HEAT TRANSFER QUIZ

The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as

(D)-0.2

(D)-1.8

(D)1.8

(D)0.2

TRUE ANSWER : ?
YOUR ANSWER : ?

Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is

Mainly confined to a thin film of fluid near the surface

None of these

Uniformly distributed throughout the fluid

In the central core of the fluid

TRUE ANSWER : ?
YOUR ANSWER : ?

In a shell and tube heat exchanger, floating head is used for

Less corrosion of tubes

Low pressure drop

Large temperature differentials

High heat transfer co-efficient

TRUE ANSWER : ?
YOUR ANSWER : ?

Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.

High pressure

Falling film

Long tube

None of these

TRUE ANSWER : ?
YOUR ANSWER : ?

The Grashoff number is defined as the ratio of the

buoyancy to inertial forces

inertial to viscous forces.

buoyancy to surface tension forces

buoyancy to viscous forces

TRUE ANSWER : ?
YOUR ANSWER : ?

A graph between __________ is called Wilson plot.

1/v0.8 Vs . U

V0.8 Vs . U

1/U Vs . 1/v0.8

1/U Vs . 1/V

TRUE ANSWER : ?
YOUR ANSWER : ?

The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)

α 1/T

Independent of T

αT

α T⁴

TRUE ANSWER : ?
YOUR ANSWER : ?

The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe )

2hi/K

K/h0

2K/h0

hi/K

TRUE ANSWER : ?
YOUR ANSWER : ?

In case of a vertical tube evaporator, with increase in the liquor level, the

Capacity of the evaporator is increased

Capacity of the evaporator is decreased

Both B and C

True temperature drop increases

TRUE ANSWER : ?
YOUR ANSWER : ?

Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for

Equal for all the three

Sphere

Cube

Cylinder

TRUE ANSWER : ?
YOUR ANSWER : ?

↑