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__Fin Heat Transfer; Fins Part III__

**Reading:** Before you begin this part, read an introductory chapter on natural convection (may be called "free convection") in an undergraduate heat transfer text.

**Objective:**

The objective of Part III of the fin lab is to examine the nature of natural convection heat transfer from fin arrays and to compare it to low-velocity forced convection.

When a heated fin array is placed in a stagnant fluid, the density gradient created by the presence of the hot fin surface gives rise to bouyancy driven flow opposite to the gravitational acceleration vector. Convection by this self-induced flow is the principal means by which the fin is cooled. Since the convective heat transfer is not dictated by an imposed external freestream velocity, we are unable to express the heat transfer rate conveniently in terms of the Reynolds number. The equations of the motion for bouyant flow indicate that the appropriate scaling parameter involves the Grashof number.

**Procedure**

Find the steady-state temperature distribution of the mean fin array in a low velocity forced convection environment. Use a velocity of 5 m/s or less with a power input of 50 Watts.

Next, remove the fin array from the wind tunnel and place it in a natural convection environment using the wooden heater holder. You will take one steady-state temperature distribution for natural convection with a shroud and one without a shroud.

All data are collected using 50 Watts of power input.