• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문집
• /
• pp.588-592
• /
• 2002

There was the transient vibration on $H_2$ piping system for cooling the generator in a power plant. We found it was resulted from resonance between the natural vibration of the piping system and exciting force from the turbine rotor by measurement and simulation test. We verified it would be changed the mode shape of the piping system by several simulation test for the structural modification of the piping system. Therefore we concluded that the change of natural vibration mode depends on deeply changing effective length of pipe and reducing supports.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1473-1478
• /
• 2003

Scale is formed when hard water is heated or cooled in heat transfer equipments such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. When scale deposits in a heat exchanger surface, it is traditionally called fouling. The objective of the present study is to investigate the formation of fouling in a heat exchanging system. A lab-scale heat exchanging system is built-up to observe and measure the formation of fouling experimentally. Water analyses are conducted to obtain the properties of HAN river water. In the present study a microscopic observation is conducted to visualize the process of scale formation. Hardness of HAN-river water is higher than that of tap water in Seoul.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.48-53
• /
• 2001

This experimental study is to research heat transfer characteristics in copper-water heat pipes with screen wick, the 150 and 200-mesh. Recent advances in the miniaturization and large capacity of electronic devices have had a major impact on the design of electronic equipment. As a result, a high-performance cooling system is needed. Experimental variables are inclination angle, number of layer and temperature of cooling water. The distilled water was used for the working fluid. At a inclination angle $6^{\circ}$, the 200-mesh screen wick 3-layer is shown the best heat transfer performance.

• 동력기계공학회지
• /
• 제14권4호
• /
• pp.5-10
• /
• 2010

This study was investigated the effect on operating characteristics of apparatus according to frosting and defrosting to develop of new defrosting equipment. The results showed as following. Frost was almost removed using the defrosting equipment with roll brush type that defrosting is possible under operating condition. Also, the temperature of compressor inlet, evaporator inlet and outlet showed higher value because of heat transfer resistance of cooling pipe frost comparing with defrosting condition. And the compressor work showed 10% lower and COP was presented 24% higher values than defrosting condition. Therefore, defrosting for cooling coil of refrigeration and low temperature storage was effected on operation and performance characteristics of equipment. This highly effects on real refrigeration apparatus which is operated in year-around.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
• /
• pp.50.1-50.1
• /
• 2009

광학탑재체 열제어 시스템(Cooling Unit)은 광학카메라가 우주환경 하에서 작동시 영상검출기(FPA)에서 발생하는 열을 효과적으로 발열하여 영상검출기의 온도를 최적으로 제어하는 시스템이다. 영상검출기(FPA)의 1회 orbit은 100분이며, 예열기간(Preheating) 최대 10분 동안 147W를 발열하고, 촬영기간(Imaging) 10분 동안 147W를 발열하여 1회 orbit 평균 32.6W를 발열하고, Parasitic heat load 15W를 고려하면 1회 orbit당 평균 총 50W를 발열 한다. 열제어 시스템은 50W를 효과적으로 발열하여 영상검출기의 온도를 $14^{\circ}C{\sim}26^{\circ}C$로 제어한다. 열제어 시스템은 Buffer Mass, Heat Pipe, Radiator로 구성된다. 열제에 시스템의 성능규격은 열주기시험, 열진공하 열전도시험 및 진동시험을 통하여 검증한다. 이 논문에서는 국내 기술로 개발되는 우주용 카메라 열제어 장치의 설계 및 해석, 제작현황 등을 소개하고자 한다.

• 설비공학논문집
• /
• 제11권3호
• /
• pp.339-348
• /
• 1999

A computer model was developed in order to predict the temperature distribution and the performance of the vertical tube-in-tube ground coil heat exchanger. This model has been validated by experimental results conducted by ORNL. The heat exchanger performance with the variation of the length is calculated and compared. As results, the heat exchanger performance is proportional to the length but the performance per unit length decreases. The minimum performance of 70m - PVC heat exchanger during cyclic operation for a week is obtained 20,054kJ/h for cooling operation and 13,915kJ/h for heating operation. And minimum temperature difference is $4.64^{\circ}C$ for cooling operation and $2.64^{\circ}C$ for heating operation. In each case, it is noted that the temperature difference between the pipe and the far-field occurs within 0.8m from the heat exchanger.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 추계 학술발표회
• /
• pp.1689-1692
• /
• 2008

In this research, these days extension of electric power station plant and new building plan is tending to more bigger size and much more cooling water for discharge, therefore submarine structure for discharge has needed various types and the large one. The domestic power plant was applied to once-through CW system structure that pipe line type, immersed PC-box culvert type and submarine headrace tunnel type of discharge structure. It is possible that the future structure type of submarine discharge is expected by a case research of application and plan.

• 한국전산유체공학회지
• /
• 제13권4호
• /
• pp.107-113
• /
• 2008

The present study numerically simulates the flow and heat transfer characteristics of rib-induced secondary flow in a square cooling channel with staggered V-shaped ribs, extruded on both walls. The rib pitch-to-height ratio (p/h) varies from 2.8 to 10 with the rib-height-to-hydraulic diameter ration (h/$D_h$)of 0.07 and the Reynolds number of 50,000. Shear stress transport (SST) turbulence model is used as a turbulence model. Computational results show that complex secondary flow patterns are generated in the channel due to the snaking flow in the streamwise direction for all tested cases. In the range of p/h=5 to 10 the staggered V-shaped rib gives about 3 times higher heat transfer augmentation than the reference smooth pipe with high heat transfer on both front side and the area around the leading edge of the ribs, while the former cases give about 18 times higher streamwise pressure drop than the latter ones. However, for the thermal performances, based on the equal pumping power condition, the case of p/h=2.8 gives the best result among three cases, mainly due to relatively low streamwise pressure drop, although it gives relatively low heat transfer augmentation.

• 설비공학논문집
• /
• 제29권9호
• /
• pp.447-454
• /
• 2017

In this study, local velocity distribution of cooling air in a heat exchanger used in an air compressor for a railway car was measured and heat transfer characteristics of the heat exchanger were analyzed. First, heat transfer coefficient and fin performance of the cooling air side were predicted and was checked if the fin of the heat exchanger was effectively used. Distribution of air flow rate at high temperature side was predicted through pipe network analysis and heat resistance at high temperature and low temperature side were predicted and compared. Spatial distribution of temperature in the interior and surface of the square channel constituting high-temperature side was predicted and appropriateness of the size of the heat exchanger was examined. As a result of the analysis, the present size of the heat exchanger could be reduced and it could be effective to promote heat transfer inside the heat exchanger rather than outside to improve performance of the heat exchanger.

• 한국유체기계학회 논문집
• /
• 제12권5호
• /
• pp.7-12
• /
• 2009

A nuclear fuel test loop(after below, FTL) is installed in the IRI of an irradiation hole in HANARO for testing the neutron irradiation characteristics and thermo hydraulic characteristics of a fuel loaded in a light water power reactor or a heavy water power reactor. There is an in-pile section(IPS) and an out-pile section(OPS) in this test loop. When HANARO is operated normally, the fuel loaded into the IPS has a nuclear reaction heat generated by a neutron irradiation. To remove the generated heat and to maintain the operation conditions of the test fuel, a main cooling water system(MCWS) is installed in the OPS of the FTL. The MCWS is composed of a main cooler, a pressurizer, two circulation pumps, a main heater, an interconnection pipe line and instruments. The interconnection pipeline is a closed loop which is connected to an inlet and an outlet of the IPS respectively. The MCWS is under a cold function test during a start-up period. This paper describes the system flow network analysis results of the flow control of a main cooling water system in the HANARO fuel test loop. It was confirmed through the results that the flow was met the system design requirements.