• Journal of Institute of Convergence Technology
• /
• v.2 no.1
• /
• pp.1-6
• /
• 2012

The cold chain system in South-East Asia is requiring to maintain freshness of refrigerated or frozen food. In this study, Thermal storage system using Phase change material (PCM) was developed and evaluated its performance about temperature and cold keeping time. For various application of cold chain system, we developed portable cold box, cold roll container and freezing station. Keeping time on laboratory tests of portable cold box in case of refrigeration and freezing were 6 hours and 4 hours, respectively. Cold container was developed to 2.5 ton scale. Evaluation in Indonesia, it was showed to keep the setting temperature of $-10^{\circ}C$ over 40 hours at $30^{\circ}C$ of ambient air. Freezing station using PCM was kept over 24 hours under $-20^{\circ}C$.

• Journal of the Society of Naval Architects of Korea
• /
• v.53 no.6
• /
• pp.473-481
• /
• 2016

Thick plate is currently widely used in shipbuilding due to the increasing of size of ships. However, its use has increased welding groove angles and volume. The welder's technique must be good enough to improve productivity while preventing defects. Generally, the groove angle can be reduced to less than a flux-cored arc welding (FCAW) machine setting of $35{\pm}5^{\circ}$, requiring fewer welding passes while maintaining high productivity and reduced heat input. Therefore, welding technique can be prevented by improved mechanical properties and welding deformation. Welding defects such as lack of fusion (LF), lack of penetration (LP) and hot cracking should be considered when reducing the groove angle for related applications. In this study, a welding groove angle of $25{\pm}5^{\circ}$ is verified as suitable for FCAW design and fabrication. The experimental results confirm the effects on the strength characteristics of FCAW weldment when reducing groove angle to improve the productivity of shipbuilding industries.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.17 no.4
• /
• pp.382-394
• /
• 1988

Dynamic characteristics of thermally-forced stratification process in a square enclosure with a linear temperature profile at the side walls have been investigated through flow visualization experiment and numerical analysis. The experiment was performed on air with the Rayleigh numbers of order $10^5$. A particle tracer method is used for the flow visualization and to obtain a sudden linear temperature profile at the side walls copper blocks which already have a linear temperature profile are come into contact with the thin copper plates of the test section. Immediately a meridional circulation is developed and heat transfer takes place from the wall to the interior region by circulation of fluid and finally a thermal stratification is achieved. In the numerical study, QUICK scheme for convective terms, SIMPLE algorithm for pressure correction, and the implicit method for the time marching are adopted for the integration of conservation equations. Comparison of flow visualization and numerical results shows that the developing flow patterns are very similar in dynamic nature even though there is a time lag due to the inevitable time delay in setting up a linear temperature profile. For high Rayleigh numbers, the oscillatory motion is likely to take place and stratified region is extended. However, initial temperature adjustment process is much slower than that for low Rayleigh numbers.

• Applied Chemistry for Engineering
• /
• v.22 no.4
• /
• pp.423-428
• /
• 2011

Hydration characteristics of cement containing zeolite mined at Daepo in Gyeongbuk province were studied for use as a mineral admixture. The cement paste containing zeolite was characterized by the measurement of heat evolution, XRD, EDS, nitrogen adsorption and mercury intrusion porosimetry. The cement paste containing zeolite exhibited tendencies toward acceleration of paste setting and promotion of cement hydration with the increase of zeolite content. The flow of mortar containing zeolite strongly reduced with increase of zeolite content. Compressive strength of the mortar containing zeolite increased very rapidly at an early age in comparison with plain mortar. These results would be related to aluminum species escaped from zeolite particles during the alkali dealumination of zeolite by the hydration process of cement.

• Journal of Ceramic Processing Research
• /
• v.19 no.5
• /
• pp.407-412
• /
• 2018

In this study, we have made a cement based inorganic insulation material and added CSA (Hauyne Clinker) to reduce the demolding time and enhance the handling workability. CSA contents were varied by 0%, 1%, 3%, 5% and the atmospheric steam curing was tried for enhancing the compressive strength. As the CSA contents are increased to 5%, a rapid reaction of hydration caused the sinking of the slurry. So, the setting-retarder was added to control the reaction of hydration. By this, the sinking of the slurry was controlled but the height of the green body after expansions was a little bit lowered. In the CSA-added slurry, it was possible to demold within 24 hours and in case of CSA 5%-added, the sufficient workability was secured. Atmospheric steam curing (temperatures $-40{\sim}80^{\circ}C$, for 6~10 hrs.) was attempted to improve the compressive strength and found that an excellent strength of 0.25 MPa was achieved at $80^{\circ}C$ for 8 hrs. Specific gravity was about $0.12{\sim}0.13g/cm^3$ and heat conductivity was about 0.045 W/mK in all specimens. This strategy significantly improves the compressive strength of CSA 5%-added specimen up to 25% compared to without CSA added specimen.

• Textile Coloration and Finishing
• /
• v.34 no.3
• /
• pp.197-206
• /
• 2022

The purpose of this study was to confirm the optimal spinning conditions for PLA (Polylactic acid) as a fiber forming polymer. According to the melt spinning test results of PLA, the optimal spinning temperature was 258℃. However, it needs to note that relatively high pack pressure was required for spinning at 258℃. At an elevated temperature, 262℃, mono filament was broken easily due to hydrolysis of PLA at a higher temperature. In case of fiber strength, it was confirmed that the draw ratios of 2.7 to 3.3 were optimal for maximum strength of melt spun PLA. Above the draw ratio, 3.3, the strength of the PLA fibers was lowered. It was presumed that cleavage of the PLA polymer chain over maximum elongation. The heat setting temperature of GR (Godet roller) showed that the maximum strength of the PLA fibers was revealed around 100℃. The degree of crystallinity and the strength of the PLA fibers were decreased above 100℃. The optimal take-up speed (Spinning speed) was around 4,000m/min. Thermal analysis of PLA showed 170℃ and 57℃ as Tm (melting temperature) and Tg (glass transition temperature), respectively.

• Journal of the Korean institute of surface engineering
• /
• v.56 no.1
• /
• pp.84-93
• /
• 2023

The spent nuclear fuel is burned during the planned cycle in the plant and then generates elements such as actinide series, fission products, and plutonium with a long half-life. An 'interim storage' step is needed to manage the high radioactivity and heat emitted by nuclides until permanent-disposal. In the case of Korea, there is no space to dispose of high-level radioactive waste after use, so there is a need for a period of time using interim storage. Therefore, the intensity of neutrons and gamma-ray must be determined to ensure the integrity of spent nuclear fuel during interim storage. In particular, the most important thing in spent nuclear fuel is burnup evaluation, estimation of the source term of neutrons and gamma-ray is regarded as a reference measurement of the burnup evaluation. In this study, an analysis of spent nuclear fuel was conducted by setting up a virtual fuel burnup case based on CE16×16 fuel to check the total amount and spectrum of neutron, gamma radiation produced. The correlation between BU (burnup), IE (enrichment), and CT (cooling time) will be identified through spent nuclear fuel burnup calculation. In addition, the composition of nuclide inventory, actinide and fission products can be identified.

• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.80-99
• /
• 2023

This paper presents the results of investigating the change in welding residual stresses of the core shroud, which is one of subcomponents in reactor vessel internals, performing finite element analysis. First, the welding residual stresses of the core shroud were calculated by applying the heat conduction based lumped pass technique and finite element elastic-plastic stress analysis. Second, the temperature distribution of the core shroud during the normal operation was calculated by performing finite element temperature analysis considering gamma heating. Third, through the finite element viscoelastic-plastic stress analysis using the calculated temperature distribution and setting the calculated residual stresses as the initial stress state, the variation of the welding residual stresses was derived according to repeating the normal operation. In the viscoelastic-plastic stress analysis, the effects of neutron irradiation on mechanical properties during the cyclic normal operations were considered by using the previously developed user subroutines for the irradiation agings such as irradiation hardening/embrittlement, irradiation-induced creep, and void swelling. Finally, the effect of neutron irradiation on the welding residual stresses was analysed for each irradiation aging. As a result, it is found that as the normal operation is repeated, the welding residual stresses decrease and show insignificant magnitudes after the 10^th refueling cycle. In addition, the irradiation-induced creep/void swelling has significant mitigation effect on the residual stresses whereas the irradiation hardening/embrittlement has no effect on those.

• Journal of Animal Environmental Science
• /
• v.11 no.3
• /
• pp.177-188
• /
• 2005

In this study, the thermal environmental factors in a layer f(arm such as dry bulb temperature, relative humidity, black globe temperature and illumination intensity were measured and analyzed to serve as basis for effective design and plan of poultry houses. The correlation analysis between the different factors was also done. Heat Index as measure of the thermal stress was also calculated and analyzed. A $1,000m^2$ laying house, 4 meters high with 52,000 layers in six-stage type cages was used in the measurement of the different environmental parameters. The results were as follows; 1. The temperature of the inside air and materials was directly related to the increase in aerial temperature based on the dry-bulb, black globe temperature reading. The correlation factor of the outside to inside air based on dry bulb setting was very significant at 0.927 The dry bulb temperature for inside temperature ranged from $19.9\~28.8^{\circ}C\;with\;SD+2.2^{\circ}C$ while that of the outside air was $16.2\~33.1^{\circ}C,\;SD+3.5^{\circ}C$. In addition, the temperature of the inside air was very stable. 2. The black globe temperature of the inside air ranged from $20.1\~28.8^{\circ}C,\;SD+2.3^{\circ}C$ while that of the outside air was $16.2\~47.5^{\circ}C,\;SD+6.0^{\circ}C$. 3. The relative humidity of the outside and inside air was $72.4\~100\;and\;50.2\~85.6\%$ with an average of $89.2\;and\;71.7\%$, respectively. 4. The illumination intensity in the laying house was less than 7 lux, with an average of $1.2\~2.5lux$ relative to height indicating that the laying house was well isolated from outside radiation. 5. The heat index of the inside air of the laying house had a high variation from $20.5^{\circ}C,\;SD+2.5^{\circ}C$ while that of the outside air was $13.1\~45.5^{\circ}C$, with an average of $21.6^{\circ}C,\;SD+6.3^{\circ}C$.

• Korean Journal of Materials Research
• /
• v.12 no.8
• /
• pp.624-633
• /
• 2002

In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, MmN $i_{4.5}$M $n_{0.5}$Z $r_{x}$(x=0, 0.025, 0.05, 0.1), are prepared by adding excess Zr in MmN $i_{4.5}$M $n_{0.5}$ alloy. The various parts in hydrogen storage vessel consisted of copper pipes reached the setting temperature within 4~5 minutes after heat addition, which indicated that storage vessel had a good heat conductivity required in application. The performance test on storage vessel filled with rare-earth metal alloys of 1000 gr was also conducted after hydrogen charging for 10 min at $18^{\circ}C$ under 10 atm. It showed that the average capacity of discharged hydrogen volume was found to be for $MmNi_{4.5}$ $Mn_{0.5}$ and $MmNi_{4.5}$ $Mn_{x}$ 0.5/$Zr_{samples}$ indicated that the released amount of hydrogen for this $AB_{5}$ type alloys was more than 92 % of theoretic value, and also it was found that the optimum discharging temperature for obtaining an appropriate pressure of 3 atm was determined to be $V^{\circ}C$ for $MmNi_{4.5}$ $Mn_{0.5}$$Zr_{x}$(x=0, 0.025, 0.05, 0.1) hydrogen storage alloys. The released amount of these hydrogen storage samples was 125 $\ell$ , 122.4 $\ell$ and 108.15 $\ell$/kg for $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{0.025}$ $MmNi_{4.5}$M $n_{0.5}$Z $r_{0.05}$, and MmN $i_{4.5}$ Mn_0.5$Zr_{0}$, at $70^{\circ}C$ respectively. Amount of the 2nd phases increase with increase on Zr contents in $MmNi_{4.5}$$Mn_{0.5}$ $Zr_{ 0.1}$/ alloy. This phenomenon indicates that$ ZrNi_3$ in $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{x}$ / phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage. As the Zr contents increase, the activation time and the plateau pressure decreases and sloping of the plateau pressure increases.creases.eases.s.