Heat Transfer Operations Practice Test 3

1. Our design dirt factor should be _____ the provided threshold dirt factor.

More than

Much less than

Less than

Equal to

2. For using fins, the heat flow is assumed to be in _______

Exponentially increasing

Unsteady State

Steady State

Linearly decreasing

3. Fins can be added only to one side of a heat exchanger.

False

True

4. The thermal conductivity of the fin should _________ with time.

Exponentially increasing

Decreasing

Increasing

Constant

5. What is the correct expression for Reynolds number in service side for jacket type Agitated Vessels?

\(Nu=K(\frac{\rho^2\beta g \Delta Tm}{\mu^2})^{1/3}Pr^{1/4}\)

\(Nu=K(\frac{z^3\rho^2\beta g \Delta Tm}{\mu^2})^{1/3}Pr^{1/3}\)

\(Nu=K(\frac{z^3\rho^2\beta g \Delta Tm}{\mu^2})^{1/3}Pr^{1/4}\)

6. Recognize the following fin.

Flat (continuous) fins

Individually finned tubes

Fully cut on axis of Helix Fins

Helical Fins

7. In the calculation of Reynold’s Number for the Friction factor of the shell, which is the correct formula for equivalent diameter De?

\(\frac{4×(D_{io}^2 - D_{oi}^2)×\frac{π}{4}}{π(D_{io}+D_{oi})}\)

\(\frac{4×(D_{oi}^2 - D_{io}^2)×\frac{π}{4}}{π(D_{io})}\)

\(\frac{4×(D_{io}^2 - D_{oi}^2)×\frac{π}{4}}{π(D_{io})}\)

Depends on the pitch

8. The fin material should be homogeneous and _________ for steady state operation.

Isentropic

Isochoric

Isobaric

Isotropic

9. Consider we have a 2-4 Shell and Tube Heat Exchanger, with the inner tube of Outer diameter 20mm (thickness 2mm) and Shell of inner diameter 100mm. We have two fluids A & B, both of density 990 Kg/m³, we desire to have their flow rates as 15 m/s(tube) and 21 m/s(shell) respectively, friction factor of 0.00096 and 2 tubes of length 0.4 m. What is the value of Pressure drop for the inner tube due to frictional losses?

20KPa

24KPa

25KPa

10.67KPa

10. Adding fins inside the tube, that is for the tube side usually ________ the heat transfer coefficient.

Increases

Does not change

Decreases

Tenfold