Satbyoul Jung

An Experimental Study on Heat Transfer Mechanisms in the Microlayer using Integrated Total Reflection, Laser Interferometry and Infrared Thermometry Technique

On a visible-transparent boiling surface, the detailed geometry of a microlayer can be detected using a total reflection technique combined with laser interferometry. On an infrared-opaque boiling surface, the surface temperature and heat flux distribution can be obtained using a high-speed infrared thermometry technique. In the present study, an experimental technique to study heat transfer in the microlayer is described that permits the simultaneous use of the total reflection combined with laser interferometry and infrared thermometry. Boiling takes place from an infrared-opaque and visible-transparent indium–tin-oxide thin-film heater deposited on an infrared- and visible-transparent calcium fluoride substrate. Details of microlayer geometry and the associated surface temperature and heat flux distribution are obtained using an integrated experimental technique. Heat transfer mechanisms in the microlayer are quantitatively discussed.

Experimental Study on Heat Flux Partitioning in Subcooled Nucleate Boiling on Vertical Wall

To validate the accuracy of the boiling heat flux partitioning model, an experiment was performed to investigate how the wall heat flux is divided into the three heat transfer modes of evaporation, quenching, and single-phase convection during subcooled nucleate boiling on a vertical wall. For the experimental partitioning of the wall heat flux, the wall heat flux and liquid vapor distributions were simultaneously – obtained using synchronized infrared thermometry and the total reflection technique. Boiling experiments of water with subcooling of 10 °C were conducted under atmospheric pressure, and the results obtained at the wall superheat of 12 °C and average heat flux of 283 kW/m were analyzed. There was a large difference in the heat flux partitioning results between the experiment and correlation, and the bubble departure diameter and bubble influence factor, which account for a portion of the surrounding superheated liquid layer detached by the departure of a bubble, were found to be important fundamental boiling parameters. Corresponding Author, hdkims@khu.ac.kr 2014 The Korean Society of Mechanical Engineers C 송준규 박준석 정샛별 김형대 · · · 466 e 기화 : q 급랭 : c 대류 : d 이탈 직경 : 1f 단상 : 2f 상 : 2

Experimental Study on Geometry of a Microlayer During Single-Bubble Nucleate Boiling

To measure the physical parameters of the simple microlayer model for the prediction of the heat flux and heat transfer rate due to the evaporation of the microlayer during nucleate boiling, the microlayer geometry was experimentally examined. The parameters, including initial thickness, moving velocity and microlayer radius, were measured by total reflection and interferometry techniques using a laser. Single-bubble nucleate boiling experiments were conducted using saturated water on a horizontal surface under atmospheric pressure. The geometric characteristics of the microlayer underneath the bubbles periodically nucleating at a nucleation site at an average heat flux of were analyzed. The experimental results in the present study show that the maximum initial thickness of the microlayer and the horizontal moving velocity are and 0.12 m/s, respectively.