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In this paper, a theoretical model for the calculation of Specific Dissipation (SD) was developed. Based on the model, the effect of ambient and coolant radiator inlet temperatures on SD has been predicted. Results indicate that the effect of ambient and coolant inlet temperature variation on SD is small (less than 2%) when ambient temperature varies between 10 and 50°C and coolant radiator inlet temperature between 60 and 120°C. The effect of coolant flowrate on SD is larger if there is a larger flowrate variation. Experimental results indicate that a 1 % variation at 1.0 L/s will cause about ±0.6% SD variation. Therefore the flowrate should be carefully controlled.

The sensitivity of cross-winds in reducing the engine cooling ability in motor cars is highlighted. Tests on three different motor cars were conducted in the Monash University full-scale wind tunnel at different yaw angles under different wind velocities. The test results show that motor car engine cooling capability decreases with an increase in yaw angles. For a wind velocity of 14 m/s, a 13% decrease in radiator cooling capability was found at a yaw angle of 20° compared to a zero yaw angle. The effect of yaw angles on the engine cooling also depends on the motor car front-end configuration, but this becomes less important with increasing wind velocity. The effect of cross-winds on car engine cooling was also evaluated by on-road engine cooling tests. A convenient experimental method to measure wind velocity and yaw angle relative to a moving car is also described.

This paper presents an experimental comparison between two factors used for evaluating engine cooling in motor cars, Air-to-Boil (ATB) and Specific Dissipation (SD). It is shown that Specific Dissipation can increase the experimental productivity for evaluating cooling system by giving more reliable results than Air-to-Boil. Results from road tests and experiments conducted in three different wind tunnels are presented. All experimental results indicate that Specific Dissipation gives more repeatable results and can be used in both stable and slowly-varying test conditions.