• Title, Summary, Keyword: mixing temperature

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An Experimental Study of Temperature Profiles in Mixing Zone of AHU with an Air Mixer (에어믹서가 설치된 공조기 혼합실 내의 온도분포에 관한 실험적 연구)

  • Pak, Kwon-Jong;Lee, Sek-Jun;Jang, Young-Keun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.12
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    • pp.999-1006
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    • 2006
  • A study of temperature profiles in mixing zone of AHU (air handling unit) can contribute greatly to enhance performance of AHU system, so the study on the temperature distribution between RA (return air) and OA (outdoor air) is important to analyze the mixing characteristics in a mixing zone of AHU. Accordingly, the temperature profiles during RA (return air) and OA (outdoor air) supply process into mixing zone of AHU with an air mixer are studied experimentally. The effect of air mixer, OA temperature and RA/OA flow rate are studied in detail. In this study, the results show that the mixing efficiency is all high for installed the air mixer. The more OA temperature increase and OA flow rate decrease, the more mixing efficiency is high.

Thermally-Induced Atomic Mixing at the Interface of Cu and Polyimide

  • Koh, Seok-Keun;Choi, Won-Kook;Song, Seok-Kyun;Kook D. Pae;Jung, Hyung-Jin
    • Journal of the Korean Vacuum Society
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    • v.3 no.3
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    • pp.316-321
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    • 1994
  • Rate of mixing of Cu particles to polyimide substrate at interfaces under different thermal treatments was analyzed by Rutherford Backscattering spectroscopy using 2.0 MeV He+ ions. T he mixing rate was a function of annealing temperature and time and was constant at afioxed temperature. The amount of mixing increased linearly with time and the mixing rate increased with temperature. The activation energy for interface mixing between Cu and polyimide was 2.6 kcal/mol. The X-ray studies showed the Cu(111) plane peak changed with annealing time at fixed temperature. The mixing of Cu to polyimide was explained with segmental motion of PI chain and with interaction between functional group of the chain and metal electron donor. The comparisons were made bewteen the mixing induced by ion irradiation and by thermal treatment. The various factors affecting the interface mixing are discussed.

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Computational Study of the MILD Combustion and Pollutant Emission Characteristics in Jet Flow Field (제트 유동장에서의 마일드 연소 및 오염물질 배출특성에 관한 전산해석 연구)

  • Kim, Yu Jeong;Song, Keum Mi;Oh, Chang Bo
    • Journal of the Korean Society of Combustion
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    • v.17 no.4
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    • pp.60-65
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    • 2012
  • The MILD combustion and pollutant emission characteristics were investigated computationally. The temperature of supplying air-stream and mixing rate (${\Omega}$) of exhaust gas in the air-stream were adjusted to investigate the effects of those parameters on the MILD combustion in jet flow field. The emission indices for NO (EINO) and CO (EICO) were introduced to quantify the amount of those species emitted from the combustion. The high-temperature region disappeared gradually as the mixing rate increased for fixed air-stream temperature. The EINO increased as the air-stream temperature became higher for fixed mixing rate, and the EINO decreased dramatically with increasing the mixing rate for each air-stream temperature condition. The EICO also decreased with increasing the mixing rate and it was nearly independent of air-stream temperature except for near ${\Omega}$ = 0.7. It was found that the CO supplied in the air-stream can be destroyed in the MILD combustion over the certain mixing rate.

Study on Mixing Condition of the Rubber Composite Containing Functionalized S-SBR, Silica and Silane : II. Effect of Mixing Temperature and Time (변성 S-SBR Silica-Silane 고무복합체의 배합조건에 대한 연구 : II. 배합온도와 시간의 영향)

  • Jang, Suk-Hee;Kim, Wook-Soo;Kang, Yong-Gu;Han, Min-Hyun;Chang, Sang-Mok
    • Elastomers and Composites
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    • v.48 no.2
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    • pp.103-113
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    • 2013
  • The properties of the rubber composites containing a silane and silica were evaluated by changing the mixing time and temperature, in order to find the optimum mixing conditions. Characteristics of the compounds were evaluated after mixing at $120^{\circ}C$, $140^{\circ}C$, and $160^{\circ}C$ with various mixing time. With increasing of mixing time, mooney viscosity decreased while the bound rubber contents of the compounds increased. Viscosity rise by increased mixing time was bigger at low temperature and the higher the mixing temperature the faster in the formation of bound rubber. With lower mixing temperature of $120^{\circ}C$, cross-linking rate was almost constant. Dynamic viscoelastic properties and dispersity of the compound showed that dispersion of ingredients and reaction was not sufficient with the mixing time of less than 10min. On the contrary, with high temperature, it was obvious that good dynamic and physical properties could be obtained due to sufficient coupling reaction, however it was thought this high temperature is not optimum because of sensitive cross-linking rate and physical properties and excessive formation of bound rubber. Consequently, it was confirmed that the mixing condition of 10min at $140^{\circ}C$ was optimum for the silane coupling reaction and dispersion of functionalized S-SBR containing silica and silane.

An Experimental Study on Flame and $NO_x$ Emission Characteristics of Front Mixing Premix Combustor (저 $NO_x$ 선단 예혼합 연소기의 화염 및 $NO_x$ 배출 특성 연구)

  • Shin, Myung-Chul;Kim, Se-Won;Mun, Min-Uk
    • Journal of the Korean Society of Combustion
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    • v.11 no.2
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    • pp.22-27
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    • 2006
  • This experimental study has been mainly motivated to obtain generally applicable design correlation for the front mixing premix combustor. The design concept of the front mixing premix combustor is to minimize thermal $NO_x$ and prompt $NO_x$ formation by maintaining low peak flame temperature, and nearly uniform flame temperature through rapid mixing process near the ignition point. The present experimental results clearly indicate that the front mixing premix combustor yields the $NO_x$ level lower than 43 ppm $NO_x$ emissions and the nearly uniform temperature distribution.

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Simulation of the Temperature and Salinity Along $36^{\circ}N$ in the Yellow Sea with a Wave-Current Coupled Model

  • Qiao, Fangli;Ma, Ji-An;Yang, Yong-Zeng;Yuan, Yeli
    • Journal of the korean society of oceanography
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    • v.39 no.1
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    • pp.35-45
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    • 2004
  • Based on the MASNUM wave-current coupled model, the temperature and salinity structures along $36^{\circ}N$ in the Yellow Sea are simulated and compared with observations. Both the position and strength of the simulated thermocline are similar to data analysis. The wave-induced mixing is strongest in winter and plays a key role in the formation of the upper mixed layer in spring and summer. Numerical experiments suggest that in the coastal area, wave-induced mixing and tidal mixing control the vertical structure of temperature and salinity.

A Study on High Cycle Temperature Fluctuation Caused by Thermal Striping in a Mixing Tee Pipe (혼합배관 내의 열 경계층 이동으로 인한 고주기 온도요동에 관한 연구)

  • Kim, Seoug-B.;Park, Jong-H.
    • The KSFM Journal of Fluid Machinery
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    • v.10 no.5
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    • pp.9-19
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    • 2007
  • Fluid temperature fluctuations in a mixing tee pipe were numerically analyzed by LES model in order to clarify internal turbulent flows and to develope an evaluation method for high-cycle thermal fatigue. Hot and cold water with an temperature difference $40^{\circ}C$ were supplied to the mixing tee. Fluid temperature fluctuations in a mixing tee pipe is analysed by using the computational fluid dynamics code, FLUENT, Temperature fluctuations of the fluid and pipe wall measured as the velocity ratio of the flow in the branch pipe to that in the main pipe was varied from 0.05 to 5.0. The power spectrum method was used to evaluate the heat transfer coefficient. The fluid temperature characteristics were dependent on the velocity ratio, rather than the absolute value of the flow velocity. Large fluid temperature fluctuations were occurred near the mixing tee, and the fluctuation temperature frequency was random. The ratios of the measured heat transfer coefficient to that evaluated by Dittus-Boelter's empirical equation were independent of the velocity ratio, The multiplier ratios were about from 4 to 6.

Flame characteristics of direct fired burner in fuel-air mixing conditions (열처리로 직화버너에서 연료-공기 혼합에 따른 화염 영향)

  • Lee, Cheolwoo;Kim, Youngho;Kim, Insu;Hong, Junggoo
    • 한국연소학회:학술대회논문집
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    • pp.285-288
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    • 2014
  • Experiments have been performed for the burners used in the non-oxidizing direct fired furnaces for the cold rolled plate to investigate the effect of fuel/air mixing patterns of the burner nozzle on flame shape, temperature and combustion gas concentration. CFD simulation has also been performed to investigate the mixing state of air-fuel for a nozzle mixing burner and a partially pre-mixing burner. A partially pre-mixing burner showed that flame temperature increased up to $26^{\circ}C$ on average compared than that of the nozzle mixing. It also showed that the mixing distance is important at the partially pre-mixing burner. Test results for a partially pre-mixing burner showed that the residual oxygen concentration and the volume ratio of $CO/CO_2$ of the flame were applicable to be used in field furnaces.

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CFD ANALYSIS FOR THERMAL MIXING CHARACTERISTICS OF A FLOW MIXING HEADER ASSEMBLY OF SMART (SMART 유동혼합헤더집합체 열혼합 특성 해석)

  • Kim, Y.I.;Bae, Y.M.;Chung, Y.J.;Kim, K.K.
    • Journal of computational fluids engineering
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    • v.20 no.1
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    • pp.84-91
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    • 2015
  • SMART adopts, very unique facility, an FMHA to enhance the thermal and flow mixing capability in abnormal conditions of some steam generators or reactor coolant pumps. The FMHA is important for enhancing thermal mixing of the core inlet flow during a transient and even during accidents, and thus it is essential that the thermal mixing characteristics of flow of the FMHA be understood. Investigations for the mixing characteristics of the FMHA had been performed by using experimental and CFD methods in KAERI. In this study, the temperature distribution at the core inlet region is investigated for several abnormal conditions of steam generators using the commercial code, FLUENT 12. Simulations are carried out with two kinds of FMHA shapes, different mesh resolutions, turbulence models, and steam generator conditions. The CFD results show that the temperature deviation at the core inlet reduces greatly for all turbulence models and steam generator conditions tested here, and the effect of mesh refinement on the temperature distribution at the core inlet is negligible. Even though the uniformity of FMHA outlet hole flow increases the thermal mixing, the temperature deviation at the core inlet is within an acceptable range. We numerically confirmed that the FMHA applied in SMART has an excellent mixing capability and all simulation cases tested here satisfies the design requirement for FMHA thermal mixing capability.

Numerical Simulation of Thermal Fluctuation of Hot and Cold Fluids Mixing in a Tee Junction

  • Gao, Kai;Lu, Tao
    • International Journal of Advanced Culture Technology
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    • v.3 no.2
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    • pp.171-178
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    • 2015
  • In this work, mixing processes of hot and cold fluids of three different jet types are predicted by large-eddy simulation (LES) on FLUENT platform. Temperature at different positions of internal wall and mixing conditions of T-junctions at different times are obtained, then the simulated normalized mean and root-mean square (RMS) temperature, temperature contour and velocity vector of every case are compared. The results indicate that, the mixing regions in the tee junction is related to the jet type, and temperature fluctuations on the pipe wall in the type of the deflecting jet is the least.