• Title/Summary/Keyword: frosting

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Modeling for Prediction of Frost Formation Phenomena on a Cold Plate (냉각 평판에서 착상 현상 예측을 위한 모델링)

  • Yang, Dong-Keun;Kim, Jung-Soo;Lee, Kwan-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.6
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    • pp.665-671
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    • 2004
  • A mathematical model is presented to predict the frost properties and heat and mass transfer within the frost layer formed on a cold plate. The model consists of the laminar flow equations for air-side and the empirical correlation of local frost density. The correlation of local frost density used in this study is obtained from various experimental conditions by considering frosting parameters. The numerical results are compared with experimental data to validate the model, and agree well with experimental data within a maximum error of 9%.

HEATING PERFORMANCE OF AIR SOURCE HEAT PUMP WITH HEAT REGENERATIVE DEVICE USING FIBER BELT

  • Ryou, Y.S.;Chang, J.T.;Kim, Y.J.;Kang, G.C.;Yun, J.H.;Lee, K.J.
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • 2000.11c
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    • pp.647-653
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    • 2000
  • In this research the heat regenerative technology was employed to eliminate frosting on evaporator coil and improve COP of the heat pump system. This heat regenerative device(HRD) has very simple structure consisting a geared motor and a porous fiber belt passing through alternatively between cold and warm air duct. The laboratory test showed that the heat pump system with HRD yielded an impressive COP higher than 3.5 at the outside air temperature of $-7^{circ}C$ in heating mode.

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Numerical Model for the Analysis of Frosting Behavior (착상 거동 해석을 위한 수치적 모텔)

  • Lee, Kwan-Soo;Yang, Dong-Keun;Jhee, Sung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.3
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    • pp.261-267
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    • 2002
  • The integral boundary layer equation for the air side and the diffusion equation for the frost layer are numerically analyzed in order to predict the behavior of frost layer growth. The thickness and density of the frost layer obtained from the present study agree well with those of previous numerical results and experimental data with a maximum error of 13%. The characteristics of heat and mass transfer within the frost layer and the frost layer growth along the flow direction are investigated by performing numerical analysis. The effects of operating conditions on the frost layer growth are also examined.

Effect of Frost and Defrost on the Operating Characteristics of Refrigeration System (착상과 제상이 냉동장치의 운전특성에 미치는 영향)

  • Kim, J.D.
    • Journal of Power System Engineering
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    • v.14 no.4
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    • pp.5-10
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    • 2010
  • This study was investigated the effect on operating characteristics of apparatus according to frosting and defrosting to develop of new defrosting equipment. The results showed as following. Frost was almost removed using the defrosting equipment with roll brush type that defrosting is possible under operating condition. Also, the temperature of compressor inlet, evaporator inlet and outlet showed higher value because of heat transfer resistance of cooling pipe frost comparing with defrosting condition. And the compressor work showed 10% lower and COP was presented 24% higher values than defrosting condition. Therefore, defrosting for cooling coil of refrigeration and low temperature storage was effected on operation and performance characteristics of equipment. This highly effects on real refrigeration apparatus which is operated in year-around.

A Study on the Frosting Phenomena of Abrasive Waterjet Microcutting for Multi-Layered Materials (연마제 워터젯을 이용한 복합재 미세가공의 백화현상에 대한 연구)

  • Park, Kang-Su;Bahk, Yeon-Kyoung;Go, Jeung-Sang;Shin, Bo-Sung
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.5
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    • pp.183-190
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    • 2007
  • It is well known that abrasive waterjet(AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain the better cutting quality of various materials such as metals, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, AWJ device still has some problems to obtain the high quality of thin workpiece. In this paper, we investigated the optimal microcutting conditions of AWJ, such as maximum pressure, cutting speed and standoff distance of thin multi-layered materials. The experimental results show that AWJ has possibilities and potential to apply to the microcutting of thin multi-layered materials for IT industrial applications.

Bioinspired Nanoengineering of Multifunctional Superhydrophobic Surfaces

  • Choi, Chang-Hwan
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.11a
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    • pp.102-133
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    • 2015
  • Nature, such as plants, insects, and marine animals, uses micro/nano-textured surfaces in their components (e.g., leaves, wings, eyes, legs, and skins) for multiple purposes, such as water-repellency, anti-adhesiveness, and self-cleanness. Such multifunctional surface properties are attributed to three-dimensional surface structures with modulated surface wettability. Especially, hydrophobic surface structures create a composite interface with liquid by retaining air between the structures, minimizing the contact area with liquid. Such non-wetting surface property, so-called superhydrophobicity, can offer numerous application potentials, such as hydrodynamic drag reduction, anti-biofouling, anti-corrosion, anti-fogging, anti-frosting, and anti-icing. Over the last couple of decades, we have witnessed a significant advancement in the understanding of surface superhydrophobicity as well as the design, fabrication, and applications of superhydrophobic coatings/surfaces/materials. In this talk, the designs, fabrications, and applications of superhydrophobic surfaces for multifunctionalities will be presented, including hydrodynamic friction reduction, anti-biofouling, anti-corrosion, and anti-icing.

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The Frost and Defrost Performances of Fin-and-Tube Exchangers with Different Surface Characteristics (표면특성이 다른 두 핀-관 열교환기의 착상 및 제상 성능)

  • 신종민;최봉준
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.6
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    • pp.525-531
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    • 2002
  • The effects of different surface hydrophilicity on frosting and defrosting characteristic were experimentally investigated. Mass of frost and water hold-up was measured. Results showed that no significant difference in the frost mass was found between the two different surfaces while the water hold-up of heat exchanger court be reduced by the enhancement of surface hydrophilicity. Also, the defrosting efficiency m hydrophilic surface was improved by 76%. It was expected that hydrophilic heat exchanger could provide the improvements in both thermal-hydraulic performances and system reliability during frost/defrost operating in refrigeration systems.

An Experimental Study on the Frost Prevention using Micro Liquid Film of an Antifreeze Solution

  • Chang Young-Soo;Yun Won-Nam
    • International Journal of Air-Conditioning and Refrigeration
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    • v.14 no.2
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    • pp.66-75
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    • 2006
  • The effect of antifreeze solution liquid film on the frost prevention is experimentally investigated. It is desirable that the antifreeze solution spreads widely on the heat exchanger surface forming thin liquid film to prevent frost nucleation while having small thermal resistance across the film. A porous layer coating technique is adopted to improve the wettability of the antifreeze solution on a parallel plate heat exchanger. The antifreeze solution spreads widely on the heat exchanger surface with $100{\mu}m$ thickness by the capillary force resulted from the porous structure. It is observed that the antifreeze solution liquid film prevents a parallel plate heat exchanger from frosting. The reductions of heat and mass transfer rate caused by the thin liquid film are only $1{\sim}2%$ compared with those for non-liquid film surface.

A Study of the Defrosting Behavior according to Surface Characteristics of a Fin-Tube Heat Exchanger

  • Jhee, Sung;Lee, Kwan-Soo
    • International Journal of Air-Conditioning and Refrigeration
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    • v.8 no.2
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    • pp.101-107
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    • 2000
  • In this study, the defrosting behavior according to the surface characteristics of a fin-tube heat exchanger is experimentally examined. It has been found that the draining rates of the hydrophilic and hydrophobic heat exchangers are evenly dispersed during do-frosting, compared with that of the bare one. This is due to the high density frost of the hydrophilic heat exchanger, and the surface characteristics of the hydrophobic heat ex-changer, The rest periods of the hydrophilic and hydrophobic heat exchangers are shorter, and their weight of residual water is also smaller than that of the bare heat exchanger. The hydrophobic heat exchanger is the most efficient in terms of the defrosting efficiency.

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Modeling for Frost Growth on a Cold Plate (냉각 평판에서 서리 성장 모델링)

  • Yang, Dong-Keun;Lee, Kwan-Soo
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1546-1551
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    • 2004
  • This paper presents a mathematical model to predict the frost properties and heal and mass transfer within the frost layer formed on a cold plate. The laminar flow equations for the air-side are analyzed. and the empirical correlations of local frost properties are employed in order to predict the frost layer growth. The correlations of local frost density and effective thermal conductivity of frost layer, obtained from various experimental conditions, are derived as functions of various frosting parameters (Reynolds number, frost surface temperature, absolute humidity and temperature of moist air, cooling plate temperature, and frost density). The numerical results are compared with experimental data and the results of various models to validate the present model, and agree well with experimental data within a maximum error of 10%. The heat and mass transfer coefficients obtained from the numerical analyses are presented, as the results, it is found that the model for frost growth using the correlation of heat transfer coefficient without solving air flow have a limitation in its application.

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