• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.63-68
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• 2001

An experimental study was carried out to identify the various regimes of natural convective boiling and to determine the Critical Heat Flux(CHF) on a 70mm square surface which is inclined at $180^{\circ}$(upward), $90^{\circ}, \;45^{\circ}$. The heater block made of copper with cartridge heaters is submerged in a water tank with windows for visualization. As the heat flux increases from $100kW/m^2$ to $1.1MW/m^2$, the heat transfer regime migrates from the nucleate boiling to film boiling and results in a rapid heat up of the heater block. An explosive vapor generation on the heated surface, whose size and frequency are characterized by the heat flux, is visualized by using a digital camcorder with $512{\times}512$ pixel size at 30fps.

• 한국태양에너지학회 논문집
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• 제36권2호
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• pp.41-51
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• 2016

A solar air heater was designed for supplementary domestic heating. The absorber plate had a series of protruding notches which had triangular openings on the front surface of the absorber plate to direct partial air flow to the rear surface and to enhance the convective heat transfer to the flowing air. The height of the opening as well as the opening configuration was determined by preceding numerical simulations. The experimental model had an absorber plate of 0.78-m width and 1.0-m length which was coated with black paint. The air temperature increased as much as $18^{\circ}C$ for $90-m^3/h$ flow rate when the absorber plate was inclined by $45^{\circ}$ for a clear-day solar irradiation of about $906W/m^2$. The collector efficiency ranged from 69 to 74%. Considering the simplicity of the structure and low manufacturing cost, the solar air heater might have competence as an auxiliary heating device for domestic use. On-site experimental results are presented with discussion for various solar irradiations and air flow conditions.