Chemical Engineering #Interview Questions: #HeatExchanger
If you’re preparing for an interview or aiming to pass F.E. or P.E. Exams upon your heat exchanger design knowledge, here’s a quick Q&A guide with 10 rules for designing efficient and reliable shell and tube heat exchangers:
Q1. Where should the higher_pressure fluid be placed?
A: On the tube side. Tubes are easier to reinforce against higher pressures compared to the shell.
Q2. What about a fluid prone to fouling?
A: The fouling-prone fluid should also be placed on the tube side, as tubes are easier to clean using mechanical or chemical methods.
Q3. Which fluid should go on the shell side when considering viscosity?
A: Fluids with higher viscosity are typically placed on the shell side to improve flow distribution and heat transfer.
Q4. How should flow rates influence fluid placement?
A: The fluid with a lower flow rate is usually placed on the shell side to minimize pressure drop and improve heat transfer efficiency.
Q5. How do you select tube materials?
A: Tube material selection depends on factors like corrosion resistance, temperature limits, and cost. Common options include carbon steel, stainless steel, and copper.
Q6. What is the relationship between tube diameter, length, and efficiency?
A: Smaller diameters provide better heat transfer coefficients but increase pressure drop. Tube length should be optimized for heat transfer area without excessive pressure drop.
Q7. How does baffle spacing impact performance?
A: Closer baffle spacing increases shell-side velocity and heat transfer, but it also increases pressure drop. Choose a balance based on process needs.
Q8. What tube pitch is most common?
A: A triangular pitch is often preferred over a square pitch for better flow distribution and heat transfer efficiency.
Q9. How do the number of tube passes affect performance?
A: More tube passes increase heat transfer but also add to pressure drop. Balance the design for optimal performance.
Q10. Why is Log Mean Temperature Difference (LMTD) important?
A: LMTD represents the average temperature difference between the two fluids, a critical parameter for determining heat exchanger performance. For non-ideal flow conditions, apply a correction factor.
Reference Wikipedia: https://en.m.wikipedia.org/wiki/Heat_exchanger
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