can be significantly mitigated.

Thermal Performance Improvement of Modified Hemispherical Cavity Receiver with Air Curtain

Heat losses from solar cavity receivers degrade the efficiency of solar parabolic dish collector system. Specifically, increased convection losses emulate a significant contribution in decreasing the performance of the modified solar cavity receiver and hence, reducing these convection losses has become a matter of great concern. The Air curtain plays a crucial role in minimizing the convection losses. This work proposes an air curtain-based modified cavity receiver wherein a plane nozzle is placed on the face of receiver to produce air curtain effect. Air curtain will prevent hot air from escaping the modified cavity receiver and increase the stagnation zone inside it to reduce natural convection on the surfaces. Numerical analyses are performed considering different air velocities and receiver orientations to evaluate the effect of air curtains on the convection losses. The impact of plane air nozzle parameters like outlet temperature, inclination, and outlet velocity of the nozzle on convection losses are shown and these parameters’ optimal value is evaluated. Our results state that the air curtain attached to the modified solar cavity receiver significantly improves performance by reducing the convection losses.

Recent Developments and Advancements in Solar Air Heaters: A Detailed Review

The scientific literature extensively mentions the use of a solar air heater (SAH) by utilizing solar energy for heating purposes. The poor heat-transfer rate of an SAH with a flat plate is caused by developing a laminar sub-layer near the heated base plate. The plate temperatures improve significantly, resulting in losses and a decrease in performance. The passive approach entails the placement of fins/turbulators/pouring material/ribs to the surface where the boundary layer forms to disrupt it. Artificially roughened SAH for gathering and efficiently using solar radiations for thermal purposes is extensively described in the literature. This paper includes a thorough literature overview of the history, basics, roughness evolution, forms of SAH, and recent breakthroughs in thermal performance improvement techniques for SAH compiled by several researchers. This paper uses a comparative evaluation of several roughness geometries and kinds of SAH to uncover thermohydraulic performance factors that may be considered in future research to pick the optimal configuration.

Thermo-Hydraulic Optimization of Shell and Externally Finned Tubes Heat Exchanger by the Thermal Efficiency Method and Second Law of Thermodynamics

The application aims to determine the thermal and hydraulic performance of externally finned, counter-flow, Shell, and Tube Heat Exchangers (STHE). The application refers to the cooling of machine oil flowing in the annular region, including non-spherical cylindrical nanoparticles of Boehmite Alumina. The oil inlet temperature is equal to 80 °C. Sea water is a coolant with an inlet temperature of 20°C. The main parameter in the optimization process is the number of finned tubes used for oil cooling. Another optimization factor is the number of heat exchanger units connected by hairpin. The number of fins per tube is fixed, equal to 34. The oil flow is set and equal to 4.0 kg/s. The inlet water flow varies, with a maximum flow of 5.0 kg/s. The quantities determined for analysis are: the thermal effectiveness, the actual and maximum heat transfer rates, the pressure drops caused in the tubes and by the flow in the annular region and fin system, the thermal and viscous irreversibilities, and the fluid outlet temperatures, and the thermodynamic Bejan number. It was determined that increasing the number of finned tubes from two to six tubes leads to better thermal and hydrodynamic performance. That is, it produces a favorable cost-benefit, to the detriment of the high viscous dissipation caused by the oil in the annular region. As an object of analysis, the inclusion of nanoparticles showed a significant improvement in thermal performance and an increase in viscous dissipation, with a slight decline in the Bejan number.

Thermal performance improvement on winglet tip of a turbine stage under engine condition-part I: Winglet geometry modifications

Heat transfer and film cooling effect on the winglet-squealer tip in the first stage of a gas turbine were numerically investigated under engine condition. To reveal the effect of P.S. (pressure side) winglet geometry on the tip thermal performance, seven different tip configurations (i.e. conventional squealer tip, no P.S. rim tip, three kinds of uniform cross-section winglet tip, and two kinds of distorted winglet tip) were selected to determine a proper design. The heat transfer and film cooling effect on the distorted winglet tip, conventional squealer tip and no P.S. rim tip were compared at two different cooling arrangements (i.e. only tip cooling and both tip and P.S. cooling). The results show that a proper design of distorted winglet geometry can effectively eliminate the high heat transfer areas and enhance the uniformity of thermal load on the cavity floor. Compared with the convention squealer tip, the thermal load on the distorted winglet tip is reduced by 16.45%. With vertical ejections from both tip and P.S. holes, the film cooling effectiveness on the distorted winglet tip is improved by 9.13% and 9.6% as compared with the convention squealer tip and no P.S. rim tip, respectively.

Experimental investigation of thermal efficiency and thermal performance improvement of compound parabolic collector utilizing SiO2/Ethylene glycol-water nanofluid.

A compound parabolic collector has been used in the present study to lower operating costs per unit of heat increase compared to other tracker concentrators. This type of collector has been given more attention in industrial and domestic applications in the temperature range of 60 to 300°C. Also, to increase the thermal efficiency, nanofluid containing SiO2 nanoparticles in ethylene glycol-water hybrid base fluid (10-90 vol.%) have been used in three different volumetric fractions. The innovation of this present study includes the utilization of mentioned nanofluids for the first time in this collector, which has good stability and is cost-effective compared to other nanoparticles. In addition, the experimental measurement of thermal and hydraulic properties of nanofluids represents new aspects of the present study. The experiments used three volumetric fractions of 0.5%, 1%, and 1.5% under extensive solar radiation. Thermal performance of the collector at four volumetric flow rates of 1, 1.5, 2, and 2.5 Lit/min have been investigated according to ASHRAE standard 93-2010 (RA2014). According to the experimental data, the thermal efficiency of the collector improved by 5% to 11.6% when the nanofluid was applied. The maximum enhancement of the average Nusselt number of the nanofluid versus the base fluid at the volumetric flow rate of 1 Lit/min and the volumetric fraction of 1.5% was equal to 7.3%. Besides, nanofluid increased the pressure drop, and consequently, the pumping power slightly. Finally, considering both the impacts of heat transfer and pressure drop, performance evaluation criteria and overall efficiency for nanofluid have been analyzed. The results represented that in all volumetric fractions, the values of performance evaluation criteria and overall efficiency enhanced compared to the base fluid. This research provides researchers and engineers with important information to better understand the thermal and hydraulic parameters of the parabolic compound concentrator in the presence of nanofluid to improve its thermal performance. The results also highlight the potential of using SiO2 nanoparticles to improve the thermal efficiency of solar collectors despite their low thermal conductivity compared to other conventional nanoparticles.

MXene incorporated nanofluids for energy conversion performance augmentation of a concentrated photovoltaic/thermal solar collector

This research work introduces emerging two-dimensional (2D) MXene (Ti3C2) and Therminol55 oil-based mono and hybrid nanofluids for concentrated photovoltaic/thermal (CPV/T) solar systems. This study focuses on the experimental formulation, characterization of properties, and performance evaluation of the nanofluid-based CPV/T system. Thermo-physical (conductivity, viscosity, and rheology), optical (UV-vis and FT-IR), and stability (Zeta potential and TGA) properties of the formulated nanofluids are characterized at 0.025 wt.% to 0.125 wt.% concentrations of dispersed particles using experimental analysis. By suspending the nanomaterials, photo-thermal energy conversion is improved considerably, up to 85.98%. The thermal conductivity of pure oil is increased by adding Ti3C2 and CuO nanomaterials. The highest enhancements of up to 84.55% and 80.03% are observed for the TH-55/Ti3C2 and TH-55/Ti3C2 + CuO nanofluids, respectively. Furthermore, dynamic viscosity decreased dramatically over the temperature range investigated (25°C-105°C), and the nanofluid exhibited dominant Newtonian flow behavior as viscosity remained nearly constant up to a shear rate of 100 s−1. Numerical simulations of the experimentally evaluated nanofluids are performed to evaluate the effect on a CPV/T collector using a three-dimensional transient model. The numerical analysis revealed significant improvements in thermal and electrical energy conversion performance, as well as cooling effects. At a concentrated solar irradiance of 5000 W/m2 and an optimal flow rate of 3 L/min, the highest thermal and electrical energy conversion efficiency enhancements are found to be 12.8% and 2%, respectively.

Liquid-based battery thermal management system performance improvement with intersected serpentine channels

A thermal management system that could maintain the temperature within the proper range is essential for lithium-ion batteries. Apart from the thermal performance, the pumping power needs to be reduced to increase the system efficiency. In this study, intersecting channels were integrated into the conventional serpentine channel to improve the performance of liquid-based thermal management system for prismatic lithium-ion batteries. Numerical results showed that adding intersecting channels could significantly decrease the required pumping power, thereby enhancing the thermal performance at given power cost. Compared to straight design, V-shape intersecting channel design performs better in terms of the thermal performance. Besides, the effects of influencing factors including the intersecting number, intersecting width and on the thermal characteristics of V-shape intersecting serpentine channel were investigated. Results demonstrated that all the structural parameters had an optimum value within the studied range. The best thermal performance subject to the power cost was achieved with the intersecting number of 7, width of 2.0 mm and angle of 45°. The gradient intersecting spacings was developed to further alleviate the temperature imbalance within the battery. It is seen that the thermal performance was improved with the channel spacing gradient, especially when the spacing gradient was 2 mm.

Activation Energy Performance through Magnetized Hybrid Fe3O4–PP Nanofluids Flow with Impact of the Cluster Interfacial Nanolayer

The current work investigated the mass and heat transfer of the MHD hybrid nanofluid flow subject to the impact of activation energy and cluster interfacial nanolayer. The heat transport processes related to the interfacial nanolayer between nanoparticles and base fluids enhanced the base fluid’s thermal conductivity. The tiny particles of Fe3O4 and PPy were considered due to the extraordinary thermal conductivity which is of remarkable significance in nanotechnology, electronic devices, and modern shaped heat exchangers. Using the similarity approach, the governing higher-order nonlinear coupled partial differential equation was reduced to a system of ordinary differential equations (ODEs). Fe3O4–PPy hybrid nanoparticles have a considerable influence on thermal performance, and when compared to non-interfacial nanolayer thermal conductivity, the interfacial nanolayer thermal conductivity model produced substantial findings. The increase in nanolayer thickness from level 1 to level 5 had a significant influence on thermal performance improvement. Further, the heat and mass transfer rate was enhanced with higher input values of interfacial nanolayer thickness.

An Expert Model Based on Physics-Aware Neural Network for the Prediction of Thermal Conductivity of Nanofluids

Abstract Operating fluids are always a significant factor for not achieving a good enough performance of heat transfer equipment and also for growing the energy costs. To resolve this issue, nanofluids are considered a potential choice for conventional heat transfer fluids due to their efficiency for the improvement of overall thermal performance. The aim of this research is to propose a physics-guided machine learning approach by incorporating physics-based relations at the initial stage and into traditional loss functions for predicting the thermal conductivity of water-based nanofluids using a wide range of both experimental and simulated data of nanoparticles Al2O3, CuO, and TiO2. Further, smart connectionist methods, viz., ridge regression, lasso regression, random forest, extreme gradient boosting (xgboost (XGB)), and black-box multilayer perceptron (MLP) are applied to compare the present physics-aware MLP model based on different statistical indicators. The accuracy analyses reveal that the use of physical views to monitor the learning of neural networks shows better results with mean absolute percentage error (MAPE) = 0.7075%, root-mean-squared error (RMSE) = 0.0042 W/mK, and R2 = 0.9525. The temperature and volume concentration variations are discussed graphically. Furthermore, the outcomes of applied algorithms confirm that the well-known theoretical and computer-aided models show substandard results than the proposed model.

SiC@BaTiO3 core-shell fillers improved high temperature energy storage density of P(VDF-HFP) based nanocomposites

The emerging industry has put forward stricter requirements for the operating temperature of electrostatic capacitors. Improving the high temperature breakdown strength is the key issue to enhance the thermal stability of polymer-based nanocomposites. In this study, the nanoparticles which is composed of high heat conductivity coefficient core (SiC) and high dielectric constant shell (BaTiO3) were prepared and used as fillers, with the purpose of improving breakdown strength (Eb) and discharged energy storage density (Udis) of P(VDF-HFP)-based nanocomposites at high temperature. Compared with the pure polymer, the composite films, especially the films with 7.5 wt% fillers, showed great enhancements in breakdown strength and discharged energy storage density at high temperature. The average Eb reached 1524.6 kV/cm at 120 °C, which was 1.84 times of the contrast. The Udis at 120 °C was 2.05 J/cm3 (1700 kV/cm), which increased by 569.4% than that of pure polymer (at 700 kV/cm, 0.36 J/cm3). The improvement of thermal performance and Young's modulus of materials was contributing to the enhancements of thermal breakdown strength and electromechanical breakdown strength at high temperature. This study provides an effective way to prepare dielectric composites for high-temperature environment application.

Thermal performance improvement on winglet tip of a turbine stage under engine condition-part II: Ejection angle adjustment

Part I has indicated that the vertical ejection causes pronounced coolant lifting-off effect on the winglet tip of turbine stage. To solve this problem, Part II presents the study on adjusting ejection angle to reduce thermal load on the winglet tip under engine condition. Three procedures were taken to realize the mitigation of thermal load on the winglet tip of turbine stage. Firstly, the streamwise ejection angle was varied to determine a suitable ejection angle for the majority of cooling holes. Secondly, different numbers of tip cooling holes were selected to adjust the ejection angles towards P.S. (pressure side), aiming at enhancing the film cooling effect at the front part of the cavity floor. Lastly, different P.S. deflection angles were tested to find the suitable streamwise ejection angles for the selected holes. The results show that the inclined coolant ejections are quite effective to reduce the thermal load on the winglet tip. As the P.S. defection angles for the tip cooling holes at the front part of the cavity floor equal to 60°, and the streamwise ejection angles for the other cooling holes are set to 120°, the lowest thermal load is achieved on the winglet tip of turbine stage. After adjustment, the area-averaged heat transfer coefficient on the tip surface is decreased by 38.84%, and the area-averaged film cooling effectiveness is increased by 42.24%, as compared with the vertical ejection case. Moreover, the uniformity of the coolant coverage on the winglet tip has been improved, significantly.

Experimental and Numerical Performance Evaluation of Bio-Based and Recycled Thermal Break Strips in LSF Partition Walls

The thermal performance of Lightweight Steel Framed (LSF) walls could be strongly compromised due to steel’s high thermal conductivity and their related thermal bridges. In this paper, the performance of bio-based (pine wood) and recycled (rubber–cork composite) Thermal Break Strip (TBS) materials, to mitigate the thermal bridge effect originated by steel profiles in LSF partition walls, is evaluated. This assessment was achieved by measurements under controlled laboratory conditions and by predictions using some numerical simulation models. Regarding the measurements, two climatic chambers (cold and hot) were used to impose a nearly constant temperature difference (around 35 °C), between the LSF partition test samples’ surfaces. To measure the overall surface-to-surface thermal resistance (R-value) of the evaluated LSF wall configurations, the Heat Flow Meter (HFM) method was used. Moreover, the measured values were compared with the calculations by 2D (THERM models) and 3D (ANSYS models) numerical simulations, exhibiting an excellent agreement (less than ±2% difference). Three TBS locations and three materials are evaluated, with their thermal performance improvement compared with a reference interior partition LSF wall, having no TBS. The top performance was accomplished by the aerogel super-insulating TBS material. The bio-based material (pine wood) and the recycled rubber–cork composite present quite similar results, with a slight advantage for the pine wood TBSs, given their higher thickness. Considering the TBS location, the inner and outer side present comparable performances. When using TBSs on both sides of steel profile flanges, there is a relevant thermal performance improvement, as expected. The thickness of the TBS also presents a noteworthy influence on the LSF partition thermal resistance.

Investigation and optimization of electro-thermal performance of Double Gate-All-Around MOSFET

The Double Gate-All-Around (DGAA) MOSFET and GAA NWFET are compared and analyzed from both electrical and thermal perspectives under four different conditions by adjusting the channel radius of the NWFET (RGAA). DGAA MOSFET is found to easier form volume inversion than GAA NWFET, and has the advantage of better gate controllability and drivability and the primary concern of worse heat dissipation efficiency. Hetero-Gate-Dielectric (HGD) structure, channel design and spacer engineering are adopted to weaken the serious SHEs in DGAA MOSFET while maintaining a good SCEs immunity. Results show that the DGAA MOSFET with the single-k Al2O3 spacer can generate a better trade-off between electrical and thermal performance than other spacer combinations. In addition, the improvement in thermal performance of DGAA MOSFET by the HGD structure is relatively limited. Compared with GAA NWFET without stacking, the optimized DGAA MOSFET with single-k Al2O3 spacer, appropriate channel thickness (Tch = 5 nm) to form volume inversion and underlap channel (Lun = 4 nm) has better electrical characteristics whose drivability improves at least twice with similar Rth.

Performance enhancement of photovoltaic module using finned phase change material panel: An experimental study under Iraq hot climate conditions

ABSTRACT The operational temperature highly influences the efficiency of the solar photovoltaic (PV) module, in which high temperature decreases the output power accordingly. In this work, a polycrystalline PV module is modified using a finned phase change material (PCM) panel attached to the rear as a thermal energy storage unit to decrease and regulate the operating temperature under hot weather conditions in southern Iraq. For this purpose, local Iraqi paraffin wax is used as a PCM loaded into a galvanized steel panel that has internal smooth wavy fins to improve the PCM poor thermal conductivity and accelerate its melting and solidification rates. Experimental results showed that the modified PV module temperature is decreased by up to 16°C compared with the reference PV module, resulting in maximum output power of up to 38.4% more than an identical reference PV module. Moreover, the electrical efficiency of the modified PV module is improved respectively by 34% and 37.2% on the first and second day of the experiment over the reference PV module, indicating remarkable electrical and thermal performance improvement.

Study on thermal performance improvement technology of latent heat thermal energy storage for building heating

Thermal energy storage technology incorporating phase change materials (PCM) is a feasible option to take advantage of off-peak electricity tariff for achieving the function of “peak load shaving” and energy efficiency economically in electric heating systems. However, the low thermal conductivity of phase change materials in these systems limits its application. In this work, a design of non-uniformly distributed fin configuration was proposed, considering the optimization of the non-uniform arrangement and coil structure to enhance heat transfer. A two-dimensional CFD model has been developed and validated with test data. The coil inner diameter, tube pitch, row spacing and fin height were optimized based on the simulated temperature variations and visualizations of the PCM during charging and discharging processes. Results demonstrated that the mass of fully melted PCM is increased by 24.5%, and the outlet water temperature is about 3℃ higher for the optimal non-uniform finned coil structure. Additionally, the influence of the device overall dimensions on the PCM utilization rate is also demonstrated in this study. After optimization, the heat energy discharged-charged ratio can be increased by 39.6% to achieve a better thermal energy discharging efficiency. The results may provide valuable references for appropriate latent thermal energy storage design solutions in practice.

Turbulence and thermo‐flow behavior of air in a rectangular channel with partially inclined baffles

AbstractIn this paper, the thermal performance improvements of a heat removal system like an electronic system have been analyzed. The studied case is a horizontal channel in which two partially inclined baffles are attached with variable height and number. The channel is crossed by a forced convective flow of a cooling fluid (air). This numerical work evaluates the influences of the height and number of the baffles on the enhancement of the heat transfer rate. The mathematical model of this system is composed of nonlinear partial equations that the analytical solution for them is very complex, hence the need for numerical analysis is mandatory with the aid of a finite volume method. Accordingly, The numerical results are presented in axial and transverse velocity, temperature, local and average Nusselt number, local friction coefficient, pressure drop, heat transfer rate, and turbulence kinetic energy. The results revealed that it is possible to improve the thermal performance of the considered system by adopting designs that allow the maximum heat transfer rate with the minimum energy loss. In addition, results show that at the lowest Reynolds number (Re = 10,000), as the height of baffles rises from 0.01 to 0.03 m (growth by 200%), the heat transfer rate augments about 59.09%. Moreover, at the highest evaluated Reynolds number (Re = 87,300), by increasing the height of baffles up to 200%, the heat transfer rate increases by approximately 50.53%. Furthermore, employing a higher number of baffles leads to more heat transfer rates and a significant pressure drop.

Recent advances on the evacuated tube solar collector scrutinizing latest innovations in thermal performance improvement involving economic and environmental analysis

Solar energy plays the most pivotal role in providing energy demand among all renewable energy resources in today's world. Hence, significant advances are being made to harness solar energy by using ever-evolving technologies such as solar collectors. Evacuated tube collectors have been in the center of attention due to high thermal efficiency and desirable performance in unfavorable weather conditions. This paper provides new insight into how ETSC has changed drastically to improve thermal performance. A full-scale comparison has been drawn between thermosyphon vacuum tube and flat plate units at the commencement to demonstrate the competency and uniqueness of evacuated tube collectors. At the next step, numerous numerical and experimental investigations have been compiled and presented to cover the latest innovations and developments in thermal modifications of evacuated tube collectors concerning the use of PCM, working fluids, and design parameters. Furthermore, to evaluate the thermal efficiency of collectors, mathematical modeling is also presented based on single-tube and the whole collector. Evacuated tube collectors have various residential and industrial applications for water heating, solar drying, solar desalination, and air conditioning which have been discussed extensively. In addition, challenges and obstacles in utilizing evacuated tube collectors have been identified and need to be tackled to reach higher thermal performance. Last but not least, an economic-environmental analysis is presented, which consequently demonstrated that evacuated tube collectors are cost-effective and impose less danger to the environment than flat plate collectors.

Development and characterisation of sugarcane bagasse nanocellulose/ PLA composites

ABSTRACT Nanocellulose from sugarcane bagasse fibres was isolated via chemo-mechanical method subjected to preparation of its PLA-based bionanocomposites using an Injection moulding process with varying weight percentages of nanocellulose. The mechanical properties (i.e. tensile, flexural, fracture toughness, and impact), thermal property (TGA analysis) and dynamic mechanical properties (i.e. storage modulus, loss modulus, and damping) of the prepared bionanocomposites were studied. In addition, water absorption behaviour in terms of maximum water uptake and sorption, diffusion and permeability coefficients of the bionanocomposites were also investigated. Anoticeable improvement in thermal stability, water resistance, and mechanical performance was seen in bionanocomposites with 2 wt. % of nanocellulose. There were 41.44%, 26.21%, 89.79%, and 16.38% improvements in tensile strength, flexural strength, fracture toughness and impact strength, respectively, for 2 wt. % of nanocellulose reinforcement composite over neat PLA matrix. ANOVA analysis was also performed and found that contents of nanocellulose have asignificant impact on the mechanical properties of the bionanocomposites.

An experimental study on the binary hydrated salt composite zeolite for improving thermochemical energy storage performance

Thermochemical energy storage is a promising approach in thermal energy storage because of its advantages in high heat storage density, low heat loss and long period stability. The hydrated salt is a commonly used material in low temperature heat storage. A thermochemical energy storage experiment is conducted based on the material of MgCl2 and CaCl2 binary hydrated salt composite zeolite. In the preparation of binary hydrated salt, it's found that the optimum concentration is 15 wt% and the better mass ratio of MgCl2 to CaCl2 is 1:1.5. The metal mesh net packed method is adopted for further improvement of thermal performance. The results of energy release process show that the binary hydrated salt composite zeolite can increase the temperature rise up to 45.8 °C at the air velocity of 0.18 m/s. It can achieve the highest energy storage density of 719 kJ/kg and thermal efficiency of 41.9% at the air velocity of 0.32 m/s. Also, the combination with metal mesh packed nets can further improve the temperature rise peak, energy storage density and the thermal efficiency to 52.7 °C, 918 kJ/kg and 46.1%, respectively. This study provides references for multicomponent composite material preparation and thermochemical reactor improvement.