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5 results on '"Wilkie Choi"'

1. Modeling a divertor with mid-leg pumping for high-power H-mode scenarios in DIII-D considering E × B drift flows

Author

Andreas Holm, Robert S. Wilcox, Jonathan H. Yu, Thomas D. Rognlien, Marvin E. Rensink, Filippo Scotti, Roberto Maurizio, Steve L. Allen, Wilkie Choi, Anothony W. Leonard, Morgan W. Shafer, Mathias Groth, and Adam McLean

Subjects
DIII-D, UEDGE, Mid-leg pumping, Plasma drifts, Nuclear engineering. Atomic power, TK9001-9401
Abstract

Edge-plasma simulations of a baffled, long-legged divertor in DIII-D, performed using the multi-fluid code UEDGE, indicate that the position of the detachment front is constrained to the location of the pump duct along the low-field side (LFS) baffle. Simulations including magnetic and E×B drifts were performed for 12.5 MW deuterium plasmas including intrinsic carbon and seeded neon to assess the optimal location of the LFS divertor pump to create a stable detachment front between the target and the X-point. The radiation front position in the simulations, taken to be indicative of the detachment front, can be controlled between the pump and X-point in the favorable magnetic field direction for H-mode access by moving the pump duct location upstream of the target along the LFS baffle. In the unfavorable magnetic field direction, the radial Eθ×B drift flows are directed towards the pumping surface, efficiently removing the injected deuterium gas and limiting the sensitivity of the radiation front location to the gas injection rate. The role of pumping rate and drift direction on the pumping efficiency are also found to affect the divertor plasma conditions and detachment front location in UEDGE simulations.

Published
2024
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2. Validating the Multi-Mode Model’s Ability to Reproduce Diverse Tokamak Scenarios

Author

Tariq Rafiq, Zibo Wang, Shira Morosohk, Eugenio Schuster, Jan Weiland, Wilkie Choi, and Hyun-Tae Kim

Subjects
EAST, KSTAR, JET, MMM, anomalous transport, fusion, Physics, QC1-999, Plasma physics. Ionized gases, QC717.6-718.8
Abstract

A large-scale validation exercise was conducted to assess the multi-mode model (MMM) anomalous transport model in the integrated modeling code TRANSP. The validation included 6 EAST discharges, 17 KSTAR discharges, 72 JET ITER-like wall D-D discharges, and 4 DIII-D fusion plasma discharges. Using the MMM, the study computed anomalous thermal, particle, impurity, and momentum transport within TRANSP. Simulations for EAST, KSTAR, and JET focused on electron and ion temperatures and safety factor profiles, while DIII-D simulations also considered electron density, toroidal rotation frequency, and flow shear. The predicted profiles were compared to experimental data at the diagnostic time, quantifying the comparison using root-mean-square (RMS) deviation and relative offsets. The study found an average RMS deviation of 9.3% for predicted electron temperature and 10.5% for ion temperature, falling within the experimental measurement error range 20%. The MMM model demonstrated computational efficiency and the ability to accurately reproduce a wide range of discharges, including various scenarios and plasma parameters, such as plasma density, gyroradius, collisionality, beta, safety factor and heating method variations.

Published
2023
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4. Modeling of an Indirect Solar Assisted Heat Pump System for a High Performance Residential House

Author

Wilkie Choi, Cynthia Ann Cruickshank, Stephen J. Harrison, and Jenny Chu

Subjects
Engineering, Renewable Energy, Sustainability and the Environment, business.industry, Hybrid heat, Energy Engineering and Power Technology, Mechanical engineering, Coefficient of performance, Thermal energy storage, law.invention, Solar air conditioning, law, Waste heat, Air source heat pumps, Thermosiphon, Process engineering, business, Heat pump
Abstract

Heat pumps are commonly used for residential spaceheating and cooling. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario's efforts to develop a high performance house for the 2013 DOE Solar Decathlon Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system is designed to provide domestic hot water, space-heating, space-cooling and dehumidification. The system included a cold and a hot thermal storage tank and a heat pump to move energy from the low temperature reservoir, to the hot. The solar thermal collectors supplies heat to the cold storage and operate at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature for domestic use via the heat pump. The IMS and the building's energy loads were modeled using the TRNSYS simulation software. A parametric study was conducted to optimize the control, sizing and configuration of the system. This paper provides an overview of the model and summarizes the results of the study. The simulation results suggested that the investigated system can achieve a free energy ratio of about 0.583 for a high performance house designed for the Ottawa climate. Copyright

Published
2014
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5. Modelling of an Indirect Solar-Assisted Heat Pump System for a High Performance Residential House

Author

Stephen J. Harrison, Cynthia Ann Cruickshank, Wilkie Choi, and Jenny Chu

Subjects
Solar Decathlon, business.industry, Nuclear engineering, Cold storage, TRNSYS, Thermal energy storage, Solar energy, law.invention, law, Thermal, Working fluid, Environmental science, business, Heat pump
Abstract

Heat pumps are commonly used for residential space-heating and cooling. The combination of solar thermal and heat pump systems as a single solar-assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario’s efforts to develop a high performance house for the 2013 DOE Solar Decathlon Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system is designed to provide domestic hot water, space-heating, space-cooling and dehumidification. The system included a cold and a hot thermal storage tank and a heat pump to move energy from the low temperature reservoir, to the hot. The solar thermal collectors supplies heat to the cold storage and operate at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature for domestic use via the heat pump. The IMS and the building’s energy loads were modeled using the TRNSYS simulation software. A parametric study was conducted to optimize the control, sizing and configuration of the system. This paper provides an overview of the model and summarizes the results of the study. The simulation results suggested that the investigated system can achieve a free energy ratio of about 0.583 for a high performance house designed for the Ottawa climate.Copyright © 2013 by ASME

Published
2013
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