up in smoke - analysis

ANALYSIS

Our experimental methodology was established to determine the rate at which the temperature decreased in the house under two different conditions.

We started by analyzing our results qualitatively, visually comparing the average cooling rate in rooms on the perimeter of the house during the fire and control trials. We also looked at the effects of the fire on those rooms adjacent to the fireplace. The difference in the slope of the first graph indicates that, overall, temperature in perimeter rooms decreased at a slightly slower rate during the fire trials than it did during the control trials. This result seems to contradict our hypothesis.

The data recorded for the outside temperature was taken from Weather Underground, which gives a single temperature record for Eugene, not specific to any particular area of the city.  It was very difficult to find two identical conditions.  During the two control trials the temperature remained close to constant.  The two fire trials took place during periods of greater temperature variation as well as slightly higher temperatures overall.

For the first fire trial and most of the second, the outdoor temperature difference was higher than it was during the control trials. On average, this lead to a lower indoor/outdoor temperature difference during the fire trials, which should have contributed to a faster rate of cooling for the control trials, since heat loss is product of temperature difference. Therefore, it is difficult to know for certain whether the slightly slower rate of temperature drop in perimeter rooms represents a refutation of our hypothesis, or simply the effects of a greater temperature difference.

To quantify the rate of temperature decrease in a simple statement we calculated the average time it took for each room to cool down 1 . This can be easily calculated by dividing the time period of the experiment by the change in temperature during that time.

We applied this calculation to the data from each temperature datalogger and then averaged the trials to give us an easy way to compare the two experimental conditions.

 
FIRE (trial 1)
FIRE (trial 2)
 AVERAGE
Datalogger/room
 Dt
(min)		 DT
()		 Dt/DT
(min/)		 Dt
(min)		 DT
()		 Dt/DT
(min/)		 Dt/DT
(min/)
1.  Living room A
240
9.07
26.46
240
3.48
68.97
47.71
2.  Living room B
240
2.07
115.94
240
0.69
347.83
231.88
3.  Bedroom 1
240
-4.81
49.90
240
-3.43
69.97
59.93
4.  Bedroom 2
240
-5.51
43.56
240
-5.51
43.56
43.56
5.  Bathroom
240
-5.50
43.64
240
-6.20
38.71
41.17
6.  Office
240
-3.44
69.77
240
-1.38
173.91
121.84
7.  Kitchen
240
-2.06
116.50
240
-3.44
69.77
93.14

 
CONTROL (trial 1)
CONTROL (trial 2)
 AVERAGE
Datalogger/room Dt
(min)		 DT
()		 Dt/DT
(min/)		 Dt
(min)		 DT
()		 Dt/DT
(min/)		 Dt/DT
(min/)
1.  Living room A
240
-5.50
43.64
N/A*
N/A*
N/A*
N/A*
2.  Living room B
240
-6.18
38.83
240
-6.86
34.99
36.91
3.  Bedroom 1
240
-4.80
50.00
240
-6.17
38.90
44.45
4.  Bedroom 2
240
-4.13
58.11
240
-6.87
34.93
46.52
5.  Bathroom
240
-7.57
31.70
240
-7.55
31.79
31.75
6.  Office
240
-2.06
116.5
240
-1.38
173.91
145.21
7.  Kitchen
240
-4.81
49.90
240
-5.48
43.80
46.85

*No data was recoverable from the datalogger

Summarizing the average data for the perimeter rooms gives us the following chart:

Datalogger/room CONTROL Dt/DT
(min/)		 FIRE Dt/DT
(min/)
3.  Bedroom 1
44.45
59.93
4.  Bedroom 2
46.52
43.56
5.  Bathroom
31.75
41.17
6.  Office
145.21
121.84

In the case of bedroom 1 and the bathroom we measured a slightly slower rate of temperature decrease while the fireplace was operating, a result that is at odds with our hypothesis. On the other hand, the finding of a slightly faster rate of temperature decrease in bedroom 2 and the office while the fireplace was operating is consistent with our hypothesis.

The overall much slower rate of decrease noticed in the office is likely due to the large amount of continuously operating computer equipment in that room. The increase in temperature in the living room demonstrates that the fire is able to effectively heat at least one room. On the other hand, the fire was unable to maintain temperatures in the kitchen, which is also adjacent to the fireplace.