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Unformatted text preview: 9/8/2010 1 Transient Conduction: The Lumped Capacitance Method The Lumped Capacitance Method Chapter Five Sections 5.2 thru 5.3 Class 7 What kind of situation is transient conduction? A solid experiences a sudden change in its thermal environment Quenching Charging Charging Lumped capacitance Assume temperature is spatially uniform at any instant during the transient process Therefore we assume no temperature gradients For this situation, what is the energy balance? g out in st st E E E t dE E & & & & + = I II III IV a) I and II b) I and III c) I, II and III d) I and IV e) II, III and IV How do we use the energy balance to find our lumped capacitance approach? 9/8/2010 2 Define a thermal time constant: Define a thermal time constant: What will happen if we increase R t ? a) A solid will respond more slowly to changes in its thermal environment b) A solid will respond more quickly to changes in its thermal environment c) The R t does not affect the response only the lumped thermal...
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