• 한국가스학회지
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• 제22권1호
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• pp.45-52
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• 2018

이 논문에서는 도시가스 배관 중 교량에 설치된 배관 398개소에 대해 현황을 조사하고, 배관을 설치연도별, 길이별, 원격차단장치 설치여부 등 특성별로 분류하여 분석하였다. 분석결과 20년 이상 장기사용배관이 43.0%를 차지하고 있었고, 원격차단장치 미설치 교량배관은 89.4%에 달하는 등 드러난 현상에 대한 안전관리 방안을 제시하였다. 또한 조사된 교량설치 배관 중 76개소를 선정한 후 응력해석 전용프로그램인 CAESAR-II를 이용하여 응력특성을 연구하고, 교량배관 중 루프관을 설치할 경우 루프관의 위치 및 크기가 배관의 합성응력에 미치는 영향을 분석하였다. 본 연구의 결과를 통해 교량 배관의 설치, 검사 및 진단 기준 개선 등에 활용하여 교량설치 배관에 대한 안전성 향상에 도움이 될 수 있을 것으로 판단한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1026-1030
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• 2007

A linear compressor used in a refrigerator has higher energy efficiency than a reciprocating compressor. But its vibration level is still severe than others. The vibration level of linear compressor at the frequency of 60Hz is dominant since it is the exciting frequency of a motor. Experimental approach to reduce the vibration needs much effort and long period. In this paper, simulation tool to predict the vibration of the shell of the linear compressor was developed. The piston, body and shell are assumed to be rigid, while the loop pipe is flexible. The results by the developed tool showed good agreements with those by experiments.

• 동력기계공학회지
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• 제14권3호
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• pp.19-24
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• 2010

The purpose of this study is to develop a snow melting system using the pulsating heat pipe(PHP). The experimental apparatus is consisted of a PHP, a concrete structure, a constant water thermostatic bath and a flowmeter. The experiment was performed at the outdoor air temperature of $-8^{\circ}C$ and inlet temperature of hot water of $75^{\circ}C$. PHP is the closed and non-loop type heat exchanger which is charging R-410A as an operating fluid. As experimental results, the temperature profile of vertical and horizontal orientation of concrete structure was measured with operating time. The heat flux of the snow melting was required more than 300 $W/m^2$. We confirmed that the snow melting system using the PHP was useful for anti-freezing road.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.328-332
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• 2011

The conclusion is derived from the arranged results and using a simulation by determining the shape of an optimum heat pump which is appropriate for small scale houses. It is concluded as 3 meters long for the laying depth of underground piping of the horizontal type geothermal heat pump system in regard to the 5 RT capacity standard that is suitable for a small scale house. The shape of the horizontal type geothermal heat pump system for a small scale house is theThree pipe shape whose trench length is short and pipe length laid in a trench is short. It is 9 for the number of laying pipes that is most appropriate to system.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권2호
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• pp.73-81
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• 2003

The performance of heat exchanger using oscillating heat pipe (OHP) for low temperature waste heat recovery was evaluated. OHP used in this study was made from low finned copper tubes connected by many turns to become the closed loop of serpentine structure. The OHP heat exchanger was formed into shell and tube type. R-22 and R-141b were used as the working fluids of OHP with a fill ratio of 40 vol.%. Water was used as the working fluid of shell side. As the experimental parameters, the inlet temperature difference between heating and cooling water and the mass velocity of water were changed. The mass velocity of water was changed from 30 kg/$m^2$s to 92 kg/$m^2$s. The experimental results showed that the heat recovery rate linearly increased as the mass velocity and the inlet temperature difference of water increased. Finally, the performance of OHP heat exchanger was evaluated by $\varepsilon$-NTU method. It was found that the effectiveness would be 80% if NTU were about 1.5.

• Corrosion Science and Technology
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• 제20권6호
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• pp.403-411
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• 2021

In this study, the reliability of a commercial ER-type corrosion sensor was evaluated under an accelerated corrosion environment to verify its suitability for application in monitoring of ship's seawater piping system. A closed-loop pump piping testbed was designed and constructed to compare the wall thickness reduction of the pipe and the response from the sensor. The sensor was attached inside the pipe near the outlet of the pump that was exposed to a 3.5% NaCl solution with or without copper accelerated acetic acid (CASS). The results demonstrated that the presence of CASS significantly increased the corrosivity of the solution as well as the thickness reduction of the pipe, as expected. On the other hand, the corrosion products formed by the solution with CASS were thicker compared with those without CASS. The sensor response to temperature variation was found to be a clear linear relationship for the solution without CASS but there was a non-linear relationship where CASS was present.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.36-39
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• 2006

To evaluate the effect of groundwater flow on the outlet temperature of a geothermal heat pump, 3 dimensional numerical simulations are performed considering both groundwater flow and pipe flow in the U-tube using TOUGHS, The present study involved the following 4 simulation cases (1) no groundwater flow, (2) slow groundwater flow (hydraulic conductivity: $1.0{\times}10^{-9}m/s)$, (3) fast groundwater flow (hydraulic conductivity, $1.0{\times}10^{-7}m/s$), and (4) groundwater flow varying with the depth (hydraulic conductivity: $1.0{\times}10^{-7}-1.0{\times}10^{-10}m/s$). The effect of groundwater flow on the outlet temperature is significant where hydraulic conductivity of aquifer is $1.0{\times}10^{-7}m/s$. Where hydraulic conductivity of aquifer is $1.0{\times}10^{-10}m/s$, however, that effect is negligible.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.167.1-167.1
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• 2010

본 연구에서는 수직 밀폐형 지중열교환기 뒤채움용 그라우트의 종류와 첨가재 종류, 지중열교환기 파이프 단면에 따른 지중열교환기의 성능을 비교 평가하기 위해 현장 시험 시공과 현장 열응답 시험을 수행하였다. 뒤채움용 그라우트재는 벤토나이트와 시멘트를 사용하였으며 첨가제로는 천연규사와 흑연을 적용하였다. 지중열교환기 파이프 단면은 일반적으로 시공되는 U-loop 파이프 단면과 파이프 사이의 열간섭 효과를 최소화 한 3공형 파이프 단면이 적용되었다. 시멘트-천연규사 그라우트재가 벤토나이트-천연규사 그라우트재 보다 큰 지중 유효열전도도를 보이고 흑연을 첨가한 그라우트는 시멘트와 벤토나이트 모두에서 천연규사만 첨가하였을 때 보다 지중 유효열전도도가 높게 나타났다. 3공형 파이프 단면의 경우 단면에 따른 영향을 비교하기 위해 그라우트는 시멘트-천연규사와 벤토나이트-천연규사를 사용하였으며 지중 유효열전도도 측정결과 각각 3.64 W/mK, 3.40 W/mK으로 일반 U-loop 파이프 단면을 사용하였을 때 보다 높게 나타났다.

• 동력기계공학회지
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• 제17권2호
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• pp.70-77
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• 2013

An experimental study was carried out to understand the heat transfer performance of a miniature loop heat pipes using water-based copper nanoparticles suspensions as the working fluid. The suspensions consisted of deionized water and copper nanoparticles with an average diameter of 80 nm. Effects of the cupper mass concentration and the operation pressure on the average evaporation and condensation heat transfer coefficients, the critical heat flux and the total heat resistance of the mLHPs were investigated and discussed. The pressure frequency also depends upon the evaporator temperature which has been maintained from $60^{\circ}C$ to $90^{\circ}C$. The Investigation shows 60% filling ratio gives the highest inside pressure magnitude of highest number pressure frequency at any of setting of evaporator temperature and 5wt% results the lowest heat flow resistance.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1475-1483
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• 2004

Loop thermosyphon(LTS) has many good characteristics such as low thermal resistance, no power consumption, noiseless operation and small size. To investigate the overall performance of LTS, we have performed various experiments varying three parameters: input power of the heater, working fluid(water, ethanol, FC3283) and filling ratio of the working fluid. At a combination of these parameters, temperature measurements are made at many locations of the LTS. The temperature difference between the evaporator and the condenser is used to obtain the thermal resistance. In addition, flow visualization using a high speed camera is carried out. The thermal resistance is not constant. It is lower at higher input power, which is one of the distinct merits of LTS. Flow instabilities are frequently observed when changing the working fluid, the input power and the filling ratio. The results show that the LTS can be readily put into practical use. Future practical application in electronic cooling is recommended.