Kuo-Hsiang Chien - Academia.edu (original) (raw)

Papers by Kuo-Hsiang Chien

Journal of Electronic Packaging, Feb 11, 2009

This study presents an approximation for determining an optimized thickness of a concentric heate... more This study presents an approximation for determining an optimized thickness of a concentric heated rectangular plate and derives an analytical solution for spreading resistance of a spreader having orthotropic conductivities. The solution for the orthotropic plate is obtained by separation of variables, and the optimized thickness is determined by taking the derivative of the thermal resistance with respect to the spreader thickness. According to the calculated results, an enhanced in-plane spreading effect can reduce the spreading resistance. The spreading resistance dominates the overall resistance of thin plates, whereas the one-dimensional conduction resistance becomes important for thick plates. However, the predicted optimized thickness from the approximation shows a disparity from the analytical results, while the aspect ratio between a spreader and heat source is less than 0.2. Even so, the thermal resistance corresponding to the predicted thickness is still in good agreement with the analytical solution. The proposed approximation will be useful for practical thermal design of heat sinks by predetermining the spreader thickness.

This study presents an approximation for determining an optimized thickness of a concentric heate... more This study presents an approximation for determining an optimized thickness of a concentric heated rectangular plate and derives an analytical solution for spreading resistance of a spreader having orthotropic conductivities. The solution for the orthotropic plate is obtained by separation of variables, and the optimized thickness is determined by taking the derivative of the thermal resistance with respect to the spreader thickness. According to the calculated results, an enhanced in-plane spreading effect can reduce the spreading resistance. The spreading resistance dominates the overall resistance of thin plates, whereas the one-dimensional conduction resistance becomes important for thick plates. However, the predicted optimized thickness from the approximation shows a disparity from the analytical results, while the aspect ratio between a spreader and heat source is less than 0.2. Even so, the thermal resistance corresponding to the predicted thickness is still in good agreement with the analytical solution. The proposed approximation will be useful for practical thermal design of heat sinks by predetermining the spreader thickness.

Flow Measurement and Instrumentation, Jun 1, 1997

Developing a practical, economical and simple on-line void fraction measurement of two-phase flow... more Developing a practical, economical and simple on-line void fraction measurement of two-phase flow is of particular interest in applications, such as two-phase mass flowrate measurement during nuclear reactor LOCA accident. The void fraction of air-water two phase flow was measured by using the side-tube method. This method is based on the assumption that the frictional pressure losses, acceleration pressure loss and minor pressure loss are negligible compared with the gravitational pressure loss. Therefore, the total pressure loss across the test section is assumed to be the gravitational pressure loss only, and it is measured by a differential pressure transducer. Duing to static pressure head, air can be separated from water, and then void fraction is obtained from this collapsed water level in the side-tube. In this study, the test sections were 3.81cm and 5.08cm (ID) vertical acrylic pipe, each test section combined with four different side-tubes to measure void fraction and to investigate dimensional effect, and the system pressure is at 1atm. The superficial air and water velocities (jg, jf) are between 0.01m/s to 0.5m/s respectively, and the void fraction is under 0.6. The root mean square (RMS) values of void fraction from four different side-tubes are 0.557, 0.381, 0.214, 0.372 and 0.305, 0.203, 0.190, 0.121 for 3.81cm and 5.08cm pipe respectively, and the void fraction was also compared with the data obtained from the measured the liquid holdup between two quick-closing valves. These results showed a good agreement with the void fraction by quick-closing valves method, and the suitable side-tube dimension also were determined for void fraction measurement in 3.81cm and 5.08cm pipes.

2014 IEEE Industry Application Society Annual Meeting, 2014

LED lighting is probably the most relevant among the emerging solid-state lighting techniques. Im... more LED lighting is probably the most relevant among the emerging solid-state lighting techniques. Impressive scenarios of a wide range of color quality and luminous efficiency have been obtained, mostly at the condition of constant ambient temperature. In this paper, we unleash the above constraint; all main factors influencing the spectral power distribution (SPD) are discussed, alongside the implementation of a pentachromatic R/G/B/A/CW platform suitable for clinic use. The proposed algorithm enables the multispectral cluster to modulate the color temperature from 2800K to 8000K in ambient temperature with high color quality scale (CQS > 85 points) and the possibly highest luminous efficiency.

Flow Measurement and Instrumentation, 1991

ABSTRACT

Flow Measurement and Instrumentation, 1998

Developing a practical, economical and simple on-line void fraction measurement of two-phase flow... more Developing a practical, economical and simple on-line void fraction measurement of two-phase flow is of particular interest in applications, such as two-phase mass flowrate measurement during nuclear reactor LOCA accident. The void fraction of air-water two phase flow was measured by using the side-tube method. This method is based on the assumption that the frictional pressure losses, acceleration pressure loss and minor pressure loss are negligible compared with the gravitational pressure loss. Therefore, the total pressure loss across the test section is assumed to be the gravitational pressure loss only, and it is measured by a differential pressure transducer. Duing to static pressure head, air can be separated from water, and then void fraction is obtained from this collapsed water level in the side-tube. In this study, the test sections were 3.81cm and 5.08cm (ID) vertical acrylic pipe, each test section combined with four different side-tubes to measure void fraction and to investigate dimensional effect, and the system pressure is at 1atm. The superficial air and water velocities (jg, jf) are between 0.01m/s to 0.5m/s respectively, and the void fraction is under 0.6. The root mean square (RMS) values of void fraction from four different side-tubes are 0.557, 0.381, 0.214, 0.372 and 0.305, 0.203, 0.190, 0.121 for 3.81cm and 5.08cm pipe respectively, and the void fraction was also compared with the data obtained from the measured the liquid holdup between two quick-closing valves. These results showed a good agreement with the void fraction by quick-closing valves method, and the suitable side-tube dimension also were determined for void fraction measurement in 3.81cm and 5.08cm pipes.

The study used the theoretical basis of the transient thermal resistance measurement method to es... more The study used the theoretical basis of the transient thermal resistance measurement method to establish an LED thermal resistance measurement system. The Transient Thermal Resistance Structure Analysis (TTRS Analysis) software designed and developed for this study was used to analyze its internal structure in order to establish the overall thermal resistance structure of the LED. When comparing the results to the theoretical value, it was found that the error values were kept to within 10%, indicating extremely high repeatability of the measurement results.

This research aims to experimentally investigate th e thermal performance of flat-plate closed-lo... more This research aims to experimentally investigate th e thermal performance of flat-plate closed-loop pul sating heat pipes (CLPHPs). Two heat pipes were made of co pper capillary tubes with overall size 122 mm × 57 mm × 5.5 mm, one had 16 parallel square channels wi th cross-section 2 mm × 2 mm, called uniform CLPHP, and the other one, called non-uniform CLPHP, had 8 parallel square channels with cross-section 2 mm × 2 mm and 8 parallel square channels with cross-sectio n 1 mm × 2 mm. The working fluid used on the heat p ipe was distilled water. The results shown that the the rmal resistance decreases with the rise of heating power due to the increased circulating speed. For the inc reased of inclinations among the test CLPHPs, the t hermal resistance decrease with the rise of inclinations b y gravity effect. However, the experimental results of the horizontal orientation are significant different fr om the operation conditions of inclinations. The un iform channel CLPHP shows poor h...

This study examines the two-phase flow pattern change and frictional pressure loss pertaining to ... more This study examines the two-phase flow pattern change and frictional pressure loss pertaining to the sudden flow area expansion from a small diameter tube into small rectangular channels. It is found that a unique flow pattern ''liquid jet-like flow pattern'' occurs at a very low quality region of G ¼ 100 kg=m 2 s in a test section of 3 mm  9 mm. This flow pattern is almost inconceivable for the 3 mm  6 mm test section. The pressure difference usually increases with vapor quality but a setback is encountered provided that the liquid jet flow pattern prevails. A phenomenal observation suggests that a conceivable reduction of the pressure difference is related to the liquid jet-like flow pattern, yet a flat or level-off of the pressure difference is seen when the liquid jet-like flow is less pronounced. By contrast, an appreciable increase of pressure difference is seen when the liquid jet-like flow pattern is completely gone. The measured pressure differences are compared with existing correlations/models, whereas none of them gives satisfactory predictions against the present data. It is found that a slight modification to the empirical constant K of Wadle's correlation may give rise to a fair improvement of the predictive ability.

International Journal of Green Energy

Applied Thermal Engineering, 2016

Heat Transfer, Part A, 2005

ABSTRACT

Proceedings of the 15th International Heat Transfer Conference, 2014

Advanced Materials Research, 2011

Following the trend of energy saving and carbon reduction, many countries have been developing va... more Following the trend of energy saving and carbon reduction, many countries have been developing various energy-saving products to aggressively upgrade or replace electrical products with high energy consumption. Household clothes dryer has become an indispensable home appliance to family life. However, its energy efficiency is low. As tumbler inlet conditions and tumbler efficiency have great effects on clothes dryer performance, this study discuss the clothes drying effect and impact of different tumbler inlet conditions (including air temperature, humidity, and flow rate) on the tumbler efficiency and moisture removal rate (MER) values of the clothes tumbler dryer. The results can provide a reference for clothes dryer system design and performance.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2008

This study numerically investigates the performance of micronozzle/diffuser pump subject to the i... more This study numerically investigates the performance of micronozzle/diffuser pump subject to the influence of frequency, opening angle, geometric dimension, and amplitude. For the effect of geometric dimension, the effect of chamber length is far more important than that of chamber depth because it can provide much more effective pumping volume. It is found that the net flowrate of a micropump increased with pumping frequency and opening angle. However, a level-off phenomenon of the net flowrate versus amplitude is seen at amplitudes nearby 150–200 μm and at an opening angle above 10°. This phenomenon is associated with two factors that compensate with each other. One is the free jet flow from the outlet that overturns and blocks the flow from the inlet. The other is the reduction of the strength of jet flow at a larger amplitude owing to effective increase of cross-sectional area.

Journal of Electronic Packaging, 2007

This study examines the spreading ability of rectangular plates numerically, analytically, and ex... more This study examines the spreading ability of rectangular plates numerically, analytically, and experimentally. The effect of aspect ratio, defined as an equivalent radius of a heater divided by that of a spreader plate, is investigated. The numerical results show a very good agreement with the analytical solutions. From the calculated results, the spreading resistance of the conduction plates with a small aspect ratio is higher than the one-dimensional conduction resistance. Calculated results also show that the spreading ability of a metal plate would be affected slightly by the external convective heat-transfer coefficient when the ratio of the longitudinal heat convection to the lateral heat spreading is less than 0.1. In addition to the numerical analysis, experimental comparisons between copper∕aluminum plates and a vapor chamber having the same thickness have been conducted. The experimental results show that the thermal resistance of the metal plates is independent of input p...

Journal of Electronic Packaging, Feb 11, 2009

This study presents an approximation for determining an optimized thickness of a concentric heate... more This study presents an approximation for determining an optimized thickness of a concentric heated rectangular plate and derives an analytical solution for spreading resistance of a spreader having orthotropic conductivities. The solution for the orthotropic plate is obtained by separation of variables, and the optimized thickness is determined by taking the derivative of the thermal resistance with respect to the spreader thickness. According to the calculated results, an enhanced in-plane spreading effect can reduce the spreading resistance. The spreading resistance dominates the overall resistance of thin plates, whereas the one-dimensional conduction resistance becomes important for thick plates. However, the predicted optimized thickness from the approximation shows a disparity from the analytical results, while the aspect ratio between a spreader and heat source is less than 0.2. Even so, the thermal resistance corresponding to the predicted thickness is still in good agreement with the analytical solution. The proposed approximation will be useful for practical thermal design of heat sinks by predetermining the spreader thickness.

This study presents an approximation for determining an optimized thickness of a concentric heate... more This study presents an approximation for determining an optimized thickness of a concentric heated rectangular plate and derives an analytical solution for spreading resistance of a spreader having orthotropic conductivities. The solution for the orthotropic plate is obtained by separation of variables, and the optimized thickness is determined by taking the derivative of the thermal resistance with respect to the spreader thickness. According to the calculated results, an enhanced in-plane spreading effect can reduce the spreading resistance. The spreading resistance dominates the overall resistance of thin plates, whereas the one-dimensional conduction resistance becomes important for thick plates. However, the predicted optimized thickness from the approximation shows a disparity from the analytical results, while the aspect ratio between a spreader and heat source is less than 0.2. Even so, the thermal resistance corresponding to the predicted thickness is still in good agreement with the analytical solution. The proposed approximation will be useful for practical thermal design of heat sinks by predetermining the spreader thickness.

Flow Measurement and Instrumentation, Jun 1, 1997

Developing a practical, economical and simple on-line void fraction measurement of two-phase flow... more Developing a practical, economical and simple on-line void fraction measurement of two-phase flow is of particular interest in applications, such as two-phase mass flowrate measurement during nuclear reactor LOCA accident. The void fraction of air-water two phase flow was measured by using the side-tube method. This method is based on the assumption that the frictional pressure losses, acceleration pressure loss and minor pressure loss are negligible compared with the gravitational pressure loss. Therefore, the total pressure loss across the test section is assumed to be the gravitational pressure loss only, and it is measured by a differential pressure transducer. Duing to static pressure head, air can be separated from water, and then void fraction is obtained from this collapsed water level in the side-tube. In this study, the test sections were 3.81cm and 5.08cm (ID) vertical acrylic pipe, each test section combined with four different side-tubes to measure void fraction and to investigate dimensional effect, and the system pressure is at 1atm. The superficial air and water velocities (jg, jf) are between 0.01m/s to 0.5m/s respectively, and the void fraction is under 0.6. The root mean square (RMS) values of void fraction from four different side-tubes are 0.557, 0.381, 0.214, 0.372 and 0.305, 0.203, 0.190, 0.121 for 3.81cm and 5.08cm pipe respectively, and the void fraction was also compared with the data obtained from the measured the liquid holdup between two quick-closing valves. These results showed a good agreement with the void fraction by quick-closing valves method, and the suitable side-tube dimension also were determined for void fraction measurement in 3.81cm and 5.08cm pipes.

2014 IEEE Industry Application Society Annual Meeting, 2014

LED lighting is probably the most relevant among the emerging solid-state lighting techniques. Im... more LED lighting is probably the most relevant among the emerging solid-state lighting techniques. Impressive scenarios of a wide range of color quality and luminous efficiency have been obtained, mostly at the condition of constant ambient temperature. In this paper, we unleash the above constraint; all main factors influencing the spectral power distribution (SPD) are discussed, alongside the implementation of a pentachromatic R/G/B/A/CW platform suitable for clinic use. The proposed algorithm enables the multispectral cluster to modulate the color temperature from 2800K to 8000K in ambient temperature with high color quality scale (CQS > 85 points) and the possibly highest luminous efficiency.

Flow Measurement and Instrumentation, 1991

ABSTRACT

Flow Measurement and Instrumentation, 1998

Developing a practical, economical and simple on-line void fraction measurement of two-phase flow... more Developing a practical, economical and simple on-line void fraction measurement of two-phase flow is of particular interest in applications, such as two-phase mass flowrate measurement during nuclear reactor LOCA accident. The void fraction of air-water two phase flow was measured by using the side-tube method. This method is based on the assumption that the frictional pressure losses, acceleration pressure loss and minor pressure loss are negligible compared with the gravitational pressure loss. Therefore, the total pressure loss across the test section is assumed to be the gravitational pressure loss only, and it is measured by a differential pressure transducer. Duing to static pressure head, air can be separated from water, and then void fraction is obtained from this collapsed water level in the side-tube. In this study, the test sections were 3.81cm and 5.08cm (ID) vertical acrylic pipe, each test section combined with four different side-tubes to measure void fraction and to investigate dimensional effect, and the system pressure is at 1atm. The superficial air and water velocities (jg, jf) are between 0.01m/s to 0.5m/s respectively, and the void fraction is under 0.6. The root mean square (RMS) values of void fraction from four different side-tubes are 0.557, 0.381, 0.214, 0.372 and 0.305, 0.203, 0.190, 0.121 for 3.81cm and 5.08cm pipe respectively, and the void fraction was also compared with the data obtained from the measured the liquid holdup between two quick-closing valves. These results showed a good agreement with the void fraction by quick-closing valves method, and the suitable side-tube dimension also were determined for void fraction measurement in 3.81cm and 5.08cm pipes.

The study used the theoretical basis of the transient thermal resistance measurement method to es... more The study used the theoretical basis of the transient thermal resistance measurement method to establish an LED thermal resistance measurement system. The Transient Thermal Resistance Structure Analysis (TTRS Analysis) software designed and developed for this study was used to analyze its internal structure in order to establish the overall thermal resistance structure of the LED. When comparing the results to the theoretical value, it was found that the error values were kept to within 10%, indicating extremely high repeatability of the measurement results.

This research aims to experimentally investigate th e thermal performance of flat-plate closed-lo... more This research aims to experimentally investigate th e thermal performance of flat-plate closed-loop pul sating heat pipes (CLPHPs). Two heat pipes were made of co pper capillary tubes with overall size 122 mm × 57 mm × 5.5 mm, one had 16 parallel square channels wi th cross-section 2 mm × 2 mm, called uniform CLPHP, and the other one, called non-uniform CLPHP, had 8 parallel square channels with cross-section 2 mm × 2 mm and 8 parallel square channels with cross-sectio n 1 mm × 2 mm. The working fluid used on the heat p ipe was distilled water. The results shown that the the rmal resistance decreases with the rise of heating power due to the increased circulating speed. For the inc reased of inclinations among the test CLPHPs, the t hermal resistance decrease with the rise of inclinations b y gravity effect. However, the experimental results of the horizontal orientation are significant different fr om the operation conditions of inclinations. The un iform channel CLPHP shows poor h...

This study examines the two-phase flow pattern change and frictional pressure loss pertaining to ... more This study examines the two-phase flow pattern change and frictional pressure loss pertaining to the sudden flow area expansion from a small diameter tube into small rectangular channels. It is found that a unique flow pattern ''liquid jet-like flow pattern'' occurs at a very low quality region of G ¼ 100 kg=m 2 s in a test section of 3 mm  9 mm. This flow pattern is almost inconceivable for the 3 mm  6 mm test section. The pressure difference usually increases with vapor quality but a setback is encountered provided that the liquid jet flow pattern prevails. A phenomenal observation suggests that a conceivable reduction of the pressure difference is related to the liquid jet-like flow pattern, yet a flat or level-off of the pressure difference is seen when the liquid jet-like flow is less pronounced. By contrast, an appreciable increase of pressure difference is seen when the liquid jet-like flow pattern is completely gone. The measured pressure differences are compared with existing correlations/models, whereas none of them gives satisfactory predictions against the present data. It is found that a slight modification to the empirical constant K of Wadle's correlation may give rise to a fair improvement of the predictive ability.

International Journal of Green Energy

Applied Thermal Engineering, 2016

Heat Transfer, Part A, 2005

ABSTRACT

Proceedings of the 15th International Heat Transfer Conference, 2014

Advanced Materials Research, 2011

Following the trend of energy saving and carbon reduction, many countries have been developing va... more Following the trend of energy saving and carbon reduction, many countries have been developing various energy-saving products to aggressively upgrade or replace electrical products with high energy consumption. Household clothes dryer has become an indispensable home appliance to family life. However, its energy efficiency is low. As tumbler inlet conditions and tumbler efficiency have great effects on clothes dryer performance, this study discuss the clothes drying effect and impact of different tumbler inlet conditions (including air temperature, humidity, and flow rate) on the tumbler efficiency and moisture removal rate (MER) values of the clothes tumbler dryer. The results can provide a reference for clothes dryer system design and performance.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2008

This study numerically investigates the performance of micronozzle/diffuser pump subject to the i... more This study numerically investigates the performance of micronozzle/diffuser pump subject to the influence of frequency, opening angle, geometric dimension, and amplitude. For the effect of geometric dimension, the effect of chamber length is far more important than that of chamber depth because it can provide much more effective pumping volume. It is found that the net flowrate of a micropump increased with pumping frequency and opening angle. However, a level-off phenomenon of the net flowrate versus amplitude is seen at amplitudes nearby 150–200 μm and at an opening angle above 10°. This phenomenon is associated with two factors that compensate with each other. One is the free jet flow from the outlet that overturns and blocks the flow from the inlet. The other is the reduction of the strength of jet flow at a larger amplitude owing to effective increase of cross-sectional area.

Journal of Electronic Packaging, 2007

This study examines the spreading ability of rectangular plates numerically, analytically, and ex... more This study examines the spreading ability of rectangular plates numerically, analytically, and experimentally. The effect of aspect ratio, defined as an equivalent radius of a heater divided by that of a spreader plate, is investigated. The numerical results show a very good agreement with the analytical solutions. From the calculated results, the spreading resistance of the conduction plates with a small aspect ratio is higher than the one-dimensional conduction resistance. Calculated results also show that the spreading ability of a metal plate would be affected slightly by the external convective heat-transfer coefficient when the ratio of the longitudinal heat convection to the lateral heat spreading is less than 0.1. In addition to the numerical analysis, experimental comparisons between copper∕aluminum plates and a vapor chamber having the same thickness have been conducted. The experimental results show that the thermal resistance of the metal plates is independent of input p...