Duckjong Kim

Compact Modeling of Fluid Flow and Heat Transfer in Straight Fin Heat Sinks

This work was supported by KISTEP ~Korea Institute of Science & Technology Evaluation and Planning! under grant number 2-578 through the National Research Lab Program.

Thermal interaction at the interface between a porous medium and an impermeable wall

The present work investigates a heat transfer phenomenon at the interface between a porous medium and an impermeable wall subject to a constant heat flux at the bottom. Currently, two possible thermal boundary conditions (which are called the First Approach and the Second Approach) at the interface are used interchangeably for the thermal analysis of convection in a channel filled with a porous medium. The focus of this paper is to determine which of these thermal boundary conditions is more appropriate in accurately predicting the heat transfer characteristics in a porous channel. To this end, we numerically examine the heat transfer at the interface between a microchannel heat sink (an ideally organized porous medium) and a finite-thickness substrate. From the examination, it is clarified that the heat flux distribution at the interface is not uniform for an impermeable wall with finite thickness. This means that a non-uniform distribution of the heat flux (First Approach) is physically reasonable. When the First Approach is applied to the thermal boundary condition, an additional boundary condition based on the local thermal equilibrium assumption at the interface is used

An electrokinetic pressure sensor

A new concept for a micro pressure sensor is demonstrated. The pressure difference between the inlet and the outlet of glass nanochannels is obtained by measuring the electrokinetically generated electric potential. To demonstrate the proposed concept, experimental investigations are performed for 100 nm wide nanochannels with sodium chloride solutions having various concentrations. The proposed pressure sensor is able to measure the pressure difference within a 10% deviation from linearity. The sensitivity of the electrokinetic pressure sensor with 10?5 M sodium chloride solution is 18.5 ?V Pa?1, which is one order of magnitude higher than that of typical diaphragm-based pressure sensors. A numerical model is presented for investigating the effects of the concentration and the channel width on the sensitivity of the electrokinetic pressure sensor. Numerical results show that the sensitivity increases as the concentration decreases and the channel width increases.

Pressure Sensor Using Electrokinetic Energy Conversion Phenomena

In this paper, a new electrokinetic pressure sensor is developed. Test results show that the proposed sensor has good linearity and high sensitivity. Moreover, numerical results show that the sensitivity can be improved 10 times more which is 100 times as high as that of the diaphragm-based pressure sensors.