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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

Convection Experiment

Leader: Tom Salerno

Partners:

Greg Rothsching

Stephen Johnson

Jen DiRocco


What will you hear today
What will you hear today?

  • Introduction

  • Theory

  • Equipment and Procedure

  • Results and Discussion

  • Conclusions

  • Questions


Introduction
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.


Theory newton s law of cooling
Theory – Newton’s Law of Cooling

  • Flat Plate:

  • Finned Plate (Resistances in Parallel):


Theory forced convection
Theory – Forced Convection

  • Physical Situation:

  • Solving Boundary Layer Equations

    • Continuity Equation -

    • Momentum Balance -

    • Thermal Balance –

    • Rigorous analytical solution


Theory forced convection1
Theory – Forced Convection

  • Forced Convection – analytically developed

    • Dimensionless Parameters

      • Reynolds:

      • Prandtl:

      • Nusselt:

    • Flat Plate:


Theory natural convection
Theory - Natural Convection

  • Physical Situation:

    • New Momentum Equation:

      • Must now solve all three boundary layer equations simultaneously


Theory natural convection1
Theory - Natural Convection

  • Experimental Correlation:

    • Churchill and Chu

    • Dimensionless Parameters

      • Grashoff:

      • Rayleigh:

    • Correlation:


Equipment and procedure
Equipment and Procedure

Figure 9: Front view of convection duct.

Figure 10: Side view of convection duct.


Results and discussions
Results and Discussions

  • Flat Plate: Laminar Flow


Results and discussions1
Results and Discussions

  • Turbulent Mix

    • New Correlation -


Results and discussions2
Results and Discussions

  • Flat Plate: Turbulent Mix


Results and discussions3
Results and Discussions

  • Finned Plate: Laminar


Results and discussions4
Results and Discussions

  • Turbulent Mix

    • New Correlation -


Results and discussions5
Results and Discussions

  • Finned Plate: Turbulent Mix


Results and discussions6
Results and Discussions

  • Effectiveness of Fin Addition


Conclusions what we learned
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


Conclusions significance
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



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