19. Consider a hot, boiled egg in a spacecraft that is filled with air at atmospheric pressure
and temperature at all times. Disregarding any radiation effect, will the egg cool
faster or slower when the spacecraft is in space instead of on the ground.
(a) No difference (b) Faster (c) Slower (d) Insufficient data
Sol: From the data it can be observed that the mode of heat transfer from the egg is natural
Natural convection occurs due to buoyancy effects and buoyancy depends on gravity.
• The rate of heat transfer due to natural convectional depends on gravity.
• More the gravity, more will be heat transfer rate.
• But in space, gravity is very less compared to ground.
Heat transfer rate will be more on ground than in space
20 In a composite material A-B-C (respective thermal conductivities are temperature
independent and related as: k
, the steady state heat flux distribution is
shown in the figure below. The corresponding steady state temperature distribution is
For region A: