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Measurements are reported of heat transfer to a number of non-aqueous liquids that may be used as high temperature engine coolants. Included are engine lubricating oil, propylene glycol and LP 1693. The measurements were made with the coolants flowing at velocities ranging from 0.5-5 m/s in ducts similar in geometry to those employed in cylinder-heads and engine blocks. Heat fluxes up to 100 W/cm2 were used. For most tests the pressure drop across the test section was held constant but a number of tests are reported for constant coolant flowrate. The heat-transfer data obtained are shown to be in good agreement with predictions from the Chen correlation for flow-forced, sub-cooled nucleate boiling. This model is used to evaluate the heat-transfer performance of other non-aqueous coolants, namely ‘Thermex’ and ethylene glycol.

Measurements of heat transfer to water/ethylene glycol mixtures are reported for a range of coolant velocities (0.1 to 5.5 m/s) and heat fluxes (up to 140 W/cm2). At the highest velocities (3 and 5.5 m/s) forced convection was the dominant mode of heat transfer. At lower velocities, however, strong nucleate boiling occurred and at the lowest velocities dryout or vapour blanketing of the test section was detected. For most of the tests reported the pressure drop across the test section was held constant and the coolant flowrate adjusted accordingly. A number of tests are, however, reported for conditions of constant flowrate. The heat-transfer data obtained are shown to be in good agreement with a heat-transfer model that allows for forced convection and nucleate boiling.