“Give’em the Heater, Vaughn”
– Major League
As you can see from the solid purple line, besides a slight dip on the 31st to a cool 97ish, the rest of the week stayed a balmy 99 to 105. Which was nothing compared to the 140 to 152 degrees the roof and West side walls felt.
What was also fun to watch was the repeated double hump the red line would create each day, the second about 10 degrees cooler than the first, but a hump nonetheless. Where it left off, the green line would pick up and climb out to its peak by an hour or two after mid-day but then plummet 60 to 70 degrees as the sun began to set.
The Beagle’s onboard sensor also was a surprise. Skyrocketing to almost as hot as the container’s skin and hardly ever going below 90 degrees except way after dark. Maybe we need to think about a heat-sink and/or fan again. A part of me also wants to see how much the little guy can take before it melts itself. The same part of me that compelled my brother and I to strap bottle-rockets and fire crackers to balsa wood airplanes with really long fuses. Anyone can spend dozens of our hours building a model airplane only to be brought to tears after its first crash or after the dog got its teeth into it. No, we wanted to see how our creations would fair 50 feet up as the “German flak” took its toll. Ah, what Texas kids do for fun in the summer.
The chart above is titled thru the 5th but in reality it’s just until the start of the day. Here’s a zoomed in version of August 5th spread out horizontally to show us some detail. The morning started cloudy with a little rain but then the clouds cleared around noon with a few more coming in again just after 1300. Once those clouds left by 1400 the sun was back to full force and the 120 to 135 degree metal temperatures resumed.
Now, unless I’d remembered that we’d had clouds with a little rain there’s no way to know what caused those 60 and 70 degree temperatures. A cold front? A down pour? I’d left the doors open for 6 hours? A digital rain gauge is over-kill but measuring the amount of sunlight would be helpful.
Observations
- Internal temperatures (dotted purple line) are very dependent on skin temperatures.
- External ambient provides very little in the way of heating or cooling of the metal skin. Although it provides the “baseline” temperature of the metal, it’s the direct sunlight on the metal that contributes the majority of the heating. Maybe shading with some airflow can provide a little relief.
- Despite ambient temperatures of 90+ degrees, even a partly cloudy day can drop the metal’s temperatures dozens of degrees.
Questions
- How much cooling would painting the roof with reflective white paint provide?
- Again, is the side heating a moot point if the container is oriented East-West instead of North-South?
- Would just shading the West wall do enough to keep the container’s temperatures down?
- How much does the suns energy actually contribute to the metal’s heating?
Time for a solar cell
See y’all next week with a solution to monitor how much direct sunlight is contributing to the metal’s heating.
Thales of Miletus 