• Design & Manufacturing
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• v.13 no.2
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• pp.49-53
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• 2019

The temperature distribution and lifetime of molds were predicted by computer simulation analysis with various spraying and blowing process of high pressure die casting. After varying the spraying angle and time, the mold temperature, heat exchange and mold life were predicted. As the spraying angle increases, the maximum temperature of the mold decreases, which is because the spraying area increases and the heat exchange with the mold increases. Heat exchange occurs more actively in the blowing process than in the spraying process. This is because the cooling is not performed due to the steam generation. When the spraying angle is 50 degree, the minimum life of the mold is analyzed 200 times. After adjusting the blowing time from 5s to 3s, the minimum lifetime of the mold has been increased almost twice.

• Elastomers and Composites
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• v.58 no.2
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• pp.65-69
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• 2023

To reduce the weight of the engineering plastic Nylon 6 resin, two high-temperature foaming agents, p-toluenesulfonyl semicarbazide (PTSS) and 5-phenyltetrazole (5-PT) (0-10 phr), were added and foamed without other additives. We investigated the effects of the foaming agent type and content on the foam density (g/cm³) and percent weight reduction rate of the Nylon 6 foam, and 5-PT exhibited better foaming performance than PTSS. In the case of 5-PT, the weight reduction rate was above 36% when the blowing agent content was 1.5 phr or higher, indicating that 5-PT is an effective blowing agent for reducing the Nylon 6 foam weight. Additionally, we studied the effect of the nucleating agent Talc content (0-0.4 phr) on Nylon 6 foaming, and the nucleating agent Talc considerably reduced foaming.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.547-548
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• 2010

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.645-652
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• 1994

The leading edge of a turbine blade was simulated as a circular cylindrical surface. The effect of free-stream turbulence on the mass transfer upstream of the injectionhole has been investigated experimentally. The effects of injection location, blowing ratio on the Sherwood number distribution were examined as well. The mass transfer coefficients were measured by a naphthalene sublimation technique. The free-stream Reynolds number based on the cylinder diameter is 53,000. Other conditions investigated are: free-stream turbulence intensities of 3.9% and 8.0%, injection locations of $40^{\circ}$, $50^{\circ}$, and $60^{\circ}$ from the front stagnation point of the cylinder, and blowing ratios of 0.5 and 1.0. The role of the horseshoe vortex formed upstream edge of the injected jet is dicussed in detail. When the blowing ratio is unity, and the coolant jet is injected at $40^{\circ}$, the mass transfer upstream of the jet is not affected by the coolant jet at all. On the other hand, when the injection hole is located beyond $50^{\circ}$, the mass transfer upstream edge of the injection hole suddenly increases due to the formation of the horseshoe vortex, but it dereases as the free-stream turbulence intensity increases because the strength of the horseshoe vortex structure becomes weakened. The role of the horseshoe vortex is clearly evidenced by placing a rigid rod at the injection hole instead of issuing the jet. In the case of the rigid rod, the spanwise Sherwood number upstream of the injection hole is much larger due to the intense influence of the horseshoe vortex.

• Journal of the Korean Institute of Gas
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• v.9 no.1 s.26
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• pp.16-20
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• 2005

CFC-11 and HCFC-l4lb have been used as blowing agents for rigid polyurethane foam insulation of LNG storage tank. But CFC-11 and HCFC- l4lb deplete ozone layer in the stratosphere. So in leading countries, the use of CFC-11 has been prohibited since 1995 and the use of HCFC-l4lb will be prohibited from 2005. Much efforts and studies have been done about alternative blowing agents and insulations blown by alternative blowing agents. This paper deals with polyurethane foams (PUFs) blown by HFC-365mfc, shows their physical and mechanical characteristics and thermal performance. These data are compared with the results of PUFs blown by HCFC-l4lb. From these test results, PUFs blown by HFC-365mfc show good mechanical and thermal characteristics. It is possible to use PUFs blown by HFC-365mfc as main insulation of membrane type LNG storage tank.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.655-663
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• 2013

Several studies of film cooling were accomplished with a secondary flow channel parallel to the main flow. In real turbine blades, however, the direction of the secondary flow channel is generally normal to the main flow. Thus, this study performs a numerical analysis to investigate the effects of the direction of secondary flow on the effectiveness of double-jet film cooling. The blowing ratio is 1 and 2, and the lateral injection angle is $22.5^{\circ}$. The parallel channel case creates a well-developed anti-kidney vortex with a blowing ratio of 1, and the laterally averaged film cooling effectiveness of the parallel channel is enhanced compared to the normal channel. The normal channel shows higher performance with a blowing ratio of 2. Both cases show high film cooling effectiveness. These phenomena can be attributed to a high blowing ratio and flow rate rather than an anti-kidney vortex.

• Fire Science and Engineering
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• v.13 no.1
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• pp.3-10
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• 1999

We had investigated combustion properties of natural textile dusts. Decomposition properles of natural textile dusts scavenged by precipitator of spinning factoη were investigated using D DSC(Differential Scanning Calorimeter) and TGA(Thermogravimetric Analysis) by temperature c changes. Combustion pro야rties of natural textile according to size distribution and amount were c checked as temperature variation according to time using spontan$\infty$us ignition apparatus. M Moreover, combustion properties with blowing or without blowing condition were checked in order to investigate combustion prope$\pi$ies in spontaneous ignition apparatus according to flow c condition of air. As results of thermal analyses, increase in r머sing tern야:rature causes initial smold벼ng t temperature to move towards low temperature section 뻐d i띠디떠 smoldering temperature was d de$\sigma$eased more remarkably in atmosphere than in inert gas and that condition allowed heating v value to increase considerably. In addition, as amount and size distribution of natural textile d dusts were increased, i띠ti머 smoldering temperature was lowered. All of combustion forms were s smoldering combustion. Initial smold밍ing temperature was low more slightly with blowing c condition than without blowing condition in sp$\alpha$ltaneoUS ignition apparatus, which condition m made heatim;!; value high.

• Macromolecular Research
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• v.17 no.1
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• pp.44-50
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• 2009

Rigid polyurethane foams (PUF)s were synthesized with environmentally friendly blowing agents such as a cyclopentane/distilled water (10.0/1.0, pphp) mixture and distilled water only for four different silicone surfactants having different silicone/polyether ratios. An attempt was made to reduce the thermal conductivities of the PUF samples by varying the concentration and the silicone/polyether ratio of the various silicone surfactants. The scanning electron microscopy (SEM) results indicated an optimum concentration of the silicone surfactant of about 1.5 to 2.5 phpp for various surfactants to reduce the cell size and lower the thermal conductivity. The silicone surfactant having a higher silicone/polymer ratio showed a smaller cell size and, therefore, demonstrated the lower thermal conductivity of the PUF samples. From the relation between the thermal conductivity and the cell size of the PUF samples, the smaller cell size improved the thermal insulation property of the rigid PUF for both the PUF samples blown by the cyclopentane/distilled water (10.0/1.0, pphp) mixture and distilled water only. If the blowing agent is fixed, then the cell size is an important factor to decrease the thermal conductivity of the PUF samples. These results indicated that rigid PUF samples having lower thermal conductivity can be obtained by choosing a silicone surfactant containing a higher silicone/polyether ratio, as well as an optimum content of the surfactant.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.200-207
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• 2017

The purpose in having a control surface on ships is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portions. A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the manoeuvring characteristics of the ship. In this paper, two-dimensional flow characteristics of a flapped rudder and a water-blowing control rudder were accomplished respectively by PIV method in a circulating water channel. Model test has been carried out with different angles of attack of main foil (NACA 0012) and flap's deflection angles to predict the performance of the flapped rudder and the water-blowing control rudder. The 2-frame particle tracking method has been used to obtain the velocity distribution in the flow field. $Re{\fallingdotseq}3.0{\times}10^4$ has been used during the whole experiments and measured results have been compared with each other.

• Food Science and Preservation
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• v.22 no.1
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• pp.154-157
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• 2015

To maintain the freshness and to prevent browning of cut Kimchi cabbages, the effect of the cutting process using a ceramic knife under $N_2$ blowing on the quality of the cut Kimchi cabbages was investigated. Kimchi cabbages cut with a ceramic knife under $N_2$ gas blowing conditions (NC) were stored at $5^{\circ}C$ for 7 days, and their weight reduction ratio and the browning degree and appearance were compared with those of the control treatment samples (OS; cut with a stainless steel knife under normal air, OC; cut with a ceramic knife under normal air). The weight reduction ratios were 0.07~0.13%, and the NC treatment showed the lowest reduction ratio among all the treatments (p<0.05). The Hunter L values increased, but the a and b values decreased after 5-day storage in all the treatments. The NC treatment had higher L values but lower a and b values than the OS and OC treatments. The browning degrees by Hunter color value, PPO activity, and appearances were the least in the NC treatment (p<0.05). The cutting process with a ceramic knife under $N_2$ blowing could be applied to the cutting of vegetable products and for minimal fruit processing.