A. ∝ t
B. ∝ 1/t
C. ∝ √t
D. Independent of ‘t’
Related Mcqs:
- The film thickness for laminar film condensation on vertical surface _____________ from top to bottom?
A. Cumulatively increases
B. Cumulatively decreases
C. Remain constant
D. And the surface conductance increase - The heat transfer co-efficient in film type condensation is _______________ that for dropwise condensation?
A. Greater than
B. Lower than
C. Is same as
D. Half - Film condensation is promoted on a/an _______________________ surface?
A. Oily
B. Coated
C. Clean & smooth
D. Dirty - Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?
A. x/KA
B. KA/x
C. K/Ax
D. A/Kx - For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then__________________?
A. hf = hd
B. hf > hd
C. hf < hd
D. hf could be greater or smaller than hd - A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?
A. Greater than that for un-insulated steam pipe
B. Less than that of the un-insulated steam pipe
C. Equal to that of the un-insulated steam pipe
D. Less than the steam pipe with 5 cms insulation - The most conducive surface for dropwise condensation to occur is the _____________ surface?
A. Coated
B. Oily
C. Glazed & polished
D. Smooth - Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2.°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the_________________?
A. Higher condensing film co-efficient is desired
B. Condensate is corrosive in nature
C. Lower pressure drop through the exchanger is desired
D. Temperature of the incoming vapor is very high - The thickness of condensate layer in filmwise condensation depends on the__________________?
A. Condensation rate
B. Surface configuration
C. Liquid flow rate from the surface
D. All A., B. and C. - The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?
A. More
B. Less
C. Some
D. Either more or less; depends on the nature of vapor
