Q1. Why is Hagen Poiseuille equation used?
▶️ To calculate head loss due to friction in pipe for a fully developed laminar flow
Q2. Hagen Poiseuille equation. Effect on pressure gradient if diameter is doubled
▶️ It is reduced by four times
Q3. The same in turbulent flow
▶️ We assume laminar flow for Hagen Poiseuille equation so it can’t be determined from this equation. For this we have to consider Darcy–Weisbach equation (doubt)
Q4. Modes of heat transfer
▶️ There are 3 modes of heat transfer Conduction, Convection and Radiation
Q5. Which mode is most used
▶️ Conduction is widely used in industries
Q6. Write Dittus Boelter equation
▶️ Nu=0.023Re^0.8Pr^n
For cold fluids n=0.3
For hot fluids n=0.4
Q7. Biot’s Number
▶️ The Biot number is the ratio of the internal resistance of a body to heat conduction to its external resistance to heat convection.
Q8. In shell side fluid thermal conductivity is increased, it’s effect on heat transfer coefficient, show mathematically
▶️ By Nusselt no=hd/k. Heat transfer coefficient also increases
Q9. What is effectiveness of heat exchanger
▶️ Effectiveness is defined as the ratio of actual heat transfer to the maximum possible heat transfer.
Q10. What is max heat transfer in heat exchanger
▶️ Qmax=Cmin(th1-tc1)
Cmin is the minimum thermal capacity of the two fluids
Th1-tc1 is the temperature difference of entry of fluids
Q11. Why Max diff between the temp of fluid is used for max heat transfer
▶️ Qmax is directly proportional to ∆T. We need maximum difference in temperature