Question 1. A metal piece of length 60 cm has a cross-section corresponding to a sector of a circle of radius 10 cm and included angle 60°. Its ends are maintained at temperature of 125 °C and 25 °C and the thermal conductivity of the material has a linear variation with temperature in degree Celsius.
k = (100-0.01 t) W/m-deg
Find the heat flow rate through the metallic piece. Presume uni-directional heat conduction, i.e., neglect any variation of temperature in the θ and r-directions.
Question 2. A spherical heater of 20 cm diameter and at 60 ºC is immersed in a tank of water at 20 ºC .determine the value of convective heat transfer coefficient
Question 3. A blind cylindrical hole of 2cm diameter and 3 cm in length is drilled into a metal slab having emissivity 0.7. if the metal slab is maintained at 650 k , make calculations for the radiation heat escape from the hole.
Question 4. Air moving at 0.3 m/s blows over the top of a chest type freezer. The top of the freezer measures 0.9 m by 1.5m and is poorly insulated so that the surface remains at 10ºC. if the temperature of air is 30 ºC , make calculations for the maximum heat transfer by forced convention from the top of the freezer.
Question 5. Estimate the diffusion coefficient of carbon tetrachloride into air from the following data recorded in a Stefan-tube experiment with carbon tetrachloride ad oxygen: diameter of tube and its length above liquid surface: 1 cm and 15 cm respectively; temperature and pressure maintained: 0°C and 760 mm of mercury; evaporation of carbon tetrachloride: 0.03 gm in 10 Hr; vapour pressure of carbon tetrachloride: 33 mm of mercury.
Question 6..Explain the difference between parallel flow and counter flow heat exchanger and show how the two fluids vary along the path of flow.