Convection · Heat Transfer · GATE ME
Marks 1
A quiescent fluid at temperature $T_3$ is confined between two vertical parallel plates. While plate 1 is kept at temperature $T_1$ and plate 2 is maintained at temperature $T_{2^{\prime}}$ a velocity profile between the plates, as shown in the figure below, is generated due to heat transfer. Which one of the following options shows the correct relations among $T_1, T_2$, and $T_3$ ?
Consider incompressible laminar flow over a flat plate with freestream velocity of $u_{\infty}$. The Nusselt number corresponding to this flow velocity is $Nu_1$. If the freestream velocity is doubled, the Nusselt number changes to $Nu_2$. Choose the correct option for $Nu_{2}/Nu_{1}$.
Consider a hydrodynamically fully developed laminar flow through a circular pipe with the flow along the axis (i.e., z direction). In the following statements, $T$ is the temperature of the fluid, $T_w$ is the wall temperature and $T_m$ is the bulk mean temperature of the fluid. Which one of the following statements is TRUE?
The free stream velocity is $${U_\infty }$$ and the free stream temperature $${T_\infty }$$ is lower than the cylinder surface temperature $${T_s}.$$ The local heat transfer coefficient is minimum at point
Group-A
$$P:$$$$\,\,\,\,\,\,\,$$ Biot number
$$Q:$$$$\,\,\,\,\,\,\,$$ Grashof number
$$R:$$$$\,\,\,\,\,\,\,$$ Prandtl number
$$S:$$$$\,\,\,\,\,\,\,$$ Reynolds number
Group-B
$$1:$$$$\,\,\,\,\,\,\,$$ Ratio of buoyancy to viscous force
$$2:$$$$\,\,\,\,\,\,\,$$ Ratio of inertia force to viscous force
$$3:$$$$\,\,\,\,\,\,\,$$ Ratio of momentum to thermal diffusivities
$$4:$$$$\,\,\,\,\,\,\,$$ Ratio of internal thermal resistance to boundary layer thermal resistance
Marks 2
A very large metal plate of thickness 𝑑 and thermal conductivity 𝑘 is cooled by a stream of air at temperature 𝑇∞ = 300 K with a heat transfer coefficient ℎ, as shown in the figure. The centerline temperature of the plate is TP. In which of the following case(s) can the lumped parameter model be used to study the heat transfer in the metal plate?
$$U\left( {r,x} \right) = {C_1}$$ and $$T\left( {r,x} \right) = {C_2}\left[ {1 - {{\left( {{r \over R}} \right)}^3}} \right],$$
where $${C_1}$$ and $${C_2}$$ are constants. The bulk mean temperature is given by
$${T_m} = {2 \over {{U_m}{R^2}}}\int\limits_0^R {u\left( {r,x} \right)T\left( {r,x} \right)rdr,} $$
with $${{U_m}}$$ being the mean velocity of flow. The value of $${T_m}$$ is
List-$${\rm I}$$
$$P.$$ Compressible flow
$$Q.$$ Free surface flow
$$R.$$ Boundary layer flow
$$S.$$ Pipe flow
$$T.$$ Heat convection
List-$${\rm II}$$
$$U.$$ Renolds number
$$V.$$ Nussult number
$$W.$$ Weber number
$$X.$$ Froude number
$$Y.$$ Mach number
$$Z.$$ Skin friction coefficient
$$\left( {T - {T_w}} \right)/\left( {{T_\infty } - {T_w}} \right) = \left( {3/2} \right)\,\,\left( {y/{\delta _t}} \right) - \left( {1/2} \right){\left( {y/{\delta _t}} \right)^3},$$
where $${{T_w}}$$ and $${{T_ \propto }}$$ are the temp of plate and free stream respectively, and $$'y'$$ is the normal distance measuread from the plate. The ratio of Average to the local Nussult number based on the thermal boundary layer thickness $${{\delta _t}}$$ is given by
The specific heat of the plate material is $$2.5KJ/KgK.$$ The convective heat transfer coefficient in $$W/{m^2}K,$$ at instant when the plate temp is $${225^ \circ }C$$ and the change in plate temp with time $$dT/dt=-0.02K/s,$$ is
The Reynolds number for the flow is
The heat transfer per meter length of the duct, in watts, is
List - $${\rm I}$$
$$A.$$ Grashof number
$$B.$$ Schmid number
$$C.$$ Weber number
$$D.$$ Fourier number
List - $${\rm II}$$
$$1.$$ Mass diffusion
$$2.$$ Transient heat conduction
$$3.$$ Free convection
$$4.$$ Forced convection
$$5.$$ Surface tension
$$6.$$ Radiation