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The honeybee problem

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(1)

The honeybee problem

Mean body mass 75 mg Mean surface areas

head 27 mm2 thorax 80 mm2 abdomen 63 mm2 total 170 mm2

Metabolic power 640 mW/g

Flight mechanical power 27 mW/g

Tb=0.63 Ta + 19

- measurement of d[CO2]/

dt and d[H2O]/dt

- measurement of body temperature at different times

Body temperatures are independent of time Ta from 21 to 45°C

Thorax

Head

Abdomen

Roberts & Harrison, J. Exp. Biology, 202, 1523(1999) Surface weighted average body

temperature Tt=0.39 Ta + 29

Th=0.86 Ta + 14

Tab=0.83 Ta + 7

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The honeybee problem

What are the different mechanisms involved in heat exchange ? Write the overall heat balance

(3)

The honeybee problem

C is not measured but deduced from the overall heat balance

(4)

The honeybee problem II

Surface weighted average body temperature

Estimate the heat flux due to radiation

body surface emissivity εb 0.98

emissivity of the glass container εg 0.90

Tb=0.63 Ta + 19

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21 33 45

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The honeybee problem

How can we estimate independently the heat transfer from the bee to the air ? Is it dominated by diffusion or convection ?

If we evaluate an order of magnitude of this heat flux, is it consistent with the other measurements ?

Physical properties of air : density ρ 1 kg/m3

specific heat Cp 1000 J/kg.K

thermal conductivity λ 0.025 W/m.K

Références

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