Is there a performance difference between flat plate and evacuated tube collectors?

Question: Is there a performance difference between flat plate and evacuated tube collectors?
Conclusion: Evacuated tubes generate higher Delta T.

Weather Conditions: Crisp, sunny fall day, light to moderate breeze, no clouds, 60-64 degrees during test
Equipment & Setup: Single 50 gallon tank with single pump at 1 gallon per minute (gpm) to flow splitter Alternating flow between 4' by 10' flat plate and 30 evacuated tube heat pipe.

November 13th, 2010
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Conclusion: Evacuated tubes start btu production earlier, end production earlier, and offer greater delta "T" than flat plate collectors, given a sunny, cool fall day in Kansas.