Flow control in microfluidics devices: electro-osmotic Couette flow with joule heating effect

Purpose – Joule heating effect is a pervasive phenomenon in electro-osmotic flow because of the applied electric field and fluid electrical resistivity across the microchannels. Its effect in electro-osmotic flow field is an important mechanism to control the flow inside the microchannels and it includes numerous applications. Design/methodology/approach – This research article details the numerical investigation on alterations in the profile of stream wise velocity of simple Couette-electroosmotic flow and pressure driven electro-osmotic Couette flow by the dynamic viscosity variations happened due to the Joule heating effect throughout the dielectric fluid usually observed in various microfluidic devices. Findings – The advantages of the Joule heating effect are not only to control the velocity in microchannels but also to act as an active method to enhance the mixing efficiency. The results of numerical investigations reveal that the thermal field due to Joule heating effect causes considerable variation of dynamic viscosity across the microchannel to initiate a shear flow when EDL (Electrical Double Layer) thickness is increased and is being varied across the channel. Originality/value – This research work suggest how joule heating can be used as en effective mechanism for flow control in microfluidic devices

Effect of non-conjugate and conjugate condition on heat transfer from the battery pack

Li-ion battery packs provide high energy density but with a concern of thermal management. Hence cooling mechanism is necessary to have a good life and reliability on the battery system. The main objective of this article is to investigate the effect of conjugate and non-conjugate boundary conditions on battery pack heat transfer characteristics. In conjugate conditions, coolant flow is considered with heat flux continuity at the battery and fluid interface. In non-conjugate condition, just convection condition is adopted. The finite volume method is adopted for the numerical analysis, and a code is written for computations of the governing equations. Effects of different parameters like heat generation, conductivity ratio, coolants, and Biot number on temperature distribution in the battery pack are analyzed. The maximum temperature contours are located near the top end of the battery, whereas at the bottom end, the battery’s temperature is low. Such high and low-temperature regions in the battery pack create uneven thermal stresses, resulting in battery failure. To have better performance results for the battery system, one should maintain the proper balance of thermal conductivity between the solid and fluid domains. From the comparative analysis, it is found that the non-conjugate condition gives the temperature distribution in the battery to be of symmetrical nature and more uniform. Practically, this is not true which is confirmed by the realistic conjugate condition where the high-temperature zones are closer to the trailing edge of the battery pack. Liquid metals and nanofluids provide a much safer operating temperature of the pack where the maximum temperature is well below the critical temperature. The application of conjugate conditions for battery thermal analysis leads to having an insight of the hotspot zones accurately which are operated using conventional fluids mentioned in this work

Experimental study on flexural strengthening of RC beams with NSM technique by different orientation of CFRP laminate

This paper gives the brief description on the use of laminates manufactured using Carbon Fiber Reinforced Polymer (CFRP) as strengthening material for the purpose of assessing the flexural strength in RC beams using Near Surface Mounted (NSM) technique. The main objective of this work was to assess the strengthened RC beam by considering the orientation of laminate as the main priority in NSM strengthening. This study gives the brief description about the utilization of tensile strength of laminate and efficiency of adhesive for different orientation of laminate. The strengthening methodologies adopted in this research work are Near Surface Mounted Laminate with Vertical Orientation (NSMLV), Near Surface Mounted Laminate with Vertical Orientation having Anchorages (NSMLVA) and Near Surface Mounted Laminate with Horizontal Orientation (NSMLH). The dimension of beam used was 200 mm (Breadth) X 200 mm (Depth) X 2300 mm (Length) and the effective span of the beam was considered as 2100 mm. All beams were designed as per Indian design code requirement to operate in under reinforcement criteria. A total of eight beams were casted, out of which two were used as control beams and the remaining were strengthened with different NSM techniques. The groove size used for NSMLV and NSMLH technique were different. The premature debonding takes place in NSMLV technique by not utilizing the tensile strength of laminate to greater extent, to overcome this drawback CFRP fabrics were used as the anchorages in four critical locations where debonding is predominate and this method was expressed as NSMLVA technique. This work was mainly focused on improving the ultimate load carrying capacity by satisfying the serviceability requirement as per codal provisions. The four-point bending test was performed for all the test specimens. In comparison with the control beams, all strengthened beams showed improved ultimate loads by satisfying the serviceability requirement. The ultimate load shows an increase of 21.74 %, 40.22% and 71.74% for NSMLV, NSMLVA and NSMLH technique respectively compared to control beams. The Stiffness of beam was increased by 14% and 30% respectively for NSMLVA and NSMLH technique compared to control beams. NSMLH technique maximizes ultimate load, which is 71.74% higher, and fulfills the serviceability requirements. In comparison with NSMLV and NSMLVA, the NSMLH Technique is the most effective method of strengthening which bears debonding to maximum extent and increases ultimate load by greater margin

Effect of using hybrid nanofluids as a coolant on the thermal performance of portable thermoelectric refrigerators

This study investigated the effect of using hybrid nanofluids as a refrigerant in portable thermoelectric refrigerator applications on thermal performance. For this purpose, a cooling cabinet with an internal volume of 36 L was designed and produced. Then, the Peltier assembly, with a water-cooled block attached to its hot surface, was placed in this cooling cabinet from the middle of its front cover. With the help of a refrigerant, the heat was removed from the Peltier's hot surface and transferred to the atmosphere via a water-to-air heat exchanger. Hybrid nanofluids prepared with Al2O3-TiO2-SiO2 and nanoparticles and water were used as the refrigerant in the system. To evaluate the thermal performances of these hybrid nanofluids, the tests were repeated using water without added nanoparticles as the reference case. According to the results obtained from the experimental study, it was observed that in all cases, tests using nanofluids gave better results than the reference cases. In addition, it was determined that the efficiency obtained from the system increased as the nanoparticle ratio in the mixture increased in all cases. Despite significant improvements in cooling cabinet and cooled product temperatures in hybrid nanofluids, the COP values ​​of the systems are slightly lower than in the reference case due to the Peltier effect. Considering the difference between the first and last temperatures of the cooled cabinet, the greatest improvement compared to the reference situation was determined as 30.3 % in the case of loaded state conditions and in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. For the unloaded conditions, this value was obtained as 25.1 % in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. On the other hand, for the unloaded condition, the lowest COP value was calculated as 0.47 and 0.45 when Al2O3-TiO2-SiO2-Water nanofluid was used in 1 % and 2 % mass fraction, respectively. For the loaded condition, this value was found as 0.48 in the case where 1 % Al2O3-TiO2-SiO2-Water and 0.47 in the case where 2 % Al2O3-TiO2-SiO2-Water nanofluid was used

Entropy Generation Analysis of Peristaltic Flow of Nanomaterial in a Rotating Medium through Generalized Complaint Walls of Micro-Channel with Radiation and Heat Flux Effects

This study discusses entropy generation analysis for a peristaltic flow in a rotating medium with generalized complaint walls. The goal of the current analysis is to understand the fluid flow phenomena particular to micro devices. Nano materials with a size less than 100 nm have applications in micro heat exchangers to cool electronic circuits, blood analyzers, biological cell separations, etc. For this study, we considered the effects of radiation, viscous dissipation and heat flux on the flow of nanomaterial inside a cylindrical micro-channel. To investigate the slip effects on the flow, the second order slip condition for axial velocity, the first order slip condition for secondary velocity and the thermal slip conditions were used. The flow was governed by partial differential equations (PDE’s), which were turned into a system of coupled ordinary differential equations (ODE’s) that were highly non-linear and numerically solved using the NDSolve command in Mathematica. The impacts of different involved parameters on the flow field were investigated with the aid of graphical illustrations. Entropy generation and the Bejan number were given special attention, and it was found that they decreased as the Hartman number, rotation, and radiation parameters increased

Shrinkage Study and Strength Aspects of Concrete with Foundry Sand and Coconut Shell as a Partial Replacement for Coarse and Fine Aggregate

The demand for natural aggregates (river sand) is increasing day by day, leading to the destruction of the environment, a burden that will be passed on to young people. Further, wastes from various industries are being dumped in landfills, which poses serious environmental problems. In order to ensure sustainability, both the issues mentioned above can be solved by utilizing industrial waste as aggregate replacement in the concrete construction industry. This research is done to find out the results using two substances viz., waste foundry sand (WFS) and coconut shell (CS) substitute for river sand and coarse aggregate. Many researchers have found the maximum benefits of substituted substances used in cement, which has material consistency. This current observation explores these strong waste properties of waste-infused concrete and cement, which experience shrinkage from drying out. The replacement levels for waste foundry sand were varied, between 10%, 20%, and 30%, and for CS, it was 10% and 20%. The experimental outcomes are evident for the strength, which increases by using WFS, whereas the strength decreases by increasing the CS level. The concrete that experiences shrinkage from drying out is included in the waste material, showing a higher magnitude of drying shrinkage than conventional concrete

Response Surface Methodology Based Optimization of Test Parameter in Glass Fiber Reinforced Polyamide 66 for Dry Sliding, Tribological Performance

The tribological performance of a glass fiber reinforced polyamide66 (GFRPA66) composite with varying fiber weight percentage (wt.%) [30 wt.% and 35 wt.%] is investigated in this study using a pin-on-disc tribometer. GFRPA66 composite specimens in the form of pins with varying percentages of fiber viz., 30 wt.% and 35 wt.% are fabricated by an injection molding process. Tribological performances, such as coefficient of friction (COF) and the specific wear rate (SWR), are investigated. The factors affecting the wear of GFRPA66 composites [with 30 wt.% and 35 wt.% reinforcements] are identified based on the process parameters such as load, sliding velocity, and sliding distance. Design Expert 13.0 software is used for the experimental data analysis, based on the design of experiments planned in accordance with the central composite design (CCD) of the response surface methodology (RSM) technique. The significance of the obtained results are analyzed using analysis of variance (ANOVA) techniques. To attain minimum SWR and COF, the wear performance is optimized in dry sliding conditions. The analysis of experimental data revealed that SWR and COF increased with increasing load, sliding velocity, and sliding distance for GFRPA66 [30 wt.%], but decreased with increasing polyamide weight percentage. The SWR for a maximum load of 80 N, and for a sliding velocity of 0.22 m/s, and a sliding distance of 3500 m for GFRPA66 composite specimens with 30 wt.% reinforcements are found to be 0.0121 m3/Nm, while the SWR for the same set of parameters for GFRPA66 composite specimens with 35 wt.% reinforcements are found to be 0.0102 m3/Nm. The COF for the GFRPA66 composite specimens with 30 wt.% reinforcements for the above set of parameters is found to be 0.37, while the GFRPA66 composite specimens with 35 wt.% reinforcements showed significant improvement in wear performance with a reduction in COF to 0.25. Finally, using a scanning electron microscope (SEM), the worn surfaces of the GFRPA66 are examined and interpreted

The influence of exhaust gas recirculation on the characteristics of compression ignition engines powered by tamanu methyl ester

This study aims to assess the performance of compression ignition (CI) engine powered with various biodiesels. The engine used for this test was a single-cylinder, water-cooled, naturally aspirated, CI engine. The biodiesels used in this study were neem methyl ester (NME), mahua methyl ester (MME), cottonseed methyl ester (CME), tamanu methyl ester (TME) and Albizia saman methyl ester (AME). According to the results, the TME-operated CI engine had 2.69%, 10.53%, 6.31% and 5.49% higher brake thermal efficiency than the MME, NME, CME and AME, respectively, without exhaust gas recirculation (EGR). Tamanu biodiesel outperformed the other test fuels in terms of performance and emissions. As a result, tamanu biodiesel was chosen as the best fuel for further testing. The results showed that tamanu biodiesel emitted more oxides of nitrogen (NOx) emissions than diesel. EGR could be used with the CI engine, resulting in a significant reduction in NOx emission. Compared to tamanu biodiesel without EGR conditions, the percentages of EGR 5%, 10% and 15% used with TME-operated CI engine produced 9.9%, 18% and 21.3% less NOx emission. The combination of EGR and tamanu biodiesel resulted in a slight increase in hydrocarbon, smoke and carbon monoxide emissions but a substantial reduction in NOx emissions. According to the study's findings, tamanu biodiesel with 10% EGR demonstrated optimal engine characteristics while having a low environmental impact

Magnetic Dipole and Thermophoretic Particle Deposition Impact on Bioconvective Oldroyd-B Fluid Flow over a Stretching Surface with Cattaneo–Christov Heat Flux

This study emphasizes the performance of two-dimensional electrically non-conducting Oldroyd-B fluid flowing across a stretching sheet with thermophoretic particle deposition. The heat and mass transfer mechanisms are elaborated in the presence of a magnetic dipole, which acts as an external magnetic field. The fluid possesses magnetic characteristics due to the presence of ferrite particles. The gyrotactic microorganisms are considered to keep the suspended ferromagnetic particles stable. Cattaneo–Christov heat flux is cogitated instead of the conventional Fourier law. Further, to strengthen the heat transfer and mass transfer processes, thermal stratification and chemical reaction are employed. Appropriate similarity transformations are applied to convert highly nonlinear coupled partial differential equations into non-linear ordinary differential equations (ODEs). To numerically solve these ODEs, an excellent MATLAB bvp4c approach is used. The physical behavior of important parameters and their graphical representations are thoroughly examined. The tables are presented to address the thermophoretic particle velocity deposition, rate of heat flux, and motile microorganisms’ density number. The results show that the rate of heat transfer decreases as the value of the thermal relaxation time parameter surges. Furthermore, when the thermophoretic coefficient increases, the velocity of thermophoretic deposition decreases