• 대한기계학회논문집B
• /
• 제32권4호
• /
• pp.283-289
• /
• 2008

An experimental investigation was conducted to investigate the heat/mass transfer for impingement/effusion cooling system with inclined jet. Jets with inclined angle of 60 are applied to impingement/effusion cooling. At the jet Reynolds number of 10,000, the experiments were carried out for blowing ratios ranging from 0.0 to 1.5. The local heat/mass transfer coefficients on the effusion plate are measured using a naphthalene sublimation method. The result indicates that the inclined jet causes the non-uniform and low heat/mass transfer compared to the vertical jet. At stagnation region, the peak position is shifted from the geometrical center of injection hole due to Coanda effect and its level is higher than that of vertical jet due to increase in turbulence intensity by steep velocity gradient near the stagnation region. Further, the secondary peak region disappears because the interaction between adjacent wall jets weakens. When the initial crossflow occurs, the distorted heat/mass transfer pattern appears. As the blowing ratio (crossflow rate) increases, the heat/mass transfer distributions become similar to those of the vertical jet. This is because the effect of crossflow is dominant compared to that of inclined jet under high blowing ratio $(M{\geq}1.0)$. At low blowing ratio $(M{\leq}0.5)$, averaged Sh value is 10% lower than that of vertical jet, whereas its value at high blowing ratio $(M{\geq}1.0)$ is similar to that of vertical jet.

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
• /
• pp.190-195
• /
• 2008

The objective of this research is to determine overall heat transfer coefficients (K-value) of exterior wall, floor, and roof of Nakseonjae, a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope component. Heat flow sensors and T-type thermocouple were attached on the internal and the external surface of each building component, and real-time measurement data were collected for the three consecutive summer days. The K-values determined in this research showed good agreement with other results from open literature. Peak and annual thermal loads of the traditional residence estimated by a commercial energy simulation program were compared with those for a current apartment house. The traditional house showed lower annual cooling load than that of the current building. It may caused by the fact that the traditional building has less air-tight envelopes and no fenestration passing direct solar radiation into the space.

• Journal of Welding and Joining
• /
• 제8권2호
• /
• pp.40-52
• /
• 1990

Fatigue behavior of the AH, DH and EH grade TMCP(Thermo-Mechanical Control Process) steels was studied. High cycle and low cycle fatigue tests were carried out for the weldment and base metal of each steel. The results showed that the fatigue limit at 2 * $10^6$ cycles was 33 to 37 kg/$mm^2$ for the base metal and 30 to 34 kg/$mm^2$ for the weldment. The ratio of fatigue limit to tensile strength for TMCP steels was 0.65 to 0.71, which was a value close to the upper limit for the ordinary steels. It was also found that the high cycle fatigue behavior of TMCP steels could be affected by the microstructures of base metal. It will be necessary to have fine structure for TMCP steels to increase the fatigue resistance. In low cycle fatigue test, the fatigue lifetime of AH and DH steels accorded well with the ASME best fit curve, while that of EH steel was considerably lower than the fatigue lifetime of the other steels. Fatigue resistance of the weldment made by high heat input(180kJ/cm) welding was not lower than that made by low heat input(80kJ/cm) welding in case of high cycle fatigue, but the high heat input welding decreased the fatigue resistance in case of low cycle fatigue.

• 한국염색가공학회:학술대회논문집
• /
• 한국염색가공학회 2010년도 제3회 국제학회
• /
• pp.167-168
• /
• 2010

Non coating type Low melting yarn(L/M PET) not to use the polyurethane resin causing some problems was knitting and evaluated its dyeing characteristics, heat setting properties and flame-retardant properties without flame retardant agent or flame retardant fabric. In order to investigate the dyeing property of fabric of L/M PET, the dyeing of L/M PET was experimented at each different dyeing temperature. Higher exhaustion yield was achieved at lower temperature of L/M PET compared to regular PET. According to result of the study for the heat setting properties of L/M fiber, the K/S value of dyed L/M fiber increased as much as the heat setting temperature did. The experiment for the light fastness reached similar result to dyed PET. However washing fastness in L/M fiber showed lower grade compared with regular PET. flame-retardant efficiency of L/M PET without flame retardant agent or flame retardant fabric measured by $45^{\circ}$ burn test and Contact burn test. The flame?retardant performance of the sample was carried out according to the Korea Fire-fighting Standard.[KOFEIS 1001].

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2007년도 춘계학술대회 논문집
• /
• pp.254-257
• /
• 2007

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $200^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $200^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.

• 한국염색가공학회지
• /
• 제28권4호
• /
• pp.299-307
• /
• 2016

In order to clarify the availability of heat treatment for catechu dyeing, effect of color developing by heating process on cotton fabrics dyed with catechu extract was investigated. Dyed fabrics were heated various time(min) at $150^{\circ}C$. The cases of non-mordanting and mordanting were compared, and examined the effect of sodium acetate as an agent to promote the color developing to fabrics. Experiments with after-mordanting method showed that various colors can be obtained using catechu. K/S values of dyed fabrics with Al, Cu, Fe mordant were higher than the case of no mordant. The fabric by Cu mordanting showed 3 times to the case of no mordant. Fabrics dyed with catechu by mordanting lowered $L^*$ value while there was little change in $a^*$, $b^*$ value as the heating process progressed. Therefore, K/S values were increased due to heating process. The effects of adding sodium acetate in dyeing bath on dyed fabrics were shown higher K/S values, and the $L^*$ values were lower than those without sodium acetate according to heating time increase. The result show sodium acetate had a promoting effect on the color developing to the fabrics by heating process, it was very effective.

• 대한기계학회논문집A
• /
• 제32권11호
• /
• pp.1010-1015
• /
• 2008

In this study, the characteristics of aluminum tube hydroformed products at different extrusion type and heat treatment conditions were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, free bulge test was performed at room temperature to $300^{\circ}C$. Also mechanical properties of hydroformed products at various pre- and post-heat treatments were estimated by hexagonal prototype hydroforming test at $250^{\circ}C$. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube. As a results, hydroformability of full annealed tube is $5{\sim}8%$ higher than that of extruded and T6-treated tube. The tensile strength and elongation of T6-post heat treated indirect extrusion tube were more than 330MPa and 12%, respectively. However, T6 pre treated hydroformed product represents high strength, 330MPa and low elongation, 8%. Therefore, Hydroformability of Al6061 tube showed similar value for both extrusion types. However flow stress of direct tube showed $20{\sim}50MPa$ lower value than indirect tube.

• 한국표면공학회지
• /
• 제46권1호
• /
• pp.36-41
• /
• 2013

Friction stir welding (FSW) is a relatively new joining technique particularly for magnesium and aluminum alloys that are difficult to fusion weld. In this study, AZ31 Mg alloys were joined by FSW with shoulder diameter 11, 19 mm and rotating speed 900, 1200, 1500, 1800 rpm. The shoulder diameter and welding speed depended on the heat input during FSW process. As a result, the microstructures of stir zone were a fine grain by dynamic recrystallization. According to the larger shoulder diameter and the higher rotating speed, refined grain sizes of stir zone were grown by higher heat input, and the microhardness of stir zone was lower. The tensile strength at the shoulder diameter 19 mm, rotating speed 900 rpm was obtained maximum value. This value compared with the base metal was over 93%.

• 한국축산식품학회지
• /
• 제34권1호
• /
• pp.40-48
• /
• 2014

In this study, the effects of two different commercial starter culture mixes and processing methodologies (traditional and heat process) on the lipolytic changes of fermented sausages manufactured with turkey meat were evaluated during processing stages and storage. Free fatty acid (FFA) value increased with fermentation and during storage over 120 d in all fermented sausage groups produced with both processing methodologies (p<0.05). After drying stage, free fatty acid values of traditional style and heat processed fermented sausages were between 10.54-13.01% and 6.56-8.49%, respectively. Thiobarbituric acid (TBA) values of traditionally processed fermented sausages were between $0.220-0.450mg{\cdot}kg^{-1}$, and TBA values of heat processed fermented sausages were in a range of $0.405-0.795mg{\cdot}kg^{-1}$. Oleic and linoleic acids were predominant fatty acids in all fermented sausages. It was seen that fermented sausage groups produced with starter culture had lower TBA and FFA values in comparison with the control groups, and heat application inhibited the lipase enzyme activity and had an improving effect on lipid oxidation. As a result of these effects, heat processed fermented sausages had lower FFA and higher TBA values than the traditionally processed groups.

• Journal of Advanced Marine Engineering and Technology
• /
• 제33권2호
• /
• pp.244-251
• /
• 2009

Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.