I used heat flux pads to measure the heat flux between an animal and the substrate below. However, the animal's behaviour meant that it was only possible to place the pads between animal and substrate for a limited period of time. As a result, the curves created from the pad's readings appear to still be 'settling', (slightly increasing or decreasing). I believe this could be overcome by repeating with slightly thinner pads in the field, but unfortunately this is not possible at this time.
I was looking for suggestions on the extraction of data from this from anyone who might have worked with heat flux previously or others. So far I have tried some curve fitting to attempt to estimate the final values, but none has looked good.
For instance, how settled must the line be before it is a good estimation of actual heat flux? Can anyone suggest a good curve fitting method for estimation of the final settled value?
See attached for example curve (green and blue show temperature of substrate and animal surfaces, respectively, with red showing the resultant heat flux; black shows heat flux between the dorsal side of the animal and air).
Many thanks,
Tom
I do not know any details of the heat transfer between the animal and the pad, however , due to the nature of the heat equation, I would use exponential fit in a form y(t)=a+b*exp(-c*t) . Before fitting the data I would discard some initial data in order to fit mainly the assymptotic behavior of the system (or one can add another exponential term). The constant "a" is the seeked estimation of the steady state heat flux.
I tried to fit the data and it seems that the two exponential model approximates the data much better than the simplest model I proposed in the previous post. The data and the models are in the figure.
Not a problem; if the dog is inside. Only 2 heat pathways long wave radiation from the dog and long wave ration from the floor;ceiling; and walls.
Qa (dog) = ∈σ(°C + 273.3)4 Qa (Wm-2)
∈ = 0.98 (emissivity)
σ = 5.673 x 10-8 Wm-2°K-4
°C = the average of 3-5 temperature measurements on surface of the dog
Same equation for the heat coming from the room except for °C
°C = the average of the surface temperatures foor-walls-ceiling
You can also measure insulation with these measurements
V.A. Langman, S.L. Langman, and N. Ellifrit. 2015.Seasonal Acclimatization Determined by Non-Invasive Measurements of Coat Insulation. Zoo Biology 34: 368–373 (2015)
The equations will give heat from animal and room. Hope it helps;
V.A. Langman, Ph.D. Specialist Biophysics; Center for Animal Welfare, Beacon Facility mailstop 1180, 2312 E Bannister Road, Kansas City, MO 64131
Many thanks for the usefl responses
Jiří, thanks for fitting the example data, it looks like that equation will be well worth trying on the rest of the data.
Vaughan, unfortunately the dog has been left outside on a windy, partially overcast night and its hairless to boot! So radiation to the night sky and forced convection will also play a role I believe? Happily I have some recordings to calculate both, so will see how I get on with the final model!
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