• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.216-221
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• 2005

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a helically coiled tube were investigated experimentally. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section is a double pipe type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. It was made of a copper tube with the inner diameter of 4.85 [mm], the outer diameter of 6.35 [mm] and length of 10000 [mm]. The refrigerant mass fluxes were 200${\sim}$600 [kg/$m^2$s] and the average pressure varied from 7.5 [MPa] to 10.0 [MPa]. The main results were summarized as follows: The heat transfer coefficient of supercritical $CO_2$ increases, as the cooling pressure of gas cooler decreases. And the heat transfer coefficient increases with the increase of the refrigerant mass flux. The pressure drop decreases in increase of the gas cooler pressure and increases with increase the refrigerant mass flux.

• Journal of the Korea Safety Management & Science
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• v.17 no.4
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• pp.397-401
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• 2015

In this study, analysed the characteristics of power drop and surface damage in solar cell through high temperature and humidity test in the 3 case of EVA(ethylene vinyl acetate) and 2 case ribbon thickness. The solar cells were tested during the 500hr in $85^{\circ}C$ temperature and 85% relative humidity conditions, that excerpted standard of PV Module(KS C IEC-61215). Through the EL(Electroluminescence) shots, specimen's surface have partialy damaged. Before and after high humidity and high temperature test, ribbon thickness $200{\mu}m$ EVA1 case power drop rate was 8.463%, EVA2 case was 6.667%, EVA3 case was 6.373%. In the ribbon thickness $250{\mu}m$ EVA1 case power drop rate was 6.521%, EVA2 case was 8.517%, EVA3 case was 6.019%. EVA3 case was the lowest power and FF(fill factor) drop rate at the 2 case of ribbon thickness, because EVA3 is laerger than EVA1 and EVA2 in thickness, elongation and tensile strength.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1245-1252
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• 2001

The condensation pressure drop for pure refrigerants R-22, R-134a, and a binary refrigerant mixture R-410A flowing in a small diameter tube was investigated. The test section is a counterflow heat exchanger with refrigerant flowing in the inner tube and coolant flowing in the annulus. The test section consists of 1220 [mm] length with horizontal copper tube of 3.38 [mm] outer diameter and 1.77 [mm] inner diameter. The refrigerant mass fluxes ranged from 450 to 1050 [kg/(㎡$.$s)] and the average inlet and outlet qualities were 0.05 and 0.95, respectively. The main experimental results were summarized as follows : In the case of single-phase flow, the pressure drop of R-134a is much higher than that of R-22 and R-410A for the same Reynolds number. The friction factors for small diameter tubes are higher than those predicted by Blasius equation. In the case of two-phase flow, the pressure drop increases with increasing mass flux and decreasing quality. The pressure drop of R-134a is much higher than that of R-22 and R-410A for the same mass flux. Most of correlations proposed in the large diameter tube showed enormous deviations with experimental data. However, the correlation predicted by Honda et al showed relatively good agreement with experimental data for R-134.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.8-14
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• 2019

A drop structure, one of the representative river-crossing structures, is constructed to stabilize a riverbed. On the other hand, the structure interrupts the continuity of the river and causes the destruction of the hydro-ecological environment. Therefore, laboratory experiments of a natural type of drop structure with low differences were performed, and the empirical formula of a local scour hole is proposed. Four experimental flow rates were tested for various types of the drop structure models with 28 test cases. Based on the scour test, it was confirmed that the maximum scour depth occurs rather than the result of applying the previously proposed scour depth formulae. Correlation analysis of the major factors of scour hole at the downstream of the drop structure revealed a strong correlation between the upstream flow characteristics, drop structure height, and total crossing length of the drop model. In addition, the depth and length estimation formula of the maximum scour hole were proposed using the dimensionless variables and validated. In the future, it is also expected that more accurate scour prediction and calculation can be derived by conducting experimental studies and numerical analysis considering the various bed materials and flow conditions.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.77-86
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• 2008

The reliability of leaded and lead-free solders of BGA type packages on a printed circuit board was investigated by employing the standard drop test and 4-point bending test. Tested solder joints were examined by optical microscopy to identify associated failure mode. Three-dimensional finite element analysis(FEM) with ANSYS Workbench v.11 was carried out to understand the mechanical behavior of solder joints under the influence of bending or drop impact. The results of numerical analysis are in good agreement with those obtained by experiments. Packages in the center of the PCB experienced higher stress than those in the perimeter of the PCB. The solder joints located in the outermost comer of the package suffered from higher stress than those located in center region. In both drop and bending impact tests, the lead-free solder showed better performances than the leaded solders. The numerical analysis results indicated that stress and strain behavior of solder joint were dependent on various effective parameters.

• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.12-17
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• 1999

In this study, a drop-weight impact tester was manufactured to assess the strength of CFRP laminate plates. The tests were conducted on several laminates of different ply orientation. A system for the impact strength of CFRP laminates was made considering stress wave propagation theory using drop-weight impact tester as one of impact test. Results indicate that absorbed energy of quasi-isotropic specimen, haying four interfaces is higher than that of orthotropic laminates with two interfaces. Absorbed energy in the specimen that ply number, interface number and fiber stacking sequences is same but having hybrid is higher than that of orthotropic laminates without hybrid.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.4
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• pp.489-496
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• 2011

Purpose : The purpose of this study was to identify the effect of an arch support taping on navicular drop height and plantar pressure in the subjects with excessive pronated foot for 6 weeks. Methods : The fifteen subjects with the pronated foot group and the fifteen subjects with the normal foot group volunteered for this study. Both groups were applied arch support taping at 3 times a week during 6 weeks. Subjects were assessed navicular drop test to evaluate pronation of subtalar joint and plantar pressure on treadmill for pressure measuring system during walking with a bare foot state at pre- taping, after 3 weeks, and after 6 weeks. A two-way repeated analysis of variance design was used to examine the difference of navicular drop height and plantar pressure in the pronation foot group and the normal foot group. Results : The pronated foot group had significantly decreased both the navicular drop height and the plantar pressure under the medial midfoot than the normal foot group after 6 weeks(p<.01). Conclusions : This study proposed that an arch support taping can be support to lift navicular bone as well as to transfer the foot pressure from medial midfoot to lateral midfoot in individuals with excessive pronated foot.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.87-94
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• 2003

To reduce the air side pressure drop in air-cooled heat exchanger, tow-in type winglet vortex generators are applied. A specially designed multiple-channel test core was used in the experiments for the various geometry of winglet vortex generators. The proposed tow-in type vortex generator gives significant separation delay, reduces form drag, and removes the zone of poor heat transfer from near-wake of the tubes. The results show the significant pressure drop reduction for the tow-in win91e1 vortex generators with the similar enhancement of the heat transfer as other vortex generator applications in heat exchanger. In the range of Reynolds number of 350 to 2100 the pressure drop decrease 8∼15% and 34∼55% for the in-line and staggered tube banks, respectively, compared to those without vortex generators.

• Current Photovoltaic Research
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• v.6 no.3
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• pp.69-73
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• 2018

PV system is consisted with PV module, inverter and BOS(balance of system). To have robustic operation more than 20 years, the expected and guaranteed durability and reliability of products should be met. Almost components of PV system are qualified through IEC standards at test laboratory. But the qualification certificate of product does not ensure long-term nondefective operation. PV module's expected life time is nowadays more than 20 years and annual maximum power degradation ratio would be less than -1%. But the power degradation ratio is basically based on real data more than several years' record. Developing test method for ensuring annual maximum power degradation ratio is very need because there are many new products every month with new materials. In this paper, we have suggested new test method under continuous artificial light irradiation test condition for analyze expected maximum power drop ratio.

• Journal of Pharmacopuncture
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• v.11 no.3
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• pp.105-111
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• 2008

Objective: The aim of this study is to investigate the safety of Fel Ursi, Bovis Calculus & Moschus pharmacopuncture solution manufactured with freezing dryness method to use eye drop. Methods: The eye irritation test of this material was performed according to the Regulation of Korea Food & Drug Administration(2005. 10. 21, KFDA 2005-60). After Fel Ursi, Bovis Calculus & Moschus pharmacopuncture solution was applied eyewash in the left eye of the rabbits, the author observed eye irritation of the cornea, iris, conjunctiva at 1, 2, 3, 4 & 7day. Results: 1. After Fel Ursi, Bovis Calculus & Moschus pharmacopuncture solution was applied eyewash in the left eye of the rabbits, there wasn t physical problem at 9 rabbits. 2. After Fel Ursi, Bovis Calculus & Moschus pharmacopuncture solution was applied eyewash in the left eye of the rabbits, there wasn't eye irritation of the cornea, iris, conjunctiva at 1, 2, 3, 4 & 7day. Conclusions: In this study, it was observed that Fel Ursi, Bovis Calculus & Moschus pharmacopuncture solution didn't induced eye irritation in rabbits.