DNMN Product Development Use of STAR-CCM+ for Heat Exchanger Product Development Gary Yu, Martin Timmins, Mario Ciaffarafa DENSO Marston Ltd. DENSO MARSTON LTD.
DNMN Product Development DENSO Marston Founded in 1904 Acquired by DENSO in 1989 Located in Shipley, West Yorkshire Designs and Manufactures engine cooling modules for Heavy Duty Cooling applications Product Range includes radiators, oil coolers, charge air coolers and condensers DENSO MARSTON LTD.
DNMN Product Development Background 1. Charge air cooler (CAC) is a typical fin-tube type cross flow heat exchanger; very fine mesh is required in CFD model to capture inner and external fin geometry features. 2. Further smaller mesh size is required to resolve thermal boundary layer. 3. Hundreds of millions of cells may be generated in CFD model for a conjugated heat transfer (CHT) study on a CAC of typical size in off-highway heavy duty vehicles. 4. Large computing resources will be required and therefore very inefficient. Tube Charge Inner Fin Air Core Depth Over Core Cooling Air External Fin DENSO MARSTON LTD.
DNMN Product Development Background 5. Can STAR-CCM+ single stream or dual stream heat exchanger model do the job? NO, it requires the input of test data and cannot be used for new product development. 6. An in-house program has therefore been developed and validated in DENSO Marston to build a virtual CAC prototype for prediction of heat rejection rate and pressure drop. 7. STAR-CCM+ has been used to find the key information of heat transfer and pressure drop in the new design. Tube Charge Inner Fin Air Core Depth Over Core Cooling Air External Fin DENSO MARSTON LTD.
DNMN Product Development Methodology 1. Use of STAR-CCM+ to study a very small section of inner and external fins to find heat transfer and pressure drop information. 2. Based on the information from Step 1, an in-house program using C++ is developed to build a virtual CAC prototype to predict the overall heat rejection rate, charge air core pressure drop and cooling air pressure drop. 3. Based on the charge air core pressure drop and overall heat rejection rate from Step 2, STAR-CCM+ single stream heat exchanger model is used to predict charge air pressure drop over tanks and core. 2 3 1 DENSO MARSTON LTD.
DNMN Product Development Why STAR-CCM+ IS Required? m , T , P , c c 2 c 2 c 2 Q , T , P , , T , P , 7 unknowns: m , T , P , m , T , P , h 2 h 2 h 2 c 2 c 2 c 2 h h 1 h 1 h 1 h h 2 h 2 h 2 Q cp m ( T T ) (1) h h h 1 h 2 Q cp m ( T T ) (2) m , T , P , c c c 2 c 1 c c 1 c 1 c 1 Q U A T (3) 1 L 2 c P f V (6) c c c c 2 D c 1 UA 1 A 1 A c c h h 2 1 L h (7) P f V T T T T h h h h 2 D h 1 h 2 c 2 c 1 T h 2 2 2 2 f F (Re ) , f F (Re ) 1 1 c c c h h h Nu F (Re ) , Nu F (Re ) c c c h h h Additional unknowns introduced: P P c Nu , Nu , f , f h (5) (4) c c h c h h RT RT c h CFD is used for the solution DENSO MARSTON LTD.
DNMN Product Development Determination of Computational Domain External fin Inner fin Periodic boundary condition Assumptions: 1. Flow is uniformly distributed between each fin loop: 2. Flow and heat transfer are same in each half external fin loop 3. Flow is periodic between each inner fin loop One loop of inner fin, 160 mm length, and half loop of external fin, 64 mm length, are modelled in CFD DENSO MARSTON LTD.
DNMN Product Development CFD Physics Model and Boundary Conditions T w T m in • Mass flow inlet, m • Temperature inlet, T in • Constant wall temperature, T w • Pressure outlet DENSO MARSTON LTD.
DNMN Product Development Results – Y+ Value Inner fin External fin 1. Pressure drop between inlet and outlet and residuals monitored for convergence check 2. Fin wall Y+ value checked to make sure near wall viscous sub-layer resolved DENSO MARSTON LTD.
DNMN Product Development Inner Fin and External Fin Heat Transfer Correlations Inner Fin Correlation: Nu v Re External Fin Correlation: Nu v Re D m D h h Nu , Re : fluid thermal conductivi ty A C m : mass flow rate; A : flow through area : averaged heat trans fer coefficien t C : fluid dynamic viscosity D : hydraulic diameter h DENSO MARSTON LTD.
DNMN Product Development Inner Fin and External Fin Pressure Drop Correlations Inner Fin Correlation: Friction Factor v Re External Fin Correlation: Friction Factor v Re 1 L m D 2 P f V h Re 2 D A h C P : pressure drop; f : averaged friction factor m : mass flow rate; D : hydraulic diameter h : density; V : velocity; L : fin length A : flow through area; : fluid dynamic viscosity C DENSO MARSTON LTD.
DNMN Product Development Numerical Program for Calculation of Core Pressure Drop and Overall Heat Rejection Rate 1. Discretise the heat exchanger core in hot flow direction by half of external fin loop pitch and in cold flow direction by one inner fin loop pitch. 2. Carry out heat balance and pressure drop calculation on each cell to get overall heat rejection rate and core pressure drop on both flow sides. Assumptions: 1. Flow rate is uniform across each tube and each fin loop. 2. Both fluids are ideal gas, no tube wall thermal resistance between hot and cold fluids. 3. No heat conduction along the tube in both flow directions. DENSO MARSTON LTD.
DNMN Product Development Numerical Program Output – an Example Core Pressure Drop and Overall Heat Rejection Rate DENSO MARSTON LTD.
DNMN Product Development Charge Air Total Pressure Drop (Tanks + Core) Outlet Tank STAR-CCM+ Inlet single stream Q Tank heat exchanger model Q In house program P over core DENSO MARSTON LTD.
DNMN Product Development Validation Against CAC A Test Data, Face Area 0.525 m 2 - Heat Rejection Rate and Cooling Air Pressure Drop Cooling Air Velocity m/s 4 6 8 10 o C Cooling Air Temp on 16.1 15.7 15.6 15.5 Charge Air Mass Flow kg/m 34.8 34.3 34.5 34.6 Charge Air Pressure In bar 1.9 1.9 1.9 1.9 o C Charge Air Temp In 184.4 184.0 183.4 183.0 Cooling Air P (Test) 100% 100% 100% 100% Cooling Air P (Prediction) 97.6% 96.5% 98.9% 102.1% Heat Rejection Rate (Test) 100% 100% 100% 100% Heat Rejection Rate 101.3% 100.3% 100.1% 100.1% (Prediction) DENSO MARSTON LTD.
DNMN Product Development Validation Against CAC A Test Data, Face Area 0.525 m 2 - Charge Air Pressure Drop Cooling Air Velocity m/s 2 2 2 2 o C Cooling Air Temp on 16.7 16.8 16.8 16.7 Charge Air Mass Flow kg/m 42.3 36.8 34.6 30.3 o C Charge Air Temp In 185.7 187.0 187.5 185.7 Charge Air Pressure In bar 1.9 1.9 1.9 1.9 Charge Air P (Test) 100% 100% 100% 100% Charge Air P (Prediction) 93.7% 99.3% 100.9% 106.9% DENSO MARSTON LTD.
DNMN Product Development Validation Against CAC B Test Data, Face Area 0.074 m 2 - Heat Rejection Rate Cooling Air Velocity m/s 8 8 8 8 Charge Mass Flow kg/s 0.35 0.30 0.25 0.20 o C Charge Mean Temp In 182.2 182.3 181.3 178.8 Heat Rejection Rate (Test) 100% 100% 100% 100% Heat Rejection Rate 98.1% 99.7% 99.2% 99.9% (Prediction) Cooling Air velocity m/s 4 6 8 10 Charge Mass Flow kg/s 0.26 0.26 0.25 0.25 o C Charge Temp In 181.9 181.5 181.3 181.0 Heat Rejection Rate (Test) 100% 100% 100% 100% Heat Rejection Rate 98.4% 99.3% 99.2% 100.8% (Prediction) DENSO MARSTON LTD.
DNMN Product Development Summary • An in house program has been developed to predict the charge air cooler (CAC) thermal performance based on heat transfer and pressure drop information obtained by two separate CFD detailed studies on CAC inner and external fins; • In the CFD detailed study, only a small section of external and inner fin (one inner fin loop, half external fin loop) is modelled; the accuracy of this study is the key to the CAC thermal performance prediction; • STAR-CCM+ single stream heat exchanger model is used to predict the charge air pressure drop over CAC tanks and core; • The developed methodology is validated against test results of two CAC units; DENSO MARSTON LTD.
DNMN Product Development THANK YOU DENSO MARSTON LTD.
Recommend
More recommend
