The determination of field usability of method measuring temperature fields in the air using an infrared camera

a Co esponding au ho : [email protected] The de e mina ion o ield usabili y o me hod measu ing empe a u e ields in he ai using an in a ed came a Ma in Pešek1,a and Ondřej Pech1 1B no Uni e si y o Technology, Facul y o Mechanical Enginee ing, Technická 2896/2, Czech Republic Abs ac . The a icle deals wi h he ield usabili y de e mina ion o he me hod o measu ing empe a u e ields in he ai using an in a ed came a. This me hod is based on he isualiza ion o empe a u e ields on an auxilia y ma e ial, which is inse ed in o he non-iso he mal ai low. In his a icle he ield usabili y is de e mined om ime cons an s o his me hod, which de ine bo de s o usabili y o low empe a u e di e ences (be ween ai low empe a u e and su ounding empe a u e) and o low ai low eloci ies. The ield usabili y de e mina ion o measu ing empe a u e ields in he ai can be used in many a ious applica ions such as ai -hea ing and ai -condi ioning whe e he me hod o measu ing empe a u e ields in he ai by in a ed came a can be used. 1 In oduc ion The empe a u e ield measu emen by he in a ed came a is e y illus a i e and quick way o measu e he alue o empe a u e o he empe a u e ield. The in a ed came a allows o noncon ac measu emen and i is used o his pu pose in many scien i ic disciplines and indus ial applica ions, especially in he ield o hea ans e and he modynamics [1]. The he mog aphy is mainly used o he su ace empe a u e measu emen s. The auxilia y ma e ials applica ion o moni o ing empe a u e ields he ai empe a u e ield is known a long ime [2]. This measu ing me hod p o ides isual image eco ds p o iding quali a i e and quan i a i e in o ma ion o deepe knowledge o he mal condi ions and he modynamic p ocesses in he esea ch objec . The in a ed came a allows measu emen s o he s a ic condi ions and moni o ing o dynamic p ocesses and i is e y sui able o he usage ou side he labo a o y. The impo an issue is o de ine he mos sui able ma e ials ha can be used o moni o ing o he empe a u e dis ibu ion in he ai using in a ed came a by he me hod o inse ing a shee o pape o o he auxilia y ma e ial in o he non-iso he mal ai s eam. This ma e ial mus ha e sui able s a ic p ope ies, mainly a high emissi i y. Also, knowledge o he dynamic p ope ies, especially he knowledge o he ime cons an as a unc ion o ai empe a u e di e ence and he ai eloci y is equi ed o p ac ical applica ions o he me hod. The empe a u e isualiza ion by he in a ed came a also allows o he deepe unde s anding and iden i ying o connec ions in he measu ing p ocesses du ing he moni o ing o a a iable empe a u e ield. The isualiza ion o empe a u e ields in he ai can also de ec he spa ial and ime con ex o moni o ed p ocesses. This me hod o he measu emen o empe a u e ields in he ai can be used in many ields o hea ing and cooling [2]. 2 The measu ing me hod desc ip ion The measu emen me hod o empe a u e ields is based on he usage o he auxilia y ma e ial on which he empe a u e ields a e displayed. This auxilia y ma e ial is placed o he ai -s eam o moni o ed a ea [3]. The con ec i e hea low changes he su ace empe a u e o auxilia y ma e ial which is measu ed by he in a ed came a. The conduc ion hea low c ea es he empe a u e ield on su ace o he auxilia y ma e ial and his su ace empe a u e can be conside ed as he ai empe a u e o his a ea. 3 Conduc ion hea ans e Du ing he isualiza ion o he ai empe a u e ield on he su ace o he auxilia y ma e ial, conduc ion hea ans e occu s he dis ibu ion and also he empe a u e ield sca e ing in he shee o his ma e ial. The hea ans e by conduc ion is de ined by he Fou ie ´s law as  = − ∙  , (1) whe e  (W m-2) is he conduc ion hea lux, λ (W m-1 K-1) is he hea conduc i i y and g ad T (K m-1) is he empe a u e g adien . This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion License 2.0, which pe mi s un es ic ed use, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. DOI: 10.1051/ C Owned by he au ho s, published by EDP Sciences, 2014 , 02091 (2014) /20146702091 67 epjcon EPJ Web o Con e ences A icle a ailable a h p://www.epj-con e ences.o g o h p://dx.doi.o g/10.1051/epjcon /20146702091 The empe a u e ield sca e ing causes he enla gemen o he a ea wi h he isualized ai low, and he e o e i also causes a shi o he ai low bounda y. Conduc ion hea ans e is no desi ed and is eques ed o be elimina ed by he use o an auxilia y ma e ial wi h a low alue o he hea conduc i i y. Un o una ely, he low alue o hea conduc i i y means e y di icul hea ans e by con ec ion on he su ace o auxilia y ma e ial. Low hea conduc i i y causes p oblems wi h imagining o dynamic p ocesses. Bo de s enla gemen o he non-iso he mal ai s eam is possible o de e mine as a solu ion o hea conduc ion p oblem in a semi-in ini e body. Semi-in ini e body ep esen s he body whe e exis s a ce ain dis ance x0 om he su ace such ha o all he dis ances x > x0 he empe a u e T(x, ) equals he ini ial empe a u e T0(x, = 0) e en hough a change o he empe a u e occu s a he su ace (x = 0). This means ha he su ace empe a u e can in luence he empe a u e inside he body up o he dis ance x om he su ace. 3 Con ec i e hea ans e Fo he de e mina ion o hea ans e om he ai s eam o he ma e ial i is necessa y o de ine hea ans e by con ec ion. The con ec i e hea low  (W m-2) is de e mined by he New on´s law  =∙(− ), (2) whe e  (W m-2 K-1) is he hea ans e coe icien ,  (K) is su ace empe a u e and  (K) is ee s eam empe a u e. Figu e 1. App oxima ion wi h he use o he p opo ional sys em o he i s o de [4] The ime cons an  (s) is he quan i y which cha ac e izes he ime needed o he ansi ional s a e (caused by an inpu impulse) o a ise o disappea . The ime cons an is de ined as he ime when 63.2 % o all inc ease o dec ease alue o moni o ing quan i y is eached, igu e 1. 4 Measu emen s o he empe a u e ield sca e ed in he auxilia y ma e ial The hea conduc ion, which cases he expansion o he empe a u e ield a ea in he auxilia y ma e ial, was in es iga ed as well. The assessmen o he conduc ion hea ans e e ec was pe o med by an expe imen and also by nume ical simula ion in STAR CCM+ so wa e p og am. Two ypes o auxilia y ma e ials wi h high emissi i y alues we e in es iga ed. A common shee o o ice pape wi h he emissi i y 0.96 and a shee o co on ex ile wi h he emissi i y 0.93 we e conside ed. Figu e 2. E alua ion o expe imen he empe a u e ield sca e ed in a shee o pape a s eady s a e which occu ed a e 10 seconds Figu e 3. E alua ion o expe imen he empe a u e ield sca e ed in a co on shee a s eady s a e which occu ed a e 10 seconds The expe imen al de e mina ion o empe a u e ield sca e ing was pe o med wi h he use o he he mal p in wi h known dimensions. Subsequen ly ime cou ses o expansion o he empe a u e ield in he shee o auxilia y ma e ial we e eco ded. The objec used as he he mal p in was selec ed o be a cylinde which was made om s ainless s eel (s ainless s eel 304) wi h he diame e d = 50 mm and heigh h = 80 mm. c p EPJ Web o Con e ences 02091-p.2 The expe imen was pe o med wi h he use o he in a ed came a Jenop ic Va ioCam. The cylinde was a ached o he holde and conduc i ely hea ed o app oxima ely 50 °C. Then he shee o he auxilia y ma e ial was sho ly p essed a he base o he cylinde and he in a ed sequence in 60 s was eco ded. The in a ed eco d e alua ion was ca ied ou in he IRBIS p o essional so wa e p og am. A e he con ac o he he mal p in wi h he shee o auxilia y ma e ial i immedia ely ex ended he empe a u e ield ou side he edge o he cylinde by he alue o c o he co on shee o by he alue o p o pape shee . The empe a u e ield was s abilized a e 10 s o p in ing o he co on shee and also o he pape shee . Using he command “ e e ence line” in he IRBIS p o essional so wa e he size o he empe a u e ield expansion was de e mined. In case o he co on shee he sca e ing is c = 3.5 mm and in case o a pape shee p = 3.9 mm. The e alua ions o hese shee s a e shown in igu e 2 and 3. The sca e ing size a ea was measu ed om he edge o he he mal p in o he dis ance whe e he empe a u e ell o 5 % o he o al empe a u e di e ence. Table 1. S a ic p ope ies able o auxilia y ma e ials o de e mine he empe a u e ield sca e ing Auxilia y ma e ials p ope ies O ice pape Co on ab ic The mal p in mass pe a ea m, (g m -2 ) 80 145 - emissi i y ε, (-) 0.96 0.93 - densi y ρ, (kg m -3 ) 750 1550 8000 speci ic hea capaci y c, (J kg -1 K - 1) 1330 1160 500 hea conduc i i y λ, (W m -1 K - 1) 0.05 0.029 16.2 The in es iga ed hea conduc ion p oblem in he auxilia y ma e ial was also in es iga ed by nume ical simula ions. Figu e 4. Simpli ied geome y o he model o he de e mina ion o he empe a u e ield sca e ed in he shee o auxilia y ma e ial One o possible simula ion p og ams is STAR CCM+. This p og am allows o sol e non-s a iona y hea conduc ion p oblems. The i s s ep was o c ea e he model geome y. In his geome y model is subsequen ly applied ma hema ical echniques and physical laws on he based on de ined bounda ies and ini ial condi ions. The s a ic p ope ies o auxilia y ma e ials we e used acco ding o able 1, i.e. he same condi ions as we e in he expe imen . The simula ion was pe o med on he simpli ied model, see igu e 4. The model was c ea ed wi h a 2D polyhed al compu a ional g id wi h a densi y o 36,000 cells. Due o a be e desc ip ion o hea ans e in o he shee o auxilia y ma e ial, he he mal p in posi ion and he measu ed shee we e equipped wi h a p isma ic bounda y laye wi h a hickness o 30 cells (4 mm). The a ea whe e he dis ibu ion o empe a u e ield was expec ed om he expe imen (10 mm om he wall o cylinde o he ma e ial), was e ined in o de o achie e a mo e accu a e desc ip ion o he dis ibu ion o he hea low in o he auxilia y ma e ial. A he bo de he bounda y condi ion was se o “Symme y plane”. The “Symme y plane” bounda y condi ion does no limi he calcula ion and i will no in luence he undesi ed hea ene gy accumula ion a he bo de s o geome y. In he posi ion o he con ac he mal p in ma e ial, he “in-place” bounda y condi ion was in oduced, which allows he con ac be ween wo di e en kinds o ma e ials ( he mal p in and shee o an auxilia y ma e ial). The simula ion was sol ed as a non-s a iona y ask las ing 30 seconds, which leads o wo ma e ial p in s o di e en empe a u es wi h a cons an densi y. Due o he ease o calcula ion, he seg ega ed sol e in ol ing seconda y solid ene gy g adien s was chosen. Du ing he calcula ion he moni o ing o he esidual ene gy con e gence le el wi h he accu acy highe han 10-4 was ca ied ou . The esul o he ma hema ical simula ion om he simula ion p og am STAR CCM+ is shown in igu es 5 o shee o o ice pape . Fo he co on shee he alues c = 3.2 mm was calcula ed and o he pape shee i was p = 3.8 mm, which is in ag eemen wi h expe imen s. Figu e 5. E alua ion o ma hema ical simula ion o he empe a u e ield sca e ed in a shee o pape a s eady s a e a e 10 seconds c EFM 2013 02091-p.3 5 De e mina ion o ield usabili y Measu emen s o he ai empe a u e ield using he in es iga ed me hod is ela i ely accu a e, i hey a e done in he ield o usabili y o he me hod. The a ea o ield usabili y is based on limi ing he ange o he empe a u e di e ence and he ange o he eloci y non- iso he mal ai low, which depend on he ime cons an o he me hod. The measu emen accu acy is de e mined by measu emen unce ain ies [4, 5]. In a eas whe e a high unce ain y is p oduced, i is no app op ia e o measu e he empe a u e ield using his me hod. Figu e 6. 2D iew on he ield o usabili y o he me hod o he isualiza ion and measu emen o empe a u e ields in ai by in a ed came a – he o ice pape Figu e 7. 2D iew on he ield o usabili y o he me hod o he isualiza ion and measu emen o empe a u e ields in ai by in a ed came a – he co on shee The ield o usabili y o he me hod was de e mined om he dependence on he ime cons an , empe a u e di e ences and low eloci y o he co on ex ile and o he o ice pape In hese dependences (Figu e 6 and 7) he a ea wi h a high ime cons an was supp essed, which indica es ha he empe a u e ield measu emen using his me hod is less sui able in hese a eas. 6 Conclusions The ob ained g aphs o he ime cons an s a e impo an o c ea ing a me hodology o measu emen s o empe a u e ields in he ai by he in a ed came a. The ime cons an s wi h he emissi i y o auxilia y ma e ial, pa ame e s o in a ed came a and applica ion limi s o he desc ibed me hod allow o measu emen s in case o low eloci ies and small empe a u e di e ences. The ield o usabili y o he in a ed came a o measu emen s o he empe a u e ield in he ai is ela ed o equi emen s, which a e equi ed by applica ions o measu emen s. In he case he ime cons an o he me hod is equi ed o be less han 8 seconds, he ield usabili y can be de e mined om igu e 8 and igu e 9. These alues o he ime cons an o 8 s a e included in able 2. Table 2 Field usabili y o he me hod o isualiza ion and measu emen o empe a u e ields in ai using an in a ed came a o he ime cons an less han 8 seconds Auxilia y ma e ial Veloci y Tempe a u e di e ence o ice pape depends on he IR came a accu acy depends on he IR came a accu acy co on shee om 1.2 m s -1 om 6 K In assessing o he ield usabili y o he me hod i is necessa y o conside he in luence o hea conduc ion in he auxilia y ma e ial. This can cause some "blu " e ec s which is usually no possible o iden i y in non- iso he mal ai s eams. This e ec needs o be especially conside ed in a eas wi h la ge empe a u e g adien s, e.g. in he mal limi laye s. Acknowledgemen s The esea ch leading o he p esen ed esul s was suppo ed by he NETME Cen e ED0002/01/01 and B no Uni e si y o Technology p ojec FSI-J-13-2042 o young esea che s. Re e ences 1. M. Vollme , K.-S. Mollmann, In a ed The mal Imaging: Fundamen als, Resea ch and Applica ions, Wiley (2010) 2. M. Pešek, M. Pa elek, Se kání ka ede mechaniky eku in a e momechaniky, Mikulo (2010) 3. M. Pešek, M. Pa elek, Expe imen al luid mechanics, Jičín (2011) 4. T. O zechowski, Ł.J. O man, Science Repo (2006) 5. T. O zechowski, Ł.J. O man, Pollu ion Enginee ing (2006) Veloci y low (m∙s-1) Time cons an (s) Tempe a u e di e ence (T) Time cons an (s) Tempe a u e di e ence (T) Veloci y low (m∙s-1) EPJ Web o Con e ences 02091-p.4