• 제목/요약/키워드: critical heat flux

검색결과 296건 처리시간 0.026초

혼합 작동 유체를 이용한 진동 세관형 히트 파이프의 압력 진동과 열전달 특성에 관한 연구 (The Study on Pressure Oscillation and Heat Transfer Characteristics of Oscillating Capillary Tube Heat Pipe Using Mixed Working Fluid)

  • 정현석;김정훈;김주원;김종수
    • 대한기계학회논문집B
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    • 제26권2호
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    • pp.318-327
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    • 2002

  • In this paper, heat transfer and pressure oscillation characteristics on oscillating capillary tube heat pipe(OCHP) according to input heat flux, mixture ratio of working fluid and inclination angle were investigated and were compared single working fluid(R-142b) with binary mixture working fluid(R-142b-Ethano1). OCHP was made to serpentine structure of loop type with 10 turns by drilling the channels of length 220mm, width 1.5mm, and depth 1.5mm on the surface of brass plate. In this study, R-l42b and R-l42b-Ethanol were used as working fluids, the charging ratio of working fluids was 40(vol.%), the input heat flux to evaporating section was changed from 0.3W/㎠ to 1.8W/㎠, and mixture ratio of working fluid was R(100%), R(95%)-E(5%), R(90%)-E(10%), and R(85%)-E(15%). From the experimental results, it was found that the effective thermal conductivity of single working fluid was better than that of binary mixture working fluid. But, in case of binary mixture working fluid, critical heat flux was higher than that of single working fluid. And, the higher the mixture ratios of working fluid, the lower heat transfer performance. In case of pressure oscillation, as the inclination angle was lower, pressure wave was more irregular. These phenomena were more serious when the working fluid was binary mixture. Besides, when mixture ratio was higher, saturated pressure was increased, more irregular wave was observed and the mean amplitude was increased. For the same input heat flux, inclination angle and charging ratio, when pressure oscillation has sinusoidal wave, mean amplitude was small, and saturated pressure was low value, the heat transfer was excellent.

  • https://doi.org/10.3795/KSME-B.2002.26.2.318 인용 PDF KSCI

EFFECT OF SOLUBLE ADDITIVES, BORIC ACID (H3BO3) AND SALT (NaCl), IN POOL BOILING HEAT TRANSFER

  • Kwark, Sang-M.;Amaya, Miguel;Moon, Hye-Jin;You, Seung-M.
    • Nuclear Engineering and Technology
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    • 제43권3호
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    • pp.195-204
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    • 2011

  • The effects on pool boiling heat transfer of aqueous solutions of boric acid ($H_3BO_3$) and sodium chloride (NaCl) as working fluids have been studied. Borated and NaCl water were prepared by dissolving 0.5~5% volume concentration of boric acid and NaCl in distilled-deionized water. The pool boiling tests were conducted using $1{\times}1\;cm^2$ flat heaters at 1 atm. The critical heat flux (CHF) dramatically increased compared to boiling pure water. At the end of boiling tests it was observed that particles of boric acid and NaCl had deposited and formed a coating on the heater surface. The CHF enhancement and surface modification during boiling tests were very similar to those obtained from boiling with nanofluids. Additional experiments were carried out to investigate the reliability of the additives deposition in pure water. The boric acid and NaCl coatings disappeared after repeated boiling tests on the same surface due to the soluble nature of the coatings, thus CHF enhancement no longer existed. These results demonstrate that not only insoluble nanoparticles but also soluble salts can be deposited during boiling process and the deposited layer is solely responsible for significant CHF enhancement.

  • https://doi.org/10.5516/NET.2011.43.3.195 인용 PDF KSCI

Superconductivity for HTS GdBCO CC with heat treatment

  • You, Jong Su;Yang, Jeong Hun;Song, Kyu Jeong
    • 한국초전도ㆍ저온공학회논문지
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    • 제23권1호
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    • pp.12-16
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    • 2021

  • The magnetic properties of heat treated O-series high temperature superconducting (HTS) GdBCO coated conductor (CC) tapes which were formed of Ag/GdBCO/Buffer-layers/Stainless Steel (SS), were investigated by employing a Quantum Design PPMS-14. Using a modified Bean model, the critical current density Jc values have been estimated from the 𝚫mirr(H) data, which are obtained by measuring the magnetic moment m(H) loops. For a range of intermediate fields, which are interacting or collective flux pinning area, the magnetic flux behaviors were investigated from the relationship Jc ∝ H-β. In addition, the changes of irreversibility magnetic field Hirr line of heat-treated O-series HTS GdBCO CC tapes were analyzed, according as the annealing temperature under oxygen flowing increases. Both weak and strong break-downs were found by examining the changes of irreversibility magnetic field Hirr lines.

  • https://doi.org/10.9714/psac.2021.23.1.012 인용 PDF KSCI