• Journal of Power System Engineering
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• v.14 no.4
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• pp.11-16
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• 2010

The evaporation heat transfer characteristics of propane(R-290) in horizontal small diameter tubes were investigated experimentally. The test tubes have inner diameters of 1 mm and 4 mm. Local heat transfer coefficients were measured at heat fluxes of 12, $24\;kW/m^2$, mass fluxes of 150, $300\;kg/m^2s$, and evaporation temperature of $15^{\circ}C$. The experimental results showed that the evaporation heat transfer coefficient of R-290 has an effect on heat flux, mass flux, tube diameter, and vapor quality. The evaporation heat transfer of R-290 has an influenced on nucleate boiling at low quality and convective boiling at high quality. The evaporation heat transfer coefficient of R-290 increases with decreasing inner tube diameter. And the evaporation heat transfer coefficient of R-290 is about 1~3 times higher than that of R-134a.

• Geomechanics and Engineering
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• v.32 no.4
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• pp.445-452
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• 2023

Temperature is one of the important factors affecting the permeability of water in the soil. In the present study, the impact of water temperature on hydraulic conductivity (k) with and without coarse aggregations by considering six types of soils was analyzed. Moreover, the effect of sand and gravel presence in the soil was investigated through the infiltration based on constant and inconstant water head experiments. Results indicated that by increasing the water temperature, adding gravel to sandy soil caused the hydraulic conductivity to raise. It is supposed that the gravel decreased the contact surface between the water and the soil aggregates. It is deduced that due to decreasing kinetic energy, k tends to have lower values. Furthermore, adding the sand to sandy silt-clay soil showed that the sand did not have a marginal effect on the variation of k since the added sand cannot increase the contact surface like gravel. Finally, increasing the main diameter of the soil will increase the effect of the water temperature on hydraulic conductivity.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.20 no.1
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• pp.1-7
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• 2024

To In this study, a nozzle which is designed to work as expansion device was installed in a refrigeration system and performance test was conducted. The nozzle has 0.8mm, 1.0mm, 1.2mm diameter and inserted in a body of the devices. System performance was compared with a electronic expansion device(EEV, electric expansion valve) and designed nozzles at the environmental conditions such as dry bulb and wet bulb temperature. To reduce energy loss in the evaporator, a nozzle was inserted into the evaporator. In the comparison test, the opening of the EEV was adjusted to the same diameter as the 3 nozzles, and the experiments conducted at a 27℃ dry bulb temperature and 19.5℃ wet bulb temperature with 50% relative humidity as defined at KS C 9306 standard. To find out the effect of the environmental condition, the bulb temperature was varied 5 degree lower and higher than the standard condition temperature with the same relative humidity condition at 50%. The air flow rate to the evaporator was also changed 4, 7 and 10 m³/min. As results, the temperature drop in the nozzle was 153% higher than that of the EEV and the enhancement of the performance(COP) was up to 125.7% if install the nozzles in the refrigeration system. The highest performance was obatained at 1.0mm diameter nozzle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.215-222
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• 2004

Synthesis of multi-walled carbon nanotubes on a nickel-nitrate-deposited substrate using an ethylene fueled inverse diffusion flame was illustrated. The deposition of nickel-nitrate particles on substrates was used for the smaller-diameter nanotubes than those formed in our previous studies. Also the effect of temperature variations on the size of formed nanotubes was investigated. The diameters of formed multi-walled carbon nanotubes were ranging from 15 to 100 nm in the several radial locations. In case of using a nickel-nitrate-deposited substrate, the smaller-diameter carbon nanotubes were synthesized than those in case of using the substrate with melted nickel-nitrate. In the formation region of carbon nanotubes, the diameter of formed nanotubes was tend to be decrease as the radial distance form the flame center was increased, that is the decreased substrate temperature.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.109-116
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• 2016

Polymethyl methacrylate is commonly used in the outer lens of automotive rear lamps. However, if the lens warps above the allowable limit, it may lead to faulty connection with the housing, and failure of the assembly. This study investigated the effects of gate diameter and cooling line distance in the mold design for automotive outer lens. The optimal gate diameter and cooling line distance to minimize the warp of the outer lens were derived as 3.0 mm and 50-60 mm respectively, and the cooling temperature to minimize warp was shown to be $60-80^{\circ}C$ (mold surface temperature $48-67^{\circ}C$). A higher cooling temperature may somewhat mitigate the warp, but is undesirable because it may cause injection molding problems, such as sinks. A mold was constructed matching the optimal design and the produced lens properties, particularly the degree of warp, were comparable with the CAE predictions.

• Macromolecular Research
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• v.15 no.2
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• pp.154-159
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• 2007

Polyaniline (PANI) nanospheres, 4 run in diameter, were fabricated by the microemulsion polymerization of octyltrimethyl ammonium bromide (OTAB). The size of the PANI nanoparticles could be controlled as functions of the surfactant concentration, surfactant spacer length and polymerization temperature. The diameter of the PANI nanospheres decreased with increasing surfactant concentration and decreasing temperature. The PANI nanoparticles revealed enhanced conductivity compared to conventional bulk PANIs. In addition, the PANI nanoparticles could be applied as optically transparent conducting materials due to their high conductivity and the nanosize effect. With 9 wt% PANI in the PC matrix, the PANI/PC film exhibited a conductivity of $8.9\times10^{-3}S/cm$ and transparency exceeding 95% over the entire visible light range.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2512-2517
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• 2007

Effect of natural convention for hot plate surface temperature uniformity was studied by experiments that were adjusted height of chamber and temperature difference. The hot plate chamber is composed of the hot plate and the upper heater and adiabatic vertical wall. The hot plate diameter is 220mm and maintains temperature at $150^{\circ}C$. Flow pattern compares with surface temperature and confirms that natural convection affects on temperature uniformity of hot plate surface. In case, temperature non-uniformity of hot plate surface is due to heater pattern, lots of weak and small flow cells more improve temperature uniformity than stronger flow cells or non-developing flow cell. Improve temperature uniformity $1.2^{\circ}C$ when developing weak and small flow cells.

• Progress in Superconductivity
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• v.9 no.2
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• pp.188-192
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• 2008

We investigated the size effect on quench development in $Au/YBa_2Cu_3O_7$ (YBCO) thin film meander lines on sapphire substrates. The meander lines were fabricated by patterning YBCO films coated with gold layers. The lines were subjected to simulated AC fault current, and immersed in liquid nitrogen during the experiment. After the initial rapid rise, the resistance increased moderately and then slowly. In 4 inch-diameter meander lines, the period during which the resistance increased moderately was considerably longer than in 2 inch-diameter line. Moderate increase of resistance was originated from quench propagation. The film temperature was about 180 K at the point when the propagation was completed. The rate of resistance increase after the quench completion was not affected by the film size.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.537-544
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• 2008

In this paper, flow characteristics of an adiabatic capillary tube in a transcritical $CO_2$ have been investigated employing the homogeneous model. The model is based on fundamental equations of mass, energy and momentum which are solved simultaneously. Two friction factors(Churchill) and viscosity(McAdams) are comparatively used to investigate the flow characteristics. Supercritical and subcritical thermodynamic and transport properties of $CO_2$ are calculated employing EES property code. Flow characteristics analysis of $CO_2$ adiabatic capillary tube is presented to offer the basic design data for the operating parameters. The operating parameters considered in this study include inlet temperature and pressure of an adiabatic capillary tube, evaporating temperature and inner diameter tube. The main results were summarized as follows : inlet temperature and pressure of an adiabatic capillary tube, evaporating temperature, mass flowrate and inner diameter of $CO_2$ adiabatic capillary tube have an effect on length of an adiabatic capillary tube.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.31-40
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• 2009

As the measurement of strain-gage type cone penetrometer is influenced by the temperature change during penetration, the temperature is a factor producing an error of the cone tip resistance. In this study, the 0.5 mm diameter temperature transducer and 7 mm diameter micro cone penetrometer are manufactured by using FBG sensors to evaluate the effect of temperature on the cone tip resistance. Design concepts include the cone configuration, sensor installation and the temperature compensation process. The test shows that the tip resistance measured by strain gauge is affected by the temperature change. The error of the tip resistance increases with an increase in temperature change, while the temperature effect on the tip resistance of FBG cone is effectively compensated by using FBG temperature transducer. Temperature compensated tip resistance of the strain gauge cone shows the good matched profile with FBG cone which performs real-time temperature compensation during penetration. This study demonstrates that the temperature compensation by using FBG sensor is an effective method to produce the more reliable cone tip resistance.