Assessment of thermo-hydraulic performance of inward dimpled tubes with variation in angular orientations

This paper presents a numerical investigation and assessment of thermal and hydraulic performance of dimpled tubes of varying topologies at constant heat flux of and Reynolds numbers ranging from 2300 to 15,000 The performance of the tubes consisting of conical, spherical and ellipsoidal dimples with equivalent flow volumes were compared using steady state Reynolds Averaged Navier Stokes simulations. The ellipsoidal dimples, in comparison to other dimple shapes, demonstrated large increment in heat transfer rate. The variation in the orientation of the ellipsoidal dimples was examined to further improve thermal and hydraulic performances of the tube. A 45° inclination angle of ellipsoidal dimple, from its major axis, increased the thermo-hydraulic performance by 58.1% and 20.2% in comparison to smooth tube and 0° ellipsoidal dimpled tube, respectively. Furthermore, Large Eddy Simulations (LES) were carried out to investigate the role geometrical assistance to fluid flow and heat transfer enhancement for the 45° and 90° ellipsoidal dimpled tubes. LES results revealed a flow channel of connected zones of wakes which maximized fluid-surface

Thermal Performance Enhancement of Lithium-Ion Batteries Using Phase Change Material and Fin Geometry Modification

The rapid increase in emissions and the depletion of fossil fuels have led to a rapid rise in the electric vehicle (EV) industry. Electric vehicles predominantly rely on lithium-ion batteries (LIBs) to power their electric motors. However, the charging and discharging processes of LIB packs generate heat, resulting in a significant decline in the battery performance of EVs. Consequently, there is a pressing need for effective battery thermal management systems (BTMSs) for lithium-ion batteries in EVs. In the current study, a novel experimental BTMS was developed for the thermal performance enhancement of an LIB pack comprising 2 × 2 cells. Three distinct fin configurations (circular, rectangular, and tapered) were integrated for the outer wall of the lithium-ion cells. Additionally, the cells were fully submerged in phase change material (PCM). The study considered 1C, 2C, and 3C cell discharge rates, affiliated with their corresponding volumetric heat generation rates. The combination of rectangular fins and PCM manifested superior performance, reducing the mean cell temperature by 29.71% and 28.36% compared to unfinned lithium-ion cells under ambient conditions at the 1C and 2C discharge rates. Furthermore, at the 3C discharge rate, lithium-ion cells equipped with rectangular fins demonstrated a delay of 40 min in reaching the maximum surface temperature of 40 °C compared to the unfinned ambient case. After 60 min of battery discharge at the 3C rate, the cell surface temperature of the rectangular fin case only reached 42.7 °C. Furthermore, numerical simulations showed that the Nusselt numbers for lithium-ion cells with rectangular fins improved by 9.72% compared to unfinned configurations at the 3C discharge rate

Computational methodology for non-evaporating spray in quiescent chamber using Large Eddy Simulation

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Hydrodynamic description of a vibrofluidized granular bed driven at high frequency

Results are reported for a dry granular bed vertically excited at high and low frequencies with constant peak base velocity. Previous experimental data sets using Nuclear Magnetic Resonance are used for comparison at low (~38 Hz) and high (~11 kHz) vibration frequencies. Packing fractions and granular temperatures are compared against hydrodynamic and molecular dynamics simulation models. At low frequency hydrodynamic and MD simulations results show the presence of a heat wave. Whilst at high frequencies soft sphere potential based MD simulations highlight the role of finite duration collisions between particles and the vibrating wall. In this region the timescales of vibration and collision duration are not well separated, as observed in experimental results

Exergetic optimization and comparison of combined gas turbine supercritical CO2 power cycles

For developing a sustainable power system, the key is to maximize the use of available resources with a minimal impact on the environment. One technique for achieving this is exhaust heat recovery. In this paper, three gas turbine exhaust heat recovery supercritical carbon dioxide combined power cycles are presented. They are combined gas turbine-recompression cycle, combined gas turbine-preheating cycle, and combined gas turbine-simple regenerative cycle. For all the cycles, thermodynamic models are developed and the influence of varying mass flow rates, compression ratio, and mass split/recompression percentages in different components of all three cycles are investigated. Using genetic algorithm, exergetic optimization is done to find the optimal configuration for each cycle. The reduction in CO2 emissions in presented cycles against fossil fuel power cycles is also assessed. Additionally, a comparison with a simple gas turbine (SGT) and an air bottoming combined cycle (ABC) is presented. The results indicate that owing to exhaust exergy recovery, there is a significant improvement in the energetic and exergetic performance of combined gas turbine-supercritical CO2 power cycles compared to that of SGT and ABC. The sum of exergy destruction and exergy loss in the combined cycles is lower as compared to the sum in SGT. The reduction in losses compared to SGT is 22.89% in the case of the combined gas turbine recompression cycle and 35.8% in the case of the combined gas turbine preheating cycle (CGTPHC). Moreover, the energetic and exergetic performances of the bottoming supercritical CO2 recompression cycles (BRECs) are better than those of the bottoming supercritical CO2 preheating cycle owing to lower exergy destruction in the components of BREC. As a result of comparative analysis based on the exergetic performance and environmental impact, the CGTPHC is selected as an appropriate option for gas turbine exhaust exergy recovery

Performance Investigation of Air Velocity Effects on PV Modules under Controlled Conditions

Junction temperature of PV modules is one of the key parameters on which the performance of PV modules depends. In the present work, an experimental investigation was carried out to analyze the effects of air velocity on the performance of two PV modules, that is, monocrystalline silicon and polycrystalline silicon under the controlled conditions of a wind tunnel in the presence of an artificial solar simulator. The parameters investigated include the surface temperature variation, power output, and efficiency of PV modules under varying air velocity from near zero (indoor lab. conditions) to 15 m/s. Additionally, the results were also determined at two different module angular positions: at 0° angle, that is, parallel to air direction and at 10° angle with the direction of coming air to consider the effects of tilt angles. Afterwards, the thermal analysis of the modules was performed using Ansys-Fluent in which junction temperature and heat flux of modules were determined by applying appropriate boundary conditions, such as air velocity, heat flux, and solar radiation. Finally, the numerical results are compared with the experiment in terms of junction temperatures of modules and good agreement was found. Additionally, the results showed that the maximum module temperature drops by 17.2°C and the module efficiency and power output increased from 10 to 12% with increasing air velocity