Question 41. An egg with mean diameter of 4 cm and initially at 25 degree Celsius is placed in an open boiling water container for 4 minutes and found to be boiled at a particular level. For how long should a similar egg boil at the same level, when refrigerator temperature is 5 degree Celsius? Use lumped parameter theory and assume following properties of egg
k = 12 W/m K
h = 125 W/m² K
c = 2 k J/kg K
p = 1250 kg/m³

Question 42. Which of the following is not correct in a transient flow process?

Question 43. A cylindrical stainless steel (k = 25 W/m K) ingot, 10 cm in diameter and 25 cm long, passes through a heat treatment furnace which is 5 meter in length. The initial ingot temperature is 90 degree Celsius, the furnace gas is at 1260 degree Celsius and the combined radiant and convective surface coefficient is 100 W/m² K. Determine the maximum speed with which the ingot moves through the furnace if it must attain 830 degree Celsius temperature. Take thermal diffusivity as 0.45 * 10¯⁵ m²/s

Question 44. The curve for unsteady state cooling or heating of bodies is

Question 45. What is the wavelength band for TV rays?

Question 46. Diagram shows transient heat conduction in an infinite plane wall. Identify the correct boundary condition in transient heat conduction in solids with finite conduction.

Question 47. Let there is some conduction resistance, then temperature becomes a function of
(i) Biot number
(ii)Fourier number
(iii) Dimensionless parameter
Identify the correct statement

Question 48. A large steel plate 50 mm thick is initially at a uniform temperature of 425 degree Celsius. It is suddenly exposed on both sides to an environment with convective coefficient 285 W/m² K and temperature 65 degree Celsius. Determine the center line temperature.
For steel, thermal conductivity = 42.5 W/m K and thermal diffusivity = 0.043 m²/hr

Question 49. “When Biot number exceeds 0.1 but is less than 100, use is made of Heislers charts for the solution of transient heat conduction”. Choose the correct answer

Question 50. A 12 cm diameter cylindrical bar, initially at a uniform temperature of 40 degree Celsius, is placed in a medium at 650 degree Celsius with convective coefficient of 22 W/m² K. Determine the time required for the center to reach 255 degree Celsius. For the material of the bar:
Thermal conductivity = 20 W/m K
Density = 580 kg/m³
Specific heat = 1050 J/kg K