By Robert L. Young Associate Dean and Professor of Aerospace and Mechanical Engineering Emeritus University of Tennessee. Retired in 1990 From The University of Tennessee Space Institue. Fellow of AIAA, ASME, ABET, AEDC First Published in the Year 2000 INTRODUCTION For more than 40 years, I taught undergraduate and graduate level courses in Engineering Thermodynamics at Northwestern University and The University of Tennessee Space Institute. In teaching at the undergraduate level, I was always concerned that many students who had done well in calculus, statics, dynamics and differential equations seemed to have great difficulty in mastering the concepts and the utilizaion of Engineering Thermodynamics. At the graduate level, I found that the students knew something about the energy property enthalpy, analyzed most thermodynamic systems as steady flow processes and if at all possible avoided the property entropy. A PROBLEM PRODUCING DISCOURAGEMENT In my beginning graduate classes, early in the semester, I frequently gave the following problem to the students: For a closed, rigid container of gas, obtain an experssion for the amount of heat, Q, which must be added to increase the gas temperure (T) and pressure (p) from a temperature of T1, pressure p1 to a higher temperature T2, pressure p2. Properties of the gas at state 1 are given as enthalpy (H1), temperature (T1), pressure (p1) and volume (V1) and properties of the gas at state 2 are are given as H2, T2, p2 and V2) Because their undergraduatge engineering thermodynamics courses and succeeding application courses had placed so much emphasis on steady flow processes, Many of the students would apply the steady flow energy equation: Q  W = H2  H1. Recognizinng that work W was zero (rigid container) their final answer would be: Q = H2  H1. Only a few would recognize that the system given was a closed (constant mass) system and the correct energy equation is: Q  W = U2  U1 where U is the internal energy given by H  PV and for this case: Q = H2  p2V2  (H1  piV1) Powered by MSN T 






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