Question 1

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.