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# From Thermodynamics

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I have created a hot box and heated the inside to 140 degrees Farenheit. The hot box has 5 stationary walls (17 inches by 17 inches) made out of
2 inches of polyisocyanurate.
The rated R-value of this material is 13.1. The 6th wall (actually the top) I can take on and off. I have run 3 experiments for 30 minutes (1800 seconds)
each.  The first experiment I ran with the 2 inches of polyisocyanurate. The change in temperature was 38 degrees Farenheit.

Question 1: what is my calculated R-value?

I ran this same experiment with the top being  3.5 inches of air.  The starting tempature was 140 degrees farenheit and the change in tempature was
45 degrees farenheit.

Question 2:  what is my calculated R-value for air?

Finally I ran this with 2 inches of polystyrene and 1.5 inches of air. The starting tempature was 140 degrees farenheit and the change in tempature was
43 degrees farenheit.

Question 3:  what is my calculated R-value fo the poltystyrene?

I have used both q= m c delta T and Newton’s law of Cooling … and I cant seem to get numbers that make sense. Please include all calculations

(Posted by RuthAnne)

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