Among the statements reported below,
select the one that is false.
O The heat conduction equation consists of an
energy balance over an infinitesimal element
domain.
O The Fourier's law can be derived from the heat
conduction equation.
O The heat conduction equation is used in
conjunction with boundary conditions and initial
conditions, for defining the temperature field
within a finite space domain.
O Thermal conductivity is a property that (in reality)
depends on temperature.
Question 2
Consider the screen of a desktop as a
1D-plane wall model. When it is
switched on, the steady-state
temperature at the centre of the device
will be (select the ONLY ONE true
statement):
O equal to the room temperature.
O impossible to say.
O higher than the room temperature.
O equal to the temperature at the screen edges
(which are exposed to the room).
Question 3
Among the statements reported below,
select the one that is false.
O The heat transfer is a quantity always associated
to a finite surface.
O The heat flux is a vectorial quantity that can be
evaluated at any point of the considered domain.
O The mathematical expression for the temperature
gradient is independent from the adopted
coordinate system.
O The temperature gradient in a point indicates the
magnitude and direction of the biggest
temperature variation around that point.
Question 4
Consider an insulated pipe (2 layers).
Please select the (ONLY ONE) true
statement.
O The heat flux is constant across the pipe
thickness.
O The total thermal resistance does not depend on
the geometric properties of the pipe layers.
O The heat transfer evaluated at the pipe innermost
surface is equal to the one evaluated at the pipe
outermost surface.
O The surface of exchange at the innermost pipe
radius is bigger than the one at the outermost
radius.