Sphericity of raschig ring (whose length and diameter are equal) is

For raschig rings, the sphericity is

A

0.5

B

1

C

$$\sqrt 3 $$

Lessing ring is formed by the addition of a partition across the centre of a raschig ring, which results in an area increase of about __________ percent.

A

5

B

20

C

35

D

55

Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity?

A

Sphere

B

Cube

C

Cylinder (L/D = 1)

D

Raschig rings

Raschig ring made of procelain cannot be used for treating concentrated

A

Hydrochloric acid

B

Nitric acid

C

Alkalis

D

Sulphuric acid

Maximum size of the raschig rings used in a packed tower is about __________ of the coloumn diameter.

A

$${\frac{1}{{10}}^{{\text{th}}}}$$

B

$${\frac{1}{{20}}^{{\text{th}}}}$$

C

$${\frac{1}{{30}}^{{\text{th}}}}$$

D

$${\frac{1}{{50}}^{{\text{th}}}}$$

Diameter of raschig rings used in packed tower in industry is normally around __________ inches.

A

2

B

8

C

12

D

18

M.I. of a thin ring (external diameter D, internal diameter d) about an axis perpendicular to the plane of the ring, is

A

$$\frac{\pi }{{64}}\left( {{{\text{D}}^4} + {{\text{d}}^4}} \right)$$

B

$$\frac{\pi }{{32}}\left( {{{\text{D}}^4} - {{\text{d}}^4}} \right)$$

C

$$\frac{\pi }{{32}}\left( {{{\text{D}}^4} + {{\text{d}}^4}} \right)$$

D

$$\frac{\pi }{{32}}\left( {{{\text{D}}^4} \times {{\text{d}}^4}} \right)$$

Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)

A

Increases pressure drop, increases surface area

B

Increases pressure drop, decreases surface area

C

Decreases pressure drop, increases surface area

D

Decreases pressure drop, decreases surface area

Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is

A

0.5

B

1

C

$$\sqrt 2 $$

D

$$\sqrt 3 $$

Reciprocal of sphericity is termed as the

A

Specific surface ratio

B

Shape factor

C

Sauter diameter

D

Surface area per unit mass

Sphericity of raschig ring (whose length and diameter are equal) is

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