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Unformatted text preview: Lecture 20 Sensible and latent heat Addition and removal of heat is a very important process in chemical engineering. For example: Chemical reaction rates typically depend exponentially on temperature, so yield depends on heating/cooling; Reactions are often exothermic, so to prevent dangerous runaway conditions, heat must be removed; Chemical separations usually depend on inducing a phase change in one component relative to another (i.e., distillation). Heat sources and sinks can include Chemical reactions; Heat added or removed via conduction; Heat absorbed or liberated in phase transitions; Heat absorbed or liberated in mixing liquids. Specific heat functions. Specific heats in general depend on pressure (or equivalently molar volume) as well as temperature, but in two limiting cases (ideal gases and incompressible liquids) they do not depend much on pressure for incompressible liquids, because pressure does not change the state of the liquid very much, and for ideal gases, because the internal energy only depends on temperature. Specific heats are often given as some polynomial in temperature; Appendix C gives coe ffi cients for a variety of gases....
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