Heat Transfer Operations Practice Test 4

1. The number of blades is a Scraped Surface Heat Exchanger does not depend on one of the following factor, which one is it?

Capital Cost

Fouling Factor

Viscosity

Rotation speed

2. Which one of the following is correct expression for sphericity of a particle?
Note: Vp = Volume of particle, Ap = Surface areas of the Particle.

S = \(\frac{\pi^{\frac{1}{3}}(6Vp)^\frac{4}{3}}{Ap}\)

S = \(\frac{6Vp}{Ap}\)

S = \(\frac{(6Vp)^\frac{2}{3}}{Ap}\)

S = \(\frac{\pi^{\frac{1}{3}}(6Vp)^\frac{2}{3}}{Ap}\)

3. Packed Beds are one of the most common heat exchangers because of its very ______

High bed side heat transfer coefficient

Low heat transfer rate

High conductivity

High wall side heat transfer coefficient

4. What can Scraped Surface Heat Exchangers do?

Adds turbulence to the core of the fluid

Can handle large pressure drops

Use high pumping power

Removes the layer of fluid at surface and mixes with bulk

5. The pressure drop in a packed bed is _______ for a given length.

Exponentially Increasing

Linearly Increasing

Constant

Parabolically Increasing

6. The maintenance cost of the Scraped Surface Heat Exchanger is usually low because of one of the following factor. What is it?

High viscous fluids are used

It removes the fouling formed at the surface

No pumps are used

No motors are used

7. The effective thermal conductivity of a packed bed is almost ____ the Thermal Conductivity of the gas.

Seven

Eight

Six

Five

8. Calculate h_wall
Re = 12000
Pr = 0.47
Kg = 15W/mK
Radius of pellets = 15mm

800 KW/m²K

528 KW/m²K

728 KW/m²K

828 KW/m²K

9. Which one of the following is the correct expression for Friction Factor in Packed Bed Columns?

f = 150/Re+1.75

f = 150/Re

f = 100/Re+0.0035

f = 180/Re+1.5

10. Recognize the following diagram.

Internal Coiled Vessel

Jacketed Vessel

Half coil Vessel

Shell and Tube Heat Exchanger