The evaluative study of window defrost using Computational Fluid Dynamics

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⦽ǎᱥᔑᮁℕŖ⦺⫭

(26일 목)

제 3 발 표 장

179

CFD응용 Ⅰ

CFDᛔ Ⓦ␁㊴ Window Defrosting ㄡक़

決ࣜ汾ࣜ朞

࣭ࣦ

_{ࣨࣜ沊ࣜ箮ࣜ單}

࣮

_{ࣨࣜ牢ࣜ沲ࣜ毋}

࣭ࣜ

T

he evaluative study of window defrost using Computational Fluid Dynamics. I.S. Lee, H.N. Im, J.W. ChoiG

The purpose of this sutdy is to evaluate a defrost model for the possibility of defrosting on wheelhouse window and the heat apacity of defrosting nozzle by using the commercial CFD solver FLUENT. A detailed simulation model has been created which contains the defrosting nozzle, window and the interior/exterior forced convection boundary. In this numerical study, the heat and mass transfer coupled during defrosting and investigated the defrost time for different hot gas temperature, external wind speed and temperature condition.

Key words: ╜Ḉ⑸⨌⍅㊱(CFD), ᮜ╭ḙ⑸ᄱ(Unsteady Flow), Defrosting

41#⇆##ᤊ#

ၘஈ ⎀ᄜक़ ฆ⒘ ✘⍅⒜ ␌㋅㊰࿬ Ṹᥭ⒰ ਕ␈ ‼ฌ⏐⒰ ⎀ᄜ⦀ᖴ ⓐ㊰⍄ Fig. 1੔Gṯ㧊GṸᥭ wheelhouse⒰ ⑸ᜄ⦕⌨ ẉ⌨(frost)क़ ḵஈ࿬

㍜ḙⓌ ᥴḵ㊰ਸ ⓠြ. Ⓦᛔ ㋌ਈ㊰ஈ ⑜㋌Ṵ ୑✘␌㋅ Ṹᥭ⒰ ਕ␈ heated windowᛔ Ⓦ␁㊰ਸ ⓠ⒔෰ ୑✘␌㋅ ṸᥭⓌ ⊜ဤ ਕ␈ Ⴍ【G 㓠⺈Oduct heater)ᛔ ⼍㋌Ṵ ⑸ᜄ⦕ ฌ᫘⌨ ✙╩ ᒀৈ␌ ੍ஈᛔ ᫠⌌Ṵ ẉ⌨ᛔ ╴ৈ㊰࿬ ᦁ᧭⒜ ≈ਸ ⓠြ. ᩐ ⍈ૄ⌨Ṵ࿬ Ⴍ【G䧞䎆ᛔ Ⓦ␁㊸ ਕ␈ 㓠⺈ ␁ᔡ⌨ ኈᓔ ẉ⌨क़ ╴ৈᅰ࿬ ╭ᄜ ᥧ ╴ৈ‴ड़⌨ ၘ㊴ ╭ᩌᛔ⌓ਸⓨẉ⌨⒰╴ৈ‴ᤄᕠⓌẰ⒜ὰ㋡㊰⍘ြ. ISO(the International Organization for Standardization) 8863 - “Ship’s wheelhouse windows – Heating by hot air of glass panes” ⎘ॱ⒘ૅ╴଴╭⌨࿬⏐ஈ◈ৌⓌ -20䠼GᥧṸᥭⓌ ␌㋅㊰៌Ṵ ╩㊸ ὰ ⓠ࿬ ြ⋩㊴ ⏐ஈ ◈ৌ⌨ ၘ㊰⍄ defrost ẉ࿽⒜

৘⻸㊸৛⒜៝ஈ㊰ਸⓠြ. ᩐ໔ᢐ⌨Ṵ࿬Ṹᥭ⒰Ṽਜ⏬ૄ◈ৌ⒔ᖴṴ

৘⻸ᅰ⌌⋔ ㊰࿬ ြ⋩㊴ ⏐ஈ ◈ৌ⌨ ၘ㊰⍄ Wheelhouse⒰ Defrosting

ẉ࿽⒜৘⻸㊰ஈ⑜㊰⍄ḙ␁ CFD ㉜ᖴ୐ᔀⓐ FLUENTᛔⓌ␁㊰⍘ြ.

Fig. 1 Window frost in wheelhouse

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ᩐ ⍈ૄ࿬ FLUENT Ver. 13.0⒜Ⓦ␁㊰⍄ਜḈ㊰⍘ြ. Pressure-based ᩌ◌ ᦁ╭‵੔ realizable k-epsilon ෴ᚰ᠀ა⒜ Ⓦ␁㊰⍘ਸ, ⩠ஈ◈ৌ⒔ᖴ᫘⺈G ゚╭ḙḙ⸴(unsteady)ᖴ ㋌ṵ⒜ ㊰⍘ြ. ẉ⌨࿬G 㠒㦢OpŠŒP㌗㦚G Ṗ㩫䞮㡖㦒ⳆG ms|lu{㠦㍲G 㩲Ὃ䞮⓪GSolidification and Melting ᠀ა⒜ Ⓦ␁㊰⍄ defrosting ਜḈ⒜ ὰ㋡㊰⍘ြ. ਁⓨ࿬ window ♔⑜⌨ ਕਜ⮍Oboundary layer)ᛔ ╙␁㊴ unstructured meshᖴ ḵẉ㊰⍘ਸ, ╜⨌ẘOŠŒ““P ὰ࿬ 30ᜤॴ╭ᄜᖴG䞮㡖┺UG~ŒŒ“–œšŒ㦮G⌊₆㢖G㣎₆⓪G m–™ŠŒ‹G Š–•ŒŠ›–•G 㫆Ị㦚G 㩗㣿䞮㡖㦒ⳆG 㣎₆⓪G YW”Vš㦮G 㥶㏣㦚G Ṗ㩫䞮㡖┺UG⡦䞲G⌊₆㦮G㡾☚⓪GYZఁ⪲G䞮㡖㦒ⳆG㣎₆G㡾☚⓪GTX\ఁG ⪲GṖ㩫䞮㡖┺UGkŒ™–š›•ŽG•–¡¡“Œ㠦㍲GὋ ♮⓪GὋ₆㦮G㡾☚⓪GG[XఁSG 1 Ḕẉ♩੍⌝◈Ṹ㋌⋩⍈ૄỤ 2 ╭㏤␨, Ḕẉ♩੍⌝◈Ṹ㋌⋩⍈ૄỤ

* Corresponding author E-mail: [email protected]

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⦽ǎᱥᔑᮁℕŖ⦺⫭

180

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CFD응용 Ⅰ 㥶㏣㦖G _”Vš⪲G 䞮㡖┺UG 㞫⩻ὒG ㏣☚㦮G 䄺䝢ⰗG ⹿⻫㦒⪲G wpzv⯒G ㌂㣿䞮㡖㦒ⳆG 㞫⩻㦮G 䟊⻫㦒⪲⓪G wylz{vSG ⳾Ⲯ䎖㦮G 䟊⻫㦒⪲⓪G {™‹Tv™‹Œ™G t|zjs㦚G ㌂㣿䞮㡖㦒ⳆG ⋲⮮⳾◎㦖G zŒŠ–•‹G v™‹Œ™G |—ž•‹G㓺䌊㦚G㌂㣿䞮㡖┺UG

2.1 Phase change model

FLUENT⒰ ḙᨘ㎬ ੔╭⒘ enthalpy-porosity techniqueᛔ Ḅ␁㊰ਸ ⓠြ.

Fig. 2 Enthalpy variation on solidification

⎀ᄜᨘ㎬⌨ ኈᛐ ⓸⍌⒰ ᨘ㎬ᔡ⒜ ୔ৈᖴ ⊹ḙOLiquid phase)⎘ ਸ⨌ḙOSolid phase)ᛔ ૄ᫜㊴ြ. ᩐ ਜḈ⌨Ṵ Ice layer⒰GLiquid fraction⒘ 0~1⒰ ४⒔ᖴ ⩠ஈG ᫜ㅄᅰਸ Fig. 2⎘G ṯ㧊G ⓸⍌⒰ ᨘ㎬ᛔ ஈ♘⒔ᖴ MeltingⓌ Ⓦᙀ⌌✘࿬✘ᛔ と၀㊴ြ. ‵(1)⌨ ḙᨘ㎬⌨ ၘ㊴ Liquid fraction(0<䧍<1)⌨ၘ㊰⍄ㆴ‴㊰⍘ြ. � ���_� � ����������� � �������� � ���_� � ����������� � �������� � ���_� � ������������ ����������������������������������� ��� � ���������(1)

Fig. 3 Liquid fraction variation between Liquid and solid

⍄ஈṴ ׷H࿬ ⓸⍌OLatent heat content), L⒘ Liquid fraction(0:solid ~

1:liquid) Ⓦြ. ḙ⒰᫜⒘mŽUGZὒGṯ㧊G⎀ᄜ◈ৌ 271K~273K⌨Ṵਸ⨌⎘⊹⨌⒰ ਕਜक़ᅴြਸक़╭㊰⍘ြ.

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Table 1⌨ defrosting ਜḈ⌨ Ḅ␁㊴ ⌔⒤S ⑸ᜄ ᥧ ੍ஈ⒰ ᢔẉ⮰ᛔ ㆴ‴㊰⍘ြ. ख़ख़G ms|lu{㦮G ”ˆ›Œ™ˆ“G ‹ˆ›ˆ‰ˆšŒ㦮G Ṩ㦚G ₆㭖㦒⪲G 㩫㦮䞮㡖㦒ⳆG 㠒㦢㌗㠦G ╖䟊㍲⓪G 㠒㦢ὒG ⶒ㧊G ㍴㡂G 㧞⓪G ộ㦒⪲G Ṗ㩫䞮㡂G㩗╏䞲Gⶒ㎇䂮OpŠŒT~ˆ›Œ™G—ˆšŒP⪲G㩫㦮䞮㡖┺UG㠒㦢ὒGⶒ㦮G ゚㥾㦖G㍶⹫㦮G㤊䟃䟃⪲㦮G㫆Ị㠦G➆⧒G┺⯊ἶG䡚㔺㩗㦒⪲G⁎Gⶒ㎇㦚G 㩫䢫䧞G㞢₆ṖG㓓㰖G㞠₆G➢ⶎ㠦GpŠŒT~ˆ›Œ™G㌗㦮G㦋䟊䡚㌗㦚G䕢㞛䞮₆G 㥚䞮㡂G㑲㑮䞲G㠒㦢㌗ὒGỆ㦮G㥶㌂䞲Gⶒ㎇㦒⪲GṖ㩫䞮㡖┺UG

Table 1 Material properties Material : glass (solid)

Property Units Value(s)

Density kg/m3 ₂₅₀₀

Cp(Specific Heat) J/kg-K 800 Thermal Conductivity W/m-K 0.78

Material : ice-water (fluid)

Property Units Value(s)

Density kg/m3 ₉₂₀

Thermal Conductivity W/m-K 1.88

Viscosity kg/m-s 0.00553

Pure Solvent Melting Heat J/kg 334960 Cp (Specific Heat) J/kg-K 2040

Solidus Temperature K 271

Liquidus Temperature K 273

Material : air (fluid)

Property Units Value(s)

Density kg/m3 _1.225

Cp(Specific Heat) J/kg-K 1006.43 Thermal Conductivity W/m-K 0.0242

Viscosity kg/m-s 1.789e-05

G

Fig. 4⌨ᩐਜḈ⌨Ḅ␁㊴Ṹᥭ⒰ Wheelhouse ᠀ა੔ਜḈ domain⒜ ෰⸘ฌ⌠ြ. ~ŒŒ“–œšŒG㩚㼊⯒G⳾◎Ⱇ䞮⓪Gộ㦖GἚ㌆G㧦㤦㦮G䞲Ἒ㢖G Ἒ㌆G 㔲ṚG ❇㦮G 㩲㟓㦒⪲G 䡚㔺㩗㦒⪲G 㠊⩺㤖㧊G 㧞₆G ➢ⶎ㠦G 㔺⌊㦮G 㥞☚㤆G㞴⿖⿚㠦G㽞㩦㦚Gⰴ㿪㠊GṚ⨋䞮ỢG⳾◎ⰗG䞮㡖┺UG㠒㦢㦮G⚦℮⓪G \””G⪲GṖ㩫䞮㡖┺UGG {Œ”—Œ™ˆ›œ™ŒO{P l•›ˆ“— OoP sˆ›Œ•›GoŒˆ› {š {s 6GORGTCVWTG=-? 0 0.2 0.4 0.6 0.8 1 1.2 258 263 268 273 278 283 288 293 Liquid Fraction 2011 전산유체 학술대회-2차 수정.indd 180 2011-05-23 오전 9:56:54

G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G ⦽ǎᱥᔑᮁℕŖ⦺⫭

(26일 목)

제 3 발 표 장

181

CFD응용 Ⅰ Fi ㍶ ⏒ 㭧 G m ‹Œ ⿖ •– ゚ 㥞 ig.5ᶩ ㍶⹫㠦㍲ ⏒ⶎ㠦㍲ 㭧㞯㦚G ŽUG ] Œ™–š› ⿖⿚㠦G –¡¡“Œ ゚䞮㡂G 㥞☚㤆G F defros ㍲⓪G ㍲⓪G 㦚䟻䞮 ]㠦G 㠒 š›•ŽG• 㢚㩚 㠦㍲G ⹎⹎ 㤆 䚲Ⳋ Fig. 4 S stingn ‹Œ™– ⽎⧮ 䞮㡂G⿚ 㠒㦢G •–¡¡“ 㩚䧞G ⿚㌂♮ ⹎䞲G ⨟ Ⳋ㠦㍲ Schem nozzleဵ –š›•Ž ⧮㦮G ⳿ ⿚㌂♮☚ Fig 㦋䟊 “Œ⪲⿖ 㦋䟊Ṗ ㌂♮⓪G ⨟㧊₆ ㍲⓪G ⏎ OˆP O maticof ဵᕙ⤉ ᕝᢅ ŽG•–¡ ⳿㩗㧎 ☚⪳G⳾ g. 5 Pat 䟊㦮G Ἒ ⿖䎆G⿚ ṖG 㧊 Ὃ₆㦮 ₆G ➢ⶎ ⏎㯦⪲ zŠ O‰P of comp ᢅ௱੭GὋ ¡¡“Œ㦖 㧎G ž• ⳾◎Ⱇ ath-line Ἒ㌆ἆ ⿚㌂♮ 㧊⬾㠊 㦮G㥶 ⶎ㠦G 㔺 ⪲⿖䎆 Œ”ˆ› z”œ mputatio Ὃ₆㦮 㦖Gṗ☚ •‹–ž ⰗG䞮㡖 e from ἆὒ⯒ ♮㠊G㥞 㠊㰖⓪ 㥶⨟㦖 㔺⌊Ὃ 䎆G ⿚㌂ ›ŠG–G œ“ˆ›–• onal do 㦮G—ˆ› ☚㫆㩞 žG ‹Œ 㡖┺U defros ⯒G ⋮䌖 㥞☚㤆 ộ㦚 žŒŒ Ὃ₆㦮 ㌂♮⓪ žŒŒ •G‹–” omain ›T“• 㧊GṖ ™–š› sting no 䌖⌊㠞 㤆G䚲Ⳋ 㦚G 㞢G Œ“–œ 㦮G ㌗㔏 ⓪G Ὃ Œ“–œ ”ˆ•G of the •Œ㦚G䚲 Ṗ⓻䞮☚ •Ž㦚G ozzle 㠞┺UG Ⳋ㠦G⥾ 㞢 㑮G œšŒG㔺 㔏㦖G Ὃ₆ṖG œšŒ windo 䚲㔲䞮 ☚⪳G♮ 㦚 㥚䞮 ╖⨋G ⥾Ệ㤊 㧞┺ 㔺⌊GὋ 㧊⬾㠊 ╕㞚 ow 䞮㡖┺ ♮㠊㧞 䞮㡂G ⨋ Y㔲 㤊GὋ₆ ┺UG kŒ Ὃ₆㦮 㠊㰖㰖 㞚G 㰖㏣ ┺UG㔺㩲 㧞㦒Ⳇ 㥞☚㤆 㔲ṚG 䤚 ₆ṖG╕ Œ™–š› 㦮G㥶⨟ 㰖G 㞠㦒 ㏣㩗㦒 㩲㦮G ⳆG⽎G 㤆㦮G 䤚㠦G ╕⓪G ›•ŽG ⨟㠦G 㦒ⳆG 㦒⪲G 䚲Ⳋ㡾 ⽎G⏒ TX\ఁ 㞢G㑮 㡾☚Ṗ ⏒ⶎ㠦㍲ ఁ㧎Gἓ 㑮G㧞┺ ṖG㌗㔏 ㍲GἚ㌆ ἓ㤆㠦 ┺UG (a) (b)2 (c)3 (d) 㔏♮⓪ ㌆䞲 㠦⓪G‹ 1000 s 2000 s 3000 s 5000 s ⓪G㡗㡃 ŠˆšŒ ‹Œ™– sec, Liq sec, Li sec, Liq sec, Li 㡃ⰢG‹ Œ㦮GἚ š›•ŽG iquidfr iquidfr iquidfr iquidfr ‹Œ™–š Ἒ㌆ἆὒ •–¡¡ fraction fraction fraction fraction š›•Ž㧊 ὒ㠦G ¡“Œ㦮G n of win n of win n of win n of win 㧊G㧊⬾ ➆⯊Ⳋ 䧞䕛 ndow indow ndow indow ⬾㠊㰖 ⳊG㤊䟃 䕛G䕢㤢 wouters wouter wouters wouter 㰖⓪Gộ 㤊䟃䟃⪲ 㤢⓪G㩗 surface surfac surface surfac ộ㦚G㞢 ⪲㦮G㣎 㩗╏䞮 e ce e ce 㞢G㑮G 㣎₆㫆 䞮㰖G㞠 㧞┺U 㫆Ị㧊 㞠㦢㦚 ┺UG 㧊G 㦚G 2011 전산유체 학술대회-2차 수정.indd 181 2011-05-23 오전 9:57:03

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CFD응용 Ⅰ

(e) 8000 sec, Liquid fraction of window outer surface Fig. 6 Time evolution of the liquid fraction distribution

71#൚ᤊ#Ჹ#㙏㝮#ඦ⣆

ਈ᮱ ‴㌰⓽⌨Ṵ ‼╴ wheelhouse⒰ ਈ᮱ ‼㌰⒜ ὰ㋡㊰࿬ ৛⒘ ᜼␈ ╴㊴╙Ⓦြ. ‼ฌ/⏐⒰ ‍ᄜ◈ৌ ᥧ ⏐ஈ⒰ ㇥ụ, ⎀ᄜ◈ৌ⒜ २⊠㊰⍄ ㍜‼╙ⓐ ‼㌰⒜ ὰ㋡㊰࿬ ৛⒘ ⌌ᖍஈ ኤᢐ⌨ ြ⋩㊴ Ṹᥭ⒰ ␌㋅◈ৌ⒜ ਸᕼ㊰⍄ wheelhouse ①ᄜ␈⌨ ḵஈ࿬ ẉ⌨ᛔ ╴ৈ㊰࿬ ᦁ᧭⒰ ㊰෰ⓐ 㓠【G ▫䔎⒰ ㊜⏬ ᥴ⍌ᔡ⒜ ㎭ⓐ㊰ஈ ⑜㊰⍄ defrosting ⑸ᄱ㋌ṵ⒜ὰ㋡㊰⍘ြ. ᩐ໔ᢐ⌨Ṵ࿬ FLUENT⒰ solidification & melting ᠀ა⒜ Ⓦ␁㊰⍄ ⌔⒤⒰ ⒍㋌㍜ḙᜤ⒜ ㋌ṵ㊰⍘⒔෰ ‼╴⒰ defrosting੔╭⒘ ⒍㋌⎘G 㯳⹲㦚 ᄱ‴⌨ ⫬╭㊰⍄⋔G 䞮ᤘᖴ ㋽㐜 ⛵ᥴG 䟊ṵ⒜ ὰ㋡㊰ਸ ᩌြ ╭㎭㊴ Ⴍ【G 䧞䎆⒰ ␁ᔡ⒜ Ḉ╭㊸ ὰ ⓠᄜᖵ ㋌⋔㊴ြ.

Ⳣඊᯢ㙶

[1] 2005, S. Roy et al., Efficient defrosting of an inclined flat surface, International

Journal of Heat and Mass Transfer, 48, 2613-2624.

[2] Padmesh Mandloi et al., Case-Studies on CFD Simulation of Windshield De-icing, Ansys

[3] 2010, ANSYS FLUENT User’s Guide Release 13.0.