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Convection Experiment

Convection Experiment. Leader: Tom Salerno Partners: Greg Rothsching Stephen Johnson Jen DiRocco. What will you hear today?. Introduction Theory Equipment and Procedure Results and Discussion Conclusions Questions. Introduction. What is convection?

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Convection Experiment

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  1. Convection Experiment Leader: Tom Salerno Partners: Greg Rothsching Stephen Johnson Jen DiRocco

  2. What will you hear today? • Introduction • Theory • Equipment and Procedure • Results and Discussion • Conclusions • Questions

  3. Introduction • What is convection? • Heat transfer from fluid flowing over solid surface • Why study convection? • Occurs in almost every process plant • Example: Heat Exchangers, Tray Dryers, etc.

  4. Theory – Newton’s Law of Cooling • Flat Plate: • Finned Plate (Resistances in Parallel):

  5. Theory – Forced Convection • Physical Situation: • Solving Boundary Layer Equations • Continuity Equation - • Momentum Balance - • Thermal Balance – • Rigorous analytical solution

  6. Theory – Forced Convection • Forced Convection – analytically developed • Dimensionless Parameters • Reynolds: • Prandtl: • Nusselt: • Flat Plate:

  7. Theory - Natural Convection • Physical Situation: • New Momentum Equation: • Must now solve all three boundary layer equations simultaneously

  8. Theory - Natural Convection • Experimental Correlation: • Churchill and Chu • Dimensionless Parameters • Grashoff: • Rayleigh: • Correlation:

  9. Equipment and Procedure Figure 9: Front view of convection duct. Figure 10: Side view of convection duct.

  10. Results and Discussions • Flat Plate: Laminar Flow

  11. Results and Discussions • Turbulent Mix • New Correlation -

  12. Results and Discussions • Flat Plate: Turbulent Mix

  13. Results and Discussions • Finned Plate: Laminar

  14. Results and Discussions • Turbulent Mix • New Correlation -

  15. Results and Discussions • Finned Plate: Turbulent Mix

  16. Results and Discussions • Effectiveness of Fin Addition

  17. Conclusions – What we learned • The convective heat transfer coefficient increases linearly with the square root of air velocity • Predictive Equations are useful for predicting trend in data, but not the absolute numbers • Natural Convection is the limit to forced convection, though it is difficult to predict • The addition of fins will increase the heat transfer rate substantially at low air velocities, but not as much at higher air velocities

  18. Conclusions – Significance? • Aid in design of heat exchangers • How to increase heat transfer coefficient • How to increase heat transfer rate • Realize presence of natural convection for cheap ways to cool electronic equipment • Confidence of Predictive Equations • Use for other experiments, such as tray dryer • Only if can perfectly match geometry, or can run a short scale experiment to obtain correction factor

  19. Questions?

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