A. (ΔT)2
B. (ΔT)4
C. (ΔT)3
D. √(ΔT)
Related Mcqs:
- 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 - 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 - In the free convection regime of pool boiling, the heat flux is proportional to__________________?
A. Δt1/2
B. Δt2
C. Δt5/4
D. Δt - 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) - Nucleate boiling is promoted ___________________?
A. On polished surfaces
B. On rough surfaces
C. In the absence of agitation
D. None of these - 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 - 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 - 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 - In a boiling curve, the peak heat flux is called the _____________ point?
A. Nusselt
B. Leidenfrost
C. Boiling
D. Burnout - 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
