Experimental study on the heat transfer characteristics of subcooled flow boiling with cast iron heating surface

• An experimental facility with cast iron was designed to produce boiling phenomenon.
• Some characteristics in flow boiling were obtained under specified conditions.
• Three types of original boiling models were utilized to correlate present data.
• A modified boiling model was developed to adapt to the cast iron heating surface.

Subcooled boiling is an effective heat transfer form for modern engine cooling systems. The significantly higher heat transfer rate achievable with boiling can keep the temperature in key thermal areas within an acceptable level and optimize thermal management strategies even at high engine loads. In this study, an experimental setup was designed using cast iron as heating block to simulate the flow boiling in engine cooling passage. The heat transfer characteristics were obtained under comprehensive cooling conditions for an engine, where the inlet temperature ranges from 75 to 95 °C, the system pressure ranges from 100 to 300 kPa, and the flow velocity ranges from 0.2 to 2.0 m/s. The experimental results were used to verify the wall heat flux of subcooled flow boiling in the cooling system of diesel engine, which was predicted by three types of empirical boiling models with primitive parameters. The results indicate that the prediction models are not accurate. Based on the experimental results and Franz's correlation, a modified boiling model was developed to adapt to the cast iron heating surface status.

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