The focus of this dissertation is the numerical analysis of confined aerosol jets used in fiber classification and dustiness measurement. Of relevance to the present work are two devices, namely, the Baron Fiber Classifier (BFC), and the... more
The focus of this dissertation is the numerical analysis of confined aerosol jets used in fiber classification and dustiness measurement. Of relevance to the present work are two devices, namely, the Baron Fiber Classifier (BFC), and the Venturi Dustiness Tester (VDT). The BFC is a device used to length-separate fibers, important for toxicological research. The Flow Combination Section (FCS) of this device consists of an upstream region, where an aerosol of uncharged fibers is introduced in the form of an annular jet, in-between two sheath flows. Length-separation occurs by dielectrophoresis, downstream of the FCS in the Fiber Classification Section (FClS). In its standard operation, BFC processes only small quantities of fibers. In order to increase its throughput, higher aerosol flow rates must be considered. The goal of the present investigation is to understand the interaction of sheath and aerosol flows inside the FCS, and to identify possible limits to increasing aerosol flow rates using Computational Fluid Dynamics (CFD). Simulations involve solution of NavierStokes equations for axisymmetric and 3D models of the FCS for six different flow rates, and a pure aerodynamic treatment of the aerosol jet. The results show that the geometry of the FCS, and the two sheath flows, are successful in preventing the emergence of recirculation in the FCS for aerosol-to-sheath flow inlet velocity ratios below ≈ 50. For larger aerosolto-sheath flow inlet velocity ratios, two recirculation regions are formed, one near the inner cylinder and one near the outer cylinder. The VDT is a novel device for measuring the dustiness of powders, relevant for dust
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Over the past few years, owing to different critical features such as high energy densities, safety, cycle-life etc., Lithium-ion batteries have been used successfully as an energy storage system for automotive applications. In addition,... more
Over the past few years, owing to different critical features such as high energy densities, safety, cycle-life etc., Lithium-ion batteries have been used successfully as an energy storage system for automotive applications. In addition, due to recent increase in interests towards developing EVTOL (Electric Vertical Take-Off and Landing) aircrafts, demand for Li-Ion batteries capable of providing high power discharge and charge along with above mentioned features has increased. Thermal Management System (TMS) is a critical component of a Li-Ion battery system that enables sustained high-power peak performance, improves overall life-cycle, and reduces possibility of thermal runaway during regular vehicle operation. The current article studies two different cooling configurations for thermal management of a commercially available 9 A-h Nickel Manganese Cobalt (NMC) Lithium-ion pouch cell for high C-rate conditions. The two configurations are referred to as the Double-sided cooling and...
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The focus of this dissertation is the numerical analysis of confined aerosol jets used in fiber classification and dustiness measurement. Of relevance to the present work are two devices, namely, the Baron Fiber Classifier (BFC), and the... more
The focus of this dissertation is the numerical analysis of confined aerosol jets used in fiber classification and dustiness measurement. Of relevance to the present work are two devices, namely, the Baron Fiber Classifier (BFC), and the Venturi Dustiness Tester (VDT). The BFC is a device used to length-separate fibers, important for toxicological research. The Flow Combination Section (FCS) of this device consists of an upstream region, where an aerosol of uncharged fibers is introduced in the form of an annular jet, in-between two sheath flows. Length-separation occurs by dielectrophoresis, downstream of the FCS in the Fiber Classification Section (FClS). In its standard operation, BFC processes only small quantities of fibers. In order to increase its throughput, higher aerosol flow rates must be considered. The goal of the present investigation is to understand the interaction of sheath and aerosol flows inside the FCS, and to identify possible limits to increasing aerosol flow ...
Research Interests:
Research Interests:
An effective cooling mechanism is the backbone of a good automotive battery thermal management system (BTMS). In addition to prevention of extreme events such as thermal runaway, an automotive BTMS must be able to efficiently tackle... more
An effective cooling mechanism is the backbone of a good automotive battery thermal management system (BTMS). In addition to prevention of extreme events such as thermal runaway, an automotive BTMS must be able to efficiently tackle aggressive environmental temperatures, and/or discharge and charge conditions during electric vehicle operation. Moreover, electrical performance and cycle life of the battery modules and packs are closely tied to the battery temperatures and thermal gradients, which increase with increase in C-Rates. In order to keep the battery temperatures to be under the operational temperature limit, it is crucial that the selected cooling mechanism provides efficient transport of the heat generated by the battery modules and packs to the cooling media under all discharge and charge conditions. Owing to its efficient thermal performance, liquid cooling is preferred by most electric vehicle manufacturers for battery thermal management. This usually incorporates batte...
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I n this paper, we perform 3D numerical simulations to understand the thermal operation of a high-current-load DC Magnetic Contactor (MC) within a Li-ion battery pack. The main focus is on evaluating the thermal behavior of an... more
I n this paper, we perform 3D numerical simulations to understand the thermal operation of a high-current-load DC Magnetic Contactor (MC) within a Li-ion battery pack. The main focus is on evaluating the thermal behavior of an electronically controlled MC through a parametric study that investigates the effect of the magnitude of electric current with the corresponding Ohmic heat generation of the MC. For the numerical analysis we perform time-accurate, conjugate heat transfer-based 3D CFD simulations on high spatial resolution grids with commercial CFD software STAR-CCM+. The results of the numerical simulations with temperature dependent material properties are validated against experimental temperature measurements at various locations on the outer body of the MC. The spatial distribution of temperature, and current within the MC and its connected components are also computed for various input parameter values to evaluate a range of its operational validity within an automotive Li-ion battery pack.
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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... more
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 he...
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An efficient Thermal Management System (TMS) is crucial for superior performance of an automotive Li-ion Battery Module (BM). Liquid-Cooled TMS, consisting of a coolant flow through a cold plate, offers higher rate of heat transfer... more
An efficient Thermal Management System (TMS) is crucial for superior performance of an automotive Li-ion Battery Module (BM). Liquid-Cooled TMS, consisting of a coolant flow through a cold plate, offers higher rate of heat transfer compared to passive or forced-air cooled TMS, thus allowing cells to charge/discharge at aggressive rates and higher ambient temperatures while maintaining the cell temperatures within an optimal range. In the current study, we investigate the effect of a variety of cold plate channel sizes and configurations on the overall thermal performance of a liquid-cooled BM using three-dimensional, time-accurate CFD simulations with variable heat load from cylindrical 21700 Li-ion cells. Specifically, we consider 8 different cold plate designs by varying the size and the flow path of the coolant channels. For all the cold plate designs, we evaluate the average and maximum cell temperatures, and heat transfer rate at a module discharge rate of 1C. Additionally, the coolant pressure drop across the entire cold plate is also computed, which helps in providing information about the energy efficiency of the TMS.
Research Interests:
I n this paper, we perform 3D numerical simulations to understand the thermal operation of a high-current-load DC Magnetic Contactor (MC) within a Li-ion battery pack. The main focus is on evaluating the thermal behavior of an... more
I n this paper, we perform 3D numerical simulations to understand the thermal operation of a high-current-load DC Magnetic Contactor (MC) within a Li-ion battery pack. The main focus is on evaluating the thermal behavior of an electronically controlled MC through a parametric study that investigates the effect of the magnitude of electric current with the corresponding Ohmic heat generation of the MC. For the numerical analysis we perform time-accurate, conjugate heat transfer-based 3D CFD simulations on high spatial resolution grids with commercial CFD software STAR-CCM+. The results of the numerical simulations with temperature dependent material properties are validated against experimental temperature measurements at various locations on the outer body of the MC. The spatial distribution of temperature, and current within the MC and its connected components are also computed for various input parameter values to evaluate a range of its operational validity within an automotive Li-ion battery pack.
Research Interests:
An effective cooling mechanism is the backbone of a good automotive battery thermal management system (BTMS). In addition to prevention of extreme events such as thermal runaway, an automotive BTMS must be able to efficiently tackle... more
An effective cooling mechanism is the backbone of a good automotive battery thermal management system (BTMS). In addition to prevention of extreme events such as thermal runaway, an automotive BTMS must be able to efficiently tackle aggressive environmental temperatures, and/or discharge and charge conditions during electric vehicle operation. Moreover, electrical performance and cycle life of the battery modules and packs are closely tied to the battery temperatures and thermal gradients, which increase with increase in CRates. In order to keep the battery temperatures to be under the operational temperature limit, it is crucial that the selected cooling mechanism provides efficient transport of the heat generated by the battery modules and packs to the cooling media under all discharge and charge conditions. Owing to its efficient thermal performance, liquid cooling is preferred by most electric vehicle manufacturers for battery thermal management. This usually incorporates battery modules exchanging heat with a flowing coolant via cold plate or cooling channels during operation. The current work aims to investigate different liquid cooling configurations and compare their relative thermal performance during operation of a high energy density Pouch Cell. The four configurations selected for this comparison are (1) Face cooling, (2) Single-Sided cooling, (3) Double-Sided cooling, and (4) a Hybrid cooling configuration. Test setups comprising of a commercially available 9 A-h NMC Pouch cell, cold plates, pump, heat exchanger, refrigeration cooling unit, and thermal sensors are built for the above four cooling configurations. During the tests, the selected cell is discharged at different discharge rates (C-Rates), i.e., 3C, 4C, and 5C. The overall cell temperatures and thermal gradient across the cell are measured using T-type thermocouples for the four cooling configurations. In order to capture the thermal gradient across the Pouch cell accurately, several thermocouples on the face of the cell are installed using a thermal interface material. Results show the superiority of Face cooling configuration in terms of overall thermal performance under all considered test conditions. Lowest cell temperatures and thermal gradients across the cell are observed for the Face cooling configuration, while highest temperatures and thermal gradients are observed for the Single-Sided cooling configuration. Much improved thermal performance is also observed in the case of the Hybrid cooling configuration as compared to the Single and Double-Sided cooling configurations. As implementation of the Face cooling configuration at the battery pack level may result in higher weight and cost of the battery pack, owing to its good thermal performance and straightforward scaling to battery pack level, the proposed hybrid liquid cooling mechanism provides a viable alternative to Face cooling for battery thermal management.
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In this paper, we perform 3D CFD simulations to understand the thermal operation of a High Breaking Capacity (H.B.C.) electric fuse within a Li-ion battery pack. The main focus is on evaluating the thermal behavior of a commercially... more
In this paper, we perform 3D CFD simulations to understand the thermal operation of a High Breaking Capacity (H.B.C.) electric fuse within a Li-ion battery pack. The main focus is on evaluating the thermal behavior of a commercially available H.B.C. fuse containing four notched silver fuse elements through a numerical and experimental study that investigates the effect of the magnitude of electric current. For the numerical analysis we perform time-accurate, conjugate heat transfer-based 3D CFD simulations on high spatial resolution grids with commercial CFD software STAR-CCM+. Specifically, we utilize an electrodynamic potential model to calculate current density and the corresponding Ohmic heat generation of the fuse. The results of the numerical simulations with temperature dependent fuse material properties are validated against the experimental temperature measurements. The spatial distribution of temperature, and current in the fuse and its connected components are also compared for various input current values to evaluate the thermal performance of the fuse under a range of operating conditions.
Research Interests:
An efficient Thermal Management System (TMS) is crucial for superior performance of an automotive Li-ion Battery Module (BM). Liquid-Cooled TMS, consisting of a coolant flow through a cold plate, offers higher rate of heat transfer... more
An efficient Thermal Management System (TMS) is crucial for superior performance of an automotive Li-ion Battery Module (BM). Liquid-Cooled TMS, consisting of a coolant flow through a cold plate, offers higher rate of heat transfer compared to passive or forced-air cooled TMS, thus allowing cells to charge/discharge at aggressive rates and higher ambient temperatures while maintaining the cell temperatures within an optimal range. In the current study, we investigate the effect of a variety of cold plate channel sizes and configurations on the overall thermal performance of a liquid-cooled BM using three-dimensional, time-accurate CFD simulations with variable heat load from cylindrical 21700 Li-ion cells. Specifically, we consider 8 different cold plate designs by varying the size and the flow path of the coolant channels. For all the cold plate designs, we evaluate the average and maximum cell temperatures, and heat transfer rate at a module discharge rate of 1C. Additionally, the coolant pressure drop across the entire cold plate is also computed, which helps in providing information about the energy efficiency of the TMS.
Research Interests:
Dustiness quantifies the propensity of a finely divided solid to be aerosolized by a prescribed mechanical stimulus. Dustiness is relevant wherever powders are mixed, transferred or handled, and is important in the control of hazardous... more
Dustiness quantifies the propensity of a finely divided solid to be aerosolized by a prescribed mechanical stimulus. Dustiness is relevant wherever powders are mixed, transferred or handled, and is important in the control of hazardous exposures and the prevention of dust explosions and product loss. Limited quantities of active pharmaceutical powders available for testing led to the development (at University of North Carolina) of a Venturi-driven dustiness tester. The powder is turbulently injected at high speed (Re ~ 2 × 10(4)) into a glass chamber; the aerosol is then gently sampled (Re ~ 2 × 10(3)) through two filters located at the top of the chamber; the dustiness index is the ratio of sampled to injected mass of powder. Injection is activated by suction at an Extraction Port at the top of the chamber; loss of powder during injection compromises the sampled dustiness. The present work analyzes the flow inside the Venturi Dustiness Tester, using an Unsteady Reynolds-Averaged Navier-Stokes formulation with the k-ω Shear Stress Transport turbulence model. The simulation considers single-phase flow, valid for small particles (Stokes number Stk <1). Results show that ~ 24% of fluid-tracers escape the tester before the Sampling Phase begins. Dispersion of the powder during the Injection Phase results in a uniform aerosol inside the tester, even for inhomogeneous injections, satisfying a necessary condition for the accurate evaluation of dustiness. Simulations are also performed under the conditions of reduced Extraction-Port flow; results confirm the importance of high Extraction-Port flow rate (standard operation) for uniform distribution of fluid tracers. Simulations are also performed under the conditions of delayed powder injection; results show that a uniform aerosol is still achieved provided 0.5 s elapses between powder injection and sampling.
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The Baron fiber classifier is an instrument used to separate fibers by length. The flow combination section (FCS) of this instrument is an upstream annular region, where an aerosol of uncharged fibers is introduced along with two sheath... more
The Baron fiber classifier is an instrument used to separate fibers by length. The flow combination section (FCS) of this instrument is an upstream annular region, where an aerosol of uncharged fibers is introduced along with two sheath flows; length separation occurs by dielectrophoresis downstream in the flow classification section. In its current implementation at NIOSH, the instrument is capable of processing only very small quantities of fibers. In order to prepare large quantities of length-separated fibers for toxicological studies, the throughput of the instrument needs to be increased, and hence, higher aerosol flow rates need to be considered. However, higher aerosol flow rates may give rise to flow separation or vortex formation in the FCS, arising from the sudden expansion of the aerosol at the inlet nozzle. The goal of the present investigation is to understand the interaction of the sheath and aerosol flows inside the FCS, using computational fluid dynamics (CFD), and ...