Showing papers by "Jung-Yeul Jung published in 2003"

Fluid Flow and Heat Transfer in Microchannels With Rectangular Cross Section

Abstract: Forced convective heat transfer coefficients and friction factors for flow of water in microchannels with a rectangular cross section were measured. An integrated microsystem consisting of five microchannels on one side and a localized heater and seven polysilicon temperature sensors along the selected channels on the other side was fabricated using a double-polished-prime silicon wafer. For the microchannels tested, the friction factor constant \( \user2{C} = \user2{f}Re_{{D_{h} }} \) obtained are values between 53.7 and 60.4, which are close to the theoretical value from a correlation for macroscopic dimension, 56.9 for Dh = 100 μm. The heat transfer coefficients obtained by measuring the wall temperature along the micro channels were linearly dependent on the wall temperature, in turn, the heat transfer mechanism is strongly dependent on the fluid properties such as viscosity. The measured Nusselt number in the laminar flow regime tested could be correlated by \( Nu = 0.00058{\text{ }}Re_{{D_{h} }} ^{{1.15}} {\text{ }}Pr^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern- ulldelimiterspace} 3}} {\left( {{{\mu} {\left( \user2{T} \right)}} \mathord{\left/ {\vphantom {{{\mu} {\left(\user2{T} \right)}} {{\mu} {\left( {\user2{T}_{\infty } } \right)}}}} \right. \kern- ulldelimiterspace} {{\mu} {\left( {\user2{T}_{\infty } } \right)}}} \right)}^{{2.76}} {\left( {\user2{W} \mathord{\left/ {\vphantom { \user2{{W H}}}} \right. \kern- ulldelimiterspace} \user2{H}} \right)}^{{0.3}} , \) which is quite different from the constant value obtained in macrochannels.

Exergetic and Thermoeconomic Analysis of Steam Power Plant

Abstract: Exergetic and thermoeconomic analyses were performed fer a 137-MW steam power plant In these analyses, mass and energy conservation laws were applied to each component of the system Quantitative balance of the exergy and exergetic cost for each component, and for the whole system was carefully considered The exergo-economic model, which represented the productive structure of the system was used to visualize the cost formation process and the productive interaction between components The computer program developed in this study can determine production costs of power plants, such as gas-and steam-turbines plants and gas-turbine cogeneration plants The program can also be used to study plant characteristics, namely, thermodynamic performance and sensitivity to changes in process and/or component design variables