While I was deciding on an appropriate brine, rub and injection for this years Turkey I was curious how closely a quick and dirty simulation would come to the reality of my smoker out on the deck? So while I was waiting for the bird to thaw I started modeling one up. Then, to calculate the fowl temperature versus time I used a 4 step process:
1. Gather Data and make Assumptions:
- I'm assuming homogeneous thermal properties.
- Assuming the majority of heat transfer is via convection not accounting for radiation.
- I'm modeling the turkey while cooking dinner so bones are not added. If anyone has a full 3D Turkey skeleton send it on over.
I found some thermal properties for meats here:
- Most of the standard material properties in Flow are temperature dependant however for this study I'm assuming conductivity and specific heat are basically constant in this temperature range.
- Assuming constant ambient temperature. When I get a second probe with recording capabilities I will try again with ambient temp(time). Ideally with the control system on the pellet smoker it's pretty consistent so it's not too big of an assumption.
Step 2. Create a Steady State Flow Simulation of the Smoker:
With Flow I used parametric studies to estimate inlet flow rate and temperature to create a steady state ambient temperature of 325F. I will use the ambient temperature and convection heat transfer coefficients from Flow rather than estimating them as boundary conditions in thermal.
|Cut Plot of Ambient Temperature in Flow|
|Heat Transfer Coefficient on Surface Note it is NOT uniform|
Step 3. Run transient thermal simulation:
The transient study was run in thermal analysis to reduce tun times. Running the full smoker model in Flow as a transient would take much longer to run. However we did use Flow to capture the non uniform convection which would be more difficult to apply in thermal.
|Transient Thermal Simulation Using Flow Convection|
Now you not may be able to tell from the picture but I was in the holiday "spirit" and forgot to save my temperature probe data from the Turkey.....
|author trying not to cut off a finger|
|Calibrating my model|
|Analysis Compared to Thermal Probe Temperatures over Time|
- Variation in ambient with time
- Possible variation of conductivity and specific heat with temperature
- Take into account rotating the Hens halfway the smoke.
I hope this give you some insight into the synergy between Flow and Sim Pro thermal and a basic understanding of the assumption that go into a thermal analysis.
Here's a link to some video of the simulations: https://youtu.be/rs7C9d6q6zM
Happy New Year!