This document discusses heat transfer, heat production, and temperature regulation in animals. It explains that all animals produce heat through metabolism but must lose heat to their environment to avoid overheating. There are three main mechanisms of heat transfer: conduction between solid objects, convection between a solid object and moving fluid like air or water, and evaporation which can cool animals through latent heat of vaporization. The rate of heat transfer depends on the temperature difference, contact area, and properties of the materials like density and thermal conductivity. Maintaining the proper balance of heat production and loss through these mechanisms allows animals to regulate their body temperature.

1. Heat transfer, heat production and
temperature regulation in animals

2. Why does temperature matter?
• chemical reactions of metabolism are slower at
low temperatures rate approximately doubles
per 10o C rise
• proteins (enzymes, structural proteins), DNA
and RNA denature at high temperatures
• lipids in membrane require temperature to
maintain fluidity for function
• fatty acid profile can differ depending on species
habitat temperature

3. All animals produce heat
• First law of thermodynamics, about the
conservation of energy:
• Second law of thermodynamics, about entropy
so they all must lose heat to environment or
will cook themselves to death
• if they lose heat faster than they generate it,
body temperature falls and vice-versa.

5. Conduction
•Heat transfer between non-moving matter
• within on matter or between two touching matters
• solid to solid, solid to unmoving fluid, unmoving
fluid to unmoving fluid
• fluid is liquid (like water) or gas (like air)

7. Conduction and heat of fusion

8. • Convection
• movement between a body and a moving fluid
• fluid movement can be generated by heat natural
or passive convection fluid movement can be
forced water pump forcefully moves engine
coolant through engine convecting heat from
cylinders to coolant and carrying it to radiator
where it convects out of coolant to solid radiator
and convects off of radiator to air cooling fan and
car movement forcefully convect air through
radiator heart forces blood from body core to
surface fans cool (or heat) body by forced
convection

9. Conduction (+ some Convection) to
liquid

14. Evaporation
• latent heat of vaporization of water 540 kcal/kg water
evaporated
•2260 joule/g water evaporated
•can cool animal when environmental temperature exceeds
body temperature cannot cool animal if air is saturated
with water (100% relative humidity at skin temperature)
• THI (temperature humidity index) “its not the heat its the
humidity”
• its both air movement replaces more water saturated air
with fresh drier air

15. Evaporation

16. Forced convection with evaporation

17. Heat can transfer into animal

18. Conduction
• heat loss between unmoving matter (solids or still fluids)
• Q/time = conductance (k)/depth (L) * area * temperature
difference
• heat loss/area at fixed temp difference = k / L
• L is ‘depth’ of solid
• k (conductance) is proportional to density
• Insulating materials (styrofoam, fiberglass blankets,
down jackets) are all low density to resist heat
• One reason why loosing heat to air requires convection

19. Conduction
• heat loss between unmoving matter (solids or still fluids)
• Q/time = heat loss
• heat loss/area = k / L * temperature difference
• l is ‘depth’ of solid
• k is proportional to density
• creating an unmoving layer of low density air = smaller
k
• increasing L reduces rate of heat transfer
• fluffy hair, fur or feathers do both!
• Offsets increased delta T in winter

20. Convection
• • Rate of heat transfer by convection =
h*A*(Ts - Tb) Ts=surface temperature (at
interface of solid and fluid) Tb = temperature
somewhere far enough from the surface so its
the average temperature of the mass of fluid
(think air temperature) A is the contact area

22. Heat transfer depends on
• temperature difference determines direction
and rate
• area
• how does area relate to animal mass?