Search results

This performative chapter offers three movements that celebrate aspects of Norman Denzin's prolific and influential career: an ode to an aging cowboy that signal's Denzin's work on the West and Native Americans, a corresponding piece that signals Denzin's commitments to performance studies and autoethnography, and a litany of his scholarship as a bibliography of worship with his commitment to critical and creative forms of writing.

The purpose of this paper is to present a numerical analysis of the flow and heat transfer in a tube with a wire coil insert. A second law analysis of the results is accounted for, in order to assess the local and overall entropy generation in relation with the increased pressure drop and convective heat transfer. A wire coil with p/D=1.25 and e/D=0.076 is selected as insert device. A Reynolds number range between 100 and 1,000 is investigated, which corresponds to the typical operating regimes in the risers of liquid solar collectors. Different wall heat fluxes and inclination angles allow to analyze the potential impact of mixed convection in the presence of tube inserts.

Three-dimensional numerical simulations are performed using a finite-volume solver, assuming laminar flow conditions. Pure water and a mixture of water and propylene-glycol (20 percent) are used as working fluids, with temperature-dependent properties. Fanning friction factor, Nusselt number and local entropy generation results are obtained in the fully developed region.

The friction factor results are successfully compared with a well-known experimental correlation for wire coil inserts. The earlier onset of transition is devised at Re > 300. Nusselt number augmentations between 2.5- and 6-fold are reported with respect to the smooth tube. The mixed convection regime encountered in the smooth tube for the operating conditions investigated is canceled in the wire coiled tube, owing to the opposed effect of the swirl flow induced and the bouyancy forces. Frictional, heat transfer and overall entropy generation rates are computed locally in the fully developed region, allowing to relate these results with the flow structures in the mixed convection smooth tube and in the wire coiled tube. A threefold decrease in the entropy generation rate is reported for tubes with wire coil inserts.

An holistic understanding of the heat transfer enhancement in tubes with wire coil inserts is provided through the analysis of the flow pattern, Fanning friction factor, Nusselt number and local entropy generation rates. The reduced entropy generation in the enhanced tube serves as a performance criteria to confirm the positive effect of wire coil inserts in heat transfer for the operating regime under investigation, in spite of the increased pressure drop.

A computational fluid dynamics based parametric analysis for shell and helical tube heat exchanger (SHTHE) using CuO/water and Al₂O₃/water nanofluids is the main purpose of the present work. The parameters having impact on the performance of a heat exchanger have been studied in depth. As the solid nanoparticle shows higher thermal conductivity compared to liquid particles, inclusion of this nanoparticle into the base fluid significantly enhances the thermal conductivity of the liquid. Incorporation of nanofluid in the heat exchanger can increase its performance.

The simulation is performed in Solid-Works flow simulation, and the performance of SHTHE is observed by varying the pitch of helical tube from 0.013 to 0.018 m and coil diameter from 0.0813 to 0.116 m, keeping the other parameters constant. The tube side and shell side flow rate is kept as 2 LPM.

The results indicate that the effectiveness of the heat exchanger increases with the increase of pitch and coil diameter. The maximum effectiveness of 0.5022 for CuO/water and 0.4928 for Al₂O₃/water nanofluid is observed at a pitch of 0.018 m and the coil diameter of 0.116 m.

It is observed that CuO/water nanofluid shows better performance compared with Al₂O₃/water nanofluid. For a coil diameter of 0.116 m and pitch of 0.018 m, the SHTHE with CuO/water nanofluid shows 1.82% greater effectiveness compared to the effectiveness with Al₂O₃/water nanofluid.

This paper aims to present the numerical models and experimental outcomes pertain to the performance of the parabolic dish concentrator system with a modified cavity-type receiver (hemispherical-shaped).

The numerical models were evolved based on two types of boundary conditions; isothermal receiver surface and non-isothermal receiver surface. For validation of the numerical models with experimental results, three statistical terms were used: mean of absolute deviation, R² and root mean square error.

The thermal efficiency of the receiver values obtained using the numerical model with a non-isothermal receiver surface found agreeing well with experimental results. The numerical model with non-isothermal surface boundary condition exhibited more accurate results as compared to that with isothermal surface boundary condition. The receiver heat loss analysis based on the experimental outcomes is also carried out to estimate the contributions of various modes of heat transfer. The losses by radiation, convection and conduction contribute about 27.47%, 70.89% and 1.83%, in the total receiver loss, respectively.

An empirical correlation based on experimental data is also presented to anticipate the effect of studied parameters on the receiver collection efficiency. The anticipations may help to adopt the technology for practical use.

The developed models would help to design and anticipating the performance of the dish concentrator system with a modified cavity receiver that may be used for applications e.g. power generation, water heating, air-conditioning, solar cooking, solar drying, energy storage, etc.

The originality of this manuscript comprising presenting a differential-mathematical analysis/modeling of hemispherical shaped modified cavity receiver with non-uniform surface temperature boundary condition. It can estimate the variation of temperature of heat transfer fluid (water) along with the receiver height, by taking into account the receiver cavity losses by means of radiation and convection modes. The model also considers the radiative heat exchange among the internal ring-surface elements of the cavity.

The study aims to use nanofluids as coolants for improving heat transfer peculiarities of plate heat exchangers (PHE). The experimental and numerical investigations are thoroughly performed using distilled water-based Al₂O₃, graphene nanoplatelet (GnP) and multi-walled carbon nanotubes (MWCNT) nanofluids.

The numerical simulation based on Single Phase Model (SPM) was performed on a realistic 3 D model of PHE having similar dimensions as of the actual plate. The standard k-epsilon turbulent model was used to solve the problem. The concentration and flow rate of nanofluids were ranging from 0.1 to 1 Vol.% and 1 to 5 lpm, respectively, at 30°C. Whereas, hot side fluid is distilled water at 2 lpm and 80°C. The heat transfer characteristics such as bulk cold outlet temperature, heat transfer rate (HTR), heat transfer coefficient (HTC), Nusselt number (Nu), pressure drop, pumping power, effectiveness and exergy loss were experimentally evaluated using nanofluids in a PHE.

The experimental results were then compared with the numerical model. The experimental results revealed maximum enhancement in an average heat transfer rate of 9.86, 14.86 and 17.27% using Al₂O₃, GnP and MWCNT nanofluids, respectively, at 1 Vol.%. The present computational fluid dynamics model accurately predicts HTR, and the results deviate <1.1% with experiments for all the cases. The temperature and flow distribution show promising results using nanofluids.

The study helps to visualise heat transfer and flow distribution in PHE using different nanofluids under different operating conditions.

Wireless power transfer (WPT) technology is explored as a promising solution for electric vehicle (EV) charging due to its convenience and potential to overcome traditional charging limitations. This study aims to present a novel lightweight magnetic coupler design, square grid structure (SGS), specifically aimed at enhancing interoperability and robustness in the presence of misalignments for primary-side impedance tuning WPT systems adapted for EVs.

The proposed coupler design uses the finite element analysis method through ANSYS Electronics Desktop software for optimization. A comprehensive comparative analysis is conducted, focusing on critical magnetic parameters such as coupling coefficient (k), mutual inductance (M) and self-inductance (L) for different air gaps. Three other coupler designs, including circular, rectangular and DD configurations, are considered in the evaluation process. Additionally, the performance of the proposed coupler is assessed through misalignment tolerance in different directions, magnetic flux density (B), magnetic field strength (H), Energy density, Quality factor (Q) with mesh generation and thermal analysis using ANSYS Icepak design software.

The study presents findings from the comprehensive analysis, highlighting the performance of the proposed SGS coupler in terms of different key magnetic parameters, misalignment tolerance in different directions and various operational conditions. To verify the result for Practical implementation, MATLAB Simulink demonstrates a remarkable power transfer efficiency (PTE) of 94\%, exceeding alternative coupler designs. These findings emphasize the potential of the lightweight magnetic coupler to enhance the performance and practicality of WPT systems for EVs.

Although the study offers valuable insights into the proposed SGS coupler design, there might be restrictions due to their hardware design being complex compared to other couplers and particular operating circumstances or environmental elements that were not considered during the investigation. Future studies could investigate these areas, focusing more on the shielding method to provide a more thorough knowledge of the coupler’s functionality.

This work advances WPT technology by presenting a novel SGS coupler design, which provides a robust and efficient solution for EV charging. The suggested lightweight magnetic coupler’s novelty and value in addressing the growing need for sustainable transportation solutions are highlighted by the significant improvement of 94% PTE.

The purpose of this paper is to evaluate the performance of table type radio frequency identification (RFID) reader and verify the effect of the use of a parasitic element on the table type RFID reader to increase the communication performance and improve the automatic identification of books in the library.

In this study, the authors observe the magnetic field at each point on the reader by using a small probe antenna and evaluate the reading performance of table type RFID reader at each point on the reader by using a RFID tag. Furthermore, to increase the communication performance, they add a parasitic element on the table type RFID reader and evaluate its usefulness.

The power distribution on the table type RFID reader and the communication performance of the table type REID reader were clearly shown. From the experiments of the magnetic field observation, when the coil surface of a tag is put in the parallel with the antenna plane of the reader, the tag can obtain electric power from the reader most effectively. Furthermore, by using a loop coil between the reader and the tag as a parasitic element, the points where communication is enabled with tag increased as the number of turns of coil increased.

In this research work, the author clearly showed the table type RFID reader’s performance by experiment. Moreover, to increase the communication performance, the author proposed to add a parasitic element to the table type RFID leader.

The electromagnetic field and cooling system of a high power switched reluctance motor (SRM) are studied numerically. The geometry of the motor and its main components are established using a computer-aided design software in the actual size. This study aims to evaluate the resulting thermal losses using the electromagnetic analysis of the motor.

In the electromagnetic analysis, the Joule’s loss in the copper wires of the coil windings and the iron losses (the eddy currents loss and the hysteresis loss) are considered. The flow and heat transfer model for the thermal analysis of the motor including the conduction in solid parts and convection in the fluid part is introduced. The magnetic losses are imported into the thermal analysis model in the form of internal heat generation in motor components. Several cooling system approaches were introduced, such as natural convection cooling, natural convection cooling with various types of fins over the motor casing, forced conviction air-cooled cooling system using a mounted fan, casing surface with and without heat sinks, liquid-cooled cooling system using the water in a channel shell and a hybrid air-cooled and liquid-cooled cooling system.

The results of the electromagnetics analysis show that the low rotational speed of the motor induces higher currents in coil windings, which in turn, it causes higher copper losses in SRM coil windings. For higher rotational speed of SRM, the core loss is higher than the copper loss is in SRM due to the higher frequency. An air-cooled cooling system is used for cooling of SRM. The results reveal when the rotational speed is at 4,000 rpm, the coil loss would be at the maximum value. Therefore, the coil temperature is about 197.9°C, which is higher than the tolerated standard temperature insulation material. Hence, the air-cooled system cannot reduce the temperature to the safe temperature limitation of the motor and guarantee the safe operation of SRM. Thus, a hybrid system of both air-cooled and liquid-cooled cooling system with mounting fins at the outer surface of the casing is proposed. The hybrid system with the liquid flow of Re = 1,500 provides a cooling power capable of safe operation of the motor at 117.2°C, which is adequate for standard insulation material grade E.

The electromagnetic field and cooling system of a high power SRM in the presence of a mounted fan at the rear of the motor are analyzed. The thermal analysis is performed for both of the air-cooled and liquid-cooled cooling systems to meet the cooling demands of the motor for the first time.

This study aims to solve the problem of the existing metal foreign object (MFO) detecting systems, which are not sensitive to the small size MFO in wireless charging region of electric vehicle (EV) because of the extremely complex signal noise in the process of wireless charging of EV.

A method for MFO detection based on the principle that MFOs can cause mistuned resonance of detection coil resonant circuit is proposed. The general scheme of detecting system is proposed. The design method for detection coils which is effective to small MFOs detection in large-area region of wireless charging of EV is presented. The design of time-sharing driving circuit and amplifying circuit of high frequency exciting signal for detection coils is introduced. The design scheme of signal processing circuit (including filter and rectifier) of detection coil terminal voltage is also proposed.

The influence of exciting frequency of detection coils on detecting sensitivity and the anti-noise feature of system are analyzed according to the experiment results.

The experiment of MFO detection indicates that the proposed method can effectively detect the coin-sized small MFO in the process of wireless charging of EV.