An insulating material with a thermal conductivity k = 0.12W/mK is used for a pipe carrying steam. The local coefficient of heat transfer to the surrounding h = 4 W/m²K. In order to provide effective insulation, what should be the minimum outer diameter of the pipe?

A plane slab of 100mm thickness generates heat. It is observed that the temperature drop between the center and its surface to be 50°C. If the thickness is increased to 200mm the temperature difference will be ___________

As the temperature increases, the thermal conductivity of a gas ____________

Hot air at 50°C. If the forced heat transfer convection is 75 W/m²K, the heat gain rate gain rate by the plate through an area of 2m² will be _____

Which of the following non-dimensional numbers is used for transition from laminar flow to turbulent flow in the free convection?

Which non-dimensional numbers relates the thermal boundary layer and hydrodynamic boundary layer?

The laminar boundary layer occurs when a cold fluid over a hot plate. In which of the following positions, the temperature gradient assumes zero value?

The characteristic length for computing Grashoff number of horizontal cylinder is ___________

In laminar developing flow through a pipe with constant wall temperature, the magnitude of the pipe wall inner surface convective heat transfer coefficient shall be maximum at the:

For a fluid with Prandtl number Pr>1, momentum boundary layer thickness?

Water (Prandtl number ≈6) flows over a flat plate which is heated over the entire length. Which one of the following relationship between the hydrodynamic boundary layer thickness (δ) and the thermal boundary layer thickness (δ)t is true?