• Title/Summary/Keyword: Pipe Cooling

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Preliminary Analysis on Design Parameters and Application Effects of Surface Water Heat Exchanger (SWHE) (지표수 열교환기 설계 변수와 적용 효과에 대한 선행 분석)

  • Sohn, Byonghu
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.12 no.3
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    • pp.24-32
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    • 2016
  • Commercial buildings and institutions are generally cooling-dominated and therefore reject more heat to a borehole ground heat exchanger (BHE) than they extract over the annual cycle. Shallow ponds can provide a cost-effective means to balance the thermal loads to the ground and to reduce the length of BHE. This paper presents the analysis results of the impact of design parameters on the length of SWHE pipe and its application effect on geothermal heat pump (GHP) system using BHE. In order to analysis, we applied ${\varepsilon}-NTU$ method on designing the length of SWHE pipe. Analysis results show that the required pipe length of SWHE was decreased with the increase of approach temperature difference and with the decrease of pipe wall thickness. In addition, when the SWHE was applied to the GHP system, the temperature of BHE was more stable than that of standalone BHE system.

Heat transfer enhancement of nanofluids in a pulsating heat pipe for heat dissipation of LED lighting

  • Kim, Hyoung-Tak;Bang, Kwang-Hyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.10
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    • pp.1200-1205
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    • 2014
  • The effect of nanofluids on the heat transfer performance of a pulsating heat pipe has been experimentally investigated. Water-based diamond nanofluid and aluminium oxide ($Al_2O_3$) nanofluid were tested in the concentration range of 0.5-5%. The pulsating heat pipe was constructed using clear Pyrex tubes of 1.85 mm in inner diameter in order to visualize the pulsating action. The total number of turns was eight each for heated and cooled parts. The supply temperatures of heating water and cooling water were fixed at $80^{\circ}C$ and $25^{\circ}C$ respectively. The liquid charging ratio of the nanofluid was 50-70%. The test results showed that the case of 5% concentration of diamond nanofluid showed 18% increase in heat transfer rate compared to pure water. The case of 0.5% concentration of $Al_2O_3$ nanofluid showed 24% increase in heat transfer rate compared to pure water. But the increase of $Al_2O_3$ nanofluid concentration up to 3% did not show further enhancement in heat transfer. It is also observed that the deposited nanoparticles on the tube wall played a major role in enhanced evaporation of working fluid and this could be the reason for the enhancement of heat transfer by a nanofluid, not the enhanced thermal conductivity of the nanofluid.

Study on Performance Evaluation of Oscillating Heat Pipe Heat Exchanger for Low Temperature Waste Heat Recovery (저온 폐열 회수용 진동형 히트 파이프 열교환기의 성능 평가에 관한 연구)

  • 안영태;이욱현;김정훈;김종수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.5
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    • pp.368-376
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    • 2001
  • Performance of heat exchanger was evaluated to heat exchanger using oscillating heat pipe for waste heat recovery of low temperature. Oscillating heat pipe used in this study was formed to the closed loop of serpentine shapes using copper tubes. Heat exchanger was formed to shell and tube type and composed of low finned tube. R-22 and R-141b were used to the working fluids of tube side and their charging ratio was 40%. And, water was used to the working fluid of shell side. As the experimental parameters, the inlet temperature difference of heating and cooling part of secondary fluid and the mass velocity of secondary fluid were used. The mass velocity of secondary fluid was changed from 90 kg/$m^2s\; to\;190 kg/m^2$s from the experimental results, heat recovery rate was linearly increased to the increment of the mass velocity of secondary fluid and the inlet temperature difference of secondary fluid. Finally, the performance of heat exchanger was evaluated by using $\varepsilon$-NTU method. It was found that NTU was about 1.5 when effectiveness was decided to 80%.

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An Experimental Study on the Heat Transfer Characteristics of a High-temperature Sodium Heat Pipe Depending on the Thermal Transport Conditions (고온 나트륨 히트파이프에서 열이송 조건에 따른 열전달 특성에 대한 실험 연구)

  • Park, C.M.;Boo, J.H.;Kim, J.S.
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2340-2345
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    • 2008
  • Cylindrical stainless-steel/sodium heat pipe for a high-temperature application was manufactured and tested for transient and steady-state operations. Two layers of Stainless-steel screen mesh wick was inserted as a capillary structure. The outer diameter of the heat pipe was 12.7 mm and the total length was 250 mm. As thermal transport conditions, the effective transport length, the heat flux, the tilt angle and the operating temperature were varied. The heat was supplied by an electric furnace up to 1 kW and the cooling was performed by forced convection of air. The effective thermal conductivity and the thermal resistance were investigated as a function of heat flux, heat transport length, and vapor temperature. Typical range of the total thermal resistance was as low as $0.036^{\circ}C/W$ at $175.8\;kW/m^2$ of heat flux and $700^{\circ}C$ of operating temperature.

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Heat transfer characteristics of the heat pipe using simplified heat transfer model (단순 열전달 모델을 이용한 히트파이프의 열전달 성능특성에 관한 연구)

  • Seo, Jae-Hyeong;Bang, Yu-Ma;Seo, Lee-Soo;Lee, Moo-Yeon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.1
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    • pp.15-20
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    • 2015
  • The objective of this study was to examine numerically the heat transfer and flow characteristics of the heat pipe with a wick using the simplified heat transfer model to enhance the cooling effects of high heat flux devices and minimizing the energy consumption for electric vehicles. The heat pipe with a wick was analyzed using commercial software with COMSOL and water was used as the working fluid. The velocity and temperature characteristics of the heat pipe were simulated numerically along the heat pipe and the local and average Nusselt numbers were calculated. As a result, the driving force occurred because of the temperature difference between the hot side and the cold side. The heat transfer of the heat pipe occurred from the hot side to the cold side and increased toward the center position. In addition, the average Nusselt numbers were 1.88 for the hot side and 0.1 for the cold side, and the maximum Nusselt number was 4.47 for the hot side and 0.7 for the cold side.

Development of Thermal-Hydro Pipe Element for Ground Heat Exchange System (지중 열교환 시스템을 위한 열-수리 파이프 요소의 개발)

  • Shin, Ho-Sung;Lee, Seung-Rae
    • Journal of the Korean Geotechnical Society
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    • v.29 no.8
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    • pp.65-73
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    • 2013
  • Ground-coupled heat pump system has attracted attention as a promising renewable energy technology due to its improving energy efficiency and eco-friendly mechanism for space cooling and heating. Pipes buried in the ground play a role of direct thermal interaction between circulating fluid inside the pipe and surrounding soils in the geothermal exchange system. However, both complexities of turbulent flow coupling thermal-hydraulic phenomena and very long aspect ratio of the pipe make it difficult to model the heat exchange system directly. Energy balance for fluid flow inside the pipe was derived to model thermal-hydraulic phenomena, and one-dimensional pipe element was proposed through Galerkin formation and time integration of the equation. Developed element is combined to pre-developed FEM code for THM phenomena in porous media. Numerical results of Thermal Response Test showed that line-source model overestimates equivalent thermal conductivity of surrounding soils due to thermal interaction between adjacent pipes and finite length of the pipe. Thus, inverse analysis for the TRT simulation was conducted to present optimal transformation matrix with utmost convergence.

Study on the Effects of Flows on the Acceleration of the Grooving Corrosion in the ERW Pipe (ERW강관에서 홈부식의 가속화에 미치는 유동의 영향에 관한 연구)

  • Kim, Jae-Seong;Kim, Yong;Lee, Bo-Young
    • Journal of Welding and Joining
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    • v.26 no.4
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    • pp.85-91
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    • 2008
  • The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.

Influence of NCG Charging Mass on the Heat Transport Capacity of Variable Conductance Heat Pipe (불응축가스량이 가변전열 히트파이프의 열수송 특성에 미치는 영향)

  • Suh Jeong-Se;Park Young-Sik;Chung Kyung-Taek
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.4
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    • pp.320-327
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    • 2006
  • Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 mm length and 12.7 mm outer diameter tube of copper, water (4.8 g) is used as working fluid and nitrogen as non-condensible gas (NCG). Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Analysis values and experimental data of wall temperature distribution along axial length are presented for heat transport capacity, condenser cooling water temperature change, degrees of an inclination angle and operating temperature. These analysis and experiment give the follow findings: For the same charging mass of working fluid, the operating temperature of heat pipe becomes to be high with the increasing of charging mass of NCG. When the heat flux at the evaporator section increases, the vapor pressure in the pipe rises and consequently compresses the NCG to the condenser end part and increases the active length of the condenser. From previous process, it is found out we can control the operating temperature effectively and also the analysis and experimental results are relatively coincided well.

Long-term Ring Deflection Prediction of GFRP Pipe in Cooling Water Intake for the Nuclear Power Plant (원전 냉각수 취수용 GFRP관의 장기관변형 예측)

  • Kim, Sun-Hee;Park, Joon-Seok;Yoon, Soon-Jong
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.3 no.3
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    • pp.1-8
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    • 2012
  • Recently, underground pipes are utilized in various fields of applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. Most of pipes are installed for long-term purposes and they should be safely installed in consideration of installation conditions because there are unexpected various terrestrial loading conditions. In this paper, we present the result of investigation pertaining to the structural behavior of glass fiber reinforced thermosetting polymer plastic (GFRP) flexible pipes buried underground. The mechanical properties of the GFRP flexible pipes produced in the domestic manufacturer are determined and the results are reported in this paper. In addition, ring deflection is measured by the field tests and the finite element analysis (FEA) is also conducted to simulate the structural behavior of GFRP pipes buried underground. From the field test results, we predicted long-term, up to 50 years, ring deflection of GFRP pipes buried underground based on the method suggested by the existing literature. It was found that the GFRP flexible pipe to be used for cooling water intake system in the nuclear power plant is appropriate because 5% ring deflection limitation for 50 years could be satisfied.

Performance Analysis of Water-Water Heat Pump System of 100 kW Scale for Cooling Agricultural Facilities

  • Kang, Youn Ku;Ryou, Young Sun;Jang, Jae Kyung;Kim, Young Hwa;Kim, Jong Goo;Kang, Geum Chun
    • Journal of Biosystems Engineering
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    • v.39 no.1
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    • pp.34-38
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    • 2014
  • Purpose: In this study, the performance of cooling system with the water-water heat pump system of 100kW scale made for cooling agricultural facilities, especially for horticultural facilities, was analyzed. It was intended to suggest performance criteria and performance improvement for the effective cooling system. Methods: The measuring instruments consisted of two flow meters, a power meter and thermocouples. An ultrasonic and a magnetic flow meter measured the flow rate of the water, which was equivalent to heat transfer fluid. The power meter measured electric power in kW consumed by the heat pump system. T-type thermocouples measured the temperature of each part of the heat pump system. All of measuring instruments were connected to the recorder to store all the data. Results: When the water temperature supplied into the evaporator of the heat pump system was over $20^{\circ}C$, the cooling Coefficient Of Performance(COP) of the system was higher than 3.0. As the water temperature supplied into the evaporator, gradually, lowered, the cooling COP, also, decreased, linearly. Especially, when the water temperature supplied into the evaporator was lower than $15^{\circ}C$, the cooling COP was lower below 2.5. Conclusions: In order to maintain the cooling COP higher than 3.0, we suggest that the water temperature supplied into evaporator from the thermal storage tank should be maintained above $20^{\circ}C$. Also, stratification in the thermal storage tank should be formed well and the circulating pumps and the pipe lines should be arranged in order for the relative low-temperature water to be stored in the lower part of the thermal storage tank.