Showing papers on "Pressure drop published in 2021"

Heat transfer and pressure drop performance of Nanofluid: A state-of- the-art review

Abstract: Nanofluid is considered to be a new generation heat transfer medium which has attracted significant attention from the research community for the past two decades due to its reported high effectiveness in various heat transfer applications. Dispersed solid nanoparticles with enhanced thermal conductivity in base fluid possess substantial competence in augmenting thermal performance at the expense of moderate pumping power. This inclusive study elaborates the impact of nanofluids on thermo-hydraulic performance of thermal devices in order to ensure the appropriate selection and implementation of nanofluids in various engineering thermal devices. Inclusion of nanofluid as heat transfer fluid in various systems requiring high heat transfer rate e.g. solar thermal conversion systems, HVAC systems, electronic equipment, heat exchangers, nuclear reactors have imparted greater role in reducing negative impacts of climate change. The influence of size, concentration, type and shape of nanoparticles, working temperature, compound passive techniques and magnetic field effect on heat transfer and pressure drop performance of nanofluids are extensively discussed along with the drawbacks of nanofluids such as formation of fouling on heat transfer surfaces. This comprehensive review will be beneficial for engineers, researchers, and academics to commend the significance of various nanofluids and comprehend their remarkable impact on various heat transfer applications.

An improved mini-channel based liquid cooling strategy of prismatic LiFePO4 batteries for electric or hybrid vehicles

Abstract: Li-ion batteries are one of the most widely used energy storage devices owing to their relatively high energy density and power, yet they confront heating issues that lead to electrolyte fire and thermal runaway, especially in automotive applications. A well-designed thermal management system is necessary to mitigate the thermal issues occurring in high charge/discharge conditions. Keeping this in view, an ingeniously designed rectangular mini-channel cold plate is proposed to sandwich in between two consecutive 7Ah prismatic lithium iron phosphate (LiFePO4) batteries with a provision of coolant flow through the mini-channels across the cold plate to form a battery module. A numerical model for the varying channel number, channel width, coolant flow rate, coolant and ambient temperature, etc. to uphold the battery module temperature within the range of 25 °C-40 °C is developed in COMSOL Multiphysics 5.4. A detailed thermodynamic analysis suggests that a cold plate comprising 5 mini channels of width 4 mm with parallel flow design, and water entry near to the charging port with a flow rate of 0.003 kg.s − 1 and temperature of 25 °C as the ideal trade-off between heat transfer and pressure drop for better thermal management across the battery module. A uniform heat propagation in longitudinal direction justifies the optimum design of the cold plate.

Combination Effect of Baffle Arrangement and Hybrid Nanofluid on Thermal Performance of a Shell and Tube Heat Exchanger Using 3-D Homogeneous Mixture Model

Abstract: In this study, thermal performance and flow characteristics of a shell and tube heat exchanger equipped with various baffle angles were studied. The heat exchanger was operated with distilled water, and a hybrid nanofluid at three concentrations of 0.04% and 0.10% of GNP-Ag/water within Reynolds numbers ranged between 10,000 and 20,000. The thermophysical properties of nanofluid varied with temperature and nanoparticles’ concentration. The baffle angles were set at 45°, 90°, 135°, and 180°. Results showed that the calculated Nusselt number (Nu) could be improved by adding nanoparticles to the distilled water or increasing the fluid’s Reynolds number. At a low Re number, the Nu corresponding to baffle angle of 135° was very close to that recorded for the angle of 180°. At Re = 20,000, the Nu number was the highest (by 35% compared to the reference case), belonging to a baffle angle of 135°. Additionally, results related to friction factor and pressure drop showed that more locations with fluid blocking were observed by increasing the baffle angle, resulting in increased pressure drop value and friction. Finally, the temperature streamlines counter showed that the best baffle angle could be 135° in which maximum heat removal and the best thermal performance can be observed.

Thermal and electrical efficiencies enhancement of a solar photovoltaic-thermal/air system (PVT/air) using metal foams

Abstract: Photovoltaic-thermal (PVT) collectors, are useful systems to absorb solar energy and convert that to electrical and thermal energy. However, to make the best out of solar irradiation, it is vital to improve the thermal and energy efficiencies of such systems. Porous metal foams are suggested to be utilized in the present study for cooling of the PV cells and increase the thermal and electrical efficiencies. Moreover, the effects of various parameters, such as porous layer thickness, solar heat flux, and Reynolds number on these efficiencies are investigated numerically. Results mainly focus on the effects of the porous media on both thermodynamic and hydrodynamic characteristics of the system, i.e., velocity profiles and the pressure drop. The results indicated that the usage of porous media can improve both efficiencies (between 3 and 4% for the electrical and between 10 and 40% for the thermal efficiency) with a subsequent pressure loss. But for cases with a thickness of more than half of the channel height, it has a negative effect. In the best condition, Rp=0.5, the overall efficiency reaches up to 95%, however, in this case, the pressure drop rises considerably (up to 600 Pa), which causes destructive effects on the system and imposes additional costs.

Direct Comparison of Immersion and Cold-Plate Based Cooling for Automotive Li-Ion Battery Modules

Abstract: The current paper evaluates the thermal performance of immersion cooling for an Electric Vehicle (EV) battery module comprised of NCA-chemistry based cylindrical 21700 format Lithium-ion cells. Efficacy of immersion cooling in improving maximum cell temperature, cell’s temperature gradient, cell-to-cell temperature differential, and pressure drop in the module are investigated by direct comparison with a cold-plate-cooled battery module. Parametric analyses are performed at different module discharge C-rates and coolant flow rates to understand the sensitivity of each cooling strategy to important system performance parameters. The entire numerical analysis is performed using a validated 3D time-accurate Computational Fluid Dynamics (CFD) methodology in STAR-CCM+. Results demonstrate that immersion cooling due its higher thermal conductance leads to a lower maximum cell temperature and lower temperature gradients within the cells at high discharge rates. However, a higher rate of heat rejection and poor thermal properties of the dielectric liquid results in a much higher temperature non-uniformity across the module. At lower discharge rates, the two cooling methods show similar thermal performance. Additionally, owing to the lower viscosity and density of the considered dielectric liquid, an immersion-cooled battery module performs significantly better than the cold-plate-cooled module in terms of both coolant pressure drop.

Two dimensional unsteady stagnation point flow of Casson hybrid nanofluid over a permeable flat surface and heat transfer analysis with radiation

Abstract: The inclined magnetohydrodynamic (MHD) unsteady flow and heat transfer of Casson hybrid nanofluid (HNF) due to porous stretching sheet is investigated. In the present paper we analyze the Casson fluid unsteady flow over permeable flat plate in the presence of inclined magnetic field and heat transfer of fluid with the effect of thermal radiation. The conservation of mass, conservation of momentum and thermal equations are non-dimensional into the system of nonlinear ODEs by taking the suitable similarity transformation. An exact analytical solution is obtained for velocity. The energy equation in the presence of inclined magnetic field and radiation is a differential equation with variable coefficients, which is transformed to an incomplete gamma function using a new variable and using the Rosseland approximation for the radiation. The governing differential equations are solved analytically and the effects of various parameters on velocity profiles, skin friction coefficient, temperature profile and wall heat transfer are presented graphically. There is an enhancement in heat transfer and pressure drop by usage of HNF. The variations in velocity and temperature profiles with respect to different various pertinent physical parameters. An increase of the mass transpiration (suction) parameter intensity increases the skin friction, which consequently improves the heat transfer enhancement and reduces the HNF temperature. Furthermore, the skin friction coefficient increases due to mass suction and MHD in the stretching sheet, whereas the rate of heat transfer decays. The results have possible technological applications in liquid-based systems involving stretchable materials.

An investigation on the influence of the shape of the vortex generator on fluid flow and turbulent heat transfer of hybrid nanofluid in a channel

Abstract: The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a two-dimensional rectangular channel with triangular and semicircular vortex generators with three different heights of 1, 2 and 3 mm. For numerically modeling this study, SIMPLEC algorithm was used. Therefore, initially, the geometry of channel and the grid points were generated, and then for solving the mathematical equations via finite volume method, ANSYS Fluent was used. The results indicate that with an increase in Reynolds number and volume fraction (φ) of nanoparticles, the average Nusselt number increases. Also, with an increase in the φ, the pressure loss in the channel increases. About the geometrical shape of the vortex generators, results indicate that with using the semicircular vortex generator, average Nusselt number is higher compared to that of triangular vortex generator. Also, by investigating the performance evaluation criteria of thermal–hydraulic, which is a criterion for comparing the positive effect of the Nusselt number increase with the negative effect of pressure drop, results indicate that this criterion is higher for the semicircular vortex generator.