• 설비공학논문집
• /
• 제13권1호
• /
• pp.38-47
• /
• 2001

The operation characteristics of variable conductance heat pipe(VCHP) were numerically investigated by using 1-dimensional diffuse-front model. For different boundary conditions, the amount of non-condensible gas charge and dimension of gas reservoir were obtained by iterative calculation. It is found that the amount of non-condensible gas charge and dimensions of gas reservoir have an effect on the temperature control of condenser for the given operating condition of VCHP. The numerical results show that VCHP has an excellent capability of temperature control when subjected to a change in the heat input.

• 한국안전학회지
• /
• 제19권2호
• /
• pp.93-97
• /
• 2004

Slab formwork consists of sheathing, stringer, hanger and shore. There are several types of adjustable individual shores. In constructions site, pipe supports are usually used as shores. The strength of a pipe support is decreasing as it is frequently being used at the construction site. In this study, 2857 pipe supports were bought to fine out the strength change of used pipe support and unused pipe supports according to aging. Among these pipe supports, 2337 pipe supports were lent to the construction companies free of charge. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports almost equaled to the strength of new pipe supports until 191 days, but the strength of used pipe supports at 191 days was lower than the strength of new pipe supports. So, the strength of used pipe supports at 191 days was not satisfied the specification of KS F 8001. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the paresent study results will be able to provide a firm base to design slab formwork and test the performance of used temporary structure and prevent formwork collapses.

• 설비공학논문집
• /
• 제12권7호
• /
• pp.659-666
• /
• 2000

Heat transfer characteristics of a heat exchanger for low temperature waste heat recovery using oscillating capillary tube heat pipe were evaluated against the charge ratio variation of working fluid and various working fluids. R-l42b, R-22 and R-290 were used as working fluids. The heat exchanger was composed of heat pipe with capillary tube bundles, having a 2.6mm in outer diameter, 1.4mm in inner diameter with 101m long, and 40 turns. Charge ratio of working fluid was 40% and 50%. Water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and9~27 kg /$m^2s$,, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-l42b and R-290 and it was proportional to Figure of merit for thermosyphons. As a result, it was thought that R-22 was the most suitable working fluid of waste heat recovery for low temperature waste heat recovery.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.247-250
• /
• 2009

Sodium heat pipe for high-temperature solar thermal application was manufactured and tested for transient and steady-state operations. Total length of the heat pipe was 650 mm and the outer diameter was 12.7 mm. Thermal performance was compared experimentally for two different cooling methods of the forced and the natural convection cooling in the heat pipe condenser. During the experiment, the maximum temperature was about 1300K, and different cooling methods were applied to the condenser region to charge the operating temperature. The effective thermal conductivity and the thermal resistance were investigated as a function of heat flux, heat transport length, and operating temperature.

• 한국안전학회지
• /
• 제21권3호
• /
• pp.101-106
• /
• 2006

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. In constructions site, pipe supports are usually used as shores which are consisted of the slab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. Among the accidents and failures that occur during concrete construction, there are many formwork failures which usually happen at the time concrete is being placed. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies free of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KS F 8001. In this study, the strength of pipe support according to age, use frequency and load carrier was predicted using SPSS 12.0. It was known that the strength of pipe support using for 5 years was reduced to 42.8%. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a finn base to prevent formwork collapses.

• 건설안전기술
• /
• 통권38호
• /
• pp.79-87
• /
• 2006

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. In constructions site, pipe supports are usually used as shores which are consisted of the stab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. Among the accidents and failures that occur during concrete construction, there are many formwork failures which usually happen at the time concrete is being placed. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies free of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KSF 8001. In this study, the strength of pipe support according to age, use frequency and load carrier was predicted using SPSS 12.0. It was known that the strength of pipe support using for 5 years was reduced to 42.8%. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a firm base to prevent formwork collapses.

• 한국안전학회지
• /
• 제20권3호
• /
• pp.120-125
• /
• 2005

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. Among the accidents and failures that occur during concrete construction, many are formwork failures which usually happen at the time concrete is being placed. In constructions site, pipe supports are usually used as shores which are consisted of the slab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies fire of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KS F 8001. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a firm base to prevent formwork collapses.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
• /
• pp.129-131
• /
• 1990

When insulating oil is flowed through a pipe, the electrostatic charge in the oil will be increased. Using inflammability oil, an electrostatic phenomena which may cause significantly problems as explosion must be circumvented by some methods. In this paper we made a new electrode which was applied AC field to the flowing oil for reducing electrostatic charge. Before we developed the new method of an electrostatic elimination, the electrification experiment was performed by using the same electrode which was supplied DC voltage to realize electrified conditions. As a result of this study, the effect of the electrostatic elimination could be observed.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1993년도 춘계학술대회 논문집
• /
• pp.72-75
• /
• 1993

The characteristic of streaming electrification and static charge diminution in Cu, Fe and Sus pipes were investigated. The Cu and Fe pipes are charged positively, whereas the Sus pipes are charged negatively. Electrification rate in Cu and Fe pipes increases with increasing a pipe length for no-charged insulating oil. The electrification rate in Cu and Fe pipes abruptly increase with increasing the temperature and flow rate of insulating oil but decrease in Sus pipes. The current flows as a direction of insulating oil in all pipes.

• 한국에너지공학회:학술대회논문집
• /
• 한국태양에너지학회, 한국에너지공학회 1993년도 춘계 공동학술발표회 초록집
• /
• pp.70-78
• /
• 1993

Heat pipes, applied to flat plate solar collectors, have a long and slender configuration with relatively low heat flux on the evaporator. Such a heat pipe has a tendency to build-up a liquid pool at the lower half of evaporator zone, and at this pool occurs such complicated phenomena of evaporation and fluid dynamics as superheat, sudden generation of bubble, its likely explosive growth process and flooding etc. In the present study, we tried to solve those problems by means of adjusting the two principle design parameters, liquid fill charge and wick length, using 4 heat pipes and 3 thermosyphons, with different values of parameter respectively. The corresponding results can be summarized as followings, - The thermal conductance of heat pipes was largely improved by el eliminating wick from adiabatic and condenser zone. - But on evaporator zone wick is inevitable to reduce behavior of the build -up of liquid pool , where arise diverse internal complex phenomena. - The liquid fill charge should have to be increased by 10∼20％ more than the quantity to saturate the wick.