Lumped heat transfer analysis of a solid object suddenly exposed to a fluid medium at a different temp is valid when.

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 $$\left( \delta \right)$$ and thermal boundary layer thickness $$\left( {{\delta _t}} \right)$$ is true

For the circular tube of equal length and diameter shown in fig below, the view factor $${F_{13}}$$ is $$0.17.$$ The view factor $${F_{12}}$$ in this case will be.

A company is offered the following price breaks for order quantity

Order cost is Rs.$$60$$ per order while the holding cost is $$10\% $$ of the purchase price. Determine the economic order quantity $$(EOQ)$$ if the annual requirement is $$1000$$ units.