1491. The main purpose of providing fins on heat transfer surface is to increase the
Temperature gradient
Mechanical strength of the equipment
Heat transfer area
Heat transfer co-efficient
✅ The correct answer is option C.
Engineering
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1492. Peclet number (Pe) is given by
Pe = Re.Pr
Pe = Re/Pr
Pe = Pr/Re
Pe = Nu.Re
✅ The correct answer is option A.
1493. A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes.
10
>10
<10
Either B or C, depends on the mass of the body
✅ The correct answer is option B.
1494. Crystallisation of solids from a homogeneous solution is a/an __________ process.
Exothermic
Mildly endothermic
Highly endothermic
None of these
✅ The correct answer is option A.
1495. Which of the following is unimportant in forced convection?
Reynolds number
Prandtl number
Grashhoff number
None of these
✅ The correct answer is option C.
1496. Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?
Corrosiveness & fouling characteristics
Pressure
Viscosity
Density
✅ The correct answer is option D.
1497. Low thermal conductivity of heat insulating materials is due to its
Dense structure
High proportion of air space
High specific heat
None of these
✅ The correct answer is option B.
1498. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because
Total heat transfer area of all the effects is -less than that in a single effect evaporator system
Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect
Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system
Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system
✅ The correct answer is option B.
1499. Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?
Thickness of the wall
Area of the wall perpendicular to heat flow
Material of the wall
Temperature difference between the two surfaces of the wall
✅ The correct answer is option D.
1500. In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred
Through a metallic wall
By direct contact of hot flue gas with air
By heating an intermediate material (like chequor bricks) and then heating the air from this hot material
None of these
✅ The correct answer is option C.