• Journal of the Korean Society of Industry Convergence
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• v.3 no.3
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• pp.265-273
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• 2000

Basic simulation program for Vuilleumier cycle heat pump was developed that can use precise VMHP design and analysis. VMHP system was divided 11 sections in simulation. Simulation was used adiabatic model analysis and that considered with heat transfer performance for heat exchanger, regenerator loss, conduction loss, shuttle loss, pumping loss and pressure loss by flow friction. Specially, friction loss of connection pipe between heat compression side and heat pump side, leakage of rod seal and piston seal was considered in the analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1238-1247
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• 2003

Simplified thermodynamic analysis of high pressure 4-stage reciprocating compressors with 4 inter-coolers has been investigated to predict a behavior of a compressor system for NGV(natural gas vehicles). A computer program has been developed to predict and estimate the performance of high pressure 4-stage reciprocating compressor system. Thermodynamic properties of compressed natural gas(CNG) were calculated by ideal gas theory and compression cycle was assumed as reversible adiabatic compression and expansion processes, and isobaric intake and discharge processes. Comparison between results predicted by calculation model and measured by experimental tests is presented.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.102-107
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• 2000

We propose a new scheme for generating a pedestal-free, femtosecond soliton pulse train by utilizing quasI-adiabatic high order soliton pulse evolution in dispersion decreasing fiber in conjunction with the intermediate pedestal suppression stage. Compression factor over 280 was achieved from lOGHz sinusoidal input, to 176 is soliton pulse train. train.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.351-358
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• 2006

This paper presents analytical results of a rotary vane compressor performance when the compressor is used for air supply from underwater. Compression characteristics such as pressure and temperature in a compression chamber are analyzed. Volumetric and adiabatic efficiencies are calculated. Vane dynamics are also performed to give reaction forces on the vane from the cylinder inner surface and from vane slots. Compressor efficiency is about 34.9%, and about 55% of the compressor loss is produced by the friction between the vane nose and the cylinder wall. Volumetric efficiency is about 79.5%, and indicated efficiency is about 77.1%, which are comparable to other displacement type compressors. When roller was introduced between housing inner wall and vane tips, mechanical efficiency could be improved by as much as 24.9%, depending on the roller friction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.1
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• pp.19-27
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• 2007

Analytical investigation on the performance of a two stage twin rotary compressor for $CO_2$ heat pump water heater system has been carried out. A computer simulation program was made based on analytical models for gas compression in control volumes, leakages among neighboring volumes, and dynamics of moving elements of the compressor. Calculated cooling capacity, compressor input, and COP were well compared to those of experiments over the compressor speeds tested. For the operating condition of suction pressure of 3 MPa, and discharge pressure of 9 MPa, and compressor inlet temperature of $35^{\circ}C$, the compressor efficiency was calculated to be 80.2%: volumetric, adiabatic, and mechanical efficiencies were 88.3%, 93.2%, and 92.7%, respectively. For the present compressor model, volumetric and adiabatic efficiencies of the second stage cylinder were lower by about $6{\sim}7%$ than those of the first stage mainly due to the smaller discharge port at the second stage. Parametric study on the discharge port size showed that the compressor performance could be improved by 3.5% just by increasing the discharge port diameter by 20%.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.121-125
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• 2023

In winter, Jeju's Seogwipo and Jungmun areas are 2~3℃ warmer than Jeju City. The reason is that when the north wind over Halla Mountain crosses Baengnokdam of Halla Mountain and passes the 300m long and 260m vertical rock face of Donnaeko at an altitude of 1600m above sea level, the cold air turns into warm air through adiabatic compression, and the warmth rides on Donnaeko and flies to Seogwipo and Jungmun. Conversely, the south wind that rises over the sea in Seogwipo in the summer passes over Hallasan Mountain and passes 99 valleys before turning into a muggy, humid climate, making Jeju hot. In other words, it is because of The wind from Jeju City to Seogwipo-The Wind from Seogwipo to Jeju City.

• Journal of Biosystems Engineering
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• v.20 no.3
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• pp.205-216
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• 1995

A fast and inexpensive approximate analysis method to predict power output characteristics of the Stilting engines in a preliminary design stage was investigated. In basic equations proposed by Walker, typical temperatures of working fluids in expansion and compression spaces were treated as those of working fluids in heater and cooler respectively. While the temperature of working fluid in the expansion space was actually lower than that of working fluid in the heater, the temperature of working fluid in the compression space was higher than that of working fluids in the cooler. In this paper, the working fluid temperature of expansion space was treated as lower than the heater temperature and that of compression space was treated as higher than the cooler temperature. Also, according to them, the power output characteristics of the Stirling engine were evaluated with respect to the GPU-3 and 4-215 Stilting engines. The following conclusions were drawn from the analysis. 1. Using the available experimental data from the GPU-3 Stirling engine, it was shown that the approximate analysis predicts the brake power with a maximum error of 19 percent at 1, 000rpm and with a minimum error of 3 percent at 2, 000rpm. 2. The approximate analysis data which for the GPU-3 Stirling engine were much closer to the experimental data than those of adiabatic 2nd order and 3rd order analysis within 1, 500rpm to 2, 500rpm. 3. The approximate analysis data which for the GPU-3 and 4-215 Stilting engines were much closer to the experimental data than those of the Beal number analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1356-1364
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• 1990

This paper deals with the preliminary design conditions of Stirling Engines based on an adiabatic analysis with regenerator effectiveness. The investigation of thermal regeneration process results that the definition of effectiveness proposed by Urieli et al. is appropriate for the present model. Then, it is applied to the already existing approximate analytic solution for the adiabatic model in order to optimize thermal efficiency as well as work parameter. Results show that thermal efficiency is less sensitive to the variation in design parameters than work. Phase angle for the maximum work is also the most efficient at high values of the effectiveness. Swept volume ratio should be chosen with care. The optimum value of dead volume ratio is at least less than the maximum efficiency condition. The feasible design range in compression ratio lies between the maximum efficiency condition and the structural limit of Stilring Engines, where the higher its value, the better. Changes in the temperature ratio do not alter the design conditions. Working fluids with the specific heat ratio 1.67 are more efficient that those with 1.4.

• Journal of Hydrogen and New Energy
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• v.12 no.3
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• pp.169-176
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• 2001

The purpose of study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The test engine was named heavy-duty variable compression ratio single cylinder engine (VCSCE). The fuel supply system provides LPG/hydrogen mixtures based on same heating value. Various sensors such as crank shaft position sensor (CPS) and hall sensor supply spark timing data to ignition controller. Displacement of VCSCE is $1858.2cm^3$. VCSCE was runned 1400rpm with compression ratio 8. Spark timing was set MBT without knocking. Relative air-fuel ratio(${\lambda}$) of this work was varied between 0.76 and 1.5. As a result, i) Maximum thermal efficiency occurred at ${\lambda}$ value 1.0. It was shown that thermal efficiency was increased approximately 5% with hydrogen enrichment at same ${\lambda}$ value. ii) Engine-out carbon monoxide (CO) emissions were decreased at a great rate under LPG/hydrogen mixture fuelling. iii) Total hydrocarbon (THC) emission was much exhausted in rich zone, same as CO. But THC was exhausted a little bit more in lean zone. iv) Finally, engine-out oxides of nitrogen (NOx) was increased with ${\lambda}$ value 1.0 zone at a greater rate with hydrogen enrichment due to high adiabatic flame temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.195-198
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• 2003

High temperature deformation and softening behavior of SAF 2507 super duplex stainless steel (SDSS) has been investigated in connection with an FEM analysis of hot forging process. Flow curves at various strain rates and temperatures were determined first from compression tests, and the kinetics of dynamic recrystallization were also formulated through the analysis of load relaxation test results. Applying the dynamic materials and proposed by Prasad et al., it was possible to determine the characteristics of deformation behavior effectively at a given condition of deformation. Constitutive relations and recrystallization kinetics formulated from the test results were then implemented in a commercial FEM code. Flow stress compensation formulated upon the volume fraction of recrystallization and adiabatic heating was found to improve significantly the FEA solutions in predicting the forming load and the distribution of recrystallized volume fraction after forging.