Author(s): Wesley Humphreys and Violet Gilfoyle

Abstract: Engine oil temperature above 130 °C accelerates oxidation, thins the lubricant film, and shortens bearing life yet compact-car oil coolers are typically sized for a single worst-case point, leaving their behaviour across the rest of the operating map largely uncharacterised. This research developed and validated a conjugate heat transfer (CHT) computational fluid dynamics (CFD) model of a 16-plate aluminium plate-fin oil-to-air cooler fitted to a 1.5 L turbocharged gasoline engine. The model was exercised across a 4 × 4 matrix of engine loads (25, 50, 75, and 100%) and ambient air temperatures (15, 25, 35, and 45 °C), producing 16 oil-outlet-temperature and cooler-effectiveness predictions. Experimental validation on a flow-bench rig at four representative operating points showed agreement within 2.3% on outlet temperature and 2.1% on effectiveness. Cooler effectiveness ranged from 0.724 at 25% load / 15 °C ambient to 0.612 at full load / 45 °C ambient a 15.5% drop driven primarily by the rising oil viscosity at elevated bulk temperatures, which suppresses the oil-side heat-transfer coefficient. The simulation revealed that at full load and 45 °C ambient the oil outlet temperature reached 133.4 °C, exceeding the 130 °C safe-operation limit by 3.4 °C, while at all other points it remained below 125 °C. A parametric sweep of fin density (10 to 18 fins per inch) and oil flow rate (±20%) identified that increasing fin density from 14 to 16 fpi reduced the critical-point outlet temperature to 127.8 °C comfortably below the limit at the cost of a 14.3% increase in air-side pressure drop. These findings give powertrain thermal-management engineers a validated simulation tool for mapping oil-cooler capacity across the full load-ambient envelope and a sizing guideline for hot-climate markets.

DOI: https://www.doi.org/10.22271/27078205.2026.v7.i2a.84

Pages: 32-36 | Views: 166 | Downloads: 63

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