PASCO ET-8593 Energy Transfer Solar - Manual (Page 11)

Energy Transfer - Solar Model No. ET-8593
10 ®
Analysis
a) Find the slope of the line tangent to the curve at outside ambient air temperature. Do not
use the Slope Tool. Highlight a small section at outside ambient temperature. At ambient
temperature, the heating is only being caused by the sunlight. Below the ambient
temperature, the surrounding air is cooling the container. Above the ambient temperature, the
surrounding air is heating the container.
= change in temperature/change in time
b) Theory for heat flow
c)Using your slope and the other measured quantities, calculate the intensity of the sun's light.
The intensity (solar constant) at the top of the Earth's atmosphere is about 1400 Watts/m
2
. On
a good clear day with the sun high in the sky, you can get over 1000 Watts/m
2
on the surface.
For Further Study:
a) Compare the intensity at noon to later in the day.
b) Compare a clear day to a slightly overcast day.
c) Compare summer to winter.
slope
∆T
∆t
-------- =
where Q =heat, c=specific heat, and = change in temperature Q mc
∆T
= ∆T
Power
Q
∆
t
----- mc
∆
T
∆
t
------- = =
Intensity
Power
Area
-----------------
mc
∆
T
∆
t
-------
Area
--------------- = =
where is the slope of the graph.
∆T
∆t
-------