MEC E230 Lecture 2: September 9, Conservation and Control Volumes
3 Oct 2016
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Document Summary
To convert physical to mathematical models, we employ control volumes to apply mass and energy conservation. Mass cannot be created or destroyed (unless nuclear reactions are involved), but it can be transported. Energy cannot be created or destroyed (cid:523)unless unclear(cid:524), it can only be converted between formed (eg. mechanical work -> heat) and transported. Energy is loosely defined, we can always make up a new type of energy but it is always conserved. Energy can be transported with mass (container, liquid), or without mass. Note: work is associated with movement but can occur without bulk displacement of mass, example: Cv defines the region of space that captures whatever process you are interested in understanding and leaves out the rest of the universe. Although the boundaries of the cv often coincide with physical boundaries (eg. engine, building envelope), it does not necessarily have to be the case.
