Numerical and Experimental Investigations for Effect of Gravity to the Heat Transfer and Fluid Flow Phenomena of Microchannel Heat Exchangers

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1 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: Nuerial and Experiental Investigations for Effet of Gravity to te Heat ransfer and Fluid Flow Penoena of Miroannel Heat Exangers antrung Dang 1* Ngotan ran and Jy-tong eng 1 Departent of Heat and Refrigeration enology Ho Ci Min City University of enial Eduation Ho Ci Min City Vietna Departent of Meanial Engineering Cung Yuan Cristian University aiwan Abstrat For bot nuerially and experientally effet of gravity on te eat transfer and fluid flow penoenon of iroannel eat exangers was presented. e influene was deterined by two ases: one wit orizontal annels te oter wit vertial annels. For vertial annels te ot water is flowing upward wi is against te gravitational field wile te old water is flowing downward wi is in te sae diretion as te gravitational field. In tis study te differene between te results obtained fro orizontal annels and tose fro vertial ones is negligibly sall; te ipat of gravity on te fluid troug te iroannel eat exangers was found to be sall wit te axiu differene between te two ases being less tan 8%. e results obtained fro nuerial siulation and experiental data are in good agreeent. In addition good agreeents were also aieved between te results obtained in te present study and te results obtained in literatures. Keywords: iro eat exanger gravity eat transfer rate pressure drop perforane index. I. INRODUCION e developent of effetive ooling devies as prooted attrative area of study in iroannel eat transfer in reent years. A review on iro eat exangers was done by Dang et al. [1] wit five setions. e first setion dealt wit te singlepase iro eat exangers wi onsist of te iro annel eat exangers as well as te iro porous/foa eat exangers. e seond setion reviewed te two-pase iro eat exangers wi onsist of iro evaporators and iro ondensers. e tird setion dealt wit iro eat exangers for arbon dioxide air onditioning syste. e fourt setion reviewed optiization of iro eat exanger. e last setion dealt wit oter types of iro eat exangers. David et al. [] studied ydrauli and teral arateristis of a vapor venting two-pase iroannel eat exanger. ey found 60% iproveent in te noralized pressure drop and up to 4.4 C redution in te average substrate teperature between te ontrol and vapor venting devie under siilar operating onditions. Brandner et al. [3] desribed irostruture eat exangers and teir appliations in laboratory and industry. Several iro eat exangers were introdued: polyer iroannel eat exanger wit aluinu separation foil eletrially powered lab-sale iroannel evaporator erai ounter-flow irostruture eat exanger et. Aeel et al. [4] presented an overview of te iniaturization tenologies and teir appliations to energy systes. Based on te MEMS tenologies (silion-based iroaining deep X-ray litograpy and te iro eanial aining) proesses were disussed in te ontext of appliations to fluid flow eat transfer and energy systes. Review on experiental results onerning singlepase onvetive eat transfer in iroannels was presented by Morini [5] wit additional review results obtained for te frition fator te lainar-to-turbulent transition and te Nusselt nuber in annels aving a ydrauli diaeter less tan 1. Matew and Hegab [6] studied on te appliation of effetiveness-nu relationsip to parallel-flow iroannel eat exangers. Besides developent of nondiensional paraeters (su as axial distane teperature and eat transfer rate) was arrier out. However te results were analyzed teoretially only. Studies of effetiveness and pressure drop for iro ross-flow eat exanger were presented by Kang and seng [7]. At te sae effetiveness eat transfer rate and pressure drop were expressed as a funtion of average teperature. However in teir study tey did not study for te ases wit varying ass flow rates at ea side. Cein and Cen [8] presented a nuerial study of te effet of inlet/outlet arrangeent on te perforane of iroannel eat sink. Six types of eat sink were studied wit te best perforane being te V-type. Beause tat if te iroanels ave te sae ross-setion area and widt of iroannel te dept of iroannel obtained fro V-saped iroannel is deeper tan tat obtained fro retangular-saped one. So it is not easy to design a eat exanger wit te subtrate tikness fro 1. to using V-type iroannels. Foli et al. [9] studied nuerially on te eat flux eat transfer rate and pressure drop in annels wit nuerous aspet ratios. However te results in Ref. [9] were presented witout experients. A study on te siulations of a trapezoidal saped iro eat exanger was presented by Dang et al. [10]. For te iroannel eat exanger beaviors of te teperature eat flux and veloity profiles were deterined. Effet of flow arrangeent on te eat transfer related beaviors of a iroannel eat exanger was presented by Dang et al. [11 1]. For all ases done in te study te eat flux and perforane index obtained fro te ounter-flow arrangeent are always iger IJCER Mar-Apr 01 Vol. Issue No Page 60

2 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: tan tose obtained fro te parallel-flow one: te values obtained fro te ounter-flow are 1.1 to 1. ties of tose obtained fro te parallel-flow. Dang and eng [13] studied effet of te substrate tikness of ounter-flow iroannel eat exangers on te eat transfer beaviors. It was found tat te atual eat transfer rate varies insignifiantly wit te substrate tiknesses varying fro 1. to. However te results obtained in [13] only entioned te eat transfer beaviors of te eat exangers wile te fluid flow beaviors of te eat exangers were not disussed. Dang et al. [14] presented an experiental study of te effets of gravity on eat transfer and pressure drop beaviors of a iroannel eat exanger. However te results in [14] were presented only for a iroannel eat exanger evaluated under te ondition of rising te inlet teperature for te ot side. Dang and eng [15 16] studied te effets of onfigurations on perforane of te iroannel and iniannel eat exangers. However teir study ignored te effets of gravity on te perforane index of iroannel eat exangers. o suarize it is goal of tis paper to study te effets of gravity on te eat transfer and fluid flow arateristis of iroannel eat exangers for bot nuerially and experientally. In te following setion two iroannel eat exangers will be disussed under te ondition of rising ass flow rate for te old side. II. MEHODOLOGY A. Mateatial odel e governing equations in tis syste onsist of te ontinuity equation oentu equations and energy equation [1718]. e equations an be expressed by Continuity equation u v w u v w 0 (1) t x y z x y z Moentu equations u u u u u v w t x y z 1 p u u u g x (a) x x y z v v v v 1 p v v v u v w g t x y z y (b) y x y z w w w w u v w t x y z 1 p w w w g z () z x y z For steady-state onditions u/ t = 0; te boundary onditions of inlet flow are u = 0 v = 0 and w = w 0 ; te boundary onditions of outlet flow are (u + (u) )n = 0 and p = p 0 were is dynai visosity is density g is gravity fore u is veloity field u is veloity in te x-diretion v is veloity in te y-diretion w is veloity in te z-diretion p is pressure and p 0 is pressure at te outlet. For te energy transport te walls ave no-slip onditions for veloity and teperature at te walls; tese onditions are expressed by u wall = 0 and wall = fluid at wall respetively were wall is wall teperature. e eat transfer equation for te energy transport witin te fluid is: u v w t x y z Qi p x y z (3) For steady-state onditions / t = 0; te boundary ondition of inlet flow is = 0 ; te boundary ondition of outlet flow is onvetive flux expressed by n. (- ) = 0; te teral boundary ondition of te botto and top walls of te iroannel eat exanger are assued to be onstant eat flux expressed by -n. (- ) = q0 ; and te four side-walls are insulated terally expressed by n. q = 0 were eat flux q = - + Cp u is teperature p is speifi eat at onstant pressure Q i is internal eat generation and is teral ondutivity. B. Experiental set-up ree ajor parts are used in te experiental syste: te test setion (te iroannel eat exanger) syringe syste and overall testing loop as sown in Fig. 1. In tis study two iroannel eat exangers were tested. e eat transfer proess of tese devies is arried out between two liquids wi are ot water and old water; te ot and old fluids are flowing in te opposite diretions. Fig. sows te diensions of te test setions. e substrate aterial used for te eat exangers is aluinu wit te teral ondutivity of 37 W/(K) density of 700 kg/ 3 and speifi eat at onstant pressure of 904 J/(kgK). For ea iroannel eat exanger te top side for te ot water as 10 iroannels and te botto side for te old water also as 10 iroannels. e lengt of ea iroannel is 3. Miroannels ave retangular ross-setion wit te widt and te dept being W and D respetively. In a iroannel eat exanger all annels are onneted by IJCER Mar-Apr 01 Vol. Issue No Page 61

3 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: anifolds for te inlet and outlet of ot water and for tose of old water respetively. e anifolds of te eat exangers are of te sae ross-setions: aving a retangular sape wit a widt of 3 and a dept of 300. P Pup Buffer tank Exaust air valve Heat exanger Pre-eater Heater P Balane Water tank Pup Balane Buffer tank Fig. 1. Seati of te test loop for iroannel eat exangers able 1. Geoetrial paraeters of iroannel eat exangers Diensions of te substrate () No. Diensions of te annel () L W W D Fig. sows te diensions of te test setion. In tis study two iroannel eat exangers were designed and anufatured wit teir diensions listed in able 1. Fig. 3 sows a poto of te iroannel eat exanger. ese test setions were anufatured by preision iroaining [4]. Ea inlet ole or outlet ole of te eat exangers as a rosssetional area of 9. e four sides of te eat exanger were terally insulated by te glass wool wit a tikness of 5. o seal te iroannels two layers of PMMA (polyetyl etarylate) are bonded on te top and botto sides of te substrate by UV (ultraviolet) ligt proess as indiated in Fig. 3. e pysial properties of te PMMA and te glass wool are listed in able [17]. Fig.. Diensions of te test setion IJCER Mar-Apr 01 Vol. Issue No Page 6

4 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: PMMA est saple Fig. 3. A poto of te iroannel eat exanger able. e pysial properties of te PMMA and te glass wool Material Density kg/ 3 eral ondutivity W/(K) PMMA Glass wool Experiental data for te iroannel eat exanger were obtained under te onstant roo teperature of 5 ºC. For tis study DI water (deionized water) was used as te working fluid. Ea inlet or outlet of te eat exanger as a set of two teroouples to reord teperature values. So tere are eigt teroouples in total. At ea side a differential pressure transduer was used to easure te pressure drop. o assess te auray of easureents presented in tis work te unertainty values for easured paraeters are listed in able 3. In addition te unertainties on te diensions of iroannel evaluated by using a sanning laser ade by Mitaka/Ryokosa odel NH-3. e unertainties of te sanning laser were estiated to be ± 0.03 µ. Equipents used for te experients are listed as follows [13-16]: 1. eroouples -type. Pup Model PU-087 ade by Jaso 3. Pup VSP-100 ade by okyo Rikakikai 4. Heater Model AXW-8 ade by Medilab 5. Differential pressure transduer Model PMP4110 ade by Duk 6. Miro eletroni balane Model E-14S ade by Sartorious. able 3. Unertainty data for easured paraeters Paraeter eperature Pressure Mass flow rate Cannel eigt Cannel widt Cannel lengt Unertainties 0.1 C 0.05% FS g In order to study te effets of gravity on eat transfer and fluid flow beaviors of te eat exangers all experiental onditions for te two iroannel eat exangers were kept te sae. rougout te paper te experiental onditions of testing were disussed: te ase is studied under ondition of inreasing te ass flow rate of te old side. Furter details of te ase are as follows: e inlet teperature and te ass flow rate of te ot side were fixed at 70 ºC and g/s respetively; at te old side te inlet teperature was fixed at.5 ºC and te ass flow rates were varying fro to g/s. C. Data of analysis In te following analyses te ajor assuptions were ade: - e fluid is a lainar flow - e fluid flow is inopressible and ontinuu IJCER Mar-Apr 01 Vol. Issue No Page 63

5 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: Heat transfer is steady - Negligible radiation eat transfer. For te experients arried out in tis study te effets on te eat transfer and fluid flow su as eat flux effetiveness pressure drop and perforane index of te eat exangers will be disussed as follows. e energy balane equation for te ounter-flow iroannel eat exanger is expressed by: Q - Q loss = Q = Q (4) Or ( i o ) = ( o i ) (5) were Q is eat transfer rate of te ot side Q is eat transfer rate of te old side Q is atual eat transfer rate Q loss is eat loss rate fro te eat exanger to te abient is ass flow rate (subsripts and stand for te ot side and old side respetively) is speifi eat i o i and o are inlet and outlet teperatures of te ot and old side respetively and is atual effetiveness. e axiu eat transfer rate Q ax is evaluated by Q ax = () in ( i i ) (6) e effetiveness (NU etod) is deterined by Q (7) Q ax Q Heat flux is alulated by (o - i ) q A nl W (8) Or q = k = l l R (9) e overall teral resistane R is deterined by R = R ond + R onv (10) e log ean teperature differene is alulated by l ax ax ln in in (11) were is ass flow rate (subsripts and stand for te ot side and old side respetively) n is nuber of iroannels is speifi eat i o i and o are inlet and outlet teperatures of te ot and old sides respetively q is eat flux A is eat transfer area k is overall eat transfer oeffiient Rond is ondutive teral resistane 1 1 Ronv is onvetive teral resistane and are te onvetive eat transfer oeffiients of te ot side and te old sides respetively is tikness of eat transfer is teral ondutivity and is te log ean teperature differene. e Reynolds nuber is alulated by: wd W D Re (1) 4A were D is te ydrauli diaeter w is veloity in te z-diretion is dynai visosity is density A is rosssetional area and P is wetted perieter. P e total pressure drop of te eat exanger is given by p p p (13) t were p and p are pressure drops of ot and old sides respetively. e perforane index is deterined by Q o i (14) p t p ( - p ) IJCER Mar-Apr 01 Vol. Issue No Page 64 l

6 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: IJCER Mar-Apr 01 Vol. Issue No Page 65 e experiental unertainties were estiated following te etod desribed by Holan [19]; te final expressions for unertainties were given as follows: 1 / i o i o Q Q U (15) 1/ Re Re D D W W U (16) 1/ i o i o p p p p U (17) By using te estiated errors of paraeters listed in able 3 te axiu experiental unertainties in deterining Q Re and were 1% 3.1% and 3.3% respetively for all ases being studied. D. Nuerial siulation Nuerial study of te 3D beaviors of eat transfer by te iroannel eat exangers wit single-pase fluid flowing troug was done by using te CFD ACE + software version e algorit of tis software is based on te finite volue etod. For tis study water was used as te working fluid. No internal eat generation is ourred resulting in Q i = 0. Nodalization of tis odel was done by using 174 ells and a relative tolerane was Fig. 4 sows te onvergene of te nuerial solver for oponents of veloity pressure and entalpy. Nuber of iteration Fig. 4. Convergene of te nuerial solver III. RESULS AND DISCUSSION A. Nuerial results For te experients arried out in te study te inlet teperature and te ass flow rate of te ot side were fixed at 70 ºC and g/s respetively; at te old side te inlet teperature was fixed at.5 ºC and te ass flow rates were varying fro to g/s [0]. Fig. 5. e teperature profile of te iroannel eat exanger

7 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: Outlet teperature of ot side 0 C orizontal 1-vertial -orizontal -vertial Mass flow rate of old side g/s Fig. 6. Nuerial oparison of te outlet teperatures of ot side e teral boundary onditions of te top and botto walls of te eat exanger are assued to be onstant eat flux. e onvetive eat transfer oeffiient between te wall and te abient used for tis solver was 10 W/( K) [18]. e teperature profile of te iroannel eat exanger 1 is sown in Fig. 5 for te ass flow rate of g/s at te old side. Fig. 6 sows a nuerial oparison of te outlet teperature of ot side of two iroannel eat exangers under te effet of gravity. It is observed tat te outlet teperatures of ot side obtained fro orizontal annels and tose fro te vertial ones are negligibly sall. A nuerial oparison of te outlet teperatures of old side of two iroannel eat exangers is also sown in Fig. 7. e outlet teperatures (for bot te ot and te old sides) are funtions of te ass flow rate of old side; te outlet teperatures derease as te ass flow rate of te old side inreases. It is sown fro Figs. 6 and 7 tat te differene of outlet teperatures obtained fro orizontal annels and tose fro te vertial ones respetively wit 1 and are negligibly sall wit te axiu perentage error of 0.1%. Outlet teperature of old side 0 C orizontal -vertial -orizontal -vertial Mass flow rate of old side g/s Fig. 7. Nuerial oparison of te outlet teperatures of old side B. Experiental results For te experiental syste te inlet teperature and te ass flow rate of te ot side were fixed at 70 ºC and g/s respetively; at te old side te inlet teperature was fixed at.5 ºC and te ass flow rates were varying fro to g/s [0]. Outlet teperature of ot side 0 C 46 1-orizontal 1-vertial 44 -orizontal -vertial Mass flow rate of old side g/s Fig. 8. Experiental oparison of te outlet teperatures of ot side IJCER Mar-Apr 01 Vol. Issue No Page 66

8 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: In tis study influene of gravity was deterined by two ases: one wit orizontal annels te oter wit vertial annels. For vertial annels te ot water is flowing upward wi is against te gravitational field wile te old water is flowing downward wi is in te sae diretion as te gravitational field. wo iroannel eat exangers 1 and were tested: tese two iroannel eat exangers ave te sae pysial onfigurations for teir substrates anifolds and lengts of annels; only te ross-setional areas of iroannels are different. e iroannels of 1 ave a retangular rosssetion wit widt of 500 and dept of 300 ; te iroannel of 3 widt of 500 and dept of 180. Paraeters of te eat exangers (1 and ) are listed in ore detail in able 1. Outlet teperature of old side 0 C orizontal 1-vertial 40 -orizontal -vertial Mass flow rate of old side g/s Fig. 9. Experiental oparison of te outlet teperatures of old side Experiental oparisons for te outlet teperatures of two iroannel eat exangers are sown in Figs. 8 and 9 under te effet of gravity. Fro Figs. 6-9 it is indiated tat te nuerial results obtaned fro Fig. 6 are in good agreeent wit te experiental results obtained fro Fig. 8 and te nuerial results obtaned fro Fig. 7 are in good agreeent wit tose obtained fro Fig. 9. e axiu differene of outlet teperatures for te oparisons in of ot side obtained fro orizontal annels and tose fro te vertial ones are negligibly sall wit te axiu perentage of.9%. 30 Heat transfer rate W orizontal 1-vertial -orizontal -vertial Mass flow rate of old side g/s Fig. 10. Experiental oparison of te eat transfer rates e outlet teperatures of ot side obtained fro 1 is iger tan tose obtained fro ; owever te outlet teperatures of old side obtained fro 1 is lower tan tose obtained fro. As a result te eat transfer rate obtained fro is iger tan tat obtained fro 1 as sown in Fig. 10. e results obtained fro te present study are in good agreeent wit tose obtained fro [9]. Foli et al. [9] indiated tat under te onstant ass flow rate ondition te iger te eat flux te lower te aspet ratio (defined as te ratio of te iroannel eigt to its widt). It is also sown fro Fig. 10 tat te eat transfer rates obtained fro orizontal annels and tose fro te vertial ones are negligibly sall. e eat transfer rate of te eat exangers is a funtion of te ass flow rate of old side: it inreases fro 4.8 to 9.9 W wit te ass flow rate of old side rising fro to g/s (for te eat exanger ). otal pressure drop Pa orizontal 1-vertial -orizontal -vertial Re nuber of old side Fig. 11. Experiental oparison of te total pressure drops IJCER Mar-Apr 01 Vol. Issue No Page 67

9 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: Perforane index W/kPa orizontal 1-vertial -orizontal -vertial Re nuber of old side Fig. 1. Experiental oparison of te perforane indies Beause tat te ydrauli diaeter of annel in is saller tan tat of annel in 1 tis results in te veloity in te annel of to be iger tan tat of 1 leading to a iger total pressure drop in tan tat in 1 as sown in Fig. 11. Besides te Figure sows tat te total pressure drop is a funtion of Reynolds nuber of old side; te total pressure drop inreases as rising te Re nuber of old side. Experiental results for effets of gravity on te beavior of pressure drop for te iroannel eat exanger are also sown in Fig. 11. It is observed tat te ange of pressure drop between te two ases (orizontal annels and vertial annels) is negligibly sall; te axiu ange in pressure is 7.% for a pressure drop fro 1060 to 044 Pa. It was found tat te pressure drop of is ties iger tan tat of 1 wile te eat transfer rate of is 1.06 ties iger tan tat of 1. As a result te perforane index (defined as te ratio of te eat transfer rate to te pressure drop in te eat exanger) obtained fro 1 is iger tan tat obtained fro as sown in Fig. 1. For eat exanger 1 a perforane index of 1.68 W/kPa was aieved for water fro te ot side aving an inlet teperature of 70 C and a ass flow rate of g/s and for water fro te old side aving an inlet teperature of.5 C and ass flow rate of g/s. It is also observed tat te ange of perforane between te two ases (orizontal annels and vertial annels) is negligibly sall; te axiu ange in perforane is 5.5% out of a perforane index fro to 1.68 W/kPa. A oparison between nuerial and experiental results for eat transfer rate wit orizontal annels is sown in Fig. 13. It is observed tat te nuerial results are in good agreeent wit tose obtained fro te experiental ones wit te axiu perentage error of.94%. 3 Heat transfer rate W Nu. results _ 1 Exp. results _ 1 Nu. results _ Exp. results _ Mass flow rate of old side g/s Fig. 13. Coparison of te eat transfer rates between nuerial and experiental results wit orizontal annels In suary it is onluded tat te ipat of gravity on te fluid flowing troug te iroannel eat exanger an be ignored as indiated in [ ]. IV. CONCLUSION Nuerial and experiental works were done on two iroannel eat exangers to arry out te evaluation of teir perforane for te varying te ass flow rates of te old side. ese two iroannel eat exangers ave te sae pysial onfigurations for teir substrates anifolds and lengts of annels; only te ross-setional areas of iroannels are different. For eat exanger 1 a perforane index of 1.68 W/kPa was aieved for water fro te ot side aving an inlet teperature of 70 C and a ass flow rate of g/s and for water fro te old side aving an inlet teperature of.5 C and ass flow rate of g/s. e ipat of gravity on te fluid troug te iroannel eat exanger was found to be sall wit te axiu differene between te results of orizontal and vertial annels being less tan 8%. e results obtained fro nuerial siulations and experiental data are in good agreeent. In addition in tis study good agreeents were aieved between te results obtained fro te present study and te results obtained fro te literatures. IJCER Mar-Apr 01 Vol. Issue No Page 68

10 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: ACKNOWLEDGMEN e supports of tis work by (1) te projet (Projet No C/HD-CB) sponsored by New Produt & enology Center (NEPECH) HCM City Departent of Siene and enology of Vietna () te projet (Projet Nos. NSC 99-1-E and NSC E ) sponsored by National Siene Counil of te Republi of Cina in aiwan and (3) te projet (under Grant No. CYCU-98-CR-ME) sponsored by te speifi resear fields at Cung Yuan Cristian University aiwan are deeply appreiated. REFERENCES [1].. Dang J.. eng and J.C. Cu Pressure drop and eat transfer arateristis of iroannel eat exangers: a review of nuerial siulation and experiental data International Journal of Mirosale and Nanosale eral and Fluid ransport Penoena Vol. Issue [] M.P. David J. Miler J.E. Steinbrenner Y.Z. Yang M. ouzelbaev K.E. Goodson Hydrauli and teral arateristis of a vapor venting two-pase iroannel eat exanger International Journal of Heat and Mass ransfer Volue 54 Issues pp [3] J.J. Brandner L. Bon. Henning U. Sygulla and K. Subert Mirostruture eat exanger appliations in laboratory and industry Proeedings of ICNMM006 ICNMM Lierik Ireland 006 pp [4].A. Aeel R.O. Warrington R.S. Wegeng and M.K. Drost Miniaturization tenologies applied to energy systes Energy Conversion and Manageent Volue pp [5] G.L. Morini Single-pase onvetive eat transfer in iroannels: a review of experiental results International Journal of eral Sienes Volue 43 Issue pp [6] B. Matew and H. Hegab Appliation of effetiveness-nu relationsip to parallel flow iroannel eat exangers subjeted to external eat transfer International Journal of eral Sienes Volue 49 Issue pp [7] S.W. Kang and S.C. seng Analysis of effetiveness and pressure drop in iro ross-flow eat exanger Applied eral Engineering Volue 7 Isuue pp [8] R. Cein and J. Cen Nuerial study of te inlet/outlet arrangeent effet on iroannel eat sink perforane International Journal of eral Sienes Volue 48 Issue pp [9] K. Foli. Okabe M. Olofer Y. Jin and B. Sendoff Optiization of iro eat exanger: CFD analytial approa and ulti-objetive evolutionary algorits International Journal of Heat and Mass ransfer Volue 49 Issue pp [10].. Dang Y.J. Cang and J.. eng A study on te siulations of a trapezoidal saped iro eat exanger Journal of Advaned Engineering Volue 4 Issue pp [11].. Dang J.. eng and J.C. Cu Effet of flow arrangeent on te eat transfer beaviors of a iroannel eat exanger Proeedings of te International MultiConferene of Engineers and Coputer Sientists 010 Hongkong 010 pp [1].. Dang and J. eng Influene of flow arrangeent on te perforane index for an aluiniu iroannel eat exanger IAENG ransations on Engineering enologies Volue 5 te Aerian Institute of Pysis (AIP) Vol pp [13].. Dang and J.. eng Effet of te substrate tikness of ounter-flow iroannel eat exanger on te eat transfer beaviors Proeedings of te international syposiu on oputer ouniation ontrol and autoation 010 aiwan 010 pp [14].. Dang J.. eng and J.C. Cu A study on te siulation and experient of a iroannel ounter-flow eat exanger. Applied eral Engineering Volue 30 Issue pp [15].. Dang and J.. eng Coparison on te eat transfer and pressure drop of te iroannel and iniannel eat exangers Heat and Mass ransfer Vol pp [16].. Dang and J.. eng e effets of onfigurations on te perforane of iroannel ounter-flow eat exangers An experiental study Applied eral Engineering Vol. 31 Issue pp IJCER Mar-Apr 01 Vol. Issue No Page 69

11 antrung Dang Ngotan ran Jy-tong eng /International Journal Of Coputational Engineering Resear / ISSN: [17] COMSOL Multipysis version 3.5 Douentation Sept 008 [18] S.G. Kandlikar S. Gariella D.Q. Li S. Colin and M.R. King Heat transfer and fluid flow in iniannels and iroannels. Elsevier 006. [19] J.P. Holan Experiental etods for engineers MGraw-Hill New York 1984 [0].. Dang J.. eng and J.C. Cu Influene of gravity on te perforane index of iroannel eat exangers - Experiental investigations Leture Notes in Engineering and Coputer Siene: Proeedings of e World Congress on Engineering 011 WCE July 011 London pp Jy-tong eng PD PE is a professor in te Departent of Meanial Engineering and te Senior onsultant of te Offie of International Affairs at Cung Yuan Cristian University (CYCU) aiwan. He is also te prinipal investigator of an international eduation enaneent progra sponsored by te Ministry of Eduation Republi of Cina. He reeived is BS in Meanial Engineering fro Montana State University MS and PD in Meanial Engineering fro UC Berkeley. His resear areas inlude tero-fluidi analyses of opartent fires and sokes nulear safety tero-fluidis of iroannels and teral anageent of eletroni devies. antrung Dang PD is a leturer in te Departent of Heat and Refrigeration enology and te Vie Dean of te Faulty of Autootive Engineering Hoiin City University of enial Eduation (HCMUE) Vietna. He reeived is BS and MS in te Departent of eral enology at Vietna National University Hoiin ity Hoiin ity University of enology (HCMU) PD in te Departent of Meanial Engineering Cung Yuan Cristian University (CYCU) aiwan. His ain resear interests are nano/irosale eat transfer energy and sustainable developent industrial refrigeration and air onditioning and energy eonois. Ngotan ran reeived is BS in te Departent of Heat and Refrigeration enology Ho Ci Min City University of enial Eduation (HCMUE) Hoiin City Vietna in 009. He eployed part tie for P.Dussann Vietna Co. Ltd as a Supervisor of Engineering fro 008 to 009 eployed full tie for P.Dussann Vietna Co. Ltd as a Manager of Laundry Fatory fro 009 to 010 and eployed for Darling Eletroni refrigerator Co. Ltd as a tenial diretor in 010. Presently e is a aster student at Departent of Meanial Engineering Cung Yuan Cristian University aiwan. He interested in studying on nano/irosale eat transfer energy and sustainable developent industrial refrigeration and air onditioning eletroni and ontrol syste engineering and energy eonois. IJCER Mar-Apr 01 Vol. Issue No Page 70