Jinhee Jeong

• Doctor of Philosophy
• Consultant at LG Electronics

From the perspective of commercializing rotating machines equipped with magnetic bearings, maintaining the error between the mechanical center and the magnetic center within an acceptable level is crucial. The existing method of measuring the center error is to adjust the position references that minimize the current imbalance present in levitation...

In this study, we perform a series of aero-thermo-mechanical analyses to predict the running-tip clearance and the effects of impeller deformation on the performance using a centrifugal compressor. During operation, the impeller deformation due to a combination of the centrifugal force, aerodynamic pressure and the thermal load results in a non-uni...

Since vibrations in rotating machinery is a direct cause of performance degradation and failures, it is very important to predict the level of vibrations as well as have a method to lower the vibrations to an acceptable level. However, the changes in balancing during installation and the vibrational modes of the support structure are difficult to p...

Gas foil thrust bearings (GFTBs) have attractive advantages over rolling element bearings and oil film thrust bearings, such as oil-free operation, high speed stability, and high-temperature operation. However, GFTBs have lower load carrying capacity than the other two types of bearings owing to the inherent low gas viscosity. The load carrying cap...

Organic Rankine cycle (ORC) is an useful cycle for power generation system with low temperature heat sources (80{\sim}400^{\circ}C). Since the boiling point of operating fluid is low, the system is used to recover the low temperature heat source of waste heat energy. In this study, a ORC with R134a is applied to recover the waste energy of condense...

A typical turbo heat pump system consists of a centrifugal compressor, expansion valve, and two heat exchangers-a condenser and evaporator. Compared to a gas turbine, a turbo heat pump introduces additional complexities because it is a two-phase closed-loop system with heat exchange using a real gas/liquid (refrigerant) as the working fluid. For th...

A typical turbo heat pump system consists of a centrifugal compressor, expansion valve, and two heat exchangers or plenums — a condenser and evaporator. Compared to a gas turbine, a turbo heat pump introduces additional complexities because it is a two-phase, closed-loop system with heat exchange using a real gas/liquid (refrigerant) as working flu...

The objectives of this study are to visualize the dispersion of nano-particles in binary nanofluids, to find the effect of key parameters such as SiO2 nano-particles concentration on the distribution stability in the H2O/LiBr nanofluids, and to measure the vapor absorption rate and heat transfer rate for falling film flow of binary nanofluids. The...

The objectives of this study are to analyze performance characteristics during partial load operation and to calculate energy consumption amount of H2O/LiBr absorption chiller with a capacity of 210 RT. The effect of cooling water flow rate and cooling water inlet temperature on the absorption performance and energy saving is quantified during the...

Coherent structures (CS) near the wall (i.e. y+ [less-than-or-eq, slant] 60) in a numerically simulated turbulent channel flow are educed using a conditional sampling scheme which extracts the entire extent of dominant vortical structures. Such structures are detected from the instantaneous flow field using our newly developed vortex defi...

Considerable confusion surrounds the longstanding question of what constitutes a vortex, especially in a turbulent flow. This question, frequently misunderstood as academic, has recently acquired particular significance since coherent structures (CS) in turbulent flows are now commonly regarded as vortices. An objective definition of a vortex shoul...

Considerable confusion surrounds the longstanding question of what constitutes a vortex, especially in a turbulent flow. This question, frequently misunderstood as academic, has recently acquired particular significance since coherent structures (CS) in turbulent flows are now commonly regarded as vortices. An objective definition of a vortex shoul...

Coherent structures (CS) are educed using a conditional sampling technique involving alignment of vorticity patches of largest size and strength; hence we educe dominant CS. A numerically simulated spatially evolving wake of a thick flat plate is used as the database, and the inflow condition for the simulated wake includes random velocity perturba...

Activities are summarized for each of the three topics discussed: eduction of coherent structures; measurement of propagation velocities of perturbation in turbulent flows; and direct evaluation of the Taylor hypothesis.