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Vital Signs
Project: Waverley Mansion
(Background) (Methodology)
(Building Results) (Model
Results) (Conclusion) (References).
This study focuses on increased indoor air movement due to the stack effect in the four-story atrium. Because Waverley Mansion has changed since the time of its construction, we concluded it was valuable to build a physical model of Waverley in its original form. This allowed us to conduct tests on both the actual building and the model, and to then compare the results. Testing Waverley The BuildingMethods All tests were performed on Saturday, November 24, 1996. Test results are dependent on the ambient temperature, humidity, wind speed, and wind direction for that day. One goal of this study was to use testing devices easily obtainable by students so that they may conduct similar tests for other case studies. The equipment used to test the stack effect included two thermometers and an electronic thermocouple. The thermometers were purchased from a local merchant for little cost and were equipped to measure both dry bulb temperature and relative humidity. Humidity is important in Mississippi because increased indoor humidity decreases perceived comfort. Because the thermometers were only accurate to within two degrees for measuring dry bulb temperature, it was necessary to borrow a hand held thermocouple from the university's mechanical engineering department; its accuracy was within 1/5 of a degree.
One thermometer was placed outside away from the house and out of direct sunlight. The other was placed inside on the first floor, also out of direct sunlight (Fig.6). Because water vapor is heavier than air, it was assumed that any water vapor which entered the house with the ambient air would fall to the first floor. Therefore, all humidity readings were taken at ground level. The electric thermocouple was used to measure dry bulb temperature at each floor level and half way up the stairs between each floor level. Temperature and relative humidity measurements were taken every 30 minutes from 12:30 P.M. to 4:30 P.M.
In order to detect changes in air flow, a pinwheel design was developed and 10 pinwheels were constructed. The pinwheels were constructed using graph paper (1/4 inch grid), 1/8 in. x 1/8 in. balsa wood sticks, and stick pins. The graph paper was chosen because it was light, rigid, and lined for quick and accurate replication of the pinwheels. First, the paper was cut into 2-1/2 inch squares (Fig.7.a). A one-inch cut was made from the midpoint of each side toward the center (Fig.7.b). Next, the paper was folded from the midpoint of each side toward the center (Fig.7.c). The same fold was repeated on the opposite side of the paper, and a hole was punched in the center of the pinwheel (Fig.7.d). Each pinwheel rotated around a stick pin stuck in a four-inch length of balsa wood. Figure 8 is a picture of a finished pinwheel.
The pinwheels were suspended at one foot increments along 16 foot long strands of fishing line. Four strands of fishing line (60 pinwheels) were stretched across both fourth and third floor levels. Two strands (30 pinwheels) were stretched across the second floor level; more pinwheels were used at the upper levels in anticipation of more changes in air motion at those levels. Figure 9 shows the pinwheels suspended in Waverley's atrium.
Waverley was tested under the following four conditions:
The greatest amount of time was devoted to condition three because it was believed to be the condition under which passive cooling would be most successful.
A video camera was used to document the motion of the pinwheels under each condition. Since most of the observations on air movement were made under condition three, fifteen minutes of pinwheel activity was filmed on each floor between 1:00 P.M. and 4:00 P.M. |
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author: vitalsigns@ All contents copyright (C) 1998. Vital Signs Project. All rights reserved. Created: 04/08/97 |
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Figure 6: Thermometer and Relative Humidity Gauge.
Figure 8: Pinwheel used to detect changes in air motion.
Figure 9a: Pinwheels in the Waverley Mansion atrium.
Figure 9b: Pinwheels in the Waverley Mansion atrium.
Figure 9c: Pinwheels in the Waverley Mansion atrium.
