Related Mcqs:

1. Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?

   A. Convection becomes important
   B. Conduction becomes important
   C. Radiation becomes important
   D. Sub-cooled boiling occurs

2. The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?

   A. 11.2 kW/m2
   B. 12.0 kW/m2
   C. 14.6 kW/m2
   D. 16.5 kW/m2

3. In the free convection regime of pool boiling, the heat flux is proportional to__________________?

   A. Δt1/2
   B. Δt2
   C. Δt5/4
   D. Δt

4. For small temperature difference, the heat transfer rate as per Newton’s law of cooling is proportional to (where, Δt = excess temperature) ?

   A. Δt
   B. Δt2
   C. Δt3
   D. √(Δt)

5. Nucleate boiling is promoted ___________________?

   A. On polished surfaces
   B. On rough surfaces
   C. In the absence of agitation
   D. None of these

6. A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time ___________________?

   A. t = 283 s
   B. t = 356 s
   C. t = 400 s
   D. t = 800 s

7. In case of _______________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface?

   A. Nucleate
   B. Local
   C. Pool
   D. Saturated

8. It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is____________________?

   A. 3.06 × 105
   B. 6.12 × 105
   C. 7.24 × 105
   D. 9.08 × 105

9. In a boiling curve, the peak heat flux is called the _____________ point?

   A. Nusselt
   B. Leidenfrost
   C. Boiling
   D. Burnout

10. The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is___________________?

    A. 25°C
    B. 30°C
    C. 35°C
    D. 40°C