Question 61. Can we able to find the extract at the second stage with the known values of E1, R1, S2.

Question 62. For the free convection circumstances, the following dimensionless numbers apply
(i) Grashof number
(ii) Prandtl number
(iii) Nusselt number
Identify the correct answer.

Question 63. A spherical heater of 20 cm diameter and at 60 degree Celsius is immersed in a tank of water at 20 degree Celsius. Determine the value of convective heat transfer coefficient

Question 64. Two horizontal steam mains with diameters 5 cm and 15 cm are to be laid in a boiler house that any mutual heat effect is precluded. The mains are at the same surface temperature of 500 degree Celsius whilst the ambient air is at 50 degree Celsius. Workout the heat losses from one meter length of the mains

Question 65. A steam pipe 50 mm diameter and 2.5 m long has been placed horizontally and exposed to still air at 25 degree Celsius. If the pipe wall temperature is 295 degree Celsius, determine the rate of heat loss. At the mean temperature difference of 160 degree Celsius, the thermo-physical properties of air are
k =3.64 * 10⁻² W/m K
v =30.09 * 10⁻⁶ m²/s
P ᵣ =0.682
Β =1/160 + 273 = 2.31 * 10⁻³ per K

Question 66. Two horizontal steam mains with diameters 5 cm and 15 cm are to be laid in a boiler house that any mutual heat effect is precluded. The mains are at the same surface temperature of 500 degree Celsius whilst the ambient air is at 50 degree Celsius. Workout the ratios of the heat transfer coefficients.

Question 67. A steam pipe 50 mm diameter and 2.5 m long has been placed horizontally and exposed to still air at 25 degree Celsius. If the pipe wall temperature is 295 degree Celsius, find out the Grashof number. At the mean temperature difference of 160 degree Celsius, the thermo-physical properties of air are
k =3.64 * 10⁻² W/m K
v =30.09 * 10⁻⁶ m²/s
P ᵣ =0.682
Β =1/160 + 273 = 2.31 * 10⁻³ per K

Question 68. Find the slope of the operating line for the first stage if the dilutant in the feed is 5 kg and the solvent used for the second stage is 10 kg.

Question 69. Estimate the heat transfer from a 40 W incandescent bulb at 125 degree Celsius to 25 degree Celsius in quiescent air. Approximate the bulb as a 50 mm diameter sphere. The approximate correlation for the convection coefficient is
Nu = 0.60 (Gr Pr)^ 0.25
Where the different parameters are evaluated at the mean film temperature, and characteristics length is the diameter of the sphere.

Question 70. A 40 W incandescent bulb at 125 degree Celsius to 25 degree Celsius in quiescent air. Approximate the bulb as a 50 mm diameter sphere. The approximate correlation for the convection coefficient is
Nu = 0.60 (Gr Pr)^ 0.25
Where the different parameters are evaluated at the mean film temperature, and characteristics length is the diameter of the sphere.
Find what percent of power is lost by free convection?