• Korean Journal of Materials Research
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• v.14 no.12
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• pp.870-875
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• 2004

Heat flow characteristics in the newly developed Wave Heat Sink were analyzed under natural and forced convections by Icepak program using the finite volume method. Temperature distribution and thermal resistance of Wave Heat Sink with/without air vent hole on the top of fin were compared with those of a commercial Al extruded heat sink(Intel Heat Sink). Under the natural convection, the maximum temperature was $45.1^{\circ}C$ in the air vent hole typed Wave Heat Sink, which was superior to that of Intel Heat Sink. The thermal resistance was $2.51^{\circ}C/W$ in the air vent hole typed Wave Heat Sink, and it changed to $2.65^{\circ}C/W\;and\;2.16^{\circ}C/W$ with changes of gravity direction and fin height, respectively. Under the forced convection, the maximum temperature became lower than that under the natural convection. In addition, the thermal resistance lowered in the air vent hole typed Wave Heat Sink with higher fin height and it decreased with increasing the air flux.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.563-569
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• 2008

During braking operation, the surfaces of disk have severe contact conditions and high frictional heat would be generated between disk and pad surfaces. The heat makes high temperature gradient on disk surfaces and results in thermal deformation. To enhance the frictional heat dissipation, heat pipes are embedded in the ventilated type disk along the radial direction. The temperatures of the inner vent type disk and the brake disk with heat pipes are compared at the same operating conditions. By comparison a brake disk with heat pipes has higher cooling performance than the inner vent type disk.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.193-202
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• 2022

Manholes and underground spaces are installed to manage the buried heat transport pipes of the district heating system, and the corrosion damage of the equipment placed in this space often occurs. The purpose of this work is to identify locations with a high risk of corrosion damage in the air vent and to establish preventive measures based on precise analysis via sampling of heat transport pipes and air vents that have been used for about 30 years. The residual thickness of the air vent decreased significantly by reaching ~1.1 mm in thickness, and locations of 60~70 mm away from a transport pipe were the most vulnerable to corrosion. The energy dispersive X-ray spectroscopy (EDS) analysis was performed in the corroded oxides, and it was found that chloride ion was contained in the corrosion products. Anodic polarization tests were carried out on the air vent materials (SPPS250, SS304) with varying the amounts of chloride ions at two different temperatures (RT, 80℃). The higher concentration of chloride ions and temperature are, the lower corrosion resistances of both alloys are.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.117-123
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• 2004

A brake disc with helical grooved vent in radial direction is proposed for the improvement of thermal dissipation. The heat transfer phenomenon is analyzed far both the proposed disc and the conventional one using finite element method. The thermal dissipation is considerably influenced by the geometrical differences of the brake discs. The results of the analysis show that the proposed brake disc with helical grooved vent has the improved performance to dissipate the thermal energy more effectively.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.196-202
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• 2020

The air vent connected to a heat supply pipeline in the district heating system has been used to eliminate the existing air in the pipe, which has a detrimental effect on corrosion durability and heat efficiency. Recently, the air vent installed under a manhole for 22 years was corroded and several pinholes were detected in the front-end of the air vent. To identify the cause of the failure, thickness reduction, corrosion products, and water quality were examined. The corrosion damage was significant at the outside of the front-end of the air vent where the insulator was covered. While a thin oxide layer was formed in the interior of the tube, the coarse and porous corrosion products consisting of magnetite and hematite were found externally. Water flowing into the thermal insulator was absorbed by the insulator following hydrolysis. The hydrolyzed insulator ejected the corrosion factors such as Cl^-, SO₄^2-, and NH₄⁺. The findings suggest that the corrosion under insulation due to rain water is the main cause of the underlying failure in the air vent.

• Corrosion Science and Technology
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• v.22 no.2
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• pp.115-122
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• 2023

This study aimed to elucidate causes of corrosion of heat transport pipes and air vents installed under a manhole of heat transport facilities and suggest effective anticorrosive measures by applying paints or adhesive tapes. It was found that air vent corrosion was attributed to corrosion under insulation caused by the inflow of water and the enrichment of chloride ions. The infiltrated water caused a hydrolysis of polyurethane foam (PUF) insulation by concentrating chloride ions at the interface between a pipe and the PUF. As insulator deteriorated, more chloride ions were eluted as confirmed by ion chromatograph (IC) analysis. As an effective method to prevent air vent corrosion, different types of paints and adhesive tapes with higher corrosion resistance on chloride ions were applied and environmental resistance tests were performed with those samples. Based on environmental test results of samples exposed to 10% HCl solution, it was revealed that a wax tape was the most adequate from a viewpoint of stability at operating condition, environmental resistance, surface treatment, and field applicability.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.247-253
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• 2002

In this study, reduced-scale experiments were conducted to analyze smoke movement in tunnel fire with roof vent. The 1/20 scale experiments were carried out under the Froude scaling using gasoline pool fire ranging from 7.3 to 15.4 cm in diameter with total heat release rate from 1.0 to 8.46kw. In case of 1 m high vent, smoke front reached to the tunnel exit at about 16 sec delayed with ventilation. The delay time grew longer with the vent height. The temperature after the vent was lower than that without the vent. The exit temperature declined maximum of $20^{\circ}C$ after passing the vent. It was confirmed that the thickness of smoke layer was maintained uniformly under the 25% height of the tunnel through the visualized smoke now by a laser sheet and the digital camcorder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.383-384
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• 2006

Ventilated disc was improved for reducing judder and heat. But the crack among vent holes occurs due to stress concentration. We investigate the stress distribution of vent holes. The vent holes with shape of a right angle, a chamfer and rounding was analyzed. The result of FEA was that rounded vent holes have a minimum stress. Also Maximum stress distributed within holes. Therefore We suggest that the rounded vent holes is good to reduce the crack.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.63-69
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• 2014

Domestic automobile companies have adopted drum type brake system for commercial vehicles. However recently those companies have been applying disc-brake system to solve vehicle control-instability and inefficient heat discharge performance of conventional drum brake system for a medium commercial vehicle. Because the kinetic energy of a running commercial vehicle is relatively high, the brake system should discharge lots of heat energy while braking. A ventilated type brake disc has been used to increase heat discharge performance of a brake system. The vent structure of a disc highly affects cooling efficiency. This paper compares thermal characteristics of three types of vent structure in JASO C421 braking condition. It is found that the slant bend type disc has the lowest temperature and thermal stress distributions in the braking condition.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.189-195
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• 2020

Two air vents situated on a heat transport pipe in district heating system were exposed to the same environment for 10 years. However, one air vent was more corroded than the other. It also had a hole on the top of the front-end pipe. Comparative analysis was performed for these air vents to identify the cause of corrosion and establish countermeasures. Through experimental observation of the damaged part and analyses of powders sampled from air vents, it was found that corrosion was initiated at the top of the front-end pipe. It then spread to the bottom. Energy dispersive X-ray spectroscopy results showed that potassium and chlorine were measured from the corroded product in the damaged air vent derived from rainwater and insulation, respectively. The temperature of the damaged air vent was maintained at 75 ~ 120 ℃ by heating water. Rainwater-soaked insulation around the front-end pipe had been hydrolyzed. Therefore, the damaged air vent was exposed to an environment in which corrosion under insulation could be facilitated. In addition, ion chromatography and inductively coupled plasma measurements indicated that the matrix of the damaged front-end pipe contained a higher manganese content which might have promoted corrosion under insulation.