Airside thermal-hydraulic characteristics for tube bank heat exchangers used to cool compressor bleed air in an aero engine

•The paper deals with bare and finned tube heat exchangers used for aero engine cooling.•The airside performance is predicted with consideration of air property variability.•The heat transfer coefficient and pressure drop are affected by the frontal air state.•The j and f factors are less dependent...

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Bibliographic Details
Published in:Applied thermal engineering 2018-08, Vol.141, p.939-947
Main Authors: Gu, L.D., Min, J.C.
Format: Article
Language:English
Subjects:
Aero engine cooling
Aerodynamics
Air temperature
Airside thermal-hydraulic characteristics
Bleeding
Compression ratio
Compressors
Cooling
Heat exchangers
Heat transfer coefficients
Hydraulics
j and f factors
Mathematical analysis
Mathematical models
Pressure drop
Temperature gradients
Thermal energy
Tube bank heat exchanger
Tube heat exchangers
Tubes
Turbine engines
Variable air property
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Summary:•The paper deals with bare and finned tube heat exchangers used for aero engine cooling.•The airside performance is predicted with consideration of air property variability.•The heat transfer coefficient and pressure drop are affected by the frontal air state.•The j and f factors are less dependent on the frontal air state.•Correction factors are proposed to modify the property variability effect on j and f factors. A numerical study has been carried out to investigate the airside heat transfer and pressure drop characteristics of bare tube bank and plain finned tube heat exchangers used to cool the compressor bleed air in an aero turbine engine. The exchangers use small diameter tubes (3.0 mm) with compact staggered tube layout and operate in high temperature circumstances with large temperature differences. Calculations are performed using the Realizable k-ɛ turbulence model with consideration of the air property variations caused by the air temperature and pressure changes. Calculations are implemented for 5–20 m/s frontal air velocities, 561–690 K and 0.5–1.0 MPa frontal air temperatures and pressures, which correspond to 15–30 compressor compression ratios, and 298 and 350 K tube wall temperatures. The airside thermal-hydraulic performance is evaluated using the heat transfer coefficient and pressure drop as well as their dimensionless forms - j and f factors. The results suggest that the heat transfer coefficient and pressure drop are strongly affected by the frontal air state whereas the j and f factors are less dependent on it. The effect of air property variability on j factor is limited while that on f factor is more notable.
ISSN:1359-4311
1873-5606
DOI:10.1016/j.applthermaleng.2018.06.033