Group Re-Tested Crossflow Ventilation methods against a reference vehicle which had no ventilation and set out to determine which of the two would provide the greatest difference in temperature as the day progressed.
Test Setup :
As before, two power supplies were placed in the back seat to provide power to the fan arrays. These were powered via an extension cord run through the window.
Figure 1 : Power Supplies in Rear of Test Vehicle
We used a test vehicle which contained the fans and temp sensors as well as a reference vehicle used with no ventilation and the windows up in order to provide a basis for potential temperature difference between the ventilation methods.
Figure 2 : Test Vehicle (2012 Kia Soul)
Figure 3 : Reference Vehicle (2011 Hyundai Elantra Touring)
Temperature Sensors were placed at the "1" (driver seat) and "2" (back seat driver side) positions of each of the vehicles doing our best to keep them out of direct sunlight.
Figure 4 : Sensor Locations (Test Vehicle Top, Reference Vehicle Bottom)
Fan arrays were placed in the window of the test vehicle to enable a cross flow of air across the interior of the vehicle. For Day 1, the cross flow was not optimized in order to create a clear difference in apparent cooling should it exist. Intake fans were placed within the back passenger window facing the sun and exhaust windows were placed facing out of the supposedly coolest part of the vehicle in the back seat driver side window.
Figure 5 : Non-Optimized Fan Orientation
For Day 2, cross flow was optimized by reversing the orientation of the fans from Day 1. The intake fans were placed in the back seat driver side window and the ventilation fans were placed in the hottest portion of the vehicle, which is the back passenger side window.
Figure 6 : Optimized Fan Orientation
Fans were run from 12:00pm to 5:00pm. Temperatures were recorded hourly starting at 1:00pm. The external temperatures of the test vehicle were recorded at each of the windows. The internal temperatures of the front and back, and the surface temperatures of the dashboard, front seat, and back seat were also monitored. The weather was noted at each hour. Results were tabulated in an excel spreadsheet for analysis.
Results :
Day 1 : High of 82°F and Mostly Sunny (Clouds appeared between 3:00pm and 4:00pm)
Temperature within the vehicle predictably rose to well over 100 degrees within the first hour. As the day progressed, the average temperature in the test vehicle was around 108 degrees with the reference vehicle being around 114 degrees. It should be noted that at 3:00pm the rear sensor in the reference car was exposed to direct sunlight causing the temperature reading to be higher than expected. Surface temperatures were also high with the reference car having lower surface temperatures on average. This is attributed to the material of the reference vehicle's upholstery being of a lighter shade than that of the test vehicle.
Table 1 : Temperature Readings from Day 1 (Non-Optimized Crossflow)
Figure 7 : Graphs of interior air temperatures for both vehicles on day 1. The left graph shows measurements for front and back over time. The right graph gives an average of the front and back over time.
Day 2 : High of 84° and Sunny (NO Clouds appeared throughout the day)
Internal temperatures rose to well over 100 degrees within the first hour. As the day progressed, average temperature in the test vehicle was around 112.5 degrees with the reference vehicle average rising to a staggering 122 degrees. Throughout the day, no clouds appeared which would decrease the exposure to the sun which was experienced by either the test vehicle or reference vehicle. Surface temperatures for the test vehicle on this day were lower than the reference vehicle by 0.5 degrees.
Table 2 : Temperature Readings from Day 2 (Optimized Crossflow)
Figure 8 : Interior temperatures in both vehicles on day 2.
Results are tabulated and charted in the Excel Spreadsheet below.
https://docs.google.com/spreadsheets/d/1VM-coa3N81jQjGFTt0Mwa1SzHctvef_VwttN8Ikxnys/edit?usp=sharing
Conclusion :
The overall increase in temperature on Day 2 was expected due to the higher ambient temperature and the constant exposure to direct sunlight that did not occur on Day 1. The average internal air temperature difference on Day 1 using non-optimized airflow ventilation was 6.1 °F. On Day 2, this difference jumped up to 9.5 °F by simply re-orienting the fans to optimize airflow from the coldest part of the car to the hottest. Thus, optimized crossflow provided 55% more cooling than non-optimized crossflow. Surface temperatures on Day 2 were also lower than expected. Despite its darker upholstery material, the test vehicle yielded surface temperatures with an average of 0.3 °F cooler than the reference vehicle. On Day 1, the test vehicle surface temperatures were on average 2 °F hotter than those of the reference. The results show that optimized crossflow is likely worth pursuing as a cooling method for the project.
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