FORS-2106EL Lecture 8: FORS-2106 - Day 8
27 Jun 2018
School
Department
Course
Professor
Forensic Biology - Day 8 2017.10.19
Scene Environment (Con’t)
-Every surface will be heated or cooled depending upon whether the energy budget
equation is positive or negative
-Positive = gaining energy
-Negative = losing energy
-Q* = (S(in) + L(in)) - (S(out) + L(out))
Stefan Boltzmann Equation
-Used to find L(out)
-β = θεT4
-β (beta) = the energy emitted from a black body in W/m2
-energy emitted from a body
-ε (epsilon) = emissivity
-θ (sigma) = 5.67 x10-8 W/m2K4
-T= temperature in Kelvin units
-Long wave emission from a clear sky
-Ld = 208 + 6Ta ( in W/m2)
-You can calculate long wave in and out, and then use the Q* equation above to find
the net energy lost or gained, both for shaded and sunlight
Bottom Line
-Any object that has mass emits radiation as a function of the fourth power of its
absolute temperature
-Simply: …
-A body be it at a surface heated by the sun, alive or dead, is going to lose or gain
heat, depending on
-Its energy balance (Q*) and hence the temperature of its surface
-The ambient temperature
-A gradient in temperature from, or to, the body core to the periphery according to
Fick’s diffusion equation
-The greater the gradient, the greater the driving force for heat gained or lost
-We also have to consider characteristics of the medium through which heat is
diffused and that is defined by the thermal conductivity
-Dense bodies tend to conduct much better then less dense bodies (gases)
-The body, at least in the early stage of decomposition can be crudely considered as
a bag of water and loss from the core of the body to the outside will be governed by
the thermal conductivity of water (0.58 W/m/k)
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Document Summary
Every surface will be heated or cooled depending upon whether the energy budget equation is positive or negative. Q* = (s(in) + l(in)) - (s(out) + l(out)) (beta) = the energy emitted from a black body in w/m2. Long wave emission from a clear sky. Ld = 208 + 6ta ( in w/m2) You can calculate long wave in and out, and then use the q* equation above to nd the net energy lost or gained, both for shaded and sunlight. Any object that has mass emits radiation as a function of the fourth power of its absolute temperature. A body be it at a surface heated by the sun, alive or dead, is going to lose or gain heat, depending on. Its energy balance (q*) and hence the temperature of its surface. A gradient in temperature from, or to, the body core to the periphery according to.
