How many types of convection processes are there?

Here are some assumptions that are made for Fourier law. Identify the wrong one:

Treat the human eye as a spherical system operating at a steady-state. The amount of heat transfer from the interior of the eye (anterior chamber) to the outside depends on whether a contact lens is worn. Assume that the convective heat-transfer coefficient remains unchanged with/without lens. Select the correct option(s):

A steam pipe has two layers of insulation of same thickness, inner layer material being a better insulator than outer. If two layers are interchanged, The heat conducted would:

Two walls having same thermal conductivity and same cross-sectional area are joined together. The temperature profile is as shown. Assume 1-D steady state heat conduction in the system. What could be the reason for different slopes in the temperature profile ?

Which of the following Temperature profile is correct representation for a composite wall with constant thermal conductivities K1 and K2 in wall 1 and wall 2 respectively. Left end of wall 1 is insulated and there's uniform heat generation is wall1.

A long, circular aluminium rod attached at one end to the heated wall and transfers heat through convection to a cold fluid.If the diameter of the rod is triples, what would happen to new rate of heat transfer?

Assume infinitely long rod.

For an annular fin, the governing equation is $$\frac{\partial^2\theta}{\partial x^2}-m^2\theta=0$$  where $$m=hpkA$$  and $$θ=T−T_{\infty}$$  , where p is perimeter and A is cross sectional area, other symbols have usual meaning.

The relation between effectiveness ( $$\epsilon$$ )  and efficiency ( $$\eta$$  ) of a triangular fin with solar surface area  $$A_s$$  and base cross-section area  $$A_c$$  is:

In the lumped capacitance assumption (LCA) employed for transient conduction, a body may be considered to be a lump of uniform temperature. Which of the following statements is/are true?

Consider a thermocouple used to measure the cold air temperature inside an AC duct. The thermocouple junction is approximated as a small solid sphere (bead). Response time is the time taken for thermocouple reading to approach actual air temperature.

In every statement listed below: one factor is changed keeping all other factors same, and validity of lumped capacitance assumption is always ensured. Choose correct statement(s).

Assume that lumped capacitance is applicable in the analysis of a system. This lumped system has a thermal time constant of $$\tau$$  . It is initially at $$T_i$$  and its surroundings are maintained at $$T_{\infty}$$  . The time taken for the system to reach an average temperature of $$\frac{T_i+T_{\infty}}{2}$$   is given by:

Nusselt number (Nu) value between 1 and 10 is characteristic of slug/laminar flow. A larger Nusselt number corresponds to more active convection, with turbulent flow typically in the 100–1000 range. Which of the following statement(s) justify that Nusselt number cannot be less than one?

Common applications of finned surfaces are with

(i) Electrical motors

(ii) Economizers for steam power plant

(iii) Convectors for steam and cold water heating systems

(iv) Cooling coils

Identify the correct option: