Kinematic viscosity of air at $${20^0}C$$ is given to be $$1.6 \times {10^{ - 5}}\,\,\,{m^2}s.$$ Its kinematic viscosity at $${70^0}C$$ will be varying approximately :

If $$'P'$$ is the gauge pressure within a spherical droplet, then gauge pressure within a bubble of the same fluid and of same size will be:

Two fluids, $$A$$ and $$B$$ exchange heat in a counter-current heat exchanger. Fluid $$A$$ enters at $${420^ \circ }C$$ and has a mass flow rate of $$1$$ $$kg/s.$$ Fluid $$B$$ enters at $${20^ \circ }C$$ and also has a mass flow rate of $$1$$ $$kg/s,$$ Effectiveness of heat exchanger is $$75\% $$. Determine the heat transfer rate and exit temperature of fluid $$B.$$ (Specific heat of fluid $$A$$ is $$1$$ $$kJ/kg$$ $$K$$ and that of fluid $$B$$ is $$4$$ $$kJ/kgK$$).

It is proposed to coat a $$1mm$$ diameter wire with enamel paint $$\left( {k\,\,\,\, = 0.1W/m} \right.$$ - $$\left. K \right)$$ to increase heat transfer with air. If the air side heat transfer co-efficiency is $$100$$ $$W/{m^2}K,$$ the optimum thickness of enamel paint should be