Calculating the Conductive Coefficient of Acrylic Plastic Can we actual use the stuff Dr. Solovjov taught us? Nathan Rhead Mike Tricarico

Introduction Problem: What is the conductive coefficient of acrylic plates used in a wind tunnel? Objectives: Can we assume the plate is adiabatic? We want to design a wind tunnel using a material that will have a high enough k to keep the temperature on the bottom of the wind tunnel constant for at least five minutes. This will allow us to research transient thermal effects on various geometries.

Problem Setup—getting the temperatures Plot of thermocouple outputs v. time Temperatures after 2 hoursTemperatures after 15 min.

Problem Setup Thermocouple “sandwiched” between plates Air u ∞ = 18 m/s T ∞ = 54° C T = 36° C Ts = 49° C *All temperatures measured by thermocouples k= ?

Problem Solution 2 hours15 minutes

Results The average conductive coefficient, k=0.868 W/mK This met our expectation. The calculated value of k changed between 15 min and 2hrs because we allowed the wind tunnel to come closer to steady state temperature.

Conclusions and Recommendations This low k value means that acrylic is an appropriate material that will insulate the wind tunnel and allow for measuring transient responses and treating the wall as adiabatic. Acrylic also has the necessary property of being transparent! Increasing L would further decrease the heat loss through the walls of the wind tunnel.

Appendix