Animals and their Environment
heat exchange in a convenient way and also linearizes the energy balance
equation. From Eq. (12.6) it is seen that
Values for gr (with E, set to 1) are tabulated in Table A.3 for temperatures
between -5 and 45°C.
With these changes and substitutions, the energy balance equation now
becomes:
where
Finally, making use of Eq. (12.3) to eliminate surface temperature the
energy budget equation for an animal is obtained in terms of body
temperature:
One final simplification allows the energy balance equation to be written in a particularly useful form. Animal metabolism is often studied
inside chambers where air and wall temperatures are equal, where the
flux density of shortwave radiation is negligible, and where wall emissivities are high. Such a chamber could be called a blackbody enclosure.
If the radiation balance equation (Eq. (1 1.14)) is looked at for an animal
in such an enclosure, it is seen that Rabs = E , O T ~ . We call the temperature of such a blackbody enclosure the operative temperature, with the
symbol Te. Later we relate the operative temperature to outdoor radiation
and temperature conditions, but for now the use of operative temperature
allows us to eliminate radiation terms from the energy balance equation.
The operative temperature form of Eq. (12. lo), with some rearrangement
of terms is:
The second equation, in resistance form, is the more familiar form, but
we continue to use conductances here. For now Te can be thought of as
the air temperature of a normal room in which the air and wall temperatures are equal. Equation (12.1 1) simply shows the relationship between
temperature, resistance, metabolic rate, and latent heat loss for an animal.
It is extremely useful for analyzing animal-environment interaction, but
before going farther we need to consider some aspects of animal biology
to get values for M, h E, and g ~ b .
heat exchange in a convenient way and also linearizes the energy balance
equation. From Eq. (12.6) it is seen that
Values for gr (with E, set to 1) are tabulated in Table A.3 for temperatures
between -5 and 45°C.
With these changes and substitutions, the energy balance equation now
becomes:
where
Finally, making use of Eq. (12.3) to eliminate surface temperature the
energy budget equation for an animal is obtained in terms of body
temperature:
One final simplification allows the energy balance equation to be written in a particularly useful form. Animal metabolism is often studied
inside chambers where air and wall temperatures are equal, where the
flux density of shortwave radiation is negligible, and where wall emissivities are high. Such a chamber could be called a blackbody enclosure.
If the radiation balance equation (Eq. (1 1.14)) is looked at for an animal
in such an enclosure, it is seen that Rabs = E , O T ~ . We call the temperature of such a blackbody enclosure the operative temperature, with the
symbol Te. Later we relate the operative temperature to outdoor radiation
and temperature conditions, but for now the use of operative temperature
allows us to eliminate radiation terms from the energy balance equation.
The operative temperature form of Eq. (12. lo), with some rearrangement
of terms is:
The second equation, in resistance form, is the more familiar form, but
we continue to use conductances here. For now Te can be thought of as
the air temperature of a normal room in which the air and wall temperatures are equal. Equation (12.1 1) simply shows the relationship between
temperature, resistance, metabolic rate, and latent heat loss for an animal.
It is extremely useful for analyzing animal-environment interaction, but
before going farther we need to consider some aspects of animal biology
to get values for M, h E, and g ~ b .