• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.1-9
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• 2004

The general method which changes sub-cooling of refrigerant is to control the expansion valve in the state of mixing with liquid and gas phase. In this study, the performance of vehicle air conditioning system is to control either changing the expansion valve or adding the sub condenser. Therefore, this research finally is tested in case of the fourth test procedure, the second test was suitable for a valve opening area due to adjusting valve slope in comparison with the other test. The other test except for the second test happened to do liquid back due to the excessively liquified refrigerant into the system. In conclusion, the second test was appeared not to be influenced upon liquid back, and it is to expect positive performance by controlling an expansion valve. Therefore, it will be also useful to research for an increase of compressor efficiency Performance improvement of an air conditioner is to reinforce the suction performance of the evaporator and increase the sub-cooling, which make use of the sub-cooling system.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.29-33
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• 2008

As the measures of nuclear power plant utilities and manufacturers to reduce the defects of tube expansion region during manufacturing steam generators, many types of NDEs(Non-Destructive Examinations) are conducted to inspect the expansion region. The expansion region of tube is subject to degrade because of stress concentration induced by tube expansion, sludge pile and high temperature. So the inspections for tube expansion region have been reinforced. Liquid penetrant test, helium leak test, Bobbin profile test and hydraulic test are performed to confirm the integrity of tube expanded by hydraulic expansion method. Liquid penetrant test and helium leak test are used to inspect seal weld region on tubesheet end part. Bobbin Profile test is used to inspect fully the expanded region of steam generator tube. Hydraulic test finally verifies the integrity of seal weld region on tubesheet end part.

• Journal of Environmental Science International
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• v.5 no.1
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• pp.93-102
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• 1996

Hydrodynamic characteristics such as gas holdup, liquid circulation velocity and bed expansion in a hexagonal inverse fluidized bed were investigated using air-water system by changing the ratio ($A_d$/$A_r$) of cross-sectional area between the riser and the downcomer, the liquid level($H_1$/H), and the superficial gas velocity($U_g$). The gas holdup and the liquid circulation velocity were steadily increased with the superficial gas velocity increasing, but at high superficial gas velocity, some of gas bubbles were carried over to a downcomer and circulated through the column. When the superficial gas velocity was high, the $A_d$/$A_r$ ratio in the range of 1 to 2.4 did not affect the liquid circulation velocity, but the maximum bed expansion was obtained at $A_d$/$A_r$ ratio of 1.25. The liquid circulation velocity was expressed as a model equation below with variables of the cross-sectional area ratio($A_d$/$A_r$) between riser to downcomer, the liquid level($H_1$/H), the superficial gas velocity($U_g$), the sparser height[(H-$H_s$)/H], and the draft Plate level($H_b$/H). $U_{ld}$ = 11.62U_g^{0.75}$${(\frac{H_1}{H})}^{10.30}$${(\frac{A_d}{A_r})}^{-0.52}$${(\frac({H-H_s}{H})}^{0.91}$${(\frac{H_b}{H})}^{0.13}$

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.98-103
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• 2015

Liquefied petroleum gas can be charged up to 85% of cylinder volume by enforcement regulations of safety control and business of liquefied petroleum gas act. The charged mass by enforcement regulations is considered by liquid expansion of internal liquefied petroleum gas at $65^{\circ}C$. But the temperature of liquid would not be suspended under $65^{\circ}C$ in a cylinder or portable vessel at certain situation. In the thermodynamics view point, the cylinder can be exposed to high pressure by liquid expansion. Consequently, it can be possible to potential risk such as physical explosion. Hence, this paper will offer a method of estimated internal pressure by liquid expansion at critical state in the closed system. Also, the structural factor which is given rise to volume increasement of cylinder is offered by experiment. This paper is expected as crucial reference for a cylinder design of liquefied petroleum gas.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.1-8
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• 2000

Spray as a liquid atomization technique has wide applications of combustion, painting, chemical, medical and agricultural purpose, and so on. Capillary tubes and expansion valves, as an expansion device of vapor compression type refrigerators, has been used from the early time. But there are some problems in practice, the former can't control refrigerant flowrate exactly and the later most of imported are expensive relatively and has some difficulties to install. Choosing an injector as a new concept of expansion device of refrigerator in this study to improve such troubles of the coming expansion device, the refrigerant spray behavior and refrigeration characteristics are evaluated experimentally. It is verified that the injector with a good function of refrigerant atomization plays a desirable role of refrigerant expansion in the actual refrigeration cycle.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.40-45
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• 2011

The purpose of research is to understand the characteristics of refrigeration system having a liquid-vapor phase separator after expansion device and precooling heat exchanger. After expansion process of typical refrigerant of freezer, R134a, the cold vapor of the expanded refrigerant mixture is separated in the liquid-vapor separator and introduced in the precooling heat exchanger to enable the liquid refrigerant to be subcooled. The analysis results showed that the increasing rate of refrigeration capacity and COP can be 8.6% and 1.4%, each. The cause of these performance improvements is due to the difference of the slope of saturated vapor and saturated liquid lines in Mollier diagram of refrigerant.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2249-2260
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• 1995

An experiment of close contact melting of phase-change medium partially filled in an isothermally heated horizontal cylinder is performed which involves the volume expansion of liquid induced by the solid-liquid density difference. The solid-liquid interface motion and the free surface behavior of liquid were reported photographically. The experimental results show that the curvature of upper solid-liquid interface varied to flat as melting progresses. In addition to the varying interface shape, the melting rate increases with the lower initial height of solid and the free surface height of liquid increases linearly. The experimental results of molten mass fraction were expressed in a function of dimensionless time Fo.Ste$^{3}$4/ and agreed well with the analytical solutions.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.105-110
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• 2013

The gimbal expansion joint for the pipe line of a liquid rocket engine undergoes high pressure and cyclic rotational displacement loadings. In present study, the moment analyses and tests of the internal-type gimbal expansion joint for the engine were performed. The moment components due to spring stiffness, friction and lateral force were obtained using a analytic method and their sums at low and high pressures were compared with the test results. Also, applying a $MoS_2$ dry film lubricant to the pin of a external hinge expansion joint, it is tested that the galling of the pin was removed and the friction coefficient was decreased for low pressures.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.3
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• pp.119-127
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• 2005

Liquid pressure amplifiers have been proposed as an energy saving technology for vapor compression refrigeration systems configured with direct-expansion evaporators. The technology utilizes a refrigerant pump in the high pressure liquid line as a means of maintaining a suitable pressure differential across the expansion valve while lowering condensing pressure to achieve the reduction of compressor energy consumption. Applications have been proposed on systems ranging from small unitary air-conditioning to large supermarket and commercial refrigeration systems. This paper clarifies the role of such a device in a vapor compression refrigeration system. Limitations are presented and discussed. Finally, results of detailed analyses are presented to quantify the energy consumption both with and without a liquid pressure amplifier in a unitary air conditioning system. The estimated energy savings associated with the installation of a liquid pressure amplifier are minimal.

• Journal of Embryo Transfer
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• v.15 no.3
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• pp.203-210
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• 2000

The objective of this study was to identify a follicular fluid ingredient inhibiting the cumulus oocyte complex (COC) expansion. Thus, follicular fluid or liquid chromatographic fractions of follicular fluid was supplemented in COC culture medium. And COCs were incubated for 48 hours to investigate about cumulus expansion and also the first polar body extrusion. The results obtained were as follows; 1. The fluid of medium follicle significantly inhibited the COC expansion. 2. The fluid of large follicle inhibited the COC expansion. 3. Follicular fluid showed six major fractions at retention volumes (RVs) 1.83, 1.91, 2.15, 2.34, 2.53 and 2.74 ml after separation with Superose 12 column. Of the major fractions, fractions RV2.15, RV2.34, RV2.53 and RV2.74 inhibited both COC expansion and polar body extrusion. Especially, fractions of RV2.15 and RV2.53 significantly inhibited COC expansion, oocyte denudation and polar body extrusion. In conclusion, porcine follicular fluid contained a COC expansion inhibiting ingredient (CEI) that may be contained largely in fractions RV2.15 and RV2.53. And CEI may inhibit oocyte maturation by inhibition of oocyte denudation and extrusion of the first polar body.