A. Increases
B. Decreases
C. Remains unchanged
D. May increase or decrease; depending on temperature
Related Mcqs:
- For what value of Prandtl number, the Col-burn analogy is valid ?
A. 0.06 to 120
B. 0.6 to 120
C. 1 to 103
D. 1 to 50 - Fouling factor_____________________?
A. Is a dimensionless quantity
B. Does not provide a safety factor for design
C. Accounts for additional resistances to heat flow
D. None of these - Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer coefficient is „3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?
A. 35.5
B. 43.75
C. 81.25
D. 48.25 - If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _____________ law?
A. Parabolic
B. Hyperbolic
C. Linear
D. Logarithmic - 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 - If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows ____________ law?
A. Hyperbolic
B. Parabolic
C. Linear
D. Logarithmic - 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 - With increase in temperature, the thermal conductivity of most liquids_________________?
A. Increases
B. Decreases
C. Remain same
D. First increases upto a certain temperature and then becomes constant - For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally ?
A. Decreases
B. Increases
C. Remains unchanged
D. Increases exponentially - For a given ambient air temperature with increase in the thickness of insulation of a hot cylindrical pipe, the rate of heat loss from the surface would ?
A. Decrease
B. Increase
C. First decrease and then increase
D. First increase and then decrease
