41
Pick out the wrong statement.
A)
By increasing the number of shell passes, the temperature cross in a shell and tube heat exchanger can be prevented
B)
An underdesigned steam trap will back up the condensate instead of discharging it out
C)
Steam condensate is corrosive because of the presence of dissolved oxygen in it
D)
Film boiling is desirable in commercial equipments due to high heat transfer rate at low temperature drop
Answer & Solution
Answer: Option
D
42
Economy of a multiple effect evaporator is not influenced much by the
A)
Boiling point elevations
B)
Temperature of the feed
C)
Rate of heat transfer
D)
Ratio of the weight of the thin liquor to thick liquor
Answer & Solution
Answer: Option
A
43
Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8 . Pr n , is not valid, if the value of
A)
N = 0.4 is used for heating
B)
N = 0.3 is used for cooling
C)
Reynolds number for the flow involved is > 10000
D)
Reynolds number for the flow involved is < 2100
Answer & Solution
Answer: Option
D
44
LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.
A)
Parallel
B)
Mixed
C)
Counterflow
D)
Same in either A, B or C
Answer & Solution
Answer: Option
D
45
In evaporators, lowering the feed temperature
A)
Increases the heating area required
B)
Reduces the economy
C)
Both A and B
D)
Decreases the heating area required
Answer & Solution
Answer: Option
C
46
Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, may be around __________ BTU.
A)
180
B)
970
C)
3.97
D)
None of these
Answer & Solution
Answer: Option
A
47
Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around __________ BTU.
A)
180
B)
970
C)
3.97
D)
Data insufficient, can't be predicted
Answer & Solution
Answer: Option
A
48
When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is
A)
Free convection
B)
Entry length problem in laminar forced conduction (developing thermal boundary layer)
C)
Mixed convection (both free and forced)
D)
Forced convection
Answer & Solution
Answer: Option
C
49
With increase in temperature, the thermal conductivity of non-metallic amorphous solids
A)
Decreases
B)
Increases
C)
Remains constant
D)
First decreases upto certain temperature and then increases
Answer & Solution
Answer: Option
B
50
What is the thermal conductivity of a perfect heat insulator?
A)
Zero
B)
One
C)
∞
D)
Between 0 and ∞
Answer & Solution
Answer: Option
A
