Wildfire temperature probe

About
This design project's objective is to create the third generation of the Wildfire temperature probe. The probe is buried in the ground before a wildfire passes over, and measures the temperature at different depths in the soil. This information is useful because the carbon released by the fire coats the soil and causes it to be water-repellent.

The driving characteristics for the probe are size and weight due to the fact that multiple units must be carried on site. Also, the size of the probe determines that size of the hole that needs to be dug to deploy the thermocouples.

Sponsor
The sponsor of this project is the USDA Forestry Service. Main contact: Pete Robichaud, probichaud@fs.fed.us

Outer Case Experiment


After running experiments with many different shapes and designs we ended up going with the dig and place method for ground installation. There were faster installation times during our experiments from the pound in wedge shape and the screw shape. However, neither of these designs seemed like they would work well. The screw shapes main issue was turning up the soil around the case which wouldn't work well for the probes going into normally packed untouched soil. The wedge shape’s main issue was isolating the internal components from the force of being pounded in. After pounding in a wooden analogue to the case we realized that we were going to have to hit it too hard to keep from breaking it. Another issue with the wedge was not knowing how it affected the soil around it after it was pounded into the ground.

With the dig and place method chosen for the method of installation we then decided that the round cylinder shape for the outer case was the logical choice. With this choice the user would be able to use an auger or a post-hole digger to make a round hole to easily install the probe. Also, using a round digger with a non-round hole would make probe installation difficult.

Insulation Experiment
Insulation Experiment Info

First Fire Experiment
To understand what temperatures a stainless steel casing would see during a fire, a peace of 2.5" pipe was buried and a small fire built on top. Eight thermocouples were placed to measure the case and internal air temperature at different depths. This information will be useful in preventing the probe's internal components from heating past their operating ranges.



The data shows the the internal surface temperatures are higher then their outside counter parts. If the ground is treated as a heat sink that is the expected result. Also the lower into the ground, the lower the temperature, which is also expected since the heat source is above the ground.



Second Fire Experiment
Second Fire Experiment Info