Elementary Principles 269

# Elementary Principles 269 - 7.44 (cont'd) (d) (i) The...

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7-24 7.44 (cont’d) (d) (i) The specific volume of liquid increases with the temperature, hence the same mass of liquid water will occupy more space; (ii) some liquid water vaporizes, and the lower density of vapor leads to a pressure increase; (iii) the head space is smaller as a result of the changes mentioned above. (e) – Using an automatic control system that interrupts the heating at a set value of pressure – A safety valve for pressure overload. – Never leaving a tank under pressure unattended during operations that involve temperature and pressure changes. 7.45 Basis: 1 kg wet steam (a) H O 2 1 kg 20 bars 0.97 kg H O(v) 2 0.03 kg H O(l) 2 H ± 1 (kJ/kg) H O,(v) 1 atm 2 1 kg H ± 2 (kJ/kg) H O 2 1 kg T amb , 1 atm Enthalpies: bars, sat'd kJ kg kJ kg Table B.7 ± ,. ± Hv Hl 20 2797 2 20 9086 bg = = U V | W | ΔΔ Δ EEQ W pK HH H HT ,, , ±± .. . . ± = Energy balance on condenser: = 2740 kJ / kg C Table B.7 o 3 0 0 0 97 2797 2 003 908 6 132 21 2 =⇒ = = + ⇒≈ bgb g (b) As the steam (which is transparent) moves away from the trap, it cools.
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## This note was uploaded on 02/27/2012 for the course CHEMICAL E 312 taught by Professor Cheung during the Fall '11 term at The University of Akron.

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