4 wcomp in krt1 k1 p2 p1 k 1k 1 140287 kjkg

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Unformatted text preview: T1 = 300 K υ relative to its critical-point values. 3 Kinetic and potential energy changes are negligible. Analysis The steady-flow compression work for all these four cases is determined by using the relations developed earlier in this section: (a) Isentropic compression with k 1.4: wcomp, in kRT1 k1 P2 P1 (k 1)/k 1 (1.4)(0.287 kJ/kg · K)(300 K) 1.4 1 900 kPa 100 kPa (1.4 1)/1.4 1 263.2 kJ/kg (b) Polytropic compression with n wcomp, in nRT1 n1 P2 P1 1.3: (n 1)/n 1 (1.3)(0.287 kJ/kg · K)(300 K) 1.3 1 900 kPa 100 kPa (1.3 1)/1.3 1 246.4 kJ/kg (c) Isothermal compression: wcomp, in P2 900 kPa (0.287 kJ/kg · K)(300 K) ln P1 100 kPa 189.2 kJ/kg RT ln (d ) Ideal two-stage compression with intercooling (n 1.3): In this case, the pressure ratio across each stage is the same, and its value is Px (P1P2)1/2 [(100 kPa)(900 kPa)]1/2 300 kPa The compressor work across each stage is also the same. Thus the total compressor work is twice the compression work for a single stage: FIGURE 7–47 Schematic and P-υ diagram for Example 7–13. cen54261_ch07.qxd 11/18/03 9:57 AM Page 312 312 FUNDAMENTALS OF THERMAL-FLUID SCIENCES wcomp, in 2wco...
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