Elementary Principles 186 - 6.31 (cont'd) When Tf...

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6- 20 6.31 (cont’d) c. d. When T f decreases, P f decreases. Decreasing temperature and increasing pressure both to increase the fractional condensation. When you decrease T f , less compression is required to achieve a specified fractional condensation. A lower T f requires more refrigeration and therefore a greater refrigeration cost ( C refr ). However, since less compression is required at the lower temperature, C comp is lower at the lower temperature. Similarly, running at a higher T f lowers the refrigeration cost but raises the compression cost. The sum of the two costs is a minimum at an intermediate temperature. 6.32 a. Basis : 120m min feed @ 1000 C(1273K), 35 atm 3o . Use Kay’s rule. Cmpd. atm Apply Newton's corrections for H H CO 133.0 34.5 CO CH 2 2 2 4 TK P T P cc c corr c corr bg b gb g b g b g . .. . . 332 12 8 413 208 304 2 72 9 190 7 458 −− == + + + = Ty T K ci c i 040 413 0351330 020 3042
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