@article{anand_gould_2021, title={Analysis of a Symmetrical Ferrofluid Sloshing Vibration Energy Harvester}, volume={6}, ISSN={["2311-5521"]}, DOI={10.3390/fluids6080295}, abstractNote={Ferrofluid sloshing vibration energy harvesters use ferrofluid sloshing movement as a moving magnet between a fixed coil to induce current and, in turn, harvest energy from external excitations. A symmetric ferrofluid sloshing vibration energy harvester configuration is introduced in this study which utilizes four external, symmetrically placed, permanent magnets to magnetize a ferrofluid inside a tank. An external sinusoidal excitation of amplitude 1 m/s2 is imparted, and the whole system is studied numerically using a level-set method to track the sharp interface between ferrofluid and air. The system is studied for two significant length scales of 0.1 m and 0.05 m while varying the four external magnets’ polarity arrangements. All of the system configuration dimensions are parametrized with the length scale to keep the system configuration invariant with the length scale. Finally, a frequency sweep is performed, encompassing the structure’s first modal frequency and impedance matching to obtain the system’s energy harvesting characteristics.}, number={8}, journal={FLUIDS}, author={Anand, Nadish and Gould, Richard}, year={2021}, month={Aug} }
@article{watkins_chilamkurti_gould_2020, title={Analytic Modeling of Heat Transfer to Vertical Dense Granular Flows}, volume={142}, ISSN={["1528-8943"]}, DOI={10.1115/1.4045311}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, author={Watkins, Megan F. and Chilamkurti, Yesaswi N. and Gould, Richard D.}, year={2020}, month={Feb} }
@article{chilamkurti_gould_2020, title={CFD-DEM and PR-DNS studies of low-temperature densely packed beds}, volume={159}, ISSN={["1879-2189"]}, DOI={10.1016/j.ijheatmasstransfer.2020.120056}, abstractNote={Over the past few decades, granular media is gaining attention as a viable option for heat transfer fluids (HTFs). Several research efforts are studying the use of particle-based heat transfer fluids in a wide variety of applications. With this motivation, the current work focusses on analyzing the different heat transfer mechanisms in low-temperature mono-sized densely packed granular media. To study the heat transfer behavior of granular media at different scales, the current work employs a two-way coupled computational strategy. The motion of particles is solved using the Discrete Element Method (DEM) and the interstitial air is solved using a Finite-Volume (CFD) approach. The Open-Source library CFDEM Coupling® is used in the current study to join the Finite Volume PISO solver of OpenFOAM® and the DEM solver of LIGGGHTS®. Typically, particle-particle contact conduction and particle-air convection are the most popular closure models. But recent research identified a different heat transfer phenomenon in packed beds that cannot be identified by conduction or convection models. Though closure models were developed to implement this on a CFD-DEM framework, they did not capture the effect of intra-particulate thermal gradients on this phenomenon. Hence the current work also employs Particle-Resolved Direct Numerical Simulations (PR-DNS) to gain valuable insights allowing for the modification of existing models. A new closure model is then proposed here and is implemented in the CFD-DEM framework. This model provides key insights into the different heat transfer mechanism of packed beds.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Chilamkurti, Yesaswi N. and Gould, Richard D.}, year={2020}, month={Oct} }
@article{watkins_gould_2019, title={Experimental Characterization of Heat Transfer to Vertical Dense Granular Flows Across Wide Temperature Range}, volume={141}, ISSN={["1528-8943"]}, DOI={10.1115/1.4042333}, abstractNote={Particle-based heat transfer fluids for concentrated solar power (CSP) tower applications offer a unique advantage over traditional fluids, as they have the potential to reach very high operating temperatures. Gravity-driven dense granular flows through cylindrical tubes demonstrate potential for CSP applications and are the focus of the present study. The heat transfer capabilities of such a flow system were experimentally studied using a bench-scale apparatus. The effect of the flow rate and other system parameters on the heat transfer to the flow was studied at low operating temperatures (<200 °C), using the convective heat transfer coefficient and Nusselt number to quantify the behavior. For flows ranging from 0.015 to 0.09 m/s, the flow rate appeared to have negligible effect on the heat transfer. The effect of temperature on the flow's heat transfer capabilities was also studied, examining the flows at temperatures up to 1000 °C. As expected, the heat transfer coefficient increased with the increasing temperature due to enhanced thermal properties. Radiation did not appear to be a key contributor for the small particle diameters tested (approximately 300 μm in diameter) but may play a bigger role for larger particle diameters. The experimental results from all trials corroborate the observations of other researchers; namely, that particulate flows demonstrate inferior heat transfer as compared with a continuum flow due to an increased thermal resistance adjacent to the tube wall resulting from the discrete nature of the flow.}, number={3}, journal={JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, author={Watkins, Megan F. and Gould, Richard D.}, year={2019}, month={Mar} }
@inproceedings{anand_gould_2017, title={A convenient low order thermal model for heat transfer characteristics of single floored low-rise residential buildings}, DOI={10.1115/imece2016-65254}, abstractNote={A low order thermal model is introduced to determine the thermal characteristics of a Low-Rise Residential (LRR) building and then predict the energy usage by its Heating Ventilation & Air Conditioning (HVAC) system according to future weather conditions. The LRR buildings are treated as a simple lump and the model is derived using the lumped capacitance model for transient heat transfer from bodies. Most contemporary HVAC systems have a thermostat control, which has an offset temperature, and user defined set point temperatures, which defines when the HVAC system will switch on and off. The aim is to predict, with minimal error, the inside air temperature, which is used to determine the switching on and off, of the HVAC system. To validate this lumped capacitance model we have used the EnergyPlus simulation engine, which simulates the thermal behavior of buildings with considerable accuracy. We have predicted using the low order model the inside air temperature of a single family house located in three different climate zones (Detroit, Raleigh & Austin) and different orientations for summer and winter seasons. The prediction error between the model and EnergyPlus is less than 10% for almost all the cases with the exception of Austin in summer. Possible factors responsible for error in prediction are also noted in this work, paving way for future research.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2016, vol. 6b}, author={Anand, N. and Gould, R. D.}, year={2017} }
@inproceedings{chilamkurti_gould_2017, title={Characterizing particle-wall contact behavior and fluctuations in gravity-driven dense granular flows in cylindrical tubes using dem}, booktitle={Proceedings of the ASME Power Conference Joint with ICOPE-17, 2017, vol 2}, author={Chilamkurti, Y. N. and Gould, R. D.}, year={2017} }
@inproceedings{watkins_gould_2017, title={Heat transfer to vertical dense granular flows at high operating temperatures}, DOI={10.1115/es2017-3272}, abstractNote={Ceramic particles as a heat transfer fluid for concentrated solar power towers offers a variety of advantages over traditional heat transfer fluids. Ceramic particles permit the use of very high operating temperatures, being limited only by the working temperatures of the receiver components, as well as demonstrate the potential to be used for thermal energy storage. A variety of system configurations utilizing ceramic particles are currently being studied, including upward circulating beds of particles, falling particle curtains, and flows of particles over an array of absorber tubes. The present work investigates the use of gravity-driven dense granular flows through cylindrical tubes, which demonstrate solid packing fractions of approximately 60%. Previous work demonstrated encouraging results for the use of dense flows for heat transfer applications and examined the effect of various parameters on the overall heat transfer for low temperatures. The present work examined the heat transfer to dense flows at high operating temperatures more characteristic of concentrated solar power tower applications. For a given flow rate, the heat transfer coefficient was examined as a function of the mean flow temperature by steadily increasing the input heat flux over a series of trials. The heat transfer coefficient increased almost linearly with temperature below approximately 600°C. Above 600°C, the heat transfer coefficient increased at a faster rate, suggesting an increased radiation heat transfer contribution.}, booktitle={Proceedings of the asme 11th international conference on energy sustainability, 2017}, author={Watkins, M. F. and Gould, R. D.}, year={2017} }
@inproceedings{watkins_gould_2016, title={Dense granular flows as a new heat transfer fluid for concentrated solar power}, DOI={10.1115/imece2015-51069}, abstractNote={The increasing interest in concentrated solar power as a new form of renewable energy necessitates an improvement in overall system efficiency. Current heat transfer fluids employed to capture the concentrated heat demonstrate limited working temperature ranges. This study sought to investigate the use of dense granular flows as a possible new heat transfer fluid, as ceramic particles present virtually no restriction on working temperature. A bench-scale system simulating a single tube of a concentrated solar power central receiver was constructed and used to evaluate the heat transfer properties of the flow at low temperatures. Ceramic particles, 270μm in diameter, were gravity-fed through a vertical tube, resulting in granular flows with particle packing fractions of approximately 60%. Radial temperature profiles were measured and used to calculate the mean temperature of the fluid at different axial tube locations. The heat transfer coefficient was then calculated based on the input heat flux and measured wall and mean temperatures. The effect of the mass flow rate on the heat transfer coefficient was examined by using different orifices at the tube exit. As expected, the heat transfer coefficient increased with increasing flow rate. Heat transfer coefficients ranging from 330 to 380 W/m2-K were obtained for bulk temperatures ranging from 40 to 70°C. Previous works demonstrated comparable heat transfer coefficients at higher bulk temperatures. Thus, our preliminary heat transfer coefficient results demonstrate the potential of dense flows of ceramic particles for obtaining beneficial heat transfer properties at extremely high operating temperatures.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 8b}, author={Watkins, M. F. and Gould, R. D.}, year={2016} }
@inproceedings{chilamkurti_gould_2016, title={Discrete element studies of gravity-driven dense granular flows in vertical cylindrical tubes}, DOI={10.1115/power2016-59159}, abstractNote={The current paper focusses on the characterization of gravity-driven dry granular flows in cylindrical tubes. With a motive of using dense particulate media as heat transfer fluids (HTF), the main focus was to address the characteristics of flow regimes with a packing fraction of ∼60%. In a previous work [1], experimental and computational studies were conducted to understand the effects of different geometrical parameters on the flow physics. The current paper is an extension of that work to gain more insights into the granular flow physics. The three-dimensional computer simulations were conducted by implementing the Discrete Element Method (DEM) for the Lagrangian modelling of particles. Hertz-Mindilin models were used for the soft-particle formulations of inter-particulate contacts. Simulations were conducted to examine the particulate velocities and flow rates to understand the rheology in the dense flow regime. Past studies suggested the existence of a Gaussian mean velocity profile for dense gravity-driven granular flows. These observations were further analyzed by studying the influence of geometrical parameters on the same. The current work thus focusses on studying the rheology of dense granular flows and obtaining a better understanding of the velocity profiles, the wall friction characteristics, and the particle-wall contact behavior.}, booktitle={Proceedings of the ASME Power Conference, 2016}, author={Chilamkurti, Y. N. and Gould, R. D.}, year={2016} }
@inproceedings{watkins_gould_2016, title={Effect of flow rate and particle size on heat transfer to dense granular flows}, DOI={10.1115/es2016-59258}, abstractNote={The increasing demand for renewable energy sources necessitates the development of more efficient technologies. Concentrated solar power (CSP) towers exhibit promising qualities, as temperatures greater than 1000°C are possible. The heat transfer fluid implemented to capture the sun’s energy significantly impacts the overall performance of a CSP system. Current fluids, such as molten nitrate salts and steam, have limitations; molten salts are limited by their small operational temperature range while steam requires high pressures and is unable to act as an effective storage medium. As a result, a new heat transfer fluid composed of ceramic particles is being investigated, as ceramic particles demonstrate no practical limit on operation temperature and have the ability to act as a storage medium. This study sought to further investigate the use of dense granular flows as a new heat transfer fluid. Previous work validated the use of such flows as a heat transfer fluid; the present work examined the effect of flow rate, as well as the particle size and type on the heat transfer to the particle fluid. Three different types of particles were tested, along with two different diameter particles. Of the three materials tested, the particle type did not appear to effect the heat transfer. Particle diameter, however, did effect the heat transfer, as a smaller diameter particle yielded slightly higher heat transfer to the fluid. Flow rates ranging from 30 to 200 kg/m2-s were tested. Initially, the heat transfer to the flow, characterized by the convective heat transfer coefficient, decreased with increasing flow rate. However, at approximately 80 kg/m2-s, the heat transfer coefficient began to increase with increasing flow rate. These results indicate that a dense granular flow consisting of small diameter particles and traveling at very slow or fast flow rates yields the best wall to “fluid” heat transfer.}, booktitle={Proceedings of the ASME 10th International Conference on Energy Sustainability, 2016, vol 1}, author={Watkins, M. F. and Gould, R. D.}, year={2016} }
@inproceedings{chilamkurti_gould_2016, title={Experimental and computational studies of gravity-driven dense granular flows}, DOI={10.1115/imece2015-50762}, abstractNote={The current paper focusses on the characterization of gravity-driven dry granular flows in cylindrical tubes. With a motive of using dense particulate media as heat transfer fluids (HTF), the study was primarily focused to address the characteristics of flow regimes with a packing fraction of ∼60%. Experiments were conducted to understand the effects of different flow parameters, including: tube radius, tube inclination, tube length and exit diameter. These studies were conducted on two types of spherical particles — glass and ceramic — with mean diameters of 150 μm and 300 μm respectively. The experimental data was correlated with the semi-empirical equation based on Beverloo’s law. In addition, the same flow configuration was studied through three-dimensional computer simulations by implementing the Discrete Element Method for the Lagrangian modelling of particles. A soft-particle formulation was used with Hertz-Mindilin contact models to resolve the interaction forces between particles. The simulation results were used to examine the velocity, shear rate and packing fraction profiles to study the detailed flow dynamics. Curve-fits were developed for the mean velocity profiles which could be used in developing hydrodynamic analogies for granular flows. The current work thus identifies the basic features of gravity driven dense granular flows that could form a basis for defining their rheology.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2015, vol 7a}, author={Chilamkurti, Y. N. and Gould, R. D.}, year={2016} }
@article{rocha_bhattacharya_moghaddam_gould_paula_cardoso filho_2016, title={Thermal Stress and High Temperature Effects on Power Devices in a Fault-Resilient NPC IGCT-Based Converter}, volume={31}, ISSN={["1941-0107"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84960155689&partnerID=MN8TOARS}, DOI={10.1109/tpel.2015.2452262}, abstractNote={The integrated gate-commutated thyristor and presspack power diodes have been successfully applied in medium-voltage neutral point-clamped converters in the power range from hundreds of kilowatt to tenths of megawatt. Responsible for driving key processes in the industry, high reliability and availability are crucial for these converters, since their repair or replacement after failure events may take too long. Given the vital importance of such equipment for the drive systems, they are equipped with protection schemes that are usually reliable, but not infallible. If the protection scheme of the converter does not work properly in a short-circuit situation, serious damages may be expected on its power semiconductor devices. In this paper, the power semiconductors thermal behavior is investigated using finite-element models in the COMSOL Multiphysics software. Three-dimensional thermal models of the power devices were raised by industrial radiography techniques, aiming to expand the information provided by the manufacturers. The authors show how these results can be used in a real equipment to attenuate the catastrophic effects of the protection scheme malfunction, so limiting the damage pattern within the converter to their least complex power devices.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Rocha, Anderson Vagner and Bhattacharya, Subhashish and Moghaddam, Giti Karimi and Gould, Richard D. and Paula, Helder and Cardoso Filho, Braz de Jesus}, year={2016}, month={Apr}, pages={2800–2807} }
@inproceedings{karimi-moghaddam_gould_bhattacharya_2016, title={Thermomagnetic liquid cooling: A novel variable speed motor drives thermal management solution}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84965183324&partnerID=MN8TOARS}, DOI={10.1109/iemdc.2015.7409303}, abstractNote={Liquid cooling for thermal management has been extensively applied in high power electronic systems. However, the use of pumps may introduce reliability and mechanical limitations such as vibration, noise, leakage, and considerable power consumption. It has been shown that temperature sensitive ferrofluids in the presence of temperature field and magnetic field gradients are able to produce a liquid flow without a mechanical pump. This paper presents results from experiments using a single-phase, Mn-Zn ferrite based ferrofluid operating under transient and steady laminar flow conditions in a partially heated thermomagnetic circulation loop under the influence of an external magnetic field created by a solenoid. The effects of several operational factors on the system performance are discussed. Additionally, the self-regulating feature of this cooling system is demonstrated as the heat load is increased a larger heat dissipation rate can be managed due to a stronger thermomagnetic convection effect.}, booktitle={Proceedings - 2015 IEEE International Electric Machines and Drives Conference, IEMDC 2015}, author={Karimi-Moghaddam, G. and Gould, R.D. and Bhattacharya, Subhashish}, year={2016}, pages={1768–1773} }
@article{karimi-moghaddam_gould_bhattacharya_2014, title={A Nondimensional Analysis to Characterize Thermomagnetic Convection of a Temperature Sensitive Magnetic Fluid in a Flow Loop}, volume={136}, ISSN={["1528-8943"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84904479914&partnerID=MN8TOARS}, DOI={10.1115/1.4027863}, abstractNote={This paper presents results from theoretical and numerical studies of a single-phase, temperature sensitive magnetic fluid operating under steady-state laminar flow conditions in a partially heated thermomagnetic circulation loop under the influence of an external magnetic field (created by a solenoid). A one-dimensional theoretical model has been developed using scaling arguments to characterize thermomagnetic circulation in this loop in terms of the geometric length scales, magnetic fluid properties, and the strength of the imposed magnetic field. In parallel to this theoretical analysis, supporting numerical simulations using Comsol Multiphysics simulation software have been undertaken to obtain data for use in this 1D model. Comparison between experimental data and numerical simulation results and also a grid sensitivity analysis was carried out to validate the numerical simulation. A correlation for the nondimensional heat transfer (Nusselt number) as a function of the appropriate magnetic Rayleigh number and a correlation for the mass flow rate based on the system's properties are developed.}, number={9}, journal={JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, author={Karimi-Moghaddam, Giti and Gould, Richard D. and Bhattacharya, Subhashish}, year={2014}, month={Sep} }
@inproceedings{karimi-moghaddam_gould_bhattacharya_2013, title={A non-dimensional analysis to characterize thermomagnetic convection of a temperature sensitive magnetic fluid in a flow loop}, volume={8 B}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903451690&partnerID=MN8TOARS}, DOI={10.1115/imece2013-66313}, abstractNote={This paper presents results from theoretical and numerical studies of a single-phase, temperature sensitive magnetic fluid operating under steady-state laminar flow conditions in a partially heated thermomagnetic circulation loop under the influence of an external magnetic field (created by a solenoid). A one-dimensional theoretical model has been developed using scaling arguments to characterize thermomagnetic circulation in this loop in terms of the geometric length scales, magnetic fluid properties, and strength of the imposed magnetic field. In parallel to this theoretical analysis, supporting numerical simulations using COMSOL Multiphysics simulation software have been undertaken to obtain data for use in this 1D model. A correlation for the non-dimensional heat transfer (Nusselt number) as a function of the appropriate magnetic Rayleigh number and a correlation for the mass flow rate based on the system’s properties are developed.}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)}, author={Karimi-Moghaddam, G. and Gould, R.D. and Bhattacharya, Subhashish}, year={2013} }
@inproceedings{karimi-moghaddam_gould_bhattacharya_2013, title={Investigation of enhancement in pool boiling heat transfer of a binary temperature sensitive magnetic fluid}, volume={8 B}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903487625&partnerID=MN8TOARS}, DOI={10.1115/imece2013-66308}, abstractNote={In this paper, the performance of pool boiling heat transfer using a binary temperature sensitive magnetic fluid in the presence of a non-uniform magnetic field is investigated numerically. By using a binary magnetic fluid, enhanced boiling heat transfer is obtained by thermomagnetic convection without deterioration of properties of the fluid. This work is aimed at gaining a qualitative understanding the magnetic field effects on boiling heat transfer enhancement of magnetic fluids. In order to accomplish this, the boiling process and the effects of position of the external magnetic field on flow pattern and heat transfer are investigated in a 2D rectangular domain using COMSOL Multiphysics simulation software. Finally, the boiling curves for a binary temperature sensitive magnetic fluid and its base fluid (without magnetic particles) are compared for various applied heat flux magnitudes.}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)}, author={Karimi-Moghaddam, G. and Gould, R.D. and Bhattacharya, Subhashish}, year={2013} }
@inproceedings{karimi-moghaddam_rende_gould_bhattacharya_2012, title={Investigation of high performance heat sink characteristics in forced convection cooling of power electronic systems}, DOI={10.1115/imece2011-64318}, abstractNote={This study presents the experimental performance of a high fin density heat sink for semiconductor power modules — such as IGBTs. As a case study a commercially available extruded heat sink has been chosen. By analyzing the steady-state maximum temperatures as well as various geometric orientations, Nusselt number correlations were found experimentally, which can be used to predict the performance of the heat sink. It was found that the experimental Nusselt number correlations can predict the performance of the heat sink to within a 10%. Furthermore, steady-state maximum temperature results showed that for low fan speeds (2 m/s–3 m/s), the device junction temperatures achieved a value no higher than 80°C, which is well below the junction temperature limit for 125°C for silicon power semiconductor devices. Furthermore, it was shown that for two heat sinks in series forced convection tests, gap spacing between the devices has a minimal effect on the overall performance. Also, a numerical simulation study using COMSOL Multiphysics simulation software to study flow and temperature fields has been conducted. These modeling results the thermal behavior of heat sink are validated by experimental measurements.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2011, vol 11}, author={Karimi-Moghaddam, G. and Rende, C. and Gould, R. D. and Bhattacharya, S.}, year={2012}, pages={815–821} }
@inproceedings{dutta_moghaddam_bhattacharya_gould_2012, title={Novel power electronics overload and temperature rise and time interval prediction based on dynamic thermal modeling}, DOI={10.1115/imece2011-64048}, abstractNote={In this digest an overload predicting algorithm is proposed based on the converter operating point and the thermal model of a 6.5 KV Silicon IGBT module. This algorithm can predict both the overload and the time interval for overload and hence can be used for thermal cycle performance evaluation for converters.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2011, vol 11}, author={Dutta, S. and Moghaddam, G. K. and Bhattacharya, S. and Gould, R.}, year={2012}, pages={809–813} }
@inproceedings{karimi-moghaddam_gould_madhusoodhanan_hatua_bhattacharya_leslie_ryu_das_agarwal_grider_2012, title={Thermal design considerations for 12kV SiC n-IGBT based 3L NPC converter}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870903069&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342445}, abstractNote={Transformer less Intelligent Power Substation (TIPS) is a solid state replacement for the conventional bulky distribution transformers used for 13.8kV and 480V grid interconnectivity. A 100kVA 3L NPC converter is being built using 12kV SiC n-IGBT for the high voltage grid interface. In this paper, detailed thermal behavior of this converter is studied for optimum thermal design. The thermal profile at the die level at different power factor of operation is studied. This study helps the optimum component placement in the converter. Also it shows that the operating modes of the converter play a key role in optimum thermal design.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={Karimi-Moghaddam, G. and Gould, R.D. and Madhusoodhanan, S. and Hatua, K. and Bhattacharya, S. and Leslie, S. and Ryu, S.-H. and Das, M. and Agarwal, A. and Grider, D.}, year={2012}, pages={2180–2186} }
@inproceedings{wang_baek_elliott_kadavelugu_wang_she_dutta_liu_zhao_yao_et al._2011, title={Design and hardware implementation of Gen-1 silicon based solid state transformer}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955785263&partnerID=MN8TOARS}, DOI={10.1109/apec.2011.5744766}, abstractNote={This paper presents the design and hardware implementation and testing of 20kVA Gen-1 silicon based solid state transformer (SST), the high input voltage and high voltage isolation requirement are two major concerns for the SST design. So a 6.5kV 25A dual IGBT module has been customized packaged specially for this high voltage low current application, and an optically coupled high voltage sensor and IGBT gate driver has been designed in order to fulfill the high voltage isolation requirement. This paper also discusses the auxiliary power supply structure and thermal management for the SST power stage.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Wang, G. and Baek, S. and Elliott, J. and Kadavelugu, A. and Wang, F. and She, X. and Dutta, S. and Liu, Y. and Zhao, T. and Yao, W. and et al.}, year={2011}, pages={1344–1349} }
@article{cassidy_gould_2008, title={Temperature range and conjugate effects in microencapsulated phase-change suspensions}, volume={22}, ISSN={["0887-8722"]}, DOI={10.2514/1.33560}, abstractNote={The melting process of some phase-change materials does not occur at a single temperature, but rather occurs over a temperature range. The effect of a phase-change temperature range for microencapsulated phase-change-material slurry was investigated numerically for a hydrodynamically fully developed laminar flow in a circular tube with a constant wall heat flux. The wall temperature and exit radial temperature were investigated for several phase-change temperature ranges, including a single phase-change temperature. The dominant dimensionless parameters: Stefan number, melt temperature range, and subcooling were varied and results presented. For code verification, results were compared with previous experimental and numerical data using eicosane as the phase-change material. Using heat flow measurements over the melt region from current literature, a curve fit for eicosane was made and used in the numerical model. The numerical results compared well with existing experimental and numerical findings and showed the phase-change region was the cause of temperature discrepancies cited in previous numerical work.}, number={2}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Cassidy, Daniel and Gould, Richard D.}, year={2008}, pages={240–246} }
@article{chernyak_henon_harris_gould_franklin_edwards_desimone_carbonell_2001, title={Formation of perfluoropolyether coatings by the rapid expansion of supercritical solutions (RESS) process. Part 1: Experimental results}, volume={40}, ISSN={["0888-5885"]}, DOI={10.1021/ie010267m}, abstractNote={The rapid expansion of supercritical solutions (RESS) process is a promising environmentally benign technology for fine droplet or particle formation. The absence of organic solvents and narrow size distribution of RESS precipitates make this process attractive for polymer coating applications. In our work, this technique has been used to produce droplets of perfluoropolyethers from CO2 solutions without the aid of cosolvents for the coating of porous materials applied in monumental and civil infrastructures. The present work is aimed at gaining an understanding of the relationship between droplet and spray characteristics and RESS process conditions. As such, a combined experimental/computational approach is applied to a representative binary system consisting of a low-molecular-weight perfluoropolyether diamide (PFD) dissolved in supercritical CO2. Part 1 of this work presents phase equilibria measurements and polymer droplet size characterizations under different operating conditions. The effects of te...}, number={26}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Chernyak, Y and Henon, F and Harris, RB and Gould, RD and Franklin, RK and Edwards, JR and DeSimone, JM and Carbonell, RG}, year={2001}, month={Dec}, pages={6118–6126} }
@article{franklin_edwards_chernyak_gould_henon_carbonell_2001, title={Formation of perfluoropolyether coatings by the rapid expansion of supercritical solutions (RESS) process. Part 2: Numerical modeling}, volume={40}, ISSN={["0888-5885"]}, DOI={10.1021/ie010268e}, abstractNote={The rapid expansion of supercritical solutions (RESS) process is a promising method for the production of ultrafine powders and aerosols of narrow size distribution for coatings and other applications. In this article, part 2 of a two-part study, the nucleation and subsequent growth of 2500 Mw perfluoropolyether diamide (PFD) from supercritical carbon dioxide (CO2) by expansion through a small-diameter nozzle is modeled in a three-stage, multidimensional fashion. The stages include a hydrodynamic solution, solvent−solute phase equilibria analyses, and an aerosol transport model. The hydrodynamics model successfully captures the vapor−liquid transition that occurs as carbon dioxide is expanded to ambient conditions. Cloud-point pressures and equilibrium compositions of the separated solvent−solute system are determined and are used in a multidimensional aerosol transport model. This model incorporates various mechanisms influencing droplet growth. Parametric studies are conducted to investigate the influen...}, number={26}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Franklin, RK and Edwards, JR and Chernyak, Y and Gould, RD and Henon, F and Carbonell, RG}, year={2001}, month={Dec}, pages={6127–6139} }
@article{benedict_gould_1999, title={Understanding biases in the near-field region of LDA two-point correlation measurements}, volume={26}, ISSN={["0723-4864"]}, DOI={10.1007/s003480050301}, number={5}, journal={EXPERIMENTS IN FLUIDS}, author={Benedict, LH and Gould, RD}, year={1999}, month={Apr}, pages={381–388} }
@article{benedict_gould_1998, title={Concerning time and length scale estimates made from burst-mode LDA autocorrelation measurements}, volume={24}, ISSN={["0723-4864"]}, DOI={10.1007/s003480050171}, number={3}, journal={EXPERIMENTS IN FLUIDS}, author={Benedict, LH and Gould, RD}, year={1998}, month={Mar}, pages={246–253} }
@article{benedict_gould_1998, title={Enhanced power spectrum estimates using Kalman reconstruction}, volume={120}, ISSN={["0098-2202"]}, DOI={10.1115/1.2820641}, abstractNote={A number of power spectral density (PSD) estimators were assessed using real laser Doppler anemometer (LDA) data from grid generated turbulence. PSD estimates from the raw data via the slotting technique and direct transform method were compared to those estimated from sample and hold, linear, and Kalman reconstructed velocity time histories. Of the reconstruction schemes, only Kalman reconstruction was shown to significantly reduce the effects of noise on the measurements leading to an additional 2 decades in power of high frequency information.}, number={2}, journal={JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME}, author={Benedict, LH and Gould, RD}, year={1998}, month={Jun}, pages={253–256} }
@article{raffoul_nejad_gould_spring_1997, title={An experimental and numerical study of the isothermal flowfield behind a bluff body flameholder}, volume={119}, ISSN={["0742-4795"]}, DOI={10.1115/1.2815579}, abstractNote={An experimental and numerical investigation was conducted to study the turbulent velocities and stresses behind a two-dimensional bluff body. Simultaneous three-component laser-Doppler velocimeter (LDV) measurements were made in the isothermal incompressible turbulent flowfield downstream of a bluff body placed at midstream in a rectangular test section. Mean velocities and Reynolds stresses were measured at various axial positions. Spanwise velocity measurements indicated that the flow is three dimensional in the recirculation zone of the bluff body. Confidence in the accuracy of the data was gained by calculating the mass fluxes at each axial station. These were found to agree with each other to within ±3 percent. A parallel Computational Fluid Dynamics (CFD) study was initiated to gage the predictive accuracy of currently available CFD techniques. Three solutions were computed: a two-dimensional steady-state solution using the standard k-ε model, a two-dimensional time-accurate solution using the standard k-ε model, and a two-dimensional time-accurate solution using a Renormalized-Group (RNG) k-ε turbulence model. The steady-state solution matched poorly with the data, severely underpredicting the Reynolds stresses in the recirculation zone. The time-accurate solutions captured the unsteady vortex shedding from the base of the bluff body, providing a source for the higher Reynolds stresses. The RNG k-ε solution provided the best match to the data.}, number={2}, journal={JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME}, author={Raffoul, CN and Nejad, AS and Gould, RD and Spring, SA}, year={1997}, month={Apr}, pages={328–339} }
@inproceedings{yang_gould_horie_iyer_1997, title={New evidence concerning the shock-induced chemical reaction mechanism in a Ni/Al mixture}, volume={429}, booktitle={Shock compression of condensed matter--1997: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter held at Amherst, Massachusetts, July 27-August 1, 1997}, author={Yang, Y. and Gould, R. D. and Horie, Y. and Iyer, K. R.}, year={1997}, pages={639–642} }
@article{yang_gould_horie_iyer_1997, title={Shock-induced chemical reactions in a Ni/Al powder mixture}, volume={70}, ISSN={["1077-3118"]}, DOI={10.1063/1.119172}, abstractNote={A new 50 mm powder gun was used to reproduce and to extend the real-time observations of ultra-fast exothermic reactions in a Ni/Al powder mixture at the shock front. Shock profiles measured by a manganin gauge show that (1) the threshold pressure for reaction is about 14 GPa; (2) the initiation criteria based either on shock energy or melting are in contradiction with experimental evidence.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Yang, Y and Gould, RD and Horie, Y and Iyer, KR}, year={1997}, month={Jun}, pages={3365–3367} }