A. Cumulatively increases
B. Cumulatively decreases
C. Remain constant
D. And the surface conductance increase
Related Mcqs:
- The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness) _________________?
A. ∝ t
B. ∝ 1/t
C. ∝ √t
D. Independent of ‘t’ - 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 - The most conducive surface for dropwise condensation to occur is the _____________ surface?
A. Coated
B. Oily
C. Glazed & polished
D. Smooth - 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 - 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. - Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping_________________?
A. Both the tube sheets fixed
B. Both the tube sheets floating
C. The top tube sheet floating and bottom tube sheet fixed
D. The top tube sheet fixed and the bottom tube-sheet floating - 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
