heat transfer analysis of integral-fin tubes

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Engineering and Technology 2015; 2(2): 23-34 Published online March 30, 2015 (http://www.aascit.org/journal/et) Keywords Heat Transfer, Integral - Fin Tube, Experimental Study Received: March 6, 2015 Revised: March 21, 2015 Accepted: March 22, 2015 Heat Transfer Analysis of Integral-Fin Tubes Laith Jaafer Habeeb 1 , Abdulhassan A. Karamallah 1 , Ayad Mezher Rahmah 2 1 Mech. Eng. Dept., University of Technology, Baghdad-Iraq 2 State Company for Oil Projects (S.C.O.P), Ministry of Oil, Baghdad-Iraq Email address [email protected] (L. J. Habeeb), [email protected] (L. J. Habeeb) Citation Laith Jaafer Habeeb, Abdulhassan A. Karamallah, Ayad Mezher Rahmah. Heat Transfer Analysis of Integral-Fin Tubes. Engineering and Technology. Vol. 2, No. 2, 2015, pp. 23-34. Abstract An experimental system has been adapted to study the heat transfer characteristics for cross flow air cooled single aluminum tube multi passes (smooth and integral low finned tube) and the effect of the integral low fins in enhancement the heat transfer. Also, study all variables which have effect on heat transfer phenomena. A series of experiments was conducted with different variables. The velocities of air across the test section are (1, 2 and 3) m/sec, the water flow rate is (5l/min) and the temperatures of the inlet water to the test tube are (50, 60, 70, 80) o C. In this study, the integral low finned tube gave a good enhancement in heat transfer. Hence, the experimental results showed that the air side heat transfer coefficient of the integral low finned tube was higher than that of the smooth tube and the enhancement ratio (( h o finned / h o smooth ) or ( Nu a finned / Nu a smooth )) was (1.86 to 2.38) for eight passes. Also, the results showed that the increasing of air velocity will improve the outside heat transfer coefficient. In addition to the theoretical analysis, this work presents a suggestion to develop empirical correlations for the air side heat transfer coefficient of an integral low finned tube, represented by the empirical correlations for the air side Nusselt number. The results were compared with previous works of other researchers and gave a good agreement in behavior. 1. Introduction One of the most common methods of enhanced heat transfer is by using integral low fin tubes and the fins usually have a two-dimensional trapezoidal or rectangular cross section [1]. Integral finned tubes are made by extruding the fins from the tube metal. The tube is generally made from (copper, aluminum and its alloys) that are relatively soft and easily worked and also made of other materials (stainless steel, titanium, and its alloys, etc.) [2, 3]. Since the fins are integral with the root tube, perfect thermal contact is ensured under any operating conditions [2]. Integral fin tubes are commonly used in the condensers of refrigeration, air conditioning and process industries especially where low surface tension fluids are used [4]. It is also used in the heat exchanger, evaporator and boiling services [5]. Fins are available in different densities ranging from 433–1675 fins/meter (11–40 fins/inch) [3]. In the last few decades, several three dimensional (3D) enhanced surfaces were developed for condensation heat exchangers. Also, several improvements were introduced to the standard integral finned tubes which resulted in a performance comparable to that of the 3D enhanced surfaces [4]. Low fin heights are ranging from about (0.66 to 1.50) mm depend on the fins density and the particular tube metal [6]. Rich [7] performed an experimental work to determine the effect of fin spacing on heat transfer and friction performance of multi-row fin-and-tube heat exchangers.

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Laith Jaafer Habeeb, Abdulhassan A. Karamallah, Ayad Mezher Rahmah

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Engineering and Technology 2015; 2(2): 23-34 Published online March 30, 2015 (http://!aascit!or"/#ournal/et) Keywords $eat %rans&er,'nte"ral - (in %ube,)*peri+ental ,tud- .ecei/ed: March 0, 2015 .e/ised: March 21, 20151ccepted: March 22, 2015 Heat Transfer Analysis ofIntegral-Fin Tubes Laith Jaafer Habeeb1, Abdulhassan A. Karamallah1,Ayad Mezher Rahmah2 1Mech! )n"! 2ept!, 3ni/ersit- o& %echnolo"-, 4a"hdad-'ra5 2,tate 6o+pan- &or 7il Pro#ects (,!6!7!P), Ministr- o& 7il, 4a"hdad-'ra5 Email address laithhabeeb1894:"+ail!co+ (;! u+aretal!D10Estudiedtheheattrans&erau"+entation durin" condensation o& ater and .-134a /apor on hori?ontal inte"ral-&intubes!'n%hise*peri+entalin/esti"ationas per&or+edontodi&&erente*peri+entalset-ups&orater and .-134a! %arradD19Epresentedaco+puteri?ed+odel&orthe ther+al-h-draulicdesi"no&asin"leshellFsin"lepasslo &innedtubebundleheate*chan"eusin"thestepb-step techni5ue (,,%)! (ernJnde?-,eara et al! D1BE in/esti"ated e*peri+entall- the condensation o& a++onia on s+ooth and inte"ral-&in (32 &ins per inch (&pi)) titaniu+ tubes o& 18!05++ outer dia+eter! 'nthisin/esti"ation,thee&&ecto&aninte"rallo&inned tube in cross &lo air cooled in a hori?ontal sin"le tube +ulti passesontheheattrans&erbeha/iorillbeanal-?ed e*peri+entall- and theoreticall-! 1lso, the e&&ect o& chan"in" air /elocit- and inlet ater te+perature are in/esti"ated! %his orCpresentsasu""estiontode/elope+piricalcorrelations &ortheairsideheattrans&ercoe&&iciento&aninte"rallo &inned tube, represented b- the e+pirical correlations &or the air side Ausselt nu+ber! 2. E!erimental "or# 2.1. T$e Test %ig (i"ures(1-a,b)shoaphotoandsche+aticdia"ra+o& thee*peri+entaltestri"!%hetestri"isdesi"nedand +anu&actured to &ul&il the re5uire+ents o& the test s-ste+ &or as+oothandinte"rallo&innedtube!%hee*peri+ental apparatus consist basicall- o&: %he duct and test section! %he air&lo rates suppl- section! %he ater &lo rates suppl- section! %he +easurin" de/ices! (a) )n"ineerin" and %echnolo"- 2015; 2(2): 23-34 25 (b) Figure (1). Experimental test rig: (a) Photo, (b) Schematic diagram. 2.2. Air Circulation &ystem %heairassuppliedtothetestsectionb-centri&u"al bloero&(390G)!'tassuppliedairatthreele/elso& /elocit- (1, 2, 3) +/sec at the test section, controlled b- usin" +ulticon&i"urationso&circularcross-section"ate +anu&actured&orthispurpose!%he"atecontrolsair+ass &loratesandair/elocitiesatthetestsection!%here5uired /elocities ere obtained b- replacin" the con&i"uration o& the "atebeteenthe&ull-openedithoutan-"ate(+a*i+u+ &lo rate) and 45 partiall- opened (+ini+u+ &lo rate)! %he bloeroutletisconnecteddirectl-toa"al/ani?edsteelair di&&userb-boltsa&terinsertin"therubbersealandsilicon, and the other side o& di&&user is connected ith the to la-ers o& the +esh at the &ace o& the di&&user beteen the +ain duct anddi&&user!%he+eshisdesi"nedand+anu&acturedto ensureda+pin"o&an-disturbanceinairstrea+be&ore enterin" the test section and to obtain a re"ular &lo! %he air bloer is &i*ed to the iron &oundation b- bolts ith thicC rubber beteen the bloer and &oundation &or da+pin" the /ibration hen the bloer operates! %heductis+anu&actured&ro+a"al/ani?edsteelsheetat rectan"ularcrosssectionithidthandhei"ht(251 ++K499++)andlen"th2+iththetestsectionpart!%he duct is connected ith the bloer b- a di&&user and the other sideendedithanotherdi&&useropenedtotheat+osphere a&terinserttherubbersealandsiliconattheed"es!%he suitabletestductlen"this390++&i*edat2000++&ro+ thebe"innin"o&inletdi&&user,thetesttubepassedthrou"h theducthori?ontall-at21B5++&ro+thebe"innin" o&inlet di&&user, as shon &i"ure (2)! Figure (2). Schematic illustration o duct. 20;aith i+,Moo-eon;eeandVon"chan >i+,T+irSide1eatTranser&oeicientsoDiscretePlate #inned5Tube 1eat Exchangers "ith !arge #in PitchU, 1pplied %her+al )n"ineerin", 30, pp!194F1B0, 2010! D14E$!$onda,,!Ao?uandV!%aCeda,T+Theoretical;odelo #ilm&ondensationina9undleo1ori8ontal!o"#inned Tubes T, %ransactions o& the 1,M), eithG!4ed&ord,T#luid ;echanicsU, Ainth edition, McMra-$ill 6o!, 1885!