• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.284-287
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• 2004

Micro-structures fabricated by X-ray lithography are largely affected by doses, development conditions and other factors. For these reasons, PMMA development rates and its surface profiles under various development conditions were obseued. Development rates were measured in the rage from 1 to 6 $kJ/cm^3$ using the 9C1 white beamline of Pohang light source(PLS). In this experiment, we observed that development rates of stacked PMMA sheet using Si filter were relatively higher than that of not using Si filter. Furthermore, development rates in condition with the acoustic agitation(1 MHz, 3.67 $W/cm^3$) were twice than that in dipping condition with $35^{\circ}C$ developer considering the PMMA sheets-substrate bond strength

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.655-658
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• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat-flux boundary conditions unlike many of the previous researches, which had adopted constant wall-temperature conditions. Therefore in the study, modified dimensionless numbers such as Stefan and Rayleigh were adopted to represent heat transfer results. The experimental results revealed that ultrasonic vibrations accompanied the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion, accelerating the melting process as much as 2.5 times, compared with the result of natural melting (i. e., the case without ultrasonic vibration). Such effects are believed to be a prime mechanism in the overall melting process when ultrasonic vibrations were applied. Subsequently, energy could be saved by applying the ultrasonic vibrations to the natural melting In addition, various time-wise dimensionless numbers provided a conclusive evidence of the important role of the ultrasonic vibrations on the melting phenomena of the PCM.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1882-1891
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• 2001

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat flux boundary conditions unlike many of the previous researches adopted constant wall temperature conditions. Therefore, in the present study, modified dimensionless parameters such as Ste* and Ra* were used. Also, general relationships between melting with ultrasonic vibrations and melting without ultrasonic vibrations were established during the melting of PCM. Experimental observations show that the effect of ultrasonic vibrations on heat transfer is very important throughout the melting process. The results of the present study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They enhance the melting process as much as 2.5 tildes, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, various time-wise dimensionless numbers provide conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.235-240
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• 2001

This study presents experimental work on phase change heat transfer, in order to increase heat transfer rate, ultrasonic vibrations were introduced. Solid-liquid phase change occurs in a number of situations of practical interest. This study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, this study presented the effective way to enhance phase change heat transfer.