1. Brandon Schulte Senior, Mechanical Engineering
Experimental Validation of Transient State Heat Transfer in Residential Attic Space
Brandon Schulte
Senior, Mechanical Engineering

2. Background
25% of household energy lost through HVAC equipment in attic space
Current modeling software (TRNSYS, DOE, Energy Plus, etc.) is used in industrial applications and does not account for attic spaces.
Dr. Ahmed Megri of the Civil Engineering Department developed 2 models to model residential attic space.
Research performed to collect data on attic space to provide comparison for theoretical model.

3. Model Dr. Megri’s model uses multi-zone and zonal methods
Intermediate approach between single zone and CFD
Two Models
Temperature distribution in attic
Interaction between attic space and HVAC system.
Thermal resistance and capacitance networks.

4. Model
RC-Network for attic space in transient state (Soleimani and Megri, 2008)
Model accounting for HVAC System, Megri (2001)

5. Temperature Measurements
Temperature measurements taken using Nickel-Nickel Chromium thermocouple
Voltage created between two dissimilar metals, linear relationship to temperature
Voltage is very small, susceptible to disturbances (table bumping, etc.)
Thermocouples connected to SCXI-1300 which is housed in SCXI-1000 power chassis and interfaced with PC.
LabView program ran on continuous loop, recorded temperature every 5 minutes.

7. Thermocouple Placement
Thermocouples placed according to model. Locations included attic, walls, mid-room stand, HVAC duct, and outside.
Mid-room stand included heights of 0.3 m, 1 m, 1.8m. At each height, globe temperature and exposed thermocouple.
Globe temperature includes effects of radiation.
Megri (2001)

10. Room
Description 1
East Wall, 1.0 m 2
S Wall, 1.0 m 3
N Wall, 1.0 m 18
Ceiling 26
Diffuser Air
Stand 4
0.3 m Air 5
1 m Air 6
1 m Globe 7
0.3 m Globe 8
1.8 m Air 31
1.8 m Globe
Attic 13
Attic Floor 14
Attic Roof, Surface 15
Attic Ceiling, Corresponding to 14 16
Mid Level, NW Ceiling 17
Duct Surface 19
Mid Level, SE Ceiling 20
Outside Air 24
Attic Air

12. Wind Measurements Wind measured in intervals of 2-4 hours
Wind measurements provide data on local environmental conditions
Wind data compared to Laramie Airport wind measurements.
Local wind generally same direction, less speed.
Other Measurements
Attic dimensions
Angle of attic ceiling to attic floor.
Ventilation (mechanical, natural, or none?)

15. Time
Wind Speed (m/s)
Direction
Wind Speed (mph)
1/5/2010
6:00:00 PM 4
SSW 15
6.73 SW
8:00:00PM W 17
7.62
10:20:00 PM
3.01 12
5.38
12:00:00 PM
0.75 18
8.07
1/6/2009
9:00:00 AM
1.05 NW 5
2.24
11:00:00 AM 3
2:00:00 PM
3.82 10
4.48
NNW
5:00:00 PM
0.53 11
4.93
8:00:00 PM
0.1 N 2
0.90
9:00:00 PM
0.68
2.5
1.12
1/7/2009
0.52 E
0.48
0.5
0.22 NE
12:50:00 PM
0.2
0.00 S
2:45:00 PM
0.45
0.39
6:20:00 PM
0.21 SE
8:30:00 PM
0.34
10:00:00 PM
1.35
1/8/2009
10:00:00 AM
12:30:00 PM
0.4
1:30:00 PM
3:45:00 PM
0.42
0.25
0.11
5:30:00 PM
0.62
6:30:00 PM
7:30:00 PM
1.32
0.24
1.13
1/13/2010
8:00:00 AM
9:30:00 AM
1.8
0.12
4:00:00 PM
0.38
0.82
0.94
1/14/2010
8:30:00 AM
1.5
10:30:00 AM
0.18
0.15
4:30:00 PM
0.46
0.31
10:30:00 PM
0.08
1/15/2010
1.31
0.04
5:15:00 PM
0.06

16. Conclusions Successfully modified LabView program .
Temperature and wind measurements taken over a week.
Sources of error
Dryer exhaust into attic
Occupied space (door opening, windows, oven, etc.)
Unexpected spikes in data due to sensitive thermocouples.
Data still under analysis
Improvements
Unoccupied household.
Stable module placement.

17. Questions?
References
Andrews, J., Field Comparison of Design and Diagnostic Pathways of Duct Efficiency Evaluation. Proceedings of the 1996 ACEEE Summer Study on Energy Efficiency in Buildings, Washington D.C.; American Council for an Energy Efficient Economy.
Greer, J., J. Fillo. Control of thermal runaway-some mathematical insights. International Journal of Heat and Mass Transfer, 1998, 41:
Megri , A.C., Soleimani, As., (2008) Computer-Based Analysis of Transient State Heat Transfer in Residential Attic Space, Roomvent 2009.