• Title/Summary/Keyword: Air slit

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An Experimental Study on Air-side Performance of Fin-and-Tube Heat Exchangers with Slit Fin

  • Chang, Keun-Sun;Phan, Thanh-Long
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.627-632
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    • 2006
  • An experimental study is conducted to investigate the effect of the tube row and fin spacing on the air-side heat transfer and friction characteristics of fin-tube heat exchangers with slit fin pattern. A total of twelve samples of fin-tube heat exchangers with the nominal tube diameter of 7 mm, transverse tube pitch of 19 mm and longitudinal tube pitch of 12.5 mm are tested. The thermal fluid measurements are made using a psychometric calorimeter. The raw data are reduced to the desired heat transfer coefficient in terms of j-factor and friction factor of f for various frontal air velocities, fin pitches and number of tube rows.

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An Experimental Study on the Absorption Property of Slit Absorbers with Composite Details

  • Jeong, Dae-Up;Joo, Moon-Ki
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.2E
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    • pp.81-90
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    • 2002
  • Single absorbing materials and Helmholtz resonators have limited absorption characteristics over limited frequency ranges due to their structures and properties. Porous materials are highly absorptive for mid and high frequency ranges, while they have little sound absorption for low frequency sounds. Helmholtz resonators are generally used to absorb sound energy for a specified frequency range. Hence they have limited capability in controlling the overall acoustic properties of a space. Not much has been known about useful finishing materials which have enough rigidity and absorption over broad frequency range, in spite of wide demands from acoustic designers and consultants. The present work measured and analyzed absorption characteristics of a slit absorber by varying surface materials, depths of air gap, dimensions of slat and slit widths. It was found that the narrower the slit width, the larger the absorptions over the wide frequency ranges and the pattern was dependent on the presence of porous material. Narrower slat's width tend to increase the slit absorber's absorption more or less. Absorption coefficients at low frequency ranges were dramatically improved (from 0.23 to 0.56) by increasing air gap when porous materials were present.

Pre-treatment of oily wastewater using a coagulation-DAF process with slit-nozzle (슬릿노즐기반 응집·공기부상공정을 통한 유류폐수 전처리)

  • Choi, Sangki;Kim, Youngmo
    • Journal of Korean Society of Water and Wastewater
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    • v.32 no.6
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    • pp.479-485
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    • 2018
  • Large amounts of oily wastewater discharged from various industrial operations (petroleum refining, machinery industries and chemical industries) cause serious pollution in the aquatic environment. Although dissolved air flotation (DAF) separating oil pollutants using microbubbles represents current practice, bubble size cannot be selectively controlled, and lots of power is required to generate microbubbles. Therefore, to investigate performance of the DAF process, this study examined the distribution of different sizes of microbubbles resulting from changes in physical shear force via modifying shapes of a slit-nozzle without an additional power supply. Three types of slit-nozzles (different angle, shape and length of the slit-nozzle) were used to analyze the distribution of bubble size. At a slit angle of $60^{\circ}$, shear force was 4.29 times higher than a conventional slit, and particle size distribution (PSD) in the range between 2 and $20{\mu}m$ more than doubled. Treatment efficiency of synthetic oily wastewater through the coagulation-DAF process achieved 90% removal of COD by injecting $FeCl_3$ and PACl of 250 mg/L and 100 mg/L, respectively, and the same performance resulted using $FeCl_3$ of 200 mg/L and PACl of 80 mg/L employing a slit-nozzle angle of $60^{\circ}$. This study shows that a coagulation-DAF process using a modified slit-nozzle can improve the pre-treatment of oily wastewater.

Functional and Physical Properties of Weft Knit with Silver Slit Yarn (은 슬릿사 위편성물의 물성 및 기능성)

  • Jeong, Sam-Ho;Park, Jong-Sik;Kwon, Young-Ah
    • Fashion & Textile Research Journal
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    • v.10 no.5
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    • pp.756-761
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    • 2008
  • In this paper, silver slit yarns combined with cotton yarns were used to produce weft knits. The purpose of this study was to investigate the physical properties as well as the functional properties of weft knit with silver slit yarns. The six different weft knit fabrics were made from silver slit yarns varying knit structure and fabric density. One cotton weft knit was also knitted to compare the properties. Weft knits made from silver slit yarns were characterized by excellent antibacterial properties, electric magnetic shielding properties, UV-cut properties, anti-static properties, and air permeability. Although there were significant differences in the physical properties of different knit structure and the fabric density, weft knits with silver slit yarns were seen to have better end use properties and ideal for apparel than the cotton weft knits.

Air-side flow and heat transfer for a two-row lanced finned tube heat exchanger (2열 절개형 핀-관 열교환기의 공기측 유동 및 열전달 특성)

  • Bae, Jin-Hyo;Lee, Jae-Heon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.1
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    • pp.79-92
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    • 1998
  • A numerical study has been performed to obtain the air-side flow and heat transfer characteristics for a two-row lanced finned tube heat exchanger with 7 mm tube outer diameter. The increases of dimensionless local heat flux at the leading edge of slit and bottom surface of the fin were noticed. The temperature of air at downstream of the 2nd row of the lanced fin becomes more uniform than that of the plain fin because the mixing of energy increases by the slit and the side-slit. As the inlet velocity increases, the contribution of the 1st row to heat transfer decreases and that of 2nd row increases.

Coating Characteristics of Photo Resist in a Slit-Coater (Slit-Coater내의 Photo Resist의 코팅 특성)

  • 김장우;정진도;김성근
    • Journal of the Semiconductor & Display Technology
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    • v.3 no.3
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    • pp.41-44
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    • 2004
  • The aim of this study is the confirmation of the coating uniformity affected by the surface tension and wall attachment angle in a slit-coater model. In this work, we use the commercial code (Fluent) to solve the two-phase flow formed with air and photo resist numerically. The results show that the surface tension is the most important factor to determine the coating efficiency in the view of coating uniformity, and the coating uniformity is 2% for our slit-coater model and conditions. To improve the coating uniformity, it is in need of minimization of the sidewall effect of slit-coater.

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Experimental study of air side pressure drop and heat transfer characteristics of wave and wave-slit fin-tube heat exchangers (웨이브 및 웨이브-슬릿 열전달촉진 휜-관 열교환기의 공기측 압력강하 및 열전달 특성에 관한 실험)

  • Yoon, Baek;Gil, Yong-Hyun;Park, Hyun-Yeon;Yoo, Guk-Chul;Kim, Young-Saeng
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.5
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    • pp.589-599
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    • 1998
  • Air side heat transfer and pressure drop for fin-tube heat exchanger with wave and wave-slit fins were measured for various fin spacings and number of tube rows. Outer diameter of the tube including fin collar is 10.07mm, and experiments were done with dry surface condition. Longitudinal and transverse tube spacings of the heat exchangers are 21.65mm and 25mm respectively, and wave depth of the wave fin is 2mm. Experiments were conducted for 1, 2 and 3 rows and 3 different fin spacings, 1.3, 1.5 and 1.7mm. An attempt was made to demonstrate advantage of the enhanced fins over the plane fin by introducing the concept of fan power, Effect of the number of tube rows on heat transfer was discussed in connection with general mechanisms of heat transfer enhancement for fin-tube heat exchanger. Also the effect of hydrophilic coating was investigated. Lastly, correlations for Colburn j-factor and friction factor were developed.

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Evaluation of Air-side Heat Transfer and Friction Characteristics on Design Conditions of Evaporator (증발기의 설계조건에서 공기측 열전달계수 및 압력강하 산출)

  • 김창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.12
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    • pp.1007-1017
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    • 2003
  • An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150∼250 kg/$m^2$s with air flows at velocity ranges from 0.3 m/s to 0.8 m/s.

Evaluation of Air-side Heat Transfer and Friction Characteristics on Design Conditions of Condenser (응축기의 설계조건에서 공기측 열전달계수 및 압력강하 산출)

  • 김창덕;전창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.3
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    • pp.220-229
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    • 2003
  • An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150~250 kg/$m^2$s with air flows at velocity ranges from 0.6 m/s to 1.6 m/s.

A Study on Performance Characteristics of Heat Exchanger for Heat Pump with R410A Refrigerant (R410A 냉매를 사용한 열펌프용 열교환기의 형상에 따른 성능특성 연구)

  • 정규하;박윤철;오상경
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.4
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    • pp.340-348
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    • 2004
  • The air and refrigerant side heat transfer performances are key parameters to improve heat transfer efficiency of the heat exchanger including the fan performance. Design of the fins, treatment of the tube inside, tube diameter and tube array effect heat transfer performance of the heat exchanger. The heat exchanger is used as a condenser at cooling mode and used as an evaporator at heating mode in the heat pump system. The heat pump system uses R410A as the refrigerant. The heat exchangers are consisted with 7 mm diameter tubes with slit-type fins. The study was conducted with variation of arrangement of the refrigerant path and air flow rate and refrigerant pressure drop and heat transfer rate were measured with a code tester. The capacity of the 3 path heat exchanger is more efficient than 2 or 4 path heat exchangers in heating or cooling modes.