1270. What is the thermal conductivity of a perfect heat insulator?
Zero
One
∞
Between 0 and ∞
✅ The correct answer is option A.
1272. Mode of heat transfer involved in the cooling of air cooled internal combustion engine is
Conduction
Natural convection
Forced convection
None of these
✅ The correct answer is option B.
1274. Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around __________ BTU.
180
970
3.97
Data insufficient, can
✅ The correct answer is option A.
1276. Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow. )
T
1/ρ
1/A
All of the above
✅ The correct answer is option D.
1278. At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the
Buffer zone
Turbulent core
Both A and B
Viscous sub-layer
✅ The correct answer is option D.
1280. When vaporisation takes place directly at the heating surface, it is called
Film boiling
Nucleate boiling
Vapour binding
None of these
✅ The correct answer is option B.
1282. Tube expansion allowances exist in __________ heat exchanger.
Multipass fixed tube sheet
U-tube
Single pass fixed tube sheet
None of these
✅ The correct answer is option B.
1285. Which of the following is concerned with both heat and mass transfer?
Lewis relationship
Nusselt number
Kutateladze number
Froude number
✅ The correct answer is option A.
1288. A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter ‘d’. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to
D0.8
D-0.2
D-1
D-1.8
✅ The correct answer is option B.
1291. If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is
1
2
1-Feb
4
✅ The correct answer is option B.