Heat Transfer Operations Practice Test 8

1. What is the relation between the vapour temperature and the liquid temperature on nucleation for a bubble inside the fluid?

T_v – T_sat = (2 σ – p_g) R_v T_v²/p_v h_fg

T_v – T_sat = (2 σ/r – p_g) R_v T_v/p_v h_fg

T_v – T_sat = (2 σ/r – p_g) R_v T_v²/p_v h_fg

T_v – T_sat = (2 σ/r – p_g) R_v T_v²p_v h_fg

2. What does the Kelvin equation tell us about?

The liquid vapour pressure is less than normal

The liquid vapour pressure is equal to normal

The liquid vapour pressure is more than normal

The liquid vapour pressure is very less than normal

3. The Nusselt number for nucleate boiling is correctly represented by which equation?

Nu=\(\frac{Q}{A}\) D_b(T_s-T_sat) K_L

Nu=\(\frac{Q}{A}\) D_b K_L ⁄ (T_s-T_sat)

Nu=\(\frac{Q}{A}\) D_b (T_s-T_sat) ⁄ K_L

Nu=\(\frac{Q}{A}\) D_b ⁄ (T_s-T_sat) K_L

4. We cannot use steam as a drying gas to remove moisture as it would rather condense and reverse the results.

True

False

5. Which one of the following correctly represents the axes of the boiling curve?

Y: Heat flux and X: Temperature difference

X: Heat flux and Y: Temperature

X: Heat transfer coefficient and Y: Temperature

Y: Heat flux and X: Temperature

6. The boiling occurs inside the tubes in ___________ thermosyphon reboiler and inside shell in ____________ thermosyphon reboiler.

Vertical, Horizontal

Horizontal, vertical

Horizontal, Horizontal

Vertical, vertical

7. Which one of the following is not a type of re-boiler?

Thermosyphon reboilers

Internal reboilers

Kettle reboilers

Double pipe Reboilers

8. There are three principal factors that define the nature of a dryer, which one of the following is not?

The method of heating the material

The pressure and temperature of operation

Humidity of the atmosphere

The method of material conveyance through the drying section

9. The Fritz equation to calculate the bubble diameter is given by -
D = C_d β [2 σ/g (ϸ_L – ϸ_V)]^½
What is the value of the constant Cd for water bubbles at 1atm?

0.0027

0.0148

0.00148

0.003

10. ____________ is used as a precursor/ primary process to the drying of heavily moist materials when the moisture-solid bonding is quite weak.

Dewatering

Drying

Dehydration

Desiccation