A fluid (Prandtl number, $$Pr=1$$) at $$500$$ $$K$$ flows over a flat plate of $$1.5$$ $$m$$ length, maintained at $$300$$ $$K.$$ The velocity of the fluid is $$10\,\,m/s.$$ Assuming kinematic viscosity, $$v = 30 \times {10^{ - 6}}\,\,{m^2}/s,$$ the thermal boundary layer thickness (in $$mm$$) at $$0.5$$ $$m$$ from the leading edge is _________.

For flow through a pipe of radius $$R,$$ the velocity and temperature distribution are as follows:
$$U\left( {r,x} \right) = {C_1}$$ 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

Water flows through a tube of diameter $$25mm$$ at an average velocity of $$1.0m/s.$$ The properties of water are $$\rho = 1000\,\,kg/{m^3},$$ $$\mu = 7.25 \times {10^{ - 4}}\,\,N.s/{m^2},$$ $$\,K = 0.625W/m.K,$$ $$Pr=4.85.$$ Using $$Nu=0.023$$ $$R{e^{0.8}}\,\,{\Pr ^{0.4}},$$ the convective heat transfer coefficient (in $$W/{m^2}.K$$) is ______________.

The non-dimensional fluid temperature profile near the surface of a convectively cooled flat plate is given by $${{{T_w} - T} \over {{T_w} - {T_\infty }}} = a + b{y \over L} + c{\left( {{y \over L}} \right)^2},$$ where $$y$$ is measured perpendicular to the plate, $$L$$ is the length, and $$a,b$$ and $$c$$ are arbitrary constants. $${{T_w}}$$ and $${{T_\infty }}$$ are wall and ambiyent temperatures, respectively. If the thermal conductivity of the fluid is $$k$$ and the wall heat flux is $$q'',$$ the Nusselt number $$\,{N_u} = {{q''} \over {{T_w} - {T_\infty }}}{L \over k}$$ is equal to