Consider two infinitely long thin concentric tubes of circular cross section as shown in the figure. If $${D_1}$$ and $${D_2}$$ are the diameters of the inner and outer tubes respectively, then the view factor $${F_{22}}$$ is given by

Water $$\left( {{C_p} = 4.18\,kJ/kg.K} \right)$$ at $${80^ \circ }C$$ enters a counter flow heat exchanger with a mass flow rate of $$0.5kg/s.$$ Air $$\left( {{C_p} = 1\,kJ/kg.\,K} \right)$$ enters at $${80^ \circ }C$$ with a mass flow rate $$2.09$$ $$kg/s.$$ If the effectiveness of the heat exchanger is $$0.8,$$ the $$LMTD$$ (in $$^ \circ C$$) is

For a particular project, eight activities are to be carried out. Their relationships with other activities and expected durations are mentioned in the table below.

The critical path for the project is

For a particular project, eight activities are to be carried out. Their relationships with other activities and expected durations are mentioned in the table below.

If the duration of activity $$''f ''$$ alone is changed from $$9$$ to $$10$$ days, then the