Heat Transfer Examples

Calculate the entropy change for reversible heat transfer (Example 7.1). 

The principle of designing for small gradients is not limited to heat transfer examples. It applies to other thermodynamic gradients as well. For example, sparged reactors with fast reactions benefit from small gas bubbles with a large surface area to promote mass transfer. Under those circumstances minor variations in the partial pressure of reactants give a rapid response in overall reaction rates. 

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The hg involves convection and gas radiation to or from a surface, and it is like two resistances in parallel, thus hg = he + hr. Similar to Ohm s Law, (/ = E/Rt), heat flux, q = Q/A = ATfR, or g — UAAT, which is the basic equation of heat transfer. Example 5.1 illustrates the method for calculating U, the overall coefficient of heat transfer. 

Before considering the solution of convection heat transfer examples, we will review the steps followed in such cases. While the discussion applies to heat transfer coefficients based on average temperature, it can also be applied to other heat transfer coefficients. 

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