An-Gels of Insulation
|Sponsor||University of Idaho Mechanical Engineering Department|
|Advisor||Dr. Behnaz Rezaie|
|Duration||Fall 2017 - Spring 2018
|Team Name||An-GELs of Insulation|
The Northwest experiences cold harsh winters and hot dry summers. These weather conditions dictate a large demand for heating and cooling during various times of the the year. One proposed way of reducing the required power generation is to employ more effective insulation into buildings. Before an installation effort is made, the performance of different types of insulation must be measured and its thermal resistance obtained.
In 2015, about 40% of total U.S. energy consumption was consumed in residential and commercial buildings. Most existing buildings in the US were built before building energy efficiency was a concern, and most of these buildings will still be in use for quite some time. They are not built with energy savings in mind. It is of great interest to decrease their heat loss in the least intrusive and least expensive way possible. A probable, and perhaps inexpensive way to lower the heat loss of buildings is to retrofit them with improved insulation. The alternative is to overhaul a buildings HVAC network, which can be expensive and intrusive. This team aims to characterize the performance of various types of insulation.
Common insulation used in buildings are shown below in the table. 
|Glass Fiber||Glass fiber is a woven glass with extremely fine fibers. Most buildings int he United States use glass fibers for insulation. Typical R values range from 11 in low density fibers, to 21 in higher quality ones.|
|Mineral Wool||Contains of natural minerals such basalt or diabase. Commonly comes in blankets and is composed of 75% recycled content. It is flame resistant. |
|Cellulose|| Primarily composed of recycled newspaper. Can be used as a loose-fill insulation in building cavities. 
|Polystyrene||Themroplastics that is colorless and transparent. Used to make foam board insulation of beadboard insulation.|
|Aerogel||Aerogel is a lightweight, porous substance created by evaporating a solvent from a silica base. Aerogel contains around 50%-99.8% air while maintaining a rigid structure.The end result is a material that has very low thermal conductivity.|
Due to the low thermal conductivity and low density, aerogel appears to be an effective method of increasing the thermal resistance of a building. A previous study was implemented at the University of Kansas to investigate the effects of aerogel insulation in a simple panel versus a different form of insulation.  The results of their experiment indicated that heat loss could be lowered by about 16 percent of a more traditional polyester insulation. Other types of insulation are shown in the table. They each have various pros and cons that enable them to be used in different applications. Common applications include wall insulation, roof insulation, piping insulation, as well as other various equipment insulation.
Temperature gradients will be observed in a simulated room model using aerogel, R max thermosheath, simple carpet, and plywood. Hobo temperature sensors will be used to measure and record the temperature at several points both within and without the simulated wall.
Measurements will be taken in 5 second intervals. The beginning of the experiment will consist of lighting two simple candles within the box.
Once the candles have been verified to be lit, the box will be sealed. The box will have several air holes in order to provide enough oxygen for the candles to remain lit.
A waiting period of 30 minutes was used to allow the box to reach steady state conditions. Once steady state conditions were reached, the holes in the box were covered with aluminum tape.The tape cuts off the oxygen and extinguishes the candles. Another waiting period of 60 minutes was observed. During this time, the heat would leave the box. At the conclusion of the experiment, the data was plotted to establish a temperature profile over time. These temperature profiles were compared for the various insulation materials.
Curve fits were established using fitting commands within excel to generate an equation relating temperature versus time. The derivative of this empirical equation was then used to compare the time rate of change of temperature. The time rate of change of temperature provided inside on how quickly the temperature declined within the box for various materials.
The table below outlines the specification for the project. They define the type of equipment required and outlines the expectations of all parts of the project.
|Sensor Temperature Accuracy||+/- 1 Degree C|
|Data Logging Capability||Able to log and record reading every minute for 90 minutes, or duration of test.|
|Test Specimens|| All test insulation must be equal thickness, or as close to equal thickness as possible
|Temperature Measurement Locations||Temperatures will be recorded in three locations. One temperature sensor will record the ambient air temperature in the center of the box, Another temperature will be recorded on the inside of the walls and on the surface of the test insulation. A third temperature measurement will be taken on the surface of the box.|
|Model Material||Model will be constructed using plywood and 2X2 wood framing. The goal is to replicate a residential home as closely as possible.|
|Size of Model||Model will be a cubic structure with an internal volume of approximately 8 cubic feet.|
Shown below is a temperature versus time plot of aerogel and R max Thermosheath. The temperatures rise until steady state conditions are reached. Once the candles are extinguished, the temperature begins to decline towards room temperature. The rate at which this decline occurs is what is important. A slower rate of decline indicates that an insulation is better suited to keeping heat inside a space.
The maximum temperature was higher for the thermosheath than for the aerogel. This is likely due to fluctuations in candle output. Many other tests results in fairly different maximum temperatures. The ambient room conditions were constant for the most part. The different candle outputs can be rectified by analyzing data from within a common range of temperatures. For example, the maximum temperature reached in all tests was 100 degrees Fahrenheit, therefore the temperature decay from 100 degrees and below were used for analysis.
The internal wall temperatures were found to increase in temperature more quickly than the air inside the box. One possible reason is radiative effects from the light of the candle. The light from the candle hits the inside surface of the box where its energy is then absorbed and the surface warms. This effect is only temporary. Once steady state conditions are reached, the difference in temperatures between the walls and the box air become negligible.
Once the candles are extinguished, the wall temperatures are shown to decrease faster than the air temperature. This was expected due to the walls being exposed to a temperature gradient from the outside air. This temperature gradient drives heat from the higher temperature inside wall towards the colder air within the room. Heat from the air within the box then moves towards the walls.
To account for different maximum temperatures within the box, data was selected from 100 degrees and below. This allows for different types of material to be compared on a more equal footing.
Austin Anderson is a senior in mechanical engineering at the University of Idaho. His interests include thermal energy systems and power generation. Following his graduation in May 2018, Austin plans on attending the University of Idaho to earn his Masters of Science in Mechanical Engineering.
Cameron Moore is a senior in mechanical engineering at the University of Idaho. His interests are in clean energy resources and fluid mechanics. After graduation his goal is to obtain a job in either of these fields or possibly return to school to obtain a masters degree in Mechanical Engineering.
Nick Chen is a senior in biological engineering at the University of Idaho.
Yue Yu is a senior in electrical engineering at the University of Idaho.
- About Aerogel|url=http://www.zerogaerogel.com/aboutaerogel.html
- Evaluation of Aerogel Composite Insulation by Characterization and Experimental Methods|url=https://kuscholarworks.ku.edu/bitstream/handle/1808/18384/Chotangada_ku_0099M_13743_DATA_1.pdf;sequence=1