This online-only sidebar to "Convection Dryers: The Path to Energy Savings" illustrates how to maximize energy savings by reducing losses. The web-exclusive content illustrates visually each of the areas outlined in the article.

Whether your system utilizes a conveyor bed, rotary, fluid bed, or other type of drying technology, the techniques to reduce energy usage are similar. To identify the potential for energy reduction in a dryer, you must first understand its balance of energy. From the control volume as seen in the figure at right, energy is spent in the following locations:



Heating and evaporating water


Heating fresh (makeup) airstreams





Losses through radiation, conduction, leaks and/or component absorption





Applying heat to the product




By examining each of these components individually, it becomes clear where the energy savings opportunities lie.

In the figure, note the following:


is the enthalpy of the dry product and desired remaining water entering the dryer






is the enthalpy of the dry product and the desired remaining water exiting the dryer






is the enthalpy of the water entering with the product that will be evaporated






is the enthalpy of the evaporated water exiting the dryer






is the enthalpy of the makeup air entering the dryer






is the enthalpy of the spent makeup air exiting the dryer






is the energy from the heat source





is the energy lost by conduction, radiation, component heating and leaks

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