• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.716-724
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• 1999

In co-orbiting scroll compressor, the two scroll members are to orbit with independent radii, producing a relative orbit motion between them. One scroll member is driven by the crank mechanism while the motion of the other member is determined by geometrical constraints and reacting forces. This paper presents an analytical study on the performance of a co-orbiting scroll compressor. The following results have been obtained: Radial contact force between the scroll wraps is virtually free from the centrifugal force of the orbiting scroll member. The frictional losses are somewhat increased due to the complicated drive mechanism, yielding to a little lower EER compared to conventional radially compliant scroll compressors .

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.325-332
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• 2005

This paper addresses the development of a scroll expander for power generation from relatively low temperature steam source. It has a double-sided orbiting scroll member so that no thrust bearing is needed to support the base plate of the orbiting scroll. Three power transmission shafts are placed at the periphery of the orbiting scroll base plate, and these shafts can also function as anti-rotation devices. Final output is obtained from the main central shaft engaged with the three power transmission shafts through gear assembly. The clearance between the fixed and orbiting scroll elements was estimated by comparing measurement of the mass flow rate with calculation results of a computer simulation. Due to large clearance, the expander total and volumetric efficiencies were measured to be $34\%\;and\;43\%$, respectively. It has been shown through the computer simulation that the total and volumetric efficiencies could be improved to $65\%\;and\;83\%$, respectively, if the current clearance is reduced by half.

• Korean Journal of Remote Sensing
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• v.39 no.2
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• pp.169-181
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• 2023

Recently, in order to reduce carbon dioxide (CO₂) emissions, which is the main cause of global warming, Korea has declared carbon emission reduction targets and carbon neutral. Accurate assessment of regional emissions and atmospheric CO₂ concentrations is becoming important as a result. In this study, we identified the spatiotemporal differences between satellite-based atmospheric CO₂ concentration and CO₂ emissions for the Korean Peninsula region using column-averaged CO₂ dry-air mole fraction from the Orbiting Carbon Observatory-2 and emission inventory. And we explained these differences using solar-induced fluorescence (SIF), a photosynthetic reaction index according to vegetation growth. The Greenhouse Gas Inventory and Research Center (GIR) and Emissions Database for Global Atmospheric Research (EDGAR) emissions continued to increase in Korea from 2014 to 2018, but the satellite-based atmospheric CO₂ concentration decreased in 2018, respectively. Regionally, GIR and EDGAR emissions increased in 2018 in Gyeonggi-do and Chungcheongbuk-do, but satellite-based CO₂ concentrations decreased for the corresponding years. In addition, the correlation analysis between emissions and satellite-based CO₂ concentration showed a low correlation of 0.22 (GIR) and 0.16 (EDGAR) in Seoul and Gangwon-do. Atmospheric CO₂ concentrations showed a different correlation with SIF by region. In the CO₂-SIF correlation analysis for the growing season (May to September), Seoul and Gyeonggi-do showed a negative correlation coefficient of -0.26, Chungcheongbuk-do and Gangwon-do showed a positive correlation coefficient of 0.46. Therefore, it can be suggested that consideration of the CO₂ absorption process is necessary for analyzing the relationship between the atmospheric CO₂ concentration and emission inventory.

• Tribology and Lubricants
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• v.19 no.3
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• pp.146-150
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• 2003

The natural refrigerant $CO_2$has attracted as an alternative refrigerant currently used in air conditioning system, which has high global warming potential. In this study, the tribological characteristics of the sliding surfaces between a fixed scroll and an orbiting scroll of the scroll compressor were investigated in $CO_2$/ POE mixed environment. The pin-on-disk type sliding tests were carried out under the various sliding speeds, normal loads. surface roughness, and pressures. During the test, friction forces, wear amount and surface temperature were monitored.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.241-249
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• 2004

A parametric study on the scroll wrap configuration factors of a $CO_2$scroll compressor for heat pump water heater has been carried out. Since there are 7 scroll wrap design parameters and 5 equations relating them, two of the design parameters can be selected as independent parameters. In this study, the wrap thickness and orbiting radius are chosen as independent ones. Computer simulation program has been used to estimate the compressor performance at various combinations of the scroll wrap design parameters. It has been found that there exists optimum combination of the wrap parameters for the highest compressor performance over analyzed ranges of the design parameters.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.397-403
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• 2007

In this paper, conceptual design of scroll expander-compressor for Stirling engine utilizing solar energy as heat source has been carried out. Orbiting scroll member was designed to have a double-sided structure to reduce the overall scroll size and to cancel out the axial forces on the orbiting scroll base plate. Diameter of designed scroll base plate was about 251 mm for the expander, and it was about 218 mm for the compressor. With operating condition such as temperature range of $400^{\circ}C/20^{\circ}C$, pressure range of 6 MPa/2 MPa, and shaft speed of 2700 rpm, the shaft output of the designed scroll expander was calculated to be 49.8 kW, while input power for the scroll compressor was 38.6 kW, yielding 11.2 kW for the output power of the Stirling engine. Overall efficiencies of the scroll expander and compressor were 93.73% and 92.87%, respectively.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.4
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• pp.115-122
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• 2009

Numerical simulations for scroll, two-stage twin rotary, and two-cylinder reciprocating compressors have been carried out to understand the effectiveness of each type compressor for heat pump water heater application using $CO_2$ as refrigerant. For suction pressure of 3.5 MPa and discharge pressure of 9 MPa, clearance volume ratio of the reciprocating compressor needs to be about 5% or less to have the volumetric efficiency comparable to that of the scroll compressor with tip clearance of $5\;{\mu}m$. Volumetric efficiency of the scroll compressor is quite sensitive to tip clearance. Adiabatic efficiency of the twin rotary compressor was calculated to be the lowest among the three types, and the most severe drawback of the $CO_2$ scroll compressor was a significant increase in the mechanical loss at the thrust surface supporting the orbiting scroll member. While the scroll compressor showed very smooth torque load variation, peak-to-peak torque variations of the twin rotary and two-cylinder reciprocating compressors were about 50% and 250%, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1305-1313
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• 2000

In a co-rotating scroll compressor, both scrolls rotate on their fixed axes contrary to the conventional orbiting type scroll machine. This implies fixed locations and directions of the gas pressure force and sealing force. Because the tilting moment is mainly caused by interplay between the resultant force of above forces and bearing reaction force, the variation during one cycle is relatively small. Under real operation, this moment is balanced by the restoring moment created by the reaction between the baseplate and thrust bearing or between the scroll tip and baseplate. If these reactions become too large, greater torque is required due to increased friction in addition to the wear of mating parts. Consequently, appropriate study and minimization of tilting moment is important in the design of scroll machines. In this study, taking into account of the small variation of tilting moment during one cycle, we minimize the moment and thrust bearing reaction force by a properly designed back pressure chamber. As a result, for both the driving and driven scrolls, the tilting moment and the reaction force of thrust bearing can be minimized. And the stability is improved for all cases.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.295-317
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• 1991

The discrepancy between centric relation and centric occlusion have a great role on the successful prosthodontic and occlusal treatment. This study was performed to investigate the effect of the discrepancy between centric relation and centric occlusion on condylar guidance inclination and Bennett shift (immediate and progressive side shift). Sixteen adults who have physiologically normal occlusion and are free of TMJ dysfunction were selected. The amount of the sagittal CR-CO discrepancy in lower anterior incisor was obtained by Saphon Visi-Trainer. The amount of the CR-CO discrepancy in condylar level was measured on the individualized corrected tomography. Pantronic survey was performed by using a arbitrary hinge axis according to manufacturer's direction. All subjects were divided into two groups, group I (small) and group II (large), according to the amount of CR-CO discrepancy. At first the amount of the CR-CO discrepancy in condylar level between two groups was compared and then the condylar guidance inclination and Bennett shift between two groups were compared and analyzed. The results were as follows; 1. The average CR-CO discrepancy in lower anterior incisors was 0.7mm superoinferiorly, 0.49mm anteroposteriorly, and 0.88 mm in total. The average CR-CO discrepancy in condylar level was 0.43mm. 2. The CR-CO discrepancy measured on teeth level and condylar level were highly correlated (p<0.01). 3. The correlation of the condylar position in the glenoid fossa between two groups was not statistically significant. 4. The large CR-CO discrepancy group showed greater amount of Bennett shift and condylar guidance inclination, but there is no statistical significancy. 5. It seems that the CR-CO discrepancy have greater effect on progressive side shift than other elements of mandibular movements.

• Korean Journal of Remote Sensing
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• v.39 no.2
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• pp.129-142
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• 2023

This study analyzed the ratio of carbon monoxide (CO) and carbon dioxide (CO₂), CO and nitrogen dioxide (NO₂) for cities and regionsin Korea and China using column-averaged carbon dioxide dry-air mole fraction (XCO₂) of the Orbiting Carbon Observatory-2/3, CO and NO₂ vertical column density (named XCO, XNO₂ in thisstudy) of TROPOspheric monitoring instrument from April 2018 to April 2022, and presented the relationship between socioeconomic indicators (population, number of vehicles, Gross Regional Domestic Product) and ratio, and differences in characteristics between Korea and China. First, CO₂ and CO were analyzed after calculating ΔXCO₂ and ΔXCO removing the background value and trend line due to the difference in atmospheric residence time of three gaseous substances (CO₂, CO, and NO₂). Comparing the three values by regions, ΔXCO and ΔXCO₂ were relatively higher in China and XNO₂ were higher in Korea and the ratio of both values (ΔXCO/ΔXCO₂, ΔXCO/XNO₂) was higher in China than in Korea. ΔXCO/ΔXCO₂, ΔXCO/XNO₂ and socioeconomic indicators have a positive correlation suggesting that the concentration of air pollutants and greenhouse gases is higher as the city is large and the economic activity is active. Regarding the differences in the ratio characteristics of Korea and China, the relationship between ΔXCO and ΔXCO₂ showed a negative correlation in Korea and a positive correlation in China. When the relationship between ΔXCO and XNO₂ was examined for summer and winter, the change of ΔXCO by season was not significant in Korea, whereasthe change of ΔXCO and XNO₂ by season waslarge in China resulting in the relationship between two countries appeared differently. These results suggest that seasonal variability and national emission characteristics should be considered in the process of analyzing the ratio of greenhouse gases to air pollutants.