• Proceedings of the KSME Conference
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• 2000.04a
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• pp.873-878
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• 2000

Semiconductor packaging technology is changed rapidly according to the trends of the micro miniaturization of multimedia and information equipment. For I/O limitation and fine pitch limitation, DIP and SOP/QFP are replaced by BGA/CSP. This is one of the surface mount technology(SMT). Solder ball is bumped n the die pad and connected onto mounting board. In ball bump formation, vacuum suction type ball alignment process is widely used, However this type has some problems such as ionization, static electricity and difficulty of fifo(first-input first-out) of solder balls. Seesaw type is reducing these problems and has a structural simplicity and economic efficiency. Ball cartridge velocity and ball aligned plate angle are Important variables to improve the ball alignment Process. In this paper, seesaw-type CSP solder ball loader is developed and the optimal velocity and plate angle are proposed.

• Journal of the Korean Society of Visualization
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• v.8 no.4
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• pp.19-25
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• 2010

The flow field measurements were conducted on the planes between impeller blades, and the gap between the impeller and turbine blades under speed ratio of 0.4. The study showed that high velocity regions move from locations near the suction surface of the impeller to the pressure blade, shroud corner as flow progresses from the mid-chord of impeller passage to exit and out into the gap region. Planes 3 through 5 also showed flow reversal occurring in the area near the shell surface and progress far into the impeller passage from the impeller passage exit, near shell surface. This affected the converter efficiency negatively. This study would aid in the construction of higher accuracy CFD models of this complex turbomachinery device.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.421-426
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• 2005

Optimal design of serial connected PZT driven micro compressor was investigated. Modeling equations were derived using energy equation and mass conservation equation. The results show that mass flow rate was increased as number of connected micro compresses is increased. As pressure difference between suction port and discharge port in compressor group is increased, connected compressors have much more mass flow rate than single compressor. Mass flow rate is also increased as driving frequency is increased. And optimal design scale is suggested for highest efficiency or highest mass flow rate.

• Journal of Power System Engineering
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• v.4 no.1
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• pp.33-38
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• 2000

The characteristics of center-driver jet pump which have multi-nozzle were studied in this research. Jet nozzles are connected outside of the bend rather than inserted in the bend in order to transport solid materials or fish without any harm. Jet pumps having one nozzle, two nozzles, four nozzles, and sixteen nozzles were tested in this study. The efficiencies and performances of jet pumps were studied for several nozzles shape, for three different mixing chamber shapes, for two suction area shapes. All the efficiency curves for these cases are presented in this paper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.5
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• pp.382-388
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• 2003

Refrigerant flow rates of the multi-type air-conditioning system can be regulated by electronic expansion valves (EEV). The performance of the multi-type air-conditioning system may be improved by lowering the superheat at the compressor suction side. In this study, a superheat temperature setpoint reset algorithm was developed by using fuzzy logics, and a PI algorithm was applied to control the superheat temperature near setpoints. Experimental results showed energy savings and stable operations at a multi-type air-conditioning system. Therefore, the developed setpoint reset algorithm may be effectively used for the EEV superheat temperature control of the multi-type air-conditioning system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.8
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• pp.756-761
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• 2004

Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the NH$_3$ gas to study the performance characteristics from the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 14.5 bar to 16.0 bar by 0.5 bar and for superheat temperature from $0^{\circ}C$ to 1$0^{\circ}C$ by 1$^{\circ}C$ at each condensing pressure. As a result of experiment, when the superheat temperature is 1$^{\circ}C$ at each condensing pressure, the refrigeration system has the highest performance.

• Journal of computational fluids engineering
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• v.16 no.3
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• pp.82-87
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• 2011

The battery pack, a main component of NEV(Neighborhood Electric Vehicle), needs cooling system when it is charging or discharging to prevent the degradation of the battery charging efficiency. The purpose of this study is to analyse the effects of cooling methods, changing positions of inlet and outlet and changing area ratios of inlet and outlet. It has been observed that in the point of uniform cooling, suction from the exit side is more efficient than blowing from the inlet. And there is a suitable inlet/outlet area ratio in maximizing the mass flow rate. A commercial code, STAR-CCM+(ver. 4.02), was used for the numerical study.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.113-118
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• 2008

For a R134a rotary vane compressor used for car air conditioners, characteristics of gas compression and oil supply have been studied. The compressor model under investigation has the low volume ratio of suction to discharge volumes so that there occur flow reversal from discharge port to compression chamber as the leading vane passes over the discharge port. As a result, the volumetric and adiabatic efficiencies turn out to be relatively low compared to other types of displacement compressors. Oil supply mechanism has been comprehended for mathematical modeling and oil flow rate has been calculated for the individual oil passages. This study on the gas compression and oil supply of a rotary vane compressor can be applied to a future design practice on a similar type of compressor.

• Journal of Aerospace System Engineering
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• v.7 no.4
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• pp.49-54
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• 2013

A turbopump for a 75 ton class liquid rocket engine was tested at full speed for 20 seconds using model fluid. Liquid nitrogen is used for the oxidizer pump, water for the fuel pump, and hot gas for the turbine. The non-cavitating head of pump from the turbopump assembly test showed a good agreement with that from the pump component test. The relative difference of turbine efficiency between the turbopump assembly test and the turbine component test was 0.3% only. Suction performance from the turbopump assembly test was higher than that of pump component test, which resulted from the thermodynamic effect of cavitation.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.236-243
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• 2016

This paper presents a simple thermo-physical model of reciprocating compressors for household refrigerator-freezers. The compressor model has been developed based on thermodynamic principles and large data sets from the compressor calorimeter tests. The input data are compressor geometry (displacement and clearance volume), compressor speed, suction pressure and temperature, discharge pressure, and ambient temperature. The model can estimate mass flow rate and compressor power consumption within 3.0% accuracy, which is not much larger than measurement errors associated with calorimeter testing under ideal conditions.