AUTOMOTIVE RADIATOR - DESIGN AND EXPERIMENTAL VALIDATION

Transcription

1 Internatinal Jurnal f Autmbile Engineering Research and Develpment (IJAuERD) ISSN Vl. 3, Issue 4, Oct 2013, 1-10 TJPRC Pvt. Ltd. AUTOMOTIVE RADIATOR - DESIGN AND EXPERIMENTAL VALIDATION PAWAN S. AMRUTKAR, SANGRAM R. PATIL & S. C. SHILWANT Department f Mechanical Engineering, Sinhgad Academy f Engineering, University f Pune, Maharashtra, India ABSTRACT In autmtive, radiatr is a base cmpnent f engine cling system. It extracts heat frm engine and keeps engine surface temperature at ptimum level fr better engine efficiency. Radiatr develpment cnsists f its size and design aspects. Size prvides heat rejectin area and its perfrmance. Design is related t its rbustness. This paper fcuses radiatr design validatin thrugh finite element analysis as well size and heat rejectin validatin by experimental test. KEYWORDS: Autmtive Radiatr, Heat Transfer, Simulatin, Sizing, Perfrmance INTRODUCTION Radiatr is a key cmpnent f engine cling system. Clant surrunding engine passes thrugh radiatr. In radiatr clant gets cled dwn and re-circulated int the system. Radiatr size is cntrlled by heat lad and packaging space availability. In this paper ε-ntu methd is described t d heat transfer calculatins and t decide radiatr size. Size is verified thrugh 1-D simulatin. HEAT TRANSFER CALCULATIONS Table 1: Heat Rejectin Requirement Air Flw Clant Flw Heat Rejectin Purpse f thermal analysis f heat exchanger is t determine heat transfer surface area (sizing) and perfrmance calculatin t determine heat transfer rate (rating). ε-ntu methd is based n cncept f heat exchanger effectiveness. [6] Here apprximate size is assumed accrding t space availability. Based n this size heat transfer rate is calculated which shuld fulfill the requirement. Radiatr size and heat transfer rate finalized accrdingly. Clant side heat transfer cefficient calculatins Mathematical expressins are taken frm references [1-3, 6] Hydraulic diameter Dhc = 4*Ait/Pit (1) Reynlds number Rec = (Vc*Dhc)/Sc (2) Prandtl number Prc = (Sc*Cpc)/Kc (3)

2 2 Pawan S. Amrutkar, Sangram R. Patil & S. C. Shilwant Nusselt number fr 2300<Re<10000 Nuc = [(Rec 1000)*Prc*(FF/2)]/{1.07+[(12.7*(FF/2) 1/2 *(Prc 2/3-1)]} (4) where Frictin factr FF = [1.58*ln(Rec) 3.28] -2 (5) Heat transfer cefficient hc = (Nuc*Kc)/(Dhc) (6) Heat transfer cefficient air Mathematical expressins are taken frm references [2,3,5,6] Hydraulic diameter Dha = 4*Cd*Ara/Aa (7) Reynlds number Rea = (Vaf*Dha)/Sa (8) Prandtl number Pra = (Sa*Cpa)/Ka (9) Clburn factr J = 0.174/Rea (10) Heat transfer cefficient ha = (J*Vaf*Cpa)/Pra 2/3 (11) Heat rejectin calculatins Mathematical expressins are taken frm references [1,3,5,6] Factr t calculate fin efficiency F = [(2*ha)/(Kf*Thf)] 0.5 *(Fh/2) (12) Temperature effectiveness f fins (fin efficiency) Ef = [TanH(F)]/F (13) Ttal surface temperature effectiveness f fins Eft = 1-[(1-Ef)*(Af/Aa)] (14) Overall thermal resistance R = [1/(Eft*ha)]+{1/{[(Ac/Cv)/(Aa/Cv)]*hc}}+(Tht/Kt) (15) Overall heat transfer cefficient U = 1/R (16)

3 Autmtive Radiatr - Design and Experimental Validatin 3 Stream heat capacity rate fr air Ca = Ma*Cpa (17) Stream heat capacity rate fr clant Cc = Mc*Cpc (18) Stream heat capacity rate rati Cr = minimum f Ca r Cc/maximum f Ca r Cc (19) Number f transfer units NTUmax = [U*(Aa/2)]/minimum f Ca r Cc (20) Heat exchanger effectiveness E = 1-exp{[exp(-Cr*NTUmax 0.78 )-1]/(Cr*NTUmax )} (21) Ttal heat transfer rate Q = E*minimum f Ca r Cc*(Tic-Tia) (22) Heat Rejectin Summary Table 2: Heat Rejectin Analytical Results Air Flw (m/s) Clant Flw (L/min) Heat Rejectin (kw) VERIFICATION OF HEAT TRANSFER AREA THROUGH 1-D SIMULATION Cling system is mdeled as shwn in Figure accrding t fllwing steps: Heat surce is selected as a radiatr. Cre dimensins specified. Input and utput ndes set fr air and clant inlet and utlet parameters. Air and clant flw directin given thrugh netwrk lines. 50% / 50% water and ethylene glycl clant is selected accrdingly its therm-physical prperties like inlet temperature, viscsity, density etc. prescribed. Similarly fr air therm-physical prperties given. Figure 1: 1-D Simulatin Cling System Mdel

4 4 Pawan S. Amrutkar, Sangram R. Patil & S. C. Shilwant Simulatin Results Size = x 665 x 60 mm3 [Fin Density 950 fins/cm] Table 3: Heat Rejectin Simulatin Results Air Flw Clant Flw Heat Rejectin Heat exchanging surface is verified and it seems enugh t achieve required heat rejectin. RADIATOR MODELING Fllwing pints taken care during design f Tank Strength Flw Optimizatin Installatin Space Cst As radiatr tank has t take all mdule weight, it needs t be rbust in design t sustain lad at the same time capable t sustain internal pressure. Figure 2: Radiatr 3D Mdel FINITE ELEMENT ANALYSIS FE analysis was perfrmed t check the stress and accrdingly design mdificatin fr rbust structure. An acceptance criterin is stress level belw 60MPa. Table 4: FEA Gemetry Cmpnent Part Material Radiatr Header Aluminum Tanks PA66-GF30% Tubes Aluminum External Fin Aluminum Munting bracket Steel Islatr Rubber Bundary Cnditins The mdel is fixed at left and right tank at the munting pints as shwn belw.

5 Autmtive Radiatr - Design and Experimental Validatin 5 FEA Result Figure 3: FEA Bundary Cnditins Table 5: Maximum Stress Lad Case (2 Bar) Open Case Clse Case Right Tank 52 MPa 53MPa Left Tank 13 MPa 13 MPa Figure 4: Maximum Stress Frm abve FEA results, tank design passes stress level s this gemetry is cnsidered t be k. TESTING AND VALIDATION Prttype Heat Rejectin Test Equipments used: Figure 5: Prttype Test bench Measuring equipment t measure clant and air side mass flws, inlet and utlet temperatures Clant-side inlet and utlet frames with ring ducts Munting blts fr cnnectin t test stands and cnnectins r ducts

6 6 Pawan S. Amrutkar, Sangram R. Patil & S. C. Shilwant Testing Wrkbench Prcedure Figure 6: Test Set Up This prcedure is applied fr preparatin, supervising and evaluating measurements at test stands fr determining clant and air-side perfrmance. Test is perfrmed at radiatr assembly level. A visual check is made f the radiatr: any damage at fins, brazed jints, cnnectins is checked. Full cre matrix is expsed t air flw. Test Cnditins 50/50 clant 80+/-10 C inlet clant temperature 20 C inlet air temperature Clant t air heat rejectin balance is kept within 3% fr each test pint. Clant side heat rejectin results recrded. Air inlet end temperature measuring pints are distributed unifrmly ahead f the radiatr cre. The first measuring pint is recrded after tw minutes in the steady state cnditin, accrding t the equilibrium criteria defined fr Clant inlet temperature, Clant inlet velcity, Air inlet temperature, Air mass flw rate. Testing Results Sample 1 Table 6: Testing Result Sample 1 Air Flw Clant Flw Heat Rejectin Sample 2 Table 7: Testing Result Sample 2 Air Flw Clant Flw Heat Rejectin

7 Autmtive Radiatr - Design and Experimental Validatin 7 Sample 3 Sample 4 Table 8: Testing Result Sample 3 Air Flw Clant Flw Heat Rejectin Table 9: Testing Result Sample 4 Air Flw Clant Flw Heat Rejectin RESULTS & DISCUSSIONS Fur 60 mm deep, U-flw, radiatr with having fin density 95fpdm and 34 tubes were tested fr heat perfrmance. The tested radiatrs have similar heat perfrmance. At all air flws, the heat-transfer is similar t the expectatin. Results btained cnfirmed design f radiatr fulfills perfrmance requirement and hence cmply level f acceptance. Cmparisn f Analytical, Simulatin and Experimental Perfrmance Results Figure 7: Cmparisn f Analytical, Simulatin and Experimental Results There were sme assumptins made in analytical calculatins like unifrm clant flw thrugh tubes, unifrm temperature f clant and air thrughut etc. s the analytical values are at higher than simulatin and experimental values. As in practical cnditins prperties f air and clant may differ frm pint t pint. Temperature f clant is changing thrughut the cre which affect heat transfer rate. Analytical values prvide safer side radiatr design as actual vehicle running cnditins are unpredictable. CONCLUSIONS The heat transfer perfrmance f the radiatr is analyzed fr theretical, simulatin and experimental values. FE Analysis result shws radiatr design is safe and stress level bserved is belw maximum stress criteria. Perfrmance test result shws radiatr is able t deliver required heat rejectin. Simulatin results are gd apprximatins f the tested

8 8 Pawan S. Amrutkar, Sangram R. Patil & S. C. Shilwant values fund experimentally. The bjective t design and validate the radiatr is accmplished successfully. FUTURE SCOPE Currently autmtive industries use iteratin methds t predict radiatr perfrmance in develpment phase. T develp cre blcks f certain vlume with cmbinatins f different standard tubes and fins. Test the blck fr perfrmance result fr specific clant and air supply. Blck vlume is integrated t btain perfrmance values fr particular cre size and then result is validated thrugh actual test measurements. These results data is incrprated in simulatin sftware and then it will integrate values ver any defined cre size and will give perfrmance values. All such cre cmbinatin blcks results will be useful in develpment phase t get perfrmance values and iteratins will be reduced as these values are already validated. Nmenclature A: Ttal heat transfer area Ar: Free flw area Ai: Inside crss-sectin area Pi: Inside perimeter Fh: Fin height G: Density Cl: Cre length Cd: Cre depth Cw: Cre width Cv: Ttal vlume f cre Nt: Number f tubes Ntr: Number f tube rws Dh: Hydraulic diameter Th: Thickness K: Thermal cnductivity FF: Frictin factr F: Factr t calculate fin efficiency Q: Ttal amunt f heat transfer E: Effectiveness f heat exchanger

9 Autmtive Radiatr - Design and Experimental Validatin 9 Eft: Ttal surface temperature effectiveness f fin Ef: Temperature effectiveness f fin C: Heat capacity rate Cr: Heat capacity rate rati Ti: Inlet temperature T: Outlet temperature NTU: Number f transfer units M: Mass flw rate W: Vlume flw rate Cp: Specific heat U: Overall heat transfer cefficient R: Overall thermal resistance h: Heat transfer cefficient Nu: Nusselt number Re: Reynlds number Pr: Prandtl number V: Velcity Vaf: Air mass flw velcity S: Dynamic viscsity J: Clburn factr Subscripts: c: Clant a: Air t: Tube f: Fin REFERENCES 1. Matthew Carl, Dana Guy, Brett Leyendecker, Austin Miller, and Xuejun Fan, The Theretical and Experimental Investigatin f the Heat Transfer Prcess f an Autmbile Radiatr, ASEE Gulf Suthwest Annual Cnference, Texas, R. Esmaeili Sany, M. H. Saidi, J. Neyestani,Experimental Predictin f Nusselt Number and Clant Heat Transfer Cefficient in Cmpact Heat Exchanger Perfrmed with ε-ntu Methd, The Jurnal f Engine Research, Vl.18, Spring, 2010

10 10 Pawan S. Amrutkar, Sangram R. Patil & S. C. Shilwant 3. K.Y. Leng, R. Saidur, S.N. Kazi, A.H. Mamun, Perfrmance investigatin f an autmtive car radiatr perated with nanfluid-based clants (nanfluid as a clant in a radiatr), Applied Thermal Engineering,30, S. K. Saripella, W. Yu, J. L. Rutbrt, D. M. France, Rizwan-uddin, Effects f Nanfluid Clant in a Class 8 Truck Engine, SAE Technical Paper, 2141, D. Ganga Charyulu, Gajendra Singh, J.K. Sharma, Perfrmance evaluatin f a radiatr in a diesel engine- a case study, Applied Thermal Engineering 19, S. Kakac, H. Liu, Heat Exchangers Selectin Rating and Thermal Design, (CRC Press LLC, 1998) 7. Pawan S. Amrutkar, Sangram R. Patil, Autmtive Radiatr Perfrmance Review, Internatinal Jurnal f Engineering and Advanced Technlgy (IJEAT), ISSN: , Vlume-2, Issue-3, February P. S. Amrutkar, S. R. Patil, Autmtive Radiatr Sizing and Rating Simulatin Apprach, IOSR Jurnal f Mechanical and Civil Engineering (IOSR-JMCE, ISSN(e) : , ISSN(p) : X, 2013