Influence of Cowl Surface Temperature On Air Conditioning Load

A study of 8 current production vehicles revealed that the cowl surface were significantly heated resulting in an increased air temperature as it flows into the blower intake through the cowl.

Based on the wind tunnel data, the sheet metal cowl channel is heated up to 50∼63 °C at highway speeds and up to 85 °C at idle.

Hence, in OSA mode the ambient air is heated up by the hot channel surface as it travels from the cowl inlet to the blower unit that result in increasing the evaporator loads by significant levels, thereby, increasing the vent outlet temperature.

Tests were conducted by removing the cowl cover to determine the maximum potential of improvements (to prevent air from being heated up in the cowl channel). This resulted in improvements of the vent outlet temperatures from 2.5∼5 °C. This shows that significant improvements of the vent temperatures can be realized by improving design of the cowl to minimize heat pickup.

Finally, attempts were made to insulate the cowl of a few vehicles by using commercially available insulation. This significantly reduced the effective flow area of the cowl resulting in an increased pressure drop and noise level.