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.Management Sciences
Category: Chemical Heat Transfer
Which of the following has the lowest overall heat transfer co-efficient ?
A. Dowtherm
B. Molten sodium
C. Water
D. Air
Pick out the wrong statement ?
A. Heat transfer from a hot body to cold body by the emission of heat waves is called radiation
B. Filmwise condensation takes place on non-wettable surfaces
C. The boiling point of a solution is affected by liquid head as well as boiling point elevation
D. None of these
Nusselt number is a function of Prandtl number and ______________ number of fluid in natural convection heat transfer?
A. Grashoff
B. Biot
C. Stanton
D. Reynolds
In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to _____________ the velocity head?
A. Twice
B. Four times
C. Square root of
D. Square of
Baffle spacing ____________________?
A. Is not the same as baffle pitch
B. Should be less than one fifth the diameter of the shell
C. Should be less than the inside diameter of the shell
D. None of these
The advantage of backward feed multiple effect evaporators over forward feed units is that___________________?
A. Heat sensitive material can be handled
B. There is no additional cost of pumping
C. Most concentrated liquid is at highest temperature
D. Equal heat transfer co-efficients exist in various effects
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
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